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Wyświetlanie 1-5 z 5
Tytuł:
A revision of Campyloprion Eastman, 1902 (Chondrichthyes, Helicoprionidae), including new occurrences from the Upper Pennsylvanian of New Mexico and Texas, USA
Autorzy:
Itano, W. M.
Lucas, S. G.
Powiązania:
https://bibliotekanauki.pl/articles/139067.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
carboniferous
permian
eugeneodontiformes
helicoprionidae
edestoidea
Chondrichthyes
geometric morphometrics
karbon
perm
ryby chrzęstnoszkieletowe
ryby chrzęstne
chrzęstniki
morfometria geometryczna
Opis:
Campyloprion Eastman, 1902 is a chondrichthyan having an arched symphyseal tooth whorl similar to that of Helicoprion Karpinsky, 1899, but less tightly coiled. The holotype of Campyloprion annectans Eastman, 1902, the type species of Campyloprion, is of unknown provenance, but is presumed to be from the Pennsylvanian of North America. Campyloprion ivanovi (Karpinsky, 1922) has been described from the Gzhelian of Russia. A partial symphyseal tooth whorl, designated as Campyloprion cf. C. ivanovi, is reported from the Missourian Tinajas Member of the Atrasado Formation of Socorro County, New Mexico, USA. Partial tooth whorls from the Virgilian Finis Shale and Jacksboro Limestone Members of the Graham Formation of northern Texas, USA, are designated as Campyloprion sp. Two partial tooth whorls from the Gzhelian of Russia that were previously referred to C. ivanovi are designated as Campyloprion cf. C. annectans. The age of Toxoprion lecontei (Dean, 1898), from Nevada, USA, is corrected from the Carboniferous to the early Permian. An alternative interpretation of the holotype of T. lecontei is presented, resulting in a reversal of its anterior-to-posterior orientation. The genera Helicoprion, Campyloprion, and Shaktauites Tchuvashov, 2001 can be distinguished by their different spiral angles.
Źródło:
Acta Geologica Polonica; 2018, 68, 3; 403-419
0001-5709
Pojawia się w:
Acta Geologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ontogenetic changes in the craniomandibular skeleton of the abelisaurid dinosaur Majungasaurus crenatissimus from the Late Cretaceous of Madagascar
Autorzy:
Ratsimbaholison, N.O.
Felice, R.N.
O’Connor, P.M.
Powiązania:
https://bibliotekanauki.pl/articles/21868.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
ontogenetic change
craniomandibular skeleton
abelisaurid dinosaur
Majungasaurus crenatissimus
Dinosauria
Abelisauridae
geometric morphometrics
ontogenesis
skull
Cretaceous
Gondwana
Late Cretaceous
Madagascar
Opis:
Abelisaurid theropods were one of the most diverse groups of predatory dinosaurs in Gondwana during the Cretaceous. The group is characterized by a tall, wide skull and robust cervical region. This morphology is thought to have facilitated specialized feeding behaviors such as prolonged contact with prey. The Late Cretaceous abelisaurid Majungasaurus crenatissimus typifies this abelisaurid cranial morphotype. Recent fossil discoveries of this species include a partial growth series that allows for the first time an investigation of ontogenetic variation in cranial morphology in a representative abelisaurid. Herein we examine growth trajectories in the shape of individual cranial bones and articulated skulls of Majungasaurus using geometric morphometrics. Several major changes in skull shape were observed through ontogeny, including an increase in the height of the jugal, postorbital, and quadratojugal, an increase in the extent of the contacts between bones, and a decrease in the circumference of the orbit. The skull transitions from relatively short in the smallest individual to tall and robust in large adults, as is seen in other theropods. Such morphological change during ontogeny would likely have resulted in different biomechanical properties and feeding behaviors between small and large individuals. These findings provide a post-hatching developmental framework for understanding the evolution of the distinctive tall skull morphology seen in abelisaurids and other large-sized theropod dinosaurs.
