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Page 5 of 19, showing 20 record(s) out of 365 total

A late Eocene palaeoamasiine embrithopod (Mammalia, Afrotheria) from the Adriatic realm (Island of Rab, Croatia)
Fabrice Lihoreau Logo, Ljerka Marjanac, Tihomir Marjanac Logo, Ozan Erdal Logo and Pierre-Olivier Antoine Logo
Published online: 14/12/2023

Keywords: Balkanatolia; Grande Coupure; Great Adria; Paleobiogeography; Systematics

https://doi.org/10.18563/pv.47.1.e1

  Abstract

    A cheek tooth recently unearthed in the Lopar Sandstone unit, of late Eocene age, in the northern part of Rab Island, Croatia, is one of the very few Eocene mammalian remains found in the Adriatic area. Thorough comparison of this tooth with those of Old-World Palaeogene mammalian orders suggests that it is a M3 belonging to an embrithopod afrothere. The specimen is referred to as Palaeoamasia sp. This genus was formerly known only in Eocene deposits of Anatolia but with close relatives in Romania among Palaeoamasiinae. The geographical distribution of this subfamily perfectly matches the recently-named Balkanatolian landmass, which experienced in-situ evolution of endemic mammals prior to the Grande Coupure event that occurred around the Eocene–Oligocene transition. This last event is characterised by massive Asian immigration in Western Europe and the supposed extinction of many endemic Central and Western European mammals, including Palaeoamasiinae.
      


  PV article infos

Published in 47-1 (2024)

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The skull of Tetraceratops insignis (Synapsida, Sphenacodontia)
Frederik . Spindler Logo
Published online: 09/01/2020

Keywords: cranium; pelycosaur; Permian; therapsid origins

https://doi.org/10.18563/pv.43.1.e1

  Abstract

    Tetraceratops insignis is known from a single, crushed skull from the Lower Permian of Texas. Its unique proportions and osteological details gained central meaning in the question of the origins of Therapsida since this early synapsid has been determined as the oldest and less derived therapsid. Apart from Tetraceratops, the ‘mammal-like’ Therapsida and their sister, the pelycosaur-grade Sphenacodontidae, are separated by one of the longest ghost lineages in tetrapod fossil record. However, the minor, though well justified critique faced insistent publication regarding the therapsid hypothesis. A carefull re-evaluation of the holotypic skull reveals that therapsid traits cannot be supported, including a rejection of the formerly supposed adductor shelf in the temporal fenestra. Increased understanding of ‘pelycosaur’ character variation underlines a haptodontine-grade or, less likely, sphenacodontid position for Tetraceratops


  PV article infos

Published in Vol 43-1 (2020)

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An evening bat (Chiroptera: Vespertilionidae) from the late Early Eocene of France, with comments on the antiquity of modern bats
Suzanne J. Hand Logo, Bernard Sigé, Michael Archer Logo and Karen H. Black Logo
Published online: 01/08/2016

Keywords: evolution; palaeobiogeography; Prémontré; Western Europe; Ypresian

https://doi.org/10.18563/pv.40.2.e2

  Abstract

    Bats are among the most numerous and widespread mammals today, but their fossil record is comparatively meagre and their early evolution poorly understood. Here we describe a new fossil bat from dental remains recovered from late Early Eocene sediments at Prémontré, northern France. This 50 million-year-old bat exhibits a mosaic of plesiomorphic and apomorphic dental features, including the presence of three lower premolars, a single-rooted p3, short p4 with metaconid, myotodont lower molars and a tall coronoid process of the dentary. This combination of features suggests it is an early member of Vespertilionidae, today’s most speciose and geographically widespread bat family. The Prémontré bat has bearing on hypotheses about the origins of vesper or evening bats (Family Vespertilionidae), as well as crown-group chiropterans.


      


  PV article infos

Published in Vol.40-2 (2016)

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La poche à phosphate de Ste-Néboule (Lot) et sa faune de vertébres du Ludien Supérieur. 2- Amphibiens. Etude Preliminaire
Jean-Claude Rage Logo and Colette Vergnaud-Grazzini
Published online: 25/09/1978

Keywords: Eocene; Quercy Phosphorites

https://doi.org/10.18563/pv.8.2-4.175-179

  Abstract

    The Caudata are known by two Salamandridae ; one of them is attributed to the genus Megalotriton. The Pelobatidae form the major part of the Anura ; a few bones indicate also the presence of Neobatrachia. 


  PV article infos

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

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Pairomys et Ectropomys : la fin d'une ambiguïté ; mise au point sur les Oltinomyinae et Remyinae (Rodenia, Theridomyidae).
Monique Vianey-Liaud Logo, Norbert Schmidt-Kittler and Pablo Pelaez-Campomanes Logo
Published online: 20/05/1994

Keywords: PHYLOGENY; taxonomy; Theridomyidae; Upper Eocene

https://doi.org/10.18563/pv.23.1-4.119-152

  Abstract

    The description of new material of the Upper Eoœne of France, Southem Germany and Spain together with the restudy of the material described by Thaler (1966b) as Pairomys allows to confirm the validity of the genus Ectropomys up to know controversally discussed. As a consequence the subfamily Remyinae and Oltinomyinae can be defined precisely. The study of the dental characters shows that the Remyinae in fact belong to the Theridomyidae and represent a derived evolutionary unit within this family. The Oltinomyinae together with the Theridomyinae and Issiodoromyinae very probably form a monophyletic unit. 


  PV article infos

Published in Vol. 23, Fasc. 1-4 (1994)

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Les serpents des phosphorites du Quercy
Jean-Claude Rage Logo
Published online: 20/12/1974

Keywords: Grande Coupure; Quercy Phosphorites; Serpents

https://doi.org/10.18563/pv.6.3-4.273-303

  Abstract

    A short review of the genera and species of snakes from the Quercy's phosphorites described by former authors is followed by the study of specimens recently collected. Most of these latter specimens belong to the Aniliidae, Boidae, Colubridae and to the Scolecophidia; the precise systematic position of some of them is not defined yet. The following genera and species are described: Eonilius europae nov. gen. and nov. sp., Platyspondylia lepta nov. gen. and nov. sp., Coluber cadurci nov. sp. and Dunnophis cadurcensis nov.  sp.; a species described by de Rochebrune (Palaeopython filholi) is revised. One of the most important conclusions of this study is that the Colubridae appear as early as the Upper Eocene. The stratigraphic repartition of these snakes shows that the rich Upper Eocene fauna is followed by the very reduced fauna of the Lower Oligocene; then the oligocene «Grande Coupure» corresponds to a very important faunistic renewal. The fauna remains poor and little diversified during the beginning of the Middle Oligocene after which there is a new faunistic explosion. 


  PV article infos

Published in Vol. 06, Fasc. 3-4 (1975)

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First record of dinosaur eggshells and teeth from the north-west african Maastrichtian (Morocco).
Géraldine Garcia Logo, Rodolphe Tabuce Logo, Henri Cappetta Logo, Bernard Marandat, Ilham Bentaleb Logo, Aziza Benabdallah and Monique Vianey-Liaud Logo
Published online: 15/12/2003

Keywords: Africa; amniotic eggshells; Maastrichtian; Morocco; theropod teeth

  Abstract

    We report the discovery of amniotic eggshells and theropod teeth from the Late Cretaccous  period in Morocco.The megaloolithid family represents the only known dinosaur egg remains in the north part of Africa and attests indirectly to the occurrence of sauropod dinosaurs (titanosaurids) in the Maastrichtian of Africa.

      


  PV article infos

Published in Vol. 32, Fasc. 2-4 (2003)

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Nouvelle quantification de l'Hypsodontie chez les Theridomyidae : l'exemple de Theridomys ludensis nov. sp.
Monique Vianey-Liaud Logo
Published online: 30/12/1985

Keywords: Dental morphology; evolution; Hypsodonty; Oligocene; Theridomyidae

https://doi.org/10.18563/pv.15.3.159-172

  Abstract

    A new example of parallelism in the dental pattern ofthe Theridomyidae is illustrated by the description ofa new species: Theridomys Iudensis from the standard level of Antoingt (middle Oligocene). Considering the occurence ofthis parallelism phenomenon. the use of numerous qualitative and quantitative criteria is essential to characterize the different stages ofthe different evolutive lineages. Thus, a new simple parameter is proposed (CHY = H+l/0,5 L) to estimate hypsodonty of the medium hypsodont Rodentia. 


  PV article infos

Published in Vol. 15, Fasc. 3 (1985)

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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 Logo
Published online: 15/06/1981

Keywords: Devonian; kiaeraspids; Osteostraci; Spitsbergen

https://doi.org/10.18563/pv.11.2-3.19-131

  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). 


  PV article infos

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

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Etude de la Variabilité chez Lophiodon lautricense Noulet
Jean Sudre
Published online: 28/02/1971

Keywords: Cheek teeth; Eocene; Lophiodon; variability

https://doi.org/10.18563/pv.4.3.67-95

  Abstract

    The biometric and morphologie variability of the cheek teeth in the end-of-the-phylum species Lophiodon lautricense Noulet studied in this note, reposes on the observation of about 800 teeth. These were revealed to be little variable in absolute dimensions. The considerable morphologie variability in the upper premolars permitted the problem of the molarization process to be taken up. An hypothesis concerning the order of eruption of the cheek teeth is formulated based on an examination of a large number of milk dentitions. In conclusion, it is suggested that reservations be held on the value of dental characters classically used in systematics for the group under consideration. 


  PV article infos

Published in Vol. 04, Fasc. 3 (1971)

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Anatomie du membre antérieur chez un chiroptère Molossidé (Tadarida sp.) du Stampien de Cereste (Alpes-de-Haute-Provence).
Bernard Sigé
Published online: 01/01/1971

Keywords: Chiroptera; Molossidae; Oligocene

https://doi.org/10.18563/pv.4.1.1-38

  Abstract

    The present study describes in detail the anterior limb osteology of a molossid chiropteran of the genus Tadarida, from Céreste, a Stampian locality in the Apt-Forcalquier Oligocene basin already known for its fishes, plants and insects.

    A comparision with the Miocene forms T. srehlini from Saint-Géraud localities and T. sp. from Württemberg, also with the recent forms T. teniotis and Eumops perotis, does not show any clear morphological differences between the Tertiary and Recent Tadarida, indicating a rather noticeable anatomical stability, not exceptionnal indeed among Chiropterans. The Céreste fossil exhibits however slightly primitive wing proportions if compared to the Saint Gérand Aquitanian species.

    Several remarks deal with the peculiar relationships between the ecology of the molossids and their kind of fossilisation, frequently associated with sedimentary facies of the lacustrine type.
      


  PV article infos

Published in Vol. 04, Fasc. 1 (1971)

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Rongeurs nouveaux de l'Oligocène Moyen d'Espagne.
Louis Thaler
Published online: 15/09/1969

Keywords: Cricetidae; Oligocene; Pseudocricetodon; Rodents; Theridomys

https://doi.org/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. 


  PV article infos

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

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Physogaleus hemmooriensis (Carcharhinidae, Elasmobranchii), a new shark species from the early to middle Miocene of the north sea basin.
Thomas Reinecke and Kristiaan Hoedemakers
Published online: 15/10/2006

Keywords: Carcharhinidae; Early Miocene; Elasmobranchii; Hemmoorian; new species; North Sea Basin; Physogaleus

https://doi.org/10.18563/pv.34.e14

  Abstract

    A new carcharhinid shark species, Physogaleus hemmooriensis sp. nov., is described from the Lower Hemmoorian (Behrendorfian, late Burdigalian, early Miocene) of Werder, Lower Saxony, Germany. P. hemmooriensis also occurs in the Edegem and Antwerpen Sands Members of the Berchem Formation, Belgium, and in the Miste Bed, Aalten Member of the Breda Formation, The Netherlands, which have an early to middle Miocene age. In the Western Atlantic region, the taxon is present in the early Miocene Calvert Formation of Delaware, U.S.A, which is largely contemporaneous with the Hemmoorian. 


  PV article infos

Published in Vol. 34, Fasc. 1-2 (2006)

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Book of Abstracts of the XXII Annual Meeting of the European Association of Vertebrate Palaeontologists, 30 June–5 July 2025, Kraków, Poland
Georgios L. Georgalis Logo, Tomasz Sulej Logo, Matteo Belvedere Logo and Marcelo R. Sánchez-Villagra (Eds.) Logo
Published online: 20/06/2025

Keywords: Abstracts; EAVP

https://doi.org/10.18563/pv.eavp2025

  Abstract

    Book of Abstracts of the XXII Annual Meeting of the European Association of Vertebrate Palaeontologists, 30 June–5 July 2025, Kraków, Poland. 


  PV article infos

Published in 48-1 (2025)

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Eocene Teleostean Otoliths, Including a New Taxon, from the Clinchfield Formation (Bartonian) in Georgia, USA, with Biostratigraphic, Biogeographic,
and Paleoecologic Implications
 
Gary Stringer Logo, Dennis . Parmley and Ashley Quinn
Published online: 03/01/2022

Keywords: climate; Congridae; Ophidiidae; Sciaenidae; tectonics

https://doi.org/10.18563/pv.45.1.e1

  Abstract

    Investigations of the Clinchfield Formation (middle Eocene, upper Bartonian) exposed at the Hardie Mine (Wilkinson County, Georgia, USA), produced 4,768 actinopterygian otoliths representing 14 taxa and increased the number of bony fishes threefold from the site. The somewhat limited richness was characterized by bonefishes, mud eels, conger eels, sea catfishes, cusk-eels, snooks, grunts, drums and croakers, and porgies. The assemblage had a relatively even distribution with Ophidiidae, Congridae, and Sciaenidae most common. Included in the otolith taxa was a new sciaenid genus and species, Eosciaena ebersolei, with unknown relationships to other Sciaenidae. The Clinchfield otoliths were compared to other middle and late Eocene in age otolith assemblages in Alabama, Mississippi, and Louisiana utilizing percentage similarity measurements. Analysis indicated that the Clinchfield otoliths were not greatly similar or greatly unlike the Moodys Branch and Yazoo Clay otolith assemblages. However, the Clinchfield showed little relationship to the slightly older Lisbon Formation in adjacent Alabama and is postulated to be related to global climatic and plate tectonic events. Biostratigraphically, the Clinchfield otolith taxa are essentially the same as the other formations except for the Lisbon, which has at least ten unique species. Abundances of Clinchfield otolith taxa indicate a possible sub-bioprovince in the eastern Gulf Coastal Plain. The Clinchfield otoliths indicate a tropical to perhaps subtropical, soft substrate, mainly normal marine to slightly reduced salinities, inner shelf (0–20 m) paleoenvironment with indications of proximal continental coastlines. This investigation represents an initial step in addressing the immensely understudied Paleogene otolith assemblages in Georgia.
      


  PV article infos

Published in 45-1 (2022)

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Designating a lectotype for Mesacanthus pusillus (Gnathostomata: Acanthodii)
Matthew G. Baron Logo and Kevin Seymour
Published online: 03/03/2021

Keywords: acanthodians; Chordata; Devonian; Midland Valley; Orcadian Basin

https://doi.org/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. 


  PV article infos

Published in 44-1 (2021)

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S.I. Data
La poche à phosphate de Ste-Néboule (Lot) et sa faune de vertebres du Ludien supérieur. 12- Fissipèdes (Carnivores)
Louis de Bonis Logo
Published online: 25/09/1978

Keywords: Carnivora; Eocene; Quercy Phosphorites

https://doi.org/10.18563/pv.8.2-4.301-311

  Abstract

    Les Carnivores Fissipèdes de Sainte-Néboule appartiennent tous au genre Cynodictis et semblent constituer une population homogène. Celle-ci se distingue suffisamment des espèces déjà décrites pour constituer un taxon particulier : Cynodictis lacustris neboulensis n. s. sp. . L'étude des variations à l'intérieur de cette population nous a conduit à reconsidérer les critères utilisés pour définir les espèces existantes et à regrouper certaines d'entre elles. Il semble qu'il demeure cependant trois lignées distinctes dans le genre Cynodictis mais le matériel nous paraît encore insuffisant pour traduire cette remarque en termes de systématique. 


