Paleontologists have found the fossilized remains of a small mammal foot preserved inside the body cavity of the holotype specimen of Microraptor zhaoianus, a species of small feathered dinosaur that lived during the Early Cretaceous epoch, some 120 million years ago. The discovery adds to the known diversity of diet for the Microraptor genus, which also consumed birds, fish, and lizards.
Life reconstruction of Microraptor zhaoianus eating the foot of a small mammal. Image credit: Ralph Attanasia III.
Microraptor zhaoianus lived in what is now China about 120 million years ago (Early Cretaceous epoch).
This dromaeosaurid dinosaur was about the size of a pigeon and had long feathers on its arms and legs.
The animal was likely gliding from tree to tree, hunting out small vertebrates — such as birds, fish and lizards — to eat.
Although the holotype specimen of Microraptor zhaoianus was first described in 2000, many years later McGill University’s Professor Hans Larsson and colleagues spotted what others had missed — the fossilized foot of an ancient mammal preserved between the dinosaur’s ribs.
The mammal foot was almost complete and belonged to a very small animal, about the size of a modern mouse.
“At first, I couldn’t believe it. There was a tiny rodent-like mammal foot about a centimeter long perfectly preserved inside a Microraptor zhaoianus skeleton,” Professor Larsson said.
“These finds are the only solid evidence we have about the food consumption of these long extinct animals — and they are exceptionally rare.”
Holotype specimen of Microraptor zhaoianus with mammal foot gut contents: (A) entire specimen; box inset indicates the location of (B) and (C); (B) close-up view of mammal foot; (C) illustration of visible bones: dark gray elements are Microraptor ribs, yellow bones are the articulated mammalian foot and light gray are unidentified bones. Note the juxtaposition of the foot over the inside of the left ribs and the overlap of the right ribs over the foot, particularly over digits II and III. Scale bar – 100 mm in (A) and 5 mm in (B) and (C). Image credit: Hone et al., doi: 10.1080/02724634.2022.2144337.
The analysis of the mammal bones suggests that it was one that predominantly lived on the ground and was not a good climber, making it an interesting option for Microraptor zhaoianus that likely spent most of its time in the trees.
With this new evidence for eating mammals, it is clear that this dinosaur had a diverse diet and was not a specialist on any given option.
It is not certain if the dinosaurs in question had directly preyed upon and eaten these animals or found them already dead and had scavenged them — or a mixture of both — but the mammal at least falls into the range of typical prey size predicated for a predator the size of Microraptor zhaoianus.
“We already know of Microraptor specimens preserved with parts of fish, a bird, and a lizard in their bellies,” Professor Larsson said.
“This new find adds a small mammal to their diet, suggesting these dinosaurs were opportunistic and not picky eaters.”
“Knowing they were not specialized to any particular food is a big deal. This could be the first evidence of a generalist carnivore in dinosaur ecosystems. Generalist predators are important stabilizers in today’s ecosystems, like foxes and crows, because they can feed among several species that may have differing population abundances.”
“Knowing that Microraptor zhaoianus was a generalist carnivore puts a new perspective on how ancient ecosystems may have worked and a possible insight into the success of these small, feathered dinosaurs.”
“It’s so rare to find examples of food inside dinosaurs so every example is really important as it gives direct evidence of what they were eating,” said Queen Mary University of London paleontologist David Hone.
“While this mammal would absolutely not have been a human ancestor, we can look back at some of our ancient relatives being a meal for hungry dinosaurs.”
“This study paints a picture of a fascinating moment in time — the first record of a dinosaur eating a mammal — even if it isn’t quite as frightening as anything in Jurassic Park.”
“The great thing is that, like your housecat which was about the same size, Microraptor zhaoianus would have been an easy animal to live with but a terror if it got out as it would hunt everything from the birds at your feeder to the mice in your hedge or the fish in your pond,” said Mount Marty College paleontologist Alex Dececchi.
A paper on the findings was published in the Journal of Vertebrate Paleontology.
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David W.E. Hone et al. Generalist diet of Microraptor zhaoianus included mammals. Journal of Vertebrate Paleontology, published online December 20, 2022; doi: 10.1080/02724634.2022.2144337
Source link: https://www.sci.news/paleontology/microraptor-zhaoianus-diet-11499.html
