AN OVERVIEW OF RESEARCH ON COLEOID CEPHALOPODS FROM TERTIARY ROCKS OF SOUTHERN NORTH AMERICA

To date, studies of coleoid cephalopods from Tertiary rocks of southern North America have yielded: guard-like sheaths of three species of belemnosellids, from the Eocene of Mississippi, Alabama, and Louisiana; of two genera of belosaepiids, from Alabama, Louisiana, Texas and North Carolina; of two genera of spirulids, one from the Miocene of Mexico, the other from the Oligocene of Alabama; and one other coleoid cephalopod of uncertain family affinity from the Oligocene of Alabama. Workers have also recovered phragmocone steinkerns of Beloptera? sp. and Anomalosaepia sp. from the Eocene of North Carolina.

Meyer & Aldrich (1886), preformed the first research on Tertiary coleoids from southern North America when they described Belemnosis americana from Claibornian sediments of Mississippi. Berry (1922), described Spirulirostra americana from Miocene sediments, Vera Cruz, Mexico. Palmer (1937) recognized the first belosaepiids from the Eocene of North America.

After a long hiatus, Jeletzky (1969), continued research into comparative morphology, phylogeny and classification of coleoid cephalopods but did not describe any new Tertiary specimens from North America. Garvie (1996) described one new species of Belosaepia from the Eocene of Texas. Weaver & Ciampaglio (2003), erected a new genus of belosaepiid, Anomalosaepia based on guard-like sheaths that were in some ways similar to Belosaepia, but markedly different.

Weaver et al. (2007), after acquiring several phragmocone steinkerns from the Eocene of North Carolina, recognized two different types, those with low angle, almost parallel septae as Beloptera? sp. and those with very strongly oblique septae as Anomalosaepia sp. Recently, Ciampaglio & Weaver (2008) reported, two types of diminutive, guard like sheaths from the Oligocene of Alabama. One is most likely a spirulid, while the other is so unlike other coleoids they were unable to place it into a family. These specimens, though possibly juvenile, marked the first record of Oligocene coleoids from North America.

Though the number of species of Eocene Belosaepia from North America is comparable to Europe, considerably more research is needed, especially on Oligocene and younger coleoids, to compare the two faunas and to assist in determining phylogenetic linkages with the modern.