Image: Graftonoceras fossil nautiloid (Lockport Dolomite, Middle Silurian; Coldwater, southern Mercer County, western Ohio, USA) (15054984258)

Description: Graftonoceras - limonite-stained external mold in dolostone (public display, OSU 24835, Orton Geology Museum, Ohio State University, Columbus, Ohio, USA). Nautiloids are squid-like creatures that construct long and slightly tapering or coiled, aragonitic, hollow shells with regularly-spaced internal walls. In the fossil record, the original aragonite shell has usually dissolved away, leaving an internal mold (an impression of the shell's interior). Nautiloids were relatively common components of Paleozoic oceans. Most species had straight, slightly tapering shells, but some had loosely coiled or tightly coiled shells. The entire group is represented in today's oceans by three living species of chambered nautilus - Nautilus pompilius, Nautilus macromphalus, and Allonautilus scrobiculatus. This external mold of a Graftonoceras nautiloid has a coiled shell. The pattern of its original shell ornament, consisting of curvilinear waves, is still preserved. Classification: Animalia, Mollusca, Cephalopoda, Nautiloidea, Tarphycerida, Trocholitidae Stratigraphy: Lockport Dolomite, Niagaran Series, Middle Silurian Locality: unrecorded locality (probably a quarry) at or near Coldwater, southern Mercer County, western Ohio, USA
Title: Graftonoceras fossil nautiloid (Lockport Dolomite, Middle Silurian; Coldwater, southern Mercer County, western Ohio, USA) (15054984258)
Credit: Graftonoceras fossil nautiloid (Lockport Dolomite, Middle Silurian; Coldwater, southern Mercer County, western Ohio, USA)
Author: James St. John
Usage Terms: Creative Commons Attribution 2.0
License: CC BY 2.0
License Link: http://creativecommons.org/licenses/by/2.0
Attribution Required?: Yes