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Simbirskiasaurus, Pervushovisaurus and their very, very strange nostrils: the Cretaceous Ichthyosaur Revolution (part III)

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


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Whimsical and hilarious illustration, incorporating drawings of Malawania (above) and the ophthalmosaurid Acamptonectes (below) by Bob Nicholls.

The event you’ve all been waiting for is here: Simbirskiasaurus and Pervushovisaurus have been resurrected, and we’re all wondering what the hell’s going on with their absurd, complex nostrils. Yes, welcome to another instalment in the long-running, slow-burning series of Tet Zoo articles on Cretaceous ichthyosaur diversity. In previous articles we’ve looked at the 2012 description of the ophthalmosaurid Acamptonectes – one of the first specimens to show that numerous ophthalmosaurid lineages survived across the Jurassic-Cretaceous boundary (Fischer et al. 2012) – and at the surprising discovery of Jurassic-style, Ichthyosaurus-like ichthyosaurs into the Early Cretaceous (Fischer et al. 2013a).

Today we look at another part of Cretaceous ichthyosaur research: it involves the dissolution of an ophthalmosaurid taxon that – supposedly – occurred worldwide during the Cretaceous, persisted (supposedly) for over 50 million years, and contained a very high number of species. The ichthyosaur concerned is Platypterygius. Here’s what I said about the status of Platypterygius in a 2012 Tet Zoo article

“globally distributed, super-speciose Platypterygius … is increasingly being regarded as a ‘taxonomic wastebasket’ that actually contains a higher diversity than previously supposed (e.g., Maxwell & Caldwell 2006, Fischer 2012). In other words, the many species currently included within Platypterygius are almost certainly not all close relatives, and Platypterygius is (I predict) eventually going to be found non-monophyletic. The outcome of such a conclusion will be its dissolution into several discrete ‘genera’ (several authors have already gone down this route, but their efforts to name new genera for the platypterygiine taxa concerned haven’t been widely accepted).”

Life reconstruction of Platypterygius australis by Frank Knight; the species concerned is one of the best known of species included within Platypterygius. It was a large, robust-jawed, long-paddled ophthalmosaurid with numerous stout teeth. Stomach contents confirm a generalised diet of invertebrates and vertebrates.

As hinted at in that quote, the problem with widespread, long-lived, supposedly homogenous genera like Platypterygius is that they become ever larger as people come to assume that new discoveries made elsewhere in the world simply ‘must’ belong to these widespread, long-lived, supposedly homogenous genera. We end up with a situation where distinct animals are referred to said widespread, long-lived, supposedly homogenous genera simply because this becomes the default thing to do, even though the taxon concerned ends up occupying a vast span of time (well beyond that considered normal for other taxa within its group) and a vast geographical range. Ichthyosaurs are particularly affected by this problem: partly, I think, because views on how genera should be distinguished have relied in large part on phenetic notions of overall proportional similarity, not on the recognition of special characters. I previously discussed this issue in terms of how it affects the Lower Jurassic temnodontosaurs.

Because it would be helpful to better understand the relationships between the many species included within Platypterygius, several authors have coded several Platypterygius species within phylogenetic analyses. The results? The species concerned do not form a clade (Druckenmiller & Maxwell 2010, Fischer et al. 2011a, 2014a, Fischer 2012), and the characters previously used to define Platypterygius (these include the presence of large humeral trochanters, quadrangular tooth roots and an extremely reduced extracondylar area on the basioccipital) instead appear to be synapomorphies of Platypterygiinae as a whole (Fischer 2012, Fischer et al. 2012).

Strict consensus cladogram from Fischer et al. (2014). Note that Platypterygius is not monophyletic (nor is Ophthalmosaurus unless we include Acamptonectes).

In order to test how similar controversial platypterygiine species are to those taxa non-controversially regarded as part of Platypterygius, you need, of course, to go and look at them. Given that they’re known from across Europe, Australia, the USA, Argentina, Colombia, Russia and elsewhere, you have you work cut out if you want to see them all. As part of a larger study of ophthalmosaurid diversity and phylogeny, my colleague Valentin Fischer of the Université de Liège (Liège, Belgium) and the Royal Belgian Institute of Natural Sciences (Brussels, Belgium) has recently been spending time in Russia (and elsewhere), looking at specimens that supposedly belong to Platypterygius.

And, as discussed here, his analysis of two of these animals – the Russian taxa Simbirskiasaurus and Pervushovisaurus – shows that good reasons for including them within Platypterygius are lacking: both are distinct, diagnosable taxa that are not especially closely related to the ‘original’ Platypterygius species. The paper concerned, co-authored with Maxim Arkhangelsky, myself, Ilya Stenshin, Gleb Uspensky and Pascal Godefroit, has just been published in Zoological Journal of the Linnean Society (Fischer et al. 2014a). Let’s look at the (fairly obscure and unfamiliar) ichthyosaurs themselves before discussing some of the more interesting of their peculiarities and ramifications.

Simbirskiasaurus is not a nomen dubium

Holotype skull of Simbirskiasaurus birjukovi Ochev and Efimov, 1985 in left lateral view. Image from Fischer et al. (2014a).

Simbirskiasaurus birjukovi was named in 1985 for a large, three-dimensional skull that’s about 70 cm long and consists of everything except the jaw tips and postorbital region. It was found in Barremian sediments on the bank of the Volga River in the Ulyanovsk Region, Russia. Its teeth have elongate, pointed crowns and are typical of ichthyosaurs that belong to the ‘generalist’ feeding guild seen in some other ophthalmosaurids (e.g., Fischer et al. 2011b). Since its initial description, ichthyosaur workers haven’t been kind to Simbirskiasaurus. Maisch & Matzke (2000) retained it as a valid species but argued that it should be subsumed into Platypterygius. McGowan & Motani (2003) also regarded it as similar enough to Platypterygius to be subsumed into its synonymy; they further argued that it lacked diagnostic features of its own and hence should be regarded as a nomen dubium.

