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Plesiosaur Peril — the lifestyles and behaviours of ancient marine reptiles

The views expressed are those of the author and are not necessarily those of Scientific American.


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Cryptoclidid plesiosaurs, ophthalmosaurid ichthyosaurs, a hybodontid shark and... ray-finned fish, ammonites and a sea jelly share a Middle Jurassic marine scene in this wonderful illustration from Daniel Loxton's new book Plesiosaur Peril. Image used with permission.

Between the later part of the Triassic and the very end of the Cretaceous, the seas of the world (and some of its rivers, lakes and estuaries as well) were inhabited by the remarkable group of swimming reptiles known as the plesiosaurs. All plesiosaurs – so far as we know – were predators, the shapes of their teeth and jaws indicating that they preyed variously on swimming and benthic invertebrates, on fish, and also on other aquatic reptiles. Some were macropredators that attacked and ate other plesiosaurs as well as ichthyosaurs, swimming crocodyliforms and turtles. Members of several lineages famously possessed long or ridiculously long necks, the flexibility and function of which have long been the subject of debate. Others (referred to as pliosaurs) had long, superficially crocodile-like skulls, and usually combined these with relatively short necks.

Thick-boned, robust ribs and gastralia (here in the Jurassic pliosaur Pachycostasaurus dawni) were probably used as 'bone ballast' in these animals. Image by Darren Naish.

In overall body form, all plesiosaurs were generally alike. Their skeletons possess large, plate-like limb girdles mostly positioned on the ventral surface of the body, and there are two pairs of slender, wing-like paddles and a relatively short tail. An interlocking basket of heavy-boned belly ribs (or gastralia) fill in the space between the pectoral and pelvic girdles and presumably helped keep the body stiff during life. There’s no question that plesiosaurs were limb-propelled swimmers. The question is: what sort of limb-propelled swimming did they use? Were they ‘rowers’, ‘fliers’, some combination of the two, and did they use their forelimbs and hindlimbs synchronously, asynchronously, or what? These issues have been much discussed in the literature (Robinson 1975, Tarsitano & Riess 1982, Halstead 1989, Riess & Frey 1991, O’Keefe 2001a, Carpenter et al. 2010) and are the subject of current investigation.

Key features of the plesiosaur skeleton, labelled on a reconstruction of the Early Jurassic taxon Rhomaleosaurus. Image by Adam S. Smith.

Schematic depiction of Benson & Druckenmiller's (2014) phylogenetic hypothesis for Plesiosauria: the black horizontal line depicts the Jurassic-Cretaceous Boundary. Brachauchenine pliosaurids and cryptoclidids crossed it, but all other Cretaceous taxa belong to the newly recognised clade Xenopsaria.

When it comes to what we really know about plesiosaurs, the literature includes a fair bit about the possible biomechanics of swimming, but is generally focused on anatomy, systematics and phylogeny. Understanding plesiosaur evolution is difficult since substantial convergence and re-evolution of similar body plans and skull shapes seems to have been a pervasive theme; the idea that very long necks and fairly short necks re-evolved independently on some or several occasions has long been popular (Bakker 1993, Carpenter 1997, O’Keefe 2001b, 2002, Ketchum & Benson 2010, Benson et al. 2013), meaning that the conventional versions of the elasmosaur and pliosaur groups are not monophyletic. The most recent work indicates that virtually all Jurassic lineages became extinct round about the Jurassic-Cretaceous Boundary, with a single surviving lineage – the Xenopsaria – then undergoing a major burst of radiation during the Cretaceous, giving rise to new versions of Jurassic-style body plans (Benson & Druckenmiller 2014).

Mother and unborn baby Polycotylus to scale: the baby is HUGE. Image from O'Keefe & Chiappe (2011).

What about the biology, behaviour and lifestyles of these amazing animals? Invaluable studies of jaw biomechanics, tooth form and stomach contents give us insights into what and how plesiosaurs ate, and on how they collected and processed their food (Massare 1987, Taylor 1987, 1992), and some extremely interesting ideas on breathing and olfactory behaviour have been proposed (Cruickshank et al. 1991, Buchy et al. 2006). Trough-like feeding traces preserved on an ancient sea floor provide possible data on plesiosaur foraging behaviour (Geister 1998), and the amazing discovery of a proportionally enormous baby preserved within the body of its mother has given us substantial food for thought as goes the reproductive biology and social lives of these animals (O’Keefe & Chiappe 2011) [see the links below for more on those discoveries and what they might mean].

In general, however, we of course know very little about plesiosaur biology and behaviour, and I’d say that most questions we might ask can only be informed by inference: by extrapolating or guessing based on what we see in living reptiles and other animals. Remember that, when it comes to interesting questions about the behaviour of long-extinct animals (especially weird ones without precise modern analogues), we’re always constrained by a frustrating lack of information.

Front cover of Daniel Loxton's Plesiosaur Peril. Buy it now!

Nevertheless, a long interest in both plesiosaurs and the amazing behaviour of extant marine tetrapods means that I’ve long had thoughts about diving behaviour, feeding ecology, social behaviour, intentional beaching and so on in plesiosaurs – I even have a half-finished manuscript done on this subject. So it was fitting that, back in October 2012, Daniel Loxton contacted me to ask if I’d like to be the technical consultant on his new book, Plesiosaur Peril. As with his previous works in the same series – Ankylosaur Attack (Loxton 2011) and Pterosaur Trouble (Loxton 2013) – Plesiosaur Peril is a fantastically illustrated children’s book that uses the fictional story of an individual animal to paint a picture of the lifestyles of ancient animals, using scientific data where possible.

The news is that Plesiosaur Peril is now out, so go buy it! In the text you’re about to read below, Daniel has kindly let me use several of the amazing, computer-generated illustrations that he, together with Jim W. W. Smith, created for Plesiosaur Peril. I’m sure you’ll agree that they look great. What I’ve also done is feature the exchange of questions and answers that Daniel and I engaged in while he was preparing the book’s text. Hopefully you’ll find this interesting; I also hope that it’ll provide some interesting insight and background into the book’s contents, as well as illustrate what we do know versus what we don’t when it comes to plesiosaur behaviour and biology.

Reconstructing live plesiosaurs – a tricky task

Images like this (by Bernard Long, from 1983) look great, but probably don't depict an anatomically feasible or plausible posture.

Before we get into that, I’d like to make a few comments about plesiosaur life appearance. While the two creatures that feature in the book – the Middle Jurassic, western European taxa Cryptoclidus and Liopleurodon – are among the best known of plesiosaurs, we have a huge number of questions about even their very appearance. It’s well known these days that plesiosaurs were almost certainly not capable of the erect-necked or swan-necked poses shown in older artwork: the anatomy is against it, it doesn’t work when we consider their buoyancy and pose in the water, and it’s not consistent with what we understand of their ecology and behaviour anyway. While they should therefore be reconstructed with more horizontal neck poses, it doesn’t follow, however, that they were wholly incapable of maintaining a vertical neck posture for a brief period – read on…

Possible ranges of vertical motion present in the necks of Cryptoclidus and Muraenosaurus: the caveat being that cartilage and other soft tissues may have allowed more flexibility than we can predict based on osteology alone OR may have reduced the amount of flexibility shown here. Images by Mark Evans, used with permission.

Plesiosaur skin texture is still very much an unknown. Plesiosaur expert Arthur Cruickshank once told me that skin impressions associated with the New Zealand plesiosaur Kaiwhekea katiki (one of the controversial aristonectine elasmosaurids, once thought to be late-surviving cryptoclidids) revealed a smooth surface, studded regularly with low, rounded scutes or scales, though so far as I know this has never been confirmed or published.

You'd be hard pressed to examine the skin impressions of Attenborosaurus today... only casts remain (like this one at London's NHM). Image by Ghedoghedo, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

However, if this one plesiosaur really was like this, it doesn’t mean that they all were (nor would that peculiar skin texture necessarily apply to the whole body). So – were plesiosaurs scaly or smooth-skinned? And if they were scaly, did they have overlapping scales, non-overlapping scales, smooth scales, or ornamented scales? Impressions of a smooth skin have been reported for the Jurassic plesiosaur Attenborosaurus, but the original specimen was destroyed during WWII and no further information is available. [Adjacent image by Ghedoghedo.]

Those of you familiar with the plesiosaur literature will know that there has recently been a resurgence of interest in the actually rather old idea that at least some plesiosaurs possessed a vertical fin on the tail. Smith (2013) showed how the proportions and form of the tail vertebrae in the pliosaur Rhomaleosaurus are suggestive of a tail fin of some sort. Wilhelm (2010) also explored this subject in an unpublished thesis, concluding that members of the Cryptoclidus group likely had a tail fin too, perhaps used as a rudder. Daniel and I discussed the possibility of putting tail fins on the plesiosaurs of Plesiosaur Peril, but ultimately the information came in too late for us to be confident about including it – the Liopleurodon’s tail, at least, does have a small fin, though, as a nod to this possibility.

Plesiosaur forelimbs, as illustrated by Bakker (1993). It is assumed here that the soft tissues adhered closely to the forelimb's bony outline. In fact, skin and other tissues might have formed more extensive tips and trailing edges: the jury is still out on this issue.

While I’m here, it’s worth saying that there are a few other bits of plesiosaur life appearance that we might be getting wrong. The general thinking at the moment is that the paddles of live plesiosaurs essentially matched the outlines of the bones. However, one (still, maddeningly, unpublished) plesiosaur fossil from England seems to preserve the impressions of flexible, curved tips to its flippers that aren’t reflected in the underlying osteology. [Image below by Matěj Baťha.]

'Unsheathed', protruding teeth do occur in living reptiles (like this gharial) - so was this the case for plesiosaurs as well? Image by Matěj Baťha, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Also, what gives with the teeth and jaw edges of these animals? As you can see from all the reconstructions shown here, tradition has it that plesiosaur teeth protrude obviously from the jaw edges, unsheathed by lips and with the skin around the teeth adhering tightly to the skull bones. The whole configuration I’ve just described is not implausible, since it’s essentially the condition present in crocodylians (and crocodylians, being mostly aquatic, may well be reasonable models for plesiosaurs in some respects). But, given the fact that ‘lips’ (of a sort) cover the teeth in snakes and lizards – even aquatic ones like sea snakes – we’re left wondering whether plesiosaurs really looked like this. Could ‘lips’ (that is, sheets or bands of skin, not necessarily lips in the flexible, sensitive sense) have covered these crazy teeth? Then again, living snakes and lizards don’t have teeth that protrude or interlock in the same fashion as plesiosaur teeth. For now, we don’t know either way: I’m inclined to think that their teeth really did protrude as we usually show, and that soft tissue did not obscure or cover them. But it’s something to be curious about; something that will only be informed by the discovery of exceptional specimens.

