Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 4

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The analysis of shell-drilling predation by naticid gastropods on molluscs from the Korytnica Clays (Middle Miocene, Holy Cross Mountains, Central Poland) has focused on the bivalve Corbula gibba and gastropods Natica tigrina and Hinia restitutiana. The results indicate that predatory behaviour of naticids varies depending on the size of the predator. When drilling corbulids, large naticids displayed higher site-selectivity than smaller naticids. Also, large naticids drilled energetically attractive prey (Hinia restitutiana and Natica tigrina) more frequently than small naticids. Preferential drilling displayed by large naticids from the Korytnica Clays increases the net energy gain for the predator and in result allows it to drill more effectively.
Two new assemblages of Mississippian pelagic chondrichthyan microremains were recovered from the pelagic limestone of the area of Krzeszowice, NW of Kraków, Poland. The older assemblage represents the upper Tournaisian of Czatkowice Quarry and the younger one the upper Viséan of the Czernka stream valley at Czerna. The teeth of symmoriiform Falcatidae are the major component of both collections. A comparison of the taxonomic composition of the assemblage from Czerna (with the falcatids and Thrinacodus as the major components) to the previously published materials from the Holy Cross Mountains (Poland), Muhua (southern China), and Grand Canyon (Northern Arizona, USA) revealed the closest similarity to the first of these, probably deposited in a deeper water environment, relatively far from submarine carbonate platforms. A short review of Mississippian falcatids shows that the late Viséan–Serpukhovian period was the time of the greatest diversity of this group.
Test−drilling predation by cassid gastropods on minute clypeasteroid echinoids has been studied in the fossil assemblage of the Heterostegina Sands (middle Miocene, Holy Cross Mountains, Poland). The analysed prey, collected from two sublithofacies of the Heterostegina Sands (coarse−grained Heterostegina Sands and fine−grained Heterostegina Sands), represent three species of Echinocyamus (E. linearis, E. pusillus and E. pseudopusillus). The drill holes were produced presumably by one cassid species, Semicassis miolaevigata. The investigation showed that drilling predation intensities varied among the prey species. Within both fine− and coarse−grained sands, E. linearis was drilled more frequently than E. pusillus. An intermediate value of drilling predation was recognised for E. pseudopusillus. The intensities of drilling predation recognised for some of the prey species (E. pusillus) varied also between (but never within) the sublithofacies. Drilling predation was both size− and site−selective. Larger individuals of E. linearis and E. pusillus were attacked more frequently and the aboral side of the test of all Echinocyamus species was drilled preferentially. An extremely high concentration of drill holes was observed in the apical disc and petals. Results obtained for the most abundant prey (E. linearis) indicate that the predatory behaviour of large cassids was somewhat different from those typical of small cassids. Large cassids drilled and consumed their prey almost always individually, whereas small cassids sometimes preyed upon the urchins in a group. Large cassids displayed also a higher site−selectivity. They more frequently drilled in the petals and apical disc. The patterns of drilling predation were most likely controlled by the potential energetic value of prey (measured by the internal volume/test thickness ratio), prey and predator mobility, prey mode of life, thickness and porosity of the prey's tests, as well as by the proportions between the size of the prey and size of the predator. The results suggest that the mode of life of the prey and its test structure can influence the drill hole morphology.
Drill holes on tests of Echinocyamus linearis from the Middle Miocene Korytnica Basin represent the first well documented fossil record of cassid predation from Poland. These traces complement the ecological information on the size and structure of cassid populations recorded by body fossils. The high number of drill holes recognised from the Heterostegina Sands, the uppermost part of the Korytnica depositional sequence, indicates the occurrence of a large cassid population during the late stage of development of the Korytnica Basin. The small size of most of the drill holes indicates that juvenile gastropods of the family Cassidae, which are not preserved in the fossil record of the investigated area, were also present in the cassid populations.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.