The skeleton of Moschorhinus kitchingi, a prehistoric therapsid. The pictures show the largest known specimen from both the top (dorsal) and bottom (ventral) views.Credit: Brandon P. Stuart
A study of fossil bones from four collections has revealed that a stocky build was an evolutionary advantage for a late Permian predator.
Moschorhinus kitchingi is a therocephalain — a ‘beast head’ — named for its large skull and carnivorous teeth structure.
Moschorhinus is the only large carnivore known to have survived the Permo-Triassic mass extinction. For the first time, a detailed look1 at the skeletal fossils, found in the Karoo Basin, has revealed how this mammal forerunner's stocky build was advantageous.
“The skulls have been the subject of other studies, but by bringing together fossils from four collections, we were able to piece together a much more comprehensive picture of this formidable predator,” says Brandon Stuart, PhD student at the University of the Witwatersrand (Wits), South Africa.
“During the late Permian, approximately 253 million years ago, the Karoo Basin enjoyed a lush, stable environment with seasonal rainfall. Large rivers dominated the landscape. The therapsids – mammal-like reptiles - were the dominant terrestrial animals during this time.
“The gorgonopsians — sabre toothed therapsids — primarily filled the apex predator role, but a few therocephalians, such as Moschorhinus, would have been competing with them for prey,” Stuart explains.
“However, during the Permo-Triassic mass extinction, the environment became unpredictable. Carbon dioxide levels increased, causing global warming, and the climate alternated between massive floods and severe droughts.”
One of the surviving predators was Moschorhinus. The study reveals a uniquely stocky build, characterised by a robust and thick-set skeleton. Its robust scapula (shoulder blade), humerus (upper arm bone), and femur (thigh bone) suggest that it was well-equipped to grapple with and overpower its prey.
A reconstruction of Moschorhinus kitchingi.Credit Brandon P. Stuart.
“Previous studies mostly focused on their skulls, so much about their growth and way of life was still unknown. But now, we’re finally getting a clearer picture of what this remarkable survivor was like,” says co-author. Jennifer Botha from Centre of Excellence for Palaeoscience at Wits.
Julien Benoit, a paleontologist at Wits, says: “It seems that Moschorhinus had a short and robust snout, with a dentition that could have enabled it to survive on scavenging during the end-Permian extinction. This may have given it an edge after the extinction when the only prey left was Lystrosaurus, a pig-sized herbivore with a beak and tusks.”
