Paleontology Newsflash: Elessaurus gondwanoccidens

Let him go or I'll fossilize you, Longshanks!

 

 

This newly discovered Triassic reptile fossil doesn't come from a dinosaur, but it does foreshadow a new addition that will be joining the park in the near future. Say hello to Elessaurus!

  • Perhaps the most important thing to know up front about this new discovery is that it consists of a leg and an incomplete hip. That limits what we can know about this taxon, but it does tell us some helpful things about Elessaurus and its closest relatives. And while the preservation might not look too hot, it was preserved in mostly natural articulation, which solves many problems for paleontologists.

  • Cladistic analyses suggest Elessaurus is a close relative of the earliest members of the tanystropheids. Just what are tanystropheids besides a bizarre name for an ancient reptile group? Well, their bizarre name fits this bizarre group of semi-aquatic reptiles. Picture a lizard with a fishing pole for a neck, and that image will fit what we know of most of the group, at least by appearance. They're not lizards, but early forerunners of the archosaurs, a group that includes crocodiles, pterosaurs, dinosaurs, birds, and a host of other bizarre reptilians. They all lived during the Triassic period, a time when Nature seems to have lost its mind a little after the End Permian extinction—by far the worst extinction event in Earth's history—and just started experimenting with bizarre things it could make reptilians do. The Triassic saw some of the strangest reptile groups come and go: giant lizards with cow horns, vegetarian crocodiles, lizards with legs for wings, and that's just for starters. Many of these reptile groups, including the tanystropheids, did not survive to modern times, making them seem all the more bizarre for their unfamiliarity. And just to drive the point home, I'll say it once more: the tanystropheids are bizarre. Since no living animal employs a survival strategy that stretches the neck to such an extreme as seen in the tanystropheids, we can't put together a good picture of their habits or their role in their ecology. If Elessaurus really is a close relative of the tanystropheids' ancestor, this could clear up several points about their lifestyle and explain why they got so bizarre. Maybe if we understood that, they would become less bizarre and spare science writers from having to use  . . . that word! . . . so much when describing them.

  • One thing to know about cladistics before returning to Elessaurus: cladistics groups organisms according to shared derived characters, or body features that they "invented" and which ought to be found in their descendants. Evolution doesn't always work that way, but this system is currently the best one we have for charting evolutionary history. Sometimes it leads to some counter-intuitive results: all animal groups with skeletons that lived on land at some point in their history (A.K.A. tetrapods) inherited that skeleton from a group called euteleostomi, A.K.A Bony Fish. Since cladistics considers descendant groups to be members of the same group as the ancestral lineage, that means you're a Bony Fish, your pet bird's a Bony Fish, and the frogs' legs you ate last Mardi Gras belonged to a Bony Fish, cladistically speaking. Even groups that gave up one or more of those defining derived characters still belong to the ancestral clades; thus even some fish groups that gave up on growing bony skeletons and went back to the old cartilage design count as . . . you guessed it! BONY FISH. I won't use that word to describe the system, but as strange as some of its groupings may seem, it's a reasonable approximation of evolutionary history that gives us some insight into how and why life on our planet includes so much variety. In short, expect to find strange bedfellows in evolutionary history, especially when we try to chart that history. Much of what makes Elessaurus significant relies on its place in evolutionary history and what it tells us about other groups. It's a bum rap, but them's the breaks when you're dealing with a fossil record full of huge, gaping holes.

  • As an early member of the archosaur predecessor group (so to speak) archosauromorpha, Elessaurus incorporates derived characters in its hind leg design that formed the groundwork for increasingly efficient designs for walking in later archosaur groups, including the high walk of crocodiles and the fully upright strut of birds and dinosaurs. Superficially, its hind legs looked like a lizards, but certain bone shapes indicate it had reworked and reemphasized some of the muscle groups to improve its locomotion.

  • Rocks from the Early Triassic, older than most known tanystropheids, preserved Elessaurus' fossils. Analysis of these rocks suggest Elessaurus preferred a much more arid environment than its later tanystropheid cousins. The overall geology of the area suggests it suffered from constant flash floods that scoured the surrounding land into a sort of dry floodplain, and Elessaurus may have already incorporated fish into its diet. More fossils from different parts of Elessaurus' body and further testing will be needed to clarify just what it did with its time, though, but whatever that was, its environment was encouraging the Elessaurus population to do something vaguely tanystropheid with its legs. Of course, this begs the question of what tanystrophieds did with their legs. Studies of the most extreme member of the tanystropheid clan, the namesake Tanystropheus itself, argue that it used some of those shared derived characters to latch onto rocks for leverage in moving its fishing-rod neck about. That's a pretty specialized function, so whatever walking innovations Elessaurus used in its deserty environment were probably co-opted in part for a different function in the water-loving tanystrophieds when the environment presented some unique ecological opportunities to animals with that leg design. Certainly more efficient walking came in handy for the tanystropheids, since by the Late Triassic they had spread from New Mexico to Italy to eastern China (which were all connected way back then).

  • If you're wondering why a butchered still from The Lord of the Rings opens this report, it's because Elessaurus represents one of the geekiest scientific names in recent memory, and that includes the dinosaurs Zuul and Thanos, and the louse Strigiphilus garylarsoni. In a near pun of epic proportions, the describers of Elessaurus cobbled the name together like this: " Genus named after Elessar, meaning ‘elf-stone’ in the fictional language Quenya, created by J.R. R. Tolkien. In Tolkien’s Middle Earth universe, Elessar Telcontar is the name chosen by king Aragorn II, who, by his turn, is also known as Strider or ‘longshanks’. The comparatively long zeugopodium of UFSM 11471 makes it a long-shanked animal, justifying the name. Termination -saurus from Greek, meaning ‘lizard’. Species name derived from the supercontinent Gondwana and the Latin adjective occidens, ‘from west’, in a reference to the locality from where the new species was recovered" (De-Oliveira 2020). Isn't that just gloriously geeky?! And to flash my own geek credentials (I was a teaching assistant for a Tolkien class in college), the reference to west in the species name isn't just geographically apropos, it fits the literary reference as well. Aragorn's ancestors emigrated to Middle Earth from an island known as Numenor—a Tolkienian version of Atlantis in some ways—whose people were known as "Men of the West." Elessaurus is truly an Archosauromorph of the West . . . which doesn't have quite the same poetic ring to it, but that's scientific parlance for ya.

           

De-Oliveira TM, Pinheiro FL, Stock Da-Rosa ÁA, Dias-Da-Silva S, Kerber L (2020) A new archosauromorph from South America provides insights on the early diversification of tanystropheids. PLoS ONE 15(4): e0230890.

 

Renesto S, Saller F. Evidences for a semi aquatic life style in the Triassic diapsid reptile Tanystropheus. Riv. It. Paleontol. Strat. 2018; 124:23–34.

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