Tetrapod Zoology

Tetrapod Zoology

Amphibians, reptiles, birds and mammals - living and extinct

The Tet Zoo Manifesto


As is so often the case, I find myself unable to make the time to finish the numerous Tet Zoo articles I want to complete and release upon the world. Through burning frustration and a desire to produce something, here’s this.

Night-time coots and geese, just because. Photo by Darren Naish.

Hmm, another goose. I think there might be a thing going on here. Image by Darren Naish.

Tet Zoo has now been going for more than eight years, yet there are still innumerable lineages that I have yet to write about at all, let alone discuss in anything approaching appropriate depth. However, thanks to my own biases, interests and priorities, there are several groups that have been a constant presence here, their stories repeated and revisited time and time again, often with updates and revisions that reflect new discoveries and the evolving state of our knowledge. While I certainly plan Tet Zoo to be a source of information on all the tetrapods, we might consider the subject areas listed below as those that form the core part of a Tet Zoo Manifesto. Links to key articles are included.

Lizards and frogs and snakes are awesome, even the small, plain-looking ones

Rhacodactylus leachianus henkeli and Tetrapod Zoology Book One (you can see part of Memo Kosemen's cover art); image by Ethan Kocak.

When it comes to tetrapods, I don’t think that there are any boring species. Look at all the frogs, lizards and snakes: you just have to look closely at these animals and read some of the work that’s been done on their ecology, biology, evolution and behaviour – they’re all fascinating. But the great frustration as goes animals like frogs, lizards and snakes is that good discussions devoted to them are all too often locked up in expensive, technical literature, and more needs to be done to bring it to the masses. Thanks (in part) to blogging, things are changing – and not too soon, since many amphibians and reptiles are of major conservation concern. Despite the annoying pull of charismatic megafauna, I’ve done my best to cover them when possible. There is still so much to do. Meanwhile...

‘Non-standard hypotheses’ are cool and interesting, worth knowing about, but ‘non-standard’ for very good reasons

The true origins of mammals, a controversial and little-known hypothesis.

If you read enough arcane literature, you’ll encounter assorted weird, wayward hypotheses about tetrapod evolution. I consider most of them interesting enough to warrant discussion. They don’t stand up well in view of the bulk of data, or our understanding of phylogeny or logic, but they sure are interesting. I’ve covered several such ideas on Tet Zoo...

Birds are dinosaurs, ‘birds’ and ‘dinosaurs’ grade into one another, and the more bird-like of non-bird dinosaurs were extremely similar to early birds

The bird-like non-bird Microraptor, a capable glider with elaborate feathering. Image by Emily Willoughby, used with permission.

Birds are dinosaurs, and virtually everyone who's read the literature on Mesozoic birds and bird-like dinosaurs is familiar with the huge amount of anatomical data that supports this contention. And as we’ve come to know more about the life appearance of Mesozoic dinosaurs, it’s also become more obvious, and better appreciated, that feathered theropods were extremely bird-like in appearance – more bird-like than thought even by champions of the ‘birds are dinosaurs’ movement. Mesozoic dinosaurs are so well-covered in the blogosphere that I tend to avoid writing about them at Tet Zoo. Nevertheless, they've been a constant presence since the early years...

If we’re going to champion the birdiness of dinosaurs, or the dinosaurian nature of birds, it follows that birds of all sorts (yes, even the living ones) need to be included in literary reviews that cover dinosaurs. I’ve put my proverbial money where my mouth is and managed to get a major chapter on birds – all birds – into a major book on dinosaurs (Naish 2012). A push to review the fossil record of birds within the context of dinosaurian diversity is, in part, inspired by the fact that I see major problems with those reviews of the avian fossil record produced by Alan Feduccia.

Images by Emily Willoughby (top left), John Conway (right), and Matt Martyniuk (lower left).

The azhdarchid pterosaurs of the Cretaceous likely followed a ‘terrestrial stalking’ mode of life, and were a significant presence in the continental assemblages of the Cretaceous

A giant azhdarchid is a formidable beast. This illustration - from Witton & Naish (2013) - shows (A) Tyrannosaurus, (B) Romanian maniraptoran Balaur, (C) the long-necked giant azhdarchid Arambourgiania, and (D) a human, all to scale. Image by Mark Witton, from Witton & Naish (2013).

Some years ago now (2008!), Mark Witton and I published a key paper in which we argued that azhdarchid morphology, proportions, palaeoenvironment and palaeoecology best support the idea that they were terrestrial predators or omnivores, most likely specialised for a lifestyle that involved quadrupedal walking and the picking up of small prey items (Witton & Naish 2008). This model has been supported by most subsequent observations and analyses (Carroll et al. 2013, Vremir et al. 2013, Witton & Naish 2013), but it has also been challenged. It has some speculative zoology tie-ins as well...