My attempt to restore the head (and part of the neck) of Cryptoclidus eurymerus. Would the teeth really have been this prominent and projecting in the live animal? It's difficult to imagine how they could have been sheathed by soft tissue. Image by Darren Naish.

Ok, on to the Q&A. This reflects part of the back-and-forth that went on between Daniel and myself as he did his research for the book. The first part of the discussion focuses on the long-necked Cryptoclidus, a slender-toothed cryptoclidid known from Middle Jurassic strata in England, France and perhaps Russia and elsewhere. There is some confusion about the total length of Cryptoclidus. All of the good specimens indicate total lengths of 3-4 m but several authors have said that these are juveniles or subadults, and that the true adult length was more like 6-8 m. Anyway, after looking at the possible behaviour and lifestyle of Cryptoclidus, we move on in the second part of the discussion to discuss the large, robust-skulled pliosaurid Liopleurodon.

Elasmosaurids thrusting their necks vertically in a (hypothetical) lekking display: image by John Conway, from All Yesterdays.

Q: Would Cryptoclidus have engaged in spyhopping behaviour?

A: I wonder how interested plesiosaurs would have been in seeing things in air. But, then, you can say the same thing about cetaceans (note also that the apparently flattened eyeballs of plesiosaurs mean that their eyesight in air was perhaps not great). As is now reasonably well known, raising the whole neck upwards from the horizontal may not have been possible at all, but, yes, vertical spyhopping remains plausible. Maybe plesiosaurs occasionally wanted to check for flocks of foraging pterosaurs, the vicinity of land and so on.

Q: Did Cryptoclidus eat stones?

A: Yes, we know that plesiosaurs did this, and in fact you might imagine that they went to special places to collect the right sorts of stones (after all, in some marine environments, stones and pebbles are rare). Imagine the possibility of plesiosaurs making treks to special pebbly beaches (and hence into very shallow water) to find and swallow stones. Of incidental interest is that stones can also be carried in the roots (and attached sediment) of floating trees.

In this illustration, the juvenile Cryptoclidus looks on while its mother forages for, and swallows, stones. Image from Daniel Loxton's Plesiosaur Peril, used with permission.

Q: Any possibility that Cryptoclidus might have dug or foraged for prey like clams or crabs?

A: The slim teeth of Cryptoclidus suggest that this animal wasn’t habitually able to eat or subdue anything tough-shelled or chunky, so shrimps and thin-shelled bivalves are probably at the extreme end of what it was capable of subduing. However, grubbing around in the sediment and reaching into burrows are totally plausible. In fact, there is some evidence suggesting that long-necked plesiosaurs were mostly may sometimes have behaved as ‘benthic grazers’, reaching down to pick at prey from the seafloor (McHenry et al. 2005).

Speculative scene showing Cryptoclidus group feeding together on a baitball. This might have happened. It might not. Image by Darren Naish.

Q: Was Cryptoclidus social? Would it have travelled in groups?

A: Given how widespread social interactions are in reptiles of all sorts, I’m inclined to think that anything goes, more or less. Some lizards, crocodylians and turtles really are social, hanging out in groups or pairs deliberately (examples: spiny-tailed goannas, gopher tortoises), others have long-term monogamy and pair-bonding (examples: American alligators, Shingleback skinks). Some data indicates that plesiosaurs had complex social lives, and I certainly consider it plausible that extended social bonds were present in these animals. Read on.

Q: Any indication of pack-hunting behaviour in plesiosaurs?

A: If these animals moved in groups – or found themselves in groups fortuitously or incidentally – then co-operative hunting of a sort is plausible, since even animals that don’t live together will co-operate to herd or cluster prey. I’m not sure I’d want to call this pack-hunting, but social hunting of a sort seems plausible and perhaps likely. Imagine benthic-foraging plesiosaurs flushing prey towards others, or a group of them hemming prey in, and moving together so that the prey gets bunched up. There’s no direct fossil evidence for this, but the fact that some living crocodylians practise co-operation (Gans 1989, Yamashita 1991, King et al. 1998) provides an analogy.

The storyline of Plesiosaur Peril is mostly based around the association between a juvenile Cryptoclidus and her mother. Based on what we know, there are good reasons for thinking that parental care of some sort really did occur. In this image, the mother and juvenile surface for breath. Image from Plesiosaur Peril by Daniel Loxton, used with permission.

Q: Do you think juvenile plesiosaurs stayed with their parents? Could these animals have lived in family groups, or pods?

A: The pregnant polycotylid described by O’Keefe & Chiappe (2011) shows that baby plesiosaurs were enormous relative to their mothers (as in, more than 33% the mother’s length). Enormous babies indicate substantial maternal investment, and – in living reptiles – are suggestive of parental care, and also such things as kin recognition and strong social bonds. The giant polycotylid baby actually suggests that plesiosaurs practised extended parental care, with babies staying with their mothers for a long time: as in, months to years. I emphasise that this is speculative, and that what went for polycotylids might not have worked for Cryptoclidus too.

A hunting Cryptoclidus group pursue belemnites. Image from Plesiosaur Peril by Daniel Loxton, used with permission.

Q: Assuming that parental care was at play, would an adult have defended a juvenile from predators? If so, how?

A: If there’s a strong bond between a mother and her baby, then, yes, I should imagine that the mother would defend her baby from attackers. Firstly, the juvenile might well travel close to the mother’s body so as to be concealed from predators (as occurs in whales). Sharks and mid-sized pliosaurs that came to attack the baby could well have received nasty flipper-smacks from the mother. When it comes to the danger posed by giant pliosaur predators, however, I suppose fast retreat would be the only way of escaping. If that’s so, we have to wonder whether babies could swim as fast as adults.

Did pliosaurs intentionally beach to grab prey animals from near the water's edge? It's been suggested, but we'll likely never know for sure. Image by Darren Naish.

Q: What do you think about the possibility that these animals might have intentionally beached for safety or escape, like walruses or seals or penguins?

A: I’m inclined to think that adult Cryptoclidus were too large to be able to fully leave the water. In fact, I reckon that plesiosaurs as a whole lack features that might permit terrestrial locomotion. If there are social bonds between juveniles and adults, you wouldn’t expect a juvenile to self-beach while its mother stayed in the water. Like most people who have expressed an interest in this area, I consider it possible, however, that plesiosaurs could self-beach in the way that some killer whales, bottlenose dolphins and wels catfish do: in other words, perhaps some pliosaurs might have self-beached in order to grab prey from the water’s edge. But there’s nothing about Cryptoclidus here that makes it different from a pliosaur:  if a Cryptoclidus could self-beach to escape a pliosaur, I would think that the pliosaur could self-beach in the same way.

Q: Do you think Cryptoclidus might have eaten ammonites?

A: I don’t think Cryptoclidus has the right sort of teeth or jaws to do much damage to an ammonite, but I suppose it could grab at the tentacles and maybe attack the soft parts in general if they were protruding. Of course, that all depends on what ammonites looked like when alive (there being a few competing ideas).

A juvenile Cryptoclidus swims alongside ammonites, the super-abundant shelled cephalopods of the Mesozoic seas. Image from Plesiosaur Peril by Daniel Loxton, used with permission.

We now move to consideration of that famous giant pliosaur, arch-predator Liopleurodon. Reaching 6 m and perhaps twice this, Liopleurodon has a giant, long-snouted skull lined with deeply rooted, conical teeth. It was undoubtedly a powerful predator of other vertebrates, presumably grabbing and dismembering other plesiosaurs as well as ichthyosaurs, crocodyliforms and fish. Indeed, preserved bite marks showing that it sometimes attacked, and presumably fed on, its long-necked relative Cryptoclidus. Understandably, Daniel wanted Liopleurodon as the villain of the piece: the lurking predator that presents the main danger to our cryptoclidid heroes.

Famous mounted skeleton of Liopleurodon, on dispay at Museum of Paleontology, Tuebingen. Image by Markus Bühler.

Q: Is it plausible that these animals were aggressive to rival individuals?

A: Yes, totally. I like to imagine these animals as combining various behavioural traits of cetaceans, crocs and lizards. As discussed above, plesiosaurs might have had social bonds with ‘friends’ and relatives, but they might been aggressive too, and maybe with some species mostly behaving aggressively towards conspecifics (as per Saltwater crocodiles). There are a few big pliosaur specimens where snout tips and flippers seem to have been bitten by other, similarly-sized pliosaurs, so we may even have direct evidence for this sort of behaviour.

Trace fossils might show that plesiosaurs like Liopleurodon ploughed through sea-floor sediment in search of food, though there are reasons for being sceptical of this idea. Image by Darren Naish.

Q: Would pliosaurs like Liopleurodon ever had rested on the sea floor?

A: Not sure about this, since I’m not sure they could hold their breath for hours. I know that some turtles sleep on the seafloor, but my suspicion is that they have much lower oxygen demands than plesiosaurs. I can buy brief settling or foraging on the seafloor, but no extended time spent there. Mind you, trace fossils suggest that these animals ploughed through sediment when foraging, and perhaps also rubbed their bodies against stones or patches of sand for grooming purposes (Geister 1998).

Q: Do you think that pliosaurs were ambush predators?

A: I feel it’s plausible that these giant predators did the same thing that white sharks do: that they lurked in dark water, then rushed upwards towards prey silhouetted at the surface. This is a sort of ambush hunting I suppose. A prey species is therefore vulnerable when at the surface and might try to spend as little time there when in an environment where pliosaurs are present (in the modern world, elephant seals spend as little time at the surface as possible when white sharks are around).

Liopleurodon pursues Cryptoclidus: image from Plesiosaur Peril; by Daniel Loxton and used with permission.

It’s plausible that they also used obstacles, debris, plant growth and maybe even sediment clouds in the water to conceal themselves before bursting from cover and pursuing prey. I wonder if reefs (sponge reefs were apparently a big thing in the Jurassic) were ever big enough to provide cover for a pliosaur. There’s some controversy over how old kelp and similar algae are, but if they were present in the Jurassic we might perhaps imagine a pliosaur hiding in a kelp forest… imagine the unlucky prey animal that swims into such a lurking giant. Could pliosaurs have used suspended sediment (and thus reduced visibility) to conceal themselves, perhaps then relying on their sense of smell to locate prey? If so, hunting in the mouth of an estuary might have been a viable strategy that these animals could have exploited. I can’t think of any living animals that deliberately stir up sediment to conceal themselves, but there are whales (Kogia) that produce a cloud of reddish fluid (probably faeces) and then hide inside the cloud. They use this as more of a predator-avoidance strategy than a hunting one, however.

