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Lissamphibians from Dams (Quercy, SW France): Taxonomic identification and evolution across the Eocene-Oligocene transition
Alfred Lemierre and Maeva J. Orliac
Keywords: Eocene-Oligocene; Grande Coupure; Lissamphibia; Quercy Phosphorites

doi: 10.18563/pv.48.1.e3
 
  Abstract

    The locality of Dams (Quercy, southwestern France) has yielded two fossil assemblages, one from the late Eocene and another from the early Oligocene, making it one of the few localities with infillings across the Eocene-Oligocene transition. At least 24 taxa (13 mammals, 11 snakes) have been identified in this locality. Study of the lissamphibian remains from Dams yields an Eocene and an Oligocene assemblage, with a total of eight taxa. The Eocene assemblage includes two unnamed salamandrine species, one unnamed pelobatid species and one pyxicephalid species (Thaumastosaurus). The Oligocene assemblage includes two unnamed pleurodeline species, one salamandrine species (Salamandra sansaniensis) and an unnamed pelobatid species. Among the eight taxa from Dams, one Eocene salamandrine and one Oligocene pleurodeline are identified for the first time in the Quercy. A review of the lissamphibians from the Quercy area identifies eleven taxa for the Late Eocene (MP19) and eight taxa for Early Oligocene (MP22), with a major turnover at the Eocene-Oligocene transition. This turnover occurs in a time of major climatic changes, with a significant decrease in temperature and precipitation and concurrent increase in seasonality in Europe, likely affecting specialized taxa.
      


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Evolution de la lignée Megacricetodon collongensis-Megacricetotodon roussillonensis (Cricetidae, Rodentia, mammalia) au cours du Midocène inférieur et moyen dans le Sud de la France.
Jean-Pierre Aguilar
Keywords: Cricetids rodents; Evolutionary lineage; Lower and Middle Miocene; Mammalian biochronology; Megacricetodon new species; Southern France
 
  Abstract

    New populations of the genus Megacricetodon have recently been discovered in Southern France.Two new species are defined: M. lemartineli n. sp. and M. fournasi n. sp., their stages of evolution are intermediate between those of M. gersii and M. roussillonensis. Morphological and biometrical analysis indicate the presence of only one lineage: M. collongensis--M. collongensis-gersii--M. gersii--M.lemartineli nov. sp.--M. fournasi nov. sp. and M. roussillonensis. This observation allows to refine the chronology based on rodents, for the Late Early Miocene and the Middle Miocene in the Southern France.
    Comparisons with some iberian species are done. The validity of the French species M. bezianensis and M. bourgeoisi is discussed. 


  Article infos

Published in Vol. 24, Fasc. 1-2 (1995)

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Strange Eocene rodents from Spain
Pablo Pelaez-Campomanes and Nieves Lopez-Martinez
Keywords: Biogeography; Eocene; PHYLOGENY; Rodents; Spain; Zamoramys extraneus n. gen. n. sp.
 
  Abstract

    A new European rodent from the middle Eocene of Spain, Zamoramys extraneus n. gen., n. sp., appears to be closely related to the middle Eocene chapattimyid rodents of Indo-Pakistan. This contradicts the generally accepted paleobiogeographic hypothesis of a Tethyian barrier between Europe and Asia isolating Europe during the middle Eocene. Because of this barrier, some authors have proposed that European and Asian rodents were not closely related, their similarity being the result of morphological convergence. Here monophyly has been tested, using the parsimony criterion, based on an analysis of dental characters (including discussing of homology and the validity of some characteristics). Our results indicate a phylogenetic relationship among the Asiatic Ctenodactyloidea, Zamoramys from Spain, and the European endemic Theridomyoidea. We also conclude from our analysis that theridomyoids and European ischyromyoids are probably not closely related phylogenetically. 


  Article infos

Published in Vol. 25, Fasc. 2-4 (1996)

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A new species of Propalaeotherium (Palaeotheriidae, Perissodactyla, Mammalia) from the Middle Eocene locality of Aumelas (Hérault, France).
Jean-Albert Remy, Gabriel Krasovec and Bernard Marandat
Keywords: Eocene; new species; Palaeotheriidae; Propalaeotherium

doi: 10.18563/pv.40.2.e1
 
  Abstract

    A new Propalaeotherium species, clearly distinct from the genus Eurohippus, is described. It is characterized by having a similar size as P. voigti from the German Geiseltal localities (MP 11 to MP 13 reference-level), but differs in several features suggesting a slighty more derived morphology. It presents indeed less brachyodont crowns with less prominent and less elevated cingula, slightly larger relative surface of premolars, and a more marked metaconid splitting on cheek teeth. This new species is unknown from other European localities except the nearby Saint-Martin de Londres locality which has been considered older than the MP 13 level. 


