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‘Rigid Swimmer’ and the Cretaceous Ichthyosaur Revolution (part I)

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


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You’re reading a blog. This almost guarantees the fact that you’re a staunch supporter, and fan, of open-access publishing. Many of us who publish technical research really do try to publish in open-access venues as often as possible. Doing so is generally good for citation indices and all that, but it’s especially important if you care about outreach and about the public availability of your research. I’ve published in open-access journals before (Witton & Naish 2008, Taylor et al. 2009), and I’m very happy to say that my very newest paper – it’s out today – is published in the open-access, 100% available-to-all journal PLoS ONE.

The new Hauterivian ophthalmosaurine ichthyosaur Acamptonectes densus Fischer et al., 2012, as reconstructed by C. M. Kosemen (contact c.m.kosemen@gmail.com).

The article concerned is co-authored with Valentin Fischer, Michael Maisch and others and is predominantly based around the naming of a very interesting new Cretaceous ichthyosaur (Fischer et al. 2012). As we explain – and as I’ll summarise here – it isn’t just any old ichthyosaur; it has major ramifications for our understanding of ichthyosaur diversity across time, and especially about their history across the Jurassic-Cretaceous boundary (known for short as the J/K boundary event or as the JCB event).

For some decades now the general feeling about ichthyosaur history and diversity has been that things were going very well for ichthyosaurs during the Late Triassic and Early Jurassic, that diversity declined during the Middle and Late Jurassic, and that ichthyosaur diversity during the Cretaceous was so low that the group was essentially just lingering on and doomed never to do anything interesting ever again. The JCB was regarded as a major extinction event for ichthyosaurs, with the successful and globally distributed ophthalmosaurine thunnosaurians being killed off, their place taken by the supposedly “much more generalized” platypterygiines (Bakker 1993). This fits with wider evidence showing that other marine groups (including thalattosuchian crocodilians and plesiosaurs) were affected quite seriously by the JCB event (Benson et al. 2010).

Skull of the platypterygiine Brachypterygius, from McGowan & Motani (2003). This skull was originally used to erect the new taxon Grendelius mordax - an awesome name. Grendelius is certainly synonymous with Brachypterygius, but opinions differ as to whether B. mordax is distinct from the type species, B. extremus.

Of ophthalmosaurines and platypterygiines

For ease of communication, I have to explain here that I and my co-authors follow a system where ophthalmosaurines and platypterygiines are grouped together into the more inclusive clade Ophthalmosauridae. Ophthalmosauridae is part of Thunnosauria, an ichthyosaurian clade that also includes Ichthyosaurus and Stenopterygius.

Many ichthyosaur workers have long suspected a divergence of Ophthalmosauridae into distinct ophthalmosaurine and platypterygiine clades, so one of the most satisfying phylogenetic aspects of our study is that we were able to find robust support for this division (Fischer et al. 2012). Because there are ophthalmosaurines from the Middle Jurassic (like Mollesaurus), the ophthalmosaurine/platypterygiine divergence must have occurred by this time.

Ophthalmosaurus icenicus, best known ophthalmosaurine. The life restoration is by Ken Kirkland; the skeletal is from Sander (2000).

Ophthalmosaurines were big-eyed, deep-diving thunnosaurians, well known for possessing a tuna-like body shape and hence likely sharing with tuna (and other thunniform vertebrates) a high swimming speed and endothermic physiology (Motani 2002, 2005). Platypterygiines have proportionally smaller eyes, and also have a more robust snout form, larger teeth, and a longer, less tuna-like body shape. If the JCB was a time of ecological turmoil and reorganisation (as often seems to be the case during extinction events), it would seem logical that ophthalmosaurines – conceivably tied to specific and reliable resources – would become extinct, whereas generalist platypterygiines – able to make a living whatever the available prey – would survive (this view of platypterygiines as generalists is supported by data from stomach contents: Kear et al. 2003). This tidy story of major ichthyosaur turnover at the JCB was stated most specifically and confidently by Bakker (1993). There is a problem though: it’s wrong.

