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The evolution of conch ontogeny in Meszoic open sea gastropods

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Andrzej Kaim at Institute of Paleobiology, Polish Academy of Sciences
Andrzej Kaim
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Data on embryonic, larval, and postlarval morphology of the gastropod conchs from the Mid Jurassic to Early Cretaceous black clays from Poland are used to improve their taxonomy. The phylogenetic relationships of the fossil gastropod taxa to their Recent relatives are traced. The results show that most of the Recent groups were already present in the Mid Jurassic. The vetigastropods are apparently conservative and shells of some groups have not changed significantly for at least 160 Ma. The most primitive extant caenogastropods (e.g., Cerithioidea and Ampullospiridae) most probably have originated from the branches which diverged already in the Late Paleozoic. The other caenogastropods have undergone significant radiation in the Triassic. Then the Caenogastropoda had a period of relative stagnation. The significant exception is emergence and rapid radiation of Neogastropoda during the Cretaceous. The most diversified Mesozoic family of Heterostropha, the Mathildidae, had its acme from the Late Triassic to the Early Cretaceous. Later the family gradually declines and nowadays it is a relic group. The oldest cephalaspidean opisthobranchians are known since the Early Triassic but the significant radiation has taken place in the Mid Jurassic. The siphonariids, the marine pulmonates, are recognized from the Early Cretaceous. 135 species (54 of them new) and two new genera (Dzikella and Gnaszynium) are described.
Possible relationship of Recent and fossil vetigastropods with semiplanispiral shells. Note close resemblance of fossil and Recent Eudaronia. The Discohelix is more similar to Delphinula than to Eudaronia. A. Eudaronia jaffaensis (Verco, 1909), Re− cent, North Atlantic (courtesy of A. Warén); A 1 apical view, A 2 lateral view. B. Eudaronia pusilla (Gründel, 2000), ZPAL Ga. 9/104 from Łuków (block in glacial drift), Podlasie, Poland, Callovian (Mid Jurassic); B 1 apical view, B 2 lateral view, B 3 close−up of the protoconch, B 4 details of lateral surface ornamentation consists of growth lines and fine pustules. C. Eudaronia pusilla (Gründel, 2000), ZPAL Ga. 9/103 from Faustianka, Częstochowa region, Bathonian (Mid Jurassic), latero−apical view. D. Angaria evoluta (Reeve, 1843), Recent, Indo−Pacific (courtesy of A. Warén); D 1 lateral view, D 2 apical view. E. Discohelix calculiformis Dunker, 1847, Late Triassic of Germany (courtesy of A. Warén); E 1 lateral view, E 2 apical view.
Possible relationship of Recent and fossil vetigastropods with semiplanispiral shells. Note close resemblance of fossil and Recent Eudaronia. The Discohelix is more similar to Delphinula than to Eudaronia. A. Eudaronia jaffaensis (Verco, 1909), Re− cent, North Atlantic (courtesy of A. Warén); A 1 apical view, A 2 lateral view. B. Eudaronia pusilla (Gründel, 2000), ZPAL Ga. 9/104 from Łuków (block in glacial drift), Podlasie, Poland, Callovian (Mid Jurassic); B 1 apical view, B 2 lateral view, B 3 close−up of the protoconch, B 4 details of lateral surface ornamentation consists of growth lines and fine pustules. C. Eudaronia pusilla (Gründel, 2000), ZPAL Ga. 9/103 from Faustianka, Częstochowa region, Bathonian (Mid Jurassic), latero−apical view. D. Angaria evoluta (Reeve, 1843), Recent, Indo−Pacific (courtesy of A. Warén); D 1 lateral view, D 2 apical view. E. Discohelix calculiformis Dunker, 1847, Late Triassic of Germany (courtesy of A. Warén); E 1 lateral view, E 2 apical view.
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The skeneids Aequispirella jurassica sp. n., Adeuomphalus bandeli (Schröder, 1995), and their Recent counterparts. A. Aequispirella jurassica sp. n., ZPAL Ga. 9/107 (holotype) from Łuków (block in glacial drift), Podlasie, Poland, Callovian, Mid Jurassic); A 1 close−up of the protoconch, A 2 lateral view of the protoconch, A 3 details of teleoconch ornamentation, A 4 lat− eral view, A 5 apical view. B. Aequispirella corulum (Hutton, 1885), Recent, of New Zealand (courtesy of A. Warén); B 1 apical view, B 2 lateral view. C, D. Adeuomphalus bandeli (Schröder, 1995). C. ZPAL Ga. 9/105 from sample B1 of Wąwał, souther Mazowsze, Valanginian (Early Cretaceous); C 1 apical view, C 2 lateral view, C 3 close−up of the protoconch, C 4 details of teleoconch ornamentation. D. ZPAL Ga. 9/106 from sample E1 apical view. E. Adeuomphalus ammoniformis Seguenza, 1876, Recent, Mediterranean (courtesy of A. Warén); E 1 apical view, E 2 lateral view.
The skeneids Aequispirella jurassica sp. n., Adeuomphalus bandeli (Schröder, 1995), and their Recent counterparts. A. Aequispirella jurassica sp. n., ZPAL Ga. 9/107 (holotype) from Łuków (block in glacial drift), Podlasie, Poland, Callovian, Mid Jurassic); A 1 close−up of the protoconch, A 2 lateral view of the protoconch, A 3 details of teleoconch ornamentation, A 4 lat− eral view, A 5 apical view. B. Aequispirella corulum (Hutton, 1885), Recent, of New Zealand (courtesy of A. Warén); B 1 apical view, B 2 lateral view. C, D. Adeuomphalus bandeli (Schröder, 1995). C. ZPAL Ga. 9/105 from sample B1 of Wąwał, souther Mazowsze, Valanginian (Early Cretaceous); C 1 apical view, C 2 lateral view, C 3 close−up of the protoconch, C 4 details of teleoconch ornamentation. D. ZPAL Ga. 9/106 from sample E1 apical view. E. Adeuomphalus ammoniformis Seguenza, 1876, Recent, Mediterranean (courtesy of A. Warén); E 1 apical view, E 2 lateral view.
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Fossil and Recent turbinids. Note characteristically flattened early whorls. A, B. Torallochus lukovensis sp. n., ZPAL Ga. 9/108 (holotype; A) and 9/110 (B) from Łuków (block in glacial drift), Podlasie, Poland, Callovian (Mid Jurassic); A 1 lateral view, A 2 details of juvenile whorls, A 3 apical view, A 4 umbilical view; B 1 lateral view, B 2 close−up of the protoconch. C. Torallochus faustiankensis sp. n., ZPAL Ga. 9/112 (holotype) from Faustianka, Częstochowa region, Bathonian (Mid Juras− sic); C 1 lateral view, C 2 , C 3 details of juvenile whorls, C 4 apical view, C 5 umbilical view, C 6 close−up of the protoconch. D. Un− named turbinid from off of New Caledonia, Recent (courtesy of A. Warén).
Fossil and Recent turbinids. Note characteristically flattened early whorls. A, B. Torallochus lukovensis sp. n., ZPAL Ga. 9/108 (holotype; A) and 9/110 (B) from Łuków (block in glacial drift), Podlasie, Poland, Callovian (Mid Jurassic); A 1 lateral view, A 2 details of juvenile whorls, A 3 apical view, A 4 umbilical view; B 1 lateral view, B 2 close−up of the protoconch. C. Torallochus faustiankensis sp. n., ZPAL Ga. 9/112 (holotype) from Faustianka, Częstochowa region, Bathonian (Mid Juras− sic); C 1 lateral view, C 2 , C 3 details of juvenile whorls, C 4 apical view, C 5 umbilical view, C 6 close−up of the protoconch. D. Un− named turbinid from off of New Caledonia, Recent (courtesy of A. Warén).
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The eucyclinid Eucycloscala izabellae sp. n. from Faustianka, Częstochowa region, Bathonian (Mid Jurassic). A. ZPAL Ga.9/214 (holotype); A 1 lateral view, A 2 apical view, A 3 , A 4 details of juvenile whorls, A 5 close−up of the protoconch.
The eucyclinid Eucycloscala izabellae sp. n. from Faustianka, Częstochowa region, Bathonian (Mid Jurassic). A. ZPAL Ga.9/214 (holotype); A 1 lateral view, A 2 apical view, A 3 , A 4 details of juvenile whorls, A 5 close−up of the protoconch.
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Fossil eucyclinids and Recent juvenile liottid. Note the different shape and sculpture, especially the densely packed, band−like axial ribs of the liottid. A, B. Eucycloscala sp. 1, ZPAL Ga. 9/113 from Łuków (block in glacial drift), Podlasie, Po− land, Callovian (Mid Jurassic); A 1 lateral view, A 2 apical view, A 3, A 4 details of juvenile whorls, A 5 close−up of the protoconch. B. Eucycloscala sp. 2, ZPAL Ga. 9/114 from Łuków (block in glacial drift), Podlasie, Poland, Callovian (Mid Jurassic); B 1 lat− eral view, B 2 apical view, B 3 , B 4 details of juvenile whorls, B 5 close−up of the protoconch. C. Juvenile liottid, Recent, Swan Reef, off of Australia (courtesy of A. Warén).
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Fossil eucyclinids and Recent juvenile liottid. Note the different shape and sculpture, especially the densely packed, band−like axial ribs of the liottid. A, B. Eucycloscala sp. 1, ZPAL Ga. 9/113 from Łuków (block in glacial drift), Podlasie, Po− land, Callovian (Mid Jurassic); A 1 lateral view, A 2 apical view, A 3, A 4 details of juvenile whorls, A 5 close−up of the protoconch. B. Eucycloscala sp. 2, ZPAL Ga. 9/114 from Łuków (block in glacial drift), Podlasie, Poland, Callovian (Mid Jurassic); B 1 lat− eral view, B 2 apical view, B 3 , B 4 details of juvenile whorls, B 5 close−up of the protoconch. C. Juvenile liottid, Recent, Swan Reef, off of Australia (courtesy of A. Warén).
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... Remarks. The only other Triassic species attributed to this genus, otherwise known from the Upper Jurassic to the Upper Cretaceous (Wenz 1940;Kaim 2004), is Diatrypesis newelli N€ utzel & Erwin, 2004 from the Norian of North America. Triassic forms share with the type species the flat whorls, the adapical part of whorls notched or ornamented with adsutural row of nodes, the subordinate spiral ornamentation and the quadrate peristome. ...
... that separates the two fossil records, a different genus could be erected for the Triassic species. Kaim (2004) places Diatrypesis in Superfamily Cerithioidea F errusac, 1822. It is here included in subfamily Andangulariinae N€ utzel & Erwin, 2004, with Andangularia Haas, 1953and Silberlingella Fr yda & Blodgett, 2003, and treated as a subfamily of Zygopleuridae (Sorbeoconcha). ...
... Among the microcarnivores, the Pleurotomariida decreased in diversity across the Ladinian-Carnian boundary (Karapunar & N€ utzel 2021). Similarly to the Neritopsoidea, the Pleurotomariida have also vanished from shallow marine ecosystems, surviving only at bathyal depths (Harasewych 2002;Harasewych et al. 2023), a general trend shared by basal heterobranchs of family Mathilididae, decreasing in diversity during the Cenozoic (Kaim 2004). Today mathildids are largely confined to deep-water coral thickets (Smriglio et al. 2007;Negri & Corselli 2016) and their diversity is lower with respect to derived caenogastropod and heterobranch clades in modern tropical shallow seas (Bouchet et al. 2002;Wells et al. 2021). ...
A Middle Triassic Cassian-type fauna (Pelsa-Vazzoler Lagerstätte) and the adaptive radiation of the Modern Evolutionary Fauna
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  • Aug 2024
We describe a high-diversity silicified assemblage of marine molluscs (Pelsa-Vazzoler Lagerstätte) from the upper Ladinian of the Agordo Dolomites (northeastern Italy). New data on the Triassic rebound, after the end-Permian mass extinction, constrain it to an interval of relatively stable climatic conditions. This Lagerstätte, in the Sciliar Formation, yields a structure comparable to the famous lower Carnian San Cassiano Lagerstätte and suggests that the radiation of benthic molluscs may have occurred as early as the late Middle Triassic. We classified more than 4800 Cassian-type molluscs, measuring abundance distributions of 109 species, including one new family (Rhaetidiidae), three new genera (Pelsia, Gaetania, Agordozyga) and 21 new species: Grammatodon egortinus, Modiolus friesenbichlerae, Myoconcha busattae, Schizogonium letiziae, Predazzella? monarii, Eucycloscala nitida, Tricolnaticopsis elongatus, Cortinella stricta, Triadoskenea alpicornu, Trachynerita tenuicostata, Coelostylina civettae, Gaetania coronata, Agordozyga caprina, Euthystylus dincae, Zygopleura elongata, Diatrypesis agordina, Cryptaulax pelsae, Pseudoscalites karapunari, Promathildia gracile, Camponaxis ladinica and Striactaeonina ingens. In this fauna, associated with tropical carbonate platforms, epifaunal filter-feeding bivalves adopted new antipredatory features and gastropods conquered new ecospace, including parasitism and microcarnivory on sponges and scleractinian corals. Small size was an advantage in an ecosystem of small, isolated patch reefs. This is how, where and when caenogastropod and heterobranch snails (groups that today dominate global marine diversity) began their rise in the marine benthos. The origins of some evolutionary innovations that are key to our understanding of the time and place of the Mesozoic Marine Revolution, are therefore pushed back to the Middle Triassic.
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... The oldest fossil record of microphagous littorinimorphs dates back to the Middle Jurassic (Rissoidae [107,108]) or is even more recent (e.g., Caecidae, in the Eocene [109]; Hydrobiidae, in the Palaeocene [110]). ...
... Of the two extant families containing only ectoparasites, the Pyramidellidae (Heterobranchia) were first recorded in the Middle Jurassic [108] (see [41] for a possibly more recent origin), while the Eulimidae (Littorinimorpha) were first found in the Late Cretaceous [122,123]. Convergence in size and form has been noted with Triassic Zygopleuridae, Permian Pseudozygopleuridae, and Devonian Donalidinidae [41] (Figure 2). ...
The Revolution of Small Snails and the Early Modern Evolutionary Fauna
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The species richness of major clades and functional groups among gastropods, a key element of Modern Evolutionary Fauna (MEF), underlines the dominant role of carnivorous Caenogastropoda and Heterobranchia, including small ectoparasites and micrograzers, at modern tropical latitudes. Neogastropoda are active predators that radiated in the Cretaceous, but their early Mesozoic MEF roots are poorly understood. The escalation hypothesis emphasises prey–predator interactions as gastropods’ macroevolutionary drivers during the Mesozoic Marine Revolution but overlooks the significance of highly diversified smaller forms. The tropical fossil record of the Permian–Triassic mass extinction (PTME) and the Triassic rise of MEF suggests that non-carnivorous species dominated gastropod fauna immediately before and after the PTME: Permian micrograzers mainly fed on sponges and waned during the rise of MEF, while ectoparasites and micrograzing carnivores diversified starting from the Ladinian period. Patterns of gastropod species richness, size, and form, the fossil record of reef builders and other benthic invertebrates, and an analysis of stem neogastropods jointly suggest a Middle Triassic revolution of small-sized gastropods, triggered by the emergence of scleractinian corals and the diversification of echinoderms. Habitat heterogeneity and new food sources offered niches for the early radiation of modern gastropod clades.
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... The evolutionary relationship of fossil Pleurotomariida to other groups is inferred based on their characteristic shell features and in Recent taxa also on anatomy. The pleurotomariidan shell is characterized by a shell slit in the outer labrum, the presence of an inner nacreous layer, and a larval shell of one whorl matching the so-called trochoid condition and reflecting non-planktotrophic larval development (Bandel, 1982;Kaim, 2004;Geiger et al., 2008;N€ utzel, 2014). The slit reflects the soft body organization (Hickman, 1984). ...
... A few Palaeozoic gastropods with vetigastropod adult shell morphology and a protoconch reflecting larval planktotrophy have been reported (e.g. Dzik, 1978;Kaim, 2004), but it is under debate if those truly are members of Vetigastropoda (N€ utzel, 2014). Thus presence/absence of potential larval planktotrophy is not phylogenetically informative within Vetigastropoda. ...
Phylogeny of the longest existing gastropod clade (Pleurotomariida) reconstructed with Bayesian and parsimony methods and its implications on gastropod shell characters
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Full-text available
  • Sep 2024
Evolutionary relationships of fossil gastropods have largely been inferred using taxonomic systematics. Phylogenetic relationships between extinct gastropod groups and their relationship to extant groups are largely unresolved. Here we reconstruct the phylogeny of Pleurotomariida, which has the longest fossil record among extant gastropod clades and represents one of the most diverse Palaeozoic gastropod groups. Bayesian (fossilized birth–death [FBD] model) and parsimony analyses were performed using 93 morphological shell characters comprising 109 pleurotomariidan species representing 80 genera/subgenera ranging from the Ordovician to Recent. Parsimony analysis failed to reconstruct stratigraphically congruent trees and many nodes have poor support. The FBD model incorporates the stratigraphical ages of taxa for tree reconstruction and therefore better fits the stratigraphical record. According to the FBD phylogeny, Pleurotomariida was represented by three distinct lineages during the Palaeozoic: Eotomariini, Wortheniellini and Pleurotomariini. Pleurotomariini and Wortheniellini survived the end-Permian mass extinction. Although Wortheniellini showed a higher diversification during the Triassic recovery period, only Pleurotomariini survived until the present day, suggesting that resilience to extinction was not dependent on diversification dynamics in this clade. The FBD analysis indicates that groups that have an exclusively Triassic fossil record originated during the Permian and that the origination and extinction rates increased from the Ordovician to the Jurassic and dropped subsequently. Sampling standardized diversity analysis of Pleurotomariida corroborates that they were one of the most diverse gastropod groups in the late Palaeozoic and that their diversity significantly dropped after the end-Permian mass extinction. Early ontogenetic shell characters are more conservative (phylogenetically more informative) compared to late ontogenetic shell characters. In contrast to previous assumptions, axial characters are not more homoplastic than spiral shell characters, as indicated by higher consistency index values. The data further revealed that adult gastropod shell size depends significantly on the protoconch size and the initial whorl size.
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... Fully grown shell having thickened apertural margin. The aperture is rounded (after Bandel et al., 2000;Kaim, 2004). Gründel (2008) pointed out that the essential characters of the Ataphrus- Description. ...
... Later, Gründel & Nützel (2012 considered Sulcoactaeonidae as a synonym of Bullinidae. The diagnosis of the genus Sulcoactaeon was recently updated byKaim (2004),Kaim & Beisel (2005), andGründel & Nützel (2012). Representatives of this genus share a slender to broadly oval shell. ...
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  • Jan 2024
Systematic knowledge of Early and Middle Jurassic marine gastropods from Argentina has been supplied during the last decade through several contributions. The present paper describes a new marine gastropod fauna for the Jurassic of the Neuquén Basin, represented by four major taxa such as Patellogastropoda, Vetigastropoda, Caenogastropoda and Heterobranchia, including 14 new species of the genera Scurriopsis (Hennocquia), Eucyclus, Pleurotomaria, Laevitomaria, Obornella, Crossostoma, Palaeorissoina, Euconactaeon, Striactaeonina and Sulcoactaeon; members of Ambercyclus and Rhabdocolpus are also described from the studied area. Most of these taxa are first reported in the Jurassic of Argentina, extending their palaeobiogeographical distribution in South America at that time. Particularly, the genera Obornella, Palaeorissoina, and Euconactaeon also extend their chronostratigraphic distribution in the Jurassic marine deposits of the Neuquén Basin, from the late Hettangian (Palaeorissoina) and late Pliensbachian (Obornella) to the Aalenian–Bajocian (Euconactaeon). The new fossils described here expand the known diversity of the marine gastropod faunas in the Jurassic of Argentina and contribute to the paleontological knowledge of the group in the Mesozoic of the Southern Hemisphere.
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... The generic diversity remained relatively low before the Albian, but increased significantly during that stage and continued to grow until the end of the period. The oldest findings in the Early Cretaceous are extremely rare -only one fragment of juvenile shell has been identified in the Valanginian of Poland (Kaim 2004) and another complete specimen has recently been discovered in the Barremian of Bulgaria (Bakayeva & Kaim 2023). From the Aptian-Albian only one species has been recorded in Mexico (Allison 1955) and from the Albian of England two species are documented (Tracey 2010), whereas from the Albian of Madagascar fifteen species are described (Collignon 1949) being the most abundant Early Cretaceous neogastropod fauna to date. ...
Kimmeridgian ammonite fauna, biostratigraphy and palaeobiogeography of the Mecsek Mountains, Hungary
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Full-text available
  • Oct 2024
Kimmeridgian ammonite fauna, biostratigraphy and palaeobiogeography of the Mecsek Mountains, Hungary
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... However, a few diagnostic features could not be revealed, such as the inclination of growth line trajectory, sequence of appearance of spiral threads, protoconch and the shape of aperture (Marwick, 1957;Allmon, 1996). Further, only shell characters may not be adequate as diagnostic of supraspecific taxa in turritellids (Kaim, 2004). Hence, we place this form in Turritella sensu lato. ...
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... The latter, however, are usually more elongated and more finely ornamented. We are nonetheless somewhat hesitant with this assignment because similar shells occur also in members of Rissoidae (War en 1973;Gofas 1999) and some juvenile Aporrhaidae (Kaim 2004). ...
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We report a newly discovered hydrocarbon seep deposit from the Eocene bathyal flysch, exposed in the town of Buje in Istria, Croatia. Molecular fossils of methane‐oxidizing prokaryotes and abundant banded botryoidal cements indicate strong fluid flux at this site. We systematically describe the fauna of this and another seep deposit previously reported from Buje. The faunal assemblages are composed of eight species, these being an unidentified solemyid protobranch bivalve, the nuculid Nucula bowerbanki ?, the nuculanid Nuculana ? sp., the mytilid Brachidontes ? amanoi sp. nov., the two thyasirids Channelaxinus dinaricus sp. nov. and Thyasira histriaensis sp. nov., the lucinid bivalve Amanocina bujensis sp. nov., and a possible provannid gastropod. The two assemblages are of low diversity (4 and 5 species, respectively), and are dominated by chemosymbiotic species whose occurrence is largely restricted to seeps. Despite their spatial and stratigraphic proximity, the two deposits share only a single species, Channelaxinus dinaricus , probably due to different fluid flux regimes at both seeps. The Buje seep assemblages are among the very few Late Cretaceous to Palaeogene chemosynthesis‐based faunal assemblages from the Tethys Ocean (the others being Late Cretaceous vent assemblages from Cyprus). From an evolutionary perspective, the Buje seep communities consist of genera with Mesozoic origins but lack Cenozoic novelties such as bathymodiolin mussels and vesicomyid clams, which are known from coeval deposits from the Pacific and dominate vents and seeps today. Thus, the Buje seep fauna support previous assertions that the Eocene Tethyan seep faunas preserved an ancient aspect, whereas evolutionary novelties arose in the Pacific.
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Gastropods of the genus Sulcoactaeon Cossmann from the Barremian and Hauterivian Deposits of Ulyanovsk Volga Region (Russia)
Article
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Pleurotomariida (Gastropoda) from the upper Anisian platform carbonates of the Dolomites (Southern Alps, Italy): systematics, palaeobiogeography and Triassic recovery
Article
  • Mar 2024
The paper is open access at https://doi.org/10.1002/spp2.1545. A very rich gastropod fauna from the upper Anisian (Nevadites secedensis Zone) platform carbonates of the Dolomites, represented by more than 200 species, was collected over recent decades. Its study contributes to a better understanding of the dynamics of the recovery after the end-Permian mass extinction. This paper deals with the Pleurotomariida. A total of 35 species, 22 genera and 9 families have been identified. Of these, 12 species and 7 genera are new, namely Rufilla wilckensi sp. nov., Rufilla giacomellii sp. nov., Viezzenella ruvida gen. et sp. nov., Temnotropis maestroettorei sp. nov., Cancellotomaria boninsegnai sp. nov., Stuorella crenulata sp. nov., Codinella? fontanai sp. nov., Fiacconella pericincta gen. et sp. nov., Fiemmespira gen. nov., Texturaspira gen. nov., Nodocingulum ogilvieae sp. nov., Dimorphotomaria fassaensis gen. et sp. nov., Moenaspira crassa gen. et sp. nov. and Predazzella elongata gen. et sp. nov. Comparison with the gastropod fauna of the St Cassian Formation indicates that, from the late Anisian to the Carnian, in the Dolomites the richness of the Pleurotomariida increased by 54% at species level, 26% at genus level and 22% at family level. A comprehensive palaeobiogeographical analysis highlights a very high degree of endemism: 90% of the species are exclusive to single palaeogeographical units. This suggests that species diversification at a strict local scale was a major feature of the Middle Triassic phase of recovery of the Pleurotomariida. Seemingly, the non-planktotrophic development of this group combined with a patchy resurgence of the carbonate platforms played an important role in hampering dispersal.
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The Vetigastropoda (Mollusca) of Walters Shoal, with descriptions of two new genera and thirty new species
Article
Full-text available
  • Feb 2024
The vetigastropod material collected on Walters Shoal during Cruise MD208 of the Tropical Deep-Sea Benthos programme is documented. In total, 50 species were obtained, 30 of which are new and apparently endemic to the seamount. Of the other 20 species, eight are regionally endemic to the south-western Indian Ocean, 11 are more widely distributed in the Indo-West Pacific and one is possibly of deep-water Atlantic origin. The primary affinities of the fauna are with warm temperate South Africa and the tropical western Indian Ocean, but one species is potentially a seamount endemic of southern affinity. A new pseudococculinid genus living on decomposing bird feathers is described, a biogenic substrate association previously unknown in the Mollusca. The following new genera are described: Imbricoscelis gen. nov. and Pterodacna gen. nov. The following new species are described: Akritogyra crenulata sp. nov., Bathymophila williamsae sp. nov., Benthobrookula araneum sp. nov., Be. galeneae sp. nov., Be. laticostata sp. nov., Be. scalaroides sp. nov., Be. semisculpta sp. nov., Bruceina areneformis sp. nov., Calliostoma pantopunctatum sp. nov., Cantrainea herosae sp. nov., Carinastele achrosta sp. nov., Cornisepta marshalli sp. nov., Emarginula lentiginosa sp. nov., E. nodulicostata sp. nov., E. retrogyra sp. nov., E. salebrosa sp. nov., Fluxinella dufresneae sp. nov., Gibbula roseosticta sp. nov., Hadroconus scobina sp. nov., Kaiparathina monticola sp. nov., Lissotesta wareni sp. nov., Microcollonia miniata sp. nov., Mikro crassus sp. nov., Parviturbo cicatricosus sp. nov., Phragmomphalina candida sp. nov., Pterodacna boucheti gen. et sp. nov., Solariella asaphea sp. nov., Spinicalliotropis lepidota sp. nov., Stomatella multilirata sp. nov. and Trenchia mcleani sp. nov. The following new combinations are proposed: Brookula coronis Barnard, 1963 is transferred to Imbricoscelis gen. nov., Cantharidus nolfi Poppe, Tagaro & H. Dekker, 2006 is transferred to Kaiparathina Laws, 1941 and Solariella incisura Melvill, 1909 is transferred to Phragmomphalina Herbert & Williams, 2020. The following new synonyms are proposed: Carinastele wareni Vilvens, 2014 is a synonym of Bruceina cognata (Marshall, 1988); Fluxinella stellaris Bozzetti, 2008 is a synonym of Agagus stellamaris Herbert, 1991.
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A Monograph of the Fauna of the Cornbrash
Book
  • Sep 2015
The thin but widespread Cornbrash Formation is a marine sedimentary deposit of particular interest and importance to stratigraphers because, as revealed by its palaeontology, within it lies a transgressive event which marks the boundary between the Middle Jurassic Bathonian and Callovian stages. The monographic treatment of its varied fauna was started by John Frederick Blake (1839–1906), but he died before the work was completed, and it remained unfinished. This one-volume reissue comprises the two parts that were originally published separately. Part 1 (issued in November 1905) includes details of Cornbrash exposures from Dorset to Yorkshire, and systematic descriptions of the vertebrates (reptiles, crocodiles, fish) and molluscs (nautiloids, ammonites, belemnites and gastropods). The second part (issued posthumously in December 1907) continues to cover the molluscs (scaphopods) and draws the monograph to a premature close. Some seventy taxa are illustrated in nine lithographic plates.
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