  Article infos

Published in Vol.40-2 (2016)

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Norselaspis glacialis n.g., n.sp, et les relations phylogénétiques entre les kiaeraspidiens (Osteostraci) du dévonien inférieur du Spitsberg.
Philippe Janvier
Keywords: Devonian; kiaeraspids; Osteostraci; Spitsbergen
 
  Abstract

    The anatomy of Norselaspis glacialis n.g., n.sp., a primitive kiaeraspidian from the Lower Devonian of Spitsbergen, is described on the basis of spécimens studied by grinding sections or prepared with dilute formic acid. This study yielded some new anatomical details, including the presence of a canal prolonging posteromedially the canal alloted to the facial nerve by Stensiö. This posterior prolongation of the « facial canal ›› into the posterolateral part of the labyrinth cavity is consistent with the hypothesis put forward by Allis, Lindström, Jefferies and Whiting, that this canal housed the glossopharyngeus nerve. Furthermore, in N. glacialis, the foramen usually referred to as the foramen for the œsophagus opens posteriorly into a cavity in the postbranchial wall, referred to here as the intramural cavity, and which is interpreted as having housed the heart. Consequently, the œsophagus probably accompanied the dorsal aorta through the aortic canal. Finally, the foramen generally interpreted as having transmitted the ventral afferent arterial trunk is here considered as having housed the hepatic vein, which emptied into the venous sinus of the heart. The ventral afferent arterial trunk may thus have passed through the former «œsophageal ›› foramen.
    The problem of the position of the dorsal nerves in the Osteostraci is discussed, and it is suggested that the three foremost nerve canals opening into the oralobranchial cavity housed the maxillary ramus of the trigeminus, the facial nerve and the glossopharyngeus nerve respectively. The mandibular ramus of the trigeminus must have accompanied one of the two foremost nerves, but for the moment it is impossible to decide which.
    The problem of the nature of the interbranchial crests of the Osteostraci is briefly discussed. Comparison with the branchial apparatus of the Petromyzontida does not support the hypothesis that the interbranchial crests are part of the branchial arches, incorporated into the endoskeletal shield. A different hypothesis is proposed, that the branchial skeleton of the Osteostraci was situated entirely inside the oralobranchial cavity, and was attached to the endoskeletal shield only by the ventromedial processes. The grooves classically allotted to the efferent branchial arteries would thus have housed extrabranchial arteries, branching off from the dorsal aorta, and irrigating the ventral branchial musculature.
    A phylogeny and a classification of the kiaeraspidians are proposed. The evolution of this monophyletic group is characterized by, e.g., reduction of cornual processes, shortening of the abdominal division of the shield, subdivision of the lateral fields, and enlargement of the supraoral fossae.
    The phylogenetic position of the kiaeraspidians within the Osteostraci remains uncertain. Their sister-group may be either the benneviaspidiens or the thyestidians, or Thyestes alone (in which case they would have to be included within the thyestidians). 


  Article infos

Published in Vol. 11, Fasc. 2-3 (1981)

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The beginning of the adaptive radiation of Theridomorpha (Rodentia) in Western Europe: morphological and phylogenetic analyses of early and middle Eocene taxa; implications for systematics
 
Monique Vianey-Liaud and Laurent Marivaux
Keywords: characters analyses; Dental morphology; Eocene; Rodentia; variability

