Chilesaurus Is So Weird, They Call It The "Platypus Of Dinosaurs"

You know what's cool about dinosaurs? Everything. But more specifically, we always thought it was amazing how different they all were from each other. On the one hand, you've got critters like tyrannosaurus and velociraptor — there's a size difference, sure, but you can see how the follow the same basic two-legged, long-tailed, sharp-toothed design. But on the other hand, you've got triceratops, stegosaurus, and brontosaurus. It's hard to believe they're related to each other, let alone any of the meat-eaters. Stranger still, back in 2015, they dug up Chilesaurus diegosuarezi (discovered by 7-year-old Diego Suarez), and it seemed to combine features from across the spectrum of species — one guess why they call it the "platypus of dinosaurs."

A Hodgepodge Of Parts

So, broadly speaking, there are two main families of dinosaurs, and we're just going to go with "Land Before Time" terminology to help keep everything straight. Saurischians were divided into sauropods (like Littlefoot) and meat-eating theropods (like Sharptooth), and their defining characteristic was their lizard-like hips — "saurischian" actually means "lizard-hipped". On the other side were the ornithischian ("bird-hipped") dinosaurs, a very diverse collection of plant-eating dinosaurs that included triceratops (Sarah), stegosaurus (Spike), and hadrosaurs (Duckie).

And then there's the turkey-sized chilesaurus. Like a theropod, it stood on two legs and had short but powerful forearms. Like a sauropod, it had a long neck, flat teeth, and broad feet. And like a ornithischian, it had bird-like hips. Usually, paleontologists in doubt could just consult the hips and put it in the appropriate category. With such a hodgepodge of parts, though, they ended up putting these bird-hips with the theropods in the lizard-hip family. But they didn't feel great about it — and a closer inspection has called the entire hip-based categorization into question.

Hips Don't Lie

The whole "putting a bird-hip with the lizard-hips" thing never sat right with scientists, and this year, a new report has scrubbed that initial analysis away once and for all. Shakira was right, the hips don't lie. But they might not tell the whole story, either. Chilesaurus was an ornithischian — and maybe it was related to theropods too. See, this March, we began to realize that, despite their similar hips, Sharptooths and Littlefoots might not be in the same family after all. Instead, T-rex and the gang split off from Sarah, Spike, and Duckie's family tree.

Following along? That means that Chilesaurus's strangest mixes aren't a combo of three different groups, but only two. And that means that little Diego Suarez didn't find an impossible puzzle. He found a missing link — a dinosaur that points to the spot where two great dynasties (dino-sties?) split apart.

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Written by Reuben Westmaas August 17, 2017

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