Tree-Dwelling Almost-Lemurs of the Canadian Arctic

Northern Canada, it has sometimes been noted, can get a bit cold. The northern coasts, and the islands beyond them, are covered in treeless tundra, the permanently frozen subsoil preventing anything that needs deep roots from growing there. The interiors of the more northerly islands don't even have that much, just permanent fields of ice and snow. 

The most northerly island in Canada is Ellesmere Island, whose most northerly point is not far from being the most northerly piece of solid land on the planet, only beaten by parts of Greenland. Midsummer temperatures reach a daily high of about 9°C (49°F) in midsummer, and it often snows in July. Winter temperatures regularly drop below -35°C (-31°F) on January nights. So, yeah, that's uncomfortable.

Before the Monkeys: Primates in North America

Anaptomorphus,
an omomyid from Wyoming

The primates are one of the larger groups of mammals, with literally hundreds of living species known. Naturally, there is a great deal of diversity across the primates but, at the highest level, we can divide them into two main suborders. These used to be referred to as the "lower" and "higher" primates, but that's misleading because the so-called lower primates have been evolving for just as long as the higher ones. It isn't as if they gave up one day and stopped evolving towards some ultimate goal of becoming human. 

So, instead, when we aren't using the technical terms strepsirrhine and haplorrhine, today we tend to call them "wet-nosed" and "dry-nosed" primates, based on whether their nose is moist like that of a dog or not. When most people think of primates, however, it's likely the haplorrhine, or "dry-nosed" primates that they think of first, since this is the group that includes all the monkeys and apes - as opposed to lemurs and the like.

The Mammal That Lived Like a Woodpecker

Plesiadapis

The time since the extinction of the non-avian dinosaurs is traditionally divided into seven "epochs". Unsurprisingly, the more recent the epoch, the more familiar the animals that inhabited the Earth at the time. In my current long-running series on the animals of the Miocene (the fourth of these epochs, and also the second-longest) I have been able to talk about a number of mammals that can at least be placed into groups we understand. Horses may have had three toes, elephants may have had four tusks, and so forth, but at least we can tell, without any great difficulty, that they are, in fact, horses and elephants.

As you'd probably expect, this gets harder the further back you go. Firstly, even animals belonging to familiar groups are getting further away from their present-day forms. There comes a point where whales still walked on land, for instance. Secondly, the further we go back, the more animals we find that didn't leave any modern descendants, and, indeed, weren't even closely related to anything that did (Smilodon, for instance, has no living descendants, but it's still pretty obviously a cat). That can sometimes make it harder to say where such animals fit into the mammalian family tree or, perhaps more importantly, how they lived and behaved.

Twilight of the Almost-Primates

The primates are one of the major groups within placental mammals, currently considered to contain at least fourteen different living 'families', and probably more. Given this, and the fact that they are fairly distinctive, it's not surprising to discover that they are also a very ancient group. Genetic studies, back by estimates of how frequently mutations ought to occur, imply that they may date all the way back to the extinction of the dinosaurs, or at least its immediate aftermath.

The oldest undisputed fossil primate we currently know of isn't quite that old, however, and dates back 'only' 55 million years to the dawn of the Eocene epoch. I have to add the word 'undisputed' to that, though, because it wasn't alone - a number of other very primate-like animals did live at the same time, and, indeed, somewhat earlier.

These animals are collectively called 'plesiadapiforms', and it would be fair to say that there is still some considerable debate as to what they actually were. Just as with the question as to how many families of living primate there are, this depends not on how the different groups are related, but on where we choose to draw the lines between them. In the case of living families, the question is whether we consider marmosets and night monkeys to belong to the broader capuchin family, or whether we consider them different enough to count as families in their own right. In the case of the plesiadapiforms, it's whether they're really weird early primates, or whether we consider them to be merely close relatives.