Although its evolutionary relationship to Tyrannosaurus Rex is already being overstated by the press--after all, it lived about 150 million years before its more famous descendant--the ancient theropod Tawa still counts as a major discovery. According to a new paper in the journal Science, this small (about 7 feet long), bipedal dinosaur lived 215 million years ago on the supercontinent Pangaea, which later split into North America, South America and Africa. Based on an analysis of its remains, Tawa--it's the Pueblo Indian name for a sun god--appears to have originated in South America, though its bones were found farther north, near the famous Ghost Ranch site in New Mexico that's yielded countless Coelophysis skeletons.

Will Tawa really cause paleontologists to rewrite the book of dinosaur evolution, as some breathless accounts surmise? Well, it's not as if bipedal, South American, meat-eating dinosaurs were rare on the ground--witness, for example, Herrerasaurus, which we already know lay at the root of the dinosaur family tree, not to mention those numerous (though native to North America) Coelophysis specimens. Like the Asian Raptorex, another recent discovery, Tawa is being described as a miniature T. Rex, though this seems (at least based on the information released so far) to be a gross oversimplification.

Over and above its presumed resemblance to T. Rex, what's important about Tawa is that it helps to clear up the evolutionary relationships, and ultimate origins, of the earliest theropods. With this missing piece of the fossil puzzle in place, the authors of the Science paper conclude that the very first dinosaurs evolved in South America in the early to middle Triassic period, then radiated out worldwide over the ensuing tens of millions of years.

In most ways a typical hadrosaur--or duck-billed dinosaur--of the Cretaceous period, Gryposaurus was distinguished by the prominent, arched bump on its nose, from which its name {"hook-nosed lizard") derives. Paleontologists speculate that this feature evolved as a sexually selected characteristic (i.e., males with bigger noses were more attractive to females), and the big schnozzes may also have been used for producing piercing sounds or butting other males.

By the way, the name Gryposaurus is often used interchangeably with Kritosaurus, but paleontologists now prefer the former (for reasons having to do with the reliability of fossil remains).

Read more about dinosaurs like Gryposaurus: Hadrosaurs - The Duck-Billed Dinosaurs

Illustration: Wikimedia Commons

It's not often that I'm taken aback by an off-the-cuff narrative blurb in a dinosaur TV special; after all, these extravaganzas are months in the making, rendering them not-quite-cutting-edge in terms of news. That's why I was shocked to hear, during last Sunday's otherwise unremarkable premiere of Clash of the Dinosaurs on the Discovery Channel, the idea that juvenile Sauroposeidon lunched on insects and small mammals to help them grow to adult size. Since Sauroposeidon was hardly special, as sauropods go, this implies that all sauropods were omnivorous at some stage in their life cycle.

My question is: really? The narrator of Clash tosses out this blurblet as if it's already widely accepted fact, but I could only find one (seemingly highly circumstantial) reference in the paleontology literature. (It's cited in this entry of the "World We Don't Live In" blog, a 2009 paper titled "The Implications of Sauropod Carnivory.") Clearly, conclusive proof of meat-eating sauropods would cause a seismic rumble in the insular world of paleontology and merit front-page coverage in, say, the New York Times. Is Discovery Channel pulling our collective legs, or do its producers know something we don't?

The relatively obscure Grippia--a three-foot-long ichthyosaur ("fish lizard") of the early to middle Triassic period--was rendered even moreso when the most complete fossil of this genus was destroyed in a bombing raid during World War II. What we do know for sure about this aquatic reptile is that it was fairly small as ichthyosaurs go, and that it was probably pretty much omnivorous in its undersea habitat (it was once believed that its jaws were specialized for crushing mollusks, but some paleontologists disagree).

Read more about marine reptiles like Grippia: Ichthyosaurs - The "Fish Lizards"

Illustration: Wikimedia Commons