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Atrypa

Classification

    Phylum:  
Brachiopoda
    Class:  
Rhynchonellata
    Order:  
Atrypida
    Superfamily:  
Atrypoidea
    Family:  
Atrypidae
    Formal Genus Name and Reference:  
Atrypa DALMAN, 1828, p. 127
    Type Species:  
Anomia reticularis LINNAEUS, 1758, p. 702, OD


Images

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Fig. 939 a–d. *A. (A.) reticularis (LINNAEUS), lower Ludlow, Gotland; a–c, dorsal, ventral, posterior views, ×2; d, SEM detail of macroornament, ×12 (new).——FIG. 940 a–d. *A. (A.) reticularis (L INNAEUS), lower Ludlow, Gotland; a–c, serial sections, ×4; d, reconstruction from serial sections, ×3.5 (new).


Synonyms



Geographic Distribution

worldwide


Age Range

    Beginning Stage in Treatise Usage:  
Silurian (upper Llandovery)
    Beginning International Stage:  
Telychian
    Fraction Up In Beginning Stage:  
0
    Beginning Date:  
438.59
    Ending Stage in Treatise Usage:  
Middle Devonian (lower Givetian)
    Ending International Stage:  
Givetian
    Fraction Up In Ending Stage:  
35
    Ending Date:  
383.06


Description

medium to large, broadly convexoplane to dorsibiconvex adult shell, ventral valve from very weakly convex apically, dorsal valve usually strongly convex, area generally absent, beak adpressed, foramen transapical or obscured, deltidial plates absent, ribs medium to coarse, regular, concentric, undulose to wavelike growth lamellae, usually expanded as prominent, multiple frills, commissure rectimarginate to plicate, thick pedicle callist, teeth massive, with dental nuclei, accessory lobes (dental cavities in neanic shells), muscle field depressed, vascular ridges weakly to strongly developed around muscle areas, hinge socket plates strong, comblike cardinal process lining cardinal pit, sockets with accessory ridges, crural bases large, bulbous, crura commonly feathered, spiralia dorsal, up to 20 whorls in large shells, jugal processes thick, terminating in long, dorsally directed spatulate jugal plates, differs from ancestral Gotatrypa in convexoplane shell, development of frills, from Atryparia in more imbricate ribs, lack of dental nuclei in adult teeth




References



Museum or Author Information