Homaloceras
Encyclopedia
Homaloceras is an extinct nautiloid cephalopod from the Middle Devonian
with a strongly curved shell, included in the nautilid
family Centroceratidae
.
Homaloceras is characterized by a smooth, exogastically curved and laterally compressed, cyrtoconic to gyroconic, shell with the ventral margin the outer rim. The venter is narrow and concave with a groove running down the middle; the dorsum on the inner rim,rounded; the sides broadly convex and convergent. The suture is only slightly sinuous, the siphuncle
tubular and near the venter. (Kummel 1964)
Homaloceras, named by Whiteavus in 1891, and found in North America, in Canada, is the most primitive and one of the earliest genera assigned to the Centroceratidae. (Kummel 1964)
The Nautiloidea, in which Homaloceras is included, is a subclass of once diverse and numerous shelled cephalopods characterized by a retrochoantic siphuncle in which the septal necks point back toward the apex.
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...
with a strongly curved shell, included in the nautilid
Nautilida
The Nautilida constitute a large and diverse order of generally coiled nautiloid cephalopods that began in the mid Paleozoic and continues to the present with a single family, the Nautilidae which includes two genera, Nautilus and Allonautilus, with six species...
family Centroceratidae
Centroceratidae
The Centroceratidae is the ancestral family of the Trigonocerataceae and of the equivalent Centroceratina; extinct shelled cephalopods belonging to the order Nautilida-Diagnosis:...
.
Homaloceras is characterized by a smooth, exogastically curved and laterally compressed, cyrtoconic to gyroconic, shell with the ventral margin the outer rim. The venter is narrow and concave with a groove running down the middle; the dorsum on the inner rim,rounded; the sides broadly convex and convergent. The suture is only slightly sinuous, the siphuncle
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...
tubular and near the venter. (Kummel 1964)
Homaloceras, named by Whiteavus in 1891, and found in North America, in Canada, is the most primitive and one of the earliest genera assigned to the Centroceratidae. (Kummel 1964)
The Nautiloidea, in which Homaloceras is included, is a subclass of once diverse and numerous shelled cephalopods characterized by a retrochoantic siphuncle in which the septal necks point back toward the apex.
See also
- CentroceratidaeCentroceratidaeThe Centroceratidae is the ancestral family of the Trigonocerataceae and of the equivalent Centroceratina; extinct shelled cephalopods belonging to the order Nautilida-Diagnosis:...
- Nautiloidea
- List of nautiloids