Search results for "Devonian"
showing 10 items of 77 documents
Rare Middle and Upper Devonian dalmanelloid (Orthida) of the Cantabrian Mountains, N Spain
2018
Rare Cantabrian Dalmanellidae ( Costisorthis lisae nov. sp.), Dicoelosiidae ( Teichertina cf. peregrina , T. cf. ?tzroyensis ), and Mystrophoridae ( Mystrophora sp., Biernatium suco i nov. sp., and Biernatium sp. 2) are described and ?gured for the ? rst time in Spain. Most of them are scarce forms that occur only in certain localities. All the species but one came from the lower part of the Portilla (province of Leon) and Candas (province of Asturias) formations, Faunal Interval 21, Polygnathus rhenanus/P. varcus conodont zone, middle Givetian. The exception is Biernatium sp. 2 that occurs in Asturias in FI 25, Pineres Fm., Palmatolepis transitans zone, lower Frasnian. Costisorthis ranges …
A new species of Strunius(Sarcopterygii; Onychodontida) from Latvia; Lode quarry (Upper Devonian)
1995
Abstract A new species of the genus Strunius has been found. It is distinct from the other Strunius species; S. rolandi and S. walteri in the shape of the gular and parasymphysial teeth. The sigmoid tooth tips are harpoon-shaped and are similar to those of Onychodus jaekeli. Strunius nov. sp. is more closely related to S. rolandi than to the type-species S. walteri.
The orbito-nasal area ofAsterolepis ornata, a Middle Devonian placoderm fish
2001
The structure of the orbito-nasal cavity in the antiarchan placoderm fish Asterolepis ornata has been studied, providing a detailed description of the premedian, rostral, and pineal plates, and bones of the sclerotic ring. Both eyes and nostrils were directed antero-latero-dorsally in Asterolepis. Eyes were enclosed within the sclerotic capsule. Nasal cavities were not opened into a so called “prenasal slit,” but directly above the head of fish. A new reconstruction of the nasal openings and position of the nasal sacs shows broader similarities between various antiarchs than was previously claimed, and allows the evaluation of the differences in the structure of the orbito-nasal cavities in…
Depositional Environment of the Devonian Quartz Sandstones in the Bāle Sand Pits
2014
This paper summarises data about the depositional environment of Devonian quartz sandstones in Latvia and discusses new fieldwork data from Bāle 1 and Bāle 2 sand pits. The commercial bed in these sand pits is composed of fine to gravel size grained white and pale gray sandstones with mud clasts and quartz pebbles in places. Studies in Bāle sand pit sectors 1 and 2 suggest the deposition of sediments in details channel and sand bars, with the scarce influence of tidal processes on sedimentation.
Ventastega curonica and the origin of tetrapod morphology.
2008
The gap in our understanding of the evolutionary transition from fish to tetrapod is beginning to close thanks to the discovery of new intermediate forms such as Tiktaalik roseae. Here we narrow it further by presenting the skull, exceptionally preserved braincase, shoulder girdle and partial pelvis of Ventastega curonica from the Late Devonian of Latvia, a transitional intermediate form between the 'elpistostegids' Panderichthys and Tiktaalik and the Devonian tetrapods (limbed vertebrates) Acanthostega and Ichthyostega. Ventastega is the most primitive Devonian tetrapod represented by extensive remains, and casts light on a part of the phylogeny otherwise only represented by fragmentary ta…
Machaeracanthus goujetin. sp. (Acanthodii) from the Lower Devonian of Spain and northwest France, with special reference to spine histology
2012
ABSTRACT We describe here a new machaeracanthid acanthodian (Machaeracanthus goujeti n. sp.), based on isolated spines, scales and scapulocoracoids from the Lower Devonian (Lochkovian-Pragian) of the Nogueras Formation, Celtiberia, Spain. The new taxon also includes a fragmentary spine and isolated scales from the Lower Devonian of northern Spain (Palencia and Cantabrian Mountains) and western France (Saint-Cenere) originally assigned to Machaeracanthus sp. The spines of M. goujeti n. sp. comprise two morphotypes in agreement with the morphofunctional model of a pair of pectoral spines articulating with the pectoral girdle already indicated for M. hunsrueckianum Sudkamp & Burrow, 2007, M. l…
Age and origin of the Böllsteiner Odenwald
2001
The granitoid protoliths of the gneisses of the Bollsteiner Odenwald, a part of the Mid German Crystalline Rise, intruded at 405 ± 3 Ma. This age was obtained by single zircon 207Pb/206Pb evaporation measurements. It is supported by an upper discordia intercept age of 410 ± 11 Ma from single zircon U/Pb data. These granitoids were derived from hybrid magmas according to their geochemical characteristics. Inherited zircon grains with apparent ages of 882 and 1138 Ma further constrain the source heterogeneity. The isotope data with Nd model ages for the granitoid gneisses between 1.3 and 1.7 Ga also underline the involvement of Proterozoic material into the magma sources. Since the geochemica…
Taphonomy of the vertebrate bone beds from the Klūnas fossil site, Upper Devonian Tērvete Formation of Latvia
2012
Combined sedimentological and taphonomical study of the siliciclastic sequence of the Tērvete Formation in the stratotypical area was aimed at revealing the formation of the three oryctocoenoses discovered and related structural and textural features of the deposits, as well as at detailed observation of the taphonomical peculiarities of the obtained palaeontological material. The fossil vertebrate assemblage is represented by 14 taxa comprising placoderms, acanthodians, sarcopterygians and actinopterygians. The three oryctocoenoses, first recognized in 2010, differ in the proportions of repeatedly buried material, in the number and degree of preservation of small and fragile skeletal eleme…
Obruchevacanthus ireneae gen. et sp. nov., a new ischnacanthiform (Acanthodii) from the Lower Devonian of Spain
2014
New disarticulated material of typically ischnacanthid scales, tooth whorls, and ?dentigerous jaw bones that occur recurrently together at many levels of the Lower Devonian of the Iberian Chain (Spain) is described. Based on their stratigraphical occurrence, histological evidence and comparison with similar ischnacanthid assemblages from other localities, we suggest including all of these remains in a unique natural assemblage, Obruchevacanthus ireneae gen. et sp. nov. This new taxon shares some features with Trundlelepis cervicostulata from the Lower Devonian of New South Wales (Australia), as for example the presence of a poorly developed pore canal system in their scales. This feature su…
Revision of asterolepidoid antiarch remains from the Ogre Formation (Upper Devonian) of Latvia
2020
The Frasnian (Upper Devonian) antiarch Walterilepis speciosa was first described in 1933 (as Taeniolepis) on the basis of a single specimen. The newly collected material has allowed the head to be described in a more detail, especially the nuchal and paranuchal plates. Other newly described elements include bones of the pectoral appendages and trunk armour, demonstrating a rather high and short trunk armour. The shape and proportions of the head and trunk armour suggest the attribution of Walterilepis to the family Pterichthyodidae; it is most probably closely related to Lepadolepis from the Late Frasnian of Germany. Whilst W. speciosa is endemic to the Latvian part of the Baltic Devonian B…