dailyfossil:

Paramylodon - Harlan’s Ground Sloth

Mounted specimen on display at the Page Museum, Los Angeles, California, USA.

When: late Pliocene to Pleistocene (~5 million to 11,000 years ago)

Where: Central and North America

What: Paramylodon is the most common of the ground sloths found at the La Brea tar pits fossil site in southern California. Megalonyx is found here as well, and though the two sloths resemble one another very strongly, they are on opposite sides of the family tree of sloths. Megalonyx is very closely related to the living two-toed sloth, but Paramylodon and its kin form a group at the base of sloths with no living relatives. The last common ancestor of these sloths lived roughly 30 million years ago. A suite of detailed morphological features distinguish these two sloths, found thoughout the skeleton, but perhaps the most amazing is that Paramylodon was somewhat of an armored animal. Imbedded within its skin were many tiny dermal ossicals, which would have served to protect it from the many predators that roamed southern California at the time.

The most complete specimens of Paramylodon come from the La Brea tar pits (which is a very redundant name as la brea means the tar, but hey!). The tar formed tens of thousands of years ago, by natural seepage of the sticky and dense material from the bedrock. The tar pits looked nothing like they do today, however. There were no large ‘lakes’ of tar then. Instead what would occur is occasionally a large seepage would collect and then be covered by leaves and dirt, hiding it from view. This would create a natural trap that would ensnare whichever animal was unfortunate enough to stumble upon it. The large expanses of tar visible today are due to the excavation of the site. The site was recognized as fossil bearing in the early 1900s, bones had been discovered on Rancho La Brea for some time previous to this, but they had not been properly identified as fossils. The Page Museum was opened on the site in 1977 in order to provide both a place for researchers to easily access and study the specimens, and to display the wondrous finds to the people of Los Angeles.

polymags: Mylodon. A kind of huge sloth with immensely powerful fore-limbs. This animal is believed to have torn down or uprooted bodily the trees on the branches of which it wished to feed. (January 1882)

(via scientificillustration)

Tagged: pleistocene megafauna mylodon sloth

Posted on February 26, 2012 via Poly Mags with 92 notes

Source: polymags

biomedicalephemera:

Top: Fossil Megaloceros giganteus with grown man for comparison.

Bottom: Approximation of Megaloceros giganteus in continental European environment.

The Irish Elk (Megaloceros giganteus), which wasn’t really an elk at all, wasn’t actually “Irish”, either. Though its fossils have been extensively preserved in the Irish peat bogs, and were first found in Ireland, this cervid lived throughout Eurasia, all the way east to Lake Baikal.

Their proposed extinction during the last major ice age has been disputed recently, with the dating of more recent bone caches. The current date that’s generally accepted for their (effective) extinction is around 7600 years ago.

Extinct Monsters. A Popular Account of Some of the Larger Forms of Ancient Animal Life. Rev. H. N. Hutchinson, 1896.

Essay on the Theory of the Earth. Baron Georges Cuvier, 1827.