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

E. Lukševičs, I. Zupiņš. Sedimentology, fauna, and taphonomy of Pav āri
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Fig. 5. Bipolar orientation of the cross-bedding of the
infilling sandstone (layer No. 6). N = 30.
of skulls have also been found, particularly in slump depressions or close to slumping
structures. Fossils are rarely found close to the margins of the supposed erosional canal;
mainly scales of sarcopterygians have been collected there. Fish and tetrapod remains
are usually brown or dark brown, rather soft and fragile, therefore many specimens
kept in the museum collection bear cracks, as the results of breakage during transportation
in the plaster jackets or during preparation.
Fossil assemblage. Of the more than 1000 specimens collected from the Pavāri site,
909 have been identified to the generic/species level. About 800 specimens are housed
at the LDM. Identified taxa from the Pavāri site are listed in the Table 1, and persentages
of each taxon are shown in the Table 2 and Figure 6.
Taxonomic representation. The fossils assemblage from the Pavāri site seems to be
taxonomically incomplete, lacking the remains of arthrodires, ptyctodonts and
chondrichthyans. Actinopterygian remains are extremely rare, including only one small
incomplete scale ever found. Arthrodires are known from the underlying beds of the
Žagare Formation, while ptyctodonts and actinopterygians have been found in the
Nīgrande Member of the Ketleri Formation (Gross 1933, Lyarskaya and Savvaitova
1974). Chondrichthyan remains are in general rare in Baltic Devonian deposits (Ivanov
and Lukševičs 1994; Mark-Kurik and Karatajūte-Talimaa 2004). From the Famennian
deposits they have so far been found only in dolostones of the Kursa Formation and
sandstones of the Mūri and Tērvete formation (both are older than the Ketleri Formation).
Underrepresentation of small fish or small skeletal parts of fish bodies are common
features of fossil assemblages and is usually interpreted as a combination of biotic and
abiotic factors that destroy or remove small, delicate bones (Behrensmeyer 1991).
Possibly the absence of ptyctodonts, chondrichthyans and actinopterygians in the material
from Pavāri can be explained by the small size of the armour plates of ptyctodonts,
scales and teeth of chondrichthyans and actinopterygian scales, although the possibility
that this part of the Baltic sedimentary basin was not suitable for the existence of these
fishes during the Ketleri time can not be excluded. Considering the presence of
acanthodian scales one should note their much smaller size comparable with that of the
sand grains.
Material from the Natural History Museum of Latvia (collection No LDM G 81),
collected in 1970, 1973 and 1995, has been used for comparison of the percentage of