Narial region of Simbirskiasaurus (from Fischer et al. 2014a), showing naso-maxillary pillar that divides naris in two.

In fact, Simbirskiasaurus has several weird, unique features of its own (we call unique, diagnostic features autapomorphies). A pillar-like bar of bone splits the nostril opening (properly termed the naris) in two (more on that in a moment) and the junction between the prefrontal and lacrimal bones involves a wavy, interdigitating suture. That last feature is a surprising one for an ophthalmosaurid, since it superficially recalls the condition present in the far more archaic temnodontosaurs (Fischer et al. 2014a). The exact configuration of bones around the nostril opening of Simbirskiasaurus is also unique. Accordingly, Simbirskiasaurus does not deserve to be dismissed as a nomen dubium or regarded as nondescript and undefinable: it is a valid taxon with unique features of its own.

Those who keep up with the ichthyosaur literature (it’s proving increasing hard) might think of another ophthalmosaurid when hearing about Barremian Russia: Sveltonectes, described by Valentin and colleagues in 2011 and notable for its sharply-pointed teeth and tightly packed forelimb bones (Fischer et al. 2011a). Sveltonectes resembles Aegirosaurus and Maiaspondylus in lacking striated crowns and in the weird, semi-divided form of its naris; the most recent runs of the data-set find it to be a platypterygiine (e.g., Fischer et al. 2014a). Anyway, while Sveltonectes is a Barremian ophthalmosaurid, it’s from the upper Barremian, not the lower Barremian like Simbirskiasaurus, so the two weren’t contemporaneous.

Holotype skull of Sveltonectes insolitus in left lateral view; you might be able to see the ventrally projecting finger-like bar of bone that nearly divides the naris. This is not a large ophthalmosaurid: the skull is about 60 cm long. Image by Darren Naish.

Holotype snout of Pervushovisaurus bannovkensis Arkhangelsky, 1998 in left lateral view. Note premaxillary foramen, positioned anteroventral to larger opening that corresponds to posterior portion of naris. Image from Fischer et al. (2014a).

The second animal discussed in our new paper (Fischer et al. 2014a) is Pervushovisaurus bannovkensis, named in 1998 for a complete rostrum found in the middle Cenomanian sediments of the Saratov Region in Russia (a skull roof was found as well, but it’s since become lost). Again, it’s pretty big – the rostrum alone is about 1 m long. This is one of the youngest ichthyosaurs known, and its Cenomanian age means that it’s about 20 million years younger than the European type species for Platypterygius (Pl. platydactylus).

Pervushovisaurus was originally named as a ‘subgenus’ of Platypterygius but was eventually dismissed as a nomen dubium by McGowan & Motani (2003). Again, however, it clearly possesses several unusual features that support its reality as a distinct taxon: it has a suboval bony opening on the side of the premaxilla, anteroventral to the external naris, peculiar bony ridges on the side of the maxilla, and the form of the nasal and splenial bones are also distinctive. Again, the arrangement of bones around its naris is unique: new bone from the nasal bone substantially covers the naris, reducing it to a short, deep, semi-circular opening. On the basis of these features we argue that it warrants recognition as a distinct taxon that was never placed in Platypterygius for any especially good reason (Fischer et al. 2014a).

A brief aside about a non-credible source

By applying a tracing technique called Digital Graphic Segregation to fossils like Longisquama, David Peters thinks that he can see hundreds of bones and other structures not discovered by anyone else. Image composite by David Peters.

There’s something I want to say here which isn’t especially relevant to platypterygiine ophthalmosaurids but which requires comment anyway. You’ll see from the figures reproduced throughout this article that we’ve followed a system of ‘colour coding’ individual bones in order to aid the reader’s interpretation. There’s nothing new about this: many authors, past and present, have used similar systems of colouring bones such that they can be more easily distinguished from the surrounding ones.

Some of you will be familiar with the work of David Peters, a highly prolific and idiosyncratic researcher who promotes his novel interpretations of animal morphology and phylogeny via a website and blog. As I’ve explained before, his observations (and hence hypotheses and claims regarding phylogeny, functional morphology and palaeobiology) cannot be considered reliable, since he relies on a magic eye technique whereby vague and ambiguous structures observed on photos of fossils are interpreted as genuine anatomical features that can be identified with precision and confidence. Peters uses a technique that he calls DGS (= Digital Graphic Segregation) in finding these structures: it’s a technique that involves tinkering with contrast and tones and tracing the perceived edges of structures in Photoshop. As is obvious from the reconstructions of animals he produces, this results in the picking up of all kinds of artefacts and misidentifications, and it has led Peters to make all kinds of incredible and flat-out false claims (that he has discovered the entire back end of Longsiquama, to mention just one example).

No, David, no: this sort of thing is NOT the same as DGS. Skull of the ophthalmosaurine Leninia stellans from the Lower Albian of Russia (from Fischer et al. 2013b), labelled interpreted below. Again - this is NOT DGS.

So, claims that colour-coded images like those you see in this article (and Fischer et al. 2014a, and Valentin’s other papers) represent application of DGS are an outright lie [link here: be warned, it takes you to Pterosaur Heresies]. DGS (or DGS-like) techniques are not used by working palaeontologists because it’s acknowledged in the real world that you can’t reliably identify structures by tracing their outlines on a computer screen. But do working palaeontologists colour-code bones to aid visual representation? Sure, all the time.

Ok, back to the ichthyosaurs…

Those weird, weird nostrils

These Russian ichthyosaurs are interesting for two primary reasons. One is that they’re morphologically weird, specifically with reference to their nostrils. In each nostril of Simbirskiasaurus, a vertical bony pillar descends from the nasal bone to divide the nostril opening into two distinct sections. There’s a small, oval anterior part and (posterior to the pillar) a tall, vertical posterior part. This ‘two-part’ nostril configuration is not unique to Simbirskiasaurus: it’s also present in Platypterygius australis from Australia and probably Pl. sachicarum from Colombia (Fischer et al. 2014a). Furthermore, what seems to be an antecedent condition (where a bony process descends from the nasal to reduce the depth of the naris at mid-length) is present in Ophthalmosaurus, Acamptonectes, Cryopterygius and Pl. americanus at least, with Sveltonectes possessing a ventrally descending bar that very nearly divides the naris in two.