The diversity of fossil crocodylomorphs is underappreciated and astonishing

Substantially simplified cladogram showing possible topology of crocodyliforms; image by Darren Naish.

All those archosaurs conventionally called ‘crocodilians’ are technically included together within the clade Crocodylomorpha; within this group, the major clade that includes all the more ‘crocodile-like’ lineages is termed Crocodyliformes. I still have yet to write about fossil crocodylomorphs at length: there are several articles on various of the crocodyliform groups, some of which now need to be replaced with wholly renovated versions, but most lineages remain untouched. Thanks to work on Wealden crocodyliforms (Salisbury & Naish 2012), and a great fondness for the marine thalattosuchians of the Jurassic and Cretaceous, I have, however, made a start...

Oh, a review article I wrote on the group (Naish 2001) is now very dated and is not as strong as it could be on croc diversity... I’d like to update it.

Sexual selection may have been an important driving force in the evolution of Mesozoic dinosaurs and pterosaurs

A selection of flamboyant ornithischian dinosaurs. Why were so many dinosaurs so very flamboyant? So that they could tell each other apart, or because - like many living flamboyant animals - their evolution was dominated by sexual selection? Image by Darren Naish.

Cover of the TREE issue that contains Knell et al. (2012): art by Mark Witton.

Together with colleagues, I’ve argued that the elaborate structures seen in the dinosaurs and pterosaurs of the Mesozoic – cranial crests, dorsal sails, head frills, horns and so on – most likely played important roles in sexual and social signalling, and likely evolved within the context of sexual selection pressure (Hone et al. 2012, Knell et al. 2012, 2013, Hone & Naish 2013). While these structures may well have been used in thermoregulation, defence against predators and so on, sexual signalling was probably the main evolutionary force driving their diversity. This subject remains the topic of heated debate. The story so far is covered in the following Tet Zoo articles...

There are other subjects that have been a constant presence on Tet Zoo as well, including giant killer eagles, investigations of ‘mystery’ carcasses, speculative zoology, scientific approaches to cryptozoology, and the dinosaurs of the English Lower Cretaceous. But it’s the subjects listed above that can perhaps, I think, be considered the core components of the Tet Zoo Manifesto. And we'll be visiting all of them again... in time.

Apologies, synapsid-fans, for the lack of mammals and kin. I guess they're just not as controversial. In the image here, Sturnus vulgaris rides Dama dama; photo by Dave Hone.

Refs - -

Carroll, N. R., Poust, A. W. and Varricchio, D. J. 2013. A third azhdarchid pterosaur from the Two Medicine Formation (Campanian) of Montana. In: Sayão, J. M., Costa, F. R., Bantim, R. A. M. & Kellner, A. W. A. International Symposium on Pterosaurs, Rio Ptero 2013, Short Communications. Universidad Federal do Rio de Janeiro: pp 40-42.

Hone, D. W. E. & Naish, D. 2013. The ‘species recognition hypothesis’ does not explain the presence and evolution of exaggerated structures in non-avialan dinosaurs. Journal of Zoology 290, 172-180

- ., Naish, D. & Cuthill, I. C. 2012. Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs? Lethaia 45, 139-156.

Knell, R., Naish, D., Tomkins, J. L. & Hone, D. W. E. 2012. Sexual selection in prehistoric animals: detection and implications. Trends in Ecology and Evolution 28, 38-47.

- ., Naish, D., Tomkins, J. L. & Hone, D. W. E. 2013. Is sexual selection defined by dimorphism alone? A reply to Padian and Horner. Trends in Ecology and Evolution

Naish, D. 2001. Fossils explained 34: Crocodilians. Geology Today 17 (2), 71-77.

- . 2012. Birds. In Brett-Surman, M. K., Holtz, T. R. & Farlow, J. O. (eds) The Complete Dinosaur (Second Edition). Indiana University Press (Bloomington & Indianapolis), pp. 379-423.

Salisbury, S. W. & Naish, D. 2011. Crocodilians. In Batten, D. J. (eds). English Wealden Fossils. The Palaeontological Association (London). pp. 305-369.

Vremir, M., Kellner, A. W. A., Naish, D. & Dyke, G. J. 2013. A new azhdarchid pterosaur from the Late Cretaceous of the Transylvanian Basin, Romania: implications for azhdarchid diversity and distribution. PLoS ONE 8: e54268.

Witton, M. P. & Naish, D. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3: e2271.

- . & Naish, D. 2013. Azhdarchid pterosaurs: water-trawling pelican mimics or “terrestrial stalkers”? Acta Palaeontologica Polonica doi:

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

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