Hippos in the Tiber

The hippopotamus (Hippopotamus amphibius) is an iconic African animal. While their distribution is very patchy, in part due to their reliance on large waterways, they are found across essentially the whole of Africa south of the Sahara and north of the Kalahari and the South African veldt. A second, endangered, species belonging to the same family, the pygmy hippo (Choeropsis liberiensis), lives only on the southern coast of West Africa, between Sierra Leone and Côte d'Ivoire. 

But hippos were once common in Europe and southern Asia. In the case of Europe, for example, we have fossils from Portugal to Greece, and as far north as the UK. Nevertheless, hippos have never been especially diverse, at least in comparison to groups such as deer or pigs, and they are grouped into no more than around six widely accepted genera. This includes the two that are still with us, and we don't have a large amount of information on three of the others.

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.

A Brief History of Zokors

The rodents are the largest group of mammals, in terms of number of species, and they are divided into several families. Some of these are familiar, such as the mice, voles, squirrels, and gophers, but others are much less so, at least to the majority of people in the West. This includes, for example, the zokors.

There are a couple of reasons why zokors are not as well-known as some other rodent groups. For one thing, they only live in northeast Asia, an area that it's fair to say doesn't receive much attention in the Western world. For another, even if you did live there, you wouldn't see them very often, because they are burrowing animals that don't like coming to the surface if they can help it. Rather like moles, you might see the mounds of earth they leave, but not often the animal itself.

Strange Carnivores of Madagascar

Madagascar is the fourth-largest island in the world, almost three times the size of Great Britain, or half again the size of California. We should not be surprised, therefore, that it has a considerable amount of native wildlife. However, it's also noteworthy that it has been an island for a very long time - certainly for far longer than Britain has been.

In fact, Madagascar became an island around 91 million years ago, over 20 million years before even the likes of Tyrannosaurus appeared on the scene. Moreover, this was when it split away from what was then the island of India, with its break from Africa being almost twice as far back in time. But, even if we take that younger date for the beginning of its isolation from any sort of 'mainland', it's well before any of the sort of mammals we would recognise today had evolved. There's no equivalent here of mammoths nipping across the English Channel.

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.

The Thrush-beaked Consort Bird

A modern thrush

This post will be the latest as of 1st April, so it's that time again...

About 40% of all living mammal species are rodents. Over a third of those that aren't are bats, leaving just 38% belonging to any other group - primates, cloven-hoofed mammals and all the rest. These are, at least in terms of speciation, clearly very successful body plans.

But the bias is even stronger with birds. A whopping 60% of living bird species belong to just one order: the Passeriformes. The chances are that, if you think of a "typical bird" the image that pops into your head is of a passerine. There are about 140 different families of passerine (the exact number being a matter of taste among ornithologists), of which 123 constitute the songbirds.

The Patagonian Homunculus

In 1891, Argentinian naturalist Florentino Ameghino, the founding father of South American palaeontology, described a new species of fossil primate. Naming it Homunculus ("little man"), he recognised that it resembled a lemur almost as much as a monkey and must therefore be very primitive, but he was unable to categorise it further.

To be fair, all he had at the time was a section of the lower jaw. Over the next seven years, working with his brother Carlos, he uncovered a few further specimens. These included part of a skull and some limb bones, but the exact details of what they had discovered remained obscure, beyond the fact that it was a primate of some sort.

It didn't help that, after 1898, the next discovery of a fossil belonging to the genus didn't happen until the 1980s. And that was only a few isolated teeth. Since then, nothing until the current century.

Rabbits in the Ice Ages

The rabbit (Oryctolagus cuniculus) is one of the more familiar mammal species to most people in the developed world, not least because it has been partially domesticated. Moreover, wild and feral rabbits are found across wide parts of the world, living on every continent except Antarctica. They are adaptable animals, able to survive in a wide range of different habitats, from hot semidesert to forests and bleak moorland. So much so, in fact, that, in most parts of the world, they are a pest.

The rabbit is widespread because we humans have spread it, following the initial domestication event in France, no later than 800 AD. This was originally for meat and fur, with pet breeds appearing only from the late 18th century. Rabbits are now found, for example, on Middleton Island, a chilly speck of land 130 km (80 miles) off the south coast of Alaska, and on the Kerguelen archipelago in the Indian Ocean, which is about as remote a place as it's possible to get.

Climate, Cloud Forests, and Cotton Rats

The Cricetidae is the single largest family of mammals in terms of the number of species, at least according to the current count from the American Society of Mammalogists. While the name translates as "hamster family", the great majority of species are not themselves hamsters. In fact, there are five subfamilies of cricetid: the hamsters, the voles, and no fewer than three with members that basically look like mice or rats... even though the true mice and rats belong to the second-largest family, the Muridae.

