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Planktonic Foraminiferida originated in the Triassic[?] or Early Jurassic but only expanded markedly in the Early to mid-Cretaceous. It is during the mid-Late Cretaceous that they evolved into a wide range of morphotypes and were able to colonise a much greater range of environments and regions. During the mid-Cretaceous, in particular, they developed a range of strategies which allowed them to move...
The Ordovician was the most significant Period in bivalve diversification. From a small Cambrianstock of palaeotaxodonts, the most fundamental radiation occurred in the early Ordovician. An intrinsic factor was the most significant, involving the evolution of the feeding gill within the palaeotaxodonts. This fundamental morphological change allowed development of more effective feeding strategies,...
The overall pattern of ancient diversifications was apparent more than a century ago, and since thenhas shown no basic change. This suggests that the fossil record is both robust and reliable. Yet many questions remain to be answered. The recent surge of interest in mass extinctions, for example, has emphasized the causes of trauma and the victims involved. Relatively less attention has been paid...
L'analyse de deux séquences régionales de France, l'une du Dévonien en Montagne Noire et l'autre du Paléogène des phosphorites du Quercy, a permis de comparer l'évolution des diversités de deux groupes distincts, les conodontes marins et les mammifères terrestres. Les réponses identiques de ces deux groupes face à une crise indiquent qu'il existe un mécanisme commun, quelque soit le groupe systématique,...
Le comportement des phytocénoses continentales lors des couples crises-paléodiversifications est assezdifférent de celui des faunes marines, matériel habituel de l'étude de ces événements. Souvent les périodes de diversifications ne sont pas concomitantes. Une approche globale du Phanérozoïque et surtout, à une toute autre échelle, des études de flores terrestres du Jurassique et du Crétacé inférieur...
Changes in biodiversity of rocky-shore ecosystems from the early Precambrian (3,500 Ma) to the last interglacial epoch (125 Ka) are summarized on the basis of the fossil record associated with geological unconformities that reflect coastal paleotopography. This analysis is derived from data reported in 130 published papers culled and updated from previous bibliographic reviews. Minimum total diversity...
The Palaeozoic history of neoselachian sharks is barely known, and the first unequivocal member ofthis clade is recognized from the Lower Triassic. At the end of the Triassic, neoselachians show a dramatic radiation in Western Europe, where they are represented by seven genera. In the same area, we notice also the appearance of four genera of sharks of uncertain affinities, but showing some convergences...
In the fossil record, distinction between the two basic aspects of evolution, i.e. branching of evolutionarytrees (cladogenesis) and evolutionary transformations along lineages (phyletic evolution, “anagenesis”), is especially well visible. The process of allopatric speciation, presumably the most common, if not the only, way to split a lineage, cannot be recognised directly in any single geological...
From a database of 226 Cambrian - Ordovician genera of organophosphatic-shelled brachiopods comprisingthe Subphylum Linguliformea, 11 sets of morphological characters typify all orders and superfamilies. Seven sets of these large-scale evolutionary novelties were established already by the end of the mid Cambrian, 2 more by the end of the late Cambrian, and the remaining 2 before the end of the Arenig...
Les plus anciennes cryptospores sont connues dès le Llanvirn. Les assemblages de ces sporomorphes évolueront peu jusqu'au Llandovery, période au cours de laquelle la plupart des espèces de cryptospores seront remplacées. De manière très caractéristique, les formes entourées d'une membrane vont régresser nettement. Les spores trilètes apparaissent à l'Ashgill et c'est seulement au Wenlock qu'elles...
SEM observations of polished, sligthly etched rock samples from limestone-marl alternations of theSilurian of Gotland allowed the discovery of numerous excellently preserved calcareous micro- and nannofossils, most of which remained unknown to date. Only few morphotypes can be assigned with varying degrees of confidence to groups which are already described in literature. The assemblages include possible...
The invasion of the land started in the Ordovician and continued into the Carboniferous. The peak ofdiversification rate and increase in biomass of terrestrial vegetation occurred during the Devonian. However, no permanent increase in marine diversity occurred at that time. Instead, a plateau of fluctuating but non-trending diversity extended for 200 million years from the later Ordovician to the...
Pebbles with a diverse shelly fauna, including bivalves, brachiopods, gastropods, and bryozoans havebeen found in the basal diamictite of the Don Braulio Formation, cropping out in the Sierra de Villicum, Argentine Precordillera. The Don Braulio Formation is of Ashgill age, but according to the brachiopods the fauna of the pebbles is of early Caradoc age. On the basis of this age and some elements...
Traditionnellement, les phacopinés néodévoniens à ceil réduit des plates-formes externes étaient intégrés dans le seul taxon Cryphops,, bien que sa répartition dans le temps soit discontinue. Une nouvelle interprétation des relations phylétiques du groupe Cryphops est proposée, en tenant compte des caractères céphaliques ventraux, non considérés jusqu'ici. Dans ce modèle, les différents morphotypes...
For the first time, comparative information is given for paleobiological patterns of creodonts. Three European (MP11–13 of the Geiseltal, MP13?–14 of Egerkingen, MP16–17b of Quercy) and three North American (Wa-1 to 3, Wa-4 to 6, Br-1) Eocene creodont faunas represented by totally 60 species are included in this study. The ecological niche of each species is defined for this study by the combination...
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