Oligocene (Pt 14): The Southern Horses That Weren't

Scarritia

30 million years ago, South America obviously lacked horses, since those (still three-toed at the time) originated in the north, and the southern continents had long been isolated from their homeland. What it did have, however, were a group of mammals called the notohippids, a name that literally translates as "southern horses". While they might not be closely related, the name might lead one to suspect that they had at least a resemblance to the modern animals.

They didn't.

Well, not much. When the name was originally coined, for the Miocene genus Notohippus, back in 1891, it was assumed that they really were horses, or at least closely related. This is because of the shape of their teeth which, did indeed resemble those of equines. It only took until 1914 to realise that, teeth aside, they weren't very horse-like. That their teeth were similar suggests a similar diet with plenty of tough vegetation, and their head was elongated in an almost horse-like fashion to accommodate them... but that's pretty much where the resemblance ends. For one thing, they had claws, not hooves; their bodies were also stockier, albeit with long limbs that may have given them a certain agility.

Gorilla Communities

It is, I would hope, well-known that the closest living genus to our own is that of the chimpanzees and bonobos. The second-closest is, of course, that of the gorillas. There are two species of gorilla, each with two subspecies, and both are considered "critically endangered" - literally on the verge of extinction. For one species, this is, as one would expect, largely due to their tiny surviving population and restricted range. 

There are many factors that we need to consider when attempting to reverse this, and some of them also have a bearing on the evolution of our own species. Among these is the question of how gorilla groups are socially constructed and how they interact. It turns out that here, we can't just consider "gorillas" en masse because the two species behave in very different ways. For example, while one species can have multiple silverback males in the same troop, this is rare (but not unheard of) in the other.

Delphinids: Spotted, Striped, and Spinning Dolphins

Pantropical spotted dolphin

The closest relatives of the common and bottlenose dolphins, which are perhaps the most familiar species to the western public, are those in the genus Stenella. Or at least, that might be true, because there has been a lot of confusion about the genus over the years.

It was first created in 1866 as a subgenus within Steno, the "narrow-beaked" dolphins, and contained just one species. It became a full genus in 1934,and by the end of the 20th century was agreed to contain five species - all of which had, in fact, been named before 1866. Since then, our understanding of genetics has greatly improved, and it has become clear that these various species cannot be so neatly arranged on a family tree as we might like.