Bellacartwrightia: A Singular Specimen

Bellacartwrightia enlarged
Bellacartwrightia sp. 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.

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 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

Some uncommon Penn Dixie fossils

With thousands of visitors to Penn Dixie each year, really cool fossils are uncovered fairly often. With a trained eye and determined spirit, our visitors never cease to amaze the staff and volunteers with what they discover.

Dr. Edgar Kooijman, Director of the Biotechnology Program at Kent State University sent us these photos and descriptions of some uncommon fossils from a trip to the site a couple of years ago. His specimens — a trilobite, a snail, a crinoid, and an amminoid — showcase the diversity of marine life that existed in our region during the Late Devonian Period.

Bellacartwrightia.JPG
The head of a Bellacartwrightia trilobite.

From Dr. Kooijman:

This rolled trilobite was identified as a Bellacartwrightia calliteles and was found during the field trip of the North Coast Fossil Club in May 2013. It came from the main trilobite layer [in the Windom Shale], and was prepped by Brian Dasno from Watertown NY. This was no small task as the specimen was essentially split in two. The eyes and some of the carapace were on one side, and the rest on another. While the specimen was crushed during or after fossilization it is complete and all the spines are visible. The “spikes” coming from the front of the head are the tail spines. The dorsal spines are also beautifully visible.

The following three specimens were all found during the May 2014 field trip of the North Coast Fossil Club, from Cleveland OH. They were prepped by Marc Behrendt.

Arthroacantha.JPG
An Arthroacantha crinoid holdfast.

From Dr. Kooijman:

The crinoid cup is from a species that is commonly found in the Sylica shale of Ohio, but which is rare (at least complete cups are) in the Windom shale at Penn Dixie. The name of this species is Arthroacantha carpenteri (Hinde). The “nob” at the top is where the stem would have been attached. Stem fragments are common fossils in the shale of Penn Dixie. Also note the numerous scars of the side of the crinoid cup. These scars used to hold spines that may have served to ward of snails that loved to feed on crinoids. The spines are not preserved in this specimen but the attachment points are easily visible.

DSC_0004.JPG
A gastropod (snail) — potentially Bucculentium.

From Dr. Kooijman:

The snail is from the genus Platyceras, and the species may be Bucculentum. And was identified from among the different species found in the Sylica shale of north west Ohio. It was found just above the main trilobite layer at the edge of the digging pit during the 2014 season. It is the largest snail I have ever found at Penn Dixie.

Ammonoid.JPG
A cast of an ammonoid — predatory cephalopod

From Dr. Kooijman:

The ammonite was found in the main trilobite layer. Note that the original shell material is not preserved and only the cast of this mollusk is visible. No genus name for this specimen is known. These aminoids are occasionally found in the Windom shale.

Penn Dixie thanks Dr. Kooijman for sharing his wonderful photos with us!