Tarphyceras
Encyclopedia
Tarphyeras is a genus of tarphyceratid
with whorls rounded in cross section, having a deeply impressed dorsum and a ventral to subcentral siphuncle
, known from the Lower Ord
(U Canad
) of North America. It differs from Campbelloceras
in that Campbelloceras is only slightly impressed, from Centrotarphyceras in that Centrotarphyceras is subquadrate and has a central siphuncle, and from Trocholites
in that although Trocholites is subcircular in cross section, the siphuncle is subdorsal.
Taphyceras may be derived from Campbelloceras through development of tighter coiling and a deeper impression along with a smaller siphuncle that may be further offset from the venter.
Tarphyceras was named by Hyatt in 1894.
Tarphyceratidae
The Tarphyceratidae are tightly coiled, evolute Tarphycerida with ventral siphuncles. The dorsum is characteristically impressed where the whorl presses against the venter of the previous. The Tarphyceratidae are derived from Bassleroceras or possibly from some member of the...
with whorls rounded in cross section, having a deeply impressed dorsum and a ventral to subcentral 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...
, known from the Lower Ord
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
(U Canad
Canadian 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 North America. It differs from Campbelloceras
Campbelloceras
Campbelloceras: a tarphyceratid with a circular whorl section, only slightly impressed, and a siphuncle that is close to the venter in all growth stages. Differs from Tarphyceras in that the rate of expansion is greater, the siphuncle is proportionally largers, and an impression is shallower...
in that Campbelloceras is only slightly impressed, from Centrotarphyceras in that Centrotarphyceras is subquadrate and has a central siphuncle, and from Trocholites
Trocholites
Trocholites is a tarphycerid genus in the fa mily Trocholitidae from the Middle and Upper Ordovician with a gradually expanding, weakly ribbed shell; whorls in contact, dorsum slightly impressed; cross section depressed, venter and sides rounded; siphuncle close to but not at the dorsal margin.The...
in that although Trocholites is subcircular in cross section, the siphuncle is subdorsal.
Taphyceras may be derived from Campbelloceras through development of tighter coiling and a deeper impression along with a smaller siphuncle that may be further offset from the venter.
Tarphyceras was named by Hyatt in 1894.