The Pandas of Bulgaria

The bear family as it exists today contains relatively few species. All but two of these species are placed in a single subfamily, the ursine bears, which includes the familiar black, brown, and polar varieties along with a couple of species unique to southern Asia. A second subfamily, the short-faced bears, includes the living spectacled bear of South America and several, often exceptionally large, fossil species. They are thought to have split from the ursine bears around 12 million years ago, towards the end of the Middle Miocene. The third living subfamily is both much older and more distinctive.

This, of course, is the subfamily of the pandas, the Ailuropodinae. Pandas are sufficiently odd that it was unclear for a time whether they were really bears, or something else, although their status hasn't really been in doubt since the 1980s when genetic evidence proved what had, even then, been suspected for a couple of decades. Today, only one species of ailuropodine exists, the giant panda (Ailuropoda melanoleuca), and it is found only in China. The same evidence used to estimate the split between the other living subfamilies puts the date of the split between pandas and other bears much further back, to around 20 million years ago, not long after the dawn of the Miocene. 

Horns v. Geography - Relationships Among Rhino Species

White rhino

Rhinoceroses are amongst the largest land animals alive today, exceeded in size only by the elephants. As one might imagine, given their distinctive appearance, the group has a long evolutionary history. What is perhaps less obvious is that the family was once much larger than it is today, with many species living side-by-side. In total, we have so far named something like 100 species of fossil rhinoceros and, while some of those will probably not survive more detailed analysis, it's also true that there must be several we haven't found yet. Either way, it's quite a lot.

Most of these lived during the Miocene epoch (although the family is older than this) with the number of species thinning out during the following, Pliocene, epoch between around 5 and 2 million years ago. Even so, we know of nine species that lived during the later Ice Ages. Four of these, however, did not survive their end, leaving us with the five that - in some cases only just - survive today.

The Last Pangolin in Europe

Ground pangolin

Pangolins are undoubtedly odd creatures. Most obviously, there's the fact that they are covered with an armoured sheet of keratinous scales, making them look somewhat like an animated pine cone. No other mammal has this feature or anything much like it. But, even ignoring this, they are still unusual, with their narrow diets, conical snouts, digging claws, and long, broad tails. 

The animals that they most resemble are probably anteaters, especially the smaller species. At one time, they were even classified together with the anteaters, but there are some significant skeletal differences, especially in the structure of the backbone that indicate they are clearly distinct. Furthermore, anteaters originated in South America, while pangolins are known only from Africa and Asia, so it's long been recognised that the resemblances are actually due to parallel evolution, with the animals having a similar diet.

Were 'Cave Lions' Really Lions?

A theme that crops up on this blog every now and then is that some animal that many people probably assume is a single species is actually two or more. There are, for example, three species of zebra, three jackals, and seven different kinds of musk deer. The lion (Panthera leo) is not one of these animals; there really is only one species alive today - and it's been around for a long, long time.

I remember a few years ago, at London Zoo, I happened to be passing the lion enclosure when one of the keepers was giving a talk. The lions at the zoo were obtained from the Gir Forest in Gujarat, India, rather than being the African sort. The keeper repeatedly referred to "this species" of lion when, for example, he was indicating how much more endangered the Indian population is than the African one.

What's the Closest Living Relative of Whales?

(For the TLDR crowd; just read the last paragraph).

It's been known for a long time that, at the highest level, mammals can be divided into three evolutionary groups based on their method of giving birth: marsupials, the egg-laying monotremes, and the placental mammals. That last group contains around 95% of all living mammal species, including everything from wolves to dolphins and moose to monkeys.

Given that wide variety, it's less obvious how we should divide up the placental mammals into smaller groups that genuinely reflect their evolutionary relationships. It's obvious that, say, cheetahs are members of the cat family and, at a slightly higher level, it's unsurprising that, for example, the dog and bear families are reasonably close relatives of one another. But once you get much higher than that, it becomes less so.

The Many Kinds of Living Marsupial

Ringtail possum
Because not every animal in Australia wants to kill you

This blog probably wouldn't exist were it not for the fact that there are a great many different kinds of mammal alive in the world today. Most of these are placental mammals, giving birth to (relatively) fully formed young that have been nourished by a placenta in their mother's womb. A significant minority, however, are marsupials, which belong to a separate evolutionary line that split from the placentals long before the dinosaurs died out.

Marsupials are diverse animals, in many cases, paralleling their placental counterparts in some key aspects of their anatomy or behaviour. True, they are not quite as diverse as their placental kin - there are no marsupials bats or dolphins, for instance. There are around 350 known living species of marsupial, commonly grouped into 19 "families", and, while is this undeniably small compared with the 5,000+ species and 120 or so families of placentals, it's hardly insignificant.

The Last of the Chinese Zebra-Donkeys

Asian wild asses

With the exception of our own species, few mammals have been the subject of quite so much interest in their evolutionary history as the horse. The number of named species of fossil horse far outweighs the number of species that are alive today. A great many of these are, of course, the older three-toed horses, with all living horses being placed in the single genus Equus.

Today that genus consists of just seven widely recognised living species. But, even among just this genus, and ignoring all the older, extinct ones, there were once many more species than there are today. But just how many is that? That's a matter of considerable confusion and debate.

