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

E. Lukševičs, I. Zupiņš. Sedimentology, fauna, and taphonomy of Pav āri
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and Cryptolepis grossi could also give satisfactory results since they are represented
by many skeletal elements. It is, however, impossible to use the other taxa due to the
insufficient number of specimens.
Disarticulated bones of the trunk and head shield of Bothriolepis ciecere are
represented in different numbers. Strongly convex dorsolateral and ventrolateral bones,
particularly posterior ventral lateral plates from the left side (PVL) and mixilateral
plates from the right side (MxL), dominate among the trunk shield bones (Tab. 3).
Possibly these bones, along with the less convex anterior median dorsal (AMD), could
belong to the Voorhies Group III, being the most resistant to transport. The number of
the anterior ventro-lateral (AVL) and anterior dorso-lateral (ADL) plates is smaller,
and the almost flat posterior median dorsal (PMD) and flat median dorsal (MV) are the
rarest among the trunk shield bones, representing the Voorhies Group II, which is
moderately readily transported. Besides that, the distribution of paired convex bones
shows assymetry. The number of the right-sided MxL plates more than three times
exceeds the number of the left-sided MxL, but the situation is opposite in the case of
PVL plates. The number of the left-sided PVL two times exceeds the number of the
right-sided PVL. The differences between various Voorhies groups and number of bones
from the right and left side of the trunk suggest quite an important hydraulic sorting of
skeletal elements of placoderms. Bones of the head shield are also represented in different
numbers, always being more rare than the trunk shield plates. Thick and relatively large
lateral (La) and nuchal (Nu, n = 17) plates, as well as complete head shields, are found
comparably often. Still, articulated head shields, which supposedly could represent the
Voorhies Group III, are disproportionally rare. Separate premedian (Prm, n = 2) and
other small and thin bones are very rare. Such very thin and small bones as inferognathals
and submarginals, as well as bones of sklerotic ossifications, were not found. Possibly
the lightest bones were readily transported soon after death.
Table 3. Number of some skeletal elements of placoderm fish Bothriolepis ciecere
* Unpaired bones and shield