Haverfordwest, United Kingdom
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Newman M.J.,Vine Lodge | Mark-Kurik E.,Tallinn University of Technology | Den Blaauwen J.L.,University of Amsterdam | Zupins I.,Natural History Museum of Latvia
Scottish Journal of Geology | Year: 2015

A number of Estonian Devonian fishes are shown to be junior synonyms of Scottish species. The Estonian sarcopterygian osteolepid Gyroptychius pauli was originally thought to be closely related to the Scottish species Gyroptychius milleri being differentiated by minor morphological differences of the skull roof. However, here we show that the only skull roof available of G. pauli to the original description (the holotype) was badly damaged in places. This and the fact that skull roofs of osteolepid fishes are morphologically highly variable has allowed us to compare the Estonian and Scottish species and show that G. pauli is a junior synonym of G. milleri. It has also been known for some time that Estonian coccosteid arthrodire Coccosteus orvikui was a junior synonym of the Scottish species Coccosteus cuspidatus. Here we present the evidence for this assumption and also show that the Scottish coccosteid arthrodire Millerosteus minor is almost certainly present in Estonia. Finally, it is shown that the three species have the same stratigraphical distribution in the two regions, strongly indicating a close faunal connection between the Middle Devonian of Estonia and the Middle Devonian Orcadian Basin of Scotland. © 2015 The Author(s).


PubMed | South Australian Museum, University of Amsterdam, Natural History Museum in London, CAS Institute of Vertebrate Paleontology and Paleoanthropology and 7 more.
Type: Journal Article | Journal: Nature | Year: 2015

Reproduction in jawed vertebrates (gnathostomes) involves either external or internal fertilization. It is commonly argued that internal fertilization can evolve from external, but not the reverse. Male copulatory claspers are present in certain placoderms, fossil jawed vertebrates retrieved as a paraphyletic segment of the gnathostome stem group in recent studies. This suggests that internal fertilization could be primitive for gnathostomes, but such a conclusion depends on demonstrating that copulation was not just a specialized feature of certain placoderm subgroups. The reproductive biology of antiarchs, consistently identified as the least crownward placoderms and thus of great interest in this context, has until now remained unknown. Here we show that certain antiarchs possessed dermal claspers in the males, while females bore paired dermal plates inferred to have facilitated copulation. These structures are not associated with pelvic fins. The clasper morphology resembles that of ptyctodonts, a more crownward placoderm group, suggesting that all placoderm claspers are homologous and that internal fertilization characterized all placoderms. This implies that external fertilization and spawning, which characterize most extant aquatic gnathostomes, must be derived from internal fertilization, even though this transformation has been thought implausible. Alternatively, the substantial morphological evidence for placoderm paraphyly must be rejected.


Burrow C.J.,Queensland Museum | Davidson R.G.,35 Millside Road | Den Blaauwen J.L.,University of Amsterdam | Newman M.J.,Vine Lodge
Journal of Vertebrate Paleontology | Year: 2015

Disarticulated elements in a large, uncompressed regurgitate from Tillywhandland Quarry (Lochkovian), as well as serial sections of an articulated specimen, reveal the three-dimensional shape and structure of fin spines, scapulocoracoid and dermal plates, and the histological structure of dermal and endoskeletal hard tissues of the climatiid acanthodian Climatius reticulatus. Globular calcified cartilage is the only form of mineralization of the head endoskeleton, with the jaws preserved as double-layered globular calcified cartilage. Tooth whorls are borne on both the upper and lower jaws and comprise a vascularized bone base and tooth cusps composed of a vascular network and mesodentine, without a central pulp cavity. The short admedian spine is the only strongly laterally compressed spine; the anterior dorsal fin spine has a wide, splayed base. No evidence was found of large dermal plates between the pectoral fin spine and the median lorical plates, with the prepectoral pinnal plates with spines being the only large paired dermal components of the shoulder girdle. The anterior lorical plate, pinnal plates, and tesserae on the scapulocoracoid bear ornament comparable to the postbranchial apronic ornament in acanthothoracid placoderms. Branchiostegal plates have a thin, dense inner bone layer and an outer dentinous ornament layer but lack a middle osteodentine layer; other postcranial plates and fin spines have a smooth-surfaced inner layer of bone and a thick middle osteodentine layer. Body scales have a crown with areal growth zones formed of Stranggewebe and syncitial mesodentine on a cellular bone base. © 2015 by the Society of Vertebrate Paleontology.