Pervushovisaurus lacks a vertical bar, but its peculiar narial condition (a small, elongate foramen is present anteriorly, and a deep, narrow, subcircular naris is present posteriorly) seems to represent the ‘end point’ of a trend whereby the middle part of the naris was filled in by bone. The anterior foramen can therefore be regarded as a significantly reduced remnant of the original, anterior part of the naris (Fischer et al. 2014a).

A hypothesis of nostril evolution in ophthalmosaurids, from Fischer et al. (2014a). The nostrils start out as pseudo-comma-shaped and then become divided and eventually bipartate.

Exactly what’s going on here is unknown. Why evolve these weirdly shaped nostrils in the first place, why then go on to evolve bipartate nostrils of the sort seen in Simbirskiasaurus, and why end up with a condition whereby the anterior part of the naris is represented only by foramina, as seen in Pervushovisaurus? We don’t know, of course, and further study would be needed to work out what’s going on internally and what any of this might mean as goes breathing, airflow or olfaction. Asymmetry in ichthyosaur nostrils has been remarked on several times in the past, and teardrop-shaped, comma-shaped and kidney-shaped nostrils are present in assorted ichthyosaurs, including leptonectids, Stenopterygius and ophthalmosaurids.

Diagrammatic representation of the flow-through nasal system hypothesised for plesiosaurs by Cruickshank et al. (1991). Was the same system present in ichthyosaurs? Illustration by Robin Carter.

Maybe different parts of the nostrils had different functions, making division of this sort advantageous. It’s been suggested that ichthyosaurs had a flow-through nasal system like that also hypothesised for plesiosaurs (Cruickshank et al. 1991): supposedly, water entered the internal nostrils on the palate, flowed through the nasal chamber, and left the head via the external nostrils. Bipartate nostrils could mean that one section specifically functioned to release water while the other was used for breathing. Or maybe it was simply advantageous to roof over the anterior part of the naris? Or maybe the ichthyosaur nostril was always partially roofed by a valve or flap of some sort, and platypterygiines simply took to ossifying this flap?

Platypterygius: quo vadis?

Excellent skull of Platypterygius australis, from Wade (1990). This is one of the most thoroughly known of species included within Platypterygius, but does this mean that the name Platypterygius should best be associated with it, or with the type species (the less well known Pl. platydactylus)? Opinions differ.

The other big-picture thing about these ichthyosaurs concerns their implications for the fate of the name Platypterygius. The Platypterygius species do not group together in our analysis (nor in other versions of the same dataset: Fischer et al. 2012, 2013a, b; see also Druckenmiller & Maxwell 2010): Pl. hercynicus from Germany is some distance from Pl. australis (an extremely well known, well described species), with Caypullisaurus and Athabascasaurus grouping closer to Pl. australis than to Pl. hercynicus. The type species of PlatypterygiusPl. platydactylus – is of uncertain phylogenetic position.

As mentioned in the paper, we’re still not sure what to do about this and there are competing opinions. Our preferred opinion (Fischer et al. 2014a) is to restrict the name Platypterygius to Pl. platydactylus and those species most closely related to it. However, this is not ideal, creates some other problems and – as we’ve found through consultation with colleagues – is unlikely to be accepted by everyone who works on ophthalmosaurids. For now, things are undecided and more work is needed.

Graph from Fischer et al. (2011b) - now substantially out of date! - showing how then-new discoveries had substantially increased the number of reported Cretaceous ichthyosaur taxa. The Cretaceous starts with 'Ber', the Berriasian.

And that where we’ll end for now. Since the description of the new platypterygiine Sisteronia seeleyi and the resurrection of Cetarthrosaurus walkeri – both from the Cambridge Greensand of England (Fischer et al. 2014b) – we’re now in a position whereby Cretaceous ichthyosaur diversity has surpassed that of the Jurassic. The old idea that ichthyosaurs had their heyday in the Late Triassic or Early Jurassic and only had the most tenuous, low-diversity existence in Cretaceous times is now officially dead. Actually, they were thriving at reasonably high diversity from Berriasian times all the way until the Cenomanian. Notably, however, the Cretaceous ichthyosaurs are more ‘samey’ than those of the Jurassic – that is, they belong predominantly to two rather homogenous evolutionary radiations (Ophthalmosaurinae and Platypterygiinae). Regardless, these are (here comes that clichéd phrase again!) very interesting times to be interested in ichthyosaurs…

More from the world of ophthalmosaurid ichthyosaurs some time soon!

For previous Tet Zoo articles on ichthyosaurs, see…

Refs – -

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

Druckenmiller, P. S. & Maxwell, E. E. 2010. A new Lower Cretaceous (lower Albian) ichthyosaur genus from the Clearwater Formation, Alberta, Canada. Canadian Journal of Earth Sciences 47, 1037-1053.

Fischer V. 2012. New data on the ichthyosaur Platypterygius hercynicus and its implications for the validity of the genus. Acta Palaeontologica Polonica 57, 123-134.

- ., Appleby, R. M., Naish, D., Liston, J., Riding, J. B., Brindley, S. & Godefroit, P. 2013a. A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs. Biology Letters 9 (4) 20130021

- ., Arkangelsky, M. S., Naish, D., Stenshin, I. M., Uspensky, G. N. & & Godefroit, P. 2014a. Simbirskiasaurus and Pervushovisaurus reassessed: implications for the taxonomy and cranial osteology of Cretaceous platypterygiine ichthyosaurs. Zoological Journal of the Linnean Society 171, 822-841.

