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A diverse assemblage of fishes (isolated teeth and scales) is reported from the Middle to Upper Pennsylvanian Buckhorn Asphalt Quarry Lagerstatte in Oklahoma, USA. The assemblage includes chondrichthyans such as the bransonelliform Bransonella lingulata, the xenacanthiform Xenacanthus, the symmoriiform Stethacanthus, ctenacanthiforms, an polyacrodontid euselachian, anachronistid neoselachians (Cooleyella amazonensis and C. sp.) and an iniopterygian paraselachian cf. Sibyrhynchidae. Moreover, the assemblage encompasses remains of acanthodians and various actinopterygians and a single specimen of an osteolepiform sarcopterygian. Most of the taxa are cosmopolitan during the Late Palaeozoic. The occurrence of bransonelliform and xenacanthiform species at the same locality is very rare in the Carboniferous. The assemblage yields the first Carboniferous occurrences of a polyacrodontid hybodontoid and an actinopterygian belonging to the Acropholidae. Bransonella lingulata from the Desmoinesian/Moscovian of the Buckhorn Asphalt Quarry in Oklahoma represents the youngest occurrence of this species.

During field and laboratory investigation of the phosphate nodules that are eroding from the Excello Shale of the Senora Formation, Cabaniss Group, Desmoinesian, of Middle Pennsylvanian age of Rogers County in northeastern Oklahoma has produced numerous vertebrate, invertebrate, and plant fossils. The vertebrate material recovered include the dermal denticles of Petrodus patelliformis and Listracanthus hystrix, along with teeth of Cladodus occidentals, Caseodus eatoni, Edestus sp, Lisgodus serratus, and a spine from the spine-brush complex of Stethacanthus sp. Previously, the only known vertebrates reported from the Excello Shale of Oklahoma were Edestus and Petrodus. This report thus increases the number of known vertebrates from the Excello Shale of northeastern Oklahoma.

Chondrichthyan fish remains reported from the Permian (Kazanian) deposits of the Chiosha Bay, and the lower course of the Nadtey River of the Kanin Peninsula (Nenets Autonomous District, Arkhangelsk Region, Russia) include dental elements and scales belonging to Stethacanthus cf. S. altonensis (St. John et Worthen, 1875), Symmoriiformes gen. indet., “Ctenacanthus” sp. and “Lissodus” sp., Euselachii gen. indet., Adamantina benedictae Bendix-Almgreen, 1993 and Kanodus robustus sp. nov. The latter genus is assigned to the previously monotypic family Psephodontidae. The record of Stethacanthus in the Middle Permian of Russia is its youngest occurrence worldwide, whilst the occurrence of Adamantina benedictae in the Middle Permian of the Kanin Peninsula is older than the Greenland record.

Sixteen different Lower Carboniferous (Tournaisian Courceyan to Chadian age, Mississippian) chondrichthyan teeth types have been extracted from Triassic erosional/aeolian fills in shallow karst systems found in the limestone quarry at Cromhall, Gloucestershire, England. These Carboniferous teeth have been found within a much larger assemblage of disarticulated bones and teeth belonging to small late Triassic terrestrial reptiles, for which Cromhall quarry is famous. The Carboniferous teeth are derived fossils, released during subaerial dissolution of the surrounding limestones. Owing to low specimen numbers and uncertainty of intraspecific character, 10 types of teeth are left in open nomenclature, although it is likely they represent new taxa. They belong to Jalodus, Ctenacanthiformes, Protacrodus, Orodus, Chomatodus, Petalodontidae, Euchondrocephali?, Helodus and Psephodus. A new genus and species, Cromhallia parvunda, of indeterminate phylogenetic relationships, is also erected. The assemblage includes also an identified suite comprising Thrinacodus ferox, Bransonella cf. nebraskensis and Stethacanthus cf. altonensis. The identification of all fish teeth found in the Cromhall assemblages as derived fossils from the Carboniferous removes any ambiguity regarding the fully terrestrial nature of the late Triassic fauna preserved in the residue-bearing karst systems.

New material from the Famennian of Morocco in the southern Maider comprises chondrichthyan teeth(Thrinacodus, Cobelodus, Denaea, Stethacanthus), actinopterygian remains (scales, teeth and hemilepidotrichium) and one acanthodian scale. The absence of crushing teeth suggests deeper water environments for the Maider Basin than the Tafilalt Basin. Vertebrate microremains from the Famennian of Sardinia, includingSiamodusandJalodusteeth, are illustrated and described. Ichthyofaunal relationships of the North Gondwanan platform during the Famennian are examined.

Very diverse Early Permian chondrichthyan assemblages occur in the Asselian to Artinskian of the Middle and South Urals. They include numerous symmoriid teeth of “Denaea” decora Ivanov, Cobelodus obliquus sp. nov., Stethacanthus and Denaea; the teeth of the ctenacanthoid Heslerodus; the teeth of the synechodontiform Synechodus antiquus sp. nov.; and the teeth of taxa of doubtful affinities – Adamantina foliacea Ivanov, Cooleyella cf. C. fordi (Duffin & Ward), Cooleyella sp. A., as well the scales and denticles of various types. Two new species, Cobelodus obliquus and Synechodus antiquus, are described herein. The Early Permian chondrichthyan assemblages of Urals include a few taxa occurring only in that interval, as well taxa which were distributed in the Carboniferous and persisted into the Early Permian, such as Stethacanthus, Cobelodus, Denaea, “Denaea”, Lissodus, Heslerodus, “Symmorium”, Petalodus, Cooleyella and Adamantina. This occurrence of a synechodontid is the oldest in the world. The symmoriid sharks disappeared in the Middle Permian. The Permian shark faunas of the Urals contain a diverse assemblage of symmoriids, ctenacanthiods and synechodontiforms, but there are no xenacanthids were common in the Permian assemblages of Western Europe

Exceptionally complete material of a new stethacanthid chondrichthyan, Akmonistion zangerli, gen. et sp. nov., formerly attributed to the ill-defined genera Cladodus and Stethacanthus, is described from the Manse Burn Formation (Serpukhovian, Lower Carboniferous) of Bearsden, Scotland. Distinctive features of A. zangerli include a neurocranium with broad supraorbital shelves; a short otico-occipital division with persistent fissure and Y-shaped basicranial canal; scalloped jaw margins for 6–7 tooth files along each ramus; a pectoral-level, osteodentinous dorsal spine with an outer layer of acellular bone extending onto a brush-complex of up to 160% of neurocranial length; a heterosquamous condition ranging from minute, button-shaped, flank scales to the extraordinarily long-crowned scales of the brush apex; and a sharply up-turned caudal axis associated with a broad hypochordal lobe. The functional implications of this anatomy are discussed briefly. The rudimentary mineralization of the axial ske...

The partly articulated specimen of the Palaeozoic (Early Carboniferous) chondrichthyan ‘Cladodus’neilsoni Traquair from East Kilbride has been known since the late nineteenth century. As such, ‘C.’neilsoni Traquair has been cited in numerous publications, but it has become increasingly clear that its anatomy and systematic affinities are obscure. This comprehensive redescription of ‘C.’neilsoni reveals new details of the neurocranium (including presence of an otico-occipital fissure), dentition, visceral arches (clarifying the condition of the basibranchial pattern plus elongate copula), and pectoral fin. These data refute previously suggested synonymies, such as between ‘C’neilsoni and the contemporaneous Bearsden Stethacanthus. Attribution of ‘C.’neilsoni to the taxonomically unsupportable genus ‘Cladodus’ is rejected, and the species is redesignated as Gutturensisneilsoni gen. nov. Preliminary cladistic analysis places Gutturensisneilsoni within a polytomy including Stethacanthus, the symmoriid Cobelodus, and the root of a monophyletic group of neoselachian-like genera. ‘ Cladodont’ as a diagnostic term for early chondrichthyan teeth is found to be insufficiently precise, referring to an ill-defined grade of tooth morphologies present in a wide variety of Palaeozoic genera.

