martes, 31 de enero de 2017

Talara - Peru's Great Ice Age Tar Trap

A few years back, as I ran around the Royal Ontario Museum fossil halls trying to take in as much as I could in the short time I had there, an Ice Age fossil stopped me in my tracks. It was a fossil horse jaw, but unlike any I had seen before. The fossil seemed impossibly black, tooth and bone stained to gorgeous ebony shades.

The beautiful fossil had been excavated decades before from a tar seep in Talara, Peru. I had never heard of this place before. When I think “tar pit”, I think La Brea. (Perhaps because, aside from being the most important fossil site on the planet, La Brea translates directly to “the tar.”) But the exhibits and a quick primer from ROM curator Kevin Seymour introduced me to an entirely different death trap that has produced a wealth of fossils colored by a deeper shade than the La Brea brown of their Californian counterparts.

Much of what’s known about Talara comes from a collection of over 28,000 bones collected from the site from A.G. Edmund in 1958. The vast majority of these fossils – about 63.4 percent of identified bones – are from mammals, and of these more than 79 percent are the remains of carnivores. There are plenty of other creatures represented at Talara – songbirds, amphibians, horses, camels, ground sloths, mastodons, deer, and more – but this place was primarily a deadly draw for the meat-eaters.

Smilodon fossils from Talara at the Royal Ontario Museum. Credit: Brian Switek

Some of the Talara carnivores are still with us. The Sechuran desert fox, wrote Seymour in an overview of the site, is represented by pieces of over 100 individuals pulled from the asphalt and still lives in the area. And when I giddily started pulling open cabinets in the ROM collections on my second day at the museum, Seymour was kind enough to point out a stunning fossil jaguar skull that had previously been mistaken for an American lion. But the biggest of the Talara carnivores are long gone. The site has given up the bones of at least 51 dire wolves and 20 Smilodon.

Many of these animals were juveniles. And while the sample isn’t nearly as extensive as that of La Brea, Seymour notes, the proportion of juvenile animals for the three most common carnivores ranged from 57 to 69 percent. That seems quite high compared to La Brea and Ice Age fossil sites in Florida, and could indicate that either there were more juveniles around at the time the Talara tar seeps were active or that the young animals were more naive and blundered into the trap more often.

All these figures are just the beginning of a new effort to understand the site. After early descriptions and fossil sorting by Charles Churcher and others in the 1960s, the fossils waited in the Royal Ontario Museum collections for a more recent surge of interest that is beginning to trickle out some new details about this sticky Pleistocene bonanza.

And Talara is not the only undersung tar pit around. In another new paper Seymour and Emily Lindsey surveyed several other sites in the Americas ranging from McKittrick in California to La Carolina, Tanque Loma, and Corralito in Ecuador.

Each site its own character and history. Tanque Loma, for example, is superabundant in sloths and has plenty of prehistoric elephants but totally lacks the big carnivores found elsewhere. La Corralito, on the other hand, has a somewhat more even mix of carnivores, sloths, horses, elephants. This is probably because these two sites didn’t kill the animals by suffocation in tar but were places where bones were laid down by rivers and then tar seeped up into them afterwards. There wasn’t the same deadly aroma of rotting flesh that pulled the wolves and sabercats to the tar in Talara and La Brea. For carnivores, those places were truly the pits.

References:

Lindsey, E., Lopez, E. 2014. Tanque Loma, a new late-Pleistocene megafaunal tar seep locality from southwest Ecuador. Journal of South American Earth Sciences. doi: 10.1016/j.jsames.2014.11.003

Lindsey, E., Seymour, K. 2015. “Tar Pits” of the Western Neotropics: Paleoecology, taphonomy, and mammalian biogeography. Natural History Museum of Los Angeles County Science Series, 42: 111-123

Seymour, K. 2015. Perusing Talara: Overview of the Late Pleistocene fossils from the tar seeps of Peru. Natural History Museum of Los Angeles County Science Series, 42: 97-109

[This post was originally published at National Geographic.]

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