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Author Interview: Matt Borths on the newly named fossil mammal Masrasector nananubis (and the possibility that he accidentally unleashed an ancient evil upon paleontology)

Ancient mammals were weird. And it wasn’t the “super-size and add saber teeth” kind of weird, either. Mammalian evolutionary history is full of fascinating dead ends and interesting side branches–exemplified quite well by hyaenodonts. Don’t let the name fool you, though–they have little to do with modern day hyaenas! As a group, hyaenodonts only are cousins to today’s modern carnivores, forming a side branch that diverged before the origin of today’s cats, dogs, hyenas, and honey badgers. So, any physical resemblance is largely coincidental. Hyaenodonts roamed North America, Europe, Asia, and Africa from around 60 to 10 million years ago, and were pretty darned successful in terms of geographic distribution, evolutionary longevity, species count, and variety of body forms. Even if they are long-gone today, hyaenodonts were pretty important players in the ecosystems of their time and present an interesting case-study in evolutionary radiations.

Life restoration of Hyaenodon horridus and Leptomeryx evansi from White River, in W.B. Scott's "A History of Land Mammals in the Western Hemisphere." New York: The Macmillan Company.
Life restoration of Hyaenodon, one of the best-known hyaenodonts in the fossil record. Image by Robert Bruce Horsfall, from Scott 1912, in the public domain.

Compared with their cousins from elsewhere in the world, African hyaenodonts are fairly poorly known. Most species are represented primarily by teeth, which can be informative for identification and diet inference, but are pretty limiting when it comes to understanding overall evolutionary relationships, behavior, and function. How closely related were African hyaenodonts to hyaenodonts elsewhere? What did they look like and what kind of lifestyle did they live? What role did they play in ancient African ecoystems? Some newly described fossils from Egypt help answer some of these questions, and raise a whole different set of questions for future scientists to investigate.

The new hyaenodont, given the name of  Masrasector nananubis, is detailed in a paper appearing today in PLOS ONE. I contacted one of the authors of the study, Matt Borths, and got his thoughts on the project.

Skull of <i>Masrasector nananubis</i>, courtesy of Matt Borths.
Skull of Masrasector nananubis, courtesy of Matt Borths.

Q: What was the most surprising part of your study, and why?

A: The most surprising part of this study was that Masrasector and its kin are part of a massive radiation of hyaenodonts that originated in Africa. For a long time it was unclear if Africa was a kind of cul-de-sac, catching various hyaenodont lineages that originated in Europe or Asia or North America, or if Africa was the source of this diversity and had its own endemic lineages.

Through this study, we discovered anatomical features that link the African group that includes Masrasector nananubis, called Teratodontinae (which means “monstrous teeth”), to the group called Hyainailourinae. Teratodontines are almost entirely African and the group includes many of the more omnivorous hyaenodonts. Hyainailourines, on the other hand, are specialized hypercarnivores, occupying ecological niches similar to modern big cats and hyenas. Hyainailourinae includes many African species, but the ultimate origins of the group were a little murky because they are also found in Europe, Asia, and North America.

A couple of cranial and skeletal features helped pull Masrasector‘s Teratodontinae into a close relationship with hypercarnivorous Hyainailourinae, evidence that both lineages belong to a large group of hyaenodonts with roots on the African continent. This all reorients major swaths of hyaenodont evolution towards Africa and shows that in Africa, hyaenodonts were filling in many of the niches occupied by large and small carnivores on the continent today.

With only the teeth of these animals, this relationship would have been hard to put together, but with more of the skull and skeleton of Masrasector, we could make comparisons to other hyaenodont cranial material from animals with different feeding habits, making connections despite dental and ecological differences and revealing this massive African lineage that originated near the extinction of the non-avian dinosaurs.

A very simplified family tree of hyaenodonts and other carnivorous mammals. Hyena by Oscar Sanisidro (public domain), cat by Steven Traver, seal by Tracy Heath, coyote by David Orr, Hyaenodon by Robert Bruce Horsfall — all in public domain, via PhyloPic.org. Masrasector skull from Borths.

Q: What kind of environment did Masrasector live in? What other things would have been running around with it?

A: Masrasector nananubis was found at a spot called Locality 41 (L-41) in the Fayum Depression in Egypt. Today the Fayum is part of the expansive western desert of Egypt, but L-41 is made of stacks of salty mudstone that reveal the spot was a marshy mangrove forest 34 million years ago, a little like the modern Everglades in Florida. One of the things that makes the Fayum so important is at the time, Africa was an island continent, cut off from the other continents like Australia is today. Also like Australia, there were lineages evolving in Africa, like elephants and hyraxes, that filled niches occupied today by other animals that moved into Africa after the continent got close to Eurasia. On the ground were hippo-like elephant relatives called Moeritherium, pig-like hippo relatives called anthracotheres, and horse-like hyrax relatives (today hyraxes are pretty much just grumpy rabbit-sized animals). Really everyone was trying to be be something else in Eocene Africa. In the trees were the primate relatives of lemurs, South American monkeys, and the common ancestors of Old World monkeys and apes. They had already found their niche, and were munching leaves and fruit like their modern descendants.

