Eocene (Pt 5): Cerberus and the Pangolins

Eurotamandua

Today, when we think of large carnivorous land mammals, we think of such things as dogs, cats, and bears, but, while some of these families do date back to the Eocene, they were not found in Europe at the time. Instead, the dominant group of carnivorous mammals were the hyaenodonts.

While the name translates as "hyena-tooth" due to the description of the first fossils to be found, hyaenodonts were not hyenas, or even closely related to them. They belonged to a group entirely separate from the living carnivorans, and that survived alongside them until as recently as 10 million years ago, near the end of the Miocene. For most of that time, they could be regarded as primitive holdovers, vestiges of their past glory, but in the Eocene they were still at the height of their power.

Having said this, the first hynaenodonts to enter Europe were physically unimpressive, succeeding largely due to the fact that there wasn't much else to compete with. These are traditionally grouped into a subfamily called the "proviverrines", although the details are debated. For one thing, it's not at all clear which family (if any) they are a subfamily of. This is largely due to the higher-level classification having shifted since they were first named, but the membership of the group is also in doubt, since it's not at all clear that all of the traditionally defined species share a unique common ancestor with one another.

Eocene (Pt 4): Ancient Beasts of the European Archipelago

Propalaeotherium

The story of the evolution of the horse is one of the most commonly cited examples of evolutionary trends, often illustrated by a series of increasingly horse-like animals with an ever-reducing number of toes. The animal typically shown at the start of that series is, depending partly on the age of the picture, either Hyracotherium or Eohippus.

Hyracotherium was long regarded as the earliest known member of the horse family. In recent decades, it has become apparent that it wasn't really a horse, in the sense that modern horses don't descend from it or its relatives, and today we call the family it belonged to the palaeotheres. The North American Eohippus, on the other hand, despite long being thought to be identical to Hyracotherium, probably is a horse. The confusion between the two means that it's often difficult to tell which is being referred to in older sources. 

Eocene (Pt 3): Sword Teeth and River Pigs

Anoplotherium

Today, by number of species, the most successful group of large mammalian herbivores are the terrestrial artiodactyls - broadly speaking, the "cloven-footed mammals". Except for Australia, they are a key element of almost any mammalian fauna. Their first great burst of diversity occurred during the Middle Eocene, over 40 million years ago, when many new forms appeared across the Northern Hemisphere, some unique to particular places, others more widespread.

Most, however, were nothing we would recognise today. There were as yet no cattle, antelopes, deer, or pigs, and many of the creatures that did live that far back left, so far as we can tell, no living descendants.

Eocene (Pt 2): In the Jungles of Europe

Heterohyus

During the Eocene epoch, Europe was very different from the way it is today. For one thing, it was still separated from Asia, with the Turgai Strait running between the two, roughly from what would now be the Black Sea to the Arctic Ocean. But, were you to look at a map without any modern day context, you probably wouldn't call it a continent, because it wasn't a single landmass, but a chain of large islands.

The biggest of these lay to the north, encompassing Scandinavia and the lands to the east. Just south of that, the second-largest was the one that would later become Britain, France, Germany, and some of their smaller neighbours. A smaller, but still sizable, Iberian island lay to the southwest, and a collection of low-lying ones occupied the south and east, with the more mountainous parts of that region having yet to form.

But, even if you didn't know the changes in the geography, if you could simply travel back in time to the Early Eocene and look around you, it wouldn't feel much like Europe. The continent was closer to the equator than it was now - northern Germany was about where Milan is today - but, even ignoring that, the world as a whole was much hotter. This is part of the reason for the islands, since there were no ice caps back then, but it means that our hypothetical time traveller would be, in almost any part of the landmass, standing in a jungle.

Age of Mammals: The Eocene (Pt 1)

When Scottish geologist Charles Lyell first created the system of epochs we now use for dividing the Age of Mammals, he designated four of them. This was in 1833, so he did not know the true age of the Earth, let alone the timespans of the epochs he was naming - he was basing them purely on geological strata and the types of fossil seashells found within them. We now know, however, thanks to the wonders of radiometric dating techniques, that the oldest of the four epochs he defined spanned over half of the Age of Mammals, longer than the other three put together.

Two epochs have been carved out at either end since, so the Eocene is not quite as long now as it was when Lyell named it. However, it remains the longest of the seven epochs since the extinction of the non-avian dinosaurs, still occupying a third of that entire stretch. As currently defined, it runs from 56 to 34 million years ago. Compared with the entire age of the Earth, that's not very much, but from the point of view of most mammalian palaeontology, that's unusually long.