Sloth News

The UI Museum of Natural History received some well-deserved recognition in the May 11, 2009 issue of the Cedar Rapids Gazette. In their Homers/Gomers column, under what’s going right, The Gazette called the Museum a “NATURAL TREASURE.”

“The University of Iowa’s Museum of Natural History may be one of the state’s best-kept secrets. The museum marked its 150^th year last week, and its mission as a teaching and research tool is still intact. The 1,000,000-item collection compiled by UI faculty and students during research expeditions, includes a signature giant ground sloth display from a major excavation near Shenandoah.”

Good Going Museum!   (For the record, Rusty and display were constructed  long before our Shenandoah discovery, but they are right about him/her being the same species.)  Sloth on.  Holmes.

Some nice press about the new sloth discovery in Futurity, a new blog about breakthroughs at America’s research universities.

This was the announcement the University released to the press this week.  We’re grateful to the NSF for their continuing support and to all the volunteers working on the project who make it possible.  Our sincere thanks.    Holmes and Dave

UI sloth excavation project awarded $20,000 NSF grant

The University of Iowa’s Tarkio Valley Sloth Project has been awarded a $20,000 grant from the National Science Foundation (NSF) to complete the excavation of the remains of three giant sloths and begin research of this unique discovery. The project is a joint effort of the UI Museum of Natural History, Department of Geoscience in the UI College of Liberal Arts and Sciences, and Office of the State Archaeologist, all teaming up with volunteers and students from across the Midwest.

A skeleton of a giant Ice Age sloth was discovered by Bob and Sonia Athen in 2001 behind their home near Shenandoah, Iowa, in the bed of the West Tarkio Creek. More bones were subsequently found on the property of the adjoining landowners, Dean and Loreta Tiemann, who, like the Athens, graciously agreed to allow the excavation and to donate the fossils to the University of Iowa.

The elephant-sized beast lived in Iowa for thousands of years before going extinct around 12,000 years ago. To date, more than 100 major elements have been recovered, making this individual the second-most-complete skeleton ever found of this rare species. In 2006, two juvenile sloths of the same species were discovered nearby.

According to project leader Holmes Semken, emeritus professor in the UI Department of Geoscience, only six semicomplete skeletons of this species have ever been found and this is the first time any juvenile, much less two, has been found directly associated with an adult. They also are buried in sediments that will provide valuable environmental data about the climate at the time.

“This could be our ‘Rosetta Stone’ for understanding the family life of these mysterious creatures,” Semken said. Over 40 bones of the older juvenile have been recovered, making it also the second most-complete juvenile of its kind ever found.

“The NSF is excited about the discovery and has indicated that we can count on their continuing support if we keep making progress like we have,” said Semken. “They see the potential here for a major contribution to our understanding of the Pleistocene extinction event in which almost 40 large mammals became extinct at the same time. They also realize they are getting a lot of bang for their buck through the tremendous support we’ve received from the university, the Page County community, the Iowa Archaeological Society, Mid-American Paleontological Society, the Boy Scouts, Iowa Academy of Science, and staff and students from educational institutions all across Iowa.”

The project has also received assistance from the U.S. Department of Agriculture, the U.S. Army Corps of Engineers, the U.S. Geological Survey and the National Park Service.

“It’s a breakthrough project for the university,” said sloth project co-leader David Brenzel of the UI Museum of Natural History. “The NSF recognized that our goal to educate people about the process of doing science is as important as the research itself. They are providing specific funding to expand our educational outreach efforts through public programs and the Web.”

Last month, a blog was started about the project at http://www.slothcentral.com, which can also be found by going to http://www.uiowa.edu/~nathist.

“The blog will allow anyone interested in the project to submit questions and contribute ideas. We hope it will be fun, educational, attract some professional interest, and also inspire young paleontologists,” Brenzel said. Photos of the dig and associated lab work are available at http://www.uiowa.edu/~nathist/Site/sloth/index.html.

For further information or to volunteer for the project contact Sarah Horgen at the UI Museum of Natural History, sarah-horgen@uiowa.edu, Semken at Holmes@slothcentral.com, or Brenzel at David@slothcentral.com.

STORY SOURCE: University of Iowa News Services, 300 Plaza Centre One, Suite 371, Iowa City, Iowa 52242-2500

MEDIA CONTACTS: Sarah Horgen, UI Museum of Natural History, sarah-horgen@uiowa.edu, 319-335-0606; George McCrory, University News Service, 319-384-0012, george-mccrory@uiowa.edu

Ground sloths were first discovered by science in 1789 when a giant skeleton was found on the banks of the Rio Luyan near Buenos Aires. Their existence didn’t surprise the local natives who had long held the animals were living underground like giant moles occasionally venturing too close to the surface and dying because of exposure to sunlight (Heuvelmans, 1995).

That’s the same legend Siberian natives evolved to explain the appearance of mammoth carcasses in the river banks after spring floods (Tolmachoff, 1929). I was reminded of that this week as I slopped through the muck inside a local museum looking for salvageable artifacts. Our first sloth was uncovered by the big 1993 flood, hopefully we don’t lose it to the Flood of 2008.

A 500-year flood fifteen years after a 100-year flood–either that’s really bad luck or we’re doing something wrong. The underground has always been a place of dark mysteries and strange animals, but there’s no mystery in what happens when you tile, pave over or compact 56,276 square miles of land (Iowa’s area) to drain the water as quickly as possible into the nearest river. The agony for the thousands of displaced people is clear, but the soil that’s currently making its way downstream to the Gulf won’t be as easily replaced as their ruined possessions.