- ., Arkhangelsky, M. S., Uspensky, G. N., Stenshin, I. M. & Godefroit. 2013b. A new Lower Cretaceous ichthyosaur from Russia reveals skull shape conservatism within Ophthalmosaurinae. Geological Magazine doi: 10.1017/S0016756812000994

- ., Bardet, N., Guiomar, M. & Godefroit, P. 2014b. High diversity in Cretaceous ichthyosaurs from Europe prior to their extinction. PLoS ONE 9(1): e84709. doi:10.1371/journal.pone.0084709

- ., Clément, A., Guiomar, M., & Godefroit, P. 2011b. The first definite record of a Valanginian ichthyosaur and its implication for the evolution of post-Liassic Ichthyosauria. Cretaceous Research, 32, 155-163.

- ., Maisch, M. W., Naish, D., Kosma, R., Liston, J., Joger, U., Krüger, F. J., Pérez, J. P., Tainsh, J. & Appleby, R. M. 2012. New ophthalmosaurid ichthyosaurs from the European Lower Cretaceous demonstrate extensive ichthyosaur survival across the Jurassic-Cretaceous boundary. PLoS ONE 7(1): e29234. doi:10.1371/journal.pone.0029234

- ., Masure, E., Arkhangelsky, M. S. & Godefroit, P. 2011a. A new Barremian (Early Cretaceous) ichthyosaur from western Russia. Journal of Vertebrate Paleontology 31, 1010-1025.

Maisch, M. W. & Matzke, A. T. 2000. The Ichthyosauria. Stuttgarter Beiträge zur Naturkunde Serie B (Geologie und Paläontologie) 298, 1-159.

Maxwell, E. E. & Caldwell, M. W. 2006. Evidence for a second species of the ichthyosaur Platypterygius in North America: a new record from the Loon River Formation (Lower Cretaceous) of northwestern Canada. Canadian Journal of Earth Sciences 43, 1291-1295.

McGowan, C. & Motani, R. 2003. Handbook of Paleoherpetology Part 8 Ichthyopterygia. Verlag Dr. Friedrich Pfeil (München).

Wade, M. 1990. A review of the Australian Cretaceous longipinnate ichthyosaur Platypterygius, (Ichthyosauria, Ichthyopterygia). Memoirs of the Queensland Museum 28, 115-137.

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. Kenshin 3:46 pm 07/28/2014

    It’s amazing to me that anyone could seriously suggest that using a color coded photo as a visual aid in a paper is the same as using photoshop filters of pictures to “analyze” 3d structures. As an aside, if DGS actually consists of overlaying semiopaque layers on photos of fossils…well, that’s pretty embarassing.

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  2. 2. Halbred 3:59 pm 07/28/2014

    So were ichthyosaurs still present at the bitter end of the Mesozoic?

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  3. 3. vdinets 4:00 pm 07/28/2014

    It is perhaps worth noting that Simbirsk is the old name of the city of Ulyanovsk on Volga River. It was renamed in the Soviet times because it happened to be the birthplace of Vladimir Ulyanov, better known under his nom de guerre, Lenin (hence Leninia).

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  4. 4. Yodelling Cyclist 5:21 pm 07/28/2014

    So what causes the Cenomanian extinction?

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  5. 5. Yodelling Cyclist 5:33 pm 07/28/2014

    ….and was the Bathonian drop in diversity real or another taphonomic artifact?

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  6. 6. naishd 5:48 pm 07/28/2014

    Thanks for comments.

    Kenshin (comment # 1): you’re dead right!

    Halbred (comment # 2): the very youngest ichthyosaurs we know of are from the upper Cenomanian of Germany, so it doesn’t seem that they persisted into the latest part of the Cretaceous – apparently, they were part of the ‘Cenomanian reorganisation’ that affected many marine groups of the time. There is, incidentally, an alleged Santonian ichthyosaur, but there are doubts about its age.

    More responses later…

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  7. 7. Allen Hazen 7:45 pm 07/28/2014

    In the last few years there have been suggestions that some Mosasaurs were more (more nearly?) Thunniform than previously thought: evidence of bilobed tail, fat torso allowing the tail to be wagged without major bending of the fore-body. In other words: more like the classic Ichthyosaur in shape! Is it possible — I know this sort of thing is very VERY hard to establish — that the ‘Cenomanian reorganization’ was in part a matter of competitive replacement of Ichthyosaurs by advanced Mosasaurs?

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  8. 8. Heteromeles 10:48 pm 07/28/2014

    Is that a typo occupying “a fast span of time?” Or is that ichthyosaurs revealing their secret superpower?

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  9. 9. naishd 6:12 am 07/29/2014

    The idea of mosasaur-ichthyosaur competition has been mentioned a few times. Given that ichthyosaurs disappear at a time of major marine ‘reorganisation’, I think there are already good reasons for blaming ichthyosaur extinction on events unrelated to mosasaur appearance.

    In any case, the mosasaurs present in the Cenomanian were small, amphibious, reef-dwelling forms, not pelagic giants like those of the latest Cretaceous. In fact, paddle-bearing, big-bodied, fully marine mosasaurs don’t seem to have existed until the Coniacian. So, no good reason to think that the last ophthalmosaurids (which were big and pelagic) were competing with, or being replaced by, mosasaurs.

    And, yes, “fast span of time” was a dumb typo.

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  10. 10. LeeB 1 6:59 am 07/29/2014

    Yes it looks more like the extinction of the Ichthyosaurs being due to environmental and/or biotic conditions in the Turonian; then when things went back to normal later there was an open environmental niche which the Mosasaurs and Polycotylids expanded into.

    Rather like the extinction of Marine Reptiles at the end of the Cretaceous leaving empty ecological space which the whales and seals later expanded into.

    It would be interesting to know if the extinction of Pliosaurs during the Turonian was part of the same event; also if the flourishing of advanced Ichthyosaurs in the lower Cretaceous led to the competitive extinction of the Metriorhynchids.

    LeeB.

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  11. 11. DavidMarjanovic 7:24 am 07/29/2014

    So were ichthyosaurs still present at the bitter end of the Mesozoic?

    No; the Cenomanian is the first stage of the Late Cretaceous.