doi: 10.18563/pv.44.2.e2
 
  Abstract

    This paper provides a revision of the early and middle Eocene European rodents previously referred to as Ischyromyoidea, including taxa considered to be at the origin of the Theridomorpha. The use of an accurate dental terminology and a better understanding of the size and shape of their infra-orbital foramen (i.o.f.) led us to a substantial revision of this group, which allowed to better characterize them and to appreciate their variability. On these bases, phylogenetic analyses (cladistic and standard Bayesian
    approaches) of early Ypresian to late Priabonian European rodent species were undertaken in order to highlight the root of the early Theridomorpha and its content. In this paper, the phylogeny was established based on 343 characters (338 dental) through 45 early Paleogene taxa using both cladistic and bayesian analyses. The ingroup included on one hand a few North American genera (Reithroparamys, Microparamys, and Acritoparamys) and European ones (Eogliravus, Ailuravus, Corbarimys, Meldimys, Euromys, Plesiarctomys, and Pseudoparamys) considered until now as being related with the North American superfamily Ischyromyoidea. On the other hand, it included genera close to the root of the Theridomorpha (Sparnacomys, Pantrogna, and Hartenbergeromys) and early Theridomyoidea (Masillamys, Protadelomys, and some Pseudosciuridae). The phylogenetic results obtained via the two
    distinct reconstruction approaches are consistent in virtually all relationships. The proposed systematics here derives from these phylogenetic results. This phylogenetic context led us to change the suprafamilial, familial, subfamilial or generic attribution of several species. Characters of Theridomorpha, like the obliquely developed postprotocristid allied with the occurrence of a metalophulid I, have been found in genera previously considered as Ischyromyidae (Pseudoparamys, Euromys, Sparnacomys, Meldimys, Pantrogna, and Hartenbergeromys) as well as the large i.o.f., when preserved (Pseudoparamys, Hartenbergeromys, and Masillamys). Based on these morphological observations and new phylogenetic considerations, the content of the Theridomorpha clade is here enlarged, thereby extending back the first theridomorph radiations to the early Eocene. Aside, a new taxon (Reinomys rhomboides gen and sp. nov.) is described from Avenay. In addition, a new genus, Auroremys, is created for the species subita (Comte et al., 2012) from Chery-Chartreuve. 


  Article infos

Published in 44-2 (2021)

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Contributions à l'étude du gisement miocène supérieur de Montredon (Hérault). Les grands mammifères. Avant propos.
Bernard Sigé
Keywords: Editorial; Mammalia; Montredon; Upper Miocene
 
  Abstract

    Le Mémoire Extraordinaire 1988 de PALAEOVERTEBRATA regroupe dix articles consacrés au gisement à mammifères du Miocène supérieur de Montredon (Hérault), connu et classique depuis la fin du siècle dernier, et auquel est lié le nom du savant paléontologue lyonnais Charles Depéret.
    Cette monographie vient normalement à la suite de celle parue en 1982 dans PALAEOVERTEBRATA, dont les différents articles traitaient de la stratigraphie du gisement, et faisaient l'étude des différents groupes de micromammifères représentés dans la faune (insectivores, chiroptères, rongeurs). 


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Published in Vol. 18, Ext (1988)

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 La poche à phosphate de Ste-Néboule (Lot) et sa faune de vertébres du Ludien Supérieur. Introduction
Bernard Gèze, Jean-Claude Rage, Colette Vergnaud-Grazzini, France de Broin, Eric Buffetaut, Cécile Mourer-Chauviré, Jean-Yves Crochet, Bernard Sigé, Jean Sudre, Jean-Albert Remy, Brigitte Lange-Badré, Louis de Bonis, Jean-Louis Hartenberger and Monique Vianey-Liaud
Keywords: Eocene; Quercy Phosphorites
 
  Abstract

    Le Quercy est aujourd 'hui un vaste plateau calcaire, parcouru par un réseau karstique actif, profondément
    entaillé par des vallées aux falaises abruptes, comme celles du Lot ou du Célé. Sur un sol peu épais domine la forêt de chênes, accompagnés de cornouillers, érables, genévriers. La faune est pauvre, peu diverse, et les nombreux chasseurs se satisfont de gibier d'élevage ...

    Il y a trente cinq millions d'années environ, le paysage était bien différent. La période de l'Eocène supérieur, qui s'achevait, avait été chaude et humide, si l'on se réfère à la fois aux paléotempératures (calculées à partir de sédiments marins extra·européens) et aux restes fossilisés de végétaux typiquement tropicaux. 


