Hyena and relatives

[brotherbear]

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The hyena that was overshadowed by a Tyrannosaurus rex

Posted on August 28, 2014

One of the wonderful things about being part of Twilight Beasts is that we are discovering new beasts all the time. Many beasts are familiar, like mammoths and sabretooth cats. Others not so much, like the unbelievably cute Great Jerboa, or the strange pig-like peccaries. (Astonishing as it may sound, even woolly rhinoceros are not that well known to some: I have taken woolly rhinoceros bones out for a big museum event, and having spoken to over 500 people, I counted 10 who knew what a woolly rhino was.)
Reading one of our recent guest posts, I came across a beast I didn’t recognise and when I looked into it, I got a little excited! Elegantly written, the post tells us about the pretty nippy pronghorn antelope which only just snuck through the end of the Pleistocene. One of the things that helped it slip through while many others fell, was their speed. These were fast animals, reaching speeds of up to 80km per hour (around 50 miles per hour). Some suggest that speedy predators may have given this antelope a good reason for evolving to be zippier than most. Possibly. There were a few fast predators around, including the American cheetah, and before the dawn of the Pleistocene, a few sabre-tooth cats. One species of carnivore in particular jumped out at me. A species that I didn’t think would be there.
I first heard of Barnum Brown fairly recently on the great, award winning, educational children’s programme Dino Dan. Barnum Brown was a palaeontologist in the late 1800s and early 1900s. He was famous for his discovery of the first Tyrannosaurus rex remains in 1902, which were found in the Hell Creek Formation, Montana.

A couple of years later Brown collected some fossil mammal remains from a fissure which miners discovered at Val Verde Copper Mine in Arizona in 1901. He labelled the bones and packed them off to the United States National Museum (which would become the Smithsonian Institution). Brown was due to re-examine these fossil, and if the infamous T. rex hadn’t taken the public by storm, he may have had the chance.
It took twenty years before anyone pried open the wooden crate full of fossils. It was the curator, Oliver Perry Hay who peered in unleashing one fossil that would stir up debates for decades to follow. The fossils found in the mine were of Pleistocene animals and some were familiar, like pronghorn antelopes and squirrels. One jaw had the label ‘cat’ with it. Comparing the jaw with other cat species, and other carnivores, Hay concluded that it belonged to an extinct hyena. He named it Chasmaporthetes ossifragus which translates to ‘he who saw the canyon’.
This was a huge discovery. A species of hyena living in America?! Before then hyenas had been found in other parts of the world, but not in America. (It has always been fascinating that the more recent cave hyena never followed mammoths or reindeer into America.) This was an exciting fossil.
The Genus Chasmaporthetes evolved some time towards the end of the Miocene around 7 million years ago. It is unsure if this group evolved in Africa, Europe or Asia. 9 different species belonging to this Genus have been discovered so far, including a relatively new one named in 2013 which lived around 4million years ago on the Tibetan Plateau. It was a very successful group of hyenas. In fact species have been found across Africa, in Europe, China and North America, giving it a very large geographical distribution.

Chasmaporthetes ossifragus was the only species of hyena (so far as we know) to have stepped its paws over the Bering Land Bridge into North America. This ‘bridge’ linked the Eastern tip of Siberia to the Western tip of Alaska when sea levels were lower. And once here, around 5million years ago, this hyena moved south. Fossils have been discovered in Arizona, Texas, Florida, and Mexico. Remains, however, are nowhere near as abundant as the European cave hyena where one site may yield dozens of beautifully preserved specimens. The North American specimens are sparse, and fragmentary.

This American hyena is also known as the American hunting hyena, or the running hyena. Not the most elegant of common names, and also a little misleading: although commonly perceived as scavenging ugly beasts, the living species of hyenas today do hunt, and they also run (and they are beautiful animals too). But there is method in the madness. Although fairly few fossils have been found, fossil bones from other species in this Genus show these hyenas were more closely related to the dog-like hyenas (like the extant, but fairly unknown aardwolf) rather than the bigger, robust species. The bodyform appears to have been long, somewhat slender, similar to that of a cheetah. The teeth were sharp, great for slicing flesh, but not a thick as it’s bone crunching cousins.

A fast, fierce hyena, Chasmaporthetes ossifragus was a top predator on the North American grasslands. Other fossils associated with the American hyena include horses, camels, deer, giant marmots and pronghorns: plenty of prey for an active predator. The North American savannah was full of predators, with other ferocious beasts looming such as the Pliocene scimitar toothed cat (Homotherium) and the dirk toothed cat (Megantereon). There was also the America cheetah, and the hugely robust canid Borophangus diversidens which, ironically, superficially resembled the bigger hyenas from Africa in body shape, and are known as the bone crushing dogs. It was a competitive world for animals at the beginning of the Pleistocene.
Most of the competition vanished as the Pleistocene moved into full swing. There were no bone crushing dogs around, or scimitar tooth cats. The American hyena was doing quite well. Hunting other animals, possibly including pronghorns, it was at the top of the food chain. Current evidence points to its extinction in North America around 780,000 years ago based on the youngest fossil evidence so far found. It appears the erratic climate that was the signature of the ever changing Pleistocene Epoch, was to blame for their extinction: changing climates and temperatures replaced the open grasslands to more covered forests.
Hyenas are a misunderstood species that are portrayed as rather ugly, scavenging beasts. Hyenas are one of my favourite Twilight Beast because they are awesome. They had an enormous diverse range of different species living in the past, ranging all across the northern hemisphere. Not far from where I work, around 35,000 years ago, hyenas were running around, dragging back carcasses to their caves. These amazing animals were living in Britain until pretty recently. What’s even more incredible is that one of their cousins was very happily living in North America.
Written by Jan Freedman (@JanFreedman) Reply