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Titre du document / Document title

Le genre Plagiolophus (palaeotheriidae, perissodactyla, mammalia) : Revision systematique, morphologie et histologie dentaires, anatomie cranienne, essai d'interpretation fonctionnelle = The Plagiolophus genus (palaeotheriidae, perissodactyla, mammalia) : systematic revision, morphology and dental histology, skull anatomy, functional interpretation attempt

Auteur(s) / Author(s)

REMY Jean A. (1) ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

(1) Laboratoire de paléontologie de l'ISE-M, Université Montpellier II. Laboratoire de paléontologie de l'EPHE, Montpellier, FRANCE

Résumé / Abstract

The genus Plagiolophus is documented, almost solely in Western Europe, from the middle Eocene up to the mid Oligocene (MP 12 to MP 25), i.e. more than for 15 MY. Seventeen species are now recorded whose two of them are new, P. ringeadei nov. sp. and P. mamertensis nov. sp. Some anatomical variations and the deflection of certain evolutionary trends justify the distinction of three subgenera, Paloplotherium, Fraasiolophus nov. and Plagiolophus s.s. The genus displays a wide range in size and weight (between 10 and 150 kg). The detailed description of the skull of several species is here given for the first time. Despite important evolutionary drifts during this long time span, the dentition shows a great structural homogeneity, which renders difficult the determination of fragmentary specimens or isolated teeth. It is characterized by a great heterodonty; premolars are little molarized and present a certain regression through time with paradoxically some progress in the molarization. The hypsodonty increases: the first Plagiolophus are hardly less brachyodont than Propalaeotherium, and the last ones are nearly as hypsodont as Merychippus from the early Miocene. The upper molars change from a wide crown pattern, with an open occlusal surface, lightly oblique transverse lophs and rounded internal cusps, to a narrower pattern, with a frontally constricted occlusal surface and internal lophs aligned parallel to the ectoloph. The M3/3 become always longer. The dental enamel displays horizontal Schreger-bands with imprecise limits occupying only the middle part of the enamel layer. The dentine is remarkable by its high rate of pericanalicular dentine. The crown cementum, lacking in earlier forms, increases to the point where it fills the occlusal valleys of the teeth. The masticatory musculature shows a increasing prominence of the temporal, with probably an important role devoted to the pterygoid muscles in lateral movements related to a two-phase type of chewing. The evolution of the dentition, of the masticatory musculature and of the repartition of masticatory forces indicate that the Plagiolophus have known different diets through their long evolutionary history; at first browsers they became mixed feeders and finally grazers. Their relatively long neck allowed these animals to reach different vegetal layers. The strength of the nuchal crests also suggests that they were able to have strong backwards movements of the head to pull up their food. This evolution of diet seems related to the slow degradation of environmental conditions attested during this period in western Europe, with the generalization of more open landscapes, increasing aridity and more marked seasons. Besides, a remodeling of the face is ontogenetically and along time observed, in relation with the evolution of the masticatory apparatus and especially with that of the mandibular lever arm. The post-canine diastemata become longer in the course of evolution; the free extremities of the nasals are always relatively long which contradicts the hypothesis according to which Paloplotherium may have had a trunk. At last the lineage Fraasiolophus can be distinguished by the presence of a deep malar fossa, probably related to a strong development of the maxillo-labialis superior muscle.

Revue / Journal Title

Palaeovertebrata    ISSN  0031-0247   CODEN PLVTAW 

Source / Source

2004, vol. 33, no1-4, pp. 17-281 [265 page(s) (article)] (8 p.1/4)

Langue / Language

Français
Revue : Anglais

Editeur / Publisher

Université de Montpellier II, Laboratoire de paléontologie, Montpellier, FRANCE  (1967) (Revue)

Mots-clés anglais / English Keywords

United Kingdom

;

Great Britain

;

Southern Europe

;

Iberian Peninsula

;

Central Europe

;

Europe

;

sedimentary rocks

;

chemically precipitated rocks

;

Phanerozoic

;

Cenozoic

;

Tertiary

;

Paleogene

;

Eocene

;

Chordata

;

Vertebrata

;

Tetrapoda

;

Mammalia

;

Theria

;

Eutheria

;

Rhone France

;

Vaucluse France

;

England

;

Spain

;

Switzerland

;

Germany

;

Lot-et-Garonne France

;

Gironde France

;

Quercy

;

France

;

Western Europe

;

paleoclimate

;

phylogeny

;

new taxa

;

functional morphology

;

aridity

;

landscapes

;

degradation

;

upper Eocene

;

diet

;

phosphate rocks

;

biostratigraphy

;

paleoenvironment

;

teeth

;

sexual dimorphism

;

skulls

;

Oligocene

;

middle Eocene

;

interpretation

;

extremities

;

histology

;

morphology

;

revision

;

Perissodactyla

;

Mots-clés français / French Keywords

Royaume Uni

;

Grande Bretagne

;

Europe Sud

;

Péninsule Ibérique

;

Europe Centrale

;

Europe

;

Roche sédimentaire

;

Roche chimique

;

Phanérozoïque

;

Cénozoïque

;

Tertiaire

;

Paléogène

;

Eocène

;

Chordata

;

Vertebrata

;

Tetrapoda

;

Mammalia

;

Theria

;

Eutheria

;

Rhône

;

Vaucluse

;

Angleterre

;

Espagne

;

Suisse

;

Allemagne

;

Lot-et-Garonne

;

Gironde

;

Quercy

;

France

;

Europe Ouest

;

Plagiolophus

;

Paléoclimat

;

Phylogénie

;

Taxon nouveau

;

Morphologie fonctionnelle

;

Aridité

;

Paysage

;

Dégradation

;

Eocène sup

;

Régime alimentaire

;

Roche phosphatée

;

Biostratigraphie

;

Paléoenvironnement

;

Dent

;

Dimorphisme sexuel

;

Crâne

;

Oligocène

;

Eocène moyen

;

Interprétation

;

Anatomie locomotion

;

Histologie

;

Morphologie

;

Révision

;

Perissodactyla

;

Mots-clés espagnols / Spanish Keywords

Reino Unido

;

Gran Bretaña

;

Europa Sur

;

Península ibérica

;

Europa central

;

Europa

;

Roca sedimentaria

;

Roca química

;

Fanerozoico

;

Cenozoico

;

Terciario

;

Paleógeno

;

Eoceno

;

Chordata

;

Vertebrata

;

Tetrapoda

;

Mammalia

;

Rhône

;

Vaucluse

;

Inglaterra

;

España

;

Suiza

;

Alemania

;

Gironde

;

Francia

;

Europa del Oeste

;

Paleoclima

;

Filogenia

;

Nuevo taxón

;

Morfología funcional

;

Paisaje

;

Eoceno sup

;

Roca fosfatada

;

Bioestratigrafía

;

Paleoambiente

;

Diente

;

Dimorfismo sexual

;

Cráneo

;

Oligoceno

;

Eoceno medio

;

Interpretación

;

Anatomía locomoción

;

Histología

;

Morfología

;

Revisión

;

Perissodactyla

;

Mots-clés d'auteur / Author Keywords

nouveaux taxons

;

Paléogène

;

anatomie crânienne

;

histologie dentaire

;

périssodactyles

;

Localisation / Location

INIST-CNRS, Cote INIST : 14105, 35400011564466.0020

Nº notice refdoc (ud4) : 17881629



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