The Devono-Carboniferous chondrichthyan Stethacanthus is best known for its striking 'spine-brush' complex. Here we provide the first detailed description of the neurocranium, using several well-preserved specimens from Bearsden, Scotland (Serpukhovian; Pendleian E1). Significant features include an otico-occipital region of about the same length as the ethmosphenoid division; short but distinct lateral otic processes; a short, broad endolymphatic fossa; a persistent otico-occipital fissure; Y-shaped basicranial canals indicating origin of the lateral aortae anterior to the occipital level; and minimal suborbital shelves limited to small, ethmoidally located outgrowths. Using placoderm, osteichthyan and acanthodian neurocrania for outgroup comparison, PAUP analysis of a matrix of 23 neurocranial characters produced the following branching sequence: (Helodus (Stethacanthus, Cobelodus (Tamiobatis (Xenacanthus (Cladodus wildungensis (Tristychius, Hybodus)))))). The location of Cladoselache in this analysis is uncertain and probably results from missing data and a morphologically restricted character set. Plesiomorphic conditions for chondrichthyan braincases are found to include the presence of a persistent otico-occipital fissure, projection of the median dorsal aorta anterior to the occipital level, and absence of suborbital shelves. These results may have important implications with regard to primitive gnathostome interrelationships, and especially the phylogenetic position of placoderms.

Vertebrate remains have been discovered in the Frasnian and Famennian of the South Urals The ichthyofaunacontains representatives of Phoebodus; Stethacanthus; Symmorium; Protacrodus as well as placoderms; acanthodians; “crossopterygians” dipnoans and palaoniscids. Changes of the fish assemblages are examined. A review of the occurrences of Phoebodus is given.

The ‘spine-brush complex’1 of the extinct, mid-Palaeozoic primitive chondrichthyan shark Stethacanthus is one of the strangest vertebrate appendages known. Its structure has never been defined, but here we reveal that the ‘brush’ is actually an enlarged, specialized extension of the fin baseplate (basal cartilage2). It consists of an unusual type of globular calcified cartilage, a tissue that is often associated with pre-jawed primitive vertebrates3.

Several specimens of an elasmobranch from the upper Mississippian Bear Gulch limestone of Montana are described. The first dorsal spine and fin closely resemble Stethacanthus erectus and to a lesser extent Stethacanthus altonensis. The new genus and species Orestiacanthus fergusi is proposed for the specimens, and it is suggested that recent attempts to synonymize the species of Stethacanthus on the basis of spines are unjustified. The specimens also share the enlarged cranial denticles, general form of the palatoquadrate, cladodont teeth and pectoral fin with S. altonensis. They differ from S. altonensis in proportions of jaws, numbers of tooth families, numbers of prearticular basals and axial radials, morphology of the second dorsal fin, and in the presence of generalized squamation in some specimens (but not the female). The pelvic fins differ greatly in having a prominent metapterygium.

The microscopic anatomy of the peculiar spine-“brush” complex of the Paleozoic shark Stethacanthus altonensis (Symmoriida: Stethacanthidae) reveals that the spine consists of trabecular dentine throughout—no shaft and mantle components are discernible. Parts of the trabecular dentine contain abundant fibers that suggest attachment surfaces for tendons and other connective tissue membranes to the epaxial musculature. The “brush” consists of parallel, membranous tubes and connecting membranes that form an intricate, internal cavity system. In section, this structure resembles sections of erectile tissues in man. The “brush” may thus have been inflatable. The “brush” is covered with a patch of large, massive, dermal denticles pointing forward. Associated with this spine-“brush” is a second patch of enlarged dermal denticles on top of the head whose crowns face backward. The entire complex consists of a variety of gross anatomical, histological, and microscopic anatomical elements. Sexual display or ...

The Paleozoic fin spine Physonemus falcatus St. John and Worthen 1883, from the Valmeyeran St. Louis Limestone of St. Louis, Missouri, has been found on sexually mature males of a small, highly sexually dimorphic chondrichthyan from the Chesterian Bear Gulch Limestone of Montana. An amphistylic suspensorium, cladodont teeth and pectoral fin further characterize this species and the group to which it belongs. The first dorsal spine and fin of males are derivable from a form like that of Stethacanthus altonensis. Males also have elongate rostra and dorsal cranial and fin denticles, while females and juveniles lack denticles, first dorsal fin, or spine. The new genus Falcatus (Order Cladodontida, Family Stethacanthidae) is erected for the species and for the related F. hamatus and F. proclivus. Aspects of the sexual dimorphism are discussed; Falcatus falcatus, with many more males than females, fits a behavioral model of male display-courtship and female choice. Possible evidence of lek aggregations...