Class Bivalvia
 
   
                       
                                           
 
                                           
                             
   

SUBCLASS PALAEOTAXODONTA

SUBCLASS ISOFILIBRANCHIA

SUBCLASS HETEROCONCHIA

SUBCLASS ANOMALODESMATA

SUBCLASS PTERIOMORPHIA

 
   
-Species Descriptions-
 
   
SUBCLASS PALAEOTAXODONTA
 

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    Ctenodonta nasuta (Hall) - Description from Pojeta, 1978. Ecology from Pojeta, 1971.

Description: Has a solemyiform shell that expands anteriorly. Shell has an enlarged anterior adductor scar and lacks concentric sculpture.

Ecology: Infaunal deposit feeders.

 
                           
           
MCZ 147559: 55 mm wide
               

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    Ctenodonta sp. Salter, 1852 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Has large elongate, equilateral shell that is curved so the beaks are opisthogyrate. Lacks a prominent internal septum and pallial sinus. The resilifer is absent.

Ecology: Infaunal deposit feeders.

 

 
      Ctenodonta sp., MCZ 143558 Ctenodonta sp., MCZ 143601      
     
MCZ 143558: 43mm wide
MCZ 143601: 48.5mm wide
     

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Deceptrix sp. Fuchs, 1919 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Similar to Praenucula, but teeth in the posterior tooth row are smaller and more numerous than those in the anterior tooth row.

Ecology: Infaunal deposit feeders. Shallowly buried with the anterior end approximately parallel to the sediment-water interface, and end is covered with a thin layer of sediment.

 

 
           
     
MCZ 147596: 15mm wide
MCZ 147600: 12mm wide
     

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    Nuculites sp. Conrad, 1841 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Shell elongate posteriorly, pallial sinus is present, and there is no resilifer present, the ligament is predominatedly external. Like Palaeoneilo, but has an internal septum that leaves a slit-like impression in molds.

Ecology: Infaunal burrowers.

 

 
            Nuculites sp., MCZ 143449                
           
MCZ 143449: 11mm wide
               

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    Palaeoneilo sp. Hall and Whitfield, 1869 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Shell elongate posteriorly, pallial sinus is present, and there is no resilifer present, the ligament is predominatedly external. There is a faint posterior radial groove, concentric shell sculpture, and internal septum is not present.

Ecology: Infaunal siphonate suspension feeders.

 

 
      Palaeoneilo sp., MCZ 143864 Palaeoneilo sp., MCZ 143936      
     
MCZ 143864: 15mm wide
MCZ 143936: 9.5mm wide
     

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Praenucula sp. Pfab, 1934 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Small shell size. Has an earlike extension of the dorsal region on the posterior of the shell (posteriorly auriculate) and it is anteriorly elongate. Teeth in the tooth rows anterior and posterior to the beaks are approximately the same size and number.

Ecology: Infaunal burrowers.

 

  Praenucula sp., MCZ 144006

MCZ 144006: 13mm wide

 


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SUBCLASS ISOFILIBRANCHIA

Cymatonota sp. Ulrich, 1893 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Has distinct soleniform shape with subparallel dorsal and ventral margins and it has both anterior and posterior shell gapes. Little is known about the hinge or pallial line or its musculature.

Ecology: Infaunal deep burrowers.

 

        Cymatonota sp., MCZ 144095              
       
MCZ 144095: 26mm wide
             

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Modiolopsis? sp. Hall, 1847 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Has a modioliform shell that expands noticeably posteriorly so that the maximum height of the shell is significantly more than the height measured down from the beaks. Modiolopsis also has concentric relief pattern on surface of shell, an entire pallial line, anisomyarian musculature, and multiple accessory muscle scars in front of the beaks.

Ecology: Most species have a semi-infaunal to infaunal mode of life, but some are epifaunal nestlers on bryozoan colonies.

 

        Modiolopsis? sp., MCZ 144422              
       

MCZ 144422: 20.5mm long

 

             

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SUBCLASS HETEROCONCHIA

Lyrodesma sp. Conrad, 1841 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Has prominent posterior lateral teeth and sockets which run the length of the posterior dorsal margin. In some species the posterior teeth are significantly longer than the other teeth. It also possesses a pallial sinus, which makes it the oldest known siphonate bivalve.

Ecology: Infaunal burrowers.

 

        Lyrodesma sp., MCZ 144554              
       

MCZ 144554: 8mm wide

 

             

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SUBCLASS ANOMALODESMATA

Cuneamya miamiensis Hall and Whitfield, 1875 - Description from Runnegar, 1974, Ecology from Pojeta, 1971.

Cuneamya miamiensis Hall and Whitefield, 1875. Runnegar, 1974, p. 931, pl. 2, fig. 1-3.

Description: Has an elongate shell with an obvious lateral sulcus and a deep lunule bounded by an angular carina. A second shallow sulcus occurs behind the edge of the lunule. There are also no shell gapes. Other Ordovician species lack the second sulcus and have a less well-defined lunule.

Ecology: Infaunal burrowers.

 

        Cuneamya miamiensis, MCZ 113853              
       
MCZ 113853: Hypotype, 44.5mm wide
             

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Cuneamya? sp. Hall and Whitfield, 1875 - Description from Runnegar, 1974. Ecology from Pojeta, 1971.

Description: Has an elongate shell with a broad lateral sulcus and a well-developed lunule. Anterior surface has concentric ornamentation. Strongly incurved beaks truncate the posterior margin and the posterior slope is smooth with no marginal gap.

Ecology: Infaunal burrowers.

 

        Cuneamya? sp., MCZ 144658              
       

MCZ 144658: 22.5mm wide

             

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SUBCLASS PTERIOMORPHIA

Ambonychiopsis sp. Isberg, 1934 - Description from Pojeta, 1966. Ecology from Pojeta, 1971.

Description: The shell is equivalved and inequilateral, with an anterior lobe. Beaks are nonterminal and prosogyral. Have a surface ornament of fine simple costellae crossed by concentric growth lines and often by concentric undulations. Shell gapes are absent and the posterior adductor muscle scar present.

Ecology: Epifaunal, byssally attached suspension feeders.

 

     
   
MCZ 145736: 72mm long
 
MCZ 145737: 28mm long

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Caritodens sp. Foerste, 1910Description from Cox et al., 1969. Ecology from Pojeta, 1971.

Description: Shell is upright suborbicular without radial ornamentation and possessing a well developed rounded auricle and a well-defined posterior wing.

Ecology: Epifaunal suspension feeders that lie free on one valve on the seafloor.

 

        Caritodens sp., MCZ 145742              
       
MCZ 145742: 9mm wide
             

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Cyrtodonta sp. Billings, 1858 - Description from Pojeta, 1971. Ecology from Pojeta, 1971.

Description: Has prominent duplivincular ligament, is equivalved, and has a well-developed dentition of cardinal and posterior lateral teeth. Shows a great deal of variation in the number, position, shape, and direction of growth of the cardinal teeth. The posterior lateral teeth are all confined to the posterior end of the hinge area, never cross the ligament area, and never reach the beaks.

Ecology: Infaunal shallow burrowers.


        Cyrtodonta? sp., MCZ 145741              
       
MCZ 145741: 15mm long
             

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“Limid” - Description from Cox et al., 1969. Ecology from Pojeta, 1971.

Description: Shell usually equivalved and shaped like longitudinal section of egg (most commonly higher than long). Many forms extend obliquely in anteroventral direction (opisthocline). Typically have 2 auricles , but with anterior auricle reduced or absent. Has triangular cardinal area with shallow triangular ligament pit present in both valves. Beaks are well-separated and shell gapes present (anterior and posterior). Shell surface is smooth with radial ornament.

Ecology: Epifaunal.

 

  Limid, MCZ 145738 Limid, MCZ 145739    
MCZ 145738: 21mm long
MCZ 145739: 44mm long

                                   
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