Our changing view of Cretaceous ichthyosaur diversity

Athabascasaurus bitumineus, a recently named, Canadian platypterygiine.

Within recent years, our views of Cretaceous ichthyosaur diversity have really changed a lot. Firstly, we’ve had some new taxa published, like Maiaspondylus lindoei Maxwell & Caldwell, 2006 from Northwest Territories, Canada, Athabascasaurus bitumineus Druckenmiller & Maxwell, 2010 from Alberta [shown here; image from here at Syncrude Canada Ltd.], and Sveltonectes insolitus Fischer et al., 2011 from Russia.

Secondly, a list of taxa originally described from the Upper Jurassic – namely Brachypterygius, Aegirosaurus, Caypullisaurus and Yasykovia – have now been reported from Lower Cretaceous sediments (McGowan & Motani 2003, Fernández & Aguirre-Urreta 2005, Efimov & Komarov 2010, Fischer et al. 2011). Additionally, Ophthalmosaurus – originally described from the Middle Jurassic – has been reported from the Lower Cretaceous of Canada and England (McGowan & Motani 2003). These Cretaceous Ophthalmosaurus records are ambiguous given that the characters used to refer them to Ophthalmosaurus are now known to have a broader distribution. Additional English records, however, can at least be identified as cf. Ophthalmosaurus (Fischer et al. 2011). The presence of these many ‘Jurassic’ ophthalmosaurids in the Cretaceous shows that the JCB was not a major extinction event for ichthyosaurs – many lineages crossed the boundary just fine (Fischer et al. 2011).

Neoichthyosaurian phylogeny plotted against time, from Fischer et al. (2012). Note how many ophthalmosaurid lineages cross the JCB.

Thirdly, the ichthyosaur taxon that (prior to these new discoveries) was typically thought to be the only Cretaceous representative of the group – 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 in press). 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).

Yet another new Cretaceous ichthyosaur

GLAHM 132588, the Acamptonectes densus holotype.

Our new paper adds to this story, for we describe another new Cretaceous ichthyosaur. Yes, say hello to Acamptonectes densus Fischer et al., 2012 from the Lower Cretaceous of England and Germany. The history of our research on Acamptonectes is kind of interesting. This is one of several new ichthyosaur taxa originally studied by the late Robert Appleby; the best specimen [shown above] is from the Speeton Clay of North Yorkshire in England, where it was discovered in 1958. Despite penning an essentially complete description, Appleby never got round to publishing it. Within recent years, I worked with Jeff Liston and the late Arthur Cruickshank to get several of Appleby’s unpublished manuscripts into print. However, Appleby regarded Acamptonectes as a new species of Platypterygius (dubbed ‘P. speetoni’). This opened up a whole world of hurt, since I couldn’t finish the project without comparing the Speeton Clay ichthyosaur to the many new platypterygiine taxa named since Appleby had stopped his work on this taxon.

Skull (and part of neck) of the Crelimgen Acamptonectes, from Fischer et al. (2012).

Unbeknownst to me, a new Lower Cretaceous ophthalmosaurid ichthyosaur had been discovered in Cremlingen, Germany, in 2003. It was being studied by Valentin Fischer, Michael Maisch and a number of collaborators. It represented a new taxon, but the characters that made it distinctive and unique compared to other ophthalmosaurids were also present in the Speeton Clay animal. In other words, they represented the same new animal. So, when Valentin visited the Speeton Clay ichthyosaur at its home in Glasgow’s Hunterian Museum in Scotland (Jeff’s former academic base), collaboration was born. We ended up using the Speeton Clay specimen as the holotype and the Cremlington specimen (a subadult) as a paratype (Fischer et al. 2012). A second Speeton Clay specimen, discovered in 1985, is in the collections of the Natural History Museum in London and was used by us as a second paratype. Both the Speeton Clay and the Cremlingen strata that yielded the Acamptonectes specimens are Hauterivian in age, but the former are early Hauterivian and the latter are late Hauterivian (Fischer et al. 2012 and references within).

