[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Weberepeton, new stem tetrapod from Devonian of Russia + non-dino papers



Ben Creisler
bcreisler@gmail.com


A number of recent non-dino papers that may be of interest to some:


Weberepeton

G. Clément &  O. Lebedev (2014)
Revision of the early tetrapod Obruchevichthys Vorobyeva, 1977 from
the Frasnian (Upper Devonian) of the North-western East European
Platform.
Paleontological Journal 48(10): 1082-1091
DOI: 10.1134/S0031030114100037
http://link.springer.com/article/10.1134/S0031030114100037



Species composition of the genus Obruchevichthys Vorobyeva, 1977,
previously based on two specimens from the Upper Frasnian (Upper
Devonian) of Latvia and Leningrad Region of Russia is revised. The
precise locality of the latter specimen was considered by the author
of this taxon as unknown. Archives recently found in collection and
field research in the presumable locality allowed the rediscovery of
this important locality along the Sondala River (east of the Leningrad
Region). This provenance is furthermore supported by spectrometric
testing. Despite the presence of several subadult features hindering
its attribution by earlier authors to a separate taxon, new
observations on its morphology revealed that several characters of the
material from Russia significantly differ from those of the type
specimen that resulted in its attribution to a new genus and species
Weberepeton sondalensis gen. et sp. nov. These differences mainly
consist in a number of lower jaw characters, such as relative size of
marginal teeth, development rate of the adsymphysial plate,
orientation of the precoronoid fossa, and dermal ornamentation.

==


D. N. Mednikov (2014)
Urodelans, Ichthyostega and the origin of the tetrapod limb.
Paleontological Journal 48(10): 1092-1103
DOI: 10.1134/S0031030114100074
http://link.springer.com/article/10.1134/S0031030114100074


Available information on the development of primitive urodele
(Hynobiidae) limbs and limb structure in Devonian tetrapods provide
the basis for formulating the hypothesis on the existence of a special
phase, the phase of the biserial limb in tetrapod history. The limb of
the Devonian amphibian Ichthyostega with two groups of digits,
preaxial and postaxial, corresponds well to this phase. Based on the
structure of the Ichthyostega limb, it is suggested that the fin type
ancestral to terrestrial limbs was asymmetrical biserial, possessed a
short axis, unbranched jointed preaxial radials deviating one by one
from each mesomere of the axis, and unbranched jointed postaxial
radials deviating from the distal mesomeres of the axis in two or more
radials.


===



Pavel P. Skutschas (2014)
A relict stem salamander: Evidence from the Early Cretaceous of Siberia.
Acta Palaeontologica Polonica (in press)
doi:http://dx.doi.org/10.4202/app.00124.2014
http://app.pan.pl/article/item/app001242014.html


The early evolution of salamanders, which are one of the three living
groups of lissamphibians, is not well known. Both stem- and
crown-group salamanders first appeared in the Middle Jurassic
(Bathonian), but subsequently had different evolutionary histories:
stem salamanders were thought to have gone extinct in the Late
Jurassic, while crown salamanders persist to the present day. Here, I
report the discovery of an indeterminate stem salamander in the Lower
Cretaceous (Aptian–Albian) Ilek Formation of Western Siberia. This is
new evidence that the most basal salamanders survived beyond the
Jurassic–Cretaceous boundary and co-existed with crown-group
salamanders during approximately the first 40 million years of the
known history of salamanders. The recognition of stem salamanders in
the Early Cretaceous of Western Siberia adds to the inventory of taxa
that suggest this area was a refugium for various groups of
vertebrates with Jurassic affinities.


=======

N. I. Krupina & A. A. Prisyazhnaya (2014)
A new dipnoan from the Middle Devonian (Givetian) of Central Russia.
Paleontological Journal 48(10): 1077-1081
DOI: 10.1134/S0031030114100049
http://link.springer.com/article/10.1134/S0031030114100049



A new dipnoan species, Dipnotuberculus bagirovi sp. nov.
(Dipnoiformes, Dipnorhynchidae), is described based on an incomplete
palatal part of the skull from the Upper Givetian (Middle Devonian) of
the Pavlovsk (Shkurlat) quarry in the Voronezh Region of Central
Russia. This is the first discovery of dipnoan material in the Middle
Devonian of the Central Devonian Field of Russia and the first record
of Dipnorhynchidae of this age within the Baltic paleozoogeographical
Province. Distribution analysis of this family supported by general
zoogeographical faunistic analysis suggests the dipnorhynchid
dispersal from Gondwana to Laurussia via Armorican faunistic province.


===


Torsten M. Scheyer, Leonhard Schmid, Heinz Furrer & Marcelo R.
Sánchez-Villagra (2014)
An assessment of age determination in fossil fish: the case of the
opercula in the Mesozoic actinopterygian Saurichthys.
Swiss Journal of Palaeontology (advance online publication)
DOI: 10.1007/s13358-014-0068-4
http://link.springer.com/article/10.1007/s13358-014-0068-4



Analyzing and interpreting life history data (e.g., aging and
longevity, age at sexual maturity) are fundamental in many
paleontological studies. In the case of extant and fossil fishes,
otoliths, and to a lesser degree other incrementally growing hard
tissue structures such as scales and bones, have been utilized to
reveal these data. We investigated the microanatomy and internal
microstructure of opercula of Saurichthys, one of the most easily
recognized and globally distributed fishes in the Triassic, to
elucidate whether these prominent skull bones provide reliable age
estimates. Opercula, and where the subopercula is present, of several
outgroup taxa were sectioned to provide a phylogenetic framework for
the study. The external protrusions and ridges or internal concentric
bands or wrinkles are not related to internal age-related bone tissue
structures such as annuli and growth zones, but are instead purely
ornamental in the case of the former and probably
structural/taphonomic in case of the latter. Opercular morphogenesis
of Saurichthys opercula differs from that of the extant outgroups
examined in that they show rostro-medial to caudo-lateral extending
growth increments instead of ones that extend sub-parallel to the
opercular bone surfaces. Individual age data could thus not be
reliably extracted from those opercula. Furthermore, an odontode-like
complex was not encountered in Saurichthys opercula, but a few
specimens show a peculiar, weakly birefringent thin tissue layer of
unknown origin filling the valleys between the external ornamental
ridges. Although all Saurichthys opercula showed growth marks, these
could not be counted to produce reliable individual age data, whereas
bones with a more concentric cross section, such as the ceratohyal,
appear better suited for this purpose.

===