The extinct cephalopod Metacoceras clinocostatum is a species commonly found in Brush Creek limestone. Compared to other examples of the genus Metacoceras, it is very small in size. I was apprehensive about identifying these. In the past, I believed they were the inner whorls of larger specimens. However, these are small cephalopods.

Metacoceras clinocostatum

Scientific Classification

Kingdom:

Animalia

Phylum:

Mollusca

Class:

Cephalopoda

Order:

Nautilida

Family:

Tainoceratidae

Genus:

Metacoceras

Species:

clinocostatum

1982 Sturgeon et al.

The common local cephalopod genus, Metacoceras, lists twenty-seven genera on Fossilworks, inside of the Paleobiology Database. But for whatever reason, M. clinocostatum is not listed as one of the genera in the database. It was clearly defined as a new species by Sturgeon et al. in a research article published in November of 1982, ahead of the publication of Pennsylvanian Cephalopods of Ohio. The new species was based on Metacoceras perelegans. The type locality is the Brush Creek Member (1979) in Ohio. There is no specific geographic location given. Its name comes from two Latin words, clino, which means included, and coctatus, which means ribbed.

The holotype is specimen OSU 28971-A. The specimen is 17 mm in diameter and has an 8 mm shoulder to shoulder umbilical diameter.

Photos of Metacoceras clinocostatum, CG-0169

This specimen was recovered from naturally chemical-altered limestone. This type of matrix is soft and readily preserves intricate details. After needing identification for quite some time, it is the first declared specimen in the catalog of M. clinocostatum. The ID is based on reported populations of specimens in the publication “Pennsylvanian Cephalopods of Ohio”, where 114 specimens were reported from the Brush Creek limestone. In reading the description, I found that the largest diameter paratype specimen was only 25 mm in diameter. Scale marks in the photo are 0.5 mm each. The specimen consists of 2/5 of a whorl. The umbilical depression is also sharply visible.

CG-0169, Metacoceras clinocostatum. 2/5 of a whorl with flank ribs easily seen.
CG-0169, M. clinocostatum. Flank view. 2/5 of a whorl with flank ribs easily seen.
Metacoceras clinocostatum dorsal view. Umbilical depression can be seen.
CG-0169, M. clinocostatum. Dorsal view. Umbilical depression can be seen, which is much smaller than the whorl.

Photos of Metacoceras clinocostatum, CG-0170

This is a specimen recovered from the Pine creek limestone. The specimen has 3-6 visible ribs on the flank. It consists of 1/2 of a whorl. There appears to be some shell material left. There is a well-defined umbilical shoulder. Specimen feels heavy, may be embedded in an ironstone concretion.

Flank view of Metacoceras clinocostatum. Catalog ID: CG-0170.
CG-0170, M. clinocostatum. Flank view. It Shows 1/2 of a whorl with some well-defined ribs on the flank. Umbilical depression can be clearly seen.
Ventrolateral view of Metacoceras clinocostatum. Catalog ID: CG-0170.
CG-0170, M. clinocostatum. Ventrolateral view.
M. clinocostatum. Flank view, coated with ammonium chloride.
CG-0170, M. clinocostatum. Flank view, coated with ammonium chloride to enhance contrast. Scale bar = 1 cm.

References