Tuesday, December 18, 2007

So thaaaaaat's what that is...

Many of you have visited this blog, looked long and hard at pictures of red fossils in red dirt and been understandably confused. Which past is the fossil, and which part is the mud?

Believe me, it can be just as hard to tell when you're eyeball to eyeball with it.

We've tried to combat this problem by using arrows, text on the image and sometimes ridiculously detailed (but hopefully vivid) descriptions. Dr. Bakker's just sent an image that helps make the leap from just-a-rock to living creature:

(c) Robert T. Bakker.

Here, Dr. Bakker has drawn the left foot of a Dimetrodon. All the various parts are labeled. Note the bone represented as almost entirely white (second digit from the left). The next two images show a fossil of this specific bone.

This Dimetrodon toe bone was discovered in the plaster jacket the team brought back from the site. The jacket is being excavated at The Woodlands Xploration Station.

Another image of the Dimetrodon toe bone, which gives it's specific size. From this, you can imagine how large the entire foot would be, as well as the full animal.

They've also uncovered what looks like another full fin spine. Since they are digging from the bottom of the layer towards what was the surface, it's a very nice surprise to find so many associated fossils.

You can see the spine running along the bottom of this image, parallel to the measuring tape. To the right of the image, the spine looks as though it continues under the dirt. Continued excavation with help determine how much of this spine has been preserved.

Technorati tags: museum, fossil, paleontology

Wednesday, December 12, 2007

This just in...

Or rather, out. And in to the world for the first time in 250 million years.

As we've previously shared, one of the plaster jackets holding fossils excavated from the Museum's site in Seymour is currently being housed at The Woodlands Xploration Station, an educational satellite of HMNS.

Dr. Bakker, David, Chris and Heather, a new volunteer at the Xploration Station, have all been working to excavate inside the jacket and figure out just what they brought back.

New Xploration Station Volunteer Heather Conklin works on excavating one of the plaster jackets brought back from Seymour. For the Conklins, science is a family affair.

Due to the jacketing process, they're actually digging from the bottom back up to the original surface of hte layer. The bones that they found closer to the surface in Seymour are actually at the bottom of this jacket. So no one knew if the dirt underneath (what they are digging now) would have a bunch of bones, or...nothing at all.

Just because they're not in the field doesn't mean they're any less meticulous about how and where each bone is discovered. According to Chris:

"We’ve slowly been removing matrix (dirt) exposing the bones and mapping their position; this includes taking pictures, and mapping them by finding compass direction and dip angle. Then we remove and package them for protection. A lot of the bones have been badly chewed and worn, suggesting that the level we are working on could possibly hold the remains of a Permian dinner. Two teeth have been found at this level, which supports that theory. After all the bones of the top level of the jacket were removed, there has been a lull in bone discovery in the next 10 to 20 millimeters. We have yet to reach a secondary bone level."

This claw may be from a Dimetrodon.

This Dimetrodon neural spine has been covered with a coat of vinac to protect it.

A small, unidentified vertebra.

This tiny, serrated tooth might be from a Dimetrodon.

They've also made some cool discoveries by going through what they bagged from the surface and excavations.

For example, someone might have a hunch a piece of rock is really something more - but you can't really figure it out in the field. So, they stick it in a bag, protect it with some foil if necessary, mark the bag with the name of the locality and move on. Also, when you're excavating a layer, you sometimes have to remove fossils in order to keep digging.

Now that the team has had some time to get all those pieces back out and look through them again, they've made a cool discovery.

The picture above shows two pieces of an Eryops bone. The larger half, in the foreground, was picked up in Seymour and then prepped out in Houston by David (a process by which he removed all the caliche and other material covering the fossil). He was showing it to Dr. Bakker, who happened to be looking through a bag of bone pieces from the same locality. While sorting through the bag, they found what looks to be the other half! (Shown in the background of the photo).

They left the other half un-prepped to illustrate the difference between fossils as they are found (the background) and as they look once prepared for display (foreground). You can see the difference in the level of detail that is evident in the prepped half.

The root of a Dimetrodon fang, as seen from the top.

The entire Dimetrodon fang that was found.

***If you're new to the blog, be sure to check out all the links at right. You can follow daily reports from the last dig, in early November, and learn all about the various species the team is finding fossils of. Lots of Dr. Bakker's illustrations and photos are posted, as well.

Wednesday, December 5, 2007

Neal Immega - A Permian Pool Table?

Did I discover a Permian pool table near the Dimetrodon dig site?

Let's do some investigation and see what answers can be found. Hundreds of two-inch spheres are concentrated in an area with a radius of about 100 feet.

Sandstone spheres all over the ground. A GPS device is present for scale.

A closeup view of several of the spheres.

When you look closely at just one of the spheres, you see that they are made up of sandstone and a few of them show inclined bedding planes (or layers), of the type that are found in rivers.

Geologists have characterized sandstone deposition in many environments. Beaches produce cross-bedding with an angle of about 5 degrees. Dunes are very different, because the grains are wind-blown and thus have cross-bedding of about 30 degrees.

Ripples in rivers have cross-bedding that are between these two extremes, which is why I predict that these sands (in the spheres seen above) are from a river deposit. This prediction is consistent with the oxidized red sands and shales that typically form in a desert environment.

What is inside of them? I could break some open, but I do not need to. A naturally broken and weathered surface (as seen in the close-up above) frequently shows more detail than a fresh break.

This is a photograph of one of the broken spheres showing rings of an iron mineral called goethite (hydrated iron oxide). We have enough information to make an interpretation.

Recall my previous entry on the spotted sandstone. In that case a bit of rotting organic matter reduced the iron in the rock to form a green spot.

The rock spheres at this site are caused by a bit of organic material that changes the chemistry of the water in the sandstone, causing precipitation of iron minerals. The banding is called Liesegang and you can read all about them by putting in “liesegang rings” into Google.