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September 1998
Vol. 27, Fasc. 1-2
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Print ISSN: 0031-0247
Online ISSN: 2274-0333
Frequency: biannual

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Palaeovertebrata Vol. 27, Fasc. 1-2:September 1998

Table of contents


Articles



Otolithes de poissons du Pliocène inférieur de Papiol, près de Barcelone.
Dirk Nolf, Ramon Mané and Agusti Lopez
Keywords: Catalonia; otoliths; Pliocene; Spain; teleosts
 
  Abstract

    The Zanclian marls from Papiol provided otoliths belonging to 53 teleost taxa; nine of those are new for the Mediterranean Pliocene. The association reflects a bathymetry between 150 and 350 m, but it is likely that such depths only existed at the initial stage of flooding of the Llobregat bay. A compilation of the available data for the whole Mediterranean realm at Zanclian time provided a list of 163 taxa, of which 105 could be identified at species level. This last group provides the most useful data for evaluating the composition and affinities of the Mediterranean Zanclian fauna, which appears to be significantly different from the Recent Mediterranean fauna. The Zanclian fauna counts 68 % of Recent species: 12,5 % were already represented in the Mediterranean Miocene, 37 % appeared there at the Zanclian, and 18 % are extra-Mediterranean today. This last group is essentially composed by oceanic fishes, living in the warm parts of the Atlantic and Indo-Pacific Oceans. It is evident that a non neglectable number of Recent species only penetrated very recently in the Mediterranean, which stresses the differences between the more oceanic Zanclian Mediterranean fauna and the present one.


      


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Une nouvelle espèce de Steneosaurus (Thalattosuchia, Teleosauridae) dans le Callovien du Poitou (France) et la systématique des Steneosaurus longirostres du Jurassique moyen d'Europe Occidentale.
Patrick Vignaud
Keywords: middle Jurassic; nov. sp.; phylogenetic relationships; skulls; Steneosaurus pictaviensis; systematics; thalattosuchian crocodile
 
  Abstract

    The study of all the available skulls allows us to review the systematic relationships of the longirostrine Steneosaurus from the Middle Jurassic of western Europe. Up to now, Aalenian and Bajocian deposits have not yielded any significant Steneosaurus remain. In the Bathonian, the only valid longirostrine species, S. megistorhynchus, is known in the Britain-Normandy Basin, the Poitou and the Lorraine. In the Callovian, most of the longirostrine Steneosaurus remains can be attributed to the species S. leedsi. Nevertheless, some remains from the Middle Callovian of Poitou (France) show important differences with S. leedsi. A new Steneosaurus species, only known in Poitou, is created and named S. pictaviensis. The specific characters are carried by the skull (preorbital pit well marked, orbit and ptetygoid fossae shapes), by the mandible (symphysis shape) and by the teeth (ornamentation). S. megistorhynchus is probably situated near the stem of the Callovian species but remains from the Bathonian and Lower Callovian are very scarce and it is very difficult to precise the phylogenetic relationships between the longirostrine species of the Middle Jurassic.
      


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Le genre Leptolophus (Perissodactyla, Mammalia): morphologie et histologie dentaires, anatomie cranienne, implications fonctionnelles.
Jean-Albert Remy
Keywords: dental histology; Eocene; functional anatomy; Palaeotheriidae; skull anatomy; Southern France; systematics
 
  Abstract

    A strong lophodonty, an extreme heterodonty, some hypsodonty and regular overlayings of coronal cement are prominent features of the genus Leptolophus (Palaeotheriinae = Palaeotheriidae s.s.). The histological pattern of the teeth unusually joins type II enamel prisms, characteristic of advanced ungulates, together with archaic features, such as an almost complete lack of Hunter-Schreger zonation and a weak expanse of peritubular dentine. The skull is narrow and slender, with an elongated ante-orbital facial region, a moderately notched nasal aperture, a rather elongated post-canine diastem, parallel zygornatic arches and a fairly dorsally located squamoso-mandibular joint.The functional analysis brings to light "ectolophodont" masticatory cycles with two phases, in which maximum power was applied, contrary to equíds, on hindmost teeth; likewise, skull accomodations to increasing height of the teeth are quite different. This study leads to the assumption that Leptolophus may have been light mammals, living in rather open surroundings, browsing on herbaceous plants or leaves cropped close to the ground. Moreover, it appears that it could have been some inadequacy of dental structures to the dietary, which leaded to quick wear of the teeth and to many enamel notches, but had been somewhat balanced by the early increase of hypsodonty, not induced in such a case by a biotop deterioration (as it will happen at the end of the Eocene). This ínadaptation might account for the short duration of the genus Leptolophus, whose the 3 species, L. stehlini, L. nouletí and L. magnus n. sp. are indeed confined in the level MP 16. Its geographical spreading (as far as known, South of western Europe) and the morphological pattern of its dentition suggest that this genus would have been related to early upper Eocene endemic spanish forms.





      


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