Cephalopoda
Subclass Nautiloidea
ENDOCERIDA
Endoceras proteiforme Hall, 1847 - Description from Flower, 1955
Description: Shell large, straight, and externally smooth. Cross section is slightly wider than high in the mature portion, but compressed in cross section in the young portion. Sutures are straight and transverse. Siphuncle is close to the ventral wall of the shell. Segments are concave between the septa in the young, but often tubular in outline in the adult. The sipuncle wall is composed of holochoanitic necks and connecting rings. Endosiphuncle composed of endocones.
Ecology: Active swimmers and posthumous floaters.
Endoceras sp. Hall, 1847 - Description from Teichert, 1964c
Description: Shell large and straight. Endoceras is similar to Cameroceras, but with annulations varying from low and closely spaced to well elevated and distinctly apart. Cross section is slightly depressed and sutures are straight and transverse. The siphuncle is large, ventral, and holochoanitic. Endocones are subcircular in cross section. Has thin endosiphuncular tube.
Ecology: Active swimmers and posthumous floaters.
ACTINOCERIDA
Actinoceras sp. Bronn, 1835 - Description from Teichert, 1964d
Description: Shell is large, straight, and somewhat fusiform, with a tendency to decrease in diameter from anterior part of phragmocone toward aperature. The cross section is subcircular to circular. Siphuncle is large, generally somewhat off center with the tendency to decrease in diameter toward the adult portion of phragmocone. Septal necks are long and brims are relatively short. Has a narrow endosiphuncular canal in the mature stage with simple radial canals. Cameral deposits are common, generally of episeptal and hyposeptal type and a ciruculus is present in a few species.
Ecology: Active swimmers and posthumous floaters.
Ormoceras sp. Stokes, 1840 - Description from Teichert, 1964d
Description: Shell medium-sized, straight, and more or less circular in cross section. The siphuncle is generally subcentral and segments are almost globular. Septal necks are short and actinoceroid, with short brims. The endosiphuncular canal system is moderately complex to simple with few radial canals. Cameral deposits are common.
Ecology: Active swimmers and posthumous floaters.
ORTHOCERIDA
Arionoceras sp. Barskov, 1966 - Description from Gnoli, 1998
Description: Shell relatively short, straight to slightly curved (most commonly endogastrically). Cross section is circular. Has a narrow, cylindrical, central siphuncle.
Ecology: Active swimmers and posthumous floaters.
Centroonoceras (?) sp. Kobayashi, 1934 - Description from Sweet, 1964a
Descripition: Shell is cyrtoconic. Subcentral siphuncle is suborthochoanitic, with elongate subfusiform segments that are generally straighter on dorsum than venter. No cameral deposits known.
Ecology: Active swimmers and posthumous floaters.
Clinoceras exiguum - Description from Sweet, 1964a
Description: Shell is an elongate, subfusiform cyrtocone with virtually straight to slightly concave dorsum and more distinctly convex venter. Conch is constricted in anterior part of body chamber, then expanding to aperture. The surface is marked by sinuous growth lines, which form a pair of ventral and lateral sinuses. The siphuncle is dorsal of center and cyrtochoanitic. Segements are slightly expanded ventrally, flat or faintly concave dorsally, and empty.
Ecology: Active swimmers and posthumous floaters.
Geisonoceras sp. Hyatt, 1884 - Description from Sweet, 1964a
Description: Shell is a slowly enlarging orthocone or cyrtocone of circular to subcircular cross section with straight transverse or slightly oblique sutures. The siphuncle is subcentral. Septal necks are short and straight and connecting rings expand slightly within the camerae. Small adorally attenuated annulosiphonate deposits are found in adapical siphuncular segments. Have camerae with episeptal and hyposeptal deposits. Surface of shell has broad transverse bands, between which are fine growth lines. The aperture is transverse, with a slightly hyponomic sinus.
Ecology: Active swimmers and posthumous floaters.
Kionoceras sp. Hyatt, 1884 - Description from Sweet, 1964a
Description: Shell is a slender to rapidly expanding, apically curved, longitudinally fluted orthocone of circular to subcircular section. Has a surface ornament of prominent longitudinal ribs separated by concave interspaces. In most species there are less conspicuous longitudinal and transverse lirae or striae. Early-formed part of test may be faintly annulated. The siphuncle is central to subcentral and empty in most Ordovician species. Septal necks are straight or suborthochoanitic and segments are cylindrical or weakly expanded within camerae.
Ecology: Active swimmers and posthumous floaters.
Leurocycloceras sp. Foerste, 1928 - Description from Sweet, 1964a
Description: Shell is a slender, circular or slightly compressed orthocone with asymmetrically curved septa and straight transverse or slightly oblique sutures. The surface has low annulations. In some species annulations are so broad and flat that interspaces are only narrowly incised striae on an otherwise smooth exterior. The siphuncle is eccentric, orthochoanitic, and empty. Septal necks are unusually long and straight and connecting rings are unknown. Have moderate episeptal and strong hyposeptal deposits. In advanced stages, these deposits may join through septal foramen with those of adjacent camerae to enclose the septal necks completely.
Ecology: Active swimmers and posthumous floaters.
Michelinoceras sp. Foerste, 1932 - Description from Sweet, 1964a
Description: Shell is a long, slender, and subcylindrical orthocone of circular section with long camerae and a very long body chamber. The siphuncle is central or eccentric by no more than its own diameter and is empty. Septal necks are straight. Connecting rings are homogeneous and cylindrical. Have well developed hyposeptal and episeptal deposits in camerae.
Ecology: Active swimmers and posthumous floaters.
Murchinsoniceras sp. - Description from Dzik, 1984
Description: Shell is compressed and relatively short with septa spaced more densely. The septal necks are shorter than in Leurocycloceras sp. Siphuncle is subcentral and there are no cameral or siphonal deposits.
Ecology: Active swimmers and posthumous floaters.
Orthoceras sp. Bruguière, 1789 - Description from Sweet, 1964a
Description: Shell is a slightly expanding and almost cylindrical orthocone or a faintly exogastric cyrtocone. Has an empty subcentral to slightly ventral cylindrical orthochoanitic siphuncle. The body chamber is transversely constricted at mid-length and is marked by a single longitudinal dorsal and 2 longitudinal ventral depressions. Surface is ornamented by a network of fine lirae. The internal surface is faintly striated longitudinally, with a prominent conchal furrow on venter. The muscle attachment is dorsomyarian.
Ecology: Active swimmers and posthumous floaters.
Parakionoceras sp. Foerste, 1928 - Description from Sweet, 1964a
Description: Shell is a faintly curved, uncompressed, exogastric longicone with relatively long camerae and straight transverse sutures. Has a surface with sharp-edged longitudinal ribs separated by broader concave interspaces. The siphuncle is slightly eccentric and empty. The septal necks are short and directed obliquely toward siphuncle axis. Connecting rings are somewhat inflated at the septal necks, otherwise cylindrical. Cameral deposits are well developed.
Ecology: Active swimmers and posthumous floaters.
Plagiostomoceras undet. Teichert and Glenister, 1952 - Description from Sweet, 1964a
Description: Shell is a long slender orthocone with a circular to slightly depressed cross section. Sutures are straight or slightly oblique. May develop faint lateral lobes. Septa are moderately concave. Aperture is strongly oblique, sloping adapically from antisiphuncular side. In lateral view, aperture is somewhat sinuous, sloping more strongly on side and flattening on both antisiphuncular and siphuncular sides. Surface with growth lines and weak ridges parallel to aperture. Siphuncle is central, eccentric, and orthochoanitic.
Ecology: Active swimmers and posthumous floaters.
Spyroceras sp. Hyatt, 1884 - Description from Sweet, 1964a
Description: Shell is an annulated orthocone with straight transverse sutures. Have transverse or slightly oblique surficial annulations and faintly cyrtoconic apices. Surface is variously ornamented, but longitudinal lirae conspicuous from earliest stage. Siphuncle is central or slightly ventral from center and orthochoanitic. Has mural deposits.
