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Can’t get me enough of that sweet, sweet Temnodontosaurus

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


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Temnodontosaurus platyodon skull (and vertebrae and forefin) at the Philpotts Museum, Lyme Regis. This specimen was discovered in 2008 by Mike Harrison and represents an animal about 7 m long. Photo by Darren Naish.

One of my favourite ichthyosaurs is the generally large, archaic, long-snouted Temnodontosaurus, and if you have an especially good memory you’ll recall it being mentioned here and there on Tet Zoo over the years (see links below). We have lots of Temnodontosaurus fossils here in southern England and I feel pretty familiar with the ‘genus’ (cough cough) – I haven’t published anything on it yet but work is in progress. Here are assorted words.

Temnodontosaurus is among the most archaic of the parvipelvian ichthyosaurs – Parvipelvia being the clade whose members are united by the presence of a strongly reduced pelvic girdle, a tibia and fibula that are about similar in form and position with respect to the end of the femur, and other characters (Maisch & Matzke 2000). Within Parvipelvia, phylogenetic studies have generally found Temnodontosaurus to be close to (but outside) the clade that includes the superficially billfish-like leptonectids and the most familiar parvipelvians of the Jurassic and Cretaceous, the thunnosaurians (Maisch & Matzke 2000, McGowan & Motani 2003). Sander (2000) used the name Neoichthyosauria for this Temnodontosaurus + leptonectid + thunnosaurian clade. However, a novel result was recovered in the phylogeny we recently published as part of our study of the Iraqi parvipelvian Malawania: we found Temnodontosaurus and leptonectids to group together (Fischer et al. 2013). As I said last time, this is “an intuitively pleasing discovery, given the similar gestalt of these often big, often especially long-snouted, long-flippered ichthyosaurs”.

Select Temnodontosaurus species, roughly to scale, from Clark (1989). Yeah, they don’t much look alike (though note that T. longirostris has proved to be based on specimens of Eurhinosaurus and Leptonectes).

Characterising Temnodontosaurus is difficult. For now, the name is used for a selection of Lower Jurassic neoichthyosaurians from England, France and Germany, all of which combine a distinctive humerus (it’s proportionally short, distally wide and has a waisted shaft) with a long body and tail where more than 80 vertebrae are present anterior to the tailbend. However, better features that unite them have yet to be published and my strong suspicion (and that of several other ichthyosaur workers) is that they’re grouped together because they’re of about the same ‘grade’, not because they share derived characters.

In general, Temnodontosaurus specimens are large, usually exceeding 6 m and sometimes exceeding 12 m. Their orbits are proportionally smaller than those of leptonectids and most thunnosaurians but are still literally enormous, in cases exceeding an incredible 26 cm in width. Substantial variation in temnodontosaur skull and tooth shape suggests diverse feeding adaptations within the group. A short-snouted, orca-like skull shape is present in Temnodontosaurus eurycephalus, a markedly elongate, pointed rostrum is present in T. acutirostris and a markedly gracile, possibly edentulous rostrum is present in T. azerguensis, for example. This variation is consistent with the idea that taxonomic revision of the group is required: the named taxa may not be close relatives at all.

Just four of the six (or so) currently recognised Temnodontosaurus species. How many 'genera' do you see? An analysis that treats each species as a separate OTU has yet to be published. We're working on it. Images from papers by Chris McGowan alike (note that T. longirostris has proved to be based on specimens of Eurhinosaurus and Leptonectes: thanks to CCollinson for pointing this out).

T. eurycephalus is one of the most incredible of ichthyosaurs. Only a single skull, discovered at Lyme Regis, is known, the basisphenoid of a far smaller ichthyosaur preserved clenched between its teeth! (did the T. eurycephalus really die while eating another ichthyosaur, were these remains vomited up during death, or is the association just a fluke?). An interesting historical snippet is that this specimen (its length exceeding 1 m) was originally referred to Ichthyosaurus breviceps, a short-nosed thunnosaurian universally regarded as a diminutive ichthyosaur that rarely exceeds 2 m in total length.

Early Jurassic Europe had a fantastic ichthyosaur fauna. As this chart shows (from Hungerbühler & Sachs 1996), in parts of the Toarcian there were contemporaneous temnodontosaurs, eurhinosaurs and thunnosaurians like Stenopterygius. Spot the typo.

More on ichthyosaurs later this year. For previous Tet Zoo articles on ichthyosaurs, see…

Refs – -

Clark, R. 1989. The Charmouth Ichthyosaur. A Dorset Giant. Bristol City Museum and Art Gallery, Bristol.

Fischer, V., Appleby, R. M., Naish, D., Liston, J., Riding, J. B., Brindley, S. & Godefroit, P. 2013. A basal thunnosaurian from Iraq reveals disparate phylogenetic origins for Cretaceous ichthyosaurs. Biology Letters 9, 20130021 http://dx.doi.org/10.1098/rsbl.2013.0021

Hungerbühler, A. & Sachs, S. 1996. Ein grosser Ichthyosaurier aus dem Pliensbachium von Bielefeld. Ber. Naturwiss. Verein Bielifeld u. Umgegend 37, 15-52.

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

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

Sander, P. M. 2000. Ichthyosauria: their diversity, distribution, and phylogeny. Paläontologische Zeitschrift 74, 1-35.

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!

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





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  1. 1. Christopher Taylor 7:30 pm 01/30/2014

    Is that apparent upcurve on the rostrum of Temnodontosaurus platyodon actually a thing, or is it some sort of perspective or preservation distortion?

    Link to this
  2. 2. Yodelling Cyclist 8:26 pm 01/30/2014

    I suspect it’s real, some piscivorous dolphin species have something similar, certainly the Baiji, and a certain recurve element can be see even in the bottlenose lower jaw. I suspect it hinders a fish flopping out.

    Link to this
  3. 3. Tayo Bethel 9:13 pm 01/30/2014

    Which ichthyosaur species might have been predators of larger marine tetrapods?Or took large prey generally?

    Link to this
  4. 4. David Marjanović 10:10 pm 01/30/2014

    Whoa. T. eurycephalus looks a lot like Janjucetus.

    Link to this
  5. 5. David Marjanović 10:11 pm 01/30/2014

    Which ichthyosaur species might have been predators of larger marine tetrapods?Or took large prey generally?

    T. eurycephalus, and T. platyodon, and that’s pretty much it, judging from tooth and jaw shapes.

    Link to this
  6. 6. naishd 4:04 am 01/31/2014

    Thanks for comments. Is the upward curvature in that T. platyodon specimen real? (comment # 1). There’s a fair bit of variation with respect to that curvature – in some specimens the rostrum is straighter than in others. But it does seem to be genuine, and with that specimen in particular (a Bristol specimen figured by McGowan and apparently privately owned) exhibiting especially pronounced curvature.

    Link to this
  7. 7. Yodelling Cyclist 11:07 am 01/31/2014

    I am perhaps being suckered in by the gross morphological similarity with whales, but did any ichthyosaurs filter feed?

    Link to this
  8. 8. naishd 5:33 pm 01/31/2014

    Temnodontosaurs are not the only ichthyosaurs that seem to have been predators of big vertebrates: don’t forget Thalattoarchon; 8.6 m long, from the Triassic of Nevada, and with cutting edges on its teeth that look suited for the slicing of vertebrate tissue.

    Link to this
  9. 9. Tayo Bethel 8:54 pm 01/31/2014

    @yodelling Cyclist:

    A quick and dirty Google search doesnt turn up any known filter-feeding ichthyosaurs–whichis not to say they didn’t exist. Come to think of it, very few marine reptiles seem to have been filter feeders. Perhaps some apparently toothless ichthyosaurs may have possessed structures analogous to the baleen of baleen whales.
    Or they may have been suction feeders that swallowed more sizable prey without the need for any filtering structures. Just speculations from a lay person obsessed with all things tetrapod.

    Link to this
  10. 10. naishd 3:59 am 02/1/2014

    The whole “where are all the suspension-feeding Mesozoic marine reptiles” thing has been an oft-asked question over the years, explored in particular in…

    Collin, R. & Janis, C. M. 1997. Morphological constraints on tetrapod feeding mechanisms: why were there no suspension-feeding marine reptiles? In Callaway, J. & Massare, J. (eds) Ancient Marine Reptiles. Academic Press (London), pp. 451-466.

    They argued that, since reptiles cannot form a tight seal at the back of the palate due to their lack of soft structures that allow separation between mouth and throat, they are unable to engulf mouthfuls of water that can then be treated to filtering. It’s an interesting argument, but I think it’s erroneous: turtles (like matamatas) show that water can be engulfed, retained, and then expelled through the mouth just fine – ‘all’ you need to do is evolve a filtering apparatus at the mouth. So far as we know, plesiosaurs, ichthyosaurs and so didn’t ever do this, but placodonts did – Henodus has features indicating that it was a suspension-feeder. The brand-new, sauropterygian or thalattosaur relative Atopodentatus also has suspension-feeding adaptations.

    Link to this
  11. 11. BonesBehaviours 4:20 am 02/1/2014

    So together with archosaur viviparity in geosaurs, does this mean Dougal Dixon’s vortex makes sense after all?

    Link to this
  12. 12. David Marjanović 8:53 am 02/1/2014

    I hadn’t heard of Thalassoarchon. I hadn’t heard of Temnodontosaurus eurycephalus either before this post… :-]

    since reptiles cannot form a tight seal at the back of the palate due to their lack of soft structures that allow separation between mouth and throat

    Except if they’re crocodiles.

    So far as we know, plesiosaurs, ichthyosaurs and so didn’t ever do this

    What about the plesiosaur Aristonectes?

    archosaur viviparity in geosaurs

    *blink* What?

    Link to this
  13. 13. David Marjanović 8:56 am 02/1/2014

    (Admittedly, Aristonectes wouldn’t be a very impressive exception to the rule.)

    Two things about Mesozoic large-bodied filter-feeders: 1) some pachycormiform actinopterygians – Leedsichthys most famously – already were in this business; 2) in the absence of cold polar waters, there’s apparently not enough krill (or whatever) to support something like a baleen whale.

    Link to this
  14. 14. BonesBehaviours 9:37 am 02/1/2014

    Geosaur crocodilians seem to have had a pelvis arranged atypically for viviparous birth as in nothosaurs. I read this in a footnote to a paper and Darren commented upon this as well.

    Aristonectes seems to have been fairly long necked? If this plesiosaur was filtering for food, maybe it was trawling the bottom like the big elasmosaurs but for smaller prey items?

    Link to this
  15. 15. Mike from Ottawa 10:45 am 02/1/2014

    I got me a sweet, sweet Temnodontosaurus plushie from Rebecca Groome (Palaeoplushies at Etsy). Lovely model.

    Link to this
  16. 16. Tayo Bethel 10:46 am 02/1/2014

    @David:

    Back in 2012 there wasan animated discussion on this blog about geosaur viviparity. So far as I know, viviparity is suspected but not proven–not yet at least.

    Is there any open access information about that suspension-feeding Thalattosuchian (if I’m using the correct term)? Since no one has or is likely to find a fossilized soft palate in any fossil,we will pprobably never know if plesiosaurs and ichthyosaurs might have independently evolved such structures.

    Link to this
  17. 17. Heteromeles 11:26 am 02/1/2014

    Speaking of ichthyosaurs with unusual (filter-feeding) morphology, what’s the deal with Shonisaurus and Shastasaurus? Giant and toothless? That sounds vaguely familiar for some reason, but I don’t see any baleen analogs. Were they giant suction feeders on squid, or something?

    Link to this
  18. 18. Yodelling Cyclist 11:42 am 02/1/2014

    How much is known about stomatosuchus? I’ve read brief references in the popular literature, and it seems to suggest that there was sufficient suspended food in tropical freshwater to support a large (5m+) crocodilian. Can any of the pros clarify/expand on this?

    Best wishes, and as ever thanks for the replies and new knowledge.
    Yod

    Link to this
  19. 19. LeeB 1 6:02 pm 02/1/2014

    Heteromeles, the recent paper by Motani et. al. in Plos One suggests that the giant Triassic ichthyosaurs weren’t suction feeding; because there wasn’t the food available for them to do so.

    See “Absence of suction feeding ichthyosaurs and it’s implications for Triassic mesopelagic palaeoecology”; Plos One 8(12): e66075.

    LeeB.

    Link to this
  20. 20. JAHeadden 5:39 am 02/2/2014

    Speaking of suspension feeding …

    “Atopodentatus unicus” suggests a suspension feeder without the seeming suspension-like features, such as a long retroarticular of gaping jaws or a broad jaw with a noticeable gape (creating high volume in the oral cavity). Julius Cstonyi just did a “quick sketch” over on Facebook that recalls bowhead/right whales (upper jaw raises rather than lower jaw suspends) that is reinforcing an idea that this animal was somewhat a near-shore benthic feeder with planktonivorous aspects. Ca-ray-zee.

    Link to this
  21. 21. BonesBehaviours 7:23 am 02/2/2014

    Fuck me, Atopodentatus in effect had two upper jaws?