Reconstructed skeleton of Ophthalmosaurus icenicus from the English Oxford Clay, by Captmondo.

It was always obvious that the new animal was an ophthalmosaurid, as it shares a large number of characters with Ophthalmosaurus, Brachypterygius, Mollesaurus and their relatives (distinctive ophthalmosaurid characters include the form of the basioccipital and the presence of three facets on the distal end of the humerus). Within Ophthalmosauridae, Acamptonectes lacks the numerous derived characters that unite the members of Platypterygiinae, and in a phylogenetic analysis it grouped close to Ophthalmosaurus (Fischer et al. 2012). Appleby was wrong in thinking that Acamptonectes was close to (or part of) Platypterygius; instead, it’s an ophthalmosaurine. [Ophthalmosaurus photo by Captmondo, from wikipedia.]

The ophthalmosaurines we know of are conservative, and approximately similar in body shape and proportions. So, what makes Acamptonectes so special? Its snout is shallow compared to that of its relatives, and its teeth are slender-crowned and with sharply pointed crowns (suggestions that some ophthalmosaurines were toothless are not correct). Compared to other ophthalmosaurines, it has features indicating that parts of its skeleton were unusually rigid and firmly locked together. The head of the slender-shafted stapes is expanded and massive and, in life, would have had a particularly strong union with the adjacent opisthotic and basioccipital bones. The basioccipital is typically a very important bone in ichthyosaur identification, and that of Acamptonectes is no exception, possessing an unusual bilobed concavity on its dorsal surface.

Basioccipital of Acamptonectes densus, in posterior (A, D), dorsal (B, E) and ventral (C, F) views. Note the bilobed concavity in B and E. See Fischer et al. (2012) for more information.

The centra of the cervical and dorsal vertebrae have peculiar, S-shaped articular surfaces, and they interlock tightly. This means that the anterior part of the vertebral column was very stiff, with hardly any side-to-side motion being possible. This might sound odd for an animal that swims with lateral movements of its vertical tail fin, but it’s an accentuated version of a trend seen in other thunnosaurian ichthyosaurs. As they came to rely more and more on the distal, finned part of the tail for propulsion (rather than on the tail as a whole), they stiffened up the body. Similar trends are seen in other vertebrates that have become specialised for so-called carangiform swimming: in lamnid sharks, tunas and billfishes, for example, there isn’t much lateral movement in the body or anterior part of the tail either.

Another distinctive feature of Acamptonectes is that its ribs are rounded in cross-section. In other thunnosaurians, deep grooves on both surfaces of the rib shaft mean that each rib is 8-shaped in cross-section. The rounded and rather robust rib shafts of Acamptonectes were presumably more resistant to bending than those of other thunnosaurians – is this a further adaptation to increase stiffness in the animal’s body?

Combined, these unusual features of the skull and axial skeleton in particular inspired us to come up with the name Acamptonectes densus Fischer et al., 2012 for our new animal. It means something like ‘tightly packed rigid swimmer’, and it refers to the chunky, tightly fitting nature of the occipital bones and vertebrae.

While Acamptonectes was especially robust in some regards, it’s worth saying that the massive, stout proportions of ophthalmosaurid anatomy are not sufficiently appreciated. You might get the impression from artistic reconstructions that ophthalmosaurids (both ophthalmosaurines and platypterygiines) were similar in overall proportions to, say, bottlenose dolphins, and with laterally compressed fore- and hindpaddles. In fact, their skulls are often extremely broad and chunky across the occipital region and the rostrum is usually very broad-based and deep at the level of the nostril. Ophthalmosaurid forepaddles are generally enormous: they’re very broad (and long in platypterygiines), but also surprisingly thick, with very prominent bony crests on the humerus meaning that the paddle was massively muscled [check out the impressive thickness on the humerus and phalanges in the ophthalmosaurid forefin shown in the adjacent photo]. Even the oval or rectangular phalanges in the more distal parts of the paddle are thick and robust, and not delicate tiles as you might assume.

