Devonian Gastropods Research Articles

Redescriptions of some Lower Devonian gastropods from Tennessee currently considered to be platyceratids

AbstractThree genera of gastropods described from the Lower Devonian Rockhouse Formation of Hardin County, Tennessee, currently are considered to be junior subjective synonyms ofPlatyceras(Visitator) Perner, 1911. Evaluation of the type specimens of these genera as well as types of two other gastropods from the same formation reveals the following:Platyostoma quadrangulare(Dunbar, 1920) is the only platyceratid gastropod among them;Saffordella tennessensisDunbar, 1920 has a selenizone above midwhorl so it is an eotomarioidean belonging to the Gosseletinidae;Aulopea nelsoniDunbar, 1920 and the lectotype ofDistemnostoma princepsDunbar, 1920 each has a broad subsutural sinus on the upper whorl surface similar to the Omphalotrochidae, as well as a basal sinus similar to certain primitive caenogastropods, so their systematic position is uncertain; I considerHolopea planidorsataDunbar, 1920 to be a juvenile specimen ofD. princeps; the fragmentary paralectotype ofD. princepspossibly represents a gerontic form ofDistemnostoma curtumDunbar, 1920, which possesses a well-developed selenizone on an upwardly projecting shoulder at the edge of the upper whorl surface. BecauseD. curtumappears to be unrelated toD. princeps, the genotype ofDistemnostoma, I propose the new generic nameOmocordellaforD. curtum. The new family Micromphalidae is erected to include OrdovicianSlehoferiaRohr and Fryda, 2001, lower CarboniferousMicromphalusKnight, 1945, andOmocordellan. gen.

New porcellioidean gastropods from early Devonian of Royal Creek area, Yukon Territory, Canada, with notes on their early phylogeny

This paper presents a description of new gastropods belonging to the superfamily Porcellioidea (Vetigastropoda) from the richly diverse Lower Devonian gastropod fauna of the Road River Formation in the Royal Creek area, Yukon Territory. This fauna belongs to Western Canada Province of the Old World Realm. The Pragian speciesPorcellia(Porcellia)yukonensisn. sp. andPorcellia(Paraporcellia) sp. represent the oldest presently known members of subgeneraPorcellia(Porcellia) andPorcellia(Paraporcellia). Their simple shell ornamentation fits well with an earlier described evolutionary trend in shell morphology of the Porcellinae. Late Pragian to early EmsianPerryconcha pulchran. gen. and n. sp. is the first member of the Porcellioidea bearing a row of tremata on adult teleoconch whorls. The occurrence of this shell feature in the Porcellioidea is additional evidence that the evolution of the apertural slit was much more complicated than has been proposed in classical models of Paleozoic gastropod evolution.

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

Two Early Devonian gastropod genera, Garraspira gen. nov. and Anoriostoma from the GarraLimestone, with sinistrally heterostrophic shells, share several shell features and are placed in the new tribe Anoriostomatini within the subfamily Agnesiinae. In contrast to the other members of the latter subfamily these genera represent a lineage in which the apertural slit was lost during evolution. This fact supports the opinion that the presence or absence of the apertural slit does not necessarily have significance for high-level taxonomy. Morphology of the gerontic whorl in Anoriostoma sinistra and Garraspira imtsitata suggests their limited mobility during the last ontogenetic stage.

Middle Devonian gastropods from Xiangzhou and Wuxuan, Guangxi, South China

Eighteen taxa of Middle Devonian (Givetian) gastropods, including two new genera and five new species, are présent in the Tungkangling and Yingtang Formations, Wuxuan and Xiangxhou counties, Guangxi Province, China. Pingtianispira tuberculata gen. et sp. nov., Wuxuanella nodusa gen. et sp. nov. and Wuxuanella luifengshanensis sp. nov., Crenulazone wuxuanensis sp. nov. and Murchisonia luifengshanensis sp. nov. are erected from this distinct fauna. The fauna is dominated by nodose and unusual murchisonioids and has strong European and other Old World realm affinities.

Early Devonian gastropods from Zhusilenghaierhan region, western inner Mongolia, China

Early Devonian (Emsian) gastropods from the Zhusileng Formation of Zhusilenghaierhan Region, West Inner Mongolia, China, consisting of 18 taxa, including Neimongolidiscus circumumbilicus new genus and species, Pseudopharkidonotus sinensis new genus and species, Nodulospira danmianshanensis new genus and species, Zhusilengospira turbiniformis new genus and species, Zhusilengospira compactum new genus and species, Taemasotrochus nodosa new species, and Scalaetrochus sinensis new species. Endemic forms dominate the fauna, which shows some genus level affinities with Eastern Australia, the Kitikami Mountains of Japan. The fauna does feature small numbers of cosmopolitan taxa.

New early Devonian gastropods from the families Crassimarginatidae (new family) and Scoliostomatidae (new family), Royal Creek Area, Yukon Territory, Canada

Two new distinctive families, Crassimarginatidae and Scoliostomatidae, each characterized by unusual gerontic apertural morphotypes, are established on the basis of study of the richly diverse Lower Devonian gastropod fauna of the Road River Formation in the Royal Creek area, Yukon Territory. The Early Devonian genusCrassimarginataJhaveri, 1969, is transferred from the family Palaeotrochidae and placed, together with the new genusYukonoconcha,into the new family Crassimarginatidae, which is characterized by a pupiform shell with an explanate outer apertural lip in the gerontic growth stage. The new family Scoliostomatidae unites Devonian gastropod genera (ScoliostomaBraun, 1838;BrilonellaKayser, 1873;AnarconchaHorný, 1964;Eoscoliostomanew genus;MitchelliaKoninck, 1877; andPseudomitchellianew genus), which are characterized by a distinctive, free, twisted (both outwards and backwards) gerontic final half whorl. More detailed morphological comparison of members of this family has allowed their division into two new subfamilies: the Scoliostomatinae and Mitchelliinae. New genera includeYukonoconcha, Eoscoliostoma,andPseudomitchellia.The former two genera are represented each by a single new species from Yukon Territory,Yukonoconcha pedderiandEoscoliostoma norrisi.The latter genus is represented by two species, the typePseudomitchellia bohemica(Perner) from the Koněprusy Limestone (Pragian) of the Czech Republic andPseudomitchellia macqueeninew species from Yukon Territory.

NEW EARLY DEVONIAN GASTROPODS FROM THE FAMILIES CRASSIMARGINATIDAE (NEW FAMILY) AND SCOLIOSTOMATIDAE (NEW FAMILY), ROYAL CREEK AREA, YUKON TERRITORY, CANADA

Two new distinctive families, Crassimarginatidae and Scoliostomatidae, each characterized by unusual gerontic apertural morphotypes, are established on the basis of study of the richly diverse Lower Devonian gastropod fauna of the Road River Formation in the Royal Creek area, Yukon Territory. The Early Devonian genus Crassimarginata Jhaveri, 1969, is transferred from the family Palaeotrochidae and placed, together with the new genus Yukonoconcha, into the new family Crassimarginatidae, which is characterized by a pupiform shell with an explanate outer apertural lip in the gerontic growth stage. The new family Scoliostomatidae unites Devonian gastropod genera (Scoliostoma Braun, 1838; Brilonella Kayser, 1873; Anarconcha Horný, 1964; Eoscoliostoma new genus; Mitchellia Koninck, 1877; and Pseudomitchellia new genus), which are characterized by a distinctive, free, twisted (both outwards and backwards) gerontic final half whorl. More detailed morphological comparison of members of this family has allowed their division into two new subfamilies: the Scoliostomatinae and Mitchelliinae. New genera include Yukonoconcha, Eoscoliostoma, and Pseudomitchellia. The former two genera are represented each by a single new species from Yukon Territory, Yukonoconcha pedderi and Eoscoliostoma norrisi. The latter genus is represented by two species, the type Pseudomitchellia bohemica (Perner) from the Koněprusy Limestone (Pragian) of the Czech Republic and Pseudomitchellia macqueeni new species from Yukon Territory.

