Almost Complete Silurian Trimerus Trilobite

These pictures show an almost complete Trimerus delphinocephalus (Green, 1832) trilobite. It was fossilized intact but was found in two pieces. Some of the last thorax segments and the pygidium (tail) had broken off this specimen. It is still missing part of its feeding/digging scoop and small pieces of segments missing from the rear section of the trilobite. Visually it appears to be about 95% complete.

After some effort, I was able to find the broken off tail section of this trilobite. It was not too damaged and fit  right into place on the original piece found. Whew! I gave an early birthday present to myself. :)

Fossil was found in Clark County, Indiana in the Silurian age Waldron Shale. It has not been cleaned and two parts of it have glued back together. I hope once it has been abrasive cleaned extra matrix and glue will be removed.

Compare it to another Clark County Trimerus trilobite fossil found on the Internet at this web site: Week's trilobite web site.

New Albany Shale Fossil

Reading the Indiana Department Geology and Natural Resources Twenty-First Annual Report W.S. Blatchley State Geologist 1896, I came across a plate image and description of the Parenchymophycus asphalticum found in the New Albany Shale of Clark and Floyd Counties in Indiana, USA. The New Albany Shale was named by a local geologist in the 1800s named William Borden. The shale dates to the Late Devonian Period.

Below is an image of a New Albany Shale fossil that might be what is described in the 1896 Report.

On page 118, Parenchymophycus asphalticum is described as:

"Plant with band-like thallus 10 to 150 mm wide, the well preserved spongy parenchymatic cells always filled with asphaltum. The cell walls are rich in silica. Cross divisions (nodes) at regular distances divide the band into rectangular oblong pieces (internodes). The termination of the plant consists of an oval shaped bud similar to that of Fucus vesiculosus L. of the present age. The length of specimens found varied from a few centimeters to 183 cm. The cell walls of this most interesting sea plant have resisted so well the influence of decomposition that they served as a means of diffusion for fluid bitumen, which, after a long time, gave off the  volatile components and left only the hard aspaltum. All specimens show no ramification. (Pl. II, fig. 1)"

Pyrite of the Waldron Shale

 Pyrite crystals found in the Waldron Shale of Clark County Indiana. It is from the Silurian Period.