Ancient creature forces new look at dinosaurs
The 245-million-yearold fossils were some of the strangest ones Sterling Nesbitt had ever seen. Their bodies looked like crocodiles — stout and muscular, with four sturdy legs. But their necks and tails were unusually long, and the bones bore certain markings only found in dinosaurs.
The fossils definitely didn’t belong to any creature known to science. But Nesbitt knew of an oddball animal that would fit these fossils perfectly: Teleocrater rhadinos, an ancient reptile discovered in Tanzania in the 1930s but never formally classified. Nesbitt had seen teleocrater’s skeleton displayed in the London Natural History Museum years ago.
Now, standing amid swaying grasses and piles of upturned soil at a fossil site not far from where the original bones were discovered, gazing at the remains of three new specimens, Nesbitt knew he was looking at the same creature.
This time, he and his colleagues had enough material to figure out how teleocrater fits into the evolutionary family tree. It is the oldest known branch on the lineage that would eventually lead to dinosaurs, they report Wednesday in the journal Nature.
To the untrained eye, teleocrater looks no stranger than any other dinosaur, but experts say its body plan is extremely unusual for an ancient reptile. The freaky newfound species is forcing paleontologists to rethink how dinosaurs evolved.
Nesbitt, a vertebrate paleobiologist at Virginia Tech, is an expert on the rise of a group of animals called archosaurs. Around 250 million years ago, that group diversified into two lineages — one led to today’s crocodiles, the other led to the “avemetatarsalins,” which included dinosaurs and eventually birds.
Phylogenetic analysis, which compares traits of various species to figure out how they relate to one another, suggests that teleocrater is a very early branch on the avemetatarsalin lineage. It’s not a direct ancestor of dinosaurs (teleocrater’s lineage eventually went extinct). Instead, it’s more like an older cousin — one with a deep knowledge of family history and a proclivity for gossip. It can tell scientists quite a lot about dinosaurs’ murky past.
“Given their position on the family tree, they give us a good idea of what the common ancestor of all bird line archosaurs was like,” said Ken Angielczyk, a paleontologist at the Field Museum in Chicago and a co-author on the study. “If we want to understand how the very distinctive dinosaur and bird body plan evolved into something that’s very successful ... teleocrater provides insight into the first step in that process.”
The teleocrater discovery comes in the wake of a recent phylogenetic study that challenged scientists’ understanding of the order in which dinosaurs diversified. That research, published in Nature last month, suggested that dinosaur family groupings needed to be reorganized and renamed and that dinosaurs arose in a completely different part of the world than originally thought.
“It’s almost a one-two punch,” Nesbitt said of the two new studies. “It’s complicated the once-simple picture of how dinosaurs got their features.”