23 December 2015

23. Tanque Loma

Reconstruction & Skeleton of Eremotherium at the Museo Paleontologico Megaterio
University of California Museum of Paleontology
Location: Santa Elena, Ecuador
Age: Pleistocene (24,000-17,000 years ago)

While the North American megafauna consisted of animals such as mammoths and mastodons, horses and tapirs, bears and dogs, and bison and camels - all of which would have been, to varying degrees, familiar in Pleistocene Asia, Europe, or Africa - the megafauna of South America had very different roots.  Until late in the Cenozoic, it had been the most isolated of island continents, populated by birds and mammals that had evolved there and that had no close relatives anywhere else in the world (as well as, bizarrely, monkeys and rodents that apparently rafted to the continent on storm-tossed vegetation).  However, as temperatures cooled and sea levels dropped (and, even more importantly, as the volcanic Isthmus of Panama began to form late in the Miocene), a land bridge formed that would connect the Americas.  Over millions of years and in several waves, animals migrated across Central America in both directions.  The effect this had on North America is attested to by the success of now-extinct ground sloths, glyptodonts, and "terror birds," as well as by the continued prosperity of armadillos, opossums, and porcupines, all taxa with origins south of Panama.  Several South American sites document the effect that the so-called American biotic interchange on native ecosystems.  One of the most-recently described is a site that has drawn comparisons to Rancho La Brea: the asphalt beds of Tanque Loma in coastal Ecuador.  This site contains remains of North American migrants: mastodonts, horses, and deer.  Contrary to the traditional narrative that northern invaders outcompeted their austral counterparts, Tanque Loma also preserves a rich array of South American taxa, notably giant ground sloths, the most iconic of the native megafauna.  Among these, the huge Eremotherium is particularly abundant, leading to the suggestion that it may have been a gregarious animal that congregated in the area.  Unlike Rancho La Brea, though, they were not trapped there, or at least not by asphalt.  Unusually, the asphalt at Tanque Loma seems to have infiltrated the local sediments well after the fossils were deposited, helping to preserve the bone bed, but not to form it.

Visit: I'm not certain what the preservation status of this site is, but I'm fairly certain it is not open for visitation.
Fossils: The Museo Paleontologico Megaterio on the campus of the Universidad Estatal Península de Santa Elena was constructed specifically to house specimens from Tanque Loma.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: No, probably in large part because of how recently described the site is, but if you want more information on it you can check out Emily Lindsey's descriptive paper.

This post is part of my 2015 Paleontology Advent Calendar, a series of vignettes on lagerstätten - sites of exceptional fossil preservation - that document changes in climate and environments through the Cenozoic.  You can see the other posts here.

No comments: