Bellacartwrightia: A Singular Specimen

Bellacartwrightia enlarged
Bellacartwrightia whiteleyi trilobite uncovered by Alasdair Gilfillin at Penn Dixie in 2016.

Every so often, one of our visitors uncovers a truly spectacular fossil. The preservation might be perfect, the assemblage of different fossils might be unique, or the type of fossil might be very uncommon. In this case, we present a beautifully preserved and uncommon trilobite called Bellacartwrightia whiteleyi.

Bellacartwrightia side view
Sideview of Bellacartwrightia. Trilobite is approximately 1.5 inches long.

Penn Dixie member Alasdair Gilfillan discovered this trilobite at our park on October 3, 2016. Our dig season was coming to a close and Alasdair decided to spend a weekend visiting us from New Jersey. Alasdair dug into the infamous Smoke Creek trilobite bed of the Windom Shale and unearthed what he thought was a Greenops — an uncommon trilobite that seems to represent one or two of every 100 or so trilobites that are found. Instead, Alasdair found something much rarer. He writes:

You may remember that I found a nice (though at the time partially covered) trilobite which I thought was a Greenops that day. I managed to get it prepped and it turns out that it was a Bellacartwrightia, a much rarer form. The prep guy did a really nice job and it turned out to be a really fantastic specimen. Please find enclosed the photographs. The trilobite is ~ 1.5 inches long.

Alasdair adds that the prep work was done by Bob Miles — a former Penn Dixie board member who also took the photographs. We thank Alasdair for sharing his images and for his donation of many fossil specimens that were used in our school programs.

Bellcartwrightia front view
The Bellacartwrightia cephalon (head) resembles that of Greenops, but the two genera are not closely related.

Bellacartwrightia whiteleyi is uniquely found in the Devonian rocks of the Hamilton Group in New York State. This fossil was first described by Lieberman and Kloc in 1997; the original paper can be downloaded here. Bellacartwrightia was named after the wife of paleontologist Bruce Lieberman, who at the time was a postdoctoral fellow at the American Museum of Natural History. Dr. Lieberman is now at the University of Kansas. The paper explains how Bellacartwrightia is different from Greenops, another trilobite with a somewhat similar appearance. From page 29:

In addition, the members of this genus are phylogenetically distant from species assigned to true Greenops…These two Middle Devonian genera have not shared acommon ancestor since, at latest, the Siegenian [approx 411 million years ago], based on an analysis of ghost lineages. To treat these species as members of a genus Greenops would necessitate placing all of the asteropyginines within the genus Greenops.

There you have it — a new genus of trilobites first documented in 1997 and one of our members finds an excellent specimen 20 years after the discovery!

Bellacartwrightia
Bellacartwrightia in the host rock — Windom Shale.

Alasdair was kind enough to share additional photos of the Bellacartwrightia as well as some of his other treasures from Penn Dixie. Our visitors are welcome to keep any fossils that they find, but we do appreciate photos of particularly cool fossils for use on our website.

Phacops rana double plate
A plate of Phacops rana trilobites found in 2015.
Phacops rana single plate
A single Phacops from 2016.
Phacops rana enlarged
Phacops trilobite. Prep work by Bob Miles.

For further reading, here are some links:

Evolutionary and biogeographic patterns in the Asteropyginae (Trilobita, Devonian) Delo, 1935 on AMNH

Bellacartwrightia whiteleyi on AMNH

Textbook Bellacartwrightia on Trilobites.com

Bellacartwrightia on fossilmuseum.net

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