Murrayoceras
Encyclopedia
Murrayoceras is a nautilid cephalopod included in the orthocerid
family Baltoceratidae
, wide spread in the Middle Ordovician of North America, characterized by a depressed orthoconic shell with a subtriangular cross section and flattened venter and a proportionally large verntral siphuncle, 0.15 to 0.3 the dorso-ventral shell diameter. Septa are close spaced with sutures forming broad lobes on the upper flanks and ventral surface.
As originally perceived Murrayoceras included species differing in siphuncle profile. Those in which the siphuncle segments are externally convex were redefined as Cartersoceras., leaving Murrayoceras with those having essentially straight, tubular, or slightly concave segments.
Murrayoceras has a ventral rod in the siphuncle , putting it thereby in the rod-bearing Baltoceratidae, and closely related to Rhabdiferoceras
and Cartersoceras
, among others. In some recent classifications however Murrayoceras has been reassigned to the Sactorthoceratidae
although Frey (1995) did retain the genus in the Baltoceratidae.
Orthocerida
Orthocerida is an order of extinct nautiloid cephalopods also known as the Michelinocerda that lived from the Early Ordovician possibly to the Late Triassic . A fossil found in the Caucasus suggests they may even have survived until the Early Cretaceous...
family Baltoceratidae
Baltoceratidae
Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, existing for approximately .-Taxonomy:Baltoceratidae was...
, wide spread in the Middle Ordovician of North America, characterized by a depressed orthoconic shell with a subtriangular cross section and flattened venter and a proportionally large verntral siphuncle, 0.15 to 0.3 the dorso-ventral shell diameter. Septa are close spaced with sutures forming broad lobes on the upper flanks and ventral surface.
As originally perceived Murrayoceras included species differing in siphuncle profile. Those in which the siphuncle segments are externally convex were redefined as Cartersoceras., leaving Murrayoceras with those having essentially straight, tubular, or slightly concave segments.
Murrayoceras has a ventral rod in the siphuncle , putting it thereby in the rod-bearing Baltoceratidae, and closely related to Rhabdiferoceras
Rhabdiferoceras
Rhabdiferoceras is an extinct orthocerid genus belonging to the Baltoceratidae that lived in what would be North America during the Cassinian Stage at the end of the Early Ordovician, existing for approximately two million years from about 474 -472 mya....
and Cartersoceras
Cartersoceras
Cartersoceras is a nautiloid cephalopod genus placed in the Orthocerid family Baltoceratidae, established by Rousseau Flower, 1964, for species formally included in part in Murrayoceras, and in part in "Sacotoceras", which are typical of Murrayoceras in all features except that the siphuncle...
, among others. In some recent classifications however Murrayoceras has been reassigned to the Sactorthoceratidae
Sactorthoceratidae
The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic siphuncle composed of slightly expanded segments and free of organic depsits...
although Frey (1995) did retain the genus in the Baltoceratidae.