Sunday, 16 September 2018

Modified Munchies of Many Mouse-eared Myotises

In the modern system of taxonomy for the classification of living things, a genus is  group of closely related species. It is the lowest mandatory level of classification, apart from 'species' itself, and forms the first half of a creature's scientific name. Thus, Panthera, for example, is the genus containing lions, tigers, leopards, snow leopards, and jaguars.

As such, we'd typically expect a genus to contain only a small number of species - it is, after all, the smallest standard grouping of species that there is. And, at least for mammals, this is typically the case. Many genera, in fact, have only one known species, or at least only one that isn't extinct (as is the case for our own genus, Homo, for example). But there are some exceptions, cases where there are so many incredibly similar species that we just have to lump them all together.

The single largest mammal genus, as commonly defined today, is Crocidura, which represents nearly half of every species of shrew we know about. But even the second largest, Myotis, is a whopper.

Sunday, 9 September 2018

The Pig Family: Peccaries Are Not Pigs

Over the the year so far, this series has described every living species of pig. Yet there are some animals that might seem to be missing. Found across much of Latin America, and up into the southwestern USA, we can find animals known as peccaries. These certainly look like pigs, and, unlike razorbacks, which can also be found in the US, they are genuinely wild animals, not the descendants of domesticated ones that happen to have escaped.

The reason I haven't mentioned them so far is, as the title of the post makes apparent, that they aren't actually pigs. So why the heck not, and what are they, if they're not pigs?

Sunday, 2 September 2018

400th Synapsida

With this being the 400th post at Synapsida, it is once again time for my biennial piece of navel-gazing, in which I see what has happened over the last 100 posts, and where I might be going next.

There's no change to the most frequently used tags over the last 100 posts, with evolution and behaviour topping the list, as might be expected, given the general theme of the blog. (I'm ignoring tags directly related to particular 'series' here, of course). Bubbling under are topics related to diet, sociability, and reproduction. Given some of the animals I have been looking at, it is unsurprising - if rather depressing - that endangered species are also mentioned quite frequently.

Sunday, 26 August 2018

Miocene (Pt 9): The First Sabretooths in Europe

Amphimachairodus
When hyenas first evolved, they were small, tree-dwelling animals, searching for rodents, birds, and the occasional insect among the branches. By the Late Miocene, they had already begun to come down from the trees, but many were still small, and resembled a mongoose more than a modern hyena. A few, such as Thalissictis, were larger, an early step on the path to the more familiar forms of today.

During the early part of the Late Miocene in Europe, however, the older forms still dominated, evidently showing that their lifestyle was still a valid one, perhaps in part because they weren't directly competing with their more "modern" looking relatives. Nonetheless, as the Late Miocene dawned, newer species of hyena began to appear, and these had a more dog-like appearance than their relatives. As a result, it has been estimated that as many as 20 different species of hyena may have lived in Eurasia at the time, with a greater diversity than today.

Sunday, 19 August 2018

Rabbit v. Rabbit

Mountain cottontail
There are literally thousands of different mammal species currently recognised. Most of them are small, and a great many of them can be quite hard to tell apart at first glance. Or even second glance, quite frankly.

The reason that they look so similar is that some body plans have been particularly effective, allowing the creatures possessing them to survive and multiply across the globe. But, if they're so similar, why doesn't one species, over the course of time, drive the other to extinction? Even if one isn't even just marginally better at doing whatever it does than the other (and, since they aren't literally identical, that's unlikely) then sheer bad luck ought to hit one or the other of them eventually.

Sunday, 12 August 2018

The Pig Family: The Strange Case of the Sulawesi Pig-Deer

Sulawesi babirusa
Warthogs are fairly odd-looking animals, as are forest hogs, among others. But, at least to my mind, when it comes to wild pigs, nothing quite beats the babirusas.

These strange looking pigs inhabit the island of Sulawesi in Indonesia. Unlike most of the others in the group, this has been an island for far longer than pigs have been in existence - when sea levels were lower, most islands to the west were joined with Asia, and those to the east with Australia, but the waters around Sulawesi are so deep that it remained isolated. I've mentioned this before, in the context of warty pigs, so it's interesting to note that those channels must have been crossed by wild pigs on no less than three occasions (the third sort of Sulawesian pig, Celebochoerus, died out in the Ice Ages).

Sunday, 5 August 2018

False Deer-Llamas of Bolivia

Theosodon
(the nasal bones are that 'bump' on the forehead
just forward of the eyes)
Australia is an island continent, separated from the rest of the world's landmass for millions of years, allowing it to develop its own unique wildlife, from kangaroos and wombats to bandicoots and emus. The only other island continent we have today is Antarctica, which has no native land mammals at all (or emus, obviously).

In geological terms, however, South America was also an island continent until relatively recently, only joining North America three million years ago, towards the end of the Pliocene epoch. Even today, the strip of land connecting the two is only 35 miles (60 km) or so wide at the narrowest point, both narrower and longer than that connecting Eurasia to Africa. This means that, like Australia, South America had a long history of so-called "splendid isolation", and it evolved a number of unique animals in the process.