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

Abstract

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. Keywords Microconchids Á Spirorbis Á Muschelkalk Á Triassic Á Skeletal microstructure Á Germany Kurzfassung Die Zugehörigkeit der schraubenförmig gewickelten Röhren von Microconchus aberrans (Hohenstein, 1913) aus dem frühen Anisium von Süddeutschland zu den Microconchiden wird durch eine SEM-Analyse der Schalenstruktur bestätigt. Die Schale von M. aberrans weist wahrscheinlich Pseudopunktae auf. In der Trias zeigen schraubenförmige und einige planispiral am Substrat zementierte Microconchiden einander ähnliche mikrolamellare Röhrenstrukturen. Die Struktur des morphologisch abweichenden M. aberrans ist typisch für Microconchiden vom Paläozoikum bis zur mittleren Trias. Allochthone Röhrenfragmente von M. aberrans im Wellenkalk stammen vermutlich aus einem Microconchiden-Biostrom. Schlü sselwörter Microconchiden Á Spirorbis Á Muschelkalk Á Trias Á Schalen-Mikrostruktur Á Deutschland

Early Triassic benthic invertebrates from the Great Bank of Guizhou, South China: systematic palaeontology and palaeobiology

“…Morphology A represents broken helical tubes of the adult free tube parts that would have extended into the water column; whereas, the planispiral tubes (morphology B) that were observed to have been attached to shell material, represent the juvenile tube parts. It is likely that this is a consequence of these specimens coming from a high‐energy, shallow water marine environment, and this scenario has also been interpreted in other studies (Vinn ). In addition, morphology B is exclusively found in the rock matrix, and morphology A on shell material, supporting our interpretation.…”

Palaeoecology of microconchids from microbialites near the Permian–Triassic boundary in South China

“…Of the microconchids documented in the present study, Helicoconchus elongatus was first described from the Early Permian (Wilson et al . ), while the planispirally coiled form ( Microconchus utahensis ) persisted to the Anisian stage of the Middle Triassic (Stiller ; Vinn ). Consequently, microconchids survived the P–Tr biocrisis in microbialite ecosystems and flourished together with other metazoans during the Middle Triassic recovery and radiation (Chen & Benton ).…”

A new mound-building biota from the lower Carboniferous of Alabama

“…However, all but the smallest microconchids are at least several times greater in diameter than any specimens of Problematicum A, and they have much thicker walls. In addition to the size difference, microconchids tend to be either more uniform in diameter or conical; many bear both annulae and longitudinal striations; and spines, where present, tend to be relatively large, stout, and evenly spaced (Vinn and Mutvei, 2005; Taylor and Vinn, 2006; Zhan and Vinn, 2007; Taylor et al, 2010; Vinn, 2010; Vinn and Wilson, 2010; Wilson et al, 2010). The affinities of Problematicum A are unknown.…”