Figure 1. Click to enlarge. Four large Tanystropheus specimens in situ and roughly reconstructed. The human silhouette is 6 feet (1.8m) tall. In situ images from Wild 1974. Note the presence and absence of epipubic bones along with the variation in skull size.
Tanystropheus (Fig. 1, Middle Triassic, Europe, von Meyer 1852) was discovered in the 19th century, but not fully realized for what it was until Peyer 1931. One early specimen, named Tribelesodon, was mistaken for a pterosaur (Basani 1886, Arthaber 1921, Von Nopcsa 1923). The long neck bones were mistakenly compared to wing bones. The foot, with its long p5.1 digit, were indeed very pterosaurian in general morphology. So the taxonomic mistake had some basis.
Lesson learned here:
respected scientists can make mistakes. And these mistakes can become traditions until falsified. A reconstruction might have helped.
New complete skeletons of Tanystropheus described by Peyer (1931) solved the basic problem by showing the hyper-elongate bones actually belonged between the skull and torso.
In 1974 Rupert Wild reviewed all the available material (27 specimens) of T. langobardicus. A few are pictured above (Fig. 1). Before the advent of phylogenetic analysis, Wild had the insight to label them Reptilia > Lepidosauria > Squamata > Lacertilia > Tanysitrachelida > Tanystropheidae. This is largely confirmed by the present large reptile tree. (The term “Lacertilia” includes all lizards, but not snakes, so it is a paraphyletic taxon in the large reptile tree. The term “Tanysitrachelida” (Peyer 1931) is no longer in use. Tanystropheidae includes other long-necked reptiles, such as Langobardisaurus, Pteromimus, Tanytrachelos and Amotosaurus, all very much smaller taxa.)
To his credit,
Wild (1978) also was among the first to promote the idea that pterosaurs were not archosaurs, but something else along the lines of an eosuchian, a term little used today. Back then an Eosuchian was commonly considered a basal diapsid, like Youngina, a genus then considered close to the ancestry of both lepidosaurs and archosaurs. Now, thanks to the large reptile tree, we know that lepidosaurs and archosaurs are not related, except at a very basal reptile level. We also know that diapsids are diphyletic, having two origins. Wild’s heretical break with tradition is to be applauded. At the time closer relatives to pterosaurs, like Langobardisaurus, Cosesaurus, Sharovipteryx and Longisquama were either unknown or just becoming known.
(Carroll 1989, etc.) placed Tanystropheus outside the Archosauriformes along with rhynchosaurs, which makes absolutely no sense. Still others (Renesto 2005 following tradition) placed Tanystropheus within the Protorosauria, which makes more sense, but, unfortunately, this is by untested tradition only.
Phylogenetic testing using more taxa in the large reptile tree clarifies relationships. Tanystropheidae nest between Huehuecuetzpalli + Macrocnemus and Cosesaurus within the Tritosauria, outside of the Squamata.
Despite what Wikipedia tells you, phylogenetic analysis recovers Dinocephalosaurus as a convergent form derived from Macrocnemus, not directly related to Tanystropheus despite the roughly similar appearance and size.
Earlier we looked at several solutions to the niche and posture of Tanystropheus. Here you can see the ancestry and sisters of Tanystropheus.
Here (fig. 1) we can see that some large Tanystropheus specimens had a larger skull. Others had a smaller skull. Some had epipubic bones. Others did not. More precision in creating the reconstructions might someday reveal other differences not readily visible in these roadkill fossils.
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Li C 2007. A juvenile Tanystropheus sp.(Protoro sauria: Tanystropheidae) from the Middle Triassic of Guizhou, China. Vertebrata PalAsiatica 45(1): 37-42.
Meyer H von 1847–55. Die saurier des Muschelkalkes mit rücksicht auf die saurier aus Buntem Sanstein und Keuper; pp. 1-167 in Zur fauna der Vorwelt, zweite Abteilung. Frankfurt.
Nosotti S 2007. Tanystropheus longobardicus (Reptilia, Protorosauria: Reinterpretations of the anatomy based on new specimens from the Middle Triassic of Besano (Lombardy, Northern Italy). Memorie della Società Italiana di Scienze Naturali e del Museo Civico di Storia Naturale di Milano, Vol. XXXV – Fascicolo III, pp. 1-88
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Renesto, S. 2005. A new specimen of Tanystropheus (Reptilia Protorosauria) from the Middle Triassic of Switzerland and the ecology of the genus. Rivista Italiana di Paleontologia e Stratigrafia, 111(3): 377–394.
Wild R 1973. Die Triasfauna der Tessiner Kalkalpen XXIII. Tanystropheus longobardicus(Bassani) (Neue Ergebnisse). – Schweizerische Paläontologische Abhandlungen 95: 1-16.
Wild R 1978. Die Flugsaurier (Reptilia, Pterosauria) aus der Oberen Trias von Cene bei Bergamo, Italien. Bolletino della Societa Paleontologica Italiana 17(2): 176–256.