Źródło:
Acta Palaeontologica Polonica; 2016, 61, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Taxonomic revision of the Paradoxididae Hawle and Corda, 1847 from the Miaolingian (Cambrian) of the Holy Cross Mountains, Poland: a morphometric approach to simply deformed trilobites
Autorzy:
Nowicki, Jakub
Żylińska, Anna
Powiązania:
https://bibliotekanauki.pl/articles/2024019.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
paradoxididae
miaolingian
Cambrian
Holy Cross Mountains
geometric morphometrics
simple deformation
Słowiec Hill
trylobity
miaoling
kambr
góry Świętokrzyskie
morfometria geometryczna
Słowiec
Opis:
The taxonomy of simply deformed paradoxidids from the Miaolingian (Cambrian) of Słowiec Hill, Holy Cross Mountains, Poland, is revised based on morphometric analysis. The material represents two species: Acadoparadoxides slowiecensis (Czarnocki in Orłowski, 1965) and Hydrocephalus? polonicus (Czarnocki in Orłowski, 1965). A new assemblage zone based on the combined although not precisely known ranges of these two taxa is suggested replacing the previous Paradoxides polonicus Zone of Orłowski (1975, 1988, 1992a). The Acadoparadoxides slowiecensis–Hydrocephalus? polonicus Assemblage Zone corresponds to the middle and upper part of the Wuliuan Stage (lower Miaolingian).
Źródło:
Acta Geologica Polonica; 2021, 71, 4; 371--391
0001-5709
Pojawia się w:
Acta Geologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fractal analysis of ostracod shell variability: A comparison with geometric and classic morphometrics
Autorzy:
Aiello, G
Barattolo, F.
Barra, D.
Fiorito, G.
Mazzarella, A.
Raia, P.
Viola, R.
Powiązania:
https://bibliotekanauki.pl/articles/22918.pdf
Data publikacji:
2007
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
fractal analysis
variability
statistical method
systematics
Krithe compressa
ostracod
shell
Ostracoda
morphometry
morphological variability
Krithe iniqua
paleontology
Opis:
Two statistical methods, fractal geometry and geometric morphometrics, are tested for their applicability to ostracod systematics. For this comparison, two morphologically similar ostracod species (Krithe compressa and Krithe iniqua) whose genus−level systematics is still incompletely resolved, are selected. Twenty−nine right valves of each species were collected from the upper Pliocene samples at the Monte San Nicola section in southern Italy. Statistical analyses (MANOVA on morphometric shape variables, and D values) were utilized to test if geometric morphometrics and fractal analysis are appropriate into discriminating between the two species. Both methods succeeded in distinguishing the species statistically. The fractal analysis of the two ostracod species shows D values centered on 1.31±0.02 for Krithe iniqua and on 1.40±0.02 for Krithe compressa. Geometric morphometric analysis indicates significant differences between the two species and allows studying intra−populational variability as well as. The most variable traits indicated by geometric morphometrics are vestibular area and posterior outline of the shell, indicating that these traits are the most relevant for the systematics of the species analyzed. Both fractal geometry and geometric morphometrics provide a measure of population variability. Fractal analysis has the advantage of being free from any subjectivity in the selection of characters and could be most appropriate to use for analysis of complex ornamentation for systematic purposes. However, a possible advantage of geometric morphometrics over fractal analysis is its ability to indicate where statistically significant variations in shape occur on the shell.
Źródło:
Acta Palaeontologica Polonica; 2007, 52, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Geometric morphometric analysis and taxonomic revision of the Gzhelian (Late Pennsylvanian) conodont Idiognathodus simulator from North America
Autorzy:
HOGANCAMP, NICHOLAS J.
BARRICK, JAMES E.
STRAUSS, RICHARD E.
Powiązania:
https://bibliotekanauki.pl/articles/945657.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
conodonta
idiognathodus
morphometrics
pennsylvanian
gzhelian
north america
midcontinent
Opis:
A new morphometric approach was developed to study morphological variation within P1 elements commonly referred to as Idiognathodus simulator, which was selected to be the biostratigraphic marker for the base of the global Gzhelian Stage (Carboniferous). This new approach combines landmark-based geometric morphometrics with eigen analyses to analyze shape variation within P1 elements of the I. simulator group, and could be used to analyze shape variation in other morphologically similar conodont groups. Specimens analyzed were obtained from three sections of the early Gzhelian Heebner Shale of the Oread cyclothem in the North American Midcontinent region, the cyclothem from which I. simulator was originally named. This analysis shows that the I. simulator group comprises a set of at least five species with asymmetrical P1 element pairs, relatively short adcarinal ridges, and a variably developed eccentric groove. Species discrimination is based on the presence of caudal and rostral lobes, character of the adcarinal ridges, and platform shape. The species I. simulator is restricted to P1 elements with a caudal adcarinal ridge that is isolated from the caudal platform margin. Idiognathodus lateralis sp. nov. is erected to include P1 elements with a caudal adcarinal ridge that is not isolated from the caudal platform margin.
Źródło:
Acta Palaeontologica Polonica; 2016, 61, 3; 477-502
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-5 z 5

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