A heads up for National Fossil Day!

As I'm sure you are all aware, October 13, 2010 marks America's first National Fossil Day! You can learn all about it at the National Parks website. This is a day to celebrate our prehistoric heritage. I'll have a more complete post about this closer to the big day.

In honor of this upcoming holiday, I will write today about one of my favorite fossils. Yes folks, it is the Ohio state fossil Isotelus. First, what isn't there to love about a large trilobite? Second, the history of Isotelus in Ohio goes back a long way.

Isotelus specimens from Ohio were first described by John Locke in the late 1830s under the guise of the first Geological Survey of Ohio. Much of southwestern Ohio is underlain by Late Ordovician rocks. These rocks were deposited as part of a shallow epicontinental sea. They are full of fossils of brachiopods, bryozoans, bivalves, gastropods, trilobites, and many other critters. These rocks are now exposed in streambeds and roadcuts around Cincinnati and the surrounding area.

Huffman Dam Isotelus

Two elementary school groups had been to the Dayton Museum of Natural History (now the Boonschoft Museum of Discovery) and seen a cast of one of the largest whole trilobites found in Ohio - the Huffman Dam specimen. The children wrote letters to their representatives and the issue received widespread publicity. On June 20, 1985, Isotelus became the state fossil of Ohio.

*Much of this information comes from the Ohio DNR's  GeoFacts #6, available here.

The problem with caves

Caves pose specific problems to many forms of life. Caves are dark, and animals must develop their non-optic senses to survive. Many cave organisms have no pigment - what's the point of a pretty color pattern if no one can see it? On the right is a photo of a blind cave fish from the National Park Service's Ozark Riverways page. As you can see, it has no pigment and no eyes. Over time this group of fish has evolved inside caves and lost many of the features that would be beneficial in a normal stream habitat.

Now, you may be wondering why I'm talking about living things. I just felt it was a nice lead-in to my cave discussion. Here's my cave discussion: Caves are really hard to georeference. The Best Practices for Georeferencing tell us to georeference the mouth of a cave for a specimen that was collected within the cave system. But what do you do when a cave system has multiple entrances? Take Mammoth Cave in Kentucky for instance. There are presently over 30 entrances (not all natural) known for this cave system. If we had a fossil collected from within Mammoth Cave, we may be able to pick an appropriate entrance based on locality data.

Historical entrance to Mammoth Cave (photo)

If the specimen was collected prior to 1921, then the most logical choice would be the "Historical Entrance." This was the only entrance known until 1921.

The cave was initially one among many caves in the area. If locality data named one of the other caves which has since been connected to the Mammoth Cave system, it would be logical to georeference an entrance to that portion of the cave system.
As for determining the extent of error on that point, the Best Practices suggest using the surface extent of the cave. For Mammoth Cave, there are over 365 miles of the system that have been explored. Could historical data be helpful here as well? If the specimen was collected early in the cave's explored history, could a map of the cave system at that time be used to determine a lesser extent of error?
Mammoth Cave provides an extreme example of potential problems one encounters when trying to georeference cave specimens. And, until GPS units can get signals underground, these problems will continue to pester us. The Best Practices guide provides a method to consistently georeference caves even when they are very extensive.

Paleoentomology

Paleoentomology is a subject about which I know very little. That disclaimer aside, I am now going to talk about it, but not in any in depth manner. This subject comes up because yesterday I was pulling some type specimens. During this process I probably looked through a few hundred Permian fossil insects. Today I share with you one of these specimens: Dunbaria fasciipennis. This specimen is especially relevant to me and the Peabody collection for two reasons. First, it is from the Early Permian Elmo Limestone of Kansas (this is the formation I was looking through yesterday to find the type specimens). Second, it is named for one of our famous curators here in IP, Carl Dunbar.

For those of you who are curious, Dunbaria is a genus belonging to the Permian Palaeodictyoptera. This particular species has a wingspan of 3-4 cm. The pictured specimen above is the part of YPM 1002. Here is the counterpart of the same individual: