''Meniscoceras'' is a straight and slender

Chazyan The Chazy Reef Formation is a mid-Ordovician limestone deposit in northeastern North America. It consists of some of the oldest reef systems built by a community of organisms rather than the deposit of a limited range of similar organisms, such ...

endocerid Endocerida is an extinct Nautiloidea, nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in their siphuncle. Endocerida was a diverse group of cephalopods that lived from the Early Ordovician possibly to the ...

described by

Rousseau Flower Rousseau Hayner Flower (1913–1988) was an extremely prolific 20th century paleontologist, known for his eccentric personality. Career Although trained as an entomologist, and a specialist in dragonflies and orthopterans, Flower began stud ...

in 1941 The genus was originally included in the

Proterocameroceratidae The ''Proterocameroceratidae'' were the first of the Endocerida. They began early in the Ordovician with ''Proendoceras'' or similar genus which had developed endocones, replacing the diaphragms of the ellesmerocerid ancestor. Proterocamerocerat ...

(Flower, 1955) but later (Flower, 1976) placed with its predecessor, ''

Najaceras ''Najaceras'' is a genus of straight, slender endocerid known only from the Whiterockian age Oil Creek Limestone of Oklahoma, introduced and named by Rousseau Flower in 1971 and further described by him in 1976. ''Najaceras'' is characterized ...

'', in the Najaceratidae. The

siphuncle The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Only cephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the living nautiluses, cuttlefish, and ...

in ''Mensicoceras'' is large with short septal necks and thin connecting rings. Endocones are vertically asymmetric. The central cavity is dorsally concave where a broad dorsal process is formed in which is said to contain a pair of dorso-lateral blades, and flat ventrally. ''Mensicoceras'' from the Chazy and the earlier ''Najaceras'' from the Whiterock age are similar in having a longitudual process formed along the inner dorsal side of the

around which the endocones form, but differ in details such as with the central opening. On that basis the two have been separated into their own family, the Najaceratidae (Flower 1971,1976). The ''

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

'' (1964) shows ''Meniscoceras'' in the Proterocameroceratidae, a carry over from before the time its ancestor, ''Najaceras'' was discovered. The type species, ''Meniscoceras coronense'', is known from the Chazyan of New York State.

References

*Flower R. H. 1955, Status of Endoceroid Classification, Journ Paleontology V.29, no.3, May 1955, pp 329– 370 *– – –, 1971; Cephalopods of the Whiterock Stage; Smithsonian Contributions to Paleontology No 3, 1971 *– – –, 1976, Part II - Some Whiterock and Chazy Endoceroids; Mem. 28, New Mexico Bureau of Mines & Mineral Resources, 1976 *Teichert, C, 1964, Treatise on Invertebrate Paleontology, Vol K, p. K166 & 170; GSA and University of Kansas Press. {{Taxonbar, from=Q3854692 Nautiloids Ordovician cephalopods Ordovician animals of North America Taxa named by Rousseau H. Flower Prehistoric nautiloid genera