The Cambrian molluscs of Australia: overview of taxonomy, biostratigraphy and paleobiogeography

Abstract

Cambrian malacofauna of Australia is among the most taxonomically diverse among time equivalents. By a number of valid mollusc species Australian Cambrian competes with Siberian and Chinese formations. Up to date, 80 valid species and 12 forms in open nomenclature, apparently representing new undescribed taxa, have been recorded from the Lower–Middle Cambrian successions of Australia. In addition, 6 species names can be considered as junior synonyms. Distribution ranges of mollusc species plotted over the modern stratigraphic scheme reveal four major molluscan evolutionary assemblages in the interval of Tommotian–Undillan stages. In paleogeographic aspect, the Cambrian malacofauna of Australia has 29 species in common with Siberian Platform, Kazakhstan, Altai-Sayan, Transbaikalia, Mongolia, South and North China, Morocco, Antarctic, Europe (Denmark, Germany), Greenland, North America, and New Zealand, providing important correlation links between these regional stratigraphic schemes.

Mollusks from the upper Shackleton Limestone (Cambrian Series 2), Central Transantarctic Mountains, East Antarctica

“…Parkhaev in Gravestock et al (2001) and Parkhaev (2002, 2007a) placed Xinjispira with the family Khairkhaniidae Missarzhevsky, 1989. The use of the family Khairkaniidae as defined in Parkhaev in Gravestock et al (2001) and Parkhaev (2002) is not used here due to issues regarding the inclusion of symmetric ( Protowenella ) and asymmetric (e.g., Xinjispira, Barskovia Golubev, 1976) forms, under the assumption that they form a phylogenetic series. As no formal phylogenetic analysis has been performed to support this hypothesis, Xinjispira is tentatively included here with the pelagiellids.…”

An Eocene conger eel (Teleostei, Anguilliformes) from the Lillebælt Clay Formation, Denmark

“…In contrast, most specimens of Costipelagiella from the Henson Gletscher Formation have a flattened upper whorl surface and more angular periphery, although both features are variable. Peel et 2001a (Parkhaev 2001a(Parkhaev , 2002Bouchet et al 2017, p. 368, footnote 6) and placed within Order Helcionelliformes. Parkhaev (2002) gave a detailed and valuable overview of the families and their included genera that he placed within Order Helcionelliformes (gastropod Class Archaeobranchia).…”

“…Parkhaev (2002) described muscle attachment scars on the supra-apical surface of Bemella Missarzhevsky in Rozanov & Missarzhevsky, 1966 and on the sub-apical surface of Anhuiconus microtuberus Zhou & Xiao, 1984, but these are low shells that expand rapidly in the direction of growth without sub-apical ridges. Li et al (2021) described well preserved muscle scars in Figurina figurina Parkhaev, 2001a, which also has a low shell. Vendrasco et al (2010) described a pair of muscle scars near the apex on the supra-apical surface of Yochelcionella snorkorum Vendrasco, Porter, Kouchinsky, Li & Fernandez, 2010 from the Miaolingian Gowers Formation of Australia, which is a tall shell but also lacks the ridges on the sub-apical surface.…”

“…Later versions were given by Bouchet et al (2017) and Parkhaev (2019). Despite differences in the naming, content and placement of constituent families, most core genera are common to Eomonoplacophora sensu Missarzhevsky (1989), Helcionelloida (Peel, 1991a, b) and Helcionelliformes sensu Parkhaev (2001aParkhaev ( , 2002.…”

“…'Planospiral' is thus not synonymous in the usage of Parkhaev & Demidenko (2010) with the widely used 'planispiral' that means a shell coiled within a single plane, irrespective of the number of whorls (Knight et al 1960, p. I132, see also Parkhaev 2000Parkhaev , 2001a. Such planispiral shells are not necessarily bilaterally symmetrical about that plane, but if so, they are described as isostrophic.…”