''Najaceras'' is a genus of straight, slender

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 ...

known only from the

Whiterockian The Whiterockian, often referred to simply as the Whiterock, is an earliest or lowermost stage of the Middle Ordovician. Although the Whiterockian or Whiterock Stage refers mainly to the early Middle Ordovician in North America, it is often used in ...

age Oil Creek Limestone of Oklahoma, introduced and named 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 1971 and further described by him in 1976. ''Najaceras'' is characterized by a longitudinal mound of material that runs forward from the apical region along the inside of the top of 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 ...

known as a dorsal process. This process, which is somewhat broad in aspect, is concave ventrally. The opening between the dorsal process and the endocone forms a dorsally concave crescent shape. The process is bisected in the lower port by which is known as a blade which bifurcates upwardly from about the middle. The

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

''Najaceras'' is based on ''Najaceras triangulatum'' (Flower, 1971) which comes from the Oil Creek Limestone on West Spring Creek, 3 miles east of

Pooleville, Oklahoma Pooleville is a community located in Carter County, Oklahoma, United States. It is west of the Arbuckles. During the territorial days, the community was originally known as Elk.Shirk, George H. ''Oklahoma Place Names'', Norman, Oklahoma: Universi ...

. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

and

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). Of ...

are at the U.S. National Museum. Two other species from the same area have been identified and named: ''N. bilobatum'', and ''N. chevroniferum'' (Flower, 1976). ''Najaceras'' probably gave rise to the similar ''

Meniscoceras ''Meniscoceras'' is a straight and slender Chazyan endocerid described by Rousseau Flower in 1941 The genus was originally included in the Proterocameroceratidae (Flower, 1955) but later (Flower, 1976) placed with its predecessor, ''Najaceras'', ...

'' which also has a dorsal process. Based on that unique feature the two are placed in their own family, the Najaceratidae. ''Najaceras'' comes from "naja", the word for the crescent at the bottom of the

Navajo The Navajo (; British English: Navaho; nv, Diné or ') are a Native American people of the Southwestern United States. With more than 399,494 enrolled tribal members , the Navajo Nation is the largest federally recognized tribe in the United ...

squash blossom or wedding necklace.

References

* Flower, R. H, (1971); Cephalopods of the Whiterock Stage; Smithsonian Contributions to Paleontology No. 3 * Flower, R. H. (1976), Part II - Some Whiterock and Chazy Endoceroids; Mem. 28, New Mexico Bureau of Mines & Mineral Resources {{Taxonbar, from=Q6959872 Nautiloids Prehistoric cephalopod genera Ordovician animals of North America Taxa named by Rousseau H. Flower