Taxonomy and diversity of slit‐band gastropods (Order Pleurotomariida) and some slit bearing Caenogastropoda from the Pennsylvanian of the USA

Pleurotomariida have the longest fossil record among living gastropods and are diverse and abundant in the middle and upper Palaeozoic. Its traditional classification is based on adult shell characters. The early shell morphology has been largely unknown. We describe exceptionally well‐preserved Pleurotomariida from the Pennsylvanian marine shales of Texas, Oklahoma, Kansas and Ohio. In total, 38 species representing 19 genera are described, including 10 new species, one new genus and one new subgenus: Eirlysella buckhornensis gen. et sp. nov., Shansiella (Oklahomaella) globilineata subgen. et sp. nov., Phymatopleura girtyi, Phymatopleura conica, Worthenia (Yochelsonospira) kuesi, Dictyotomaria turrisbabel, Paragoniozona yanceyi, Spiroscala shwedagoniformis, Peruvispira oklahomaensis, Baylea tenera. Replacement names are Paragoniozona ornata nom. nov. (for Pleurotomaria aspera Girty), Spiroscala quasipulchra nom. nov. (for Euconospira pulchra Batten). The early ontogenetic shells including protoconchs and early teleoconchs are reported in detail for the first time for most taxa. Most species have a protoconch of one whorl as that of living Vetigastropoda. Planktotrophic protoconchs (multi‐whorled larval shells with sinusigera) are reported for Platyzona and Peruvispira; they are therefore placed in the family Goniasmatidae (Caenogastropoda). Repaired shell scars were found in juvenile Pleurotomariida specimens (c. 1 mm), suggesting exposure to predation from an early stage of ontogeny. Pleurotomariida are strongly dominant in surface samples of the Finis Shale (Texas) but in bulk samples using fine mesh‐sizes, dominance is much less pronounced, indicating a change in clade proportion depending on sampling method. The taxonomic richness and abundance of Pleurotomariida seen in these Carboniferous shales have not been reported from post‐Triassic formations.The Deutsche Forschungsgemeinschaft (DFG) http://dx.doi.org/10.13039/50110000165

Syn-Vivo Bioerosion of Nautilus by Endo- and Epilithic Foraminiferans (New Caledonia and Vanuatu)

A variety of syn-vivo bioerosion traces produced by foraminiferans is recorded in shells of Nautilus sampled near New Caledonia and Vanuatu. These are two types of attachment scars of epilithic foraminiferans and two forms of previously undescribed microborings, a spiral-shaped and a dendritic one, both most likely being the work of endolithic 'naked' foraminiferans. Scanning electron microscopy of epoxy-resin casts of the latter revealed that these traces occur in clusters of up to many dozen individuals and potentially are substrate-specific. The foraminiferan traces are the sole signs of bioerosion in the studied Nautilus conchs, and neither traces of phototrophic nor other chemotrophic microendoliths were found. While the complete absence of photoautotrophic endoliths would be in good accordance with the life habit of Nautilus, which resides in aphotic deep marine environments and seeks shallower waters in the photic zone for feeding only during night-time, the absence of any microbial bioerosion may also be explained by an effective defence provided by the nautilid periostracum. Following this line of reasoning, the recorded foraminiferan bioerosion traces in turn would identify their trace makers as being specialized in their ability to penetrate the periostracum barrier and to bioerode the shell of modern Nautilus

A CHAETETID SPONGE ASSEMBLAGE FROM THE DESMOINESIAN (UPPER MOSCOVIAN) BUCKHORN ASPHALT QUARRY LAGERSTÄTTE IN OKLAHOMA, USA

The first detailed study on chaetetids from the Buckhorn Asphalt Quarry Lagerstätte is presented. Among the investigated specimens we found two samples (chaetetid specimens 2 and 6) that are different from all others in the quarry. Thin sections of these display a complex fragmentation of these Buckhorn chaetetids. Additionally, one of these samples contains two chaetetid morphotypes growing side by side, thus, in the same paleoenvironment. These specimens differ in their mode of growth (laminar and domical), which suggests that chaetetid growth was most likely influenced by genetic factors rather than by the paleoenvironment. We observed a feature, not hitherto reported as far as we are aware, on the surface of chaetetids; namely a regular clustering of seven tubules surrounding a central tubule. This feature could have had an exhalant function. Mineralogical analyses of the skeleton indicate primary high magnesian-calcite mineralogy, which is in accordance with reports in the literature. Cements precipitated during diagenesis are either calcite or dolomite and, where associated with microbial mats, they may contain a distinct amount of manganese. The comparison of the chaetetid skeletons from the Buckhorn Asphalt Quarry leads to the impression, that they represent various morphotypes or even species. Because of the lack of unique features, we have refrained however, from describing new species

Taxonomy and diversity of slit-band gastropods (Order Pleurotomariida) and some slit bearing Caenogastropoda from the Pennsylvanian of the USA

Pleurotomariida have the longest fossil record among living gastropods and are diverse and abundant in the middle and upper Palaeozoic. Its traditional classification is based on adult shell characters. The early shell morphology has been largely unknown. We describe exceptionally well-preserved Pleurotomariida from the Pennsylvanian marine shales of Texas, Oklahoma, Kansas and Ohio. In total, 38 species representing 19 genera are described, including 10 new species, one new genus and one new subgenus: Eirlysella buckhornensis gen. et sp. nov., Shansiella (Oklahomaella) globilineata subgen. et sp. nov., Phymatopleura girtyi, Phymatopleura conica, Worthenia (Yochelsonospira) kuesi, Dictyotomaria turrisbabel, Paragoniozona yanceyi, Spiroscala shwedagoniformis, Peruvispira oklahomaensis, Baylea tenera. Replacement names are Paragoniozona ornata nom. nov. (for Pleurotomaria aspera Girty), Spiroscala quasipulchra nom. nov. (for Euconospira pulchra Batten). The early ontogenetic shells including protoconchs and early teleoconchs are reported in detail for the first time for most taxa. Most species have a protoconch of one whorl as that of living Vetigastropoda. Planktotrophic protoconchs (multi-whorled larval shells with sinusigera) are reported for Platyzona and Peruvispira; they are therefore placed in the family Goniasmatidae (Caenogastropoda). Repaired shell scars were found in juvenile Pleurotomariida specimens (c. 1 mm), suggesting exposure to predation from an early stage of ontogeny. Pleurotomariida are strongly dominant in surface samples of the Finis Shale (Texas) but in bulk samples using fine mesh-sizes, dominance is much less pronounced, indicating a change in clade proportion depending on sampling method. The taxonomic richness and abundance of Pleurotomariida seen in these Carboniferous shales have not been reported from post-Triassic formations

On Paleozoic platycerate gastropods

The platycerate gastropods Orthonychia yutaroi Ebbestad, sp. nov. (Ordovician, Boda Limestone, Sweden), O. enorme (Silurian, Sweden, Gotland), O. parva (Pennsylvanian, Finis Shale Member, USA), and Orthonychia sp. (Mississippian, Imo Formation, USA) are studied including their protoconch morphology. Orthonychia yutaroi is the oldest known species in Orthonychia. Platycerates contain species with both, openly and tightly coiled protoconchs. This is the first report that tightly coiled protoconchs occur in Orthonychia. This and previously published observations blur the diagnostic difference between orders Cyrtoneritimorpha (openly coiled protoconch) and Cycloneritimorpha (tightly coiled protoconch). We suggest to treat Cyrtoneritimorpha and Cycloneritimorpha as synonyms of Neritimorpha. The monotypic Devonian genus Pragoserpulina is morphological so close to the Orthonychia species reported herein that synonymy of both genera seems to be possible (and thus of the families Pragoserpulinidae and Orthonychiidae). Protoconch morphology and dimensions suggest that the studied platycerate species had planktotrophic larval development. By contrast, two studied Carboniferous euomphaloid species (one with an openly and the other with tightly coiled protoconch) have paucispiral, large protoconchs indicating non-planktotrophic larval development. We assume that openly and tightly coiled protoconchs were present in various Paleozoic gastropod clades and that selection acted against the openly coiled protoconch morphology. It has previously been proposed that increasing predation pressure in the plankton was the reason for the demise of openly coiled protoconchs (Paleozoic plankton revolution). The presence of larval planktotrophy in platycerates excludes the possibility that they belong to extant basal gastropod clades such as Patellogastropoda, Cocculiniformia, and Vetigastropoda. However, a previously proposed close relationship to Neritimorpha is corroborated

Morphotype 4 in <i>Nautilus macromphalus</i> from New Caledonia.

<p>(A) SEM image of initial borings of the foraminifer in an epoxy-resin cast. (B) Mature morphology with numerous irregularly branching galleries forming a hemispherical plexus. (C) Close-up of galleries displaying their irregular surface texture. (D) SEM-photograph of shell surface illustrating the entrance of the foraminiferan trace.</p

Shell fragments of the <i>Nautilus pompilius</i> specimen from Vanuatu (AMNH 310431) and the three <i>Nautilus macromphalus</i> specimens from New Caledonia.

<p>(A) <i>N</i>. <i>pompilius</i>. (A3-A4) Exemplary fragments of the shell. (A5) Dentritic structures on the shell surface produced by boring ‘naked’ foraminiferans (producing morphotype 3). (B) Specimen AMNH 93431, <i>N</i>. <i>macromphalus</i>. (C) Specimen AMNH 93432, <i>N</i>. <i>macromphalus</i>. (D) Specimen AMNH 93433, <i>N</i>. <i>macromphalus</i>. Scale bar for the shells is 1 cm unless indicated otherwise.</p