Q: Did pliosaurs use pursuit predation as a prey-catching strategy?

A: My best guess (largely concordant with what other plesiosaur researchers think is likely) is that they remained concealed as best as possible before dashing out (or up) at speed. In other words, there would be a chase, but not necessarily a long one. A prey animal would have to react very quickly – that is, have very good acceleration – to get away, and it may be that pliosaurs were better at accelerating than some of the prey animals they went for. Liopleurodon, for example, has especially big hindflippers (bigger than the foreflippers), so maybe it was a better accelerator than Cryptoclidus.

A passing Cryptoclidus group keeps an eye on a nearby Liopleurodon. Image from Plesiosaur Peril by Daniel Loxton, used with permission.

Q: Is there any evidence for pack hunting in pliosaurs?

A: As per the above comments on Cryptoclidus, social bonds of some sort – involving parental or mating relationships – are now plausible for these animals, so we might imagine twos or threes working together. In lizards and crocs, juveniles and parents recognise each other (that is, exhibit kin recognition) long after their original parental care phase has passed. I’m speculating here but, theoretically, a big juvenile pliosaur of several years old could conceivably meet up with its mother.. and, if she has a new juvenile, we can get a group of 3 animals (or more). A recent study of dwarf caimans described exactly this: a mother was discovered with both brand-new hatchlings as well as juveniles of over 1 yr old, obviously from a previous brood (Campos et al. 2012). Anyway, I think it’s plausible to think of related individuals co-operating.

Humpback whale breaching. Did plesiosaurs do this sort of thing too? Image by Gillfto, licensed under Creative Commons Attribution-Share Alike 3.0 Unported license.

Q: Could pliosaurs have indulged in breaching behaviour?

A: Crocs do head slaps, white sharks smack their tails on the water surface, and whales breach [adjacent image by Gillfoto]. Based on this data, I think we can regard it as likely that plesiosaurs also used noisy displays at the water surface to communicate signals over distance (this, of course, then raises questions about hearing abilities and so on). These might have been aggressive signals, territorial signals, or signals related to courtship. We can but speculate.

Q: Is basking behaviour likely for pliosaurs?

A: Lounging at the water surface (sleeping/resting) is plausible, either in deep water or shallow water, perhaps even in places where the animal is partly in contact with the sediment (though see caveat above about lying on the sea floor).

Irrefutable proof that Liopleurodon preyed on ichthyosaurs: cartoons! Image by Darren Naish.

Q: Do we know that Liopleurodon preyed on Ophthalmosaurus, the familiar contemporaneous ichthyosaur?

A: There are certainly ophthalmosaur bones marked with pliosaur bite marks – so, yes, Liopleurodon surely did predate on Ophthalmosaurus when it could catch it. I’m not sure if the bite marks we can see on ophthalmosaur bones demonstrate any preference as goes attack style, but it’s been stated that bitten plesiosaur bones tend to belong to the limbs. This has led to the irresistible notion that pliosaurs wrenched the paddles from plesiosaurian prey in order to disable them. There is even some data that supposedly shows a preference for (if I remember correctly) right-sided attacks!

Q: Any possibility of Liopleurodon eating drowned or swimming dinosaurs?

A: I think we can be confident that they did this. There’s even possible evidence for this, since armour plates from an ornithischian dinosaur were apparently found within the stomach contents of a pliosaur (Taylor et al. 1993).

There aren't many plesiosaur-themed books to collect - try collecting them all! Here's another one.

Clearly, there is – as I said above – a huge amount we don’t know about plesiosaur behaviour. It’s possible, perhaps likely, that we will never know about these sorts of things. Plesiosaur Peril is based on evidence as much as is possible, but we obviously had to speculate and extrapolate where appropriate.

I think that Plesiosaur Peril looks amazing and I’m sure that kids and other interested readers will enjoy it very much. And it’s not as if there are many books out there devoted to plesiosaurs already… there are, like, two or three… so a new one, produced for popular audiences, is a wonderful thing. My congratulations to Daniel on getting the book out there and on working so hard to popularise an amazing and somewhat under-appreciated group of animals. Buy Plesiosaur Peril now: Daniel announced its publication here at Skepticblog.

For previous Tet Zoo articles on plesiosaurs and other sauropterygians, see…

Refs – -

Bakker, R. T. 1993. Plesiosaur extinction cycles – events that mark the beginning, middle and end of the Cretaceous. In Caldwell, W. G. E. & Kauffman, E. G. (eds) Evolution of the Western Interior Basin: Geological Association of Canada, Special Paper 39, 641-664.

Benson, R. B. J. 2014. Faunal turnover of marine tetrapods during the Jurassic–Cretaceous transition. Biological Reviews 89, 1-23.

- ., Ketchum, H. F., Naish, D. & Turner, L. E. 2013. A new leptocleidid (Sauropterygia, Plesiosauria) from the Vectis Formation (Early Barremian-early Aptian; Early Cretaceous) of the Isle of Wight and the evolution of Leptocleididae, a controversial clade. Journal of Systematic Palaeontology 11, 233-250.

Buchy, M.-C., Frey, E. & Salisbury, S. W. 2006. The internal cranial anatomy of the Plesiosauria (Reptilia, Sauropterygia): evidence for a functional secondary palate. Lethaia 39, 289-303.

Campos, Z., Sanaiotti, T., Muniz, F., Farias, I. & Magnusson, W. E. 2012. Parental care in the dwarf caiman, Paleosuchus palpebrosus Cuvier, 1807 (Reptilia: Crocodilia: Alligatoridae). Journal of Natural History 46, 2979-2984.

Carpenter, K. 1997. Comparative cranial anatomy of two North American Cretaceous plesiosaurs. In Callaway, J. & Massare, J. (eds) Ancient Marine Reptiles. Academic Press (London), pp. 191-216.

- ., Sanders, F., Reed, B., Reed, J. & Larson, P. 2010. Plesiosaur swimming as interpreted from skeletal analysis and experimental results. Transactions of the Kansas Academy of Science 113, 1-34.

Cruickshank, A. R. I., Small, P. G. & Taylor, M. A. 1991. Dorsal nostrils and hydrodynamically driven underwater olfaction in plesiosaurs. Nature 352, 62-64.

Gans, C. 1989. Crocodilians in perspective. American Zoologist 29: 1051-1054.

Geister, J. 1998. Lebensspuren made by marine reptiles and their prey in the Middle Jurassic (Callovian) of Liesberg, Switzerland. Facies 39, 105-124.

Halstead, L. B. 1989. Plesiosaur locomotion. Journal of the Geological Society, London 146, 37-40.

Ketchum, H. F. & Benson, R. B. J. 2010. Global interrelationships of Plesiosauria (Reptilia, Sauropterygia) and the pivotal role of taxon sampling in determining the outcome of phylogenetic analyses. Biological Reviews 85, 361-392.

King, F. W., Thorbjarnarson, J. & Yamashita, C. 1998. Cooperative feeding, a misinterpreted and under-reported behavior of crocodilians. Available at: http://www.flmnh.ufl.edu/herpetology/herpbiology/bartram.htm

Loxton, D. 2011. Ankylosaur Attack. Kids Can Press, Toronto.

- . 2013. Pterosaur Trouble. Kids Can Press, Toronto.

- . 2014. Plesiosaur Peril. Kids Can Press, Toronto.

McHenry, C., Cook, A. G. & Wroe, S. 2005. Bottom-feeding plesiosaurs. Science 310, 75.

O’Keefe, F. R. 2001a. Ecomorphology of plesiosaur flipper geometry. Journal of Evolutionary Biology 14, 987-991.

- . 2001b. A cladistic analysis and taxonomic revision of the Plesiosauria (Reptilia: Sauropterygia). Acta Zool. Fennica 213, 1-63.

- . 2002. The evolution of plesiosaur and pliosaur morphotypes in the Plesiosauria (Reptilia: Sauropterygia). Paleobiology 28, 101-112.

- . & Chiappe, L. M. 2011. Viviparity and K-selected life history in a Mesozoic marine plesiosaur (Reptilia, Sauropterygia). Science 333, 870-873.

Riess, J. & Frey, E. 1991. The evolution of underwater flight and the locomotion of plesiosaurs. In Rayner, J. M. V. and Wootton, R.  J. (eds) Biomechanics and Evolution. Cambridge Uni. Press (Cambridge), 131-144.

Robinson, J. A. 1975. The locomotion of plesiosaurs. Neues Jahrbuch fur Geologie und Paläontologie, Abhandlungen 149, 286-332.

Smith, A. S. 2013. Morphology of the caudal vertebrae in Rhomaleosaurus zetlandicus and a review of the evidence for a tail fin in Plesiosauria. Paludicola 9, 144-158.

Tarsitano, S. F. & Riess, J. 1982. Plesiosaur locomotion – underwater flight versus rowing. Neues Jahrbuch für Geologie und Paläontologie 164, 188-192.

Taylor, M. A. 1987. How tetrapods feed in water: a functional analysis by paradigm. Zoological Journal of the Linnean Society 91, 171-195.

- . 1992. Functional anatomy of the head of the large aquatic predator Rhomaleosaurus zetlandicus (Plesiosauria, Reptilia) from the Toarcian (Lower Jurassic) of Yorkshire, England. Philosophical Transactions of the Royal Society of London B 335, 247-280.

- ., Norman, D. B. & Cruickshank, A. R. I. 1993. Remains of an ornithischian dinosaur in a pliosaur from the Kimmeridgian of England. Palaeontology 36, 357-360.

Wilhelm, B. C. 2010. Novel anatomy of cryptoclidid plesiosaurs with comments on axial locomotion. Ph.D. thesis, Marshall Univerisity, Huntington, WV.

Yamashita, C. 1991. Social fishing behavior in Paraguayan caiman. Crocodile Specialist Group Newsletter 10 (2), 13.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. cmchenry 6:16 am 03/3/2014

    Darren – great article about the single best group of reptiles that ever dominated marine systems for >100 million years. I didn’t know about the book but will hunt it down.

