Two ways to be an herbivorous dinosaur

[Halichoeres]

This paper is a cool demonstration that your evolutionary past can constrain your evolutionary future. Ornithischian and saurischian dinosaurs were both very diverse groups with lots of herbivorous members, and they showed distinct but repeated trends when it came to evolution of their skulls and guts. This paper constructs a sort of index of several traits associated with herbivory and shows that, in ornithischians, most of the relevant evolution pertains to initial food processing, like stronger jaws and greater cheek tooth density. Meanwhile, in both sauropodomorphs and various herbivorous theropod groups, most of the relevant evolution had to do with modifications of the gut, while the jaw actually tended to grow weaker and oral processing of food diminished.

A visual summary of trends in saurischian herbivores:


And trends in ornithischian herbivores:


Button & Zanno, Current Biology (paywall): https://www.cell.com/current-biology/pdfExtended/S0960-9822(19)31390-9

[Ravonium]

Quite a good topic to do a study on; this is definitely the most interesting of the recent 'big stories' in paleontology

[Libraraptor]

Interesting paper. I always wonder, too, if there were carnivorous Ornithischians?

[stargatedalek]

Interesting paper. I always wonder, too, if there were carnivorous Ornithischians?

I don't think there is anything conclusive, but many that rely heavily on beaks have been long presumed to be potential omnivores.

[Halichoeres]

Some hadrosaur coprolites seem to have had pieces of crab carapace in them. Like modern herbivores, many ornithischians probably supplemented a mainly plant-based diet with animals, maybe to get minerals or other nutrients.

https://www.nature.com/news/fossilized-poo-reveals-that-vegetarian-dinosaurs-had-a-taste-for-crabs-1.22649

[austrosaurus]

Some hadrosaur coprolites seem to have had pieces of crab carapace in them. Like modern herbivores, many ornithischians probably supplemented a mainly plant-based diet with animals, maybe to get minerals or other nutrients.

https://www.nature.com/news/fossilized-poo-reveals-that-vegetarian-dinosaurs-had-a-taste-for-crabs-1.22649

While herbivorous dinosaurs almost definitely supplemented their diet on occasion, I think that an equally likely explanation for this particular scenario is that it was simply a case of wrong place, wrong time for the poor crabs.