Taphonomy of the vertebrate bone beds from the Klūnas fossil site, Upper Devonian Tērvete Formation of Latvia

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 elements, as well as in the evaluated current velocity and the transportation distance. Sedimentary concentrations of marine vertebrate remains, dominated by the antiarchs Bothriolepis ornata and B. jani, have been formed under the influence of fluvial and tidal processes in the shallow-water environment, deltaic or estuarine settings. Elongated placoderm and sarcopterygian bones are probably better indicators of the palaeoflow direction than acanthodian spines or sarcopterygian teeth

Osteolepiform sarcopterygian fishes (Sarcopterygii, Osteolepiformes) of the Main Devonian Field

GALVENĀ DEVONA LAUKA OSTEOLEPIFORMU KĀRTAS DAIVSPURZIVIS (SARCOPTERYGII, OSTEOLEPIFORMES) Ivars ZupiĦš ANOTĀCIJA Revidēts osteolepiformu kārtas daivspurzivju taksonomiskias sastāvs un stratigrāfiskā izplatība Galvenā devona lauka (Austrumeiropas platformas ziemeĜrietumu daĜas) teritorijā. Kritiski izvērtēts morfoloăisko pazīmju kopums un sniegtas sugu precizētas diagnozes. Konstatēts, ka darbā apskatāmajā teritorijā kārta pārstāvēta ar 16 sugām, kas pieder 9 ăintīm. Aprakstīta jauna tristihopterīdu suga Eusthenopteron kurshi sp. nov., izvērtējot osteolepiformu iespējamo pielietojamību devona nogulumu biostratigrāfijā, konstatēts, ka grupai ir zināma nozīme kā vienam no mugurkaulnieku faunas kompleksu elementiem līdzās biežāk pieejamam bruĦuzivju un bezžokleĦu materiālam, ko pierāda korelācijas piemēri, salīdzinot Galvenā devona lauka, Skotijas un Centrālā devona lauka griezumus. Analizēti daivspurzivju tafonomijas aspekti īpaši pievēršoties Lodes mālu karjerā konstatēto fosiliju sakopojumu veidošanās apstākĜiem.Osteolepiform sarcopterygian fishes (Sarcopterygii, Osteolepiformes) of the Main Devonian Field ANNOTATION The diversity and stratigraphical distribution of osteolepiform sarcopterygians from the Main Devonian Field (north-western part of the East European Platform) are analysed. Morphological characters have been critically evaluated and amended diagnoses are given. It is concluded that the order is represented by 16 species, which belong to 9 genera. A new species of tristichopterids, Eusthenopteron kurshi sp. nov., is described. Evaluation of the potential application of the osteolepiforms in biostratigraphy shows that the group has certain value as elements in Devonian vertebrate assemblages along with the more frequently available placoderm and agnathan material as approved by the correlation examples between the sequences of the Main Devonian Field, Scotland and the Central Devonian Field. Certain aspects of sarcopterygian taphonomy have been discussed paying special attention to the fossil accumulations in the Lode clay quarry and their formation conditions

Palaeoichthyological investigation in the Luga area of Leningrad Region: past and present

A list of Devonian vertebrates from the Luga District of the Leningrad Region (Russia) was originally mentioned by P. N. Venyukov (1884). However, detailed palaeoichthyological studies in this territory started in only during 1926-1931 in the framework of the geological mapping programme. Two field crews studied the sections of the Middle and Upper Devonian by the Luga, Lemovzha, Oredezh, Tesovaya and Vruda rivers. One of the teams was the Devonian Lithological expedition under guided by R. F. Hecher. D. V. Obruchev was also involved in the works of this expedition. Other team headed by B. P. Asatkin surveyed the western part of the Leningrad Region. Both teams sampled numerous outcrops and boreholes, and collected abundant vertebrate remains. As a result the Devonian deposits were subdivided into the regional beds characterized by diverse vertebrate assemblages. Collectioning and research of Devonian vertebrates in this area continued in the 1950-1960ties by D. V. Obruchev and his students: V. N. Karatajute-Talimaa, E. Mark-Kurik, L. A. Lyarskaya. Their descriptions of Eifelian-Frasnian agnathans and fishes were published in the series of monographs or papers (e.g. Karatajute-Talimaa, 1963, Obruchev & Mark-Kurik, 1965, Lyarskaya, 1981). During the last thirty years J. Valiukevicius and some of the authors of the present report supplemented the vertebrate collections from some sections. The new localities in this area were reported by the 2001 Latvian-Russian Expedition (A. Ivanov, E. Luksevics, I. Zupins and others). The 2009-2010 Russo-Franco-Latvian expedition discovered a new diverse material from the historical and new localities of that area.Origin, ecology and environments of the earliest tetrapods from the Upper Devonian (Frasnian) and paleogeography in the Eastern "Old Red Sandstone Continent"

2009-2010 Russo-franco-latvian expeditions in the Main Devonian Field (North-western Russia)

In the frame of an international project between the Paleontological Institute of Moscow and the Museum of Paris, a Russo-Franco-Latvian team has been set up to prospect the Main Devonian Field in North-Western Russia (Novgorod and Leningrad Regions). This joined project started in 2009 (one month of field trip), continued in 2010 (one month also) and will end in 2011. The two first years were mainly devoted to the prospecting of historical localities, some discovered and/or exploited by Dmitry Obruchev himself. Such a method is effective but quite time-consuming; i.e. to rediscover the accurate location of the localities by discussing with denizens, to fathom the archives out and to access to non-weathered layers by removing the altered surface. Novgorod and Leningrad Regions are topographically excessively flat. Devonian fields have not been disrupted by tectonic movements and the layers are thus horizontal. Rocks are most often quite unconsolidated (consisting of loose sands or clays) and excavations are thus relatively easy. The lack of relief and the vegetal cover unfortunately lead to few outcrops in the landscape. They are all located along rivers (Lovat’, Syas' and Oredesh rivers for instance) or are represented by outliers. Although most of the localities were easily accessible by cars, others required several kilometers by feet and/or by boat. Roughly 30 localities have been prospected. About one third of them are very interesting such as Borshovo and Goryn' (Luga District) which provided numerous and exquisite fossils of placoderms, agnathans and sarcopterygians. The original locality of the Frasnian tetrapod Obruchevichthys in Russia, Sondala (Leningrad Region), has been rediscovered with near certainty.Origin, ecology and environments of the earliest tetrapods from the Upper Devonian (Frasnian) and paleogeography in the Eastern "Old Red Sandstone Continent"

Ventastega curonica and the origin of tetrapod morphology

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 taxa: it illuminates the origin of principal tetrapod structures and the extent of morphological diversity among the transitional form