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  12. 12. Gigantala 8:02 am 07/29/2014

    “It would be interesting to know if the extinction of Pliosaurs during the Turonian was part of the same event; also if the flourishing of advanced Ichthyosaurs in the lower Cretaceous led to the competitive extinction of the Metriorhynchids.”

    - Pliosaurs seem to have occupied a similar ecological niche to that of ichthyosaurs (fast, fully aquatic pursuit piscivores with long jaws; probably like modern dolphins), if generally tending towards “bulkier” roles, so yes, whatever killed ichthyosaurs probably also offed pliosaurs. Both groups were probably replaced in the post-Turonian Cretaceous by polycotylids, which have been compared to both clades for years anyways.

    - Interesting. Metriorhynchoids defenitely seem to have occupied similar ecological niches to those of ichthyosaurs and pliosaurs, so niche partitioning between these groups is definitely something to take into consideration. However, since all these clades co-existed for at least 38 million years, I think it’s unlikely, and frankly given the presence of metriorhynchoids in the Valanginian I think it’s simply a matter of time until we find more.

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  13. 13. naishd 8:15 am 07/29/2014

    Some hot news on late-surviving metriorhynchids is due to be announced soonish…

    On the broader issue of ‘competition’ and the ‘overlapping’ of niches, I note that palaeontologists have often assumed that, if group x is occupying a particular place in an ecosystem, group y ‘can’t’ exist as well. This might be true/partially true in cases, but it certainly isn’t in others. In modern oceanic ecosystems, look how many big-bodied predators can share the same area: there are marine environments where predatory dolphins (including false killer whales, pilot whales, orcas and others) co-exist with squaliform, hexanchiform, carchariniform and lamniform sharks as well as assorted billfish and barracudas. These species co-exist by using different parts of the water column, by moving around on a seasonal basis, by exploiting different sorts of prey and different microhabitats etc.

    In view of this, the idea that one group (neoselachian sharks, or mosasaurs, for example) appears and ‘takes over’ a niche already occupied by another group is frequently a ‘just so’ story, devised in an effort to explain an otherwise mysterious pattern of decline and replacement. We should be very sceptical of these sorts of ideas.

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  14. 14. Yodelling Cyclist 8:55 am 07/29/2014

    Late surviving metriorhynchids? Don’t tell me, let me guess: you found the Monongahela carcass.

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  15. 15. naishd 9:42 am 07/29/2014

    It’s also been difficult to make much sense of the Monongahela monster (and it was pretty clearly a hoax in any case) – but it was described as serpentine, over 30 m long, and with paired blowholes, ‘separate’ jawbones and recuved teeth. The Gambo carcass and the creature allegedly seen from the U28 in 1915 have also been posited as metriorhynchids in the cryptozoological literature.

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  16. 16. satyrus 10:31 am 07/29/2014

    With the shape of the nares is there a good handle on the variation within species or is there typically only 1 or 2 samples per species?

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  17. 17. Heteromeles 11:07 am 07/29/2014

    Incidentally (if you believe everything you read in Wikipedia), the environmental event at the boundary of the Cenomanian and Turonian is the Cenomanian-Turonian Boundary Event with a strikingly original name. It was a major anoxic event in the ocean, caused as usual by well-we-don’t-really-know-yet-but-we’ve-got-hypotheses. Sorry, I’ve seen that explanation so much it really deserves a pithy acronym, if not a rude one. Anyway, there was a major anoxic event, rudist reefs seem to have been affected, and some major groups, including the ichthyosaurs, disappeared.

    I’m not quite sure if it was a full-scale Reef Gap, which is what you get when the ocean becomes sufficiently carbonated and/or acidic that large reefs fall apart and don’t reform for a while (thereby forming a reef gap in the geologic record), but from what little I’ve found on the subject with a few minutes’ googling, it looks like one.

    If you’ve never heard of reef gaps, I’d suggest reading up on them. All the carbon we’re dumping into the ocean is likely to induce a reef gap in the next century or so. Since reefs are extremely well preserved in the geologic record, compared with, oh, diverse montane ecosystems, reef species are generally over-represented in the fossil record, and the massive loss of reef species is one widely used marker in determining whether an extinction event happened.

    So if you’re wondering what could have taken out the ichthyosaurs and pliosaurs, I’d suggest that food web disruption is more likely than is competition with other large-bodied predators.

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  18. 18. Yodelling Cyclist 11:27 am 07/29/2014

    Indulging in silliness: the Monongahela carcass was also supposed to have recurred teeth and one lung longer than the other. It all sounded rather like a hoax snake to me. I wondered about lying sailors mosasaurs or some supergiant palaeophsid.

    I mean we keep saying the guys on the Valhalla saw something got bored and included a joke in their work.

    Link to this
  19. 19. Yodelling Cyclist 11:28 am 07/29/2014

    The strike tag doesn’t want to cancel itself!

    Link to this
  20. 20. naishd 1:49 pm 07/29/2014

    Yod: was all that underlining deliberate?

    Link to this
  21. 21. Yodelling Cyclist 2:33 pm 07/29/2014

    Not all of it at all. The only words intended to be struck through (for comic effect) were “hoax”, “lying sailors”, “got bored and included a joke in their work”.

    Link to this
  22. 22. Mark Young 3:44 pm 07/29/2014

    I never realised metrios had been posited for ‘sea monster’ sightings/carcasses! I thought they were too poorly known for that kind of attention. The poor, poor deluded fools.
    Just out of curiosity, what is the Gambo carcass and the U28 sighting?

    Oh, and this external nares morphology in ichthyosaurs is very interesting. I wasn’t aware of it before, but I’m curious to learn more.

    Link to this
  23. 23. naishd 5:55 pm 07/29/2014

    Mark (comment # 22): metriorhynchids feature quite heavily in the cryptozoological literature, and have done since the 1960s at least. Heuvelmans – in his classic 1968 book In the Wake of the Sea-Serpents – suggested that the ‘marine saurian’ (a gigantic, flippered, crocodile-shaped sea monster he endorsed) might be a metriorhynchid. One of his key cases was the U28 incident of 1915: Baron Von Forstner claimed that he watched a giant, crocodile-shaped sea monster get blasted skyward when a sinking ship exploded. The case has been the source of debate for years and recent research has shown, not only that it almost certainly never happened, but also that the metriorhynchid-like monster was not imagined as metriorhynchid-like initially – the original drawing of it makes it look like a gigantic baby Nile crocodile. See Mike Dash’s article here if you’re really interested.

