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 semilunar, 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 protacrodontid 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 distinguished in the collection reflecting a moderate degree of linear gradient monognathic heterodonty. The range of morphologies otherwise displayed by the collection of teeth shows the greatest similarity to that described for the dentitions of relatively high-crowned hybodontids from the Mesozoic. The internal structure of the teeth, including their vascularization system is reconstructed using microtomography. The highest chondrichthyan taxonomic diversity is found in the Artinskian, especially from the localities of the Middle and South Urals. Key words: Chondrichthyes, Elasmobranchii, teeth, Permian, Russia, Urals.
Diverse remains of chondrichthyans were found in several stratigraphic levels in 18 cores of the Devonian and Lower Carboniferous of Belarus. Most of the taxa were first reported in that territory. A ...new species of ctenacanthiform shark, Tamiobatis elgae, is described. The internal structure of teeth of this species is reconstructed for the first time using microtomography. The distribution of chondrichthyan taxa is analysed.
A diverse assemblage of fishes (isolated teeth and scales) is reported from the Middle to Upper Pennsylvanian Buckhorn Asphalt Quarry Lagerstätte 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.
Very rare chondrichthyan spines from the Famennian (Upper Devonian) of European Russia are referred here to ctenacanthiforms, euselachians and a chondrichthyan group of uncertain systematic position. ...Ctenacanthus Agassiz, 1837 is recorded from the lower and middle Famennian of the central and north-western parts of the area. Sculptospina makhlaevi Lebedev gen. et sp. nov. originates from the lower Famennian of the Lipetsk Region. The holotype of ‘Ctenacanthus’ jaekeli Gross, 1933 and a new specimen from the upper Famennian of the South Urals are shown to belong to the same taxon, which is transferred to Acondylacanthus St. John and Worthen, 1875. New specimens of Tuberospina nataliae Lebedev, 1995 from the upper Famennian of Central Russia are described in detail. The newly presented material increases our knowledge of the composition of Famennian marine assemblages from the East European Platform. It is suggested that these assemblages may be classified as chondrichthyan-dominated and dipnoan-dominated. Hypothetically, after the end- Devonian Hangenberg extinction event, which affected numerous secondary consumers in vertebrate communities, some chondrichthyan groups could have encroached to take advantage of previously occupied ecological niches. Ctenacanthus, as well as Acondylacanthus and Amelacanthus survived the end-Devonian mass extinction to continue into the Carboniferous.
A diverse assemblage of fish microremains is reported from the Virgilian (Gzhelian), Upper Pennsylvanian Finis Shale outcrop at Lost Creek Lake near Jacksboro (Texas, USA). The assemblage contains ...diverse remains of chondrichthyans, rare acanthodians and actinopterygians. The chondrichthyans are represented by a xenacanthimorph, ctenacanthiforms, symmoriiforms, an euselachian
,
a neoselachian, a petalodontiform, eugeneodontiforms, a helodontiform and euchondrocephalian taxa. The teeth of
Bransonella
dominate the chondrichthyan microremains. The occurrence of
Bransonella lingulata
in the Gzhelian Finis Shales of Texas is the youngest in the world. The assemblage includes widely distributed taxa of chondrichthyans. The chondrichthyan fauna from the Finis Shale outcrop differs from the rich faunas of the Kasimovian–Gzhelian from other regions such as New Mexico and Nebraska in the USA, Moscow, Samara and Volgograd regions of Russia, Spain, Germany and the Czech Republic by the dominance of bransonelliform remains and the set of diverse ctenacanthiforms and euchondrocephalians. The new assemblage of fishes demonstrates the presence of chondrichthyan taxa with different food specialisation in the Virgilian faunal community.
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In order to identify novel nonnucleoside inhibitors of HIV-1 reverse transcriptase two series of amide-containing uracil derivatives were designed as hybrids of two scaffolds of ...previously reported inhibitors. Subsequent biological evaluation confirmed acetamide uracil derivatives 15a–k as selective micromolar NNRTIs with a first generation-like resistance profile. Molecular modeling of the most active compounds 15c and 15i was employed to provide insight on their inhibitory properties and direct future design efforts.
An acanthodian assemblage is reported for the first time from the Silurian-Devonian boundary beds of Novaya Zemlya Archipelago, Russia. The acanthodian scales and rare other vertebrate microremains ...were in a sample collected from the Reliktovoe Formation of the western coast of Inostantzev Bay, North Island. The assemblage includes Gomphonchus mediocostatus, Gomphonchoporus hoppei taxa previously described from the Pridoli - Lochkovian of Laurussia, and Taimyrolepis composita occurred in the Lochkovian of Siberia. Gomphonchus mediocostatus and Gomphonchoporus hoppei are widely distributed in the Baltica palaeogeographic province, and Taimyrolepis is known from the Siberia province, indicating connection between those provinces.
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