Ecology: Active swimmers and posthumous floaters.
ONCOCERIDA
Eorizoceras sp. Flower, 1943 - Description from Sweet, 1964b
Description: Shell is apically curved, adorally straight, rapidly expanding, and faintly compressed. The ephebic (adult) section is ovoid and sutures are straight and slightly oblique. Has an exterior with transverse bands and finer longitudinal markings. Shows no hyponomic sinus. The siphuncle is small and ventral.
Ecology: Active swimmers and posthumous floaters.
Maelonoceras(?) sp. Hyatt, 1884 - Description from Sweet, 1964b
Description: Shell is a faintly gibbous cyrtocone with subparallel dorsal and ventral profiles, but has adorally converging sides on body chamber. Aperture is partially visored, pear-shaped, with a hyponomic sinus. The siphuncle is small and ventral.
Ecology: Active swimmers and posthumous floaters.
Oocerina sp. Foerste, 1926 - Description from Sweet, 1964b
Description: Like Oonoceras, but siphuncular segments nummuloidal and actinosiphonate.
Ecology: Active swimmers and posthumous floaters.
Oonoceras sp. Hyatt, 1884 - Description from Sweet, 1964b
Description: Shell is a slender compressed cyrtocone of slight curvature with gradual enlargement. Have sutures with lateral lobes. The camerae and body chamber are short. Has aperture with hyponomic sinus. The siphuncle is close to venter, cyrtochoanitic,and empty. Segments are either slightly or broadly expanded with camerae.
Ecology: Active swimmers and posthumous floaters.
Oncoceras constrictum Hall, 1847 - Description from Sweet, 1964b
Description: Shell is a compressed, curved brevicone with a gibbous behind body chamber contracting to aperture. At gibbous region, convexity of ventral profile is typically increased. The dorsal profile is concave adapically and convex over gibbous region. Siphuncle is small and ventral. The segments are ovoid to scalariform and generally longer than wide. Septal necks are short and recurved.
Ecology: Active swimmers and posthumous floaters.
Tripteroceras sp. Hyatt, 1884 - Description from Sweet, 1964b
Description: Shell is small, straight, or slightly exogastric with broadly depressed triangular section. Venter broad and flat, lateral angles acute, dorsum divided by median ridge or keel; dorsolateral regions flat or slightly concave. Sutures with dorsal and ventral lobes. Siphuncle small, ventral; segments slightly expanded, interior not well known, but apparently empty.
Ecology: Active swimmers and posthumous floaters.
Valcouroceras sp. Flower, 1943 - Description from Sweet, 1964b
Description: Shell is a curved cyrtocone with gibbous body chamber and oblique sutures. It is compressed in early stages and later flattened dorsally, then depressed and subtriangular. May be compressed at adapical end of body chamber. Early stages of siphuncle are suborthochoanitic, ventral, and empty. Later segments are more inflated with thicker rings and actinosiphonate deposits.
Ecology: Active swimmers and posthumous floaters.
TARPHYCERIDA
Trocholites ammonius Conrad, 1838 - Description from Furnish and Glenister, 1964b
Description: Shell is gradually expanded and weakly ribbed. Whorls are strongly depressed, weakly impressed, and rounded across the venter and flanks. The siphuncle is subdorsal.
Ecology: Active swimmers and posthumous floaters.
BARRANDEOCERIDA
Lechritrochoceras sp. Foerste, 1926 - Description from Sweet, 1964c
Description: Shell is very low-spired, gyroconic, dextral torticone of 2 or fewer compressed, flat-sided volutions (or whorls)with venter more narrowly rounded than dorsum. Whorls are in contact only at extreme adapical end of conch, but neither phragmocone nor body chamber diverges very broadly from preceding whorls. The sutures have lateral lobes and dorsal and ventral saddles. Surface has transverse annulations prominent ventrally, less so laterally, and faint dorsally. Annulations form a prominent ventral hyponomic sinus. The siphuncle is between center and venter and segments are cylindrical.
Ecology: Active swimmers and posthumous floaters.
