My job at Impossible Pictures finished last week (though I am still doing the odd day here and there and am likely to go back to them in the future). Sigh, so much for digging myself out of that immense financial pit I’m still in. Anyway, today I start work on a new job involving… marine reptiles. I’ll say more about it in the future. Partly as a result of this, I post here another picture very kindly supplied by Mike Skrepnick, and used with his permission (image © Mike Skrepnick, used with permission). Created for a new mural at Dinosaur Provincial Park, it depicts a scene in the Campanian Bearpaw Sea. We can see a plioplatecarpine mosasaur, assorted sharks and ammonites, and the elasmosaurid plesiosaur Terminonatator ponteixensis, recently described by Sato (2003)…
Terminonatator – the name means ‘last swimmer’ – is so named as it is the youngest plesiosaur known from the sediments of the North American Western Interior (younger elasmosaurs are known from the western and eastern coasts of North America, as well as from Europe and elsewhere: see Mulder et al. (2000)). Its remains include a very nice articulated skull that is particularly interesting in preserving the impressions of various parts of the brain.
Marine reptiles – and in particular sauropterygians (plesiosaurs and their kin) – are another group that I’ve hardly touched at Tet Zoo, and again this is something I’d like to remedy (there is an article on Oxford Clay tetrapods at ver 1 here). Planned articles cover giant pliosaurs, leptocleidines, the salvation of Elasmosaurus, and placodonts. It would also be a good idea to cover the whole internal nostril thing: Cruickshank et al. (1991) proposed that plesiosaurs channelled water into the internal nostrils on the palate and ‘smelt’ the water while it moved through the olfactory chamber. The water would finally exit via the external nostrils on the dorsal surface of the snout. One key feature that led to the proposal of this ingenious system is that the internal nostrils of plesiosaurs are located closer to the snout tip than are the external nostrils*. It all sounds very good and this theory of ‘underwater sniffing’ has been largely accepted among marine reptile workers: there have been a few challenges to the model (Buchy et al. 2003), but they propose rather more radical interpretations of internal nostril function and don’t seem as likely.
* This is also true of some other sauropterygians, like placodonts. Consequently it has been argued that they also snorted in water via the internal nostrils for the purposes of olfaction (Rieppel 2001).
What makes Terminonatator really interesting, then, is that its internal nostrils are not located further forward than its external nostrils (Sato 2003, p. 95). I know that this is the case in at least one other plesiosaur too – so, were these taxa oddballs that didn’t rely on underwater olfaction, or had they developed some other solution to the problem? Thanks to Terminonatator‘s cerebral impressions, we know that it had an olfactory canal, and hence was presumably sniffing something – it wasn’t… err, what’s the name for things that lack a sense of olfaction? Is there such a word? [adjacent pic of Terminonatator skull borrowed from Adam Smith's The Plesiosaur Directory].
Oh dear, I’ve now said far too much. And hey… you see you can talk about plesiosaurs and not mention necks once. Many thanks for sharing the picture Mike. The picture shown here is – I presume – only one section of the whole mural.
Refs – -
Buchy, M.-C., Frey, E. “D.”, Métayer, F. & Salisbury, S. W. 2003. Slicing plesiosaurs, part II: plesiosaurs’ internal nares are no nares at all. In 1st EAVP Meeting (Basel, Switzerland), Abstract of Papers and Posters, With Programme. Natural History Museum Basel, p. 39.
Cruickshank, A. R. I., Small, P. G. & Taylor, M. A. 1991. Dorsal nostrils and hydrodynamically driven underwater olfaction in plesiosaurs. Nature 352, 62-64.
Mulder, E. W. A., Bardet, N., Godefroit, N., Godefroit, P. & Jagt, J. W. M. 2000. Elasmosaur remains from the Maastrichtian type area, and a review of latest Cretaceous elasmosaurs (Reptilia, Plesiosauroidea). Bulletin de l’Institut Royal des Sciences Naturelles de Belgique, Sciences de la Terre 70, 161-178.
Rieppel, O. 2001. The cranial anatomy of Placochelys placodonta Jaeckel, 1902, and a review of the Cyamodontoidea (Reptilia, Placodonta). Fieldiana, Geology (New Series) 45, 1-104.
Sato, T. 2003. Terminonatator ponteixensis, a new elasmosaur (Reptilia; Sauropterygia) from the Upper Cretaceous of Saskatchewan. Journal of Vertebrate Paleontology 23, 89-103.