Newman M.J.,Vine Lodge | Burrow C.J.,Ancient Environments | den-Blaauwen J.L.,University of Amsterdam | Davidson R.G.,35 Millside Road
Geodiversitas | Year: 2014

The five species of genus Euthacanthus Powrie, 1864 are reduced to two species on morphological and stratigraphical evidence. Euthacanthus macnicoli Powrie, 1864 and Euthacanthus grandis Powrie, 1870 are here synonymised in the type species E. macnicoli Powrie, 1864. In a previous article, Euthacanthus gracilis Powrie, 1870 and Euthacanthus elegans Powrie, 1870 were combined in the species E. gracilis, and the fifth species, Euthacanthus curtus Powrie, 1870, was reassigned to Uraniacanthus curtus (Powrie, 1870). In this work, we give an in-depth study of the full range of morphological and histological structure of scales over the body of E. macnicoli, as well as of fin spine structure. Our study reveals new features of E. macnicoli, including a large ornamented dorsal sclerotic bone, ornament on the branchiostegal plates, a separate series of gular rays, calcified cartilage forming the jaws, and a postbranchial protruding spinose plate rather than the flat prepectoral plate previously described. © Publications Scientifiques du Muséum national d’Histoire naturelle, Paris.


Burrow C.J.,Ancient Environments | Newman M.J.,Vine Lodge | Davidson R.G.,35 Millside Road | den Blaauwen J.L.,University of Amsterdam
Alcheringa | Year: 2013

Parexus Agassiz was one of the first Early Devonian 'spiny sharks' to be described. The genus is readily recognized by the large size and ornament of its anterior dorsal fin spine. Although two species were erected, reappraisal of all known specimens indicate they should be synonymized in the type species Parexus recurvus. Farnellia tuberculata Traquair, originally described as a vertebral column, is actually tooth rows of jaw dentition, and is also now considered to be a junior synonym of P. recurvus. Parexus has a perichondrally ossified scapulocoracoid of typical acanthodian shape, and diagnostic features of the family Climatiidae, but has distinctive scales comprising appositional growth zones that closely resemble those of the putative stem chondrichthyan Seretolepis elegans Karatajute-Talimaa. © 2013 Copyright Taylor and Francis Limited.


Newman M.J.,Vine Lodge | Davidson R.G.,35 Millside Road | Den Blaauwen J.L.,University of Amsterdam | Burrow C.J.,Ancient Environments
Geodiversitas | Year: 2012

The acanthodian originally described as Euthacanthus curtus Powrie, 1870 from the Early Devonian (Lochkovian) of Scotland was tentatively reassigned to Diplacanthus Agassiz, 1844 later in the nineteenth century, although doubt was cast on this revision. In 1976 Paton suggested that specimens comparable with the single type could belong to Uraniacanthus Miles, 1973, based on similarities with the type species U. spinosus Miles, 1973 from the Lochkovian of England. Hanke et al. (2001) noted that the Canadian Lochkovian species Gladiobranchus probaton Bernacsek & Dineley, 1977 was also very similar to U. spinosus. Our investigations indicate that all three species belong to the genus Uraniacanthus (which has priority over Gladiobranchus Bernacsek & Dineley, 1977) in the family Gladiobranchidae Bernacsek & Dineley, 1977, order Diplacanthiformes Berg, 1940 (revised). This identification supports a biogeographical connection between the Canadian, Scottish and English Early Devonian based on the common presence of the genus Uraniacanthus, as well as other acanthodian genera, including Ischnacanthus Powrie, 1864. Uraniacanthus could also be represented by isolated scales in coeval deposits in the Baltic. © Publications Scientifiques du Muséum national d'Histoire naturelle, Paris.


