A new genus of Devonian tetrapod from North-East Greenland, with new information on the lower jaw of Ichthyostega (original) (raw)
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Taxonomic revision of the Late Devonian tetrapod Ichthyostega from East Greenland
Palaeontology, 2005
Two morphologically distinct assemblages of the Late Devonian tetrapod Ichthyostega from East Greenland are described on the basis of a large collection of skulls and postcranial elements. Skull specimens collected on Gauss Halvø show that the assemblage from the lower Aina Dal Formation has proportionally narrower skulls and finer skull roof sculpture than the assemblage from the higher Britta Dal Formation. The assemblages are compared with the stratigraphically unconstrained type material from the north side of Celsius Bjerg on Ymer Ø, allowing a taxonomic revision. From the original description of seven taxa, three species are recognized and related to the assemblages from Gauss Halvø. I. stensioei is comparable with the Aina Dal Formation assemblage while I. eigili and I. watsoni are valid for specimens found in the Britta Dal Formation. Ichthyostegopsis wimani is not a valid genus or species and may be regarded as a juvenile I. eigili. This example of species-level variability is the earliest known from the fossil record of early tetrapods.
A review of Palaeozoic and Mesozoic tetrapods from Greenland
Bulletin of the Geological Society of Denmark, 2018
This article presents a synthesis of Palaeozoic and Mesozoic fossil tetrapods from Greenland, including an updated review of the holotypes and a new photographic record of the main specimens. All fossil tetrapods found are from East Greenland, with at least 30 different known taxa: five stem tetrapods (Acanthostega gunnari, Ichthyostega eigili, I. stensioi, I. watsoni, and Ymeria denticulata) from the Late Devonian of the Aina Dal and Britta Dal Formations; four temnospondyl amphibians (Aquiloniferus kochi, Selenocara groenlandica, Stoschiosaurus nielseni, and Tupilakosaurus heilmani) from the Early Triassic of the Wordie Creek Group; two temnospondyls (Cyclotosaurus naraserluki and Gerrothorax cf. pulcherrimus), one testudinatan (cf. Proganochelys), two stagonolepids (Aetosaurus ferratus and Paratypothorax andressorum), the eudimorphodontid Arcticodactylus, undetermined archosaurs (phytosaurs and both sauropodomorph and theropod dinosaurs), the cynodont Mitredon cromptoni, and thre...
Vertebrate remains from the Upper Silurian-Lower Devonian of North Greenland
1998
Cover Transitional scale of Thulolepis striaspina gen. et sp. nov., a new small thelodont species from the lowermost Devonian of North Greenland. SEM photograph of the holotype, MGUH VP 3510, found in an acetic acid residue of GGU sample 319264. The sample is from a limestone bed in the Chester Bjerg Formation at the top of Monument, an inselberg-like hill in central Hall Land (see Fig. 1). Length of the scale is 0.26 mm.
Bulletin of the Geological Society of Denmark
dk/publikationer/bulletin). Vertebrate micro-remains of jawless vertebrates (psammosteid heterostracans) and gnathostomes (acanthodians and sarcopterygians) occur in a residue collected from the Late Devonian Kap Graah Group sandstones of East Greenland. Fragmentary and isolated elements of psammosteids are assigned to Psammosteus sp. The acanthodians are represented by scales of acanthodiform type and poorly preserved fin spines. Tooth and scale fragments of sarcopterygians may suggest a porolepiform affinity. This assemblage and the associated macro-vertebrate fauna indicate a Frasnian age for an otherwise assumed Famennian part of the East Greenland succession, and do rather effectively bracket the Frasnian-Famennian boundary.
The smallest known Devonian tetrapod shows unexpectedly derived features
Royal Society Open Science
A new genus and species of Devonian tetrapod, Brittagnathus minutus gen. et sp. nov., is described from a single complete right lower jaw ramus recovered from the Acanthostega mass-death deposit in the upper part of the Britta Dal Formation (upper Famennian) of Stensiö Bjerg, Gauss Peninsula, East Greenland. Visualization by propagation phase contrast synchrotron microtomography allows a complete digital dissection of the specimen. With a total jaw ramus length of 44.8 mm, Brittagnathus is by far the smallest Devonian tetrapod described to date. It differs from all previously known Devonian tetrapods in having only a fang pair without a tooth row on the anterior coronoid and a large posterior process on the posterior coronoid. The presence of an incipient surangular crest and a concave prearticular margin to the adductor fossa together cause the fossa to face somewhat mesially, reminiscent of the condition in Carboniferous tetrapods. A phylogenetic analysis places Brittagnathus crow...
A near-tetrapod from the Baltic Middle Devonian
Palaeontology, 2000
The tetrapodomorph sarcopterygian Livoniana multidentata gen. et sp. nov. is described on the basis of lower jaw fragments from the Middle Devonian(late Givetian) of Latvia and Estonia. It possesses a suite of derived characters previously only known from tetrapods, which first appear in the late Devonian (late Frasnian), and a phylogenetic analysis places it on the internode between Panderichthys and the base of the Tetrapoda. The analysis also reveals that the ‘Elpistostegalia’ are paraphyletic to Tetrapoda, with Elpistostege closer to tetrapods than is Panderichthys. Owing to incompleteness of the material, there is almost no overlap between the data sets for ElpistostegeLivoniana; the analysis places the two genera in an unresolved trichotomy. In addition to the tetrapod features, Livoniana has a strikingly autapomorphic dentary dentition comprising multiple tooth rows. It thus provides evidence both for the unexpectedly early evolution of tetrapod characteristics and for morphological radiation around the fish-tetrapod transition.
Palaeontology, 2016
The origin of tetrapods is one of the key events in vertebrate history. The oldest tetrapod body fossils are Late Devonian (Frasnian–Famennian) in age, most of them consisting of rare isolated bone elements. Here we describe tetrapod remains from two Famennian localities from Belgium: Strud, in the Province of Namur, and Becco, in the Province of Liège. The newly collected material consists of an isolated complete postorbital, fragments of two maxillae, and one putative partial cleithrum, all from Strud, and an almost complete maxilla from Becco. The two incomplete maxillae and cleithrum from Strud, together with the lower jaw previously recorded from this site, closely resemble the genus Ichthyostega, initially described from East Greenland. The postorbital from Strud and the maxilla from Becco do not resemble the genus Ichthyostega. They show several derived anatomical characters allowing their tentative assignment to a whatcheeriid-grade group. The new tetrapod records show that there are at least two tetrapod taxa in Belgium and almost certainly two different tetrapod taxa at Strud. This locality joins the group of Devonian tetrapod-bearing localities yielding more than one tetrapod taxon, confirming that environments favourable to early tetrapod life were often colonized by several tetrapod taxa.
Early Cretaceous brachiopods from North-East Greenland: Biofacies and biogeography
Bulletin of the Geological Society of Denmark 52, 213-225, 2005
Augmentation and revision of the relatively diverse Valanginian brachiopod faunas from North-East Greenland confirms the existence of two mutually exclusive but broadly coeval assemblages, associated with two contrasting facies types. A Boreal, relatively shallow-water assemblage dominated by large terebratulids and ribbed rhynchonellids, including Cyrtothyris, Lamellaerhynchia and Praelongithyris characterizes the Falskebugt fauna. By contrast the Albrechts Bugt and Rødryggen fauna contains Tethyan elements, more typical of deeper water, including Lacunosella, Placothyris, Pygope and Rugitela. This early Cretaceous Out-of-Tethys migration confirms the early and persistent northward track of a proto Gulf Stream current. A new taxon, Placothyris kegeli, is described from the Albrechts Bugt and Rødryggen members of the Palnatokes Bjerg Formation