Williamsoceras is an

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 ...

that

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 ...

(1968) added to his

Allotrioceratidae The Allotrioceratidae is a family of Middle Ordovician fossils, established by Rousseau Flower, 1955, originally including ''Allotrioceras'' and '' Mirabilocras'', assigned inferentially to the Endocerida and known only from structures interprete ...

(Flower 1955) on the basis of having a vertical partition within 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 ventral

process A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

, with inter-connecting

tubule In biology, a tubule is a general term referring to small tube or similar type of structure. Specifically, tubule can refer to: * a small tube or fistular structure * a minute tube lined with glandular epithelium * any hollow cylindrical body stru ...

-like structures along its margin where intercepted by endocones. Three species are named and described (Flower 1968) from the Garden City limestone of

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 near

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and northern Utah, including the genotype ''Williamsoceras adnatum''. Two other species come from the Juab limestone (Flower 1976) of near equivalent age in the southern

Confusion Range The Confusion Range is a north-south trending mountain range in west-central Utah, United States. It is bounded by Snake Valley to the west, Tule Valley to the east, the Great Salt Lake Desert to the north, and the Ferguson Desert to the south. ...

in the Ibex area in western Utah.

Description

Of the five described species the siphuncle wall and

phragmocone The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a ...

are known only from the

genotype The genotype of an organism is its complete set of genetic material. Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. The number of alleles an individual can have in a ...

''Williamsoceras adnatum''. The other four are known only from pieces of siphuncle which show only internal configurations, but closely resemble that of the

. ''Williamsoceras'' is characterized by a ventral process within the siphuncle that extends vertically from the bottom side, essentially bisecting the interior. The process is straight sided and narrow in the more forward part of the siphuncle, approaching the body chamber, and swells to a bulbous or teardrop shape in cross section closer to the apex of the siphuncle where it becomes draped by endocones. As the ventral process and endocones approach a crescent shape space is formed, known as the endosiphocone, the upper side being convex, the lower side concave. The septal necks, described only from the genotype, are macrochoanitic, extending 1.5 segments back from their origin. and is slightly sinuous in profile (Flower 1968, 1976)

Comparisons

''Williamsoceras'' is similar to '' Cacheoceras'' which comes from the same areas and formations, except that ''Cacheoceras'' has additional smaller processes, either one on the dorsal side opposite the main process or a pair that are positioned dorsolaterally. It differs from '' Emmonsoceras'' (Flower 1955, 1976; Techert 1964) and from ''

Perkinsoceras ''Perkinsoceras''is an endocerid genus from the Middle Ordovician (Chazyan) of Champlain Valley established by Flower in 1976, which he added to his Allotrioceratidae based on certain similarities to ''Williamsoceras'' and '' Cacheoceras'' which ...

'' (Flower 1976) in that the ventral process in these is broad and in broad contact with the lower side of the siphuncle. ''Williamsoceras'' differs from ''Allotrioceras'' from the Chazian of

Champlain Valley The Champlain Valley is a region of the United States around Lake Champlain in Vermont and New York extending north slightly into Quebec, Canada. It is part of the St. Lawrence River drainage basin, drained northward by the Richelieu River into ...

(Flower 1955) in the manner in which the central processes are formed and that the features in ''Willimasoceras'' are bilaterally symmetrical while those in ''Allotrioceras'' are definitely asymmetric.

Origin and classification

''Williamsoceras'' may have its origin in the Manchuroceratidae from the upper

Canadian Canadians (french: Canadiens) are people identified with the country of Canada. This connection may be residential, legal, historical or cultural. For most Canadians, many (or all) of these connections exist and are collectively the source of ...

of northern China and Korea (Flower 1955, 1968, Teichert 1964) derived from 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 ...

, by a lengthening of the septal necks. ''Williamsoceras'' is included in the suborder Proterocameroceratina and is closely related to the Emmonsoceratidae

References

* Flower 1955; Status of Endoceroid Classification; ''Journal of Paleontology'', V.29,n.3, May 1955, pp329–372 * Flower 1968; Some Additional Whiterock Cephalopods, Part II, Memoir 19, New Mexico Bureau of Mines and Mineral Resources, Socorro. NM * Flower 1976; Some Whiterock and Chazy Endoceroids; Part II, Memoir 28, New Mexico Bureau of Mines and Mineral Resources, Socorro. NM * Teichert, 1964; ''Endoceratoidea in the Treatise on Invertebrate Paleontology'', Curt Teichert and R.C. Moore,eds, GSA and Univ Kansas Press. {{Taxonbar, from=Q8021193 Nautiloids Taxa named by Rousseau H. Flower