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.

All the World's Antelopes: Gemsbok and Oryx

Gemsbok

As I have discussed previously, there is no such thing as an antelope, in the strict scientific sense. That is to say, they do not form a natural group of organisms, being defined only as those members of the cattle family that aren't sheep, goats, or obviously cow-like. This covers a wide range of animals, some closely related, but others much less so.

I've previously looked at the various species of gazelle, and at the spiral-horned antelopes (which are actually "bovines"). Now it's time to look at the others.

Linnaeus' original catalogue of scientific names, published in 1758, included five species that we would now call antelopes. In that catalogue, they are listed as goats, based primarily on the shape of their horns, and therefore sit alongside the chamois and ibex. Two of these, the dorcas gazelle and the blackbuck, are now placed within the gazelle subfamily, while two others are relatively small "dwarf antelopes", which I will cover later.

Goo Goo G'joob

"Pinnipeds" is the technical term for flipper-footed aquatic mammals that are able (although often with difficulty) to move about on land. Although there had previously been some speculation on the point, we now know that they are a natural group of animals, all descending from a single distant ancestor. They are carnivorans, more closely related to dogs than to cats and probably represent the third major branching within the living dog-like carnivores, after the dogs and bears, but before (for example) the raccoons, skunks, and weasels.

The living species of pinniped are placed within three families, although one or two extinct ones are also recognised. Most pinnipeds belong to the Phocidae, or "seal family". While the term "seal" is often used in modern English to refer to pinnipeds in general, the seal family proper consists of animals especially well-adapted to living in the water. They lack visible ears, and their hind limbs are arranged so to be efficient for propulsion underwater, but almost useless on land, forcing them to haul themselves about using their front flippers only.

Euplerids: Madagascar's Top Mammalian Carnivore

The native mammalian carnivores of Madagascar are mostly obscure to those of us in the West. The one possible exception, thanks to the Madagascar animated film franchise, is the fossa (Cryptoprocta ferox). Often spelt with a single 's', especially in more modern sources, and typically pronounced "foosa", this is the largest and most potentially dangerous of all the island's native mammalian predators.

Having said which, it's not especially big compared with predators elsewhere. There is little need to be a large carnivore when the island does not have, for example, any native antelopes. On average, they are about 75 cm (30 inches) in body length, not counting a cat-like tail that adds about the same length again. Adult females weigh around 6 kg (13 lbs), while the largest males can reach 8.5 kg (19 lbs), about the same as a West Highland terrier. 

Exactly where they fit within the mammalian family tree was long a source of confusion, given a mix of features resembling a range of other animals. When English zoologist Edward Turner Bennett first described the animal in 1833, he considered it to be a type of unusually large civet. So it remained for a hundred until it was moved to the cats in the 1930s, back to the civets in the 1940s, and then to the mongooses in the 1990s. Over the next ten years or so, arguments continued back and forth between all three of these options until genetic studies finally settled the matter in 2003. 

The First Cows In Europe?

When we look at scientific lists of animals, we usually see them placed into neat groups based on their relationships: families, subfamilies, and so on. These are, however, entirely human constructions, and nature is rarely so tidy in reality. Even for mammals, which have been more thoroughly studied than, say, fish or invertebrates, disagreements can arise, and details can change.

At least in the case of mammal groups above the species level, the relationships are faily well understood by this point, thanks to the advance in molecular and genetic studies over the last couple of decades. Disputes are more likely to arise when we question how broadly we should define a particular group, and what taxonomic level it might have. (The latter, of course, are entirely artificial; the cat family is provably a 'real' thing, but the fact that we call it a 'family' rather than giving it some other rank is essentially arbitrary).

This becomes a much bigger issue when we look at animals we know only from fossils. For one thing, we will have fewer, and generally less complete, specimens to examine. Furthermore, unless they are really recent, genetic analysis is out of the question. But, on top of all of that, when we travel back in time, lines become inherently blurred. There's always going to be the question of where exactly the 'not yet X' becomes 'X', even if we had perfect information about them. Which we don't.

Two Million Years of Llamas

The camel family is one of the smaller mammal families in the present day, containing just seven species, four of which are domesticated. Thus, if you don't consider, say, dogs to be distinct from wolves at the species level, one could reasonably argue that there are only four. Although these are all considered to belong to the same subfamily (with all the other subfamilies being extinct), they still fall into two branches: the 'true' camels in the Old World, and their counterparts in the Americas.

It should come as no surprise that members of the family are noted for their ability to survive in arid environments with minimal water. They are, for example, more efficient at absorbing water from their stomach than ruminants such as cattle and deer, and genetically resistant to heat stress and ultraviolet radiation. Nonetheless, while the word "camel" doubtless conjures up an image of one or more of the three Old World species (that is, the dromedary and the wild and domesticated versions of the Bactrian camel), the family also includes those four American species.

The Genomics of Yellow Bats

In terms of species, bats are the second-largest order of mammals, after the rodents. New species are identified all the time, due in part to the relative difficulty of closely examining night-flying mammals, many of which sleep in hard-to-access caves. The current total stands at over a thousand, representing over 20% of all known mammal species. 

Within this huge group, there is, perhaps, rather more diversity than many people realise. While bats have probably not received the same level of attention as some other mammal groups, scientists have nonetheless long attempted to disentangle the relationships between all these subgroups. (Also, when I say they have received less attention, there's a mammal-centric bias here; it's probably still a lot better than, say lizards, let alone millipedes or the like).