Lower Kimmeridgian echinoids of Poland

Urszula Radwańska

Abstract


A rich assemblage of echinoids, primarily regular ones, is reported from the Lower Kimmeridgian part of an over 1km thick Upper Jurassic carbonate sequence, developed over cratonic (epicontinental) areas of Poland (Holy Cross Mountains in Central Poland, and Western Pomerania in NW Poland). The echinoids, either underestimated or even overlooked in the former literature, appear to be significant components of ubiquitous
organic assemblages contained in various deposits of the bahamite type of facies. The most diversified taxonomically are the echinoids from Malogoszcz in the Holy Cross Mountains (22 species, of which 4 dominate: Rhabdocidaris orbignyana, Hemicidaris intermedia, Gymnocidaris agassizi, Holectypus corallinus). The richest numerically is the collection from Czarnoglowy in Western Pomerania (13 species, of which only 2 dominate: Hemicidaris hoffinanni and Nucleolites letteroni). 

The systematically accounted forms, totalling over 2,000 specimens, represent 31 species of 20 regular genera, and 10 species of 5 irregular genera. Of these, four species are new to science, viz. Pseudosalenia malogostiana sp.n., Pseudocidaris sanctacrucensis sp.n., Trochotiara kongieli sp.n., and T. suleiovense sp.n. The well preserved specimens, although usually devoid of spines and apical plates, display the SEM-recognizable features of the tests (i.a. pore-pairs morphology, tubercle arrangement) substantial for a functional analysis of 14 more commonly occurring species. This analysis stimulated a paleobiologic interpretation focused on the behavioral and environmental (very shallow up to subtidal) conditions under which the studied echinoids lived and were buried, i.a. by such catastrophic events as storm-induced and mass-movement deposition. A separate, short section of the paper concerns the grazing traces of regular echinoids [classified in ichnology as Gnathichnus pentax BROMLEY, 1975], caused by browsing the epibionts, and preserved in the studied sequence on various organic (shelly) substrates, the other echinoid tests including.


Keywords


Echinoidea, taxonomy, paleoecology, Upper Jurassic, Poland

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