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Burrows of Enteropneusta in Muschelkalk (Middle Triassic) of the Holy Cross Mountains, Poland

100%
Kazmierczak J., Pszczolkowski A.
Acta Palaeontologica Polonica
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1969
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tom 14
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nr 2
Traces of burrowing organisms from Lower Muschelkalk carbonate sediments of the Holy Cross Mountains (Góry Świętokrzyskie) interpreted as burrow systems of enteropneusts, have been described. Morphological and palaeoecological analysis of Triassic forms based on the comparison with the burrows of Recent enteropneusts is given. The presence of many horizons with burrows of enteropneusts in the profiles of the Lower Muschelkalk deposits (Łukowa beds) and the lithological characters of these deposits seem to indicate that the sedimentation took place in a zone of the basin affected by the activity of tidal currents.
2
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Using abundance data to assess the relative role of sampling biases and evolutionary radiations in Upper Muschelkalk ammonoids

100%
McGowan A. J., Kiessling W.
Acta Palaeontologica Polonica
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2013
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tom 58
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nr 3
The Middle Triassic ammonoid genus Ceratites diversified spectacularly within the Germanic Muschelkalk Basin during the Anisian/Ladian (244–232 Mya). Previous studies have interpreted this diversification as a sequence of rapid, endemic radiations from a few immigrant taxa. Here we investigate the possibility that geological and sampling biases, rather than ecological and evolutionary processes, are responsible for this pattern. A new specimen−based dataset of Ceratites species−richness and abundance was assembled. This dataset was combined with 1:200 000 geological maps in a geodatabase to facilitate geospatial analyses. One set of analyses compared species richness per geological map with the number of occurrences and localities per map. Per−map change in the amount of rock available to sample for fossils was also included as a variable. Of these three variables, number of occurrences is the most strongly correlated with richness. Variation in the amount of rock is not a strong determinant of species−richness. However, rarefaction of basin−wide species/abundance data demonstrates that differences in species−richness through time are not attributable to sample size differences. The average percent similarity among sites remained close to 50% throughout the Upper Muschelkalk. The rank abundance distribution (RAD) of species from the first interval of the Upper Muschelkalk is consistent with colonization of a disturbed environment, while the other two intervals have RADs consistent with more stable ecosystems. These results indicate that genuine ecological and evolutionary events are partly responsible for the observed differences in richness and abundance. Although changes in the RADs through time support changes in the ammonoid assemblage structure, the processes underlying increasing richness and change in RADs cannot be explained by increasing geographic distinctiveness or isolation among the ammonoid assemblages present at different localities.
3
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Functional morphology and taphonomy of nautiloid beaks from the Middle Triassic of Southern Germany

70%
Klug C.
Acta Palaeontologica Polonica
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2001
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tom 46
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nr 1
New records of nautiloid beak elements conventionally classified as 'Rhyncholithes hirundo (Biguet, 1819)' and 'Conchorhynchus avirostris (von Schlotheim, 1820)' with carbonised (originally chitinous) three-dimensionally preserved appendages from the Upper Muschelkalk (Middle Triassic) of northern Württemberg (Southwest Germany) enable restoration of the complete beak of Germanonautilus. In three specimens, the lower mandible is embedded within the living chamber of Germanonautilus conchs, Beak elements of Germanonautilus differ from those of Recent Nautilus in the more elongate appendages of the fossil lower mandibles and the weaker sculpture on the originally chitinous parts. Furthermore, the dorsal sculpture of the fossil conchorhynchs consists of ridges rather than denticles and the ventral sculpture of the fossil rhyncholiths displays ridges in places where the Recent rhyncholiths have a smooth surface. Additionally, the fossil beak elements attained a larger size than their Recent counterparts, During transport of 'Rhyncholithes hirundo', the light chitinous parts served as a sail and the heavier conchorhynch anchored in the sediment causing alignment. In contrast to the irregularly embedded isolated rhyncholiths, the conchorhynchs usually settled with their ventral side up. From the study of 407 fossil nautiloid beak-elements, a significant variability of the hard parts is evident. Consequently, the assignment of specific morphologies to the species of Germanonautilus is impossible.
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