SYSTEMATIC PALEONTOLOGY 



Phylum BRACHIOPODA 



Class ARTICULATA 



Suborder Rhynchonelloidea Moore, 1952 



[nom. correct. Muir-Wood, 1955, p. 69 {ex Rhynchonellacea Moore, in Moore, 

 Lalicker and Fischer, 1952, p. 220) ] 



Superfamily Stenoscismatacea Oehlert, 1887 (1883) 



[nom. correct. Muir-Wood, 1955, p. 69 (pro Stenoscismacea Shrock and Twen- 

 hofel, 1953, p. 317; nom. transl. et correct, ex Stenoschismatinae Oehlert, 1887, 

 p. 1304)] [= Camerophoriacea Waagen, 1883 (nom. transl. Grabau, 1936, p. 70 

 ex Camerophoriinae Waagen, 1883, p. 435) ] 



Family ATRIBONIIDAE Grant n. fam. 



Stenoscismatacea without stolidium, ranging from Middle Devonian 

 through Permian without clear evolutionary trends except general in- 

 crease in size ; costae absent, weak, or fine, not strong. 



Subfamily ATRIBONIINAE Grant n. subfam. 



Atriboniidae with intercamarophorial plate strong, extending an- 

 teriorly beyond undivided hinge plate. 



Genus ATRIBONIUM Grant n. gen. 



(A, Gr., without; tribonion, Gr., cloak) 



Shell about average size for family, flatly to strongly biconvex ; out- 

 line rotund, subtrigonal to subelliptical, normally widest anterior to 

 midlength ; anterior margin normally flat or slightly emarginate ; an- 

 terior commissure uniplicate ; fold rather low, broad, crest flat, stand- 

 ing only slightly above flanks, normally with several low plications ; 

 sulcus shallow, beginning 5-10 mm. anterior to pedicle beak, trough 

 flattened, depressed only slightly at anterior just behind strong flexure 

 around anterior margin ; flanks with costae beginning about 5 mm. 

 anterior to beaks, number on each side about equal to number on fold ; 

 posterolateral commissure with only narrow overlap of valves ; valve 

 edges slightly protruding around anterior of some species, not ex- 

 tended to form stolidium ; growth lines fine, closely spaced, stronger 

 growth laminae rare ; radial ornamentation consisting of fine, fibrous 

 shell substance. 



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