Posts Tagged ‘Megalonyx jeffersonii’

Did Eremotherium laurillardi Supplement its Diet with Sea Weed?

July 13, 2014

Eremotherium laurillardi, a species of giant ground sloth, apparently was abundant along the Georgia coast during the Sangamonian Interglacial (~132,000 BP-~118,000 BP).  Fossils of this species have been found at 7 of the 9 known coastal fossil sites of Pleistocene Age. It was really a spectacular beast growing as large as 18 feet long and weighing 6000 pounds.  When it sat on its haunches, it was even taller than a mammoth.  It disappeared from the state when the climate turned colder, probably some time between ~75,000 BP-~30,000 BP.  The fossil record is too incomplete to determine exactly when this species succombed to the cold in this region.  Eremotherium continued to exist in South America until the end of the Pleistocene.  Two other species of ground sloths  were better adapted to the cold and likely lived in Georgia as recently as 11,000 BP.  Jefferson’s ground sloth (Megalonyx jeffersonii) and Harlan’s ground sloth (Paramylodon harlani) were able to survive subfreezing temperatures by denning in underground burrows. (See: https://markgelbart.wordpress.com/2012/10/10/some-giant-ground-sloths-dug-long-burrows/).

eremotherium and human

Size comparison between Eremotherium laurillardi and a man

Eremotherium primarily ate leaves and twigs.  However, I wonder if they supplemented their diet by foraging on seaweed that washed upon the beach.  Because this species frequented the coast, I’m sure they knew how to swim and may have colonized areas of the mainland or islands by crossing waterways with a depth above their head.  Seaweed is high in certain minerals such as iodine and sodium that are lacking in tree leaves.  Modern day tree sloths are known to obtain these nutrients by raiding human septic tanks to feed on feces.  If Eremotherium ate seaweed, scientists should be able to find abrasions on their teeth from munching seaweed with sand adhering to it.  The scientific literature is silent about this detail, but that may be because scientists have never looked for this evidence.

i-f37fe4c608a50b25cc6d49e7bfdc9d9a-toilet_sloth_M-Stojan-Dolar_April-2010.jpg

Two-toed tree sloth, Choloepus didactylus, climbing from a latrine where it just enjoyed snacking on human shit.  The minerals excreted by humans supplement the diet of this species which consists of tree leaves low in sodium.

There was a genus of South America ground sloths that did gradually evolve into an increasingly aquatic existence.  Five consecutive species of ground sloths in the Thalossocerus genus lived on the coast of Chile and Peru between 9 million years BP-4 million years BP.  The earliest species was Thalossocerus antiquus and the last was T. yaucensis T. antiquus had a shorter nose and abrasions on its teeth from eating seaweed with sand adhering to it.  It likely foraged on the beach and in shallow water.  T. yaucensis had a longer nose and no abrasions on its teeth–evidence it swam deeper into the ocean to feed upon kelp that was washed free of sand by the currents.  Moreover, T. yaucensis had greater bone densisty, a characteristic found in marine mammals; and their anatomy suggests they had strong lips for plucking underwater plants.  Manatees have similarly strong lips.  The environment in this region then was mostly desert, so evolving the ability to subsist mostly on seaweed facilitated the survival of this species in an otherwise uninhabitable landscape.  This genus became extinct at the end of the Pliocene during a major marine extinction event.

Thalassocerus sp., a marine ground sloth that lived on the coast of what’s now Chile and Peru between 9 million BP-4 million BP.  Although Eremotherium also lived near the coast, it probably did not swim in the ocean as regularly as this species.

I propose to any vertebrate paleontologists who read this blog, to check your Eremotherium specimens for sand abrasions.  Maybe you can publish a paper about it and thank me for bird-dogging the idea.

Reference:

Amsen, Eli; et. al.

