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Śady ugryzień i regeneracji na triasowych liliowcach z Polski-dane wstępne

100%

Gorzelak P. , Salamon M. A.

tom Vol. 56, nr 10

885-886

Functional anatomy and mode of life of the latest Jurassic crinoid Saccocoma

63%

Brodacki M.

tom 51

nr 2

Loose elements of the roveacrinid Saccocoma from the Tithonian red Rogoża Coquina, Rogoźnik, Pieniny Klippen Belt, Poland, are used to test the contradictory opinions on the mode of life of Saccocoma. The investigated elements belong to three morphological groups, which represent at least two separate species: S. tenella, S. vernioryi, and a third form, whose brachials resemble those of S. vernioryi but are equipped with wings of different shape. The geometry of brachials’ articular surfaces reveals that the arms of Saccocoma were relatively inflexible in their proximal part and left the cup at an angle of no more than 45, then spread gradually to the sides. There is no evidence that the wings were permanently oriented in either horizontal or vertical position, as proposed by two different benthic life−style hypotheses. The first secundibrachial was probably more similar to the first primibrachial than to the third secundibrachial, in contrast to the traditional assumption. The winged parts of the arms were too close to the cup and presumably too stiff to propel the animal in the water efficiently. Swimming was probably achieved by movements of the distal, finely branched parts of the arms. The nonhorizontal attitude of the winged parts of the arms is also not entirely consistent with the assumption that they functioned as a parachute. Moreover, the wings added some weight and thus increased the energy costs associated with swimming. The hydrodynamic benefits balancing these extra costs are not entirely clear, but it seems probable that the wings reduced the sinking rate of the animal not by increasing the pressure drag, as suggested by the parachute−analogy, but by increasing the surface drag (friction drag), which also harmonize with the presence of spines, reticulate sculpture and conspicuous vacuolar ornamentation in some species of Saccocoma.

A rare comatulid crinoid, Semiometra petitclerci (CAILLET, 1923), from the Upper Oxfordian of Poland

51%

Radwańska U.

tom Vol. 57, no. 2

161-167

A small faunule of feather stars or comatulids (free-living crinoids of the order Comatulida A.H. CLARK, 1908) is recorded from Upper Oxfordian strata (Bielawy/Wapienno sequence) in the Couiavia region, north-western Central Poland. It represents a single, very small-sized species, Semiometra petitclerci (CAILLET, 1923), hitherto an extreme rarity in the Jurassic sequences of France and Germany. The present record extends the geographic distribution of the species in Europe, to evidence a wider range of the genus Semiometra GISLEN, 1924, prior to its fairly common occurrence and higher diversity during the Late Cretaceous.

Nanostructural and geochemical features of the Jurassic isocrinid columnal ossicles

51%

Stolarski J. , Gorzelak P. , Mazur M. , Marrocchi Y. , Meibom A.

nr 1

69-75

Calcite isocrinid ossicles from the Middle Jurassic (Bathonian) clays in Gnaszyn (central Poland) show perfectly preserved micro− and nanostructural details typical of diagenetically unaltered echinoderm skeleton. Stereom pores are filled with ferroan calcite cements that sealed off the skeleton from diagenetic fluids and prevented structural and geochemical alteration. In contrast with high−Mg calcite skeleton of modern, tropical echinoderms, the fossil crinoid ossicles from Gnaszyn contain only 5.0–5.3 mole% of MgCO₃. This low Mg content can be a result of either a low temperature environment (ca. 10℃) and/or low Mg/Ca seawater ratio. Both conditions have been proposed for the Middle Jurassic marine environment. Occurrence of Mg−enriched central region of stereom bars of Jurassic columnal ossicle of Chariocrinus andreae is consistent with the concept of magnesium ions involvement in earliest growth phases of calcium carbonate biominerals.

Crinoids from the Silurian of Western Estonia

51%

Ausich W. I. , Wilson M. A. , Vinn O.

nr 3

The Silurian crinoids of Estonia are re−evaluated based on new collections and museum holdings. Nineteen species−level crinoid taxa are now recognized. All crinoid names applied to Estonian Silurian crinoids during the middle 19th century are disregarded. Especially significant is the fauna reported herein from the Pridoli because coeval crinoids are very poorly known from the Baltic region and elsewhere. One new genus and four new species are described from Estonia, namely Calceocrinus balticensis sp. nov., Desmidocrinus laevigatus sp. nov., Eucalyptocrinites tumidus sp. nov., and Saaremaacrinus estoniensis gen. et sp. nov.