Palaeobiogeography of Australian Devonian gastropods

Australian gastropod faunas of Devonian age have received comparatively little attention. The occurrences of key gastropod taxa in the Devonian of Australia are reviewed. High levels of endemism of species in the Early Devonian are overprinted by Old World affinities at the generic and familial levels. These affinities persist into the Givetian, where strong links are maintained with European taxa. Limited data are available for Lochkovian, Eifelian and all Late Devonian gastropod faunas, making assessment of their biogeography difficult. Platyceratids, although present throughout Australia, form a lesser element of the faunas here than in other Old World Realm regions during the Devonian.

Upper Middle Devonian (Givetian) gastropods from the Kersadiou Formation, Brittany, France

Gastropods are described for the first time from the Kersadiou Formation (middle Givetian) in the vicinity of Brest, Brittany, northwestern France. Twenty-three species of gastropods are recognized. New taxa include the new genera,Calvibembexia, Kersadiella, Breizospira, Finisterella, Parahormotomina, andNodoloxonema, represented by the new speciesCalvibembexia lethiersi, Kersadiella babini, Breizospira crozonensis, Finisterella tibidiensis, Parahormotomina sibertae, andNodoloxonema plusquelleci.Further new species include:Sinuitina(Sinuitina)morzadeci, Crenistriella armoricana, Patellilabia(Phragmosphaera)ponceti, Angyomphalus(Eoangyomphalus)weyanti, Eoplatyzona ongaroae, Murchisonia oehlerti, andHormotomina fiacrensis.The biogeographic affinities of the fauna show a strikingly unusual admixture of Eastern Americas Realm taxa such asHormotominaandCrenistriella.This suggests that during the middle Givetian, the Massif Armoricain (northwestern France) represented an area of Realm-boundary mixing between the Old World and Eastern Americas Realms, while older Devonian gastropod faunas of the Massif Armoricain are wholly of Old World Realm type.

New Silurian and Devonian gastropod genera of Bohemia

New Silurian and Devonian gastropod genera of Bohemia

Early and Middle Devonian gastropod biogeography

Abstract Early and Middle Devonian gastropods show biogeographic patterns remarkably similar to those of better studied faunal groups of this same interval, notably articulate brachiopods, rugose corals, and trilobites. Three biogeographic realms are recognized: Old World, Eastern Americas, and Malvinokaffric Realms. Gastropod diversity is highest in the Old World Realm and lowest in the Malvinokaffric Realm. The diversity patterns and the high degree of shell ornamentation suggest that the Old World Realm was generally warmer than the Eastern Americas Realm, and that both were considerably warmer than the cool temperate to cold polar waters of the Malvinokaffric Realm. The utility of gastropods for fine-scale delineation of biogeographic units is illustrated for the Eifelian of western North America. At least two subprovincial units (the Alaska-Yukon and Nevada subprovinces) can be recognized. Eifelian gastropods from interior and southeastern Alaska belong to a single unit (the Alaska-Yukon Subprovince), and are most closely related to coeval faunas of northwestern Canada, suggesting little displacement of most of Alaska's so-called 'suspect' terranes. Plotting the data on the Devonian palaeogeographic maps of Scotese results in several suggested emendations: (1) North America should be moved south by 10-20°; (2) Australia is too far south on the Emsian and Givetian reconstructions, it should be in a more palaeotropical position; and (3) Siberia is too far north, it too should also be placed in a palaeotropical position.

Lower Devonian Gastropoda from the Canadian Arctic Islands

Gastropods from Lochkovian (Lower Devonian) beds on Prince of Wales and Baillie-Hamilton Island, Canadian Arctic, compose a small but relatively diverse part of a brachiopod-dominated fauna. The fossils probably represent subtidal photic, and shallow subphotic zone environments. Seventeen species are described including six new species: Odontomaria linsleyi (an openly coiled septate species), Phanerotrema perryi, Gyronema thorsteinssoni, Cyclonema (Cyclonema) supralirata, Platyceras (Platyceras) daschi, and Subulites sinistralis. Based on the limited amount of previous work on Lower Devonian gastropods, the gastropod fauna appears to have Old World affinities, with genera such as Lytospira and Codonocheilus representing holdovers from the Silurian.