    Minor comment: I’m not sure we said that elasmosaurs were ‘mostly’ harvesting benthic prey. We wrote up two specimens that have evidence of benthic prey in their stomach contents… it’s not really enough to base a word like ‘mostly’ on. We drew attention to those specimens because most discussions about the functional advantages of the stupifdly hyper-elonagate elasmosaur neck were all conjecture about different ways to capture shoaling fish and squid – we simply wanted to point out that a structure, no matter how optimised for a particular function it may seem, is still probably capable of other functions. I have no doubt that the selective pressures acting upon the evolution of Muranosaurid/Elasmosaurid necks mainly involved the difficult task of catching small, agile, shoaling nekton, but that doesn’t necessarily mean that elasmosaurs were restricted to that diet. As I know you are well aware, delphinids (and pretty much every other group) display feeding behaviours that you wouldn’t necessarily expect from their morphlogy.

    It’s the difference between the verbs ‘for’ and ‘use’. When we say structures are ‘for’ X, that is a statement about the selective pressures that we think are involved with the origination/maintenance of a trait. But these are not necessarily the same as range of functions that structure X can be ‘used’ for. I’m pretty sure that my hind limb anatomy did not evolve for kicking a football, and yet it happens to be pretty good at that function. Do I think that elasmosaurs (and/or other long-necked plesiosaurs) evolved the most incredible neck in the animal kingdom to pick up cockles from the sea-bed? No. Could they use them for that role if they wanted? Sure – and we have some fossils that indicate this.

    Sorry, bit long for a comment about an article that I really enjoyed, but I think it’s an important (albeit subtle) point to make.

    Long live the lizard wings!

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  2. 2. naishd 6:22 am 03/3/2014

    Fair enough :)

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  3. 3. naishd 6:29 am 03/3/2014

    Oh, I should add that Les Noè gave a presentation at one of the SVPCA meetings on the idea that long-necked plesiosaurs as a whole may have routinely foraged on benthic prey. I would definitely agree that long necks did not constrain these animals to any one specific niche, but the evidence for negative buoyancy and so on does suggest a preference for being low in the water column.

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  4. 4. cmchenry 6:42 am 03/3/2014

    Les had been giving that talk for a while but I don’t agree with his interpretation. The negative buoyancy thing applies to some plesiosaurs but not to all.

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  5. 5. naishd 6:58 am 03/3/2014

    You know, someone needs to systematically cut up bones from a broad range of plesiosaurs, combine it with the data on inferred habitat and ecology, and tie it to analyses of neck flexibility, skull shape, and tooth morphology and so on. Only a PhD’s worth of work. I think we can all agree that plesiosaurs were doing diverse things. The problem at the moment is that there’s no clear idea of what each lineage was doing.. I mean, vague inferences made about cryptoclidid or plesiosaurid ecomorphology aren’t that different from ones made about elasmosaurids or microcleidids or whatever.

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  6. 6. Mark Evans 7:15 am 03/3/2014

    In a similar vein, it would seem that habitually swallowing a high number of relativley large stones is a xenopsarian behaviour, as discussed by Benson and Druckenmiller (2013). When gastroliths are found in taxa from other clades they tend to be fewer and smaller, sometimes approaching coarse grit.
    Great article, and the book looks good too. I have to say that I prefer your Cryptoclidus, with a nice large eye. The ones in the book look as if they all slightly worried about something. Probably that sneaky Liopleurodon!

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  7. 7. naishd 7:22 am 03/3/2014

    Thanks for that, Mark. As you’ll know, there’s been a push lately to downsize the eyes of fossil reptiles in reconstructions – I may have advised Daniel to do likewise on the cryptoclidids, can’t recall now. Another unknown: did these animals (and other Mesozoic marine reptiles) have eyelids? I reckon they did.

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  8. 8. Jerzy v. 3.0. 7:23 am 03/3/2014

    Do we know that plesiosaurs lacked a layer of fat, and their body contours traced skeleton?

    Cryptocolidus was not much bigger and its skeleton on the underside not weaker than elephant seals. The downward dange of movement of flippers was also big. Why it would be less able to crawl on land than an elephant seal?

    Liopreurodon skeleton seems to have long thin teeth and narrow throat, so maybe Liopreurodon itself was fish-catcher unable to eat bigger prey?

    Or, if it is simply not cool, maybe it dismembered caught plesiosaurus in a kind of crocodile death roll?

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  9. 9. naishd 7:31 am 03/3/2014

    Ah, the good ol’ “What about elephant seals?” thing :) Elephant seals (and, in fact, all pinnipeds) have a long list of features that are obviously linked to terrestrial locomotion, NONE OF WHICH are present in plesiosaurs. I’m planning to write this up as a paper (there’s very little data out there on form and function of the Mirounga skeleton)… but I plan lots of things.

    I don’t think Liopleurodon teeth can be described as thin… they’re massively stout, carinated, and with robust roots that are longer than the crowns. They really look suited for macropredation.

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  10. 10. Dartian 7:34 am 03/3/2014

    Darren:
    some extremely interesting ideas on breathing and olfactory behaviour have been proposed

    Interesting for sure, but unlikely IMO. Cruickshank et al. suggested that plesiosaurs could detect scents underwater. Fish and amphibians possess olfactory receptor cells of the kind that are functional underwater, but extant amniotes – even fully aquatic ones – only have olfactory receptor cells that are capable of detecting air-borne odorants (Freitag et al., 1995, 1998). Thus, they can’t smell underwater*. I suppose it’s possible that plesiosaurs were able to somehow circumvent this genetical constraint, but personally I wouldn’t bet on it. (It certainly begs the question why no other amniotes have been able to do likewise.)

    * Well, some water shrews and star-nosed moles apparently can, but they are cheating (Catania, 2006; Catania et al., 2008).

    This is a sort of ambush hunting I suppose.

    I don’t see why it wouldn’t be.

    there are whales (Kogia) that produce a cloud of reddish fluid (probably faeces) and then hide inside the cloud

    There are whales that do what? Wow! Reference, please.

    References:

    Catania, K.C. 2006. Underwater ‘sniffing’ by semi-aquatic mammals. Nature 444, 1024-1025.

    Catania, K.C., Hare, J.F. & Campbell, K.L. 2008. Water shrews detect movement, shape, and smell to find prey underwater. Proceedings of the National Academy of Sciences of the United States of America 105, 571-576.

    Freitag, J., Krieger, J., Strotmann, J. & Breer, H. 1995. Two classes of olfactory receptors in Xenopus laevis. Neuron 15, 1383-1392.

    Freitag, J., Ludwig, G., Andreini, I., Rössler, P. & Breer, H. 1998. Olfactory receptors in aquatic and terrestrial vertebrates. Journal of Comparative Physiology A 183, 635-650.

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  11. 11. Mark Evans 7:36 am 03/3/2014

    Yes, but Cryptoclidus does have some of the largest eyes relative to skull length among plesiosaurians, and cryptoclidids generally seem to be trying to make their orbits as big as they can. I agree about the eyelids, though.

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  12. 12. naishd 7:43 am 03/3/2014

    Kogia‘s ‘cryptic cloud’ is mentioned in most of the recent literature on these whales. I mentioned it in this ver 2 article. One of several key references…

    Scott, M. D. & Cordaro, J. G. 1987. Behavioral observations of the dwarf sperm whale, Kogia simus. Marine Mammal Science 3, 353-354.

    Interesting what you say, Dartian, about the flow-through breathing model. Plesiosaurs (and other sauropterygians) do have a peculiar set of palatal and narial features that are otherwise difficult to explain, however (though, as Mark Evans will tell you, not all plesiosaurs are built this way).

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  13. 13. Mark Evans 7:57 am 03/3/2014

    This is true (but unhelpful).

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  14. 14. JAHeadden 8:03 am 03/3/2014

    I appreciate the cautionary nature of the argument on “lip-like” structures in plesiosaurs, but let us not paint all plesiosaurs in the same brush. If the teeth would appreciably pass the opposing oral margin, we are sure to find jaw morphology similar to, say, Platanista or Gavialis — though in the former, a full “lippy” structure is present. But bands of tissue around the oral margin, as well as the oral mucosa itself, may influence the size of the teeth and obscure the apparent bases of the teeth. And that’s just in taxa like Cryptocleidus. What about Aristonectes, with much shorter, finer teeth? I’d imagine even in the longer-snouted, “pliosaur” morphs, some may very well have had thick extraoral integument, “swollen” mucosa (as in gharials), etc. We know that there is a line of neuovascular foramina lining the jaws, a probable indicator of thick oral tissues (in gharials as much as in plesiosaurs, as in lizards, etc.) which forces us to ask what these foramina correspond to and their relevant to facial integument. I quite imagine plesiosaurs were variable in facial integument; no one-model-fits-all.

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  15. 15. Jerzy v. 4.0. 8:40 am 03/3/2014

    “extant amniotes (…) can’t smell underwater”

    ??? My pet red-eared turtle obviously sniffs underwater. When it doesn’t like the smell (like vitamin powder wrapped in a piece of meat) you can actually see two puffs of water quickly expelled from the nostrils.

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  16. 16. Sordes 8:51 am 03/3/2014

    Really a great article Darren!

    I think it is really quite probable that plesiosaurs really lacked lips, because it is very hard to imagine how those interlocking and crisscrossing teeth should fit under lips, as they would most probably pierce in the softtissue of the antagonistic jaw and would require extremely big lips. We know what happens when teeth permanently push in tissue – funny holes, as seen in crocodylians, especially alligators. Even quite big teeth can be covered by lips if they are vertically, like in mosasaurs or whales, but this slanting teeth are really hard to imagine with working lips, especially if you keep in mind that usually the upper lips are longer and fleshier. And given the fact that many plesiosaur teeth really look like they should have worked as “combs” to catch smaller prey like smaller fish or small shell-less cephalopods, it seems more likely that fleshy lips would have inhibited such a sieving for hydrodynamic reasons.

    There is also a very different possibility for reproduction, or better said reproduction-related behavior. Instead of protecting a large baby for a long time, it could have been quite the opposite, and those really big babies were already quite independent and active from the very beginning, similar to certain sharks like great white sharks, or – if you prefer to look at tetrapods – ovoviviparous boids, slow-worms, common lizards or alpine salamanders. But of course, that´s also just a possibility, and I don´t prefer one of the two over the other, or possibly it was also something in between, like a short parental care for some days or weeks.

    I have to admit I have a really hard time to imagine a plesiosaur beaching itself. With this super-stiff bodies, they were probably similarly immobile as turtles, and probably even lesser adapted for “walks” on land, as they didn´t need to lay their eggs on beaches. In contrast whales have quite flexible bodies, and can use the full strength of their tail, back and abdominal musculature to lift their bodies and to move again into the water. If you look at videos of whales coming on land and going back into the water, you can see they make intensive use of the flexibility of their bodies.
    Same thing in wels, just with the difference that they move in lateral movement and bend their bodies to go back into the water. Around 2/3 of their length is only a quite strong and comparably flexible tail, which can also be used like a lever to raise the rest of the body. Totally unrelated to the rest of the topic, this behavior of wels which learned to partly beach themselves to catch pigeons on the riverside is mainly known from a river in France, but there is also another place in Italy where they have learned the same thing, but this was nowhere reported and not included in the paper which described the ones at France. What´s really interesting is that both populations date back to a comparably recent introduction (not from Russia as River Monsters will tell you, but from Germany I think), and this particular behavior was never reported within their (huge) original distribution.

