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. 

Le présent volume est l'aboutissement d'un projet né il y a presque cinq ans. En décembre 1991, l'un d'entre nous (MG) prenait des contacts en vue de proposer un symposium sur les mammifères fossiles, dédié à D.E. Russell, dans le programme du 4e Congrès de la European Society for Evolutionary Biology. Ce congrès, baptisé "Evolution 93", devait se tenir à Montpellier en août 1993. Son Comité d'Organisation, animé par F. Catzeflis, recherchait des organisateurs de symposiums. L'idée fut acceptée avec enthousiasme par le second d'entre nous (PDG), et le titre de notre Symposium fut précisé: " Palaeobiology and Evolution of Early Cenozoic Mammals - A Symposium in Honor of D.E. Russell". Le projet fut formellement accepté par le Comité d'Organisation en avril 1992. 

Lalieudorhynchus gandi gen. nov. and sp. nov. is a new caseid synapsid from the Permian of the Lodève Basin, Occitanie, France. This new taxon is represented by a partial but well-preserved postcranial skeleton, and is characterized by the following apomorphies: a transverse section of the sacral and anterior caudal neural spines with a very thin keel-like process anteriorly, a slender dorsal tip of the dorsal and caudal spines, a narrow distal end of the first sacral rib, a fossa on triceps process of metacoracoid, and a very large distal tarsal 1 of same width than the astragalus, with nearly all sides being shallowly concave.
The skeleton corresponds to a sub-adult individual that was excavated from the La Lieude Formation dated as Roadian-Capitanian (Guadalupian). A sedimentological and taphonomical analysis of the type locality, together with preliminary osteohistological observations, suggest that this new French caseid was rather aquatic, as already hypothesised for other large forms.
A phylogenetic analysis of caseids is performed to test the position of this new taxon and to better understand the evolution of the clade: interestingly, Lalieudorhynchus gandi gen. nov. et sp. nov. is closer to the NorthAmerican “Cotylorhynchus” hancocki than to the other French caseids Ruthenosaurus and Euromycter from the Artinskian of the geographically closer Rodez Basin. These two last caseids document the Artinskian radiation of the clade, which remained diverse until Olson’s extinction. Caseids survived, as Lalieudorhynchus is one of the youngest representatives of the clade, and may have used novel ecological strategies to access their vegetarian food sources.

  

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. 

When the first edition of Mike Benton’s Vertebrate Palaeontology came out in 1990, sauropods still dragged their tails on the ground, the closest relatives of whales were mesonychids, and Mesozoic birds consisted essentially of Archaeopteryx, Ichthyornis and Hesperornis. Twenty-five years later, the book, now in its fourth edition, is a third longer, in a larger format and sports fine colour plates – in addition to a companion website. 

The description of original material of anthracothere and proboscidean in the new locality of Bir el Ater 3 from East Algeria, and a thorough review of early Libycosaurus remains of Bir el Ater 2 allows us validating L. algeriensis as the smallest and earliest species of Libycosaurus and probably the earliest migrant of the genus from Asia. The presence of a Tetralophodon in the Neogene Nementcha formation might represent the earliest occurrence of the genus in Africa. These original fossil remains allow us to discuss the age of the Neogene part of the Nementcha formation close to the Serravalian/Tortonian boundary. 

Suite à la récente publication d'une révision systématique des Chiroptera Vespertilioninae, conduite sur la base des morphologies dentaires comparées (Menu 1