    The Gambo case concerns a metriorhynchid-like or pliosaur-like monster carcass, supposedly found on Bungalow Beach, Gambia, in 1983. Cryptozoologist Karl Shuker has written several articles on the carcass, and I provided a summary of the case in this Tet Zoo ver 1 article. He vetted the various possible identifications, and metriorhynchids were considered among the ‘best fits’.

    Link to this
  24. 24. naishd 6:15 pm 07/29/2014

    satyrus’s comment # 16 raised a good point: “is there a good handle on the variation within species or is there typically only 1 or 2 samples per species?”. Several ichthyosaur taxa are known from numerous specimens (e.g., certain species of Ichthyosaurus, Leptonectes, Stenopterygius and so on), and some platypterygiines are known from at least a few good specimens (e.g., Platypterygius australis). And they do show homogeneity in the form of the naris within species (though left-right asymmetry in size and form is sometimes present: it doesn’t seem to be part of the ‘bipartate story’ though).

    Link to this
  25. 25. LeeB 1 6:30 pm 07/29/2014

    A late surviving metriorhynchid is interesting.
    If it is late enough it might suggest that they died out in the Cenomanian-Turonian event as well.
    There are a number of early Cretaceous marine reptiles turning up in Colombia recently; does any one know if they have found Metriorhynchids there (yet)?

    LeeB.

    Link to this
  26. 26. Yodelling Cyclist 7:03 pm 07/29/2014

    We should move away from the crypto stuff soon – but I’m intrigued, what’s the support for the statement “that it almost certainly never happened”? I mean, yeah, the drawing looks like a stuffed baby croc, but readers of this blog will be familiar with the possibility that an artist may have over-borrowed from a familiar subject rather than using the imagination.

    Link to this
  27. 27. Allen Hazen 11:30 pm 07/29/2014

    Darren (#9)– Thanks for reply! I had only the vaguest sense of just when in the Cretaceous Mosasaurs reached the big time.

    (So: are there ANY generally accepted examples in the fossil record of competitive replacement of one taxon by another? Van Valen’s (I think) account of the last Multituberculates falling to a one-two punch from early Primates (Plesiadapids?) and then Rodents seemed convincing when I read it, but I don’t know what the current thinking is. And Prothero’s recent book (Rhinoceros Giants) on Indricotheres has an interesting speculation that Gomphotheres and Deinotheres may had been implicated in their extinction: Proboscideans can make major changes in the landscape, knocking down enough trees to convert forest to savannah, and this would be bad for treetop browsers!)

    Link to this
  28. 28. Therizinosaurus 5:40 am 07/30/2014

    I know little about ichthyosaurs, but given that genera are only subjectively diagnostic, is there a good reason to prefer a Platypterygius of several species to a Platypterygiinae of several genera? If not, then where’s the psittacosaur revolution with its several new genera?

    Link to this
  29. 29. naishd 5:58 am 07/30/2014

    Therizinosaurus (comment # 28): I think about this every time I look at the phylogenies. You’re right that it’s subjective: if you look at the phylogeny above, we could simply subsume Caypullisaurus and Athabascasaurus into an expanded version of Platypterygius, and thus retain a monophyletic Platypterygius.

    However, this doesn’t jive with what we understand of ichthyosaur diversity – it’s (so far as I know) universally agreed that Caypullisaurus and Athabascasaurus are morphologically pretty divergent from species classically included within Platypterygius (Caypullisaurus, for example, seemingly has a reduced dentition and thus is not ‘Platypterygius like’), so lumping all of these taxa together would create a genus that houses substantially more disparity than other ‘genera’ (those ichthyosaur ‘genera’ that do contain this much diversity are suspected, or known, to be non-monophyletic and will get broken up in time). Furthermore, the view of a super-speciose Platypterygius means that we have this one genus persisting for more than 30 million years (and perhaps as much as c. 60 million years).. theoretically that’s not impossible but it’s above and beyond what we see in other ichthyosaur ‘genera’. So, morphological disparity, the shape of the cladogram, and the implied longevity of clades makes the view of distinct platypterygiine ‘genera’ more in keeping with the rest of ichthyosaur diversity and taxonomy. I do, totally, agree with the point about subjectivity as goes these opinions, but super-speciose, super-long-lived ‘genera’ (like the traditional versions of Iguanodon and Megalosaurus) don’t enhance our appreciation of patterns in the fossil record – they stifle them.

    Oh, and — there’s a psittacosaur revolution??

    Link to this
  30. 30. Mark Young 7:59 am 07/30/2014

    Darren: I had no idea metriorhynchids were frequently mentioned in the cryptozoological literature. If any Mesozoic marine reptile group could have survived the K-P boundary it would be mosasaurids.
    Back to ichthyosaurs, do you know what’s happening with them in the Cenomanian? Are they still as diverse as in the Albian, or were they doing through a ‘rough spot’ like dinosaurs were during the Maastrichtian (re Steve’s new paper)?

    Link to this
  31. 31. Gigantala 9:41 am 07/30/2014

    I find it curious how often metriorhynchoids were brought up, when the relatively morphologicall similar and much more recently lived champsosaurs could be a valid alternative.

    Link to this
  32. 32. DavidMarjanovic 9:46 am 07/30/2014

    I forgot to ask: you say the pillar in the naris consists of processes from the nasal and the maxilla, meaning that the maxilla wraps around behind the premaxilla. It’s not clear to me if you’ve actually seen the snout from the inside or if there could be a septomaxilla involved – or do ichthyosaurs just not have septomaxillae?

    Baron Von Forstner

    Lowercase “von”.

    So: are there ANY generally accepted examples in the fossil record of competitive replacement of one taxon by another?

