Zemes un vides zinātnes Earth and Environment Sciences - Latvijas ...

ACTA UNIVERSITATIS LATVIENSIS, 2004, Vol. 679, pp. 99-119
Sedimentology, fauna, and taphonomy of the
Pavāri site, Late Devonian of Latvia
ERVINS LUKšEVIČS and IVARS ZUPIŅš
E. Lukševičs, Department of Geology, University of Latvia, Rainis Blvd 19, Riga LV-1586,
Latvia, Ervins.Luksevics@lu.lv; I. Zupiņš, Natural History Museum of Latvia, K. Barona Str.
4, Riga LV-1712, Latvia, Ivars.Zupins@dabasmuzejs.gov.lv
The distribution, sorting, orientation, state of preservation, and wearing of vertebrate remains
from the upper Famennian (Upper Devonian) Ketleri Formation of the Pavāri site, western
Latvia, have been studied. The vertebrate fauna is dominated by the placoderm, Bothriolepis
ciecere, and includes also acanthodians, several sarcopterygian taxa and the primitive tetrapod
Ventastega curonica. Taxonomic composition, pattern of distribution, sorting, preferred orientation
of vertebrate remains suggest that the assemblage was winnowed by water transport in a low
concentration flow. Nevertheless, an almost total lack of wearing and the high degree of
preservation, including many articulated skeletal parts, indicate short transportation of the remains
before burial. An almost autochtonous character of the oryctocoenosis is, therefore, suggested.
Sedimentological and taphonomic studies of the locality suggest that it was formed in relatively
shallow sea conditions dominated by stream and weak wave influence, probably representing a
low-tidal near-shore depositional environment. Most likely, vertebrates from the Ketleri Formation
dwelled in a marine coastal environment, although the possibility that the remains have been
transported for a considerable distance can not be excluded.
Key words: Palaeoecology, placoderms, sarcopterygians, tetrapods, Famennian.
Introduction
The environmental conditions in habitats of early tetrapods and the palaeoecological
aspects of the origin of tetrapods are still disputable problems of vertebrate evolution
(Thomson 1980; Spjeldnæs 1982; Bendix-Almgren et al. 1990; Coates and Clack 1995;
Lebedev, this volume). Studies on taphonomy in fossil vertebrate sites using both
sedimentological and bionomic data is one of the methods that can provide some clues
to the problem. This study concerns the sedimentological, environmental and taphonomic
context of the locality known as the Pavāri (or Ciecere) site in western Latvia. This is
one of the well-known sites where the primitive tetrapod Ventastega curonica has been
found together with abundant fish remains in a sandstone of the upper Famennian (Upper
Devonian) Ketleri Formation.
The stratigraphy and fossils of the Ketleri Formation have attracted the interest of
geologists and palaeontologists for more than 70 years (Gross 1942; Lyarskaya and
Savvaitova 1974; Vorobyeva 1962, 1975; Lukševičs 1992; Lebedev and Lukševičs
1996). This interest has grown significantly in recent years after the discovery of the
first tetrapod fossils from the Ketleri Formation (Ahlberg, Lukševičs and Lebedev 1994;
Ahlberg and Lukševičs 1998; Lukševičs, Ahlberg and Clack 2003). Vertebrate fossils