Search results for "Systematics"

Early oysters and their supposed Permian ancestors

2005

The origin of oysters is a much debated palaeontological issue. Recent morphological studies indicate that oysters are characterized by a particular ribbing pattern, the so-called antimarginal ribs which are characterized by a proper morphogenetic pattern. Therefore antimarginal ribs can be used as a diagnostic character in phylogeny. The earliest recognized bivalve displaying diagnostic features of oysters (sinistral attachment to the substrate, typical hinge and ligament structure, and antimarginal ribs) is Ostracites cristadifformis Schlotheim, 1820 first appearing in the Anisian of Europe. This common species was later attributed to Enantiostreon and is here transferred to Umbrostrea. S…

Tremadocian Stylophoran Echinoderms From The Taebaeksan Basin, Korea.

2006

15 pages; International audience; Abundant isolated elements of cornute and mitrate stylophorans were recovered from the upper Tremadocian Tumugol Formation in the Taebaeksan Basin, Korea. Cornute skeletal elements comprise a diverse assemblage of marginals and brachials of cothurnocystid affinities, suggesting the presence of no fewer than four different species. Mitrate remains include numerous isolated adorals, marginals, and aulacophoral plates with typical peltocystidan morphologies. Two adorals are identified as Anatifopsis sp., while all the others are attributable to A. cocaban. However, the two previously documented peltocystidans of Korea, A. cocaban and A. truncata, are sufficien…

So close yet so far: the disjunct global range of Orthotrichum consobrinum (Orthotrichaceae) includes North America

2021

Illuminating the evolution of bioluminescence in sharks

2023

The evolutionary context in which shark bioluminescence originated is poorly understood, despite it being critical to uncovering influential factors in the evolutionary history and diversity of living chondrichthyans as well as the mechanisms of deep-water colonization by vertebrates. This study provides the first joint reconstruction of the habitats, lifestyles, and occurrence of bioluminescence in the evolution of squalomorph sharks using ancestral state estimation analysis to resolve the timing of deep-sea colonization, the evolutionary origin of bioluminescence and the ancestral ecologies of this group. The results suggest that most squalomorphs originated in neritic environments from w…

New dinosaur, crocodylomorph and swim tracks from the Late Jurassic of the Lusitanian Basin: implications for ichnodiversity

2021

Séries charbonneuses dans des séquences rétrogradantes: cas du bassin houiller paralique westphalien de Jérada (Maroc)

1998

Abstract Several orders of stacked genetic sequences in the Westphalian C of the Jerada Basin are defined from detailed sedimentological data. Eight coal seams were formed in this paralic basin as distal facies passed laterally into proximal facies in retrogradational stages. These stages are related to base level rises that curtailed detrital influx and induced the development of swamps and the preservation of organic matter below anoxic water levels. The base level variations are related to active faulting along the basin margins and to sea level changes in the Palaeo-Tethys.

The first recorded protozygopteran insects from the Upper Permian of France

1999

. The earliest known Odonatoptera: Protozygoptera from the Upper Permian of Lodeve (France) are described. Epilestes gallica sp. nov. belongs to the Permolestidae and Lodevia longialata gen. et sp. nov. to the Permepallagidae. Both of these families were previously known from the Kazanian of Russia, suggesting a similar age for the formation of Lodeve.

The recovery and radiation of Early Jurassic ammonoids: morphologic versus palaeobiogeographical patterns

2001

Abstract The recovery and radiation of the Early Jurassic ammonoid morphospace, as represented by nine morphologic groups identified in an earlier study, are traced through the first 36 subzones of the Hettangian to Domerian time interval. A quantitative survey of the dispersion of 436 species over 15 palaeogeographical areas reveals seven palaeobiogeographical patterns, each corresponding to an exclusive set of species exhibiting similar characteristics in terms of distribution and abundance. This study combines morphologic, chronostratigraphical, and palaeobiogeographical data in an attempt to investigate possible connections between morphologic recovery and radiation patterns and the his…

Reconstitution du squelette d'astérides fossiles à partir d'ossicules isolés : intérêt taxinomique et phylogénétique

1999

Abstract Dissociated ossicles of asteroids are frequent in neritic sediments. Until now, this material was mainly used in the identification of species. A new method, associating a morphological analysis and counting of plates, allows the architecture of the skeleton and the shape of the body to be reconstructed. This method provides new elements for taxonomic and phylogenetic comparisons. It also provides indications on the adaptation of the asteroids to their environment. In geological beds, frequencies of the different kinds of plates will allow qualification of bioerosion and taphonomic sorting.

A NEW EARLY DEVONIAN THELODONT FROM CELTIBERIA (SPAIN), WITH A REVISION OF SPANISH THELODONTS

2006

:  A revision of thelodont scales from the Lower Devonian of the Iberian Chains enables their grouping into two taxa: Turinia pagei and T. nachoi sp. nov. These taxa are clearly distinguishable by morphological and histological features; they also have a different stratigraphic range (T. pagei is restricted to Lochkovian strata, whereas T. nachoi sp. nov. occurs within lower–middle Pragian rocks). The new species is represented by head, transitional (cephalopectoral) and trunk scales.