Friday, November 9, 2007

Day 5: The Beatles Strike Again

As more and more of the Amy Dimetrodon popped out of the ground today, the team spontaneously broke into a collective rendition of The Beatles' "Come Together" - accidentally following the proud tradition of channeling the Fab Four in celebration of a big find. It certainly won't have Lucy's groundbreaking, international impact - but it's still pretty cool to see something so recognizable just keep coming together.

This site was uncovered from just one clue - a tiny rib bone in the lower righthand corner. The site extends further to the right, and most of the lines of bones extend further into the hill horizontally. In addition, it looks like each horizontal fin spine is roughly the same distance apart - increasing the likelihood that this is all from a single Dimetrodon.

Since the original discovery of this site on Tuesday, the area producing bones has roughly quadrupled in size. Today at the Amy site, Chris, Kathleen and Kathy uncovered 2 new full Dimetrodon fin spines, each of which is continuing into the face of the hill; two new partial fin spines that look like they will be complete when fully excavated; another tooth from the mystery animal that we theorize to be Dimetrodon loomisi, the "cheetah of Dimetrodons"; a small vertebra; and this:

Multiple vertebra and a fin spine that Kathleen and Kathy unearthed today at the Amy site.

Because they keep finding teeth with roots - indicating that they were lost after death and not while eating - the team suspects they may have a jaw somewhere in the Amy hill. It's exciting, but you have to reign it in sometimes - as Kathleen said, "It's a learning experience. You have to be patient. You're desperate to clear off all the dirt, so you can see the whole bone, but the dirt is often what is holding the bone together."

This image shows the spine running across the top of the picture above, as it is being uncovered.

In one instance today, Chris found two lines of fin spine bones criss crossing each other, meaning the team won't be able to uncover the lower line of bones until they get it into the lab - which could be weeks, or even months away, depending on how soon they can return to work on the site. It can be maddening - but always exciting.

Further up the opposite hill, Shirley, Neal and Kim Beck dug into a possible site discovered by SHS students Jacob and Tarrington, who will be back on the dig tomorrow morning. Though the site was rich with Xenacanthus teeth on the surface, which the guys did a great job of finding - it turned out to prove the rule that you can't strike gold every time.

Neal, Shirley and Kim Beck dig into The Site That Wasn't. Towards the end of the day, Kim did locate some tiny Xenacanthus teeth, a tiny vertebra, a bunch of fish scales, a few little amphibian limb bones and skull fragments and shark cartilage.

Of course, Shirley insists that they did find something: "We found places where there aren't any fossils. That's valuable information. It's very useful for mapping the site as a whole."

David and Johnny also worked on "stabilizing the jacket," though it looked an awful lot like playing in the mud.

David mixes the plaster to soak the burlap and spread over the jacket. It's a delicate art - you have to get each of the ingredianets just right. Too much salt - and it dries before you can get it on. Too little, and you're stuck with a soggy jacket.

They're adding fresh burlap, which is coated in plaster, and reinforcing that with...more plaster. According to David, "this is going to be the tiger tank of the plaster-jacket world." They may also add wooden boards for extra support, and they're currently debating the best way to get this 350-pound behemoth out of the site - which is at the bottom of the hill.

Johnny and David work on wrapping the Spine site with plaster. In person, you can see all the textured burlap peeking through - it makes the jacket look kind of like a mummified block.

Tomorrow they'll undertake the massive task of flipping this monster over. They also headed into town for a visit with another of Kim Beck's science classes.

SHS junior Shelby Winter examines a possible Xenacanth coprolite.

SHS students Shelby Martin and Shelby Winter check out arthopod tracks found on local sandstone.

Tomorrow, they're expecting lots more of the Dimetrodon to pop out of the Aimee hillside. Check back tomorrow to see how this site continues to come together.

David Temple - Riddle me this: When is Nothing, Something?

A fossil is any trace of past prehistoric life - sometimes proof of the animal itself - such as a tooth, a toe or other bone. But there is another group of fossils that I have enjoyed collecting and working with at our site in Seymour that are much more subtle. They are not the fossilized remains of the animal itself - but rather the remains of something they made.

These arthropod tracks show the path of a tiny creature (probably something like a crayfish) crawling on the bottom of the ocean millions of years ago. The animal itself is long gone - but thanks to his footprints, we know he was here. Look at the way these tracks have a staircase pattern - what could have caused this?

These are called trace fossils. Examples we've found locally include footprints, trackways (a series of footprints), burrows and coprolites. Finding any of these can tell you where animals live on a site, even if you don't find their bones. These fossils are often trickier to spot - but once you've gotten the hang of it, you start to see them everywhere.

So, when is nothing actually something?

In the Permian, burrows were the holes that animals dug to live in. After death, these holes filled in, and due to their chemical makeup, became encrusted in colliche (a substance that normally covers fossils and is removed to expose them). At this point, the surrounding rock is now softer than the filled-in burrow. When the surface erodes - as it is doing at the Museum's site - all or part of this cast of the hole becomes exposed. What you see on the surface are hundreds or thousands of roughly cylindrical colliche fragments that show you the shape of these animals' burrows. We have found some that represent a hole large enough for a medium-sized dog to crawl in - and some that are small enough for an ant.

A student in Kim Beck's science class at Seymour High School looks at a possible burrow found at the Seymour site. David visited the classes yesterday to talk about local geology and fossils.

We are not always sure what animal made the burrow -so we take it back to the Museum, research what other paleontologists have found and compare it to figure out the answer.
Hitting a Home Run
Finding and looking at burrows can seem tedious - especially when all the other team members are excavating beautiful bones and teeth, and all you've picked up is a funny-shaped rock - but every now and then you'll find a burrow with bones in it. This is a home run - it means you are looking at an animal's house - and they are still at home. Because they died inside their burrow, and were thus protected from the elements, you've got a complete, articulated skeleton.

Previously, we've found 6 complete animals and a larger number of partial animals in burrows. They are the remains of the Lysorophus, a smallish amphibian that resembles a modern siren. In response to the drying climate of the Permian, these animals burrowed into the mud to stay moist and waited for the rains to return. They never did, and these burrows became their graves.

You be the judge.

Trace fossils are subtle and paleontologists will sometimes disagree as to exactly what they represent. Case in point - this fossil was found in a spoil pile from the 1917 excavation by the Sternbergs, who either missed it, or weren't interested in collecting it.

What in this picture piqued David's attention? His possible coprolite is the larger, tear-shaped object in the lower lefthand corner.

I suspect it is a world class shark coprolite or a very unusual burrow - my irascible colleague feels it is only an unusual rock. We've got a wager on it - if it turns out to be a coprolite, he's offered to eat it, and I've matched him by saying I will if it turns out to be nothing. We won't be able to settle this dispute in the field - we'll have to wait until we get back to Houston. Stay tuned to see what happens. We should know in about a week.

(David also explains the process of plaster jacketing - which the team is working on today - here. We'll have photos and videos of the process posted later today.)