Kazakhstania colubrella (Morton, 1836) mold in quartzose sandstone from the Mississippian of Ohio, USA. (1.75 cm across)

Many fossils of shelly organisms (e.g., bivalves, gastropods, brachiopods, cephalopods) have had the original hard parts dissolved away. In such cases of dissolution, the fossil itself is an impression of the outside of the shell (external mold) or an impression of the inside of the shell (internal mold).

The specimen shown above is mold of a goniatite. Goniatites are a group of ammonoid cephalopods with relatively simple suture patterns. Sutures are the lines formed by the intersection of the outer shell wall and the internal walls (septa) that separate chambers. Nautiloid cephalopods (e.g., the modern pearly nautilus) generally have curvilinear suture patterns. Ammonoid cephalopods have goniatitic, ceratitic, or ammonitic suture patterns. Goniatitic sutures are characterized by having several broad lobes & saddles. Goniatitic sutures are seen in the earliest ammonoids.

This is a rare species of ammonoid cephalopod - Kazakhstania colubrella (formerly Prolecanites colubrellus) from the Byer Sandstone at Chatham, Ohio, USA. It has a planispirally coiled shell (as do almost all ammonoids) and a distinctive goniatitic suture pattern (see Manger, 1971, figure 6D) - the yellowish-brown wavy lines in the above specimen are the sutures. Adult shells show four, narrow, external constrictions (not visible in this specimen) (see Manger, 1971, plate 12, figures 8, 10-12).

Classification: Animalia, Mollusca, Cephalopoda, Ammonoidea, Goniatitina, Imitoceratidae

Host rock & stratigraphy: slightly micaceous quartzose sandstone, float from the Byer Sandstone Member, lower Logan Formation, Waverly Group, Osagean Stage, upper Lower Mississippian

Locality: loose piece from rubble along petroleum well access road, southern side of St. Joseph Road, due east of Chatham, northwestern Newton Township, northern Licking County, central Ohio, USA (~40º 09’ 18.7” North, ~82º 26’ 29.2” West)

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