Although it wasn’t billed specifically as a “show and tell” day when Metro and its paleontology contractor, Cogstone, invited local media to view a small but significant portion of the collection of ice age fossils that have been found in excavations for the Purple Line Subway extension, the occasion radiated the same kind of giddy excitement found at that kind of grade school tradition – if not more.
And as TV cameras, photographers and reporters jammed a small basement classroom at the La Brea Tar Pits museum yesterday morning, it definitely looked like everyone was having great fun – most of all the Cogstone paleontologists, who beamed at the chance to show off their fascinating finds. “I love talking about fossils,” said Ashley Leger, Cogstone’s Paleontological Field Director for the Metro digs. “Any time I get to talk about fossils all day, it’s a good day!”
According to Eric Scott, Cogstone’s Program Manager and Principal Paleontologist for the Purple Line Section 1 and Section 2 digs, there have been “several hundred” fossils found in more than 500 locations in the excavations so far, and that’s not including microfossils (those so small they have to be studied with microscopes) or shells, of which they’ve found “zillions.” Scott said some of the fossils are important individually, and others are more important collectively for the stories they tell. That is definitely true of the large collection of sloth bones found in the La Cienega station excavation…
…and of several instances in which they’ve found separate bones from the same animal in different nearby locations. “And that’s unusual,” said Scott, noting that the La Brea site has yielded bigger, but fewer, bones, and no multiples from the same animal. This may be, he said, because bigger animals were more likely to be pulled apart by predators and their pieces dragged off to separate locations. Smaller animals, like those at the La Cienega site, were more likely to be devoured in one place, with their bones remaining together after lunch was over.
Scott says his favorite fossil finds are those “put you back in the story.” For example, he showed off a horse bone that’s very weathered on one side, indicating it sat on the surface of the ground for a long, long time before it was buried, clearly warmed and worn by the summer sun.
There’s also a baby camel bone that shows evidence of tooth punctures, likely from a carnivore that munched on it after the camel died.
And these ground slot bones contain deposits of hard mud sediments, along with flecks of dark charcoal, indicating that – much like in our current cycles – there was once a big fire, followed by large rains and mud flows, which carried the bones away.
But, also in terms of favorites, Scott said, “It’s hard to get over the (very intact) lower jaw of the sloth.”
So far, even though the Tar Pits are closest to the Fairfax station area, the La Cienega station dig has yielded more bones – by far – than either the Fairfax or La Brea sites. Scott says the reason may go back to the ages-old wetter terrain at La Cienega (which was actually named after the wet, swampy conditions there). He says it’s likely there was a very healthy and diverse eco-system at the location, with plenty of fresh water, a wide variety of plant life, lots of herbivores to eat the plants and, also, carnivores (such as dire wolves and saber tooth cats) to eat the herbivores. (Scott noted with tongue firmly in cheek that La Cienega’s reputation as a great place for dining lives on today, with its famous Restaurant Row just up the street.) Scott says it’s very exciting to have found all of these types of fossils in the La Cienega excavations, because they provide evidence of the “whole ecosystem” that thrived there, not just bits and pieces, which is more common at many dig sites.
Cassidy Sharp, a Cogstone paleontologist who works as a field monitor at the La Cienega site and also does lab work, said her most thrilling find came when she was called to examine a pile of bones that had been scooped out and set aside at the location, and – “Oh, my goodness, this is exciting!” – saw a mastodon bone sticking out of the pile.
But it was Ledger who may have most proudly showed off several big finds, including her favorite, the skull of a Columbian mammoth found at the La Brea excavation. She said she feels a particularly personal connection to this one – named “Hayden” by the Cogstone monitor at the site – because it’s the same animal that was the subject of her Ph.D. thesis.
Leger explained that the fossil’s gender-neutral name was chosen by the Cogstone monitor at the La Brea site because they couldn’t tell whether it was from a male or female mammoth. Meanwhile, the pelvis bone of a Harlan’s Ground Sloth, sitting nearby and from the La Cienega excavation, evokes the perfect pop culture reference: “Her name is Shakira, ‘cuz her hips don’t lie!”
Scott and Dave Sotero, Metro Communication Manager, said Cogstone’s paleontologists will remain on duty at the Purple Line sites through the completion of construction in 2023. Until then, they are responsible for “mitigation services” at the sites – helping fulfill California CEQA guidelines that require site monitoring at all times during digging operations. If and when fossils are found during digging, work stops until the fossils can be safely removed, encased in a plaster “jacket,” and transported.
According to Scott, all of the fossils found will eventually end up at the Natural History Museum. Earlier, there was an agreement that all the fossils found in soil would go to the NHM, while those in found in tar would go to the Tar Pits Museum (which is actually a branch of the NHM), but Scott said there has so far only been one significant fossil found in tar – a camel toe bone found at the Fairfax excavation…”and it’s beautiful!”
Here are a few more images from yesterday’s event.