Endoceratidae
Encyclopedia
The Endoceratidae is a family of large to very large straight shelled nautiloid cephalopods belonging to the order Endocerida that lived during the Middle and Late Ordovician. They include the largest known Paleozoic invertebrates, represented by Endoceras
and Cameroceras.
and their derivatives. Endocones, nested cone-shaped deposits characteristic of the Endocerida, form in the apical portion of the siphuncle where they balanced the weight of the animal in the body chamber at the opposite end. This helped assure a horizontal orientation while the endoceratid animal was alive. Septal necks are holochoantitic, reaching the previous septum and sometimes beyond, as macrochoantic. Connecting rings, which may be moderately thin, form a lining on the interior of the necks. In some forms, such as Nanno and Chazyoceras
the siphuncle is swollen at the apex so as to preclude the presence of adjacent camerae. In others, such as Cameroceras and Vaginoceras the siphuncle is tubular with chambers formed adjacently from the very start. The taxonomic significance of either in undetermined, other than as used to define a particular genus.
(Lower Ordovician) Piloceratidae
according to Rousseau Flower, which have similar simple structured siphuncles, although they may resemble proterocameroceratids in general form. Accordingly Flower included the Endoceratdae and Piloceratidae, along with the Cyrtendoceratidae, in a suborder, the Endoceratina.
, Triendoceras
. and Allocotoceras
from the Lower Ordovician
Genera included are:
Endoceras
Endocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in its siphuncle.Endocerida comprises a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian . Their shells varied in form...
and Cameroceras.
Descriptive Characters
Endocerids are characterized by large, generally ventral,siphuncles with simple endocones which lack the more complex structures associated with the ProterocameroceratidaeProterocameroceratidae
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....
and their derivatives. Endocones, nested cone-shaped deposits characteristic of the Endocerida, form in the apical portion of the siphuncle where they balanced the weight of the animal in the body chamber at the opposite end. This helped assure a horizontal orientation while the endoceratid animal was alive. Septal necks are holochoantitic, reaching the previous septum and sometimes beyond, as macrochoantic. Connecting rings, which may be moderately thin, form a lining on the interior of the necks. In some forms, such as Nanno and Chazyoceras
Chazyoceras
Chazyoceras is a moderately large endocerid included in the Endoceratidae with a Nanno type apex and a ventral siphuncle with a holochoanitic wall, characteristic of the family. The siphuncle swelling at the apex is subtriangular in longitudinal profile. Endocones are of medium length.Chazyoceras...
the siphuncle is swollen at the apex so as to preclude the presence of adjacent camerae. In others, such as Cameroceras and Vaginoceras the siphuncle is tubular with chambers formed adjacently from the very start. The taxonomic significance of either in undetermined, other than as used to define a particular genus.
Origin
The Endoceratidae arose 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...
(Lower Ordovician) Piloceratidae
Piloceratidae
The Piloceratidae are a compressed, rapidly expanding, cyrtoconic brevicones with holochoanitic ventral siphuncles and simple endocones. Most likely evolved from Clitendoceras, a narrow, slightly endogastric genus intermediate in form between straight shelled Proendoceras and the bulkier...
according to Rousseau Flower, which have similar simple structured siphuncles, although they may resemble proterocameroceratids in general form. Accordingly Flower included the Endoceratdae and Piloceratidae, along with the Cyrtendoceratidae, in a suborder, the Endoceratina.
Genera
Flower restricted the Endoceratidae to those genera from the Middle and Upper Ordovician, and possibly lower Silurian, belonging to the Endocerida with holochoantic or macrochoanitic septal necks and simple endocones. Teichert added ProterovaginocerasProterovaginoceras
Proterovaginoceras is a medium to large sized endocerid from the Early and Middle Ordovician included in the family Endoceratidae....
, Triendoceras
Triendoceras
Triendoceras is a fairly large endocerid named by Flower , included in the Endoceratidae by Teichert , characterized by a holochoanitic ventral siphuncle in which the cross section through the endocones has an opening in the shape of an isosceles triangle with a sharp apex pointing down...
. and Allocotoceras
Allocotoceras
Allocotoceras is an endocerid from the Lower Ordovician of Australia , included in the Endoceratidae, based on small, straight or gently curved siphuncles....
from the Lower Ordovician
Genera included are:
- AllocotocerasAllocotocerasAllocotoceras is an endocerid from the Lower Ordovician of Australia , included in the Endoceratidae, based on small, straight or gently curved siphuncles....
- Cameroceras
- ChazyocerasChazyocerasChazyoceras is a moderately large endocerid included in the Endoceratidae with a Nanno type apex and a ventral siphuncle with a holochoanitic wall, characteristic of the family. The siphuncle swelling at the apex is subtriangular in longitudinal profile. Endocones are of medium length.Chazyoceras...
- DiderocerasProterovaginocerasProterovaginoceras is a medium to large sized endocerid from the Early and Middle Ordovician included in the family Endoceratidae....
- EndocerasEndocerasEndocerida is an extinct nautiloid order, a group of cephalopods from the Lower Paleozoic with cone-like deposits in its siphuncle.Endocerida comprises a diverse group of cephalopods that lived from the Early Ordovician possibly to the Late Silurian . Their shells varied in form...
- FoerstellitesFoerstellitesFoerstellites is an Ordovician cephalopod genus from North America, belonging to the family Endoceratidae, in which the siphuncle takes up the entire apex....
- Kotoceras
- Kutorgoceras
- Lamottoceras
- Liskeardia
- Nanno
- ProterovaginocerasProterovaginocerasProterovaginoceras is a medium to large sized endocerid from the Early and Middle Ordovician included in the family Endoceratidae....
- SuecocerasSuecocerasSuecoceras is an endoceratid that lived during the Middle Ordovician. It is characterised by a long, straight, slender shell with a slightly expanded tip that curves slightly downwards....
- Tasmanoceras
- TriendocerasTriendocerasTriendoceras is a fairly large endocerid named by Flower , included in the Endoceratidae by Teichert , characterized by a holochoanitic ventral siphuncle in which the cross section through the endocones has an opening in the shape of an isosceles triangle with a sharp apex pointing down...
- Vaginoceras
- Vaningenoceras