Systematic position of two Early Devonian sinistral heterostrophic gastropods from the Garra Limestone, New South Wales

The term shell heterostrophy describes the condition where the shell whorls coil in one direction during one portion of a gastropod's life, and in the other direction for another portion. In the present paper, the oldest evidence of non-coaxial shell heterostrophy in the Class Gastropoda is documented in the new species Koneprusellia zaki sp. nov. (Porcellioidea, Archaeogastropoda), coming from the Early Devonian of the Barrandian area (Bohemia). A brief analysis of the occurrences of this shell's morphological features, among the Paleozoic gastropods, revealed that the shell heterostrophy was present in at least three unrelated gastropod lineages: in the clades Heterobranchia (Devonian-Recent), Macluritoidea (Ordovician), and Porcellioidea (Silurian-Cretaceous).•

Section: Genus Koneprusellia Frýda 1998mentioning

confidence: 99%

Section: Jiøí Frýda and Lenka Ferrová The Oldest Evidence Of Non-coaxiamentioning

confidence: 99%

Section: B C B a C Amentioning

confidence: 99%

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The oldest evidence of non-coaxial shell heterostrophy in the Class Gastropoda

Frýda¹,

Ferrová²

2011

“…Conti & Monari (2001) discussed the history of the taxonomy of Eucyclus and the genera considered to be related to it. Hickman & McLean (1990) included in the Eucyclinae Koken, 1897 the genera Amberleya, Eucyclus, Eunemopsis, Eucyclomphalus, Cirrus Sowerby 1815, and Hamusina Gemmellaro, 1879, the last two of which belong to quite different groups of the Vetigastropoda, the Cirridae Cossmann, 1916 which belong to the Porcellioidea Koken, 1895 (Bandel 1988;Bandel & Frýda 1998Frýda 1997;Frýda & Blodgett 1998Kiel & Frýda 2004;Frýda & Farrell 2005;Frýda et al 2006Frýda et al , 2008. The tribes Calliotropini and Chilodontini were included into the Eucyclinae with species that occur world-wide.…”

Section: Genus Pseudoclanculus Cossmann 1918mentioning

confidence: 99%

Relationships of the Triassic Eucycloidea Koken, 1897 (Mollusca, Gastropoda) to modern genera such as Pagodatrochus, Calliotropis and Euchelus, based on morphology of the early shell

Bändel¹

2010

The aim of this study is to document the relationship that may exist between Triassic species of Eucycloscala, Ampezzotrochus, Sabrinella, Microcheilus, Eunemopsis and Pseudoclanculus and living species of genera such as Pagodatrochus, Turcica, Calliotropis, Danilia, and Euchelus. Their shell has a nacreous inner layer and ornament of axial ribs on the early teleoconch. This ornament distinguishes from living and fossil Vetigastropoda with Trochus, and Turbo-like shells. Eucycloscalidae, containing the Triassic genera Eucycloscala and Ampezzotrochus, can be distinguished from Eunemopsis and Pseudoclanculus and the Eunemopsidae fam. nov. by folds on the inner lip and Sabrinellidae fam. nov. with Sabrinella and Microcheilus by the varix of the aperture of the last whorl. Lanascala with Lanascalidae belongs here. Neoeunema gen. nov. represents a Triassic member of Eucyclidae, which contains numerous Jurassic genera and species. Pseudoturcicidae fam. nov. differs by the ornament of the early teleoconch. The Chilodontidae form a characteristic Cretaceous group with teeth on the inner side of their outer lip. Three families of modern genera can be distinguished by the arrangement of teeth in the radula: four pairs in Pagodatrochidae fam. nov. and Turcicidae fam. nov., and three pairs in Calliotropidae, documented with Euchelus. The Seguenzioidea represents a related group having a distinctive radula with two lateral pairs of teeth and a variety of shell shapes and ornament. The early teleoconch of Seguenziidae (with slit in the aperture) and Ancistrobasidae fam. nov. (without such a slit) resembles that of the Eucycloscalidae, but has a strong spiral rib in addition to the axial ribs. The new species Microcheilus maxwelli sp. nov., Eucycloidea madagascariensis sp. nov., new genera Pseudoturcica and Heterodiscohelix, and new families Sabrinellidae fam. nov., Euemopsidae fam. nov., Pseudoturcidae fam. nov., Pagodatrochidae fam. nov. Turcicidae fam. nov., and Ancistrobasidae fam. nov. are introduced. The fossil record confirms existence of two independent branches of Vetigastropoda since more than 220 Ma, and within one of these branches parallel to the Eucycloidea the Seguenzioidea since Mesozoic times

“…During the last few decades muscle scars were documented in another bilaterallycoiled molluscan group, the Porcellioidea (Peel 1986). The latter belongs to gastropods having a nacreous shell and represents an extinct lineage of archaeogastropods originating in the Silurian and becoming extinct in the Cretaceous (Frýda 1997;Frýda & Blodgett 1998, 2004Kiel & Frýda 2004;Frýda & Farrell 2005). The muscle scars were also …”

Section: Muscle Scarsmentioning

confidence: 99%

Mode of life of Early Devonian Orthonychia protei (Neritimorpha, Gastropoda) inferred from its post-larval shell ontogeny and muscle scars

Frýda¹,

Rachebœuf²,

Frýdová³

2008

Rich fossil material of the Early Devonian Orthonychia protei (Oehlert, 1883) from the Saint Céneré Formation, Brittany (France) provides a unique chance to analyze the infraspecific variability of muscle scars and post-larval shell morphology. The position of the muscle scar in this species depends on the shape of the teleoconch, which seems to be influenced by its living position upon the crinoid host. Individuals having a teleoconch aperture with a pentagonal outline and five apertural processes probably lived on top of a crinoid calyx and their muscle was attached to the center of their teleoconchs. However, muscle scars are situated more laterally in individuals with irregular teleoconchs lacking apertural processes. The latter group was probably attached to another part of the crinoid body or even to another type of hard substrate. Juvenile post-larval Orthonychia protei was a mobile animal, but very early in its ontogeny became adapted to a fixed position on the crinoid body and remained immobile for the majority of its post-larval ontogeny. Long-term coexistence of Orthonychia protei with the same crinoid suggests that this species had a long-term advantage from such an ecological strategy. However, the existence of individuals with irregularly shaped teleoconchs suggests that Orthonychia protei could also live successfully outside of the digestive openings of crinoids and, thus, use a food source not closely connected with crinoids. This interpretation can be supported by the fact that at least some Silurian and Devonian platyceratids were adapted to living on small firm objects (like empty cephalopod shells) lying on the sediment surface.•