The revision of "Cladodus" occidentalis, a late Palaeozoic ctenacanthiform shark (original) (raw)
Related papers
… Journal of the …, 2009
Extensive sampling of several Barremian and Albian-Cenomanian levels across the Aguilón, Oliete and Aliaga subbasins of the Iberian Basin, north-east Spain, yielded abundant material of new or so far poorly known neoselachians. The faunas consist of 16 different species, five of which represent new species and two new genera: Cantioscyllium brachyplicatum sp. nov., Platypterix venustulus gen. et sp. nov., Ptychotrygon pustulata sp. nov., Ptychotrygon striata sp. nov. and Iberotrygon plagiolophus gen. et sp. nov. In addition, teeth of Heterodontus cf. H. carerens, Lamniformes indet., Pteroscyllium sp., Scyliorhinidae indet., Rhinobatos sp., Spathobatis sp., Belemnobatis sp., Ptychotrygon geyeri, Ptychotrygon sp. and Celtipristis herreroi are described. The new family Ptychotrygonidae is defined. The localities comprise palaeoenvironments ranging from lacustrine and shallow lake to open marine settings. Neoselachians are almost completely absent from continental settings in the Barremian, as a result of prevailing freshwater conditions, but became more abundant in marine strata. The Albian-Cenomanian selachian assemblage is the most profuse and diverse of the three assemblages studied. It is dominated by small, benthic and near-coastal taxa, for instance Cantioscyllium and Ptychotrygon, and contains several new species, including an endemic batoid, Iberotrygon plagiolophus gen. et sp. nov.
The early evolutionary history of sharks and shark-like fishes
2014
Chapter 1: Introduction 1 Chapter 2: Methodology and definitions of terms 2.1. Methods 2.1.1. Scale structure analysis 6 2.1.2. Phylogenetic analysis 7 2.2. Definitions of terms 9 2.3. Acquisition and accession of specimens 12 2.4. Institutional abbreviations 13 Chapter 3: North American scale taxa from the Upper Ordovician shed light on the early evolution of the chondrichthyan integumentary skeleton 3.1. Introduction 18 3.2. Systematic palaeontology 20 3.3. Discussion 3.3.1. The characteristics of chondrichthyan scales 31 ii 3.3.2. The integumentary skeleton of Ordovician chondrichthyans 3.4. Conclusions Chapter 4: Ordovician origin of Mongolepidida and the integumentary skeleton of basal chondrichthyans 4.1. Introduction 4.2. Systematic palaeontology 4.3. Discussion 4.3.1. Crown morphogenesis of mongolepid scales 4.3.2. Mongolepid scale crown histology 4.3.3. Histology of mongolepid scale bases 4.3.4. Canal system of mongolepid scales 4.3.5. Systematic position of the Mongolepidida 4.4. Conclusions Chapter 5: Elegestolepis and its kin, the earliest chondrichthyans to develop mono-odontode scale crowns 5.1. Introduction 5.2. Systematic palaeontology 5.3. Discussion iii 5.3.1. Chondrichthyan characteristics of elegestolepid mono-odontode scales 5.3.2. Elegestolepida in the context of other Lower Pazaeozoic chondrichthyans 5.4. Conclusions Chapter 6: Scale-based phylogeny of Palaeozoic chondrichthyans 6.1. Introduction 6.2. Results 6.2.1. Classification schemes of scale morphogenesis in chondrichthyans 6.2.2. Scale morphogenetic types in chondrichthyans 6.2.3. Chondrichthyes-specific developmental pattern of the integumentary skeleton 6.2.4. Remarks on the phylogenetic analyses 6.2.5. Populating the stem of the chondrichthyan tree 6.2.6. Degree of correlation with existing gnathostome phylogenies 6.3. Conclusions iv Chapter 7: Conclusions References Appendix Matrix of character states assigned to the 51 taxa included in the phylogenetic analyses Character list Taxa included in the analyses, studied material, literature used in the coding the character-taxon matrix v I am grateful to the following people for granting me the opportunity to examine museum collections and/or obtain study material over the course of the project:
Due to the peculiar combination of dental features characteristic for different squaliform families, the position of the Late Cretaceous genera Protoxynotus and Paraphorosoides within Squaliformes has long been controversial. In this study, we revise these genera based on previously known fossil teeth and new dental material. The phylogenetic placement of Protoxynotus and Paraphorosoides among other extant and extinct squaliforms is discussed based on morphological characters combined with DNA sequence data of extant species. Our results suggest that Protoxynotus and Paraphorosoides should be included in the Somniosidae and that Paraphorosoides is a junior synonym of Protoxynotus. New dental material from the Campanian of Germany and the Maastrichtian of Austria enabled the description of a new species Protoxynotus mayrmelnhofi sp. nov. In addition, the evolution and origin of the characteristic squaliform tooth morphology are discussed, indicating that the elongated lower jaw teeth with erected cusp and distinct dignathic heterodonty of Protoxynotus represents a novel functional adaptation in its cuttingclutching type dentition among early squaliform sharks. Furthermore, the depositional environment of the tooth bearing horizons allows for an interpretation of the preferred habitat of this extinct dogfish shark, which exclusively occupied shelf environments of the Boreal-and northern Tethyan realms during the Late Cretaceous.
