Prehistoric Mammal Discoveries of 2020

The largest known Oligocene whale was
moved into the new genus Ankylorhiza
this year

Well, that year was... different. Fortunately, it didn't stop me posting and, indeed, a cancelled summer break meant that you got one more post than anticipated you lucky people, you. But as 2020 finally passes into the history books where it can bloody well stay, it's time for the end-of-year roundup of paleontological discoveries that didn't make the regular blog. As always, no theme, just a random assortment of journal papers that may, for all I know, be thoroughly contradicted by this time next year. But this is a collection of things that some scientist, somewhere, thinks that they demonstrated in 2020:

Miocene (Pt 22): Last of the Creodonts

The largest predator in Africa today

The dominant mammalian carnivores in Africa today are the lions, hyenas, and leopards, with cheetahs and wild dogs also playing their role. The ancestors of all of these creatures first reached the continent from the north, shortly after it collided with Eurasia during the Early Miocene. For the most part, at the time, their ancestors were small, with hyenas, for example, being no larger than mongooses. But this does not mean that Early  Miocene Africa had no large predators at all.

For one thing, the cats, hyenas, and so forth, were not the only carnivorous mammals to have made the crossing from Asia. The animals known as bear-dogs, or more technically, amphicyonids, are far better known from Europe, Asia, and North America, but they did reach Africa, too. 

Miocene (Pt 14): Sabre-toothed Sea Otters

Ysengrinia

When bears first entered North America is really more a matter of definition than of our understanding of the fossil evidence. Going by what is probably the most common current definition, bears first appeared in Europe about 20 million years ago, in the form of Ursavus elmensis. Noticeably smaller than modern bears, this developed into a number of species across Europe and Asia, and to the closely related Ballusia in China.

Almost immediately, however, Ursavus also crossed into North America, probably arriving around 19 million years ago. It seems to have been far less common there than it was in Europe, with the local species, Ursavus pawniensis (there were probably others, but that's the only one we know of for sure) living in relatively small populations across the west, from Nebraska to Oregon and Saskatchewan. It doesn't appear to have left any descendants, being eventually replaced by more modern species of bear from Asia rather than evolving into anything uniquely American.

Miocene (Pt 8): Giant Honey Badgers and European Pandas

Indarctos

A great many predators lived in Europe in the glorious warmth of the Mid Miocene, when the continent was lush with subtropical vegetation and the herbivores that fed on it. As the climate began to turn, and the forests gave way to more open terrain, both the herbivores and the animals that preyed on them underwent a number of changes, with the latter in particular suffering some loss of diversity. (At least, so far as we can tell from the incomplete fossil record).

This affected the full gamut of mammalian carnivores, including many of the smaller, less obvious, ones. The boundary between the Middle and Late Miocene is an arbitrary one that isn't really marked by anything much in Europe, so that, to begin with, these were as numerous as ever. There were badgers, such as Sabadellictis, and even skunks, which today are not found outside the Americas.

Miocene (Pt 4): Bear-Dogs and Dog-Bears

Amphicyon

Many of the animals we would see in Early Miocene Europe, were we able to visit, would be of broadly recognisable types: deer, pigs, antelopes, rhinos, and elephant-like mastodons. True, many of these are nor animals we would expect to find in Europe today, and the individual species were, of course, different from the modern sort, and in some cases quite dramatically so. But they at least have identifiable relatives today.

But all of the animals I've just mentioned are herbivores. Yet, when it comes to the larger predators of the day, we instead find that most of them were rather different, lacking close modern relatives. While more recognisable carnivores did, in fact, turn up as the Miocene progressed, at least in the beginning, the majority were survivors from an even earlier time, before many modern kinds of animal had arisen.

The Beardogs that Travelled the World

Amphicyon

Dogs and bears are two quite distinct families of carnivoran mammal, and nobody today is likely to mistake one for the other. They both belong to the same half of the carnivoran family tree, separate from the one that gave rise to such creatures as cats and mongooses. However, their half of the tree also included such animals as weasels, seals, and raccoons, so it is quite diverse. Furthermore, within that branch, bears and dogs are not particularly closely related, last having shared a common ancestor something like 50 million years ago.

However, before we get back that far in evolutionary history we discover that, for much of the Age of Mammals, there was an additional family of animals belonging to the broad group that includes both bears and dogs, and which is no longer with us. These were the beardogs, more technically known as amphicyonids.

Beardogs were not, despite the name, the ancestors of bears and dogs. They were a separate family, one containing animals that looked a bit like bears and a bit like dogs, and which needed a common name of their own. "Beardogs" gets across both those physical features and the fact that they are, indeed, related to the two living families... having said which, it is not at all clear which, if either, of the two they are closer to, in part because the first of them appeared so early.