Nav: Home

Some extinct crocs were vegetarians

June 27, 2019

Based on careful study of fossilized teeth, scientists Keegan Melstom and Randall Irmis at the Natural History Museum of Utah at the University of Utah have found that multiple ancient groups of crocodyliforms--the group including living and extinct relatives of crocodiles and alligators--were not the carnivores we know today, as reported in the journal Current Biology on June 27. In fact, the evidence suggests that a veggie diet arose in the distant cousins of modern crocodylians at least three times.

"The most interesting thing we discovered was how frequently it seems extinct crocodyliforms ate plants," said Keegan Melstrom, (@gulosuchus) a doctoral student at the University of Utah. "Our study indicates that complexly-shaped teeth, which we infer to indicate herbivory, appear in the extinct relatives of crocodiles at least three times and maybe as many as six."

All living crocodylians possess a similar general body shape and ecology to match their lifestyle as semiaquatic generalist carnivores, which includes relatively simple, conical teeth. It was clear from the start of the study that extinct species showed a different pattern, including species with many specializations not seen today. One such specialization is a feature known as heterodonty: regionalized differences in tooth size or shape.

"Carnivores possess simple teeth whereas herbivores have much more complex teeth," Melstrom explained. "Omnivores, organisms that eat both plant and animal material, fall somewhere in between. Part of my earlier research showed that this pattern holds in living reptiles that have teeth, such as crocodylians and lizards. So these results told us that the basic pattern between diet and teeth is found in both mammals and reptiles, despite very different tooth shapes, and is applicable to extinct reptiles."

To infer what those extinct crocodyliforms most likely ate, Melstrom and his graduate advisor, chief curator Randall Irmis, compared the tooth complexity of extinct crocodyliforms to those of living animals using a method originally developed for use in living mammals. Overall, they measured 146 teeth from 16 different species of extinct crocodyliforms.

Using a combination of quantitative dental measurements and other morphological features, the researchers reconstructed the diets of those extinct crocodyliforms. The results show that those animals had a wider range of dental complexities and presumed dietary ecologies than had been appreciated previously.

Plant-eating crocodyliforms appeared early in the evolutionary history of the group, the researchers conclude, shortly after the end-Triassic mass extinction, and persisted until the end-Cretaceous mass extinction that killed off all dinosaurs except birds. Their analysis suggests that herbivory arose independently a minimum of three times, and possibly six times, in Mesozoic crocodyliforms.

"Our work demonstrates that extinct crocodyliforms had an incredibly varied diet," Melstrom said. "Some were similar to living crocodylians and were primarily carnivorous, others were omnivores and still others likely specialized in plants. The herbivores lived on different continents at different times, some alongside mammals and mammal relatives, and others did not. This suggests that an herbivorous crocodyliform was successful in a variety of environments!"

Melstrom says they are continuing to reconstruct the diets of extinct crocodyliforms, including in fossilized species that are missing teeth. He also wants to understand why the extinct relatives of crocodiles diversified so radically after one mass extinction but not another, and whether dietary ecology could have played a role.
-end-
This research was supported by the US National Science Foundation, the Welles Fund from the University of California Museum of Paleontology and the University of Utah Department of Geology & Geophysics Chapman Fund.

Current Biology, Melstrom and Irmis: "Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs" https://www.cell.com/current-biology/fulltext/S0960-9822(19)30690-6 DOI: 10.1016/j.cub.2019.05.076

Current Biology (@CurrentBiology), published by Cell Press, is a bimonthly journal that features papers across all areas of biology. Current Biology strives to foster communication across fields of biology, both by publishing important findings of general interest and through highly accessible front matter for non-specialists. Visit: http://www.cell.com/current-biology.

University of Utah

Related Diet Articles:

Poor diet can lead to blindness
An extreme case of 'fussy' or 'picky' eating caused a young patient's blindness, according to a new case report published today [2 Sep 2019] in Annals of Internal Medicine.
New research on diet and supplements during pregnancy and beyond
The foods and nutrients a woman consumes while pregnant have important health implications for her and her baby.
Special issue: Diet and Health
Diet has major effects on human health. In this special issue of Science, 'Diet and Health,' four Reviews explore the connections between what we eat and our well-being, as well as the continuing controversies in this space.
Should you eat a low-gluten diet?
When healthy people eat a low-gluten and fiber-rich diet compared with a high-gluten diet they experience less intestinal discomfort including less bloating which researchers at University of Copenhagen show are due to changes of the composition and function of gut bacteria.
If your diet fails, try again; your heart will thank you
Risk factors for cardiovascular disease closely track with changes in eating patterns, even only after a month or so.
The brain diet
Scientists at the Medical University of South Carolina (MUSC) find that high levels of a hormone called FGF23 are linked to changes in brain structure.
You are never too old for the Mediterranean diet
The Mediterranean diet as a secret of long life for elderly.
Getting to the roots of our ancient cousin's diet
Since the discovery of the fossil remains of Australopithecus africanus from Taung nearly a century ago, and subsequent discoveries of Paranthropus robustus, there have been disagreements about the diets of these two South African hominin species.
A diverse diet may not be the healthiest one
Scientific evidence to date does not support the notion that eating a diverse diet is healthy or promotes a healthy weight.
How was Mediterranean diet associated with severity of psoriasis?
Adherence to a Mediterranean diet, an eating plan filled with fruits and vegetables, legumes, cereals, bread, fish, fruit, nuts and extra-virgin olive oil, may be associated with the severity of the skin condition psoriasis.
More Diet News and Diet Current Events

Top Science Podcasts

We have hand picked the top science podcasts of 2019.
Now Playing: TED Radio Hour

In & Out Of Love
We think of love as a mysterious, unknowable force. Something that happens to us. But what if we could control it? This hour, TED speakers on whether we can decide to fall in — and out of — love. Guests include writer Mandy Len Catron, biological anthropologist Helen Fisher, musician Dessa, One Love CEO Katie Hood, and psychologist Guy Winch.
Now Playing: Science for the People

#542 Climate Doomsday
Have you heard? Climate change. We did it. And it's bad. It's going to be worse. We are already suffering the effects of it in many ways. How should we TALK about the dangers we are facing, though? Should we get people good and scared? Or give them hope? Or both? Host Bethany Brookshire talks with David Wallace-Wells and Sheril Kirschenbaum to find out. This episode is hosted by Bethany Brookshire, science writer from Science News. Related links: Why Climate Disasters Might Not Boost Public Engagement on Climate Change on The New York Times by Andrew Revkin The other kind...
Now Playing: Radiolab

Breaking Bongo
Deep fake videos have the potential to make it impossible to sort fact from fiction. And some have argued that this blackhole of doubt will eventually send truth itself into a death spiral. But a series of recent events in the small African nation of Gabon suggest it's already happening.  Today, we follow a ragtag group of freedom fighters as they troll Gabon's president - Ali Bongo - from afar. Using tweets, videos and the uncertainty they can carry, these insurgents test the limits of using truth to create political change and, confusingly, force us to ask: Can fake news be used for good? This episode was reported and produced by Simon Adler. Support Radiolab today at Radiolab.org/donate.