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  17. 17. Mark Evans 8:58 am 03/3/2014

    The type (and only) specimen of Pliosaurus carpenteri has pathological lesions where the maxillary “caniniform” teeth impacted on the lateral surface of the dentary due to a misaligned jaw. At least on this occasion there can’t have been much in the way of lip tissue.

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  18. 18. Yodelling Cyclist 9:16 am 03/3/2014

    Great article, thoroughly enjoyed.

    With regards the idea of large baby=parental care, perhaps (dare I say it) we should recall the kiwi. Enormous egg, allowing a huge and highly precocial hatchling. Live birth is a necessary modifictaion to live at sea.

    Secondly, with regard to the terrestrial mobility idea, please recall that dugongs will not infrequently use shallow sandbanks to give birth in order to avoid sharks, even going so far as to deliberately ground themselves, while remaining awash while vulnerable in labour. Freeing themselves subsequently seems to be just a normal part of the process. I wonder if similar behaviour was present in plesiosaurs. [source]

    Finally, I love the spy hopping idea, as it gives yet another possible reason for the long stiff neck (pushing the observable horizon out), as opposed to a flexible neck which might seem more useful for prey capture (like a cormorant). Whether this was to watch for feeding signs, look for mates or look out for land as a means of navigation is an interesting field of pure speculation.

    Best wishes,
    Yod

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  19. 19. Yodelling Cyclist 9:19 am 03/3/2014

    Oh, a with regard to the fleshy extensions on the fins, should we be comparing with Humpback whales?

    What does their skeletal anatomy suggest?

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  20. 20. Dartian 10:34 am 03/3/2014

    Jerzy:
    My pet red-eared turtle obviously sniffs underwater. When it doesn’t like the smell (like vitamin powder wrapped in a piece of meat) you can actually see two puffs of water quickly expelled from the nostrils.

    Chelonians do indeed make ‘sniffing’ motions with their nostrils underwater. But that doesn’t mean that they can “obviously” smell fluid-borne chemicals. They could be ‘cheating’ in a similar (though not identical) fashion to the water shrews and star-nosed moles that I mentioned earlier; that is, by trapping air bubbles in their nasal cavities, into which dissolved volatile chemicals could escape from the surrounding water (in which case the chelonians’ olfactory epithelia are still smelling airborne, not fluid-borne chemicals). Or, alternatively, they could be detecting chemicals by using another sensory system altogether, most probably the vomeronasal system. For additional discussion, see Schwenk (2008).

    Reference:
    Schwenk, K. 2008. Comparative anatomy and physiology of chemical senses in nonavian aquatic reptiles. In Thewissen, J.G.M. & Nummela, S. (eds.): Sensory Evolution on the Threshold: Adaptations in Secondarily Aquatic Vertebrates, University of California Press, Berkeley / Los Angeles / London, pp. 65-81.

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  21. 21. naishd 11:25 am 03/3/2014

    Loving all these great comments, thanks everyone. Always remember that a lot of this stuff is not really discussed ANYWHERE in the literature… certainly not in the available literature, anyway.

    Sordes (comment # 16): given that plesiosaurs (well, polycotylids) grew gigantic babies, produced a really low number of babies, and were viviparous, the most likely conclusion – based on what we see in other reptiles – is that this correlates with parental care, kin recognition and so on (check out the O’Keefe & Chiappe paper). Of course, a major issue here is that n = 1, but not much we do about that…

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  22. 22. Jerzy v.3.1. 11:29 am 03/3/2014

    @Dartian
    I doubt there is any air remaining in the nostrils, given how forceful the turtle ‘exhales’ underwater and how much it can turn its head.

    Maybe it pumps water all the way to the mouth and, in a sense, tastes it. The strength of expulsion makes it likely.

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  23. 23. Heteromeles 11:51 am 03/3/2014

    Just to add the totally improbable but fun to think about:

    http://heteromeles.wordpress.com/2013/02/23/shocking-necks/

    I still think plesiosaurs would make great electric eels, especially since that big body gives them the equivalent of an outboard fuel tank, turbocharged by air-breathing lungs. I’d also add that LeeB (last comment) pointed out a way to look for skeletal evidence to prove or disprove this, which was a great addition. Thanks Lee

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  24. 24. naishd 12:07 pm 03/3/2014

    I wondered how long it would be before someone mentioned that :) (re: comment # 23).

    Regarding those mandibular and rostral grooves (the features LeeB refers to in the comment on your blog): to be fair, they’re very widespread… ichthyosaurs also have an internal system of branching canals in their premaxillary and dentary bones. Their function is unknown, but an electroreceptive role has been suggested (by which I mean: somebody said this once).

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  25. 25. Yodelling Cyclist 12:18 pm 03/3/2014

    Hehe, sky hopping, with long necks and electric organs? Bring on the radio masts.

    I’ll see myself out.

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  26. 26. Dartian 12:28 pm 03/3/2014

    Jerzy:
    I doubt there is any air remaining in the nostrils

    I was speaking of the entire nasal cavity, not just the nostrils.

    Anyway, thanks for the Kogia reference, Darren. I wasn’t yet a regular Tet Zoo reader by the tame you publishes that article; I’m pretty sure that I would have remembered it otherwise. I tend to remember things such as whales hiding in clouds consisting of their own faeces. ;)

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  27. 27. Dartian 12:32 pm 03/3/2014

    by the tame you publishes that article

    And I also tend to try to not make two obvious typos in the very same half-sentence…

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  28. 28. Heteromeles 1:00 pm 03/3/2014

    Thanks Darren. Actually, with 3-D printing, you could probably print out ichthyosaur or plesiosaur skulls with conductive nerve replicas (wires) in situ, and study the electrical fields around them, and whether they could be used as electrosensors in a saltwater tank with fish.

    I like YC’s suggestion of the radio masts, though. Maybe they used ELF waves to send mating calls around the world? :D

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  29. 29. Halbred 1:28 pm 03/3/2014

    Great article. Always happy to learn more about plesiosaurs. The hint you dropped about an unpublished specimen with flexible flipper ends makes me wonder (1) how many of these kinds of soft-tissue structures exist in museum back-catalogues; and (2) why they so often go unpublished (the “nippled” Triceratops skin impression comes to mind)? The interest is clearly there–sick a grad student on it or something.

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  30. 30. vdinets 1:47 pm 03/3/2014

    I wonder if these extensive rib cages could support massive muscle walls for infrasound production…

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  31. 31. Zoovolunteer 2:38 pm 03/3/2014

    I am not sure if this is a viable suggestion, but having seen film of “bait balls” of schooling fish being attacked by various predators, it occurs to me how such a tight school would react to a long necked plesiosaur attack. Approaching from the right angle, the mouth would be in a position to grab while the bulk of its body was still apparently (to the school) some distance away. A slow moving hunter in open water would need some way to get close if it was hunting fast moving prey.

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  32. 32. SciaticPain 3:10 pm 03/3/2014

    Personally I think sharks of the genus Somniosus may offer much insight into plesiosauromorph (long necked) foraging strategy.
    Carroll, Amy. “Sleeper Sharks: Awake and Hungry Sleeper sharks Not Culprits in Sea Lion Declines.” Alaska Fish and Wildlife News. 1999. Alaska Department of Fish and Game.

    On ammonite predation by plesiosaurs: Sato T, Tanabe K (1998) Cretaceous plesiosaurs ate ammonites. Nature. 394, 629-630 (13 August 1998)
    What is interesting about the above article is that only the mouth parts of the ammonites were recovered, not the shell. Did the plesiosaur wrench them free?
    For me ammonites were too abundant in the Mesozoic for plesiosaurs to ignore. I don’t know if anything is published on the late Jurassic Svalbard (Monster X) food chain but fish are said to be exceedingly rare there while cephalopods, especially shelled ones, numerous.

    Another weird thing consumed by plesiosauromorph: O’keefe FR, et al. (2009) A plesiosaur containing an ichthyosaur embryo as stomach contents from the Sundance Formation of the Bighorn Basin, Wyoming. Journal of Vertebrate Paleontology. 29(4) 1306-1310

    What is interesting in the above paper is that the skeleton is disarticulated, suggesting that the plesiosauromorph may have dismembered the (probably) scavenged carcass. Plesiosauromorphs are usually considered gape limited predators unable to break up larger carcasses but the above account and several more anecdotal accounts http://www.oceansofkansas.com/plesio4.html may suggest otherwise.

    But go look at the skull of some elasmosaurids, Zarafasaura is a good one: http://en.wikipedia.org/wiki/File:Zarafasaura_oceanis.jpg
    no matter that it is small compared to the whole animal, it still appears pretty solid, with big rooted teeth, and good jaw closing muscles. In my view over-designed for fish no bigger than a large trout…

    Maybe these guys could have death rolled larger carcasses cooperatively into smaller pieces, especially as it seems likely based on K-strategy reproduction that group living was a high probability?

    Compare the skulls of elasmosaurids/plesiosauromorphs to eels, bichirs, and caecilians- all known to use twist/rotational feeding- and you will notice some similarities.

    Not suggesting long-necked plesiosaurs were arch-predators on the order of pliosaurs- just that maybe some could handle prey/scavenge on items larger than generally assumed.

    Duane Nash

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  33. 33. Sordes 3:24 pm 03/3/2014

    Darren, that´s of course an argument. I just wanted to show that there is also a completely different scenario possible. For example great white sharks have a gestation period of 11 months and have usually litters from 2-10 juveniles which are already 1,20-1,50 m in length and around 30 kg in weight, so the situation is not even that different. Perhaps ichthyosaurs are a better analogue for them, as a single baby is indeed quite extreme. However, we have to keep in mind that the single-baby-form could have been a more derived feature, and more primitive plesiosaurs gave possibly birth to bigger litters of smaller juveniles and did not show (much?) parental care. Of course that´s speculation again, but I could well imagine that there were several different ways of reproduction or interaction with juveniles within an evolutionairy history of more than 100 mio years.

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  34. 34. Boesse 7:01 pm 03/3/2014

    Nice stuff – a few comments:

    Jamie – there are lips present in Platanista, but the teeth are still nearly entirely exposed (perhaps a good analogue for plesiosaurs?).