George Washington Carver offered one of the most hopeful predictions for Iowa ever conceived, “ I believe the Creator has put ores and oil on this earth to give us a breathing spell. As we exhaust them, we must be prepared to fall back on the farms, which are God’s true storehouse and can never be exhausted. For we can learn to synthesize materials for every human need from the things that grow” (Blouin, 2005). When things calm down a bit and people feel a little more secure, maybe we can take a hard look at the way we manage our soil and water. That’s Iowa’s fortune washing away. Our future is a lot darker as a result–there’s no mystery about that. . . . Dave

References

Blouin, MT. 2005. Iowa builds on agricultural strengths to advance a bioeconomy. Industrial Biotechnology 1:92.

Heuvelmans, B. 1995. On the Track of Unknown Animals. R. Garnett (transl.) Kegan Paul International.

Ides, EY. 1706 Three Years Travels from Moscow Overland to China. London.

Tolmachoff, I. 1929. The carcasses of the mammoth and rhinoceros found in the froze ground of Siberia. American Philosophical Society 23: I-74b.

I cited Swedish explorer Erland Nordenskiold in a post last week and forgot  to mention the role he played in one of the last great natural history adventures of the 19^th century. 

In 1895 a former merchant sea captain named Hermann Eberhardt, farming on the shores of a inlet called Ultima Esperanza (“Last Hope”) in southern Chile discovered a giant cave  on his property. Inside he found a large fresh-looking skin covered with long reddish-gray hair and embedded with bean-sized bones.  Scientists identified it as that of an extinct Mylodon ground sloth.  Further excavations uncovered bones with bits of dried tissue still attached, plus evidence  of human habitation.

Today we know the bones and skin were preserved by the climate inside the cave, but to Professor Florentino Ameghino of the Buenos Aires museum, the skin appeared fresh.  He remembered a story a friend had told him of seeing a strange animal while exploring in the area.  Ameghino linked the story and the skin to a legend of a large nocturnal beast local natives called iemisch, with giant claws it used to dig burrows where it slept during the day.  Ameghino concluded the iemisch  was a  living Mylodon ground sloth.  His announcement created a world-wide stir. (Ameghino, 1898)

Erland Nordenskiold was a voice of reason in the hullabaloo and conducted the first systematic excavation of the cave.  However, publication of his study only added fuel to the fire.  He determined the evidence of human habitation lay in a distinct horizon above and separate from the older lower horizon with its sloth bones, dung and dried grass.  (Nordenskiold, 1900). Modern radiocarbon dating of the dung indicates the cave was occupied by sloths from about 13,500 years B.P. to 10,500 B.P. (Markgraf, 1985). 

Others concluded from the large quantities of the dung and finely chopped “hay” that sloths had been kept captive inside the cave by natives fattening them for slaughter, behind the stone wall  Nordenskiold had reported.  Some even suggested the sloths had been domesticated (Allen, 1942). Today we know the sloth “corral” was merely fallen rock from the ceiling (Naish, 2005)

In 1900 the Daily Express sponsored an expedition to Patagonia to capture a living Mylodon. The venture was mismanaged however and the leader, HV Hesketh-Prichard, quit before reaching the cave.  He dismissed the idea as a hoax (Hesketh-Prichard, 1902).

Nordenskiold offers us a lesson on the sloth project–finding three sloths in close proximity doesn’t make them a family no matter how good it looks.   Only careful excavation, painstaking attention to stratigraphy  and detailed chemical analysis will do that. . . . Dave

References

Allen GM. 1942.  Extinct and Vanishing Mammals of the Western Hemisphere. Special Publication #11, American Committee for International Wild Life Protection.

Ameghino, F. 1898. An existing ground-sloth in Patagonia. Natural Science 13: 324-326.

Hesketh-Prichard, HV. 1902. Through the Heart of Patagonia.

Heuvelmans, B. 1995. On the Track of Unknown Animals.  R. Garnett (transl.) Kegan Paul International.

Markgraf,V. 1985.  Late Pleistocene faunal extinctions in southern Patagonia.  Science 228: 1110-1112.

Naish, D. 2005. Fossils explained 51: Sloths. Geology Today 21: 232-238.

Nordenskjold E. 1900.  La grotte de Glossotherium (Neomylodon) de Patagonia. Bulletin de la Societe Geologique de France: 29: 1216-1217.

Scientists recently finished analyzing a partial sloth skeleton found in the Cupisnique Desert of Peru in 1975 (Pujos et al., 2007). They estimate its age at 15-25,000 years old. The humerus (upper arm bone) matches one recovered by Swedish explorer, Erland Nordenskiold, in 1905 from a cave in the Andes called Casa del Diablo. They named the new species Diablotherium nordenskioldi and placed it in the Megalonychidae family, making it a close relative of our own Megalonyx. Nordenskiold suspected he had something special, and now it’s confirmed– Diablotherium was fully arboreal (tree-dwelling) and apparently as well-adapted to life off the ground as modern tree sloths. The discovery, the first species of this type ever found, underscores the tremendous adaptability of the ground sloths, especially the  Megalonychidae.

It would be hard to find anywhere in this hemisphere where a Megalonychidae of one kind or another didn’t live–from the tip of South America to the Arctic Circle, from the Atlantic Ocean to the Pacific. In addition to all the familiar terrestrial (ground-dwelling) species, like our M. jeffersonii, there were subarboreal forms and even aquatic species living like sea otters off the coast of Peru, grazing on sea weed (deMuzon and McDonald, 1995). How do animals as adaptable as that, thriving for millions of years, ever go extinct? Answering that question is one reason why we keep digging. . . . Dave

References

de Muizon, C and McDonald, HG. 1995. An aquatic sloth from the Pliocene of Peru. Nature 375: 224-227.

Pujos, F, De Juliis, G, Argot, C, Werdelin, L. 2007. Zoological Journal of the Linnean Society 149: 179-235.