Shell structure of helically coiled microconchids from the Middle Triassic (Anisian) of Germany

摘要

Microconchid affinity of helically coiled tubes of Microconchus aberrans (Hohenstein, 1913) from the early Anisian of southern Germany is supported by an SEM study of shell structure. There are probable pseudopunctae in the shell of M. aberrans. Helically coiled and some substrate-cemented planispiral microconchids have similar microlamellar tube structures in the Triassic. The structure of the morphologically aberrant M. aberrans is characteristic of Palaeozoic to Middle Triassic microconchids. Allochthonous tube fragments of M. aberrans in the Wellenkalk presumably originate from a microconchid biostrome.