In a way, that's hardly surprising, especially when you consider the focus of attention that there has been on horse evolution. Even just looking at the living species, not everyone agrees that 'seven' is the appropriate number, with some authorities arguing that particular subspecies are distinct enough that they should really be species in their own right.

Mice, Mice, and More Mice

A common feature of my blog posts, pretty much since the beginning, has been the inclusion of cladograms, tree-like diagrams that show how different species, or groups, of mammal are related to one another. Our knowledge of these relationships is constantly evolving, as we get more and more information, or find different ways of doing the necessary measurements.

In general, though, what happens is that scientists measure a number of different features from the animals that they want to study, and compare which ones have the most in common. These days, these are most likely to be physical measurements, such as fine details of the shape of the skull or teeth, if at least some of the creatures we're looking at happen to be fossils. Otherwise, it's much more likely that the things being compared are stretches of genetic code. The further apart two animals are, evolutionarily speaking, the more differences there are likely to be, and if we pick a gene that both animals possess, and that can accumulate a reasonable number of changes without stopping working altogether, we have a good basis for comparison.

Just What Is a Red Panda, Anyway?

Last week, as it sometimes does, the topic of red pandas came up in conversation. The person I was speaking to was well aware that red pandas are not very closely related to the more famous giant pandas... but he had no idea what they actually are related to. It occurs to me that, while I've often posted on the evolutionary relationships of closely related animals within the various mammal families, I've posted rather less about how the different families are related to one another. So, let's look at that, from the perspective of trying to figure out which mammal family it is that the red panda belongs to.

The red panda (Ailurus fulgens) was first formally described by Frédéric Cuvier, brother of the much more famous Georges Cuvier, in 1825. He gave it the scientific name that it still bears, which translates to "shining cat" because of what he thought it looked like. Of course, this was long before Darwin, so he wasn't suggesting that the animal was literally related to cats, since, like his brother, he presumably thought that all species were created independently. In fact, probably because of the bushy striped tail and the shape of the teeth, he instead placed it within the recently named raccoon family, the Procyonidae.

A History of the Strange-Jointed Beasts

All living species of mammal fall into one of three major groups, representing the lowest branches of the mammalian family tree: the placental mammals, the marsupials, and the bizarre, egg-laying, monotremes. Well over 90% of identified living species fall into the first of those groups, which prompts the interesting question of how we divide those up - what, in short, are the next branches on the tree?

In the strict, old-style, system of classification, the next major level down is that of the "order", groups of broadly similar creatures that are in turn, divided into more than one hundred "families". Primates, for instance, are an order.

What the orders are, and how many of them there might be, has varied a little down the years, but nineteen or twenty would be a good, modern estimate. But, of course, the orders themselves are entirely arbitrary, and, even if they weren't, it isn't as if they all sprang simultaneously from the same stock. In evolutionary terms, there must have been some early branches in the placental family tree from which the "orders" that we know today descended.

The question of how to group the orders together into some higher level pattern is one that mammalogists have been been pondering for well over a hundred years. The problem is that the orders are pretty distinctive - is a moose more like a wolf than it is a monkey? When all you have to go in is physical anatomy, these are not the simplest questions to answer, and it's not surprising that people have come up with different answers.

Weasels in Stone: Mustelid Evolution

Sthenictis, a fossil mustelid

Last September, I began a survey of the weasel family, the largest, and arguably the most varied, family of carnivorous mammals. Since then, I have managed to give at least a brief description of every living species in the family, from stoats and badgers to otters and wolverines. But how do all these animals relate to one another, and where did they come from?

In the past, scientists would work this out by examining the physical features of animals, reasoning that those with the greatest similarity were the most likely to be related. By adding in information gleaned from fossils. such as their age and location, and any evolutionary changes they may have undergone, it's possible to get quite a lot of information this way. However, today, it is more common to use molecular and genetic information, seeing how genes and the proteins they produce have changed in subtle, often invisible ways, over the course of time. Taken together with the fossil information, this can reveal many relationships that might otherwise remain obscure.

In the very first attempt at scientific classification of animals, way back in 1735, weasels were grouped together with martens, polecats, and civets as a sort of collective group of small slender mammalian carnivores, although otters and badgers were placed separately.  However, it was not until 1817 that the weasel family was formally named by German naturalist Johann Gotthelf Fischer von Waldeheim. That, of course, was still before we understood evolution, and it's hardly surprising that we've moved on since then.

Badger Badger Badger

The European badger (Meles meles) is a very familiar animal across Europe, the animal we immediately think of when we think of "badgers". Its distinctive black-and-white face markings make it instantly recognisable, but, in fact, it has quite a range of different appearances, with variations in size, fur colour, and skeletal anatomy that allow it to be divided into a number of subspecies. This variation has been the source of some confusion when it comes to separating this species from its closest relatives.

It used to be thought that the European badger could be found throughout almost the whole of Europe and Asia, avoiding only the tropics, deserts, and the depths of Siberia. As a result it was called, quite reasonably, the "Eurasian badger". Over the last decade, that view has changed. Firstly, it became clear that the badgers of Europe and Asia were different enough to be considered separate species, and then that the badgers of Japan were likely different from those elsewhere in Asia. The suggestion has a venerable history; it was first made in the 1840s, but subsequently ignored when scientists decided that Eurasian badgers were really just one species that happened to be quite variable in appearance.