Did Plants Make Feathered Dinosaurs Dumb?

Short answer, no.

Want to know more… by all means read on.

Today, colleagues from the University of Bristol, National University of Mongolia, Ohio University and I took aim at the doctor/patient confidentiality pact by publishing some very personal information on a research subject of ours.  Fortunately, I don’t think this particular patient is going to get their feathers ruffled about it.  Turns out, paleontologists are smarter than we often get credit for.  In fact, we’ve got this whole messy doctor/patient thing figured out… just work on patients that are already dead… in this case, for over 90 million years.

copyright Mark Anderson www.andertoons.com
copyright Mark Anderson http://www.andertoons.com

One fortuitous day, we got the chance to do just that.  The only good skull of a rare and whacky group of theropod dinosaurs known as Therizinosauria made the trek from Mongolia to the UK on holiday.  While there, UK paleontologists realized that the skull of the therizinosaur Erlikosaurus was REALLY, REALLY, REALLY, overdue for its check-up.  So they took Erlikosaurus’s head to a CT scanning facility for its 90 million year annual physical.

The fossilized skull of Erlikosaurus andrewsi from the Cretaceous of Mongolia
The fossilized skull of Erlikosaurus andrewsi from the Cretaceous of Mongolia

Why Erlikosaurus?  Well, for starters, therizinosaurs are downright weird animals, which makes them really interesting to weird people (erg.. uh.. cough.. I mean “scientists”). Although they are theropods and therefore cousins of bloodthirsty predators like Velociraptor, therizinosaurs were clearly not taking a bite out of anyone.  Sometimes it is hard to envision an advanced therizinosaur like Erlikosaurus as doing anything at all, other than finding a nice soft spot in the Cretaceous landscape to pop a squat and eat all day long.  A quick run down of the therizinosaur anatomy makes this blaringly evident.  These guys had tiny heads, tightly packed minuscule teeth, long necks, stocky legs with fat feet, hand claws up to four feet long, and giant bloated bellies. They also reached enormous body sizes up to 13,000 lbs. When I was in grad school I used to get this point across by comparing therizinosaurs to a cross between a gorilla, an ostrich, and Edward Scissorhands.  If you ask me, the analogy is still apropros.

Luis Rey's vision of what an advanced therizinosaur looked like in the flesh.
Luis Rey’s vision of what an advanced therizinosaur looked like in the flesh.
How to build a therizinosaur 101.
How to build a therizinosaur 101.

The question is… did the loss of predatory behavior coincide with a loss of smarts and a loss of sensory capabilities in therizinosaurs?  No one knew. By CT scanning the skull, we were able to reconstruct soft tissue of the brain and inner ear of Erlikosaurus and tackle this intriguing question.  The result?  Despite its rather slow appearance, Erlikosaurus was not a dumb as a box of rocks.  Although, these kind of estimates are admittedly crude, it seems as if Erlikosaurus was just a bit shy on the intelligence scale when compared to early birds, but likely a bit ahead of the great hunter T. rex.  Pair this with the fact that Erlikosaurus had above average hearing capabilities for an animal its size and a higher than predicted sense of smell, and suddenly therizinosaurs don’t seems as dimwitted as…. well, as they look.

Scans did reveal that one Erlikosaurus sense could’ve benefited from some improvement–its vision, which probably wasn’t the best.  Whatever these guys were eating, they were likely munching in the pure light of day.

Reconstructed soft tissues in the head of Erlikosaurus: brain (blue), cranial nerves (yellow), and inner ear (pink).
Reconstructed soft tissues in the head of Erlikosaurus: brain (blue), cranial nerves (yellow), and inner ear (pink).

The implications are interesting. Despite leaning toward vegetarianism, therizinosaurs seem to have kept the keen sensory toolkit they inherited from their predatory ancestors.  All of which means that the brainpower and good senses of therizinosaurs had more to do with their place on the family tree as close cousins to birds than their dietary preference.  Its also good to know that, should you ever encounter Erlikosaurus as a result of, say a time machine fluke, it could hear your terrified whimpers but would be kind enough not to eat you.  (Just don’t sneak up on it at night or you could lose an eye).

Couldn’t say the same about T. rex.

The paper “The Endocranial Anatomy of Therizinosauria and its Implications for Sensory and Cognitive Function” by S. Lautenschlager, E. Rayfield, P. Altangerel, L. Zanno, and L. Witmer, is freely available to the public via the journal PLoS ONEhttp://dx.plos.org/10.1371/journal.pone.0052289

3 thoughts on “Did Plants Make Feathered Dinosaurs Dumb?”

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