    Darren – breaching behavior in modern cetaceans has also been hypothesized to be a method for removing barnacles and other epibionts.

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  35. 35. Tayo Bethel 7:45 pm 03/3/2014

    @Naishd:
    Great article, as usual. Lots of info not only on plesiosaursbut hints of interesting things about other reptiles as well. I didn’t know that spiny-tailed goannas were any more social than other varanids, for example. Why has there been a trend to downsize the eyes of marine reptiles? Eye size seems to be variable among marine tetrapods; deep-diving pinnipeds have quite large eyes, for example, whereas cetaceans tend to have smaller eyes and some,like some river dolphins, have very small eyes. Perhaps those plesisaurs with large eyes hunted in deep but clear water, as Weddell seals do, whereas those with smaller eyes preferred murkier conditions.

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  36. 36. JAHeadden 7:52 pm 03/3/2014

    @ Sordes (#16): I hedge on painting plesiosaurs with the same brush. It is possible that some plesiosaurs have a different extraoral integument than others. No one has gone to try checking. I have little doubt that the splayed teeth of Cryptocleidus would be visible, but the reasons for this are based on incredulousness, not on specific features or comparative anatomy by which to determine why. I use gharials and SA river dolphins as examples because they show the regular, idodont tooth morphology of plesiosaurs, though the angles are often different. Their oral tissues are also vastly different. I bring up short-toothed plesiosaurs to try to conceive (hypothesize) possible exceptions.

    @ Mark Evans (#17), on tooth occlusion of the jaws preventing “lip tissue,” brought up by Sordes above: This also happens in cats and dogs, the examples producing bone, tooth, and integumental pathologies. This doesn’t preclude the lack of lips in those mammals. But again, my arguments draw away from generalizing (so, even if one plesiosaur might have some “lippy” integument, they don’t all have to be so restored).

    @ Boesse (#34): Definitely all true. But I’ve found that some Platanista vary in this, from just the first few teeth exposed and then extending down the jaw. The rear teeth seem always to be covered, but I can’t qualify this at the moment. Hypothetically, they may recede as the teeth grow, suggesting that scale is a factor. But the lips would still be there, and prevent the margin of the teeth or the jaws from being fully visible. Such a thickened tissue certainly alters the oral margin’s shape and of the head in general.

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  37. 37. Yodelling Cyclist 8:39 pm 03/3/2014

    With regards elasmosaurids/plesiosauromorphs death rolling carcasses to bits: this is may be yet another reason why the necks were so stiff, and the skulls seemingly overbuilt. This was, in this scenario, a necessary adaptation to withstand the torque generated by the pectoral fins around such a small head. Indeed, that may have even driven the heads to be small, and the paddles large, to really push the available torque. Any scavengeable prey that would have required awesome torque to open up? Actually, if Heteromeles is right about asymmetric neck vertebrae (and I know little of the anatomical features he referred to in his blog post), this may further be an adaptation to lock the neck against a particular, preferred, roll direction. Furthermore, I suspect it would be an advantage to have the centre of mass at the centre of torque, i.e. on the pectoral girdle.

    All this speculation suffers heavily from the presence of fish remains as plesiosaur gut contents, though, and the extreme length of the neck (together with the sheer number of vertebrae) would have a distinct draw back in death rolling. Which is a shame, because an animal specifically evolving to act like an underwater T-handled socket wrench of death is oddly appealing to me.

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  38. 38. SciaticPain 9:30 pm 03/3/2014

    @Yodelling Cyclist. Yes the fish problem I have looked at that and a number of elasmosaurids show fish scales, indicative of a possible limitation of size swallowed. Maybe larger fish, with numerous bones in the flesh were generally avoided. Large cephalopods would not pose such a problem. But we also have plesiosauromorphs with embryonic ichthyosaur remains, various benthos, ammonites and if you look back further in the literature the field notes of Cope mentions fish scales, broken up bits of pterosaurs, and ammonite in some individuals. If I was to sum up plesiomorph diet in one word it would be generalist. And if plesiosauromorphs were using rotational feeding to rip off chunks of flesh from large critters we might never know that they did so as, without hard parts, when swallowed these bits would likely not fossilize. So there is a possibility that small stuff remains- swallowed whole bones, beaks and all- could show a fossil bias in plesiosaur guts in favor of their preservation. But, yeah, that is a convenient defense…

    T-handled socket wrench of death I like it. Since maybe some of you are catching on to me I think this is what plesiosauromorphs were doing and I am actually trying to piece together enough of an argument to turn it into an actual paper. Ultimately I am arguing that ammonite predation was the chief impetus towards the unique design of plesiosauromorphs. I do not think it is a coincidence that the Elasmosaurids were coincident with the largest ammonites during the Cretaceous. And yes I think Elasmosaurids were ratcheting giant ammonites out of their shells (paleoartists GO!!). I also do not think it is a coincidence that Cenozoic oceans lack both abundant pelagic shelled prey similar to ammonites and also lack predators that are morphologically similar to plesiosauromorphs.

    But I want to be careful with the idea of specialist. Think of the leopard seal, teeth specialized for filtering krill but field observations pointing to a generalist diet.

    Duane Nash antediluvian salad

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  39. 39. John Scanlon FCD 4:40 am 03/4/2014

    “leopard seal, teeth specialized for filtering krill”

    You meant crab-eater, didn’t you?

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  40. 40. naishd 4:50 am 03/4/2014

    So many interesting comments – thanks, everyone.

    I’m very interested in Duane’s idea (comments # 32 and 38) about the possibility of elasmosaurids eating ammonoids… though note, with respect to the article and Plesiosaur Peril, that these ideas are not necessarily relevant to cryptoclidids. At the moment I certainly think that elasmosaurids were generalised, though I also agree with those who note that plesiosauromorphs were not all dainty-skulled, delicate animals as might be implied by some reconstructions. Their skulls sometimes (or often) are robust, deep and/or broad across the snout, and perhaps capable of resisting high bite stresses.

    Note, however, that the plesiosaur with the ammonoid remains inside it (Duane mentions it in comment # 32) is a polycotylid, and thus a pliosauromorph, not a plesiosauromorph.

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  41. 41. naishd 4:56 am 03/4/2014

    Leopard seal dentition (comments # 38 and 39): I think Duane did indeed mean Leopard seal. They have multi-cusped post-canines that can be used in filtering. Some populations get a reasonable amount of their dietary requirements by filtering krill.

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  42. 42. LeeB 1 5:48 am 03/4/2014

    I wonder how long vertical spy hopping elasmosaurs could keep their heads out of the water before they passed out from lack of blood to the brain; that is a long way up for the heart to pump blood.

    At least while they were swimming in groups it would be safer for them while breathing at the surface, whereas individuals swimming alone would seem to be vulnerable to being sneaked up on by predators while their eyes and ears were above the water.

    And the idea of pliosaurs disabling plesiosaurs by biting their flippers seems possible but I would think the neck would also be an obvious and inviting target for a bite, unless of course they could generate stunning electric shocks.

    And if an elasmosaur wanted to feed on an ammonite it could possibly shatter it’s shell by striking it with it’s flipper.

    Or if it could generate subsonic sounds perhaps it could focus them along the neck and stun prey in front of the mouth.

    LeeB.

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  43. 43. naishd 6:00 am 03/4/2014

    Elasmosaurids are an interesting paradox as goes the so-often-mentioned blood pressure problem. As long-necked animals, they might have evolved the same solutions as those present in terrestrial climbing snakes (where vertical climbing is allowed by compensatory increase in blood pressure and by smooth muscle control around blood vessels). But, as fully aquatic animals, we might predict that (like marine snakes) they had very low blood pressure and were poor at dealing with blood pooling. Either way, the idea behind the Conway painting is that the animals are having to work really hard – it’s a show of strength and endurance, as expected for sexual display.

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  44. 44. Yodelling Cyclist 7:41 am 03/4/2014

    With regards keeping the head out of the water, there is a phenomenon known (the name of which I just can’t remember, and my notes are in a different city) whereby humans who have been stranded on the sea surface with their heads above water, and body oriented ~vertically for long periods have their blood pressure drop dramatically. The pressure of the water at the feet helps keep blood in the head.

    This was discovered when helicopter rescues became common – if you pull someone out of the water vertically, they’ll blackout, suffer severe shock or die on the hoist. This accounted for several fatalities in the 1979 Fastnet race disaster. In order to prevent this rescues are now attempted using horizontal stretchers, which are very difficult to deploy in adverse sea states.

    All that chat very much aside, my point is that the water column will be helping keep blood in the head of a spy hopping elasmosaur. It would still be tricky to pump blood ~5m into the air, though.

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  45. 45. Yodelling Cyclist 7:42 am 03/4/2014

    I should clarify, I’m assuming the body hanging vetically under water, like a sleeping sperm whale.

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  46. 46. Jerzy v. 3.0. 8:06 am 03/4/2014

    Re: ichtyosaur and plesiosaur electroreception

    It would be interesting to correlate these canals in skulls to features wike eye size and body shape. Electroreceptors are usefyul for a nocturnal or benthic feeder, but much less for a sight-oriented pelagic hunter.

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  47. 47. Heteromeles 9:12 am 03/4/2014

    True, Jerzy. The other perceptual problem is that long-necked body-forms have a substantial blind-spot problem. Unless their necks are quite flexible and they are constantly moving them, they can’t see any of their body. How could a long-necked plesiosaur spot a pliosaur sneaking up on them from behind, for example?

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  48. 48. SciaticPain 10:04 am 03/4/2014

    For those interested I did a couple of very rough sketches on my idea of ammonite de-shelling: or the T-handled Socket Wrench of Death.

    Yes Another Hypothesis on Long Necked Plesiosaur Feeding Ecology
    http://antediluviansalad.blogspot.com/2014/03/yes-another-hypothesis-on-long-necked.html

    As Darren points out the Japanese specimen is a polycotylid and therefore has more of a pliosaur body type- so maybe instead of rolling it shook out the ammonites -but it did serve as an inspiration in how de-shelling might have occurred in other longer necked taxa. And the boundary between these two morphological (phylogenetically the distinction is useless) groups has been getting more and more blurred- both phylogenetically and morphologically- in recent years. Look at Rhomaleosaurus- pretty good sized head there, but also a fairly long neck- my point is that there is a lot of plasticity in plesiosaur evolution and maybe certain behaviors were common to both morphological groups as they seem to have re-evolved both morphologies over time.

    Also another thing to think about with ammonite de-shelling is that the living animal did not occupy the whole shell only the larger segments of the shell at the end of the coil. And therefore wrenching out such a tasty bit may have been a commonly employed tactic.

