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Journal
of Vertebrate Paleontology
21, 625-627 (2001). Jerzy
Dzik Abstract. A new locality in the middle Keuper marly
clays with excellently preserved tetrapod skeletons was discovered at Krasiejów
near Opole, southern Poland. It has yielded abundant cranial and postcranial
material of metoposaur and capitosauroid labyrinthodonts, phytosaurs,
aetosaurs, and undetermined archosaurs. Based on the position of the Krasiejów
fossiliferous horizon in the lithostratigraphic column, it seems to be coeval
to the Lehrberg beds in Germany, which probably terminate the Carnian
sedimentary cycle. The initial part of the cycle in Germany is the
Schilfsandstein, a local rock equivalent of which is represented about 80 m
below in boreholes drilled in the area. The labyrinthodont Metoposaurus found at Krasiejów is conspecific with, or at least
closely related to, M. diagnosticus,
occurring in these strata in Germany. The phytosaurs from Krasiejów confirm
such age determination. They belong to a species of Paleorhinus, geologically the oldest and anatomically the least
derived of phytosaurs. The co-occurrence of Paleorhinus
with Metoposaurus indicates that the
Krasiejów fauna chronologically belongs to the Late Carnian part of the Paleorhinus biochron.
Paleorhinus is represented in the
material from Krasiejów by several skulls, more or less fragmentary
articulated postcranial skeletons and numerous isolated bones. Individuals of
various ontogenetic stages are represented, forming an ontogenetic series. The
Krasiejów fossil assemblage is dominated by skeletons of semiaquatic
amphibians and reptiles, but less numerous bones of strictly terrestrial
reptiles are also represented. Among them there is an aetosaur species. Its
isolated scutes are closely similar to those of Stagonolepis.
A few archosaurian bones of undetermined affinities (same of relatively large
size) have been found at Krasiejów. Among them of special interest seems to
be a small second sacral vertebra with a flat anterior surface of the centrum.
Unlike sacrals of the associated phytosaurs and aetosaurs, as well
as Ornithosuchus, it bears very
short and deep ribs. This indicates a rather narrow pelvic girdle, unusually
narrow as for early archosaurs. Such sacra are known among the herrerasaurid
dinosaurs. The second sacral vertebra of Staurikosaurus and
Chindesaurus resemble the Krasiejów specimen especially close in their
short ribs with vertically extended bases. Whether this is truly a member of
the herrerasaurid lineage remains unknown until more complete material is
found. The occurrence of a diverse tetrapod assemblage with Paleorhinus
and Metoposaurus in Silesia extends much eastward its known distribution
within the Germanic Basin and improves the Late Triassic age correlation in
this part of Europe. Early dinosaurs may be represented in the assemblage
which makes it of special importance. |