Burrow C.,Geosciences | den Blaauwen J.,University of Amsterdam | Newman M.,Vine Lodge | Davidson R.,35 Millside Road
Palaeontologia Electronica | Year: 2016

The Diplacanthiformes are a clade of acanthodian fishes which were widespread during the Middle and early Late Devonian. They are best represented in the Middle Devonian, by articulated fossils, fin spines, and abundant scales, the latter particularly from northern Europe. Three species of diplacanthid diplacanthiforms, Diplacanthus crassisimus, Diplacanthus tenuistriatus, and Rhadinacanthus longispinus, are found in Middle Devonian (Eifelian–Givetian) assemblages of articulated fish in northern Scotland. Our detailed study of the dermal structures and endoskeletal shoulder girdles in these fish supports the validity of Rhadinacanthus as a separate genus from Diplacanthus, with the two being differentiated by spine morphology, scale morphology, and histology, and shape and form of the pectoral girdle. In Orkney and Caithness, D. crassisimus first occurs in the Thursius macrolepidotus vertebrate biozone and disappears by the Millerosteus minor + Thursius pholidotus vertebrate biozone. Diplacanthus tenuistriatus and R. longispinus range from the Coccosteus cuspidatus biozone to the end of the Millerosteus minor + Thursius pholidotus biozone. Through comparing the results of our detailed work on the morphology and histology of fin spines and scales from the articulated fish with diplacanthid taxa based on isolated scales and fin spines from the Baltic region, Belarus, and Severnaya Zemlya, we recognize many of the latter taxa from contemporary deposits as junior synonyms of the Scottish species. Phylogenetic analysis of selected gnathostome genera shows the diplacanthiforms Diplacanthus, Rhadinacanthus, Uraniacanthus, and Culmacanthus form a well-supported clade within a larger clade comprising all acanthodian taxa plus a monophyletic Chondrichthyes. © March 2016 Palaeontological Association.


McL Michiet U.,Vine Lodge | Newman M.J.,Vine Lodge | Den Blaauwen J.L.,University of Amsterdam
Scottish Journal of Geology | Year: 2015

Biostratigraphic zones based on fossil fish are identified within the Middle Devonian Rousay sequence in the upper part of the main lacustrine sequence of Orkney. The Rousay sequence forms the majority of the bedrock of Orkney and the original Geological Survey had estimated its thickness to be over 1500 m. Some recent geological investigations have redefined the Rousay sequence and reduced its thickness to such an extent (around 200 m) that the latest (2000) BGS geological map (1:100 000) includes a Rousay Flagstone Member as only an upper member of the Upper Stromness Flagstone Formation. Our new investigations have confirmed that the fossil fish clearly separate the Rousay sequence from the underlying Strom-ness Flags and show that its thickness is over 800 m. The osteolepid fish Osteolepis panderi occurs in a limited zone at the base of the Rousay sequence in a set of two or three fish beds with prolific occurrences of O. panderi and occasional specimens of the osteolepid fish Thursius pholidotus. Above these fish beds, O. panderi becomes extinct within the basin (but may have persisted outside the basin in the marine realm). Several fish beds containing numerous specimens of the coccosteid fish Millerosteus minor, again with occasional specimens of T. pholidotus, occur from about 205 m above the base of the Rousay sequence in a middle unit of the sequence. This unit is about 195 m thick and contains the first significant coarse to pebbly sandstones above the basal transgression of the main lacustrine sequence. Above this sandy member, these fossil fish become extinct within the basin (but may persist outside the basin) and then there are over 400 m of dominantly finer-grained lacustrine strata up to the overlying sandstones of the Lower Eday Sandstone Formation, the lowest formation of the Eday Group. Fossil fish are present in this uppermost part of the Rousay sequence, but do not include Osteolepis panderi or Millerosteus milleri and instead are dominantly of species with long ranges in the flagstone sequence. A poorly defined biozone containing rare individuals of the antiarch, Asterolepis orcadensis, occurs in a limited interval near the top of the lacustrine sequence. Based on the identification of these biozones and their relationship to distinct sedimentary units, we have provisionally identified within the Rousay sequence Lower, Middle and Upper Rousay units, but these are not formally defined as formations. These biostratigraphic zones can be correlated in the equivalent sequence in Caithness, except for the uppermost Aster-olepis orcadensis zone probably because the transition between the lacustrine sequence and the overlying sandstones is not exposed. Equivalent biostratigraphic units, provisionally identified as the Thurso Flagstones, Mey and Huna units, can be directly related in upward sequence to the units recognized on Orkney. By comparison with the position of the first appearance of the spore Geminospora lemurata, which marks the base of the Givetian, the Eifelian/Givetian boundary is interpreted to lie above the Millerosteus minor Biozone. © 2015 The Author(s).

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