    Duane Nash

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  49. 49. Tayo Bethel 11:36 am 03/4/2014

    How might plesiosaurs have used their hind flippers? The enlarged hind flippers of some plesiosaurs suggests that they provided much of the power for swimming.

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  50. 50. ChasCPeterson 12:44 pm 03/4/2014

    Yet another fascinating article about yet another group of fascinating tetrapods. O for a functional time machine! (Even a little one; we could send back some quadcopter drones pre-porogrammed to fly video transects and then return to a predesignated spot for re-temporalization.)

    Manta rays breach too, and it’s quite a spectacular sight.

    extant amniotes – even fully aquatic ones – only have olfactory receptor cells that are capable of detecting air-borne odorants (Freitag et al., 1995, 1998). Thus, they can’t smell underwater.
    wut
    I’ve never heard this claim before, but without current access to the cited articles I find it extremely dubious. For one thing, aquatic turtles are routinely captured in sardine (or canned corn) baited traps. Are they tasting their way to them? What possible good is an ability to only detect airborne odors to (say) a male snapping turtle?
    For another, even airborne odorants have to first go into solution on the surface of the olfactory mucosa before they are received. How would olfactory receptors “know” (and why would they “care”) whether a chemical was delivered to the mucosa in air or in water??

    Live birth is a necessary modifictaion to live at sea.
    obviously not. Sea turtles.

    Why has there been a trend to downsize the eyes of marine reptiles?
    ichthyosaurs.

    Elasmosaurids are an interesting paradox as goes the so-often-mentioned blood pressure problem.
    I’d have to think about it, but I’m not sure there’s problem at all underwater.

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  51. 51. naishd 1:07 pm 03/4/2014

    Ah – I had missed the comments about underwater sniffing. It’s been known for a long time (since the 1950s) that sea turtles have huge olfactory bulbs: this was regarded either as a bit of a paradox, or as evidence that the turtles were only sniffing things when in air. This inspired a number of studies on underwater olfaction… sorry, Dartian, turtles almost certainly CAN sniff – in the strictest sense possible – underwater (Manton et al. 1972). These authors even tinkered with the olfactory nerve in order to see if true olfaction (rather than another form of chemoreception) was going on. Other studies have since been done which confirm that turtles do practise olfaction underwater.

    Plesiosaurs aren’t turtles, but the fact remains that underwater olfaction is known for reptiles. You can see for yourself, since I just found the paper online…

    Manton, M. L., Karr, A. & Ehrenfeld, D. W. 1972. Chemoreception in the migratory sea turtle Chelonia mydas. Biology Bulletin 143, 184-195.

    On blood pressure: ChasCPeterson (comment # 50) – the blood pressure problem I referred to is the one concerning how long-necked animals deal with the problems of blood pressure in air… that is, relevant to plesiosaurs should they raise their necks to the vertical.

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  52. 52. Yodelling Cyclist 1:14 pm 03/4/2014

    To clarify the blood pressure issue, body in water, neck out of water.

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  53. 53. DavidMarjanovic 1:20 pm 03/4/2014

    I’m back. I got this e-mail from the webmaster, who is anonymous for good reasons:

    We apologize for any inconvenience, however the new system does not accept symbols in the screen name field, and accounts with symbols, but without active subscriptions, were not imported to the new system. I’m sorry for any inconvenience, please create a new commenting account, omitting symbols from your screen name choice.

    So, in the 21st century, they downgraded their system – and didn’t even tell anyone (not even their bloggers). I cannot help finding this breathtaking.

    The new screen names may only contain letters and numbers. Even underscores are not allowed. Mark Evans, Jerzy, LeeB, Yodelling Cyclist and John Scanlon, next time the system logs you out, I expect that your accounts will be deleted because of the space in your screen names!

    *deep breath*

    Back to the topic.

    Another unknown: did these animals (and other Mesozoic marine reptiles) have eyelids? I reckon they did.

    All cetaceans have eyelids, right? Because if so, the only tetrapods without eyelids are salamanders that haven’t metamorphosed and pipids.

    Elephant seals (and, in fact, all pinnipeds) have a long list of features that are obviously linked to terrestrial locomotion, NONE OF WHICH are present in plesiosaurs. I’m planning to write this up as a paper (there’s very little data out there on form and function of the Mirounga skeleton)…

    YES YES YES YES YES!!! Please do that! The neontologists aren’t gonna do it on their own!

    extant amniotes – even fully aquatic ones – only have olfactory receptor cells that are capable of detecting air-borne odorants (Freitag et al., 1995, 1998). Thus, they can’t smell underwater*.

    This strikes me as an oversimplification. The papers make clear that class I olfactory receptors are for hydrophilic substances that doesn’t evaporate easily even at small molecule sizes (amino acids for example) while class II ones are for hydrophobic stuff; the few investigated teleosts have only class I, birds and mammals have only class II; Xenopus laevis* and Pelophylax synkl. esculentus have both, though the latter only expresses class II as an adult (when it’s terrestrial); the dolphin Stenella coeruleoalba has only pseudogenes of class II; Latimeria chalumnae has both, but 7 of the 11 identified members of class II are pseudogenes. “Interestingly, every Latimeria receptor shows higher similarity to a mammalian or amphibian receptor subtype than to another Latimeria sequence. Most notable is the remarkably high sequence similarity of LCor 27 to the human receptor HSor10 (82%) and the rat receptor RNor5 (80%).” Class II as a whole must thus be at least as old as the sarcopterygian crown-group. As coelacanths do not have terrestrial ancestry, I don’t think the function of class II receptors is completely limited to the terrestrial realm. “Hydrophobic” rarely means “completely unsoluble in water” – which is why water shrews and star-nosed moles can cheat.

    Poor cetaceans. No sense of smell, almost no sense of taste.

    Interestingly, the second paper consistently distinguishes Latimeria from “fish”, going so far as to say “fish and Latimeria” on p. 645. :-)

    …Finally, anecdotal evidence: I can smell water. It’s a useless superpower: I can smell rain seconds before or after the first drops reach the ground, and I sometimes smell a pond hidden by a hedge when I’m on the other side of that hedge, that’s it. I’ve read that the earthy smell that sometimes occurs during or after rain is actually actinomycete spores, not the water itself, but that’s probably not the same smell, doesn’t explain why I can smell ponds sometimes, and doesn’t explain why I perceive an overwhelming version of this smell when I get water (or milk) into my nose. Precisely how specific class II is to hydrophobic molecules may still need to be investigated.

    * Who knows which species it really is. I don’t think the authors would have noticed if they had investigated even Silurana tropicalis instead! In the first paper they say “homology” instead of “identity”, “phylogenetic scale” instead of “phylogenetic tree”, and wax poetic about how well adapted Xenopus is to both aquatic and terrestrial life – when in reality it’s as fully aquatic as a plesiosaur.

    For those interested I did a couple of very rough sketches on my idea of ammonite de-shelling: or the T-handled Socket Wrench of Death.

    I like that.

    You’d get a lot more comments on your blog, BTW, if you allowed name/URL comments instead of just Google login and OpenID ones.

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  54. 54. Yodelling Cyclist 1:35 pm 03/4/2014

    Woohoo! Danger Mouse is back!

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  55. 55. Heteromeles 2:20 pm 03/4/2014

    @53: David. Sorry for your loss of characters. Still, I hate to break it to you, but lots of people can smell water. I can too. Gary Nabhan even wrote a really cool book titled The Desert Smells Like Rain. If you want to level up in useless superpowers, try using Haidinger’s Brush to see polarized light, or spotting a comet during the day (yes, I’ve done both, although Haidinger’s Brush was much easier back when I ate large amounts of carrots).

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  56. 56. DavidMarjanovic 2:34 pm 03/4/2014

    :-D

    Turns out they sent out e-mails about the impending changes to all their paid subscribers. Most of their commenters, I bet, are not paid subscribers of Scientific American.

    I’ve used the opportunity to ask for the <blockquote> tag…

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  57. 57. DavidMarjanovic 2:36 pm 03/4/2014

    lots of people can smell water. I can too.

    Very good, this bolsters my hypothesis :-)

    Haidinger’s Brush to see polarized light

    Tried once, didn’t seem to work; I ate lots of carrots at the time. I’ll try again.

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  58. 58. ChasCPeterson 3:13 pm 03/4/2014

    the only tetrapods without eyelids are salamanders that haven’t metamorphosed and pipids.
    and snakes, and xantusiids, and non-eublepharid geckos inc. pygopodids…

    lots of people can smell water
    I’m skeptical. Ponds generally stink, and it ain’t the H-2-O. The strong sensation of water in the nasal cavity is probably either non-olfactory or just sensory overload.
    The desert smells like rain because of volatile plant oils (mostly from creosote bush here in the Mojave) and petrichor.
    I would bet money that nobody can detect ambient-temperature water vapor olfactorily.
    I would

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  59. 59. Yodelling Cyclist 3:57 pm 03/4/2014

    Dude, if you can smell actually water then the world should stink all the time from your own sweat and mucosal membranes.

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  60. 60. Dartian 4:03 pm 03/4/2014

    Well, chelonians are not included in those olfactory receptor cell studies that I cited. And the review by Schwenk that I also cited earlier notes that, judging by empirical observations, chelonians might be able to smell underwater (although he personally does lean more towards them instead using their vomeronasal sense underwater). So I concede the point that chelonians might actually turn out to be exceptional among the amniotes regarding their olfactory capacities (although that still remains to be demonstrated). Having said that…

    Chas:
    Are they tasting their way to them?

    Probably not, unless they happen to get very close. (Is it known over how long distances they can detect such bait?) But they may detect chemicals in the water with their vomeronasal – not their olfactory – sense.

    What possible good is an ability to only detect airborne odors to (say) a male snapping turtle?

    Has anyone ever studied the olfactory organ of that species? How well-developed is it really? (There isn’t exactly an overabundance of literature on chelonian nasal morphology.)

    How would olfactory receptors “know” (and why would they “care”) whether a chemical was delivered to the mucosa in air or in water??

    I don’t think anybody knows that for sure yet, but there are known structural differences between class I (‘aquatic’) and class II (‘aerial’) olfactory receptors. The class I receptors have a longer extracellular loop (i.e., consisting of a longer chain of amino acids) than class II receptors. So it’s apparently not really about the chemical, but about the structure of the receptor molecule.