Q: Was there anything in your research for this paper that presented a particular challenge or annoyance? What was it?

A: One challenge is we now have so much material from Masrasector nananubis, but the evidence from many other hyaenodonts, including other species of Masrasector, is still really fragmentary. We would love to make comparisons between the ear regions or brain cases of other African hyaenodonts, but we can’t. The record of Masrasector nananubis is so good now that we can make notes of anatomy we would like to check on other hyaenodonts when it’s found, but for the time being we are simply left wondering when the fan-like structure on the back of M. nananubis‘s skull first appeared, or what the locomotion of other hyaenodonts at L-41 [the site where Masrasector nananubis was discovered] was like. The patchy African record for the group is frustrating, especially the very fragmentary early record of the group. It feel stupid to complain about having so many skulls and jaws, but they really do present more mysteries than they solve, which is why we need to keep collecting and studying hyaenodonts, the first African carnivores.

Q: You clearly collected a good chunk of scan data with this project. By making the digital files available, what do you hope other researchers might do with it?

A: Hyaenodonts have been a little neglected as a group. They were the apex carnivores in many ecosystems for the first two-thirds of the Age of Mammals. Yet, there are only a few researchers delving into their evolution and ecology. I hope by making this material as accessible as a few clicks of the mouse at Morphosource.org, researchers around the world who focus on mammal evolution can examine the material and bring their own questions and areas of expertise to a group that is pretty obscure at the moment. Researchers with more of a focus on brain evolution or limb evolution than I have may notice something new.

By making fossils accessible outside of the museum setting, I hope more investigators can be involved in future studies. There are measurements we didn’t collect because they weren’t pertinent to our questions, but someone else can now access this material to collect the measurements they need to answer their own questions. Part of what makes paleontology so exciting is we don’t know what questions and technologies will be brought to bear on the fossil record. By making these fossils available digitally, they can be printed, measured, scrutinized, and broken down using those now-uninvented methods.

I also hope that people who want to learn about hyaenodonts examine these digital files to acquaint themselves with the predators our primate ancestors once had to contend with and maybe print them off to look these creatures in the teeth. There isn’t really a place to see these fossils on display at the moment. These fossils are part of our story, and making these files available enables everyone, from those with specific research questions to the casually curious, able to study this material.

Finally, the fossils from L-41 are actually pretty delicate. The rocks they are preserved in are filled with salt crystals and mud that expands and contracts with changes in temperature and humidity. The collections at Duke University and the Cairo Geological Museum are carefully monitored and stabilized, but these fossils may not always be as well-preserved as they are now. The digital models are a record of the morphology we examined. Future researchers can build their investigations upon these models as a record of this delicate material.

anubis
Anubis (right), weighing the heart of a recently deceased candidate for the afterlife. Scientists today employ a similar process during peer review. Public domain image, via Wikimedia Commons.

Q: At least in the movies, invocation of the names of ancient gods never ends well for the protagonists. Your new animal was named after Anubis–did you have any worries that by doing so you would unleash some unspeakable ancient evil on the field of paleontology?

A: There was a key moment when I choose to follow my passion for fossils and had to resign myself to being an amateur enthusiast of ancient cultures and civilizations. I’ve always been especially fascinated by Ancient Egyptian myth and artifacts. By evoking Anubis as part of this study, I felt I could finally bring two of my passions to the same question.

It occurs to me now, as a new adaptation of The Mummy is about to be unleashed, that I should have contemplated this a little more carefully.

Jackal-headed Anubis is the ancient Egyptian god most closely associated with mummification, the process of preparing the remains of the deceased for eternal preservation. That process is evocative of fossilization, so I’ve always seen Anubis as a patron god of paleontology. Further, salt was a particularly important part of the embalming process that lead to the preservation of mummies, and the rocks where Masrasector nananubis was found are chock full of the stuff, so I thought the name “tiny Anubis” was the perfect fit for the little, jackal-like creature.

As I contemplate this more, I’m reminded Anubis is also the protector of cemeteries and tombs, which is why it occurs to me there may be reason for me and other paleontologists to worry… Until I am struck down by a curse from the Book of the Dead, I will just have to practice this overthought explanation for the name and hope for the best when Anubis weighs my heart in the afterlife.

Thank you, Matt, for taking the time to tell us a little more about your research. If you haven’t already, check out the paper at PLOS ONE. And, check out more of Matt’s work in Past Time, a podcast that he co-hosts!

Citation
Borths MR, Seiffert ER (2017) Craniodental and humeral morphology of a new species of Masrasector (Teratodontinae, Hyaenodonta, Placentalia) from the late Eocene of Egypt and locomotor diversity in hyaenodonts. PLoS ONE 12(4): e0173527. doi:10.1371/journal.pone.0173527 [link]

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