Past Time

A few weeks ago Past Time co-host Matt Borths published a study that identified a new species of now-extinct carnivorous mammal from Egypt. The animal was near the top of the African food chain when Africa was cut off from the other continents. It lived in the same swampy ecosystem that was home to our earliest monkey-like relatives!

Here’s a link to the original paper in the open access journal PLOS ONE <http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0173527> if you want to take a look at the original fossils. You can even see them in 3D at www.morphosource.org

Masrasector means “The Egyptian slicer” because the meat-eater was found in the deserts of Egypt, near the Fayum Oasis southwest of Cairo. The species name, nananubis, means “tiny Anubis,” because the small, fox-sized carnivore resembles the jackal-headed Ancient Egyptian god of embalming and guide through the afterlife. “Tiny Anubis” likely scrambled on the ground, chasing large rodents and small hyraxes through the Fayum wetland. It probably didn’t spend a lot of time weighing the hearts of the dead, but such behaviors don’t fossilize very well.

Masrasector nananubis was part of an extinct group of carnivorous mammals called hyaenodonts. If you think of a meat-eating mammal today, like a wolf, tiger, or hyena, you’re thinking of a species from the mammalian order Carnivora. Carnivorans are united by having one pair of specialized meat-slicing teeth on each side of their face. Next time you see a dog or cat yawn, look in the back of their mouth for the scissor-like blades. Hyaenodonts had three pairs of these meat-slicers on each side of their mouths instead of just one, making it easy to recognize them in the fossil record. Hyaenodonts were the only meat-eating mammals in Africa for over forty million years between the extinction of the dinosaurs and the arrival of the first African carnivorans.

Carnivorous mammals are rare in modern ecosystems, and this was also true in the past. Fossilization itself is a rare event, which means the chances of a rare carnivore becoming a rare fossil are very low. This means African hyaenodonts are a rare find, and most are only known from a few isolated teeth and jaws. But, Masrasector is known from several nearly complete skulls, dozens of jaws, and pieces of arm bone.

A photograph and three-dimensional model of the skull of Masrasector nananubis.

With all this material it’s possible to really dig into what Masrasector ate, and how it moved through its environment. African carnivores like lions and hyenas are fascinating, endangered creatures. Hyaenodonts were a separate experiment in how to be a carnivorous African mammal, and they did it successfully for millions of years.Masrasector offers a detailed view of how African hyaenodonts pursued their prey and what their diet was like.

The specimens were discovered in a quarry called Locality-41, one of the most fossil-rich places from the beginning of the Age of Mammals in Africa. The first specimens of Masrasector were found at L-41 nearly 30 years ago. For decades, the specimens accumulated as Egyptian and American paleontologists delicately removed the fossils from the salty, clay-like rock they were embedded in. Hundreds of people moved the sediment, prepared the specimens, and protect these delicate fossils, which need to be kept in a humidity-controlled room because the salt and clay they were fossilized in can expand and break the bones. Salt was an important ingredient in the mummification process, which is another reason naming Masrasector nananubis after the god of embalming made sense.

 

Matt and Erik investigate new fossils during fieldwork in the Fayum Depression of Egypt.

“The Fayum deposits give us our most detailed insights into the early evolution of Africa’s native mammals, when that continent was still largely isolated from other landmasses,” says Eric Seiffert, co-author on the study and Professor in Integrative Anatomical Sciences at the University of Southern California. “The small carnivorous mammals from the Fayum sites were previously only known from a few jaw fragments and isolated teeth, so the discovery of complete crania and arm bones of Masrasector provides lots of new information that allows us to better understand what these animals looked like, what their adaptations were, and how they might have fit into these ancient ecosystems.

Because the specimens are so delicate, many were micro-CT scanned at Duke University to create digital models of the specimens. Now the digital models can be shared widely and studied by researchers around the world, without needing to handle the delicate specimens.

With all the anatomical detail provided by the specimens, it was possible to run an analysis using new analytical methods to understand where Masrasector fits in the hyaenodont family tree. The results reveal Masrasector is part of a group of hyaenodonts that were part of African ecosystems for millions of years: Teratodontinae. The oldest species in Teratodontinae is nearly 50 million years old and the youngest shared the landscape with the early relatives of dogs, cats, and mongooses that crossed into Africa when the Arabian Peninsula connected Africa to Eurasia.

Teratodontines, were an integral part of African landscape, shaping the same ecosystems where we find our ape and monkey relatives. Then hyaenodonts passed the ecological baton to modern carnivores. All of this Masrasector material helps to sort out their anatomy and relationships, so researchers can piece together what ecological role modern African carnivores inherited from these ancient beasts.

To reconstruct the ecology of Masrasector, the researchers took measurements of the arm bones of Masrasector, other hyaenodonts, and modern carnivorans. Because the locomotion of modern carnivorans is known from actually watching them move, the researchers used a classification analysis to predict Masrasector was a ground-based carnivore, like a modern fox or hyena.

An illustration of Hyaenodon, a large North American relative of Masrasector by paleoartist Nobu Tamura. This illustration captures the large rectangular skull of hyaenodonts.

The discovery of Masrasector nananubis allowed Matt and Dr. Seiffert to delve into the ancient lives of a mysterious group of African carnivorous mammals. With the scans of the specimens and the measurements accessible online, “tiny Anubis” can continue to guide researchers through the evolution and extinction of Africa’s first meat-eating mammals.

This study was funded by grants from the National Science Foundation Division of Biological Infrastructure, Division of Behavioral and Cognitive Sciences, and Division of Environmental Biology, The Leakey Foundation, The Explorers Club, Gordon and Ann Getty, and the Society for Integrative and Comparative Biology.

 

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