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Published in Vol. 08, Fasc. 2-4 (1978)

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A new species of hippopotamine (Cetartiodactyla, Hippopotamidae) from the late Miocene Baynunah Formation, Abu Dhabi, United Arab Emirates
Jean-Renaud Boisserie, Mathieu Schuster, Mark J. Beech, Andrew Hill and Faysal Bibi
Keywords: Arab Peninsula; Hippopotamidae; Hippopotamine event; Systematics

doi: 10.18563/pv.41.1.e2
 
  Abstract

    The discovery of new hippopotamid material from the late Miocene Baynunah Formation (Abu Dhabi, United Arab Emirates) has prompted the revision of the existing material of this as yet unnamed fossil taxon. The Baynunah hippopotamid appears to be distinct from all other contemporary and later species in having a relatively more elongate symphysis, a feature similar to the earlier (and more primitive) Kenyapotamus. Yet, the Baynunah hippopotamid presents a dentition typical of the Hippopotaminae. It is therefore a distinct species attributed to the later subfamily, described and named in this contribution. This species provides further evidence for a ca. 8 Ma evolutionary event (termed “Hippopotamine Event”) that initiated the spread and ecological significance of the Hippopotaminae into wet habitats across Africa and Eurasia. The morphological affinities of the new species from Abu Dhabi suggest that the Arabian Peninsula was not a dispersal route from Africa toward southern Asia for the Hippopotamidae at ca. 7.5 Ma to 6.5 Ma. 


  Article infos

Published in Vol 41-1 (2018)

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Critical comments on the genus Propachynolophus Lemoine, 1891 (Mammalia, Perissodactyla, Equoidea)
 
Jean-Albert Remy
Keywords: Eocene; Eurohippus; Pachynolophus; Propalaeotherium; tooth morphology

doi: 10.18563/pv.41.1.e3
 
  Abstract

    Abstract
     The validity of Propachynolophus Lemoine, 1891, supposedly an intermediate between Hyracotherium Owen, 1841 and Pachynolophus Pomel, 1847, has been questioned for a long time. A detailed analysis of features on which this genus is based further supported by a formal cladistic analysis demonstrates that Propachynolophus is not a valid taxon. The type species, “Propachynolophus gaudryi Lemoine, 1891” shall be assigned to Propalaeotherium Gervais, 1849, under the new combination Propalaeotherium gaudryi (Lemoine, 1891). “Pachynolophus maldani Lemoine, 1878”, later assigned to Propachynolophus, typifies the new genus Orolophus, under the binomen Orolophus maldani (Lemoine, 1878). The other referred species, “Propachynolophus levei Hooker, 1994” and “P. remyi Checa-Soler, 1997” are poorly documented, and both species shall be provisionally referred to as “Hyracotherium levei (Hooker, 1994) and “Hyracotherium remyi (Checa-Soler, 1997), pending new discoveries.
     
      


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Published in Vol 41-1 (2018)

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Les Périssodactyles (Mammalia) du gisement Bartonien supérieur de Robiac (Éocène moyen du Gard, Sud de la France)
Jean-Albert Remy
Keywords: Chasmotherium; new species; Palaeotheriidae; paleoenvironments

doi: 10.18563/pv.39.1.e3
 
  Abstract

    We present here a new updated counting of the perissodactyls of Robiac, the type locality of the MP 16 level of the biochronological scale of paleogene mammals and that of the Robiacian stage of Eocene Land Mammals Ages in Western Europe.
    The outcrop of Robiac consists actually of two 500m apart loci, Robiac-Nord and Robiac-Sud, considered of the same age according to the current discriminating power, and is dated from -38,7 MA after the last faunal, magnetostratigraphic and climatic calibrations.
    It has yielded a very abundant and rich of 21 taxa perissodactyl fauna, topped by the giant Lophiodon lautricense, last representative of the family Lophiodontidae, of which it is the last proved deposit. The Palaeotheriidae are much diversified with 5 genera and 9 species of "Pachynolophinae", 3 genera and 10 species of Palaeotheriinae. Nine taxa have been defined from Robiac: Chasmotherium depereti n. sp., Palaeotherium castrense robiacense Franzen, 1968, the genus Leptolophus Remy, 1965 with the species L. stehlini Remy, 1965 and L. magnus Remy, 1998, Anchilophus (Paranchilophus) jeanteti Remy, 2012, Metanchilophus chaubeti Remy, 2012, Lophiotherium robiacense Depéret, 1917 and Pachynolophus gaytei n. sp.
    The faunal Robiac cenogram with the associated flora testify to a hot, wet and forestal environment, likely corresponding to a short warming climatic phase; the broken up fossil bones should have been carried away and then gathered in swamp areas along the banks of a meandering river.
    The swarm of mammals of Robiac, the richest of contemporaneous deposits, has been followed by a drastic drop in perissodactyl diversity at the MP 17A level; a crisis which could have originated in a renewal of the global Eocene cooling. Fons 4, the type-locality of this level, is largely scarcer in perissodactyls and its cenogram testifies to a less diversified fauna, with on the whole smaller species, that likely means a cooler and drier climatic environment; a new perissodactyl diversification occurred but later.
      


