Fig 5 - uploaded by Christopher Duffin
Content may be subject to copyright.
Comparison of the right lower posterior (mandibular) tooth plates in a range of myriacanthid genera. A: Oblidens bornholmensis gen. et sp. nov. (Pliensbachian of Denmark). B: Myriacanthus paradoxus (Rhaetian to Sinemurian, UK). C: Halonodon luxembourgensis (Hettangian, Luxembourg). D: Halonodon warneri (Sinemurian of Belgium). E: Metopacanthus granulatus (Sinemurian, UK). F: Agkistracanthus mitgelensis (Rhaetian to Hettangian of Switzerland and the UK). G: Acanthorhina jaekeli (Toarcian of Germany). H: Alethodontus bavariensis (Hettangian of Germany). After Duffin & Delsate (1993). Scale bar =10 mm throughout.
Source publication
A new myriacanthid holocephalian is described from the Hasle Formation (probably the Uptonia jamesoni subzone to the Acanthopleuroceras valdani subzone, Early Pliensbachian, Early Jurassic) of Bornholm, Denmark, on the basis of isolated upper posterior (palatine) and lower posterior (man-dibular) tooth plates. Oblidens bornholmensis gen. et sp. nov...
Contexts in source publication
Context 1
... Agkistracanthus, a convex ridge crosses the oc- clusal surface diagonally from the labial angle to the lingual angle, dividing the surface into two (Duffin & Furrer 1981, p1.2, fig. la; Fig. 5F). This ridge is pro- portionally much narrower in Agkistracanthus than its equivalent in Oblidens gen. nov., and the tooth plate as a whole is less elongate, more robust and trapezoid in outline. The lower posterior tooth plate of Metopacan- thus also possesses a single diagonal ridge, this time arising from part way along the labial ...
Context 2
... elongate, more robust and trapezoid in outline. The lower posterior tooth plate of Metopacan- thus also possesses a single diagonal ridge, this time arising from part way along the labial border passing across the occlusal surface toward the lingual angle, but the form of the tooth plate is much more elongate and slender than Oblidens gen. nov. (Fig. ...
Context 3
... (Duffin 1983b) is based upon an isolated external mould of a lower posterior tooth plate whose occlusal surface is transected by two diagonal ridges arising from a common origin on the labial border of the plate; the ridges diverge posteriorly, with one di- rected toward the lingual angle and the other toward the distal angle of the tooth plate (Fig. ...
Citations
... However, due to the coarse-grained nature of the sediment at Hasle (more fine-grained at Rønne), at the type locality at Hasle, most invertebrates are poorly preserved. Condrichthyan remains are common in the form of abundant selachian teeth comprising hybodont and neoselachian species of sharks (Rees 1998), and at least two species of holocephalians (Duffin & Milàn 2017. Fish remains are abundant and represented by numerous undescribed scales. ...
Serpulid remains are very rare in the Lower Jurassic Hasle Formation of Bornholm, Denmark. A historical specimen mentioned, but not figured by Malling & Grön wall (1909) was reexamined and attributed to Pentaditrupa quinquesculcata and here f igured for the first time. New finds of additional well-preserved serpulid tubes are described as Serpula? alicecooperi sp. nov, which show adaptations for a lifestyle on fine-grained sediment in a nearshore environment.
... However, due to the coarse-grained nature of the sediment, most invertebrates are badly preserved. Remains of marine vertebrates are common in the form of abundant selachian teeth, comprising three species of hybodont sharks and teeth from three neoselachian species [20], and so far, at least two species of holcephalians have been reported [12,21]. Fish remains are abundant in the form of numerous undescribed scales. ...
Turiasauria is a clade of basal sauropod dinosaurs hitherto only known from the Middle Jurassic (Bathonian) to the Lower Cretaceous (Valanginian). A new find of a shed tooth crown from the Lower Jurassic (Pliensbachian), Halse Formation of Bornholm, Denmark, is spoon-like, asymmetrical, and heart-shaped, which identifies the tooth as turiasaurian, pushing the origin of the Turiasauria some 17 My back into the Lower Jurassic. This suggests a North Pangean/Laurasian origin of the turiasaurian clade, which then, during the Middle to Late Jurassic, dispersed through Europe, India, and Africa, with their latest representatives found in the Early Cretaceous of England and North America. Furthermore, this is the first record of a sauropod from the Pliensbachian in Europe.