The largest of these subfamilies is the Sigmodontinae, consisting of mouse and rat-like animals primarily native to South America, although one species lives as far north as Virginia, and several others reach Arizona and New Mexico. The group is named for the S-shaped pattern on the molar teeth and was originally coined as the genus name for the cotton rats in 1825.

How the Lemming Got its Coat

The Ice Ages were, without doubt, the most dramatic natural climatic changes on Earth in the last few million years. The last one was particularly severe, with vast ice sheets covering much of northern Europe and northern North America. This, naturally enough, forced many species of animals in the Northern Hemisphere to move south. Even those well-suited to the cold, such as reindeer, musk oxen, and woolly mammoths, would have had to avoid the barren ice sheets, even if they were happy in the broad tundra belt to the south.

In Europe, in particular, there is only so far south you can go before hitting the coastline. This meant that many animals were forced into small areas, some of which may still have been marginal habitat for them, to avoid extinction. These areas are called "refugia", and their small size and isolation were a driver for evolutionary change. Sometimes populations were split apart for so long that they became separate species and, for example, we can date many species of northern birds to this time, even though, for them, the Mediterranean would not have been an issue. 

Bast, Sekhmet, and the Egyptian Hyena-cats

Megistotherium, a Miocene hyena-cat

The majority of the land-based mammalian predators we are familiar with today belong to the order Carnivora. This is a diverse order, including such mammal families as the cats, bears, dogs, weasels, and seals. In fact, if we ignore the cetaceans and a few kinds of marsupial, they are the only large carnivorous mammals alive. But, as so often, this was not always the case, and they once shared the world with at least three other orders of predatory placental mammal (plus some marsupials far more fearsome than any Tasmanian devil). 

Two of these orders died out relatively early on, but one of them survived for much longer, producing multiple diverse species that lived across Eurasia, North America, and Africa. These were the hyaenodonts, named for Hyaenodon itself, first identified from a fossil all the way back in 1838. With so many species, they must have been successful in their day, but their numbers declined until the last two species died out in Africa and India around 9 million years ago, perhaps due to competition from the carnivorans, perhaps due to long-term climate change. Or, more likely, both.

The Earliest Landfowl

Gallinuloides

This post will be the latest as of 1st April, so if you've been following this blog for a while, you'll know what that means... 

The humble chicken (Gallus domesticus) is a member of the pheasant family. This is a moderately-sized family, with around 180 species. Alongside the chicken and its wild ancestor, this also includes, not just pheasants, but many similar ground-dwelling birds, such as grouse, partridges, true quails, turkeys, and peacocks. 

It is, in turn, a part of a larger taxonomic group technically referred to as the Galliformes, or more commonly the "landfowl". The other four living families in this order have fewer species and are generally less well-known, but they share the same features of being generally plump, often quite large by avian standards, and having short, rounded wings unsuited for long-distance flight. 

When Snow Leopards Reached Portugal

While the various species of "roaring cat" all share a great many points of similarity, most are easily distinguished from each other. Arguably, one of the most distinctive is the snow leopard (Panthera uncia). Not only does this have unusually thick fur for a wild cat, but it also has a longer tail than we would expect, and the face is shorter and wider than that of other roaring cats.

The snow leopard was first scientifically described by Johann Schreber in 1775 as a member of the genus Felis. The differences from other cats were sufficient that, in 1854, John Edward Gray proposed that it be given its own genus, Uncia. His original definition of the genus did not stand (it also included at least one species of "purring cat"), but it was resurrected again in the early 20th century, and used solely for snow leopards up until 2006. In that year genetic evidence placed it alongside the other "roaring cats" in Panthera, something that has been amply confirmed since.

From Dragon to Cave Bear

In 1675, German physician Johann Paterson Hain published a detailed description of the bones of what he believed to have been a dragon. Such bones had been unearthed from German caves for centuries and identified as belonging to various mythical creatures, with unicorns perhaps the most popular - likely since one could sell supposed unicorn horns for their magical healing properties. Fortunately for us, his illustrations were highly accurate and we can identify them for what they really are.

Indeed, while naturalists continued describing such bones as belonging to fantastical animals into the 18th century, physician and rationalist Gregor Horst had beaten them to the punch, pointing out as early as 1656 that bones recovered from Unicorn Cave (yes, that is its actual name) looked remarkably like those of "bears, lions, and humans". Today, we can look at Paterson Hain's original illustrations and confirm that he had produced the first known published drawings of the bones of a cave bear.

