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New materials on Ventalepis ketleriensis Schultze, 1980 extend the zoogeographic area of a Late Devonian vertebrate assemblage

Lebedev O., Lukševičs E.

Acta Geologica Polonica

2018

Vol. 68, no. 3

437--454

Newly collected and restudied earlier materials on an enigmatic fish Ventalepis ketleriensis Schultze, 1980 from the upper Famennian (postera – ? Lower expansa conodont zones) of Latvia and central and northwestern Russia support its porolepiform affinities. A new family Ventalepididae fam. nova is established for this genus upon a peculiar combination of characters, including scale structure and dermal bones ornamentation. New records extend the distribution of this genus and the Ventalepis vertebrate assemblage on the whole to a vast geographical zone along the south-eastern coast of the Old Red Sandstone continent. The habitat area of the Devonian vertebrate assemblage over such a large territory within the zoogeographical province of Baltica is established for the first time. Palaeozoogeographical analysis suggests Laurentian affinities of the Ventalepis assemblage demonstrating the major congruency to the Belgian and East Greenland ones. These and Russian localities are separated by a vast ORS continent. Presence of the dipnoan Jarvikia in all three locations, as well as an Ichthyostega-like tetrapod in the Belgian one reveals palaeozoogeographical connections, which might reflect possible dwelling not only in the near-shore continent periphery but also in the river systems of the continent itself.

Geology and taphonomy of the base of the Taquaral Member, Irati Formation (Permian, Paraná Basin), Brazil

Chahud A., Petri S.

Acta Geologica Polonica

2015

Vol. 65, no. 3

379--387

The taphonomy of Early Permian vertebrates from a sandy facies at the base of the Taquaral Member, Irati Formation, was surveyed in order to acquire data for the interpretation of the sedimentary processes and paleoenvironment of deposition. Six outcrops from the Rio Claro municipality and surrounding areas, from the Brazilian State of São Paulo, were investigated. The vertebrate groups are Chondrichthyes (Xenacanthiformes, Ctenacanthiformes and Petalodontiformes), Osteichthyes (Actinopterygii and Sarcopterygii) and Tetrapodomorpha. They occur as loose teeth, scales, spines and bone remains. The sandy facies is characterized by fining upward deposition. The coarser sandstone immediately above the underlying Tatuí Formation is rich in Chondrichthyes. However, the fine sandstone above, immediately beneath the silty shale facies, is devoid of Chondrichthyes, though Osteichthyes scales, teeth and bones were present. The taphonomy is important for inferring sedimentary processes and then the paleoenvironments. The poor sorting of the sandstone and the presence of fossils that are mostly abraded or worn are indicative of a high energy environment. In contrast, the presence of fossils in a good state of preservation, some without abrasion and breakages are indicative of only limited transport. Differences of fossil spatial density, numbers of specimens and taxa may be explained by the dynamics of deposition, from details of the palaeoenvironment can be obtained.