Pliocene (Pt 3): Of Gazelles and Three-toed Horses

Hipparion

The Zanclean Flood may have been a catastrophe of epic proportions, but, so long as you were above where the flood waters eventually stopped, Europe at the dawn of the Pliocene was a fairly pleasant place. The weather was warmer than today, and, apparently wetter too, which might not be what time-travelling tourists would be looking for, but was certainly good news for the plants that were actually there. Where places like Spain, Italy, and Greece are today dominated by... well... "Mediterranean" scrubland, back then they would have been considerably greener. And what's good for plants is good for herbivores.

Especially when it comes to cloven-hoofed animals, many of these would have been animals that would have been, at least in general terms, familiar to us. Not necessarily familiar to us from Europe, though, since, in addition to pigs, bovines, and deer, there were also a number of antelopes. These were mostly members of the gazelle subfamily, although there were others, including some, for example, related to the modern sable antelope. The gazelles included Hispanodorcas, a small and slender antelope with slightly twisting horns, with fossils found in southern Spain. However, some were even closer to the gazelles of today, to the point that, if, like most people, you'd be pressed to tell the difference between a Dorcas gazelle and a Speke's gazelle today (or at least, to know which one was which), you'd probably not have identified these as anything different, either - although at least some of them were smaller than any living species, which might have helped.

What is a Primate?

Brown lemur

In 2012 and 2013, I finished off the year by posting short(ish) responses to questions entered into search engines that had, according to the blogger interface, led people to Synapsida. I didn't do this last year, because the great majority of the questions were ones I had already answered - perhaps an artefact of how many posts there are now at this blog. But somebody did ask "what is the definition of a primate?" and that struck me as something I could expand on at length. So here we are. What is a primate?

The simple, dictionary, definition is "a member of the order Primates". That's obviously a circular, and rather unhelpful, definition, but, then dictionaries aren't the same thing as encyclopaedias. But even it requires picking apart a bit. For a start, note the capital 'P' in the word "Primates". This indicates it's the name of a discrete thing, and not just the plural of the word "primate". It's a Latinate word, like "Rodentia" for the order of rodents or "Proboscidea" for the order of elephants and their extinct kin. Which means that it may not be pronounced the way you think; it has three syllables: Prime-ATE-eez. It literally means "of the first rank", because, you know, anything with us in it has to be of the highest rank. (Hence the title "primate" given to some high-ranking bishops).

The Smell of Success

One of the noticeable features of mammals, when compared to other vertebrates, is that they tend to have a highly developed sense of smell. Most vertebrates can smell, even if, in the case of fish, it's not quite what we'd think of by that term. Indeed, the sense of smell is pretty poor in most fish (sharks are among the exceptions, hence that blood-in-the-water thing), and it's also rubbish in birds, and not too great in many amphibians. It's rather better in reptiles, but the snakes, which appear at first glance to be really good at it, actually do so by cheating (more on that later).

But, by and large, the sense of smell reaches its apogee with the mammals. It's not just dogs that have a far better sense of smell than you do. It's also mice, deer, cats, and many others besides. The mammalian olfactory system is superbly evolved, and this dates right back to the origin of the class. In short, it's usually far better than anything we've got.

Except... um... we are mammals. So what gives? Why are we humans so useless at something that our fellow milk-giving relatives have perfected? Something that, presumably, has a lot to do with the success of mammals as a class?

The Dog Family: Wolves, Dogs, and Dingoes

Eurasian wolf

The best known and most familiar of the species in the dog family is surely the grey wolf (Canis lupus). This is not least because it is the one that we happen to have domesticated, and which most of us see just about every day. Even the wild form is so familiar that there are a great many wildlife documentaries and web pages out there that cover the species better than I can in one blog post, and I don't want to go too much over that ground. But nonetheless, for the sake of completeness, at least some sort of overview is needed here.

The term "grey wolf" is the generally accepted one for the species as a whole. While there are other species that are referred to as wolves, this is the one that we generally mean when we say the word "wolf" without qualification. Most other terms, such as "timber wolf", "steppe wolf", and so on, refer either to groups of one or more subspecies, or are simply alternative terms for the same animal. Once being spread throughout almost the entire Northern Hemisphere (albeit to only a limited extent in Africa), it is unsurprising that there are rather a lot of subspecies.

But how many? That's a question of some debate. I have talked before about how difficult it can be, in practice, to separate one species from another; the problem is even worse when you're trying to count subspecies. One scheme, for instance, has as many as 24 subspecies in North America alone, while another, more conservative, scheme recognises just twelve worldwide. There are a great many opinions that lie somewhere in between.

Claws of the Bear-Dogs

Arctocyon primaevus

Over the four or so years that this blog has been running, I have covered a number of discoveries of or about fossil mammals. These have come from various epochs within, and beyond, the Age of Mammals, and so are a wide range of different ages. But I don't believe that I've ever previously discussed a fossil from the very first epoch of the Age of Mammals, the Paleocene.

This is partly because, being the oldest, it's not an epoch from which very many good quality fossils survive - at least, as compared with later epochs (as opposed to, say, comparably short periods during the Permian). On the other hand, though, it's obviously an important one, because this is the time during which mammals rose to inherit the Earth in the wake of extinction of the dinosaurs. The great diversity of mammals that we see today had much of its origin in the explosive radiation of new forms that first occurred during the Paleocene. Few modern groups are recognisable from this time, but we do see a number of immediate ancestors of those later groups.