Saturday, 1 October 2022

Miocene (Pt 35): Crash Bandicoot and the Giant Platypus

Nimbacinus
When we think of marsupials, the animal that's probably most likely to come to mind first is the kangaroo, likely followed by the koala. Both of these animals, along with wombats and possums, belong to the largest order of marsupials, technically referred to as the diprotodonts - a term that literally means "two front teeth" on account of the enlarged, vaguely rodent-like incisors that characterise the family. These are used to clip at vegetation, since the group is overwhelmingly herbivorous.

This was less true in the Miocene, and that's because of the existence of marsupial lions. Or, more accurately, of thylacoleonids, members of the "marsupial lion" family, since the truly lion-sized animal best known by that name didn't live until much later. The group originated towards the end of the previous epoch, when some herbivorous, probably wombat-like, animal switched to a more meaty diet, its front teeth becoming blade-like in order to cut into flesh. They seem to have prospered during the Miocene, with three different genera currently recognised.

Sunday, 25 September 2022

Ain't No Mountain High Enough

Almost anywhere you can go on Earth, you will find life. A field of molten lava might be going a bit far, but otherwise, life seems to have adapted to almost every environment, from ridiculously hot springs at the bottom of the sea bed to barren ice fields to microscopic cracks in apparently solid rock far underground. Much of this life is, of course, far too small to see with the naked eye - bacteria or their cousins the archaea. Mammals are somewhat more limited; we don't find them inland in Antarctica, for instance. But what are the limits beyond which even the best-adapted mammals cannot live comfortably?

One of the easier limits to measure in this way is altitude. This is, after all, a fixed value, whereas factors such as temperature can vary throughout the year. Certainly, it would be useful to know whether a given species can survive as the world warms, but that can be a complex question to answer. When it comes to altitude, we simply have to go and look. For this reason, when describing the habitat of a creature in a conservation catalogue or the like, the altitudinal range of the animal is often described in numeric terms, while the preferred climate is described more vaguely.

Sunday, 18 September 2022

The Hybrid History of North American Deer

There are five species of deer native to the US and Canada. Two of these, the moose and the caribou, are distinctive animals with no especially close living relatives. The elk, while perhaps not as distinctive in appearance as these two, is even more distant from the others in evolutionary terms. The other two, however, are the white-tailed deer (Odocoileus virginianus) and the mule deer (Odocoileus hemionus) which not only look similar to one another but are, indeed, each other's closest relatives.

When I discussed these two species in detail last year, I mentioned the existence of the "black-tailed deer" a subgroup of mule deer with tails of a more solidly black colour than others of their kind. The black-tailed deer are native to the Pacific Northwest and are generally considered to consist of two subspecies of mule deer that share a common ancestor that split off from other mule deer early on. Since are subspecies, not full species, it should come as no surprise to discover that they hybridise with other mule deer where the two come into contact, although, if anything, this happens more often than we might expect.

Sunday, 11 September 2022

Leaf-Eating Monkeys: Borneo and Beyond

Hose's langur
Borneo is the third largest island in the world (after Greenland and Papua New Guinea), being about 10% larger than Texas, and around three times the size of the entire UK. The interior is rugged and mountainous, especially in the north, and, in its natural state, almost entirely covered in dense jungle. This is a perfect environment for spawning new species, which can easily become isolated from one another and still have plenty of lush vegetation to feed upon. It's also ideal for hiding these species from naturalists so that it's possible that even the species we currently recognise from the island are not a complete list.

As was common at the time, several species were named in the 19th century, often by naturalists unaware that what they'd just described had already been named in some obscure source by somebody else. Even after the general taxonomic tidying up of the 20th century, however, no fewer than four species of the genus Presbytis - loosely speaking, the Indomalayan group of langurs - were still recognised as living on Borneo.

Sunday, 4 September 2022

600th Synapsida

The time has come around once again for my approximately biennial piece of navel-gazing, as I celebrate this blog reaching its 600th post, almost 12 years after it first started. Since the 500th post, the world has (mostly) emerged from the perils of COVID and now tends to have other issues on its mind that biological science is less likely to be helpful with - not that I deal with epidemiology or virology here anyway. But let's take the traditional look back at what did appear on the blog during that timeframe and, allowing for the fact that I usually pick the topic on the day the post goes up, what might be coming over the next two years.

Animal behaviour and evolution remain the two most popular topics of my posts, and it's unlikely that that's going to change too much. However, there were also several posts on sociability specifically, as well as things such as diet and habitat and a more than usual number of posts on anatomy. In terms of the types of animals covered, where posts were on a particular species and not part of an ongoing series, rodents top the list, followed by bats. These are, of course, the top two mammalian groups in terms of number of species, but, while rodents are relatively easy to study, bats are rather less so... but perhaps that just means that studies on them tend to stand out more and pique my interest.

Sunday, 28 August 2022

Fossil Martens... or Not?

When talking about fossil animals on this blog I often mention the earliest known example of a particular group. But this often hides a degree of uncertainty, or even controversy, because such the exact identity of such fossils can be difficult to pinpoint. That's partly because, being, by definition, older than other fossil examples of the group, they are also the most likely to be incomplete or poorly preserved. Often, since we're talking about mammals here, the "oldest known fossil" may consist of little more than a distinctive tooth. 

The second, and perhaps even bigger, problem is that the further you go back to the origin of a group the more it blurs into whatever preceded it. Even if we had perfect remains, or if we could travel back in time and see the animals in life, or take blood samples from them for genetic analysis, there would always be a question of what exactly we were looking at. Where do you draw the line when, in reality, one group will have slowly and perhaps imperceptibly, evolved into a newer one?

Sunday, 21 August 2022

Food for Thought

The word "primate" means "of the first order" and the group of mammals is so-named because, even in the days before evolutionary theory, it was recognised that this is the group that includes our own species. I've previously discussed how primates are distinguished from other mammals, and one of our identifying features is that we tend to have larger brains in proportion to our bodies. (Not uniquely so, of course, given the existence of dolphins and their kin, but certainly well above the average).

But why? What is it about the primate lifestyle that, over the last 60 million years or more, has resulted in them growing larger brains than other, similarly sized, mammals? This is obviously a significant question, since it relates to what is undeniably the key defining feature of our own species and might explain why our planet is inhabited by sapient urbanised monkeys rather than, say, sapient city-building cats.