Comments on: The usual suspects

By: David

David — Sat, 31 Jan 2009 21:41:21 +0000

Mark, your’re right about Nothrotheriops being limited to the mountainous West in the Rancholabrean, but Akersten and McDonald (1991) suggest the genus may have been more widespread in the Irvington. It’s reported from the central Florida Pool Branch (McDonald, 1985) and Leisey Pit 1A (Webb et al., 1989). Their theory is that the sloth’s low body temperature didn’t limit its distribution so long as North American climate stayed relatively stable, but the wider swings associated with the late Pleistocene limited the animal’s range to regions where it could find shelter to moderate the extremes (e.g. in caves) or migrate vertically relatively easily (e.g. up and down mountains). References Akersten, W.A. and McDonald, H.G. 1991. Nothrotheriops from the Pleistocene of Oklahoma and Paleogeography of the genus. The Southwestern Naturalist 36: 178-185. McDonald, H.G. 1985. The Shasta ground sloth Nothrotheriops shastensis (Xenarthra, Megatheridae) in the Middle Pleistocene of Florida. In The Evolution and Ecology of Armadillos, Sloths and Vermilinguas, G.G. Montgomery (ed.) pp. 95-104. Webb, S.D., Morgan, G.S., Hulbert, R.C., MacFadden, B.J. and Mueller, P.A. 1989. Geochronology of a rich early Pleistocene vertebrate fauna, Leisey Shell Pit, Tampa Bay, Florida. Quaternary Research 32: 96-110.

By: Mark Gelbart

Mark Gelbart — Mon, 29 Sep 2008 13:02:14 +0000

The presence of Nothroptheriops shastensis in Florida is possible but not likely. Unlike most other eastern sites, Florida’s Pleistocene fossil record is relatively complete and so far I don’t believe any specimens of that species have been found in state. However, specimens of prairie chickens, magpies, and thirteen-lined ground squirrels have been found in Georgia and Florida, so there was some open habitat with Western species. There’s also that disjunct population of burrowing owls.

By: David

David — Tue, 02 Sep 2008 16:17:25 +0000

Thanks for the correction Mark. I should have said they were rare in the East, not totally absent. Faunmap is a wonderful resource but I guess it has it limits. I’m wondering if the Florida record could strengthen the case for the lions preferring open habitat. I’m thinking about Florida also serving as a refuge for Nothrotheriops shastensis, another westerner otherwise.
(see http://www.museum.state.il.us/research/faunmap/)

By: Mark Gelbart

Mark Gelbart — Tue, 02 Sep 2008 13:07:54 +0000

There isn’t an absence of lion fossils east of the Mississippi. The very first Pantera leo atrox specimen was found in Natchez, Mississippi. A very large lion skull has been recovered in Florida, and some fossil specimens of lions have been recovered in South Carolina.

By: dave

dave — Tue, 12 Aug 2008 17:54:13 +0000

We have a preliminary pollen and seed report but that’s going to give us too wide of a snapshot–we can’t say they were deposited at the time of death. Forensic scientists use insects to estimate TOD, but of course they’re dealing with maggots and flesh. They have largely ignored aquatic insects, unless they are on floating carcasses. I’m curious about aquatic insects and crustaceans that might use defleshed bones for a substrate for laying eggs. Also some species of ostracodes lay eggs and molt in a particular season. . . hide inside a skull maybe? . . . Art Bettis here has a student doing a preliminary survey of microfossils–we’ll decide what we want to examine closer based on his report.

By: Pete Eyheralde

Pete Eyheralde — Tue, 12 Aug 2008 14:24:26 +0000

Falling through ice sounds good. Mama trying to help struggling young one – baby goes in with her. Or possibly mom goes through and kids follow her in blindly – could open up some interesting ideas in the sloth behavior department.

Has there been any pollen analysis or other clues from the sediment samples that might point to the time of year they died?

By: Dave

Dave — Mon, 11 Aug 2008 17:32:30 +0000

Hi Pete,
No geothermal activity like that in Iowa that I’ve ever heard of. Meghann is still working on the bone distribution map. Haynes says he has seen wolves take down a juvenile with an adult moose and bison. Our problem is explaining why TWO juveniles, a year or more apart in age, were hanging around. (Could the wound in the back of the toddler have slowed its development?) A natural catastrophe usually leaves the bones of other animals–we don’t have anything but sloths. I’m rethinking drowning too, but a flood is out–it would have carried in and dropped gravel and rocks equal to the density of the sloths. The clay the bones are buried in indicates little or no water velocity. How do you like the idea of falling through ice and drowning in a lake or the backwaters of a river in the winter?

By: Pete Eyheralde

Pete Eyheralde — Sat, 09 Aug 2008 21:03:35 +0000

Are there any maps from the Tarkio Valley site of the bone arrangement that might show a pattern of disarticulation?

3 sloths going down at once still sounds like a lot of predators to me. My vote is for drowning in a flooded creek or some other natural catastrophe.

Just watched something on National Geographic that showed how seemingly healthy bison in Yellowstone were being taken out in small groups by toxic gasses released from thermal vents. Nothing like that in Pleistocene Iowa was there?