Unravelling the History of Seals

Allodesmus, a desmatophocid

Trying to determine the largest patterns in evolution can be a daunting task. Here, we often want to look at large numbers of species, comparing the living ones and filling in the gaps with fossils that are often incomplete, ambiguous, or that simply haven't been discovered yet. As a result, there are several big transitions in mammalian evolutionary history that we'd like to get a better look at. Bats are a significant case in point; their small fragile skeletons don't preserve well if we want to see more than teeth, and how they developed their forelimbs into wings remains obscure.

With some groups, however, we do have sufficient fossil evidence that we can look at a whole group of animals and get some idea, not just of how it originated, or where it fits in the larger mammalian family tree, but what ups and downs it has faced over the course of its existence. This can tell us what alterations in climate or geography drove changes within the group and how and when particularly evolutionary innovations developed.

Oligocene (Pt 10): The First Elephants with Trunks

Barytherium

During the Oligocene, Africa remained an island continent, separated from Asia by the Tethys Sea that ran from the Atlantic, through what is now the Mediterranean, and then south of the Zagros Mountains to connect with today's Persian Gulf. The Tethys was narrower in the Oligocene than it had been in the preceding epoch, due both to Africa's slow northward movement and the fact that sea levels were lower, but it was still substantial. As a result, the large herbivores of Eurasia, such as pigs and rhinos, had yet to enter Africa, resulting in quite a different fauna there.

The same was not, however, necessarily true of smaller mammals, some of which had been there for some time, more able, perhaps, to be accidentally carried across on floating vegetation. (A rare event, to be sure, but tens of millions of years gives a lot of opportunities to get it right). There may not have been antelopes in Africa yet, but there were certainly rodents.

Oligocene (Pt 9): Rise of the Dogs

Sunkahetanka

Many of the carnivorous mammals present in North America during the Oligocene were of types also found in Eurasia. However, this far back in time, they did not necessarily belong to any family of animals we would recognise. Cats, for example, first appeared in Europe at the end of the epoch and did not reach the Americas until much later. Other groups, such as raccoons, simply didn't exist yet. 

But we do, for example, have Palaeogale, an animal also known from Europe that looked somewhat like a polecat, but was actually more closely related to cats and mongooses without, so far as we can tell, being either. Corumictis looked similar, but analysis of the skull has shown that it much closer to true mustelids. About the size of a modern weasel, it lived in Oregon at least 29 million years ago, towards the middle of the epoch. It may make it the first mustelid to reach North America from Eurasia, home to the very similar, and slightly older, Plesictis. It's far enough back that it might, however, belong to an early musteloid group rather than to the modern family (that is to say, it may be equally related to mustelids and raccoons, and thus, strictly speaking, neither). Oaxacagale is almost as old, and lived in what is now Mexico; it's probably another close relative but, it too, has so many primitive features that it's hard to place precisely.

Before Cats Could Purr

Hyperailurictis

Although the differences are obvious when we can see the spots or stripes on their fur, the various species of cat are often very similar in form, and it can be hard to tell them apart based on the skeleton alone. For this reason, through much of the 20th century, all of the "purring cats" except the cheetah were placed in the single genus Felis. That's not the case today, when we distinguish genera not only for the larger purring cats, such as pumas and lynxes, but others that modern genetic evidence tells us are distinct, such as the group that includes the ocelot.

Given this, it's hardly surprising that the same should go for fossil species, too. It may well be that if we had genetic evidence on those, or could even just see their coat colour, we would be more willing to distinguish them but, when all you have is an often fragmentary skeleton, there isn't much to go on.

Oligocene (Pt 8): The First Tapir and the Last Hoofless Horse

Miohippus

A close look at the evolutionary history of horses reveals that it's more complicated than sometimes presented, with numerous side branches forming a bushy tree of different species, many of which ultimately died out without descendants. This applies both to the origins of the group in its early days and its period of great diversification through the Miocene and Pliocene epochs. In the Oligocene, however, the picture, at least so far as we can tell, was rather simpler.

We know of two genera of horse that made it into the Oligocene from the preceding epoch. Mesohippus had been around for a while, Miohippus was a relative newcomer, appearing towards the very end of the Eocene. The two are rather similar, to the point that it has been argued they should be treated as different species of the same genus (which would be Miohippus, as that was named first) and they are both found in fossil beds across the United States and southern Canada, with Miohippus being known from Washington state to Florida and Mesohippus primarily in the west. The similarity also led to proposals early on that the one directly evolved into the other, but it's now clear that they lived alongside one another for millions of years, which scuppers that idea.