Williamsoceras
Encyclopedia
Williamsoceras is an endocerid that Rousseau Flower (1968) added to his Allotrioceratidae (Flower 1955) on the basis of having a vertical partition within the siphuncle
, known as a ventral process
, with inter-connecting tubule
-like structures along its margin where intercepted by endocone
s. Three species are named and described (Flower 1968) from the Garden City limestone of Whiterockian
age near Logan
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
in the Ibex area in western Utah.
are known only from the genotype
Williamsoceras adnatum. The other four are known only from pieces of siphuncle which show only internal configurations, but closely resemble that of the genotype.
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)
(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
(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.
of northern China and Korea (Flower 1955, 1968, Teichert 1964) derived from the Proterocameroceratidae
, by a lengthening of the septal necks.
Williamsoceras is included in the suborder Proterocameroceratina and is closely related to the Emmonsoceratidae
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 Spirula...
, known as a ventral process
Process (anatomy)
In anatomy, a process is a projection or outgrowth of tissue from a larger body. The vertebra has several kinds of processes,such as: transverse process, prezygapophysis, postzygapophysis.-Examples:Examples of processes include:...
, with inter-connecting tubule
Tubule
A tubule is a very small tube or fistular structure.A system of surface-connected membranes in muscle that enables a nerve impulse to travel to the interior of the muscle fibre.In anatomy, a tubule is a minute tube lined with glandular epithelium....
-like structures along its margin where intercepted by endocone
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 Spirula...
s. Three species are named and described (Flower 1968) from the Garden City limestone of Whiterockian
Whiterock Stage
The Whiterockian, often referred to simply as the Whiterock, is a 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 the older literature in a global sense.The...
age near Logan
Logan, Utah
-Layout of the City:Logan's city grid originates from its Main and Center Street block, with Main Street running north and south, and Center east and west. Each block north, east, south, or west of the origin accumulates in additions of 100 , though some streets have non-numeric names...
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
Confusion Range
The Confusion Range is a north-south trending mountain range in west-central Utah. 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. The range trends into the Burbank Hills, Mountain Home Range, and...
in the Ibex area in western Utah.
Description
Of the five described species the siphuncle wall and phragmoconePhragmocone
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 siphuncle which determines buoyancy by means of gas...
are known only from the genotype
Genotype
The genotype is the genetic makeup of a cell, an organism, or an individual usually with reference to a specific character under consideration...
Williamsoceras adnatum. The other four are known only from pieces of siphuncle which show only internal configurations, but closely resemble that of the genotype.
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
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 Spirula...
, the upper side being convex, the lower side concave.
The septal necks, described only from the genotype, are macrochoanitic
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 Spirula...
, 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 PerkinsocerasPerkinsoceras
Perkinsocerasis an endocerid genus from the Middle Ordovician of Champlain Valley established by Flower in 1976, which he added to his Allotrioceratidae based on certain similarities to Williamsoceras and Cacheoceras which had been added previously.Perkinsoceras is characterized by a large ventral...
(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
Champlain Valley
The Champlain Valley is a region of the United States around Lake Champlain in Vermont and New York extending slightly into Quebec, Canada as part of the St. Lawrence River drainage basin drained northward by the Richelieu River into the St...
(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 CanadianCanadian Epoch
The Canadian is the Lower or Early Ordovician in North America. The term is common in the older literature and has been well understood for more than a century...
of northern China and Korea (Flower 1955, 1968, Teichert 1964) derived from the Proterocameroceratidae
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....
, by a lengthening of the septal necks.
Williamsoceras is included in the suborder Proterocameroceratina and is closely related to the Emmonsoceratidae