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Published in Vol.39-1 (2015)

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Contribution à la classification des pistes de vertébrés du Trias: Les types du Stormberg d'Afrique du Sud (1).
Paul Ellenberger
Keywords: Footprints; South Africa; Stormberg; Trias
 
  Abstract

    No abstract available 


  Article infos

Published in Vol. 5, Ext (1972)

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Révision des Artiodactyles de l'Eocène moyen de Lissieu (Rhône)
Jean Sudre
Keywords: Artiodactyles; Dichodon; France
 
  Abstract

    The object of this work is the study of the artiodactyls of the karstic locality of Lissieu near Lyon. Among the sixteen species counted, five (Hyperdichobune nobilis, Hyperdichobune sp., Haplabunodon mulleri, Tapirulus depereti and Pseudamphimeryx schlosseri) are cited for the first time in this fauna. The description of part of the anterior dentition of «Dichobune» langi permits the referal of this species to the genus Hyperdichobune. The new selenodont species Dichodon lugdunensis  described in this work belongs, with its ancestor Dichodon simplex, to a lineage distinct from that of Dichodan cartieri and Dichodon ruetimeyeri. Finally, the taxonomic reality of the Lissieu species, Lophiobunodon rhodanicum Deperet, is justified. All the other species have been compared with those of Egerkingen. Even though with most of them no difference in age can be shown between the two deposits, some however indicate clearly by their degree of evolution that Lissieu is slightly more recent than Egerkingen. ln the history of Eocene mammals, the Lissieu fauna, because of its homogeneity, can be considered as a sure reference fauna of the Auversian period. 


  Article infos

Published in Vol. 05, Fasc. 4 (1972)

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Un giraffidae dans le pliocène de Montpellier ?
Claude Guérin
Keywords: Artiodactyla; France; Giraffidae; Mammalia; Montpellier; Ruscinian
 
  Abstract

    An upper giraffid premolar without any indication about its origin is preserved at the Montpellier University among numerous fossils from the ruscinian formation of Montpellier. It can be related to Samotherium, of the Upper Miocene in Eastern Europe, North Africa and Asia, or more probably to Bramatherium  or Hydaspitherium of the Pliocene of South East Asia. The sedimentological study of the matrix shows a calcareous background, which may indicate that this tooth does not come from the Montpellier formation. 


  Article infos

Published in Vol. 16, Fasc. 3 (1986)

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Relations phylétiques de Bachitherium filhol, ruminant de l'Oligocène d'Europe Occidentale.
Denis Geraads, Geneviève Bouvrain and Jean Sudre
Keywords: Artiodactyla; Bachitherium; Cladistic analysis; France; Mammalia; Oligocene; Ruminantia
 
  Abstract

    A detailed comparative study of a complete skeleton of Bachitherium and a cladistic analysis of the sub-order Neoselenodontia lead us to propose a cladogram and a new classification of this group. The Tylopoda are the sister-group of the Ruminantia, which are chiefly defined by the fusion of the cuboid and navicular. Within this infra-order, Amphimeryx is the sister genus of a tetraselenodont group, in which the Hypertragulidae are well-separated group from a monophyletic group defined by the loss of trapezium, fusion of capitatum and trapezoid, and the isolation of the hypoconid on lower molars. The most primitive genera of this group, Lophiomeryx and Iberomeryx still have an open trigonid on the lower molars, but this is lingually closed in Archaeomeryx, sister-genus of the higher Ruminantia which have fused metatarsals and more evolved milk teeth. We divide them into two pan/orders : Tragulina (including the recent and miocene Tragulidae, and the North-American Leptomerycidae), and Pecora, with reduced lateral metacarpals and a new crest (telocristid) on the lower premolars. Within the Pecora, the upper molars of Gelocus are more primitive than those of Bachitherium (a genus with many autapomorphies in the dentition) itself more primitive than the group Prodremotherium + Eupecora, with fused metacarpals. We consider the Eupecora (including several genera without frontal appendages) to be monophyletic. 


