Dinosaurs From Space! (OK, Not Really)

We spend a lot of time on ScienceLife talking about human disease and intricate biological research, so it’s important to take a break every once in a while and stir the inner 8-year-old in all of us with one glorious word: DINOSAURS!

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Woah! That fine illustration by artist Jorge Gonzalez depicts three Triassic carnivores, the uppermost of which is Tawa hallae, a new species described last week in the journal Science as a sort of uniter-not-divider of early dinosaurs. Appearances to the contrary, Tawa hallae did not fly in from outer space to invade the Earth 215 million years ago, but the unusual features revealed by a complete fossil found in New Mexico in 2006 have prompted reconsideration of the dinosaur evolutionary tree and theories about how far early dinosaurs traveled across the super-continent of Pangea.

The University of Chicago can claim several A-list paleontologists, such as Paul Sereno and Neil Shubin, on faculty, but our representative on the Tawa hallae paper showcases the importance of educating future stars of the field – Nathan Smith, a graduate student in the evolutionary biology program and a research associate at Chicago’s Field Museum. Smith was involved in the dig, at New Mexico’s famous Ghost Ranch, that uncovered a nearly complete Tawa skeleton and bones from six other members of the species, as well as the analysis of the skeleton, which places it as a relative of several species formerly thought to be weird cousins of dinosaur evolution.

Probably the most famous of those cousins was Herrerasaurus, a species discovered in Argentina 45 years ago. To the untrained eye, Herrerasaurus sure looks like a dinosaur, but due to some irregularities in its skull and pelvis, was classified by some as different enough to be outside of the dinosaur family. In order to conclusively rope the Herrerasaurus back into the evolutionary history of dinosaurs, paleontolgists needed to find a fossil that contained some features of Herrerasaurus alongside features of theropods, one of the three major early groups of dinosaurs.

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Illustration by Jorge Gonzalez

Tawa hallae, named after the Puebloan sun god and paleontologist Ruth Hall, fits that profile nicely, according to the Science paper. Sharing many features with the Herrerasaurus, another species called Eoraptor, and the neotheropods, Tawa fills in some of the gaps in the fossil record and makes a tree inclusive of these weird cousins more sensible. Tawa also shares a few features, such as hollow bones, with modern birds – more evidence that carnivorous dinosaurs live on today as our avian friends.

The new tree also lends support to the idea that these dinosaurs were pretty mobile back in the days when all the continents were nestled together as one. While the hotspot of dinosaur evolution in the late Triassic period appears to have been South America, new species then dispersed to what we now know of as North America and Africa – a much easier trip in Pangea days. Another group of dinosaurs, the long-necked suaropodomorphs, did not travel so widely, a difference that suggests ecological factors, not geological barriers, prevented the movement of some dinosaurs.

If two dimensions aren’t enough to satisfy your thirst for dinosaur knowledge, the Tawa discovery is featured as part of a 3-D film called Dinosaurs Alive!, currently playing at the Field Museum. You can also listen to a Science podcast interview with the paper’s first author, Sterling Nesbitt.

“Our Ghost Ranch project is featured in the first half of that film, and the fossil jackets that are seen during the film being hauled out of the ground in 2006 actually contain this new species of dinosaur,” Smith told my colleague Greg Borzo. “This is one of the most primitive and most complete early dinosaurs ever found, so it will be invaluable in shedding light on dinosaur origins and early evolution.”

About Rob Mitchum (526 Articles)

Rob Mitchum is communications manager at the Computation Institute, a joint initiative between The University of Chicago and Argonne National Laboratory.

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