    Darren:
    sorry, Dartian, turtles almost certainly CAN sniff – in the strictest sense possible – underwater (Manton et al. 1972)

    Yes, they can sniff (as I said in comment #20). But the fact that they move their nostrils underwater does not necessarily mean that they have functional underwater olfaction too. That paper that you cite (I appreciate you linking to the pdf, BTW!) does not conclusively demonstrate that. It is from 1972, so the authors can hardly be blamed. Back in those days, the structure and function of the vomeronasal organ wasn’t fully understood; in fact, it was at that time still largely thought to be a mere subsystem of the main olfactory system (hence it was often called the ‘accessory olfactory system’). Manton et al. do not make a functional distinction between those two: indeed, they say on page 192 that “For purposes of this discussion we assume that “olfaction” is mediated by the entire sensory epithelium of the nasal cavity, which includes some tissue possibly homologous with Jacobson’s organ of other reptiles, and which is innervated by the vomeronasal nerve”. In other words, they conflate the olfactory and the vomeronasal sense. Thus, the turtles in their experiment could have been detecting chemicals in the water with their vomeronasal organs, not their olfactory organs – in which case they weren’t technically ‘smelling’.

    (The above may sound like semantics, but I want to point out that different chemical senses are not equivalent. If the turtles had detected those chemicals with their gustatory sense, I don’t think that anybody would be saying that they ‘smelled’ them. But it is probably intuitively easier for us humans to understand the difference between smell and taste than the difference between smell and vomeronasal sensing.)

    David:
    coelacanths do not have terrestrial ancestry

    Can we actually be quite sure about that? (Well, if not ‘terrestrial’, then at least ‘amphibious’.)

    Poor cetaceans. No sense of smell

    Only true of odontocetes. At least some mysticetes still have a functional sense of smell, which they appear to be using to detect odours (above the surface) of large concentrations of prey animals such as krill.

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  61. 61. Andreas Johansson 4:19 pm 03/4/2014

    David Marjanović wrote:
    So, in the 21st century, they downgraded their system – and didn’t even tell anyone (not even their bloggers). I cannot help finding this breathtaking.

    Here’s a dollar saying they didn’t tell anyone because they didn’t know they did it until you wrote them and they had to figure out what was going on.

    I should add that I’ve been logged out repeatedly during your absense without the space causing my account to be deleted, so I expect the others are safe.

    On vomeronasal sniffing, I note that the WP pages on “Vomeronasal organ” and “Olfaction” refers to it as the accessory olfactory system.

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  62. 62. Andreas Johansson 4:22 pm 03/4/2014

    Drat. The entire paragraph following “David Marjanović wrote:” was supposed to be italicized and the “down” was supposed to be bold. Can we have an edit function along with the blockquote?

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  63. 63. Jurassosaurus 5:21 pm 03/4/2014

    Tayo Bethel wrote: The enlarged hind flippers of some plesiosaurs suggests that they provided much of the power for swimming.

    I wouldn’t be surprised. Most reptiles are “rear-wheel driven,” using their forelimbs more for steering than propulsion.

    Of course extant sea turtles are forelimb powered, but as was just discussed regarding underwater “smelling,” turtles are the exception to every rule.

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  64. 64. Heteromeles 6:02 pm 03/4/2014

    Actually, what you sense with oncoming rain is a change in relative humidity. It’s not limited to your nose, but that’s one place that can be sensitive.

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  65. 65. naishd 6:15 pm 03/4/2014

    As usual, it turns out the ‘turtles can practise underwater olfaction’ thing is a little complicated.

    Yes, there are several studies showing that marine turtles flood the olfactory chamber, use buccal pumping to ‘sniff’, and can detect chemical cues in water (Schwenk 2008, Endres et al. 2009) (see Druzisky & Brainerd 2001 on buccal pumping as well)… But the issue of whether they are definitely practising olfaction or using another chemosensory sense (like vomerolfaction) seems unresolved. I only just discovered that Schwenk (2008) provides a useful review of olfaction and possible olfaction in all reptile groups – including plesiosaurs. Therein, it’s argued that turtles are relying on vomerolfaction, not olfaction in the strict sense.

    Having said all this… ok, so maybe ‘underwater sniffing’ plesiosaurs (and other fossil marine reptiles) weren’t ‘smelling’ water in the strict sense. The fact remains, however, that perhaps they really were testing inhaled water for sensory cues, but maybe using their vomeronasal organs instead of their olfactory ones. In other words, Cruickshank et al.’s model remains completely viable, the one thing about their paper perhaps being objectionable is that they used the word “olfaction” in the title.

    Refs – -

    Druzisky, K. A. & Brainerd, E. L. 2001. Buccal oscillation and lung ventilation in a semi-aquatic turtle, Platysternon megacephalum. Zoology 104, 143-152.

    Endres, C. S., Putman, N. F. & Lohmann, K. J. 2009. Perception of airborne odors by loggerhead sea turtles. The Journal of Experimental Biology 212, 3823-3827.

    Schwenk, K. 2008. Comparative anatomy and physiology of chemical senses in nonavian aquatic reptiles. In Thewissen, J. G. M. & Nummels, S. (eds) Sensory Evolution on the Threshold. Adaptations in Secondarily Aquatic Verterbrates. University of California Press, Berkeley, pp. 65-81.

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  66. 66. SciaticPain 9:29 pm 03/4/2014

    @DavidMarjanovic Thanks I changed it, about a year ago I was getting loads of robots/ads and crap leaving comments so I changed to google account openid.

    Another weird thing regarding plesiosaurs is the question of strange paired foramen on their vertebrae?
    http://www.thefossilforum.com/index.php?/topic/38373-does-anyone-know-the-purpose-of-paired-foramina-on-plesiosaur-and-pliosaur-vertebrae/

    Maybe there was an interesting buoyancy control thing going on where they could shunt fluids/oils throughout the spinal column to effortless rise/lower their position in the water column? Would make for a scary good way to silently move and stalk through the water…

    Anyone else heard of this or have any papers/refs?

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  67. 67. Mark Evans 4:53 am 03/5/2014

    The function of the subcentral foramina has been discussed over the years, and I’ve heard people suggest something along those lines, but I’m not aware that anything convincing has been published. They are present in the cervical vertebrae of most plesiosaurians, only being absent in some pliosaurids (old adult Peloneustes and in brachauchenines). They are also there in some non-plesiosaurian pistosauroids (Augustasaurus, Pistosaurus) but apparently absent in others (Yunguisaurus). The foramina rise up onto the lateral surfaces of the dorsals, and then descend again to the ventral surface of the caudals in some (most?) plesiosaurians.

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  68. 68. Jerzy v. 3.0. 5:08 am 03/6/2014

    I wonder how juvenile plesiosaurs fed? Unless female was feeding them, I think the presence of a parent was a disandvantage for a youngster to catch fish.

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  69. 69. Yodelling Cyclist 11:30 am 03/6/2014

    Wait, wait, I realise I’m operating under a massive misapprehension, what are sauropterygians? For a long time I had subconsciously assumed they were archosaurs – which is clearly wrong on many levels, so where do they fit in? Clearly they were diapsids, but what flavour of diapsid?

    Oh, and since “we” were wondering about about the number of nuggets one could get form a pterosaur, the pectoral muscles on plesiosaurs must have been impressive, and quite possible tasty…

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  70. 70. ChasCPeterson 9:08 pm 03/6/2014

    the blood pressure problem I referred to is the one concerning how long-necked animals deal with the problems of blood pressure in air… that is, relevant to plesiosaurs should they raise their necks to the vertical.
    I know. I guess I was suggesting that it’s a good reason to suspect that they didn’t do so.

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  71. 71. ChasCPeterson 9:10 pm 03/6/2014

    My understanding is that Sauropterygia are lepidosauromorphs, not archosaurs.

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  72. 72. Yodelling Cyclist 9:40 pm 03/6/2014

    So are we talking squamate, sphenodont or something else entirely?

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  73. 73. Tayo Bethel 3:02 am 03/7/2014

    Jurassosaurus:
    A study of the caudofemoralisin plesiosaurs would be very interesting, then. Is steering such a demanding muscular effort that it requires reinforced pectoral girdles?

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  74. 74. Gigantala 10:26 am 03/7/2014

    @What are sauropterygians: Recent studies seem to place them closer to Archosauromorpha than to Lepidosauromorpha, though for obvious reasons this is as good a guess as any.

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  75. 75. DavidMarjanovic 2:39 pm 03/7/2014

    Diapsid phylogeny, and likely amniote phylogeny, is squamous gibbering madness. People I know are beginning to work on it, and I’ll try to take a peek from the amniote root, but don’t expect to go mad from a revelation soon.

    “the only tetrapods without eyelids are salamanders that haven’t metamorphosed and pipids.”
    and snakes, and xantusiids, and non-eublepharid geckos inc. pygopodids…

    All of these do have eyelids – they’re just fused and transparent. Separate eyelids, of which the lower one has a transparent window, occur in some (other) burrowing squamates.

    Ponds generally stink

    That’s different. (Several different stenches in fact.)

    Dude, if you can smell actually water then the world should stink all the time from your own sweat and mucosal membranes.

    Clearly it takes much higher moisture contents than that. Also, I sweat less than many people, and my nose almost always finds the air too dry.

    David:
    “coelacanths do not have terrestrial ancestry”

    Can we actually be quite sure about that? (Well, if not ‘terrestrial’, then at least ‘amphibious’.)

    Yes. All coelacanths dead or alive completely lack any adaptations to carrying their weight, let alone pushing it forwards by their paired fins. The same, incidentally, is true of many animals much closer to us, like Eusthenopteron; all those illustrations showing it on land or peeking out of the water that were produced for decades are untenable. Not counting aestivation in lungfish, no non-elpistostegalian sarcopterygian shows any evidence of having been any more terrestrial than an eel or a Silurus catfish – likely even less.

    Actually, what you sense with oncoming rain is a change in relative humidity. It’s not limited to your nose, but that’s one place that can be sensitive.

    It feels like a smell, though. On the other hand, as mentioned, it’s not all that sensitive: useless superpower.

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  76. 76. ChasCPeterson 11:37 pm 03/7/2014

    All of these do have eyelids – they’re just fused and transparent.
    huh…that seems to be correct. I had no idea that the spectacle was homologous to movable eyelids. Today’s learnin’!

    Link to this
  77. 77. LeeB 1 6:40 pm 04/23/2014

    There is a nice new paper on a scan of a skull of Pliosaurus kevani here: http://palaeo.gly.bris.ac.uk/Benton/reprints/2014rostral.pdf
    This shows a branching system for nerves and blood vessels in the skull linked to pits on the bone surface of the jaws, suggesting some kind of sensory system.

    LeeB.

    Link to this

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