    Link to this
  22. 22. Tayo Bethel 10:40 am 02/2/2014

    If baleen whales were known only from fossils,wouldwe be able to tell whether they were filter feeders or not?

    Link to this
  23. 23. Gigantala 11:25 am 02/2/2014

    I’ve since gone back on my rejection of “metriorhynchid” vivipary, since early crocodylomorphs had soft shelled eggs appearently if Baurusuchus is of any indication.

    The reason Mesozoic oceans seem devoid of large filter feeders sans pachycormids is most likely explained due to warmer global temperatures not generating enough planktonic crustacean biomass, but this is less of an excuse in time periods where global temperatures dropped radically. One would expect at least one tentative filter feeder during the Lower Cretaceous.

    Link to this
  24. 24. Tayo Bethel 4:15 pm 02/2/2014

    @Gigantala

    Have Baurusuchus eggs been found?

    Apparently there were giant filter-feeding fish in the Mesozoic–just very few or no filter-feeding marine reptiles. Apparently.

    Link to this
  25. 25. Gigantala 4:55 pm 02/2/2014

    Well, not Baurusuchus per se, but defenitely sebecian eggs:

    Oliveira, C.E.M.; Santucci, R.M.; Andrade, M.B.; Fulfaro, V.J.; Basílo, J.A.F.; and Benton, M.J. (2011). “Crocodylomorph eggs and eggshells from the Adamantina Formation (Bauru Group), Upper Cretaceous of Brazil”

    Link to this
  26. 26. Heteromeles 6:46 pm 02/2/2014

    Um, about filter feeders not feeding in tropical waters…. mumble mumble MANTA RAYS, mumble mumble MINKE WHALES mumble mumble WHALE SHARKS mumble mumble.

    Somehow, I don’t think warm waters are quite as free of plankton as you think, although I agree that blue whale-sized critters might have trouble migrating far enough to find enough to eat in a warm-world ocean. This is, of course, unless there are upwelling zones as off the coast of southern California (where blue whales currently congregate to feed on krill swarms up to a few hundred feet down)

    I’m working on a piece about what the world might look like after fairly extreme global warming, so I’m actually reading a bit outside of Wikipedia on globally warm oceans, for a change. Fun stuff.

    Link to this
  27. 27. LeeB 1 8:58 pm 02/2/2014

    Well something interesting was going on in the later Jurassic and early Cretaceous.
    There must have been a reasonable amount of biomass available in deep water (mesopelagic zone) because some of the ichthyosaurs started developing very large eyes suggesting they were deep divers; i.e. Ophthalmosaurus, Baptanodon and Leninia.

    The largest Temnodontosaurus had similar sized eyes but at a much greater body size; meaning the Ophthalmosaurs eyes were proportionately larger.
    Their eyes were even bigger than those of a big eye thresher shark or broadbill swordfish; both of which feed in deep water or at night in low light conditions.

    However these ichthyosaurs do not seem to be filter feeders, they retain teeth in their jaws.

    LeeB.

    Link to this
  28. 28. David Marjanović 3:31 pm 02/3/2014

    Geosaur crocodilians seem to have had a pelvis arranged atypically for viviparous birth as in nothosaurs. I read this in a footnote to a paper and Darren commented upon this as well.

    I can’t remember.

    Aristonectes seems to have been fairly long necked? If this plesiosaur was filtering for food, maybe it was trawling the bottom like the big elasmosaurs but for smaller prey items?

    Could of course be.

    Oliveira, C.E.M.; Santucci, R.M.; Andrade, M.B.; Fulfaro, V.J.; Basílo, J.A.F.; and Benton, M.J. (2011). “Crocodylomorph eggs and eggshells from the Adamantina Formation (Bauru Group), Upper Cretaceous of Brazil”

    Found it; it’s in Palaeontology 54(2): 309–321. I’ll have to read it tomorrow. The abstract doesn’t say “soft”, though, just “thin”.

    Um, about filter feeders not feeding in tropical waters…. mumble mumble MANTA RAYS, mumble mumble MINKE WHALES mumble mumble WHALE SHARKS mumble mumble.

    The point is that once you add the basking sharks, this is an exhaustive list. The contrast to the diversity of baleen whales in polar/subpolar waters is striking.

    Link to this
  29. 29. JAHeadden 4:03 pm 02/3/2014

    On suspension feeding. I think there should be several unrecognized filter feeders. Not all “known” filterers co-occur, with Henodus from the Late Triassic (one of the youngest placodonts) and our freakish friend Atopodentatus from the lower Mid Triassic. They could have adapted on different foodstuffs, but for the most part it shows there were sources of food abundant enough to drive the evolution of these things. We should expect to find other sauropterygian-like animals with similar adaptations on the lineages towards Atopodentatus and Henodus.

    But living filterfeeders don’t always have “obvious” filtering types of jaws. Someone mentioned how we’d ever think of baleen whales as filterers without the baleen plates, and the real answer to that is the enormous jaws, gape capability, and absence of any other type of diet: They were engulfers of mass quantities of food. These animals not only eat krill, plankton, etc., they also eat fish. Benthic animals, though, are different. Crabeater seals are a good example of zooplankton specialists, are fully toothed, and show that an environment can host multiple filterers (right whales and seals).

    So perhaps many known ichthyosaurs and plesiosaurs, perhaps including Aristonectes mentioned above, were filterers though not obviously so. It helps to have a wide jaw, gape-capability, and ease of mobility to engulf food quickly. Purging water shouldn’t be a problem: Several marine sauropsidans can do it, and these suggest it is possible other animals can pick up the “trick.” Plesiosaurs MUST have fed through ram suction, engulfing or capturing prey and purging the water through their nose or however, and they seem well suited for such behavior. Ichthyosaurs I imagine are trickier, but short- and wide-jawed early forms probably fared better than long- and narrow-jawed later Jurassic and Cretaceous forms. It’s quite likely there was a range of marine reptile suspension feeders throughout the Mesozoic, being replaced by the advent of fish when they died off, or perhaps being competed with.

    Apologies on the lack of scholarship: I’m musing on this.

    As for the typo: ExcalibRosaurus.

    Link to this
  30. 30. Yodelling Cyclist 4:21 pm 02/3/2014

    Apologies for a brief post. Pygmy blue whales are tropical filter feeders.

    Link to this
  31. 31. Yodelling Cyclist 4:27 pm 02/3/2014

    Sorry again, megamouth sharks, gray whales (I appreciate the later are benthic filter feeders, still filter feeding.)

    What’s the size cut off here? Can I include fusiliers (apologies for even more fish)?

    Link to this
  32. 32. Gigantala 4:33 pm 02/3/2014

    Long necked plesiosaurs at least seem somewhat analogous to gray whales, so some species doing a jump to pelagic filter feeders makes sense.

    Link to this
  33. 33. Yodelling Cyclist 4:54 pm 02/3/2014

    Again, apologies for brevity. Why must there be cold water for major plankton blooms? The long growing season at high latitudes, coupled with seasonal nutrient availability I get, but not the need for cold. Higher oxygen concentration is one thing, but for nektonic plankton I am surprised that this is considered essential.

    Link to this
  34. 34. Heteromeles 5:30 pm 02/3/2014

    So far as warm seas go, I’ve been reading up a bit on the PETM, which was one of the warmest of the recent seas and a good model for about the worst we can do at global warming (fingers crossed). Yes, there were large dead zones in the PETM sea. However, IIRC, there is evidence of deep ocean bioturbation from other places in the PETM (and unfortunately, I just returned the books I found this in, which were Huber et al’s (2000) Warm Climates in Earth History and Wing et al’s (2003) Causes and Consequences of Globally Warm Climates in the Early Paleogene).

    My suspicion is that, even at their warmest, Earth’s seas seldom (if ever) became globally anoxic in deep water. Yes, they had huge dead zones, but there were other places where enough oxygen reached the bottom in the deep sea that bottom-dwelling organisms churned up the sediments and left behind ichnofossils that researchers have found.

    Link to this
  35. 35. Dartian 9:21 am 02/4/2014

    David:
    The point is that once you add the basking sharks, this is an exhaustive list. The contrast to the diversity of baleen whales in polar/subpolar waters is striking.

    But, on the other hand, the mysticetes represent just one single radiation, whereas in elasmobranchs, filter-feeding has evolved at least four times: in basking sharks, megamouth sharks, whale sharks, and manta rays. So in that sense, at least, giant filter-feeding elasmobranchs are more diverse than cetaceans.

    Link to this
  36. 36. CCollinson 2:21 am 02/5/2014

    Christopher McGowan found the holotype of Ichthyosaurus longirostris to be a specimen of Eurhinosaurus due to the characteristically abbreviated lower jaw. With the remaining specimens making up the Ichthyosaurus longirostris paradigm, including the specimen above illustrated as Temnodontosaurus longirostris, being referred to Leptonectes tenuirostris. So one less species of Temnodontosaurus.

    Link to this
  37. 37. naishd 4:56 am 02/5/2014

    Thanks, CCollinson: I have often been confused about the status of longirostris and, yes, screwed up in including it here. I should replace it with the even more gracile-snouted T. azerguensis.

    Am going to tweak the text above to bring attention to this.

    Link to this
  38. 38. David Marjanović 4:16 pm 02/5/2014

    nektonic plankton

    That’s a contradiction in terms – what do you mean?

    But, on the other hand, the mysticetes represent just one single radiation, whereas in elasmobranchs, filter-feeding has evolved at least four times: in basking sharks, megamouth sharks, whale sharks, and manta rays. So in that sense, at least, giant filter-feeding elasmobranchs are more diverse than cetaceans.

    Conversely, the mysticetes have been spectacularly successful, with 15 extant species and a whole lot of extinct ones according to Wikipedia, while there’s one species of basking shark, one species of whale shark, one species of megamouth shark (which I didn’t count because it lives at such great depths), and… admittedly 11 species of Mobula + Manta. The point I was trying to make is that the big filter-feeding chondrichthyans are one-off events unlike Mysticeti; admittedly the mantas aren’t quite happy with that..

    Link to this
  39. 39. Gigantala 5:06 pm 02/5/2014

    One should perhaps look at it in the context of their ecological niche and efficacy. Sharks might be capable of developing filter feeding easier, but they may be less effective at it than mysticetes, which explains they the latter diversified at the expense of the possibility of any other large filter feeder aside from a few sharks.

    Perhaps filter feeding sharks were once more speciose, before whales became dominant. We just happen to be left without fossils due to their cartilage skeletons and miniscule teeth.

    Link to this
  40. 40. Yodelling Cyclist 6:10 pm 02/5/2014

    @David Marjanović: Yes, yes, apologies and thank you for the correction. I meant small creatures such as krill – a trophic level linking the true phyto- and zooplankton with the higher nektonic levels of the trophic web populated by species of larger body mass.

    Thinking specifically of krill, I will mount a weak defence of my previous term (despite its being an oxymoron from the perspective of the Greek roots). They can swim, briefly, against a weak current, but under normal circumstances their migrations are driven by oceanic currents. Krill occupy an odd place between true drifting plankton and vigorously swimming nekton.

    On the subject of Megamouth – it’s a filter feeder. Blue whales supposedly at depths greater than 100m.

    Still don’t understand why we need cold water.

    Oh, and I remember as well that there’s a resident population of humpback whales in the Arabian sea.

    Link to this
  41. 41. Yodelling Cyclist 6:35 pm 02/5/2014

    Oh, and off topic, with the news of a “new” beaked whale being found:

    http://news.sciencemag.org/biology/2014/02/dried-meat-resurrects-lost-species-whale

    Question for Darren:

    Based on the discovery curves, how many new species does this leave to find in the open ocean? (I want my sea serpent!)

    Link to this
  42. 42. SciaticPain 4:52 pm 02/7/2014

    A little late to the party but interesting discussions pertaining to filter feeding.

    My addition to the discussion is that there was probably loads of filter feeding during the Mesozoic but that the majority of it was being conducted not by large vertebrates but by invertebrates, chiefly reef building rudistid clams. Following this I would suggest that even today it is invertebrates and small fish, not whales, sharks, rays etc etc, that handle the lions share of filter feeding in the oceans.

    Regarding the connection between cold water, high productivity. Cold water upwellings supply a good doze of fertilizer to the photic zone which enhances the phytoplankton pasture for krill, copepods etc etc. which in turn allow for the massive whales we have at this particular juncture in earth’s history. But there are many other ways to fertilize the ocean- wind blown dust such as in the Arabian ocean, input from terrestrial rivers- which, then as now, may have allowed for high productivity even in warm seas.

    Also keep in mind that manta rays and whale sharks are not so much munching on concentrated patches of krill and other crustaceans but often times from a more diffuse soup of larvae, eggs, and other less conspicuous parts of the planktonic mix. Both also take advantage of seasonal gluts of coral sperm/eggs and fish spawning events. But crustacean blooms, primarily of cold upwelling areas, are a special occurrence that allow for the unique radiation of large, active baleen whales we see today. Otherwise you can’t grow a blue whale without such rich food patches.

    But my suspicion is that, then as now, large bodied, homeothermic obligate filter feeders were rare in warm oceans. And that the few we may have in the fossil record are outliers.

    Duane Nash

    Link to this

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