A taxonomical and statistical study of chitinozoan distribution across the lundgreni Event (Wenlock, Silurian) from the Prague Basin, Czech Republic: A specific pattern driven by ecological changes
Abstrakt
The nature and relation of the graptolite lundgreni Event and the conodont Mulde Event in the mid-Homerian and the ensuing development of atmospheric-oceanic models for the whole Silurian has been a matter of debate for several decades. Chitinozoans represent a promising tool in the correlation of graptolite and conodont biozonation, however, their dynamics through the mid-Homerian must first be well constrained.
Based on supposed changes in chitinozoan faunas described in earlier studies from the Prague Basin, a continuous section ranging through the lundgreni Event has been selected and the chitinozoan content was investigated taxonomically and statistically for a detailed faunal dynamic study. Although the moderate to bad preservation of chitinozoans hinders the taxonomic work, an exceptionally diverse chitinozoan population has been observed.
The range through assumption compiled with data from other areas showed only two widespread species to disappear near the lundgreni Event: Cingulochitina cingulata and Margachitina margaritana. The statistical evaluation of chitinozoans indicates only minor changes in chitinozoan dynamics across the section.
The differences in development of generic and specific richness and dominance is interpreted as being related to chitinozoans with selective ecological dependence, interpreted as a result of changes in environmental conditions during the mid-Homerian period. This pattern is in concordance with the results of a relative change test of the chitinozoan population and is more similar to the pattern of conodont faunal dynamics, rather than graptolite faunal dynamics during the mid-Homerian.