Saturday, 28 January 2023

The Raccoon Family

It has not always been easy to determine where exactly raccoons fit within the larger mammalian family tree. In part, this is because it's difficult to pin down exactly what defines them and makes them distinctive from their closest relatives. We can get some idea of this by looking at the taxonomic history of the group.

The scientific classification of living organisms we use today has its origins in the 1758 edition of Systema Naturae, by Carl Linnaeus. Raccoons live only in the Americas, but even in 1758, Linnaeus was aware of the existence of raccoons, having heard about them from his friend Peter Kalm, who had observed them in what were then the colonies of Pennsylvania and New Jersey. Based on Kalm's description, Linnaeus named this new species Ursus lotor - the "washing bear". It was one of four species of "bear" that he identified in that work, only one of which we'd still consider to be such today.

Sunday, 22 January 2023

Miocene (Pt 37): The Miocene Oceans

Xiphiacetus
Given their extreme adaptations to a life at sea, it should not be surprising that whales and dolphins have a long evolutionary history. Even at the dawn of the Miocene, when seals were at best, only very recent arrivals, and may still have been semi-aquatic, like otters, the cetaceans were already well-established. A time-travelling whale-watching expedition at almost any point during the Miocene would likely have been just as rewarding as one today and, especially so far as one would have been able to see them above the waves, the animals you would have been spotting would not have looked all that different.

At a more detailed anatomical scale, that would have been less true and many of the creatures would not have been as closely related to the modern forms as one might have supposed. Today, the largest number of cetacean species belong to the "true" or "oceanic" dolphin family, including not only all of the sea-going dolphins but some larger animals such as killer whales. But in the Miocene, true dolphins seem to have been comparatively rare and we know of very few fossils predating the subsequent, Pliocene, epoch.

Sunday, 15 January 2023

Grumpy Old Voles?

Meadow vole (a related species)
It should go without saying that the behaviour of young mammals changes as they approach, and eventually reach, adulthood. Obviously, there's the development of the mating drive, but there are also social changes, as the animal gains independence, first from suckling, and then more generally from its parent(s), often leaving home, whether to live alone or to find a new pack where its potential mating partners aren't also its own siblings. 

Drawing parallels between these changes and the way that humans develop isn't without risk; the complexity of our society, the existence of culture and so on significantly colour how we behave. But that's not to say that such parallels don't exist, and can't tell us anything, even if it's only how we evolved. We are, after all, still affected by our biology and evolutionary history in at least some respects. For instance, it's notable that exactly how animal pups are raised by their mother can affect how they behave as adults, even if the details are going to be less complex than they are with human child-rearing.

Sunday, 8 January 2023

Dunnarts in the Sandhills

It's a recurring theme of this blog, especially notable in last year's series on Old World leaf monkeys, that a great many mammalian species are threatened in some way. Population numbers of many species are declining, to the point that their continued existence is in doubt, often due to human encroachment on their habitat, but also due to the habitat itself changing as climate change continues. In this context, the quest of zoologists to understand how mammals (and other animals) behave is not just one of intellectual curiosity but can be of direct benefit to the creatures themselves.

For example, it is useful to conservation efforts to understand not only where a given species lives, and the habitat requirements it may have, but how it makes use of that environment. (Obviously, there's more to it than this, for example, how different species in the same area interact with one another but we'll stick with this one point for today). What particular features of the habitat are important to it? How much land does it need? How is its population distributed across the area? 

Sunday, 18 December 2022

Prehistoric Mammal Discoveries 2022

New reconstruction of the sabretooth cat
Homotherium, showing that the teeth
would not have been as visible as popularly
supposed
2022 approaches its conclusion and I have to say that, while far from perfect, it was an improvement on the previous two years. There were a couple of weeks without posts this year, one for positive reasons, and one less so, but overall it has been good. Next year, you can look forward to something other than monkeys in my "family" series of posts and also to the conclusion of the long-running Miocene series, which should be as early as February. Until then, here is the now-traditional year-end look back at the paleontological discoveries that didn't quite make it into the blog.

Large Herbivores

Probably the most distinctive thing about deer is that the males have antlers; branching bony head ornaments that are shed and regrown each year. This naturally raises the question of how this evolved, since no other animal has quite the same thing. Acteocemas was an Early Miocene deer, but despite living very early in the group's evolutionary history, it already had antlers that split into two near the tip - which the horns of animals such as cows and true antelopes never do. A Spanish fossil of the antlers described earlier this year showed that it was already shed and regrown, but microscopic analysis indicated that it appeared to have been present for over a year, suggesting longer a more irregular pattern of shedding that must have changed to the seasonal pattern we are familiar with more recently, perhaps in the Middle Miocene.

Sunday, 4 December 2022

Leaf-Eating Monkeys: Leading by a Nose

Proboscis monkey (male)
Perhaps the most distinctive and well-known of all the colobine monkeys is the proboscis monkey (Nasalis larvatus). Sufficiently distinctive that it's hard to confuse it with anything else, it was first described as a species all the way back in 1787 by botanist Friedrich von Wurmb, then working for the Dutch East India Company, and given its own genus in 1812.

Indeed, it is strange enough that, during the 20th century, it was assumed to represent a very early side-branch in colobine evolution, existing outside all the other groups in the subfamily. That wasn't just because of its odd appearance, but also because it had two extra pairs of chromosomes to every other colobine monkey. But it turns out that that's a false signal and that, not only are proboscis monkeys a relatively recent branch within the subfamily, their closest relatives include the snub-nosed monkeys whose noses are noted for being extraordinarily short.

Saturday, 26 November 2022

Miocene (Pt 36): Dawn of the Seals

Allodesmus
In this series so far, I have covered the mammalian wildlife of the Miocene continent by continent, showing how the diversity of animals then was just as great as it is now. But there is a group of mammals that a time traveller to the period would have been able to observe along the coasts of those continents - especially during their breeding season - that I have not yet mentioned.

Today, the seals are divided into two subfamilies (I have reviewed all living species of seal here): the phocine or "northern" seals, which live in the Northern Hemisphere, and the monachine or "southern" seals, which are primarily found in the Southern Hemisphere, but do include three living species in the north.