    Probably not. Basically, for much of the 20th century competition was taken for granted, so almost every extinction was attributed to competition, then in the late 80s and 90s people pointed out that, in more and more of those cases, there’s not enough evidence to tell that that’s the most parsimonious hypothesis, and most of the cases haven’t been investigated in detail. What happened at and around the Jurassic/Cretaceous boundary, for example, is poorly understood across all of paleontology and geology; some have postulated a catastrophic extinction event, others have postulated two, others think nothing much happened at all…

    Link to this
  33. 33. DavidMarjanovic 9:50 am 07/30/2014

    Oh, and — there’s a psittacosaur revolution??

    The difference between Platypterygius and Psittacosaurus is that the former has been found to be paraphyletic with respect to other accepted genera. Since we’ve stopped liking paraphyletic genera, the options are to either lump all the descendants of Pl. into Pl. or to split it (more or less?) all the way down to the type species. That’s where the arguments about how diverse and long-lived we expect a genus to be have a chance to get in.

    Psittacosaurus is universally thought to be monophyletic. There’s no sociological trigger for splitting it.

    Link to this
  34. 34. naishd 11:23 am 07/30/2014

    Thanks for continuing comments…

    David (comment # 32) says “I forgot to ask: you say the pillar in the naris consists of processes from the nasal and the maxilla, meaning that the maxilla wraps around behind the premaxilla. It’s not clear to me if you’ve actually seen the snout from the inside or if there could be a septomaxilla involved – or do ichthyosaurs just not have septomaxillae?”

    Ichthyosaurs display a pattern whereby the posterior processes of the premaxillae extend posteriorly to overlap the nasals and maxillae; in the same way, the nasals extensively overlap the frontals. In other words, I wouldn’t say that the maxilla ‘wraps around behind’ the premaxilla – rather, that the premaxilla overlaps the lateral face of the maxilla, as is seen throughout these animals.

    Could a septomaxilla be involved here? Septomaxillae have been identified in platypterygiines (Romer described one for Pl. americanus and Valentin has figured one in Pl. hercynicus) and other thunnosaurians; they are suboval or ‘leaf-shaped’ structures that emerge into the naris from the edge of the lacrimal or ventral edge of the premaxilla. They aren’t smack in the middle of the naris, as is the naso-maxillary pillar. Furthermore, the naso-maxillary pillar does seem to be a hypertrophied example of the condition present in other ophthalmosaurids, and which seemingly involves the edges of the nasal and maxilla, not a separate element. Having said all that, confirmation via CT-scanning would be nice…

    Link to this
  35. 35. Yodelling Cyclist 2:47 pm 07/30/2014

    How big are the objects that need CT scanning? I have a colleague who is doing some development work with a scanner she has – but it’s a low volume instrument.

    Link to this
  36. 36. Halbred 7:37 pm 07/30/2014

    To echo what David said about psittacosaurs, not only is there no reason to think Psittacosaurus is anything but monophyletic, it’s likely over-split. Recently, a purported second psittacosaur genus (“Hongshanosaurus”) was sank into Psittacosaurus, and the three “species” of Yixian psittacosaurs were synonymized as P. lujiatunensis.

    If any psittacosaur deserves its own genus, I’d nominate P. sibiricus, which is significantly larger than its cousins and has more horns than most ceratopsids. But nobody has seriously suggested spinning it off.

    Link to this
  37. 37. DavidMarjanovic 4:29 pm 07/31/2014

    OK, not a septomaxilla, then. :-)

    I wanted to mention Hongshanosaurus, but forgot at the last moment; thanks for bringing it up!

    Link to this
  38. 38. Mark Evans 6:06 pm 07/31/2014

    On the plesiosaur side of things, the flow-through nasal system of Cruickshank et al. (1991) was based on the neotype of “Rhomaleosaurus” megacephalus in which the external nares are posterior to the internal nares and grooves on the palate seem to lead into the internal nares. The above illustration by Robin Carter is based on Andrews’ (1910) reconstruction of the cryptoclidid Muraenosaurus platyclis. In the holotype the external nares are actually just anterior to the internal nares, so it’s initially less convincing, although the narial duct seems to be inclined posterodorsally. There seems to have been something going on, but not perhaps a straight-through flow system. No plesiosaurian has divided external nares, but the cryptoclidid Vinialesaurus seems to have two equally-sized internal nares on each side. A possible alternative explanation is that the anterior opening is an enlarged “vomeronasal” foramen – other cryptoclidids have a pair of foramina anterior to the internal nares, and in some the foramina approach the naris in size.

    Link to this
  39. 39. Zimices 7:37 pm 07/31/2014

    To LeeB 1 (#25): Yes, in central Colombia (specially near to the village of Villa de Leyva) have been found several marine reptiles, but nothing like a methriorhynchid yet, although there is a number of fossils still undescribed.

    Some more information is in this article (in Spanish): http://www.sumamente.co/articles/detail/villa-de-leyva-potencia-fosilifera

    Link to this
  40. 40. LeeB 1 10:52 pm 07/31/2014

    Zimices, thanks for that, it is a nice article.
    It looks like there should be some interesting papers on Colombian marine reptiles in future.
    As well as the early Cretaceous Colombia also has mosasaur fossils, so it does seem one of the better localities worldwide for studying Cretaceous marine vertebrates.

    LeeB.

    Link to this
  41. 41. LeeB 1 11:57 pm 07/31/2014

    I just found this: file:///C:/Users/user/Downloads/Tesetoda.pdf

    It is an online thesis by Montefeltro on the phylogenetic revision of Mesoeucrocodylia and on page 6 it shows a photograph of a Cricosaurus skull from Colombia.
    It references an Ameghiniana abstract which mentions there is also postcranial material of the specimen, so I guess we will be hearing more about Colombian Metriorhynchids in future.
    Given the age of the strata with marine reptile fossils in Colombia perhaps we will learn just when the group became extinct.

    LeeB.

