Spirotrypidae, A new family of Permian Bryozoans from the Wargal Limestone, Salt Range, Pakistan
Keywords:
Keywords: Bryozoa, Wargal Limestone, Capitanian-Wuchiapingian-Changhsingian, Salt Range, Pakistan, Permian.Abstract
Spirotrypidae, a new family of Rhabdomesida containing seven new genera and species, occurs in the Wargal Limestone (Permian) of the Salt Range in northcentral Pakistan. Based on conodonts, the age of this family ranges from Capitanian to earliest Changhsingian. The Wargal Limestone is considered to have been deposited on a shallow carbonate platform under normal marine conditions.
The small size of these bryozoans presents a challenge for their identification by normal methods of study of stenolaemate bryozoans (transverse, tangential, and longitudinal sections). It was necessary to prepare serial acetate peels of transverse sections of zoaria and produce tangential and longitudinal sections from these transverse sections.
Critical for producing tangential and longitudinal views is the constant central tube in the center of these bryozoans. The central tube serves as a known point of reference for aligning the serial transverse sections. This central tube is unique in the absence of any internal structures such as diaphragms. The tube does not branch to form additional tubes or produce new autozooecia from within the tube. Other structures unique to these bryozoans is the presence of indented tabular nodes in two of the genera and hook-shaped spines in two of the genera.
The seven new genera are classified by the type of autozooecial budding in the zoaria. The type of budding can be identified by examining the transverse sections. The new genera and species are Didymotrypa multistylia, Tritrypa indentura, Tetratrypa hookia, Pentatrypa tabularia, Hexatrypa nammalia, Heptatrypa spinosa, and Spirotrypa spiralia.
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