Class Cephalopoda
 
   
                     
                                     
 
                                     
                   
   

SUBCLASS NAUTILOIDEA

ENDOCERIDA

ACTINOCERIDA

ORTHOCERIDA

ONCOCERIDA

TARPHYCERIDA

BARRANDEOCERIDA

 
   
-Species Descriptions-
 
   
-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 proteiforme, MCZ 128593            
     
MCZ 128593: 122mm long
           

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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.

 

  Endoceras sp., MCZ 128771 Endoceras sp., MCZ 128730    
 
MCZ 128771: 79mm long

MCZ 128730: 151mm long

 

   

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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.


      Actinoceras sp., MCZ 129014            
     
MCZ 129014: 181mm long
           

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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.

 

      Ormoceras sp., MCZ 129061            
     

MCZ 129061: 112mm long

           

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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.

 

      Arionoceras sp., MCZ 129258            
     
MCZ 129258: 91mm long
           

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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.

 

      Centroonoceras? sp., MCZ 129299            
     
MCZ 129299: 86mm long
           

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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.

 

      Clinoceras exiguum, MCZ 134023            
     
MCZ 134023: 36.5mm long
           

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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.


      Geisonoceras sp., MCZ 129897            
     
MCZ 129897: 46mm long
           

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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.


  Kionoceras sp., MCZ 130157 Kionoceras sp., MCZ 130150    
 
MCZ 130157: 45mm long
MCZ 130150: 133mm long
   

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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.

 

      Leurocycloceras sp., MCZ 130123            
     
MCZ 130123: 38.5mm long
           

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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.

 

      Michelinoceras sp., MCZ 130240            
     
MCZ 130240: 206mm long
           

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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.

 

      Murchinsoniceras sp., MCZ 130520            
     
MCZ 130520: 73.5mm long
           

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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.


      Orthoceras sp., MCZ 130974            
     
MCZ 130974: 73mm long
           

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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.

 

      Parakionoceras sp., MCZ 131051            
     
MCZ 131051: 118mm long
           

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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.

 

      Plagiostomoceras undet., MCZ 131065            
     
MCZ 131065: 78mm long
           

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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.

 

      Spyroceras sp., MCZ 131011            
     

MCZ 131011: 71.5mm long

           

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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.

 

      Eorizoceras sp., MCZ 132764            
     
MCZ 132764: 26mm long
           

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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.

 

      Maelonoceras? sp., MCZ 132790            
     
MCZ 132790: 107mm long
           

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Oocerina sp. Foerste, 1926 - Description from Sweet, 1964b

Description: Like Oonoceras, but siphuncular segments nummuloidal and actinosiphonate.

Ecology: Active swimmers and posthumous floaters.

 

      Oocerina sp., MCZ 132655            
     
MCZ 132655: 29mm wide
           

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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.

 

      Oonoceras sp., MCZ 132822            
     
MCZ 132822: 30mm long
           

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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.

 

      Oncoceras constrictum, MCZ 132641            
     
MCZ 132641: 37mm long
           

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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.

 

      Tripteroceras sp., MCZ 132870            
     
MCZ 132870: 305mm long
           

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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.

 

      Valcouroceras sp., MCZ 132911            
     

MCZ 132911: 109mm long

           

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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.

 

      Trocholites ammonius, MCZ 135171            
     

MCZ 135171: 38mm wide

           

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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.


      Lechritrochoceras sp., MCZ 135388            
     
MCZ 135388: 38mm wide
           

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