Home: Scrying: For the love of species VII: A Fossil Photo Essay
When it comes to understanding the histories of speciation, ecology, and evolution, fossils are of the utmost importance. But not only do they show how life has changed over the centuries, they have an innate coolness: it is simply fascinating to touch a mineralized impression of a creature that lived thousands, millions, or even billions of years ago.
I was just a child when I found my first fossil. I was walking with my mom and my grandfather, along a beach on the northwest coast. My grandfather had degrees in both geology and paleontology, and so was telling us all about the nearby sandstone cliffs. I was interested, but only to a point… my little head was full of rocks by that point, so to speak.
I ran ahead to explore, and eventually found a lump of stone, sticking out of the cliffs. When he’d caught up with me, I asked Grandpa if I could use his rock hammer to check out this lump. He sort of shrugged, and a few moments later, I cracked open a fossil of the most beautiful clamshell I’d ever seen. I would have been proud to have found such a shell while combing the beach, and here, it was a fossil!
There were a number of other shells scattered in the piece I broke off, so I wanted to keep it as a whole. Mom said that was fine—as long as I carried it. She didn’t think I would, since the rock was nearly a quarter of my weight, but I managed. The fossil remains in my garden today, pictured above.
Since I was pretty much an amateur at the time, I never found out how old my shell was, or even the exact location I found it in. Even today, fossils fascinate me. Now I take more care to know how old they are and where they have come from. (Roll your mouse over any of the following pictures for age and origin. If you need a geological timescale for reference, please click here.)
Fossils provide important information, if we ever wish to know what may have once lived—and died—on our planet. By looking at the remains of the past, we might better understand how life and extinction today. (Those who fail history are doomed to repeat it, as my mother, the history/anthropology teacher likes to say.)
As pretty as I thought my shell was, the fossil record can be a chilling record of mass extinction. At least five major extinctions have occurred in the past 500 million years, leading to greater biological diversity in each case. Here in Colorado, there are several places where such a vivid record can be seen clearly in layers of sedimentary rock.
On South Table Mountain near Golden, a ridge marks the K-T boundary, the most recent extinction. Below the line, reptile fossils and dinosaur footprints have been found—above it, only mammals. If this extinction had not occurred, the explosion of placental mammal variation would have been squashed (or snacked) by giant reptiles.
Smaller things went extinct at the end of the Jurassic, along with the dinosaurs. Ammonites, like this one disappeared as well.
In comparison to the Permian extinction, the death of the dinosaurs was minor. About 250 million years ago, approximately 96% of the world’s species died. Many new habitats were then available, and the surviving 4% eventually found ways to fill them. Extinctions, as horrid and drastic as they may seem, can lead to a beautiful diversity. For instance, the Permian extinction led to the later success of flowers.
Trilobites and horn corals were quite prolific before the end-Permian extinction. Now they exist only in fossils such as these.
Meanwhile, Crinoids, like the one pictured on the left, lived alongside the trilobites, but are still around today.
Fossils and extinctions are even making the news today. Scientific American had a few articles on the subject this week. First, a rodent that was nearly someones snack in Laos turns out to be a species only seen before in fossils over 11 million years old:
Paleontologist Mary Dawson of the Carnegie Museum of Natural History and her team immediately recognized the strange rodent as a living member of a family thought to have been extinct for at least 11 million years: the Diatomyidae. Fossilized remnants of this group have been found throughout Asia with a distinctive jaw structure and molars. A new specimen of Diatomys discovered in June of last year in China bore an uncanny resemblance to Laonastes, including the same body size and tail span.
Full story is here.
On the extinction front, scientists have been recalculating which mammals may be at risk for extinction, factoring in things like urban sprawl and shrinking habitats (something familiar to Colorado natives.)
Biologist Marcel Cardillo of Imperial College London and his colleagues first estimated the overall risk of extinction a given mammal faced based on factors that led to the loss of other species in the past: a limited and specific geographic range, large size and relatively long periods of time needed to mature and reproduce. They then compared these factors to the animal’s current risk of extinction as measured by the World Conservation Union and came up with a “latent extinction risk.” The resulting list reveals mammals that are not threatened presently but could very quickly become threatened due to their biological extinction risk factors. In short, they could jump to the head of the line relatively rapidly.
Perhaps even the mass extinction occurring now will lead to greater diversity later on. Of course, if we humans and our parasites are the only survivors, we’d better figure out how to at least match Mother Nature in the aesthetics department, if we’re going to be responsible for future diversity. (Somehow, no matter what TV tells me, the SUV just doesn’t do it the same way a gazelle does.)
Since this post took me so long to compile, here is an extra note on the formation of fossils, plus a few more pictures:
Usually, a fossil is a bone, or shell, or tooth (like this shark tooth); materials high in calcium, which become preserved in sand or mud, eventually hardening to stone. Fossils of softer bodies are sometimes left as the impression of an organism’s remains mineralize while the sedimentary rock forms around it.