Gorgosaurus has become the first tyrannosaur found with remnants of its last meals still inside its body and joins the very small club of “stuffed” dinosaurs discovered so far.
In particular, where once there must have been the digestive system of TMP 2009, there are the legs and portions of a tail and an arm of two specimens of Citipes, an oviraptorsaurus, eaten within a short time from each other not long before the death of Gorgosaurus himself.
In fact, the bones of the oviraptorsaur consumed first were partially eroded by the gastric juices of the predator, while those of the second show no signs of degradation by acids.
All three dinosaurs in this case were juveniles. The Gorgosaurus was estimated to be seven years old and weighed around 300 kg. The Citipes were extremely young, less than a year old as their bones have no growth rings.
Furthermore, the fact that only the most palatable portions of the prey are present, those which include the viscera and the most voluminous muscles, suggests that, at least this Gorgosaurus, dismembered them, discarding the less nutritious parts. A way of processing food that is more like a bird than a crocodile or monitor lizard. This could depend on the diameter of the digestive canal of the living animal not being wide enough to allow the passage of whole prey. Among other things, the long bones of the two prey are aligned in very specific directions which should suggest the layout of the digestive canal in that particular part of the body.
From these data it was deduced that young tyrannosaurs most likely did not eat like adults and procured their prey independently. There must therefore have been a segregation of prey so that both the niches of medium-sized predators and those at the top of the food chain were occupied by the same tyrannosaur species at different ages of their lives.
It would not make sense for an adult Gorgosaurus to hunt such tiny prey both because it was probably too agile and because the energy gain would be so paltry that in all likelihood it would not even compensate for the energy spent during the hunt. This is also evidence against the possibility that tyrannosaurs hunted in small family groups, which is often proposed in documentaries. In this case, juveniles and adults would feed on the same prey, large animals killed by the combined efforts of the pack, as happens for example with lions or wolves.
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For the photos were used:
Gorgosaurus by PNSO
Gorgosaurus by Vivid Toy Group Ltd,
Caudipteryx by Safari LTD (Feathered Dinosaurs Toob),
Corythosaurus by Safari LTD (Carnegie)
Parasaurolophus and Styracosaurus by Battat
Courtesy of Pietro “Leyster.
Link to the study Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator : https://www.science.org/doi/10.1126/sciadv.adi0505