Wyoming, today, contains some of the most important geological sites in the United States and perhaps the world, ranging from its mineral hot springs and geysers, to its geologic formations that capture the past. Over an hour away from civilization, in an area that is so arid that only sagebrush and grass can survive, the past is being uncovered. The land is giving way to wind and water erosion, revealing evidence of life that existed almost 200 million years ago.

    During the Jurassic Period, tropical climates extended well into North America and Europe. Higher sea levels created epicontinental seas, particularly in western North America. These seas were prime environments for Jurassic marine life, including ichthyosaurs. Ichthyosaurs flourished in a shallow epicontinental sea that covered much of Wyoming about 160 million years ago, during the Jurassic Period. Because epicontinental seas covered both North America and Europe, ichthyosaurs have been found on both continents. Whether they are the same species or not remains a mystery, although some paleontologists classify them together.
 
 The Sundance Formation consists of multiple layers of sandstone, shale, and limestone. Each layer marks a point in the past of Wyoming. The Red Water Shale, a member of the Sundance formation, contained the fossilized skeletons of Marcellus and Mitch.

    Marcellus, the first specimen to be excavated, had the posterior dorsal vertebrae exposed by run off erosion. Some exposed vertebrae were weathered and scattered on the surface extending down a gully. The covered portions of the vertebral column plunged into the ridge and were therefore unweathered. The specimen was encased in a layer of platy black shale, which was easily removable. This was done using shovels, smaller digging tools, whiskbrooms, and dustpans. Once uncovered the specimen consisted of forty vertebrae, fragmented gastralia and ribs, a jawbone, and one paddle bone. Under the specimen was an unusually high concentration of invertebrates called belemnites, a squid like animal, that may have been a source of food for the ichthyosaurs.

    Mitch, only a five-minute amble from Marcellus, also protruded from a ridge. Float from Mitch was scattered more widely, extending down the whole side of the ridge in every direction. Excavated in the same fashion as Marcellus, many vertebrae, ribs, neural arches, pelvis bones, and paddle bones were recovered. Belemnites were also associated with this specimen; however, there were fewer of them.

    In order to excavate the specimens, and obtain accurate information, techniques such as plaster jacketing, site mapping, and measuring stratigraphic sections were used. These techniques allow us to gather data on the context in which the specimen was found.
Before the specimens could be removed, a site map of the area was drawn. A grid of one or two foot squares was laid out using nails and string. A Brunton compass was used to measure the orientation of the grid. The grid enabled an accurate recording of the position of all parts of the specimens. From this map, it was possible to describe the manner and orientation in which the bones were preserved. From the site maps that were drawn of the two specimens, it is evident that scavengers fed on Mitch's body before it was buried by sediment. Mitch's fossilized skeleton was severely disarticulated. Portions of the vertebrae were laying face up while other sections were on their sides. Some of the ribs were in a criss crossed direction. The jumble of bone was encased in shale providing evidence that it had been disarticulated before deposition. Marcellus's fossilized remains were articulated and remained in a straight pattern of vertebrae and ribs.

    A portion of both specimens needed to be encased in plaster jackets. Plaster jacketing was used to keep the specimens as intact as possible. The jawbone of Marcellus had been kept intact for millions of years by the surrounding rock. However, attempting to remove the jawbone proved to be difficult as it was very delicate and began to shatter. Therefore, the jawbone was cleaned off, as much as possible, without damaging it. Once cleaned, a plastic hardener was applied to keep the bone and surrounding shale from falling apart. In order to ensure that the plaster would not stick to the bone, paper towels were soaked with water and then pressed onto the bone to form a protective layer. Then plaster bandages were moistened and wrapped around the whole surface of the bone pod. Next, a trench was dug around the bone pod, deep enough to leave a thick supporting layer of sediment below it. The pod was undercut and plastered again to create a lipped edge, allowing the pod to be flipped and plastered on the bottom to create a hard shell that would keep the specimen intact for the journey home.

    A stratigraphic section was measured at both excavation sites to determine which strata layer the specimens were coming from. Because each layer represents a period of time, it is important to know which layer the specimens came from. Using outcrops of bedrock, a tape measure, and a Brunton compass, we were able to determine the thickness and the strike and dip of the different layers. Marcellus and Mitch both came from the Redwater Shale, however, in two different layers that were separated by sandstone.

    Both specimens are now in the Earth Sciences building at SUNY Brockport where the fossilized skeletons will be cleaned and reassembled for further study. From this, we hope to learn more about the North American ichthyosaur that lived during the Jurassic, about 160 million years ago.  It is likely that the specimens belong to the genus Ophthalmosaurus.

"Author'sHumor"
 
 

The Western Jackalope

    A common occurrence in the mountains of Wyoming, the Western Jackalope is a solitary creature fearful of humans. Being one of the rarest species in the world many dispute their existance. However, legends tell stories of jackolopes having the ability to imitate the human voice. They repeat the songs and stories of cowboys guiding their herds, like phantom echos coming from nearby hillsides. And some believe that the milk of a jackolope can treat many ailments. Jackolopes are shy and clever, choosing to remain mysterous in the minds of humans.