Current issue


December 2018
Vol 41-2
<< prev. next >>

Print ISSN: 0031-0247
Online ISSN: 2274-0333
Frequency: biannual

Article Management

You must log in to submit or manage articles.

You do not have an account yet ? Sign up.


Most downloaded articles (last 90 days)


Terrestrial vertebrate paleocommunities from the Cerro del Pueblo Formation (Late Cretaceous; Late Campanian) at Las Aguilas, Coahuila, Mexico
Héctor E. Rivera-Sylva, Eberhard Frey, Wolfgang . Stinnesbeck, Natalia Amezcua Torres and Diana Flores Huerta
Keywords: Campanian; Coahuila; dinosaurs; Mexico.; vertebrates

doi: 10.18563/pv.42.2.e1
 
  Abstract

    The Las Águilas site near Porvenir de Jalpa, Coahuila, Mexico, is extremely rich in tetrapod remains comprising both bones and trackways of several dinosaur taxa of late Campanian age. Within a 50 m thick section we identified at least nine layers with dinosaur bone assemblages. In one of these the dinosaur bones are associated with remnants of eusuchian crocodilians, turtles, plesiosaurs, pterosaurs, tyrannosaurids, dromaeosaurids, parksosaurid, hadrosaurids, ceratopsids, and ankylosaurs. This layer is also rich in coprolites of turtles, crocodilians and likely theropods, thus providing evidence for the wealth of Late Cretaceous vertebrate life in the area. 


  Article infos

in press

PDF
Recherches de mammifères paléogènes dans les départements de l'Aisne et de la Marne pendant la deuxième moitié du vingtième siècle
Pierre Louis
Keywords: Biochronology; Eastern Paris Basin; Fossil localities; Mammals; paleoenvironments; Paleogene; Paleogeography
 
  Abstract

    A brief historical account of fossil vertebrate discoveries in the Eastern part of the Paris Basin between the beginning of the nineteenth century and 1950 is given. Other localities discovered since then are presented. A reconstruction of past landscapes is briefly elaborated. A biozonation based on mammals is proposed, from the Late Thanetian to the Middle Bartonian. Paleogeographical considerations are added. Suggestions regarding the search for new marnmal localities are made. 


  Article infos

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

PDF
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.
      


  Article infos

Published in Vol.39-1 (2015)

PDF
There were giants upon the earth in those days
Pierre-Olivier Antoine
Keywords: Eurasia; history of science; Indricotheriinae; Paleogene; Rhinocerotoidea

doi: 10.18563/pv.38.1.e4
 
  Abstract

    Rhinoceros Giants: the Paleobiology of Indricotheres. Donald R. Prothero. Life of the Past Collection, Indiana University Press; 160 pp. (66 b&w illustrations). Hardback (7x10”): USD 42.00 plus shipping. ISBN: 978-0-253-00819-0. E-book: USD 34.99. ISBN: 978-0-253-00826-8.
      


  Article infos

Published in Vol.38-1 (2014)

PDF
Analysis of changing diversity patterns in Cenozoic land mammal age faunas, South America
Larry G. Marshall and Richard L. Cifelli
Keywords: Cenozoic; Chronofaunas; diversity; Equilibrium theory; Extinction; Land mammal faunas; Origination; South America
 
  Abstract

    Comparison of various measurements of taxonomic evolution using stratigraphic range data for orders, families and genera of land mammals indicates several means by which deficiencies of the South American fossil record (e.g., presence of hiatuses, unequal temporal and geographic representation of ages, unequal systematic treatment) may be normalized, thus permitting a less distorted appreciation of diversity pattern and trend. Initial radiation of native taxa resulted in a relative equilibrium by early Eocene time. Subsequent increases in absolute diversity were apparently induced by immigration at the family level and by environmental factors at the generic level. Miocene through Pleistocene phases of faunal stability, herein characterized as chronofaunas, are punctuated by rapid turnover events resulting from a complex of factors, including adaptive radiation of immigrant taxa into unoccupied eco-space; environmental and concomitant habitat change induced by orogenic events of the Andes; and biotic interactions between native and immigrant taxa, including competition and prey naivete. The first two factors account for major faunal transitions in the South American middle and late Tertiary; immigration-induced turnover may have been of greater importance in shaping the character of the fauna upon the Great American Interchange and the arrival of man in the Neotropics 


  Article infos

Published in Vol. 19, Fasc. 4 (1990)

PDF
Rongeurs nouveaux de l'Oligocène Moyen d'Espagne.
Louis Thaler
Keywords: Cricetidae; Oligocene; Pseudocricetodon; Rodents; Theridomys

doi: 10.18563/pv.2.5.191-207
 
  Abstract

    Description of four new rodents from a recently discovered locality at Montalban. Theridomys crusafonti nov. sp. is considered as the ancestry of T. Iembronicus. Theridomys varian: nov. sp. includes «Theridomys» morphotypes and «Blainvilllimys» morphotypes; it could be ancestral to B. blainvillei. Pseudoltinomys nanus nov. sp. represents a new lineage paralleling in evolution that of P. gaillardi (which is equally found at Montalban). Pseudocricetodon montalbanensis nov. gen., nov. sp. designates a lineage of very small Cricetidae accompanying Eucricetodon. With these well defined new species and six others present in the locality, Montalban appears as the best faunal reference point within the biochronologic zone of La Sauvetat.
    As an annex, discussion of two rodent specimens from the classic localíty of Tárrega, close in age to that of Montalban. 


  Article infos

Published in Vol. 02, Fasc. 5 (1969)

PDF
Fossil mammals and the age of the changxindian formation, Northeastern China
Spencer G. Lucas
Keywords: Changxindian Formation; China; Eocene; Fossil mammals
 
  Abstract

    Re-evaluation of the small collection of mammal fossils from the Changxindian Formation near Beijing, China indicates the following taxa are present: Eutheria, Hypsimilus beifingensis, cf. Miacis sp., Anthracotheriidae and Forstercooperia grandis. The presence of Forstercooperia grandis indicates an Irdinmanhan age and does not support previous assignment of a Sharamurunian age to the Changxindian Formation. 


  Article infos

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

PDF
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).



      


  Article infos

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

PDF
Cervus elaphus rossii (Mammalia, Artiodactyla), a new endemic sub-species from the Middle Pleistocene of Corsica
Elisabeth Pereira
Keywords: Cervus elaphus; Corsica; Endemism; Pleistocene
 
  Abstract

    Several endemic deer remains from the Middle Pleistocene deposits of the Castiglione cave (Oletta, Haute-Corse) are examined here. A morphometric analysis allows to relate them to a new insular subspecies Cervus elaphus rossii. The bones were compared with those of the mainland early Middle Pleistocene subspecies Cervus elaphus acoronatus Beninde and the European species Cervus elaphus Linné (Late Middle Pleistocene and Upper Pleistocene forms (continental and insular)). The Castiglione fossil shows peculiar morphofunctional features in its appendicular skeleton suggesting a morphological convergence with certain Bovidae. 


  Article infos

Published in Vol. 30, Fasc. 3-4 (2001)

PDF
New Late Miocene plecotine bats (Chiroptera, Vespertilionidae: Plecotini) from Gritsev, Ukraine
Valentina V. Rosina, Sergei Kruskop and Yuriy Semenov
Keywords: Barbastella; bats; late Neogene; Mammalia; Plecotus

doi: 10.18563/pv.42.1.e2
 
  Abstract

    The Late Miocene site of Gritsev (MN 9, Ukraine) has yielded a very rich bat fauna, the remains of which are well preserved. Compared to other Neogene bat assemblages of Europe, the Gritsev bat community is unique in preserving plecotine bats, which are rare from Neogene sites. Some peculiar and new bat species, including a large plecotin Otonycteris, already were described from the Gritsev mammal site. Here we report new records of small plecotin bats from Gritsev, including a new taxon, Barbastella maxima nov. sp. This is the earliest reliable fossil record of this genus and it differs from more recent species of Barbastella in being considerably larger. The evolutionary patterns in the odontology within the tribe Plecotini, supported by biostratigraphical distribution of fossil records of Plecotus are discussed. The morphological peculiarities of the new fossils of plecotine bats from Gritsev are discussed in connection with its possible taxonomical affinity. 


  Article infos

in press

PDF

A femur of the Late Cretaceous giant bird Gargantuavis from Cruzy (southern France) and its systematic implications
 
Eric Buffetaut and Delphine Angst
Keywords: Aves; femur; France; Gargantuavis; Late Cretaceous

doi: 10.18563/pv.42.1.e3
 
  Abstract


    A large avian femur recently discovered at the Late Cretaceous Montplo-Nord locality at Cruzy (Hérault, southern France) is referred to the giant bird Gargantuavis philoinos. The estimated mass of the bird is 57 kg, within the range of living cassowaries. The specimen provides new evidence about the anatomy of G. philoinos, notably showing that the distal end of the femur was similar to that of modern birds in having a condylus lateralis subdivided into two semicondyles. A new diagnosis of Gargantuavis philoinos is provided and the taxon is placed in a new family of basal ornithurines.
      


  Article infos

in press

PDF
Les insectivores des phosphorites du Quercy
Jean-Yves Crochet
Keywords: Insectivores; Quercy phosphorites
 
  Abstract

    Many types of insectivores have been described from specimens found in the Quercy phosphorites. These remains very often were not dated because they came from old collections. Recent excavations have permitted the situation of Amphidozotherium cayluxi FILHOL in the late Eocene. Two new genera are descrlbed based on material both from the old collections (Cryplotopos nov. g.) and from that recently recovered (Darbonetus nov. g., beginning of the middle Oligocene). Their systematic positions are revised and comparisons with American faunas are made. Amphidozotherium is not a talpid, but an erinaceoid belonging to an indeterminate family. Saturninia gracilis STHELIN is classified among the Nyctitheriinae, Myxomygale antiqua FILHOL among the Urotrichini Talpinae, and the genus Geotypus POMEL among the Scaptonichini Talpinae. A new study of the talpids from Auvergne has been rendered necessary. During the late Eocene and Oligocene precise morphology relationships existed between certain insectivores of Europe and North America. 


  Article infos

Published in Vol. 06, Fasc. 1-2 (1974)

PDF
New remains of the giant bird Gargantuavis philoinos from the Late Cretaceous of Provence (south-eastern France)
Eric Buffetaut, Delphine Angst, Patrick Mechin and Annie Mechin-Salessy
Keywords: Aves; Gargantuavis; Late Cretaceous; Pelvis; South-eastern France

doi: 10.18563/pv.39.2.e3
 
  Abstract


    Two incomplete pelves of the giant bird Gargantuavis philoinos are described from Late Cretaceous deposits at Fox-Amphoux (Var, south-eastern France). They consist of synsacra with attached parts of the ilia. One of them has undergone considerable dorsoventral compression, which makes it very similar in appearance to the holotype pelvis of Gargantuavis philoinos from Campagne-sur-Aude (Aude, southern France). The second specimen has suffered some lateral distortion but is uncrushed dorsoventrally. Because of this, its avians characters (including an arched synsacrum and widespread pneumatisation) are especially clear. These new specimens confirm the avian nature of Gargantuavis and reveal new details about its pelvic anatomy, but provide little new evidence about its systematic position within Aves. The geographical distribution and general rarity of Gargantuavis are discussed.
      


  Article infos

Published in Vol.39-2 (2015)

PDF
The Ctenodactylidae (Rodentia) from the Oligocene of Ulantatal (inner Mongolia, China)
Monique Vianey-Liaud, Norbert Schmidt-Kittler and Laurent Marivaux
Keywords: Adaptive radiation; Ctenodactylidae; Mongolia; Oligocene; Rodents
 
  Abstract

    This paper proposes a systematic revision of the Oligocene Mongolian Ctenodactylidae, on the basis of abundant material obtained by screen/washing operations in stratified localities of the Ulantatal area (Inner Mongolia) (UTL1, 2, 3, 4, 5, 7, 6 & 8). A Chinese-German team has collected several thousands of isolated rodent teeth, and a number of fragmentary jaws. A new genus is identified (Alashania nov. gen. tengkoliensis nov. sp.), and eight former species are reevaluated, Karakoromys decessus, Tataromys sigmodon, T. minor, T. plicidens, Yindirtemys ulantatalensis, Y. bohlini, Y. deflexus, with several synonymies. A new Yindirtemys species is described: Y. shevyrevae nov. sp. and another one close to that: Y. aff. shevyrevae nov. sp. Four new species, which are rare in the localities, remain in open nomenclature because they are not well-represented. Yindirtemys differs from the other genera by the permanence of crescentic structures, while the other genera show a general reduction of the trigonoid area (= anterior valley). We define a range of size variation for each well documented population. Although the dental morphology shows a wide range of variation, given that transitional morphologies occur in a single locality, it is possible to provide a clear definition for most species. We show that dental patterns of the different genera can be derived from the pattern of Karakoromys. As a number of Tataromyinae have been determined in several localities from China, Kazakhstan and Mongolia, usually on the basis of scarce material, or surface collections, the present study would be used to re-evaluate their attribution inasmuch as the taxa are now placed in the Oligocene stratigraphy. The diversity of sizes and forms reflects the adaptive radiation of the family during the Oligocene, within a forested environment where the vegetation was probably abundant. 


  Article infos

Published in Vol. 34, Fasc. 3-4 (2006)

PDF
Nouvelles données sur les mammifères du Thanétien et de l'Yprésien du bassin d'Ouarzazate (Maroc) et leur contexte stratigraphique.
Emmanuel Gheerbrant, Jean Sudre, Sevket Sen, Claude Abrial, Bernard Marandat, Bernard Sigé and Monique Vianey-Liaud
Keywords: early Paleogene; magnetostratigraphy; Mammals; Morocco; North Africa; Ouarzazatz basin; systematics
 
  Abstract

    New faunal and stratigraphical data on the vertebrates localities from the early Paleogene of the Ouarzazate Basin (Adrar Mgorn 1, Adrar Mgorn 1 bis et N'Tagourt 2), Morocco, are presented. A magnetostratigraphical study, the first for such early Paleogene Arabo-African mammal localities, and the discovery of probable remains of the nannofossil Discoaster support the Thanetian age of the Adrar Mgorn 1 site. The magnetostratigraphy suggests a slightly later age than was thought for the Paleogene formations of the local series of Tinerhir and for the vertebrate localities: late or latest Thanetian for Adrar Mgorn 1 and Adrar Mgorn 1 bis, middle Ypresian for N'Tagourt 2. It also indicates a lower position of the KT boundary in the series. Two tons of matrix recovered in the vertebrate sites have vielded new data on the micromammals. A damaged lower molar from N'Tagourt 2 is referable to Khamsaconus bulbosus  and supports the proboscidean affinities of this species and especially possible relationships with bunolophodont taxa such as elephantiforms. A lower molar from Adrar Mgorn 1 bis belongs to a new form which can be identified as a plesiadapiform or an euprimate close to Altiatlasius koulchii though significantly larger. A new material from Adrar Mgorn 1 illustrates a new dilambdodont adapisoriculid species which is referable to Garatherium : ?Garatherium todrae n. sp. Another species referred to Garatherium is known in the locality (?Garatherium n. sp.). Garatherium is a new lineage from the Ouarzazate basin which crosses the Paleocene-Eocene boundary together with Palaeoryctes, Didelphodontinae gen. and sp. 2, Todralestes, and Afrodon, and it is the first Paleocene-Eocene lineage identified outside of this basin (Garatheríum is based on a species from El Kohol, Algeria). Among the Paleocene-Eocene lineages from the Ouarzazate basin, it should be also mentioned a new possible carnassial form (carnivoran or creodont; Adrar Mgorn 1), and an upper molar of Cimolestes cf. incisus (Adrar Mgorn 1 bis). The upper molar THR 168 previously reported as from an indeterminate didelphodontine is here identified as the M1/ of Afrodon chleuhi. The micromammal faunas from the Ouarzazate basin are positioned in the global chronological framework of the mammal localities from the Paleogene of the Arabo-African domain. 


  Article infos

Published in Vol. 27, Fasc. 3-4 (1998)

PDF
Rongeurs Miocènes dans le Valles-Penedes 2 : Les rongeurs de Castell de Barbera
Jean-Pierre Aguilar, Jordi Agusti and J. Gibert
Keywords: Castell de Barbera; Miocene; Rodents; Valles-Penedes
 
  Abstract

    The rodent-fauna (Cricetidae and Gliridae) recently found at Castell de Barbera (Spain) is similar to those from the other locslities of the Valles - Penedes - Can Ponsic 1 and Can Llobateres - : same composition and similar evolutionary level of the different species. On the other hand this fauna is different from those of Upper Vindobonian and Vallesian localities of the Calatayud - Teruel area. Castell de Barbera has an intermediate chronological position between the localities of Anwil (Switzerland) and Can Ponsic 1. It is still not possible to validate or invalidate the initial attribution based on absence of Hipparion of Castell de Barbera to the Upper Vindobonian. 


  Article infos

Published in Vol. 09, Fasc. 1 (1979)

PDF
First record of the family Protocetidae in the Lutetian of Senegal (West Africa)
Lionel Hautier, Raphaël Sarr, Fabrice Lihoreau, Rodolphe Tabuce and Pierre Marwan Hameh
Keywords: innominate; Lutetian; Protocetid; Senegal

doi: 10.18563/pv.38.2.e2
 
  Abstract

    The earliest cetaceans are found in the early Eocene of Indo-Pakistan. By the late middle to late Eocene, the group colonized most oceans of the planet. This late Eocene worldwide distribution clearly indicates that their dispersal took place during the middle Eocene (Lutetian). We report here the first discovery of a protocetid fossil from middle Eocene deposits of Senegal (West Africa). The Lutetian cetacean specimen from Senegal is a partial left innominate. Its overall form and proportions, particularly the well-formed lunate surface with a deep and narrow acetabular notch, and the complete absence of pachyostosis and osteosclerosis, mark it as a probable middle Eocene protocetid cetacean. Its size corresponds to the newly described Togocetus traversei from the Lutetian deposits of Togo. However, no innominate is known for the Togolese protocetid, which precludes any direct comparison between the two West African sites. The Senegalese innominate documents a new early occurrence of this marine group in West Africa and supports an early dispersal of these aquatic mammals by the middle Eocene.
      



  Related dataset
  Article infos

Published in Vol.38-2 (2014)

PDF
Etude du crâne de Pachynolophus lavocati n. sp. (Perissodactyla, Palaeotheriidae) des Phosphorites du Quercy
Jean-Albert Remy
Keywords: Perissodactyla; Quercy phosphorites

doi: 10.18563/pv.5.2.45-78
 
  Abstract

    The genus Pachynolophus, one of the poorest known of the Palaeotheriidae, includes the brachyodont forms with reduced and non-molariform premolars and with upper molars lacking a mesostyle. Quantitative characters (divers surface indications and elongation of the teeth), while demonstrating a close relationship to Hyracotherium, permit a better differentiation of the genus, confirm its specific splitting, and permit the distinction of three lineages. The skull from Memerlein is taken as the type of a new species, P. Iavocati, of which the dentition is extremely characterized by its lophiodonty, the strong reduction of the premolars and the reduction of the cingula. This characterization testifies to a late age which extends the existence of the genus quite near to the Eocene-Oligocene limit. Compared with the only two skulls known of related species (Hyracotheríum vulpiceps and Pachynolophus Iivinierensis), that from Memerlein is distinguished by progressive characters affecting diferent regions but most particularly the braincase; it is not possible, however, to isolate within this evolution the part which leads to a systematic differentiation. Modernization is translated by a considerable increase in size of the braincase, principally in the frontal region, a development of the facial region with anterior displacement of the dental series and a greater specialization of the masticatory apparatus. This evolution parallels the history of the Equidae of the North American early Tertiary, but certain particularities, the form of the alisphenoid, the presence of an anterior frontal foramen, and the structure of the paroccipital apophysis, testifies to the independance of the European forms. 


  Article infos

Published in Vol. 05, Fasc. 2 (1972)

PDF
Evolution et extinction des reptiles marins au cours du Mésozoïque.
Nathalie Bardet
Keywords: Crocodiles; evolution; Extinctions; faunal assemblages; Helveticosaurs; Hupehsuchians; Ichthyoaurs; lizards; Marine Reptiles; Mesozoic; Nothosaurs; Pachypleurosaurs; Placodonts; Plesiosaurs; Snakes; Thalattosaurs; Turnovers; Turtles
 
  Abstract

    An interpretation of the marine reptile fossil record, based on the existing litterature and complemented by the review of ancient collections and the study of new material, permits a better understanding of Mesozoic marine ecosystems. An inventory of the marine reptiles known from the Lower Triassic to the Paleocene is presented: 46 families, about 200 genera and 400 species have been recorded. This data base includes commentaries about systematics, stratigraphical ranges and geographical distribution of taxa. Marine reptiles include a mosaic of not necessarily closely related groups: ichthyosaurs, thalattosaurs, hupehsuchians, pachypleurosaurs, placodonts, nothosaurs, plesiosaurs, pliosaurs but also crocodiles, lizards, snakes, turtles. The diversity studies reveal that the fossil record of marine reptiles has been punctuated by two mass extinctions, during the Middle-Upper Triassic transition and at the Cretaceous-Tertiary boundary. The Jurassic-Cretaceous and Cenomanian-Turonian boundaries (the latter marked by the disappearance of ichthyosaurs) are potential crisis periods, but current data are not sufficient to reach conclusions. The Ladinian-Carnian transition is characterized by the disappearance of 64 % of families and affects essentially coastal forms. This extinction coincides with an important regressive phase. During the Upper Triassic, a faunal reorganisation within marine reptiles leads to the progressive disappearance of near-shore forms and to the development of pelagic groups. During the Maastrichtian-Danian crisis, 36% of families died out. Large-sized pelagic forms such as mosasaurs and elasmosaurs were the most affected and their extinction seems to have been rather sudden. On the other hand, pliosaurs and protostegid turtles became extinct, but were already declining. The survivors were near-shore forms such as crocodiles, snakes and some turtles and they may have taken refuge in freshwater environments. A break in the food chain based on phytoplankton is proposed as an extinction scenario for pelagic forms.

      


  Article infos

Published in Vol. 24, Fasc. 3-4 (1995)

PDF
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)

PDF