Tanystropheidae in the sw usa – svp abstracts 2013
From the abstract
Pritchard et al. 2013 wrote: “Tanystropheids are a clade of long-necked archosauromorphs whose remains are largely restricted to marine deposits from the Triassic of Europe and Asia and almost entirely known from two-dimensionally crushed skeletons. Thus far, the occurrences of Tanytrachelos along the East Coast of the United States represent the westernmost confirmed record of tanystropheids, although unconfirmed isolated fragments have been referred tentatively to the group from localities in western North America.
“A large sample of well-preserved, three-dimensional tanystropheid fossils from the Hayden Quarry in the Upper Triassic Chinle Formation of New Mexico provides new insight into the anatomy, phylogeny, and paleoecology of Tanystropheidae. A newly constructed phylogenetic analysis of 200 characters and 45 diapsids, early archosauromorphs, and archosauriforms recovers a novel topology for basal Archosauromorpha. Tanystropheidae forms the sister taxon of a clade including Trilophosaurus, Prolacerta, and Archosauriformes. The analysis also recovers a novel subclade of small tanystropheids including Langobardisaurus and Tanytrachelos. Numerous apomorphies, including dorsoventrally flattened cervical centra and a number of tarsal characters, indicate that the Hayden Quarry tanystropheid materials belong to this subclade. Protorosaurus is recovered as the earliest diverging archosauromorph, outside of Tanystropheidae, and Prolacerta nests as the sister taxon to Archosauriformes.
“These results support the hypothesis that a long necked “protorosaur” bauplan was ancestral for archosauromorphs. Tanystropheid apomorphies identified in this analysis were subsequently used to recognize additional Norian-aged fossils from other sites in New Mexico, Arizona, and Texas. Some of these fossils had previously been attributed to drepanosaurs. The estimated body size range of western tanystropheids based on comparison with Tanytrachelos (~0.3 meters–2.0 meters) indicates that the group was a taxonomically and ecologically diverse component of western North American ecosystems. The presence of tanystropheids throughout western North America, a region that was only seasonally wet during the Norian and Rhaetian suggests that tanystropheids could adapt to a far wider range of habitats than previous records indicate.”
First of all
It’s great to see that little tanystropheids made it to SW America, along with those desert drepanosaurids.
Figure 1. Tanystropheus and kin going back to Huehuecuetzpalli. Apparently only forms close to Langobardisaurus and Tanytrachelos were discovered at the Hayden Quarry.
Second of all
This presumption of an archosauromorph nesting of lepidosaurs has to stop! Pritchard et al. are beating a dead horse. A larger spectrum of reptiles reveals that tanystropheids, many with ossified sterna, by the way, are lepidosaurs. This can be tested simply by including taxa, nor excluding them.
To their credit
Protorosaurus and Prolacerta do indeed belong at the base of the Archosauriforms. They have long necks by convergence with tanystropheids.
However
These results do indeed support the hypothesis that a long necked “protorosaur” bauplan was ancestral for archosauromorphs. But I hope they’re not excluding the real sister taxa, like Youngina and Thadeosaurus. And bizarre bauplans, like tanystropheids, are almost always terminal, not ancestral.
References
Pritchard A, Nesbitt S, Turner A, Irmis R Smith N 2013. Morphology and systematics of the reptile clade Tanystropheidae: implications for Late Triassic biogeography and early archosauromorph evolution. Journal of Vertebrate Paleontology abstracts 2013.
Source: http://pterosaurheresies.wordpress.com/2013/11/06/tanystropheidae-in-the-sw-usa-svp-abstracts-2013/
