Diagnoza

Porównanie

It shows significant variation in the diagnostic curvature, most elements being laterally bent, symmetrical elements not being rare. The basal cavity is also variable in adult specimens being slightly swollen and Pseudopolygnathus-like. Generally, the basal cavity shows the morphology typical of Siphonodella, that is fusiform in shape, but a few very mature specimens are in this respect somewhat transitional to Pseudopolygnathus. The only co-occurring oz elements that could belong to the same apparatus are rather robust and variable in morphology. They tend to develop a narrow platform along the dorsal process that gives them a slightly 'notognathella' appearance. Singular recognised elements of the symmetry transition series show some resemblance to elements of the younger Pinacognathus sp. although they are not so specialized morphologically.

The type population of Polygnathus sulcata Huddle, 1934 comes from the upper New Albany Shale near its top just above gray-green shale containing Devonian brachiopods near Rockford, Indiana (Huddle 1934; Sandberg et aI.1972).

Autekologia

Występowanie geograficzne

Zasięg czasowy

early Tournaisian

Materiały muzealne

Literatura