2014
Doliodus problematicus is the oldest known fossil shark-like fish with an almost intact dentition (Emsian, Lower Devonian, c. 397Ma). We provide a detailed description of the teeth and dentition in D. problematicus, based on tomographic analysis of NBMG 10127 (New Brunswick Museum, Canada). Comparisons with modern shark dentitions suggest that Doliodus was a ram-feeding predator with a dentition adapted to seizing and disabling prey. Doliodus provides several clues about the early evolution of the “shark-like” dentition in chondrichthyans and also raises new questions about the evolution of oral teeth in jawed vertebrates. As in modern sharks, teeth in Doliodus were replaced in a linguo-labial sequence within tooth families at fixed positions along the jaws (12–14 tooth families per jaw quadrant in NBMG 10127). Doliodus teeth were replaced much more slowly than in modern sharks. Nevertheless, its tooth formation was apparently as highly organized as in modern elasmobranchs, in which future tooth positions are indicated by synchronized expression of shh at fixed loci within the dental epithelium. Comparable dental arrays are absent in osteichthyans, placoderms, and many “acanthodians”; a “shark-like” dentition, therefore, may be a synapomorphy of chondrichthyans and gnathostomes such as Ptomacanthus. The upper anterior teeth in Doliodus were not attached to the palatoquadrates, but were instead supported by the ethmoid region of the prechordal basicranium, as in some other Paleozoic taxa (e.g., Triodus, Ptomacanthus). This suggests that the chondrichthyan dental lamina was originally associated with prechordal basicranial cartilage as well as jaw cartilage, and that the modern elasmobranch condition (in which the oral dentition is confined to the jaws) is phylogenetically advanced. Thus, oral tooth development in modern elasmobranchs does not provide a complete developmental model for chondrichthyans or gnathostomes. J. Morphol., 2013. © 2013 Wiley Periodicals, Inc.
FOSSIL SHARKS FROM ALBIAN AND CENOMANIAN DEPOSITS OF THE KURSK OBLAST (RUSSIA
FOSSIL SHARKS FROM ALBIAN AND CENOMANIAN DEPOSITS OF THE KURSK OBLAST (RUSSIA), 2023
This article briefly describes fossil selachian assemblages from the Albian-Cenomanian ages from three localities in Kursk Oblast. The collected material is mainly represented by isolated shark teeth. A total of 14 unambiguous taxa have been identified including cf. Polyacrodus sp., Notidanodon sp., Heterodontus sp., Cederstroemia sp., cf. Pseudomegachasma sp., Archaeolamna ex.gr. kopingensis, Dwardius sp., Cretoxyrhina cf. C. vraconensis, Paraisurus macrorhiza, Squalicorax sp., Protolamna sp., Eostriatolamia sp., Synechodus sp., and Paraorthacodus sp. These taxa are all new to the Cretaceous selanchian fossil record of Kursk Oblast. These fossil materials allow for improvements in our knowledge in the paleoecology and species-richness of East-European, Albian-Cenomanian selachian assemblages. Further study of selachian material from Cretaceous deposits in Kursk Oblast may further clarify information on the geographical distribution, paleobiogeography, paleoecology and taxonomic diversity of this group of vertebrates, both in the Early Cretaceous and Late Cretaceous in Central Russia, and in Europe as a whole.
A new euselachian shark from the early Permian of the Middle Urals, Russia
The isolated teeth of a new euselachian shark Artiodus prominens Ivanov and Duffin gen. et sp. nov. have been found in the Artinskian Stage (Early Permian) of Krasnoufimskie Klyuchiki quarry (Sverdlovsk Region, Middle Urals, Russia). The teeth of Artiodus possess a multicuspid orthodont crown with from four to nine triangular cusps; prominent labial projection terminating in a large round tubercle; distinct ornamentation from straight or recurved cristae; oval or semilu-nar, elongate, considerably vascularized base; dense vascular network formed of transverse horizontal, ascending, short secondary and semicircular canals. The teeth of the new taxon otherwise most closely resemble the teeth of some prot-acrodontid and sphenacanthid euselachians possessing a protacrodont-type crown, but differ from the teeth of all other known euselachians in the unique structure of the labial projection. The studied teeth vary in crown and base morphology , and three tooth morphotypes can be distingu...