  Article infos

Published in Vol. 17, Fasc. 2 (1987)

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First evidence of an early Miocene marine teleostean fish fauna (otoliths) from la Paillade.(Montpellier,France)
Bettina Reichenbacher and Henri Cappetta
Keywords: Aquitanian; Biostratigraphy; La Paillade; marine deposits; Miocene; otoliths; Palaeoecology; Palaeogeography; Southern France; Teleostei
 
  Abstract

    A fossil fish fauna, based on 5533 otoliths, from the La Paillade locality at Montpellier is described and figured. The otolith-bearing marls correlate to mammal zone MN l (Aguilar, 1982), and thus represent the earliest Miocene. The fish fauna consists of 30 taxa belonging to 20 families. Two species are new: Dussumieria sittigi and Liza gaudanti. The predominant faunal element is the Lesueurigobius vicínalis-species complex, composing 73% of all investigated otoliths. The palaeoecological analysis reveals a marine to euryhaline fish fauna living under tropical to subtropical conditions in the transition zone littoral - sublittoral. Water depth probably was more than 10 m. The scarcity of pelagic físhes suggests that the habitat was either a sheltered bay and/or far away from the open sea. Furthermore, some genera represented in the La Paillade fish fauna presently live exclusively in the Indopacific realm. Their presence strongly supports a broad connection between the Indian Ocean, the Mediterranean, and the Paratethys Seas during the Early Miocene (Aquitanian). From a palaeobiogeographical point of view, faunal relationships were found between the La Paillade fish fauna and both the Paratethys fish fauna and the fish fauna from the deposits in the Upper Rhinegraben and the Mayence and Hanau Basins (Germany).



      


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Published in Vol. 28, Fasc. 1 (1999)

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First Neogene Otonycteris (Chiroptera: Vespertilionidae) from Ukraine: its biostratigraphic and paleogeographic significance.
Valentina V. Rosina
Keywords: bats; East Europe; Gritsev; Late Miocene; Mammalia

doi: 10.18563/pv.39.1.e2
 
  Abstract

    A new species, Otonycteris rummeli nov. sp., is described from the Late Miocene site Gritsev (MN 9) in the Ukraine. Otonycteris rummeli nov. sp. differs from those of most vespertilionids, except recent Otonycteris, Antrozous and Early Miocene Karstala silva, in having a well-developed entocingulid at the foot of the trigonid valley in the lower molars. The morphological resemblance of Otonycteris, Antrozous and Karstala is apparently a case of convergence in the evolution of the Old and New Worlds bat faunas. From at least the Middle Miocene the range of Otonycteris distribution spread to the whole of Central Europe and such a situation continued during the whole Late Miocene. This indicates a more arid climate in Europe during the Upper Miocene compared to the Quaternary. The reduction of the distribution range of Otonycteris and its extinction in most of the territory of Europe could have been caused by the global climatic cooling and increasing glacial cycle amplitude during the onset of the Quaternary. 


  Article infos

Published in Vol.39-1 (2015)

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Contributions à l'étude du gisement Miocène supérieur de Montredon (Hérault). Les grands mammifères. 3 - Les artiodactyles ruminants
Léonard Ginsburg and Herbert Thomas
Keywords: Artiodactyla; France; Montredon; Ruminentia; Upper Miocene
 
  Abstract

    The remains of Ruminantia are very rare at Montredon. No specific determination was possible. We have only one Micromeryx, one small cervid, one tragocere and one (?) gazella. The faunal spectrum is in good correlation with the general retreat of the cervids in the European upper Miocene, but in contrast it is not convenient for the bovids, which are in expansion at the same time. For them, we have to invoke the local ecological conditions.
      