“Gradual Adaptation of Bone Structure to Aquatic Lifestyle in Extinct Sloths from Peru”

Proceedings of the Royal Society of Science 281 (1782) 2014

Evidence Humans Butchered a Jefferson’s Ground Sloth in Ohio 13,700 years ago

January 11, 2013

Some time prior to World War I, R.C. Niver found the bones of a Jefferson’s ground sloth (Megalonyx jeffersonii) and a bison on his family’s farm located near Norwich Township, Ohio.  The bones were unearthed fom 4 feet below the surface of a bog.  It’s unknown whether he was attempting to drain the swamp by digging a ditch, ploughing, or deliberately looking for fossils.   The bones were examined by the late Oliver Hay, one of the leading paleontologists of the day.  Eventually, the ground sloth bones were placed in a box mislabled as mastodon and put in the attic of the obscure Firelands Historical Society Museum where they rested for over 80 years.  One day, Matthew Burr was cleaning the attic, and he rediscovered the ground sloth bones.  Furthermore, he noticed cut marks on the bone.  Although many paleoecologists believe humans overhunted ground sloths into extinction, before Mr. Burr’s astonishing observation, no direct evidence of human exploitation had ever been reported from the archaeological record.

Photo of the bog where researchers think the ground sloth bones were originally discovered.

The ground sloth bones rested in a box labeled as mastodon in the attic of the Firelands Historical Society Museum for many decades.

Brian Redmond, a curator of the Cleveland Museum, examined the bones.  He counted 5 chop marks and 41 slice marks on an upper leg bone. (Claws, ribs, an ankle, a knee cap, and the lower leg were the other bones found along with the femur.)  Of course, the material was studied thoroughly to discount fraud and other types of morphology such as trampling or river scouring that can produce scratches that resemble anthropogenic marks.  They looked at the marks with a scanning electron microscope and confirmed they were made while the bone was fresh, and they learned they were made with 2 different stone tools.  The placement of the marks also made sense from a butcher’s point of view.  The Indian butcher cut the muscles from the most efficient angles.

There are visible cut marks on this ground sloth femur.  It’s a one of a kind specimen.  The cracks are the result of drying after the specimen was retrieved from the wet bog.

Though the Ohio ground sloth is the best direct evidence that humans exploited ground sloths, 2 other sites yielded assumed evidence.  Scientists found dermal ossicles of a Harlan’s ground sloth at the Kimmswick site in Missouri.  Kimmswick is a confirmed mastodon kill site.  Dermal ossicles make up the armor that used to help protect ground sloths from predators.  Like their cousins, armadilloes and glyptodonts, ground sloth skin was covered in armor, but theirs was covered with thick fur.  The scientists who studied the Kimmswick site believe the dermal ossicles came from a sloth hide carried by paleo-Indians to the mastodon kill site.  The hide later rotted away but the ossicles endured.  The other site is in South America where sloth bones were found associated with human artifacts.

Artist’s rendition of a Jefferson’s ground sloth.  They weighed over a ton.  The Ohio specimen discussed here was one of the largest individuals ever discovered.

Only 3 Jefferson’s ground sloth bones have ever been found in Ohio.  It’s an amazing coincidence that 1 of them showed evidence it was probably killed by humans.  The Indians may have been scavenging it, but I doubt it.  I’m sure they directly killed it.

13,700 years ago, the Laurentide Glacier had retreated northward from Ohio and Lake Erie was young, and recently filled with glacial meltwater.  The climate was rapidly warming but still quite cold during winter.  But as I wrote  in a previous blog entry, these  beasts with neotropical origins could survive cooler climate because they dug deep underground burrows. https://markgelbart.wordpress.com/2012/10/10/some-giant-ground-sloths-dug-long-burrows/

It’s sad that these amazing beasts no longer walk the earth.  When the paleo-Indians hunted them, they probably never imagined they were in the process of completely wiping them out.  They likely had no concept of extinction because they lived in a world of bounty.  To them, a ground sloth was an easy feast in a world before grocery stores existed.  (Incidentally, in his book How to Get out of the Rat Race and Live on $10 a Month George Leonard Herter claims that tree sloth tastes like pork.)  Ground sloths were well adapted to defend themselves against big cats and wolves, but they were helpless against projectile weapons.

Reference:

Lepper, Bradley

“Pre-Clovis Butchered Ground Sloth in Ohio”

The Mammoth Trumpet 28 (1)  Jan 2013