Wyniki wyszukiwania - Biblioteka Nauki

Ten serwis zostanie wyłączony 2025-02-11.

Nowa wersja platformy, zawierająca wyłącznie zasoby pełnotekstowe, jest już dostępna.
Przejdź na https://bibliotekanauki.pl

Ograniczanie wyników

3 Acta Palaeontologica Polonica

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Sortuj według:

Ogranicz wyniki do:

Relationships of the Devonian Strobilepis and related Pensylvanian problematica

100%

Hoare R. D. , Mapes R. H.

nr 2

111-128

Reinterpretation of the North American Strobilepis spinigera Clarke 1888 from the Devonian and the find of Diadeloplax paragrapsima gen. et sp. n. from the Pennsylvanian provide the basis for the recognition of a new class of uncertain affinity, Multiplacophora. The range of the class is Middle Devonian (Erian) to Pennsylvanian (Morrowan). Multiplacophora differ from the order Hercolepadida and the classes Thambetolepida and Polyplacophora in the number, shape, and arrangement of plates; the presence of large spines; and the complexity of internal canal systems in the plates and spines.

Środkowodewońska Strobilepis należy do najbardziej tajemniczych skamieniałych organizmów młodszego paleozoiku. Autor ilustruje i analizuje muzealne okazy Strobilepis (w tym również identyfikowane niegdyś jako ślimaki i chitony) dowodząc, że poszczególne skleryty ułożone były liniowo na grzbiecie zwięrzecia a więc odmiennie niż morfologicznie i strukturalnie podobne płytki sylurskiej Hercolepas i dewońskiego Protobalanus. Z późnego karbonu stanu New York pochodzą podobne do Strobilepis zestawy sklerytów opisane jako Diadeloplax paragrapsima gen. et sp. n. Dla tych dwu form utworzona została nowa gromada Multiplacophora z rzędem Strobilepida.

Chaetognath grasping spines from the Upper Mississippian of Arkansas [USA]

80%

Doguzhaeva L. A. , Mutvel H. , Mapes R. H.

nr 3

Previously unidentified tiny (about 0.5 mm in length), hollow, gently curved, serrated spines probably originally composed of horny, organic fibers from the Upper Mississippian (Middle Chesterian = Namurian A equivalent or lower Serpukhovian) of Arkansas (USA) are described, and their probable chaetognath affinities are discussed. The specimens are preserved in an oval accumulation (about 15 mm long and 6 mm wide) of approximately 200 specimens within a small (about 25 mm in length) phosphatic concretion. For comparison, the grasping spines of the Recent chaetognath Eukrohnia hamata were examined. The Arkansas specimens are named Eoserratosagitta serrata gen. et sp. nov., and this genus is assigned to the Phylum Chaetognatha. The Upper Mississippian spines are also compared with protoconodonts. This comparison supports the hypothesis that the chaetognaths may have existed in the Cambrian.

Piggyback whorls: A new theoretical morphologic model reveals constructional linkages among morphological characters in ammonoids

70%

Ubukata T. , Tanabe K. , Shigeta Y. , Maeda H. , Mapes R. H.

nr 1

A new theoretical morphological model is proposed for the analysis of growth, form and morphospace of ammonoid shells. In this model, the shape of a radial cross section through the shell is simulated by “piggybacking” of successive whorls. The “piggyback whorls model” is defined in terms of the enlarging rate of the perimeter and the proportion of the dorsal wall to the whorl periphery, if an isometric relationship is assumed between perimeter and area of the cross−sectioned whorl. Allometric coefficients on these growth parameters determine how compressed and evolute shells are formed. The present model successfully reproduced some correlations among purely geometric variables that have been reported in previous works and were also observed in our biometric analyses. This model yields a hypothesis of “constructional linkages” between aperture shape and coiling geometry that might provide a functional coupling between hydrostatic and hydrodynamic characters. The model may partly explain Buckman’s Law of Covariation between rib features and shell shapes.