ARMOURED ANIMALS: ANCIENT ARMADILLOS

Glyptodonts are the early ancestors of our modern armadillos that roamed North and South America during the Pleistocene. 

Armadillos, both living and extinct, range in size from the size of an armoured car to the size of a small, family dog. As they evolved over time, the smaller they have become. 

Glyptodonts became extinct at the end of the last ice age. They, along with a large number of other megafaunal species, including pampatheres, the giant ground sloths, and the Macrauchenia, left this Earth but their bones tell a story of brief and awesome supremacy.

Today, Glyptodonts live on through their much smaller, more lightly armoured and flexible armadillo relatives. They defended themselves against Sabre Tooth Cats and other predators but could not withstand the arrival of early humans in the Americas. Archaeological evidence suggests that these humans made use of the animal's armoured shells and enjoyed the meat therein. Glyptodonts possessed a tortoise-like body armour, made of bony deposits in their skin called osteoderms or scutes. Beneath that hard outer coating was a food source that our ancestors sought for their survival.

Each species of glyptodont had a unique osteoderm pattern and shell type. With this protection, they were armoured like turtles; glyptodonts could not withdraw their heads, but their armoured skin formed a bony cap on the top of their skull. Glyptodont tails had a ring of bones for protection. Doedicurus possessed a large mace-like spiked tail that it would have used to defend itself against predators and, possibly, other Doedicurus. Glyptodonts had the advantage of large size.

Many, such as the type genus, Glyptodon, were the size of modern automobiles. The presence of such heavy defences suggests they were the prey of a large, effective predator. At the time that glyptodonts evolved, the apex predators in the island continent of South America were phorusrhacids, a family of giant flightless carnivorous birds.

The ancient Armadillo Glyptodon asper

In physical appearance, glyptodonts superficially resembled the much earlier dinosaurian ankylosaurs and, to a lesser degree, the recently extinct giant meiolaniid turtles of Australia.

These are examples of the convergent evolution of unrelated lineages into similar forms. The largest glyptodonts could weigh up to 2,000 kilograms. Like most of the megafauna in the Americas, they all became extinct at the end of the last ice age 10,000 years ago. The deeper you get in time, the larger they were. Twenty thousand years ago, they could have ambled up beside you in what would become Argentina and outweighed a small car.

A few years back, some farmers found some interesting remains in a dried-out riverbed near Buenos Aires. The find generated a ton of palaeontological excitement. Fieldwork revealed this site to contain two adults and two younger specimens of an ancient armadillo. These car-size beasties would have been living and defending themselves against predators like Sabre Tooth Cats and other large predators of the time by employing their spiked club-like tails and thick bony armour.

Glyptodonts were unlikely warriors. They were grazing herbivores. Like many other xenarthrans, they had no incisor or canine teeth but had a number of cheek teeth that would have been able to grind up tough vegetation, such as grasses. They also had distinctively deep jaws, with large downward bony projections that would have anchored their powerful chewing muscle.

Image Two: By Arentderivative work: WolfmanSF (talk) -  http://de.wikipedia.org/wiki/Bild:Glyptodon-1.jpg, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=665483

SQUIRRELS: SHADOW TAILS

One of the little animals I see daily in Kitsilano, Vancouver, are the very busy, highly comic rodents we know as squirrels. 

They spend their days busily gathering and caching food and their nights resting from all that hard work. 

My neighbourhood has mostly Eastern Gray squirrels, Sciurus carolinensis (Gmelin, 1788) who come in a colour palette of reddish-brown, grey (British spelling) and black. 

These cuties have bushy tails and a spring in their step — racing around gathering nuts, finding secret hiding spots to cache them, teasing dogs and generally exuding cuteness.

We find the first fossil evidence of tree squirrels in the Pleistocene. At least twenty specimens have been found of Sciurus carolinensis in Pleistocene outcrops in Florida on the eastern coast of the United States. Over time, their body size grew larger then shrunk down to the 400 to 600 g (14 to 21 oz) weight we see them today.  

Eastern Gray squirrels have two breeding seasons in December-January and June-July. This year has been unseasonably warm. On Vancouver Island, the Eastern Grays bred again in early September. One wonders if the heat dome killed off the July litter, and with the return of more favourable weather, the parents have been induced to breed again.

While they are not native to Vancouver, they are plentiful. They were introduced to the region over a hundred years ago and have been happily multiplying year upon year. 

Our native species are the smaller, reddish-brown, rather shy Douglas squirrels, Tamiasciurus douglasii (Bachman, 1839), and the nocturnal Northern Flying Squirrels, Glaucomys sabrinus (Shaw, 1801).  

Sciurus, is derived from two Greek words, skia, meaning shadow, and oura, meaning tail. The name choice is poetic, alluding to squirrels sitting in the shadow of their tails. 

The specific epithet, carolinensis, refers to the Carolinas on the eastern seaboard of the United States, an area that includes both North and South Carolina. It was here that the species was first recorded and still rather common. In the United Kingdom and Canada, Sciurus carolinensis is referred to as the Eastern Gray or grey squirrel — and though adorable is an invasive species. 

In the United States, Eastern is used to differentiate the species from the Western Gray or Silver-Gray squirrel, Sciurus griseus, (Ord, 1818). 

The Ord here, of course, is George Ord, the American zoologist who named the species based on notes recorded by Lewis and Clark in the early 1800s. If you fancy a read, check out his article from 1815, "Zoology of North America." It is charming, anachronistic and the first systemic zoology of America by an American. 

In the Kwak̓wala language of the Kwakiutl or Kwakwaka'wakw, speakers of Kwak'wala, of the Pacific Northwest, use the word ta̱minasux̱, to express: "that is a squirrel." 

The word for shadow in Kwak'wala is gagumas and tail is ha̱t̕sa̱x̱ste' — so I will think of these wee wonders of the Order Rodentia in the family Sciuridae as the Gagumas ha̱t̕sa̱x̱ste' of Khahtsahlano.