    Link to this
  42. 42. LeeB 1 12:04 am 08/1/2014

    Sorry that link didn’t work; try this.

    LeeB.

    Link to this
  43. 43. DavidMarjanovic 7:26 am 08/1/2014

    A possible alternative explanation is that the anterior opening is an enlarged “vomeronasal” foramen – other cryptoclidids have a pair of foramina anterior to the internal nares, and in some the foramina approach the naris in size.

    Now it gets interesting!!!

    Link to this
  44. 44. naishd 7:55 am 08/1/2014

    So many good ideas and observations have been made about the ‘flow-through nasal system’ (many of them by Mark!) that a published discussion really is warranted at some point – the subject keeps coming up in the Tet Zoo comments, yet we don’t see these ideas reflected in the literature. Of course, Marie-Celine Buchy and others have published their own interpretations of what might be going on here…

    Link to this
  45. 45. Heteromeles 9:53 am 08/1/2014

    Hmmm. I wonder if there’s some way to use 3-D printing and some sort of flow tank to test the various nasal architectures. I assume that the problem with this approach is what to do about the soft tissue reconstruction around the bones. Still, the technology is probably there, or close to there.

    Link to this
  46. 46. Zimices 8:40 pm 08/1/2014

    LeeB 1: Thank a lot for the thesis! very interesting, I didn’t known anything about it. Certainly many new findings here are in process of publication – the latest is precissely the mosasaur Eonatator coellensis, form Late Cretaceous – so we can expect even more new species.

    On another hand: This skull of Platypterygius sachicarum seems have the separation of the nostrils mentioned in the article.

    Link to this
  47. 47. LeeB 1 1:55 am 08/2/2014

    Thanks Zimices, thats a very nice skull and you are right about the nostrils.
    Another area where new specimens are coming in fast is Svalbard; Janusaurus lundi has just been named.
    Interestingly Athabascasaurus shows as an Ophthalmosaur in their cladogram, as a sister to the Svalbard ichthyosaurs which form a polytomy.
    Now we need a cladogram with multiple species of Ophthalmosaurus as well as multiple species of Platypterygius; it would be interesting to see how the South American species of Ophthalmosaurus compare to the European and North American species.

    LeeB.

    Link to this
  48. 48. Mark Young 7:15 am 08/2/2014

    @Lee (#41) Yes, there is a Valanginian metriorhynchid from Colombia. I’m not sure what stage of publication the paper is at. Felipe OK’ed citing his SVP abstract in my Annales de Paleontologie paper.

    @Darren (#44) disagree with Marie at your own peril… :-) But, I agree with her paper.

    @Darren, I take it no news about the Cenomanian ichthyosaur question I asked about?

    @Lee (#47) Aubrey was kind enough to let me see her Svalbard photographs earlier this year, and I was excited by what I saw there. The evolution of ophthalmosaurids is very interesting, and hypothesis of a Boreal-clade… Well, it has some interesting implications.

    (Oh, late surviving metrios. I think not anymore, can’t say any more than that, but something exciting is happening in the EK, re: my paper with Darren and another I’m helping out on.)

    Link to this
  49. 49. DavidMarjanovic 8:27 am 08/2/2014

    Felipe OK’ed citing his SVP abstract in my Annales de Paleontologie paper.

    Once the conference is over, SVP abstracts are published in open access here, though I see that last year’s still isn’t up. They can absolutely be cited, and pretty often are.

    Link to this
  50. 50. naishd 8:46 am 08/2/2014

    Sorry, Mark – it’s often difficult to keep up with comments… Cenomanian ophthalmosaurid diversity is reasonably high, with five taxa present in the early Cenomanian (an indeterminate ophthalmosaurine, two species of Platypterygius s. l., Sisteronia and Cetarthrosaurus), though the last of those is most likely reworked from Albian strata (see Fischer et al. 2014b – cited above). However, how many of these persisted to the end of the Cenomanian is less certain: only Platypterygius s. l. is known from Upper Cenomanian strata. Speak to Valentin if you need more detail!

    And, yes, the new paper by Aubrey Roberts and colleagues is very neat. I like the phylogeny they recover (Malawania as sister to Ichthyosaurus, a platypterygiine-ophthalmosaurine divergence, a non-monophyletic Platypterygius), and the hypothesis of a boreal clade of ophthalmosaurines is certainly very interesting. I just submitted (with Ben Moon) another ophthalmosaurid-focused ichthyosaur manuscript two days ago…

    Link to this
  51. 51. Mark Young 11:38 am 08/2/2014

    @David (#49), I know. I just took the courtesy to ask if he was OK with me referring to a specimen in a publication before he formally published on it.

    @Darren (#50), seems like there are loads of ophthalmosaurid papers getting submitted these days! :-)

    Link to this
  52. 52. ValFisch 11:36 am 08/3/2014

    Dear all,

    Like Darren, I am amazed by the quality of the comments, observations and discussions!

    @LeeB #47 — There is such cladogram, incorporating most species of “Platypterygius” (including P. platydactylus, the type species) but it can only be found in my PhD thesis; I haven’t published it, notably because data from privately-held specimens are crucial. If nothing change within a year or two, regarding these magnificent specimens, I will make my PhD thesis open access.
    Yet, the take home message is similar to that of our paper with Darren: Platypterygius is a wastebasket taxon hiding a large diversity of ophthalmosaurids.

    @ Several commenters on ichthyosaur extinction: I have just finished writing a 20.000 words paper on the subject; it will be submitted around september!

    Link to this
  53. 53. LeeB 1 7:25 pm 08/3/2014

    Well if you are going to comment about marine reptiles on a thread that has Darren Naish, Mark Young and Valentin Fischer on it you really need to up your game ;-) .
    Glad to hear that you will eventually either open your thesis or publish on those specimens if they can be got into a museum; the colossal form of Ichthyosaur sounds very interesting.

    The paper on ichthyosaur extinction sounds like something to look forward to as well; the last few years have really been a good time for people with an interest in marine reptiles and it looks like this is going to continue into the future. Excellent.

    Link to this

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