  PV article infos

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

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Observations sur l'anatomie crânienne du genre Palaeotherium (Perissodactyla, Mammalia): mise en évidence d'un nouveau sous-genre, Franzenitherium
Jean-Albert Remy
Published online: 01/12/1992

Keywords: Palaeotherium; Paléogène; Perissodactyla; skull anatomy; Systematics

https://doi.org/10.18563/pv.21.3-4.203-224

  Abstract

    The skull remains referred to the genus Palaeotherium are recorded and described. Biometrical tests are made to elucidate intrageneric allometric relationships and to allow comparisons with various other perissodactyls. Apart from the well known shortness of post canine diastems and deepness of the narial opening, the genus is characterized by a great lengthening of the splanchnocranium, owing to a spreading of the post-orbital facial region, by a reduced area of the eye-socket and by the prevalence of the temporal muscle with regard to the masseter; this original shape of the masticatory apparatus needs to be related to the morphology of the jugal teeth and particularly to their  asymmetrical semi-hypsodonty.
        These animals, whose running ability was evidently poor, appear to have been adapted to rather closed environments, feeding on relatively soft vegetable matter; olfactory sense was likely to play a leading part in interindividual and environmental relationships. Such evolutionary trends might explain the disappearance of most of them, as clirnatic conditions deteriorated at the end of the Eocene, before the "Grande Coupure" which affected mammalian faunas at that time.
          Although the present paper is not directly concemed with phylogenetics, it invalidates the supposed ancestor-descendant relationship between P. castrense and P. magnum, and it suggests a possible emergence of the P. medium lineage from a P. siderolithicum stock. Moreover, the structure of the post-orbital facial area allows the  erection of a new sub-genus, Franzenitherium, for the  species lautricense and duvali.

      


  PV article infos

Published in Vol. 21, Fasc. 3-4 (1992)

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On the genus Dikkomys (Geomyoidea, Mammalia)
Morton Green and Philip R. Bjork
Published online: 01/10/1980

Keywords: Dikkomys; Geomyoidae; North America

https://doi.org/10.18563/pv.9.ext.343-353

  Abstract

    The geomyoid genus Dikkomys is well represented in a sample from the Black Bear Quarry Il local fauna of Early Hemingfordian age in Bennett County, South Dakota. Isolated unworn P/4's of Dikkomys matthewi WOOD have a prominent median cristid (sagicristid) with a connection to the metaconid and the hypolophid. With wear, P/4 does not become as molariform as P/4 because of this cristid.
    A large sample of the Whitneyan beteromyid Proheteromys nebraskensis WOOD contains variants of the P/4 with on incipient sagicristid in approximately 18 percent of the population. The upper dentition and lower molars of Proheteromys nebraskensis are sufficiently generalized to indicate probable ancestry to Dikkomys


  PV article infos

Published in Vol. 9, Ext (1980)

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Schmelzmikrostruktur in den inzisiven alt-und neuweltlicher histricognather nagetiere
Thomas Martin
Published online: 15/12/1992

Keywords: Africa; Caviomorpha; Ctenodactyloidea; Deseadan; Enamel microstructure; Hunter-Schreger bands; Hystricognathi; Incisors; Ischyromyoidea; multiserial; Paleobiogeography; pauciserial; Phiomorpha; Rodentia; South America

https://doi.org/10.18563/pv.21.ext.1-168

  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.
      


  PV article infos

Published in Vol. 21, Ext (1992)

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Page 5 of 19, showing 20 record(s) out of 365 total