An excellent specimen of Trepospira sphaerulata was recovered in late December of 2021. It is a much better example of this species of Paleozoic gastropod, so I am replacing the content of this article with photos of it. This should help future researchers looking for an excellent example of this species. The specimen below, CG-0284 is from the Pine Creek limestone in Central Armstrong County, Pennsylvania.

CG-0284, Trepospira sphaerulata. Whitened with ammonium chloride to enhance contrast.
CG-0284, Trepospira sphaerulata. Whitened with ammonium chloride to enhance contrast.
Trepospira sphaerulata, Apertural view
Apertural view of CG-0284, Trepospira sphaerulata
Dorsal view of CG-0284, Trepospira sphaerulata
Dorsal view of CG-0284, Trepospira sphaerulata. Note the raised nodes.
Dorsal view magnified of CG-0284, Trepospira sphaerulata
Off-center dorsal view of CG-0284, Trepospira sphaerulata
Off-center dorsal view of CG-0284, Trepospira sphaerulata

Original Post from July 13, 2020.

Note: While the identification below is highly probable, it’s not definite. The specimen above (CG-0284) is a definite identification, verified by two other invertebrate paleontologists.

This gastropod has a highly probable Identification. I have confirmation that Trepospira sphaerulata is found in this and nearby limestone layers. Based on the nodes visible on the top of the last whorl, a local fossil gastropod expert gives this as a likely identification. This specimen comes from the Pine Creek Limestone locality which has been the source material for many of my recent posts.

The only fact keeping me from being sure is the lack of suture ornamentation. These should display as regular, raised nodes. However, the fact that this is a very flat, wide shell helps. The spire is visible as small and only raised in the very center.

Focus stacked photo of Trepospira sphaerulata. This may actually be a smashed Strobeus.
Focus stacked photo of what might be Trepospira sphaerulata. This may actually be a smashed Strobeus.

Example showing ornamentation from the late 1800’s

The example below was regarded as a perfect specimen. The suture ornamentation is very apparent.

Trepospira sphaerulata from Geological and Natural History Survey of Minnesota, Volume III, Part II, Page 1081.

Additional Photos of CG-0090

Specimen (right) with several others that may be of the same genus.

References for Trepospira sphaerulata