... Mesozoic holocephalians all belong to the Order Chimaeriformes, and can be classified into three suborders: the squalorajoids are represented only by the type genus (Squaloraja; Hettangian to Sinemurian of Europe); myriacanthoids range from the Rhaetian (Late Triassic) to the Tithonian (Late Jurassic) of Europe; true chimaeroids, whose oldest known representatives are Eomanodon simmsi and Brachymylus latus from the Pliensbachian of England and Germany respectively (Ward & Duffin 1989;Duffin 1996). The discovery of tooth plates of Oblidens bornholmensis, a myriacanthid, on Bornholm (Duffin & Milàn 2017) marked the first record of the group in Pliensbachian deposits and the earliest point in the overlap of the ranges of the myriacanthoids and chimaeroids. Myriacanthoid remains seem to dominate the holocephalian fossil record in the Early Jurassic, but chimaeroid remains are more abundant and diverse by the Late Jurassic and Early Cretaceous. ...
... Further specimens of myriacanthid holocephalian tooth plates have come to light since the initial work of Duffin & Milàn (2017). The purpose of the present paper is to describe and discuss this additional material and highlight holocephalian diversity in the Pliensbachian Hasle Formation. ...
... The type section for the Hasle Formation is exposed just south of Hasle town (Fig. 1B), approximately 1 km west of a fault line which controlled the shoreline geography during the deposition of the formation (Surlyk & Noe-Nygaard 1986;Milàn & Surlyk 2015). The formation is dominated by arenaceous deposits; reddish-brown, hummocky cross-stratified sandstones and swaley cross-stratified siltstones are interbedded with very fine sandstones (Duffin & Milàn 2017, fig. 1C). ...
Oblidens bornholmensis, known from isolated upper posterior (palatine) and lower posterior (mandibular) tooth plates, was the first myriacanthid holocephalian to be described from the Hasle Formation (Pliensbachian, Early Jurassic) of Bornholm (Denmark). Further collecting in the Hasle Formation has yielded seven more specimens of myriacanthid tooth plates. Two mandibular tooth plates are assigned to Myriacanthus paradoxus, thereby extending both the geographical and stratigraphic range of the genus. In addition to new material of Oblidens bornholmensis, some distinctive myriacanthid palatine and mandibular tooth plates are described and left in open nomenclature. The Early Pliensbachian deposits of Bornholm preserve the most diverse myriacanthid fauna known to date.
... The taxonomic diversity and distribution patterns of Early Jurassic elasmobranchs thus are strongly biased towards open marine, offshore environments, rendering the study of their macroevolutionary patterns and processes difficult (Underwood 2004(Underwood , 2006. So far, the Danish island of Bornholm in the Baltic Sea is the only European place known to have produced Early Jurassic cartilaginous fish remains of marginal marine origin, including those of hybodontiforms, neoselachians, and holocephalians (Rees 1998;Duffin and Milàn 2017). These are derived from the Hasle Formation, a fine-grained sandstone to coarse-grained siltstone of early Pliensbachian age that was deposited in close proximity to the Fennoscandian Shield (see Vajda and Wigforss-Lange 2009). ...
Here we describe a new, previously unrecognized elasmobranch microfossil assemblage consisting of isolated dental material from late Pliensbachian marginal marine, near-shore deposits of Grimmen in northeastern Germany. The faunal composition indicates close affinities to other European pre-Toarcian elasmobranch-bearing localities, as it is predominantly composed of Hybodontiformes (Hybodus reticulatus?, H. hauffianus?, Lissodus sp.), Synechodontiformes (Palidiplospinax enniskilleni, P. occultidens, Paraorthacodus sp., Sphenodus sp.), and Hexanchiformes (Notidanoides sp.), as well as teeth attributable of the enigmatic Early Jurassic galeomorph shark Agaleus dorsetensis. In addition, the here reported elasmobranch tooth assemblage includes the oldest undisputable fossil records of Orectolobiformes and Batomorphii, each being represented by a single complete tooth only. The orectolobiform specimen is reminiscent of hemiscyllids but left in open nomenclature due to its very generalized morphology preventing any taxonomic identification. The batomorph tooth, conversely, is characterized by a unique combination of morphological features, which allows the introduction of new genus and species, Antiquaobatis grimmenensis gen. et sp. nov. The fossil assemblage presented here contributes to our current knowledge of late Early Jurassic chondrichthyan diversity and distributional patterns, providing some support for the hypothesis that most modern neoselachian lineages were initially linked to marginal marine, near-shore environments, before moving into open marine, offshore habitats by the Toarcian.