  Article infos

Published in Vol. 18, Ext (1988)

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Schmelzmikrostruktur in den inzisiven alt-und neuweltlicher histricognather nagetiere
Thomas Martin
Keywords: Africa; Caviomorpha; Ctenodactyloidea; Deseadan; Enamel microstructure; Hunter-Schreger bands; Hystricognathi; Incisors; Ischyromyoidea; multiserial; Paleobiogeography; pauciserial; Phiomorpha; Rodentia; South America
 
  Abstract

    Enamel microstructure in the incisors of Old- and New World hystricognath rodents:

    The incisor enamel microstructure in more than 100 genera of fossil and Recent hystricognath and sciurognath rodents was studied. A multiserial schmelzmuster is present in the Hystricognathi, the Ctenodactylidae, advanced Chapattimyidae, and in Pedetes. A redefinition of pauciserial and multiserial HSB is given that makes the two enamel types unambiguously distinguishable which apparently represent well defined evolutionary levels. In the pauciserial Schmelzmuster the IPM is thicker than in the multiserial one. In pauciserial HSB the IPM always surrounds each prism, and the crystallites of the IPM run parallel to prism direction; transition zones between HSB are lacking; the inclination of the HSB is normally very low and the prism cross sections are not flattened but somewhat irregular. The number of prisms per HSB is no good distinctive character for pauciserial and multiserial HSB, since there exists a wide overlap. The pauciserial schmelzmuster is primitive, the multiseiial derived because: 1. the pauciseiial schmelzmuster appears earlier in the fossil record in the most primitive rodents (Paramyids s.l. and Ctenodactyloids); 2. the Eocene Ctenodactyloidea show pauciserial HSB but the Oligocene and younger ones are characterized by multiserial HSB; 3. in the outgroup comparison, the Eurymylidae (Mixodontia) show pauciserial HSB; 4. biomechanically, multiserial HSB strenghten the enamel better than pauciserial HSB, since their IPM runs nearly always in an angle of 45° or more to the prisms.

    In multiseríal HSB three subtypes can be distinguished which are differentiated by the IPM orientation. Primitive is a (rarely strict) parallel or acute angular, anastomozing IPM, and derived is an interrow sheet-like ("plattenartige") IPM. This evolutionary polarity is indicated by enamel evolution in the Ctenodactylidae which show an acute angular IPM in the Oligocene and a rectangular interrow sheet-like IPM since the Miocene. Among the Caviomorpha a rectangular interrow sheet-like IPM is restricted to the Octodontoidea; therefore they must be considered derived in terms of their enamel structure. The first multiserial HSB in rodent incisors appear in phiomyids or chapatrimyids from the Upper Eocene of Algeria. The IPM is acute angular and anastomozing. The worldwide next younger multiserial HSB are found in Lower Oligocene phiomyids of Fayum, Egypt There already a rectangular interrow sheet like IPM is present (in Metaphiomys) besides the acute angular anastomozing IPM.

    The first Caviomorpha from the Deseadan (Oligocene-Miocene) likewise show already acute angular anastomozing IPM (e.g. Scozamys) and rectangular interrow sheet-like IPM (Platypittamys). Therefore the first Caviomorpha cannot be positioned close to a transition from pauciserial to multiserial HSB. In none of the potential caviomorph ancestors from southern North America multiserial HSB or transitional stage between pauciserial and multiserial HSB could be found. The similarities between the enamel types of the Fayum rodents and the rodents from the Deseadan of South America make a derivation of the Caviomorpha from Paleogene North African phiomorph rodents or their direct ancestors most probable. This supports at the same time a descent of the platyrrhine Primates from North African anthropoids.
      


  Article infos

Published in Vol. 21, Ext (1992)

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Designating a lectotype for Mesacanthus pusillus (Gnathostomata: Acanthodii)
Matthew Baron and Kevin Seymour
Keywords: acanthodians; Chordata; Devonian; Midland Valley; Orcadian Basin

doi: 10.18563/pv.44.1.e2
 
  Abstract

    The early gnathostome genus Mesacanthus is well represented in both Lower Old Red Sandstone and Middle Old Red Sandstone assemblages of northern and central Scotland. This ‘acanthodian’ taxon is currently thought to comprise two valid species: M. mitchelli and M. pusillus. Although the whereabouts of the holotype of M. mitchelli (NHMUK PV P560) is known, the syntype material for M. pusillus has long been thought lost. Here we identify at least one specimen that formed part of the original syntype material for M. pusillus, albeit in a slightly different condition than when it was originally figured. This specimen is ROM 25872, which is here designated as the lectotype. A second specimen – ELGNM 1978.191.1 – could represent another of the syntype specimens, but poor preservation quality makes it impossible to be certain. 


  Article infos

Published in 44-1 (2021)

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S.I. Data