Acamptonectes to the end

Our holotype and paratype specimens of Acamptonectes are from the Hauterivian. But it gets better: numerous fossils referable to Acamptonectes are also present in the English Cambridge Greensand. This is lower Cenomanian in age and thus about 30 million years younger than the late Hauterivian strata that yielded the Cremlington A. densus specimen. While the Cambridge Greensand fossils can be confidently referred to Acamptonectes, they differ from the A. densus specimens in various details (in possessing, for example, a larger extracondylar area on the basioccipital). This means that they can be identified as Acamptonectes sp., but not necessarily as A. densus (Fischer et al. 2012) – a conclusion that seems reasonable in any case given that c. 30 million year difference in age. More material is needed before we can determine with precision the specific status of the Cambridge Greensand Acamptonectes. Anyway, the most interesting thing here is that Acamptonectes was present from the early Hauterivian until the early Cenomanian.

The basisphenoid (a bone from the very bottom of the braincase) described as Ichthyosaurus brunsvicensis by Broili (1909). L: ventral view. R: anterior view.

Of further interest here is that a very Acamptonectes-like ophthalmosaurid was described from the Cretaceous of Germany in 1909 and named Ichthyosaurus brunsvicensis. This name has generally been regarded as a nomen dubium, and the specimen lacked the diagnostic characters of Acamptonectes (like that bilobed cavity on the basioccipital). The situation isn’t helped by the fact that the specimen was destroyed during WWII. We identify the 1909 specimen as cf. Acamptonectes and hope that new material will one day be found that allows it to be confirmed as an additional ophthalmosaurine taxon.

Anyway, we can now say that Acamptonectes was present until the Cenomanian. This is particularly interesting in the context of Cretaceous ichthyosaur diversity since it shows that Ophthalmosaurinae was long-lived, and that it persisted until virtually the end of recorded ichthyosaur history. Previously, only platypterygiines were known from these younger Cretaceous strata. The last ichthyosaurs, then, were not lone representatives of a single lineage: rather, “the ‘last’ ichthyosaurs were actually taxonomically diverse and morphologically disparate, making their Cenomanian extinction far more severe than previously assumed” (Fischer et al. 2012, p. 20).

Ichthyosaur diversity plotted against time, from Fischer et al. (2011). The dark parts of the graph show how the number of known taxa has changed since 2003. It's obvious that Cretaceous ichthyosaur diversity is now rather higher than previously thought.

New evidence, then, does not support the idea that the JCB event was a major event in ichthyosaur evolution as previously thought. Rather, ichthyosaurs of numerous lineages apparently sailed across the boundary without event. Quite why this is so when there’s good evidence that other marine reptile groups were affected quite severely by the JCB event is now a very good question – were ichthyosaurs actually highly resistant to whatever events caused this biological crisis? Furthermore, Early Cretaceous ichthyosaurs were not rare, sorry stragglers of a previous Golden Age – we are learning that ophthalmosaurids, at least, were doing quite well at this time, with diversity and disparity being reasonably high. Finally, ophthalmosaurines and platypterygiines both made it to the Cenomanian, suggesting that both clades were similarly affected by the same Cenomanian extinction event. Gradually, we are revising our views of what marine reptile diversity was like in the Cretaceous.

And, as I so often say, there is more to come.

UPDATE: A far more detailed, more historically accurate account of the story behind the work on the Speeton Clay 1958 A. densus specimen has been written up by Jeff Liston for Mr Wood’s Fossils.

For previous Tet Zoo articles on ichthyosaurs, see…

UPDATE: while we’re here… some of you will be aware of the Research Works Act, a vile, nefarious attempt by some academic publishers to RESTRICT ACCESS TO ACADEMIC PUBLICATIONS AS MUCH AS POSSIBLE. We need to act (and act before January 12th) – please read the article here.

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., Butler, R. J., Lindgren, J. & Smith, A. S. 2010. Mesozoic marine tetrapod diversity: mass extinctions and temporal heterogeneity in geological megabiases affecting vertebrates. Proceedings of the Royal Society B 277, 829-834.

Broili, F. 1909. Neue Ichthyosaurierreste aus der Kreide Norddeustschlands und das Hypophysenloch bei Ichthyosauriern. Palaeontographica 55, 295-302.

Efimov, D. V. & Komarov, V. N. 2010. The first find of fragments of a skeleton of the ichthyosaur Yasykovia in the Valanginian of Crimea. In Baraboshkin, E., Blagoveschensky, I. V. (eds) Cretaceous System of Russia and CIS States: Problems of Stratigraphy and Palaeogeography Materials of the 5th All-Russian Meeting (August 23-28, 2010, Ulianovsk), Ulyanovsk, pp. 132–135.

Fernández, M. & Aguirre-Urreta, M. B. 2005. Revision of Platypterygius hauthali von Huene, 1927 (Ichthyosauria, Ophthalmosauridae) from the Early Cretaceous of Patagonia, Argentina. Journal of Vertebrate Paleontology 25, 583-587.

Fischer, V. In press. New data on the ichthyosaur Platypterygius hercynicus and its implications for the validity of the genus. Acta Palaeontologica Polonica.

Fischer, V., Clément, A., Guiomar, M., & Godefroit, P. (2011). 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

Kear, B. P., Boles, W. E. & Smith, E. T. 2003. Unusual gut contents in a Cretaceous ichthyosaur. Philosophical Transactions of the Royal Society of London B (Suppl.) 270, S206-S208.

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).

Motani, R. 2002. Scaling effects in caudal fin propulsion and the speed of ichthyosaurs. Nature 415, 309-312.

- . 2005. Evolution of fish-shaped reptiles (Reptilia: Ichthyopterygia) in their physical environments and constraints. Annual Review of Earth and Planetary Sciences 33, 395-420.

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

Taylor, M. P., Wedel, M. J. & Naish, D. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54, 213-220.

Witton, M. P. & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3 (5): e2271. doi:10.1371/journal.pone.0002271

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. Halbred 5:52 pm 01/3/2012

    Congratulations on the new taxon! It’s also extremely interesting to see that ichthyosaurs remained very diverse until the bitter end. One wonders how they dealt with the rise of mosasaurs–if they dealt with it at all. And the body-stiffening bit is cool in that this same feature was recently found on a Kansas mosasaur fossil (also from PLoS ONE), though based on preserved scales, not skeleton.

    Link to this
  2. 2. David Marjanović 6:38 pm 01/3/2012

    That went pretty fast! I submitted my review in early November… :-]

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  3. 3. Bora Zivkovic 7:38 pm 01/3/2012

    Awesome! An impressive paper!

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  4. 4. LeeB 1 8:50 pm 01/3/2012

    Very nice new paper.
    Congratulations.
    This looks like a second major revolution in marine reptile taxonomy and phylogeny in the last few years.
    First the metriorhynchid’s taxonomy was sorted out and now the ophthalmosaurs.
    It will be interesting to see how many genera are raised out of both Platypterygius and Ophthalmosaurus,
    and also what happens to the numerous Russian Ophthalmosaur genera that have been named.

    Strange that Nannopterygius doesn’t feature in any of these cladograms, does it need redescribing?

    And interesting that the Jurassic-Cretaceous boundary turns out to have had so much effect on Metriorhynchids and so little on Ichthyosaurs, although it is possible that lower Cretaceous Metriorhynchids may turn out to be more diverse than currently realised.

    LeeB

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  5. 5. Therizinosaurus 12:53 am 01/4/2012

    Congrats on the paper, and Cretaceous ophthalmosaurs are interesting, but surely the important lesson is to not treat genera as real entities than measure diversity? Seems we always knew there were numerous Cretaceous ichthyosaur species, and it’s no more accurate to split them into multiple genera than it is to just use Platypterygius and Acamptonectes.

    One question though. You assign the Nettleton to cf. Ophthalmosaurus, but then find that the latter genus may be paraphyletic with respect to Acamptonectes. Does the Nettleton material share characters with Ophthalmosaurus sensu stricto, or could it actually be (i.e. closer to) Acamptonectes instead?

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  6. 6. naishd 5:08 am 01/4/2012

    Thanks for comments. Some swift responses…

    LeeB: yes, the Russian ophthalmosaurids need re-evaluation. The tendency among non-Russian authors has been to declare all of the Russian taxa nomina dubia, or junior synonyms of previously named taxa (like Brachypterygius). Nannopterygius is controversial (in terms of phylogenetic position) and under-described – there are plans to get it looked at anew. Here is what I said about it on Tet Zoo ver 2…

    ——————
    Nannopterygius is one of my favourites and is known from a complete skeleton (BMNH 46497, currently panel-mounted in the NHM palaeo corridor, about 3 m off the ground), plus two referred, incomplete specimens (neither of which have been properly described). I was going to include it in the cladogram but ended up not doing so because views on what it is differ so wildly: McGowan & Motani (2003) included it among ophthalmosaurids (which looks mightily unlikely to me) while Maisch & Matzke (2000) placed it somewhere near the base of Thunnosauria, near to Suevoleviathan (which is also missing from the cladogram above).

    For those who don’t know, Nannopterygius has to be one of the most remarkable ichthyosaurs: it has tiny, tiny, massively abbreviated limbs, a reduced pectoral girdle with stretched coracoids, slender, cylindrical ribs and evidence for hefty tail musculature. It was weird.

    Refs – -

    Maisch, M. W. & Matzke, A. T. 2000a. 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.
    ——————

    And – were ophthalmosaurids (or thunnosaurians in general) ‘special’ with respect to their successful crossing of the J/K boundary? Work in progress…

    Darren

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  7. 7. naishd 5:29 am 01/4/2012

    Therizinosaurus (Mickey, comment # 5): you are dead right that ideas about ‘genera’ have clouded the issue (of Cretaceous ichthyosaur diversity). Because a large number of valid species have been grouped together in Platypterygius, people have assumed its monophyly and have therefore regarded it as representing a ‘single score’ for ichthyosaur survival into the Cretaceous. As we note in the paper (and as others say elsewhere), Platypterygius is likely not monophyletic – even so, its constituent taxa should indeed be treated as separate units.

    Regarding the Nettleton cf. Ophthalmosaurus, we mean that this material is specifically closest to O. icenicus and probably a member of the same lineage – thus, it’s Ophthalmosaurus sensu stricto (and it differs from Acamptonectes in such details as the relative size of the distal humeral facets – see pp. 17-18 of the paper). Ophthalmosaurus sensu lato was, as you note, found to be non-monophyletic since O. natans did not form a clade with O. icenicus. There has long been disagreement among ichthyosaur workers as to whether O. natans should be separated from Ophthalmosaurus as Baptanodon. Our phylogeny could provide further support for such a ‘generic’ separation.

    Darren

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  8. 8. HowardRichards 12:00 pm 01/4/2012

    I’ve looked into Open Access Journals in physics (my subject), but they come with a hefty price tag. I don’t have a few hundred bucks in my budget just for page charges.

    On the other hand, we do have arxiv.org, which allows us to publish preprints of articles that should end up in journals. Some journals don’t like this, but Physical Review now asks for submissions to be made through arxiv.org. Maybe biology could get in on this?

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  9. 9. naishd 12:31 pm 01/4/2012

    If you lack funding, the open access journals I’m aware of can waive their publishing charges. Sadly, zoology/biology/palaeontology has yet to devise anything as inherently logical and useful as arxiv (so far as I know). I wonder if it’s just a matter of time?

    Darren

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  10. 10. Jerzy New 3:59 am 01/5/2012

    Congrats, Darren!

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  11. 11. naishd 4:51 am 01/5/2012

    Thanks. We hope that our paper will inspire other researchers to look anew at Cretaceous ophthalmosaurid specimens and publish on them (already we have interesting additional data from various sources). There was a lot of interest in the paper yesterday – seems to have made the German newswires, if not the international ones.

    Darren

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  12. 12. Mike from Ottawa 1:30 am 01/6/2012

    Is there any book out there that does for ichthyosaurs, plesiosaurs and mosasaurs what David Unwin’s ‘Pterosaurs: From Deep Time’ does for pterosaurs (and what we expect Mark Witton’s pterosaur book to do as well!)?

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  13. 13. naishd 4:29 am 01/6/2012

    Mike – there are but a few non-technical works on marine reptiles, and certainly nothing like Unwin’s pterosaur book. Richard Ellis’s Sea Dragons: Predators of the Prehistoric Oceans is just about the only one. It seems about impossible to get publishers to commit to a book on Mesozoic marine reptiles – I got quite far with one a couple of years ago (as with my bird phylogeny book, we got to the stage where several sample spreads were created), but it failed on the launchpad.

    Darren

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  14. 14. Hai~Ren 10:16 am 01/6/2012

    I quite like Mike Everhart’s Oceans of Kansas: A Natural History of the Western Interior Sea, though it covers only a single geographic area within a rather limited span of time. Mike also wrote the book for Sea Monsters: Prehistoric Creatures of the Deep, which is based on the National Geographic film of the same name. There’s also that Walking With Dinosaurs special, Sea Monsters: Prehistoric Predators of the Deep book by Nigel Marven and Jasper James, that accompanies the documentary series.

    But yes, a book about marine reptiles in general across the Mesozoic would be good. I think the closest we’ve got so far is Ancient Marine Reptiles, edited by Jack Callaway and Elizabeth Nicholls.

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  15. 15. ValFisch 7:17 am 01/7/2012

    @Halbred, comment 1
    Yes, we have evidence that the last ichthyosaurs met some of the earliest mosasaurs, but only in certain places of the world (Russia) because our new results actually suggest the extinction was diachronic. I’ll leave it there, for now ;)

    @David, comment 2
    Yes, indeed, actually, the fastest I’ve experienced yet!

    @Therizinosaurus, comment 5
    Indeed, quite a number of species were already known in Cretaceous sediments, but all were referred to _Platypterygius_ or to platypterygiine ophthalmosaurids. As you and Darren have noted, this blurred our view of the diversity and disparity of cretaceous forms. Now we know that cretaceous ichthyosaurs are distant relatives that diverged during the early Middle Jurassic

    Our phylogenetic analysis indeed suggests that _O. natans_ should be referred to its previous moniker _Baptanodon_, but the evidence for this is weak. As we note (Fischer et al. 2012:20):
    “However, _O. natans_ is united with _A. densus_ due to a single homoplastic synapomorphy (reduced crown striations, char. 1) and we do not yet consider this sufficient evidence to resurrect use of the name _Baptanodon_. Because of the obvious differences between _Acamptonectes_ and the _Ophthalmosaurus_ species, we do not consider it preferable to include _Acamptonectes_ within an expanded version of _Ophthalmosaurus_”.

    Valentin

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  16. 16. David Marjanović 6:25 am 01/9/2012

    Yes, we have evidence that the last ichthyosaurs met some of the earliest mosasaurs, but only in certain places of the world (Russia) because our new results actually suggest the extinction was diachronic. I’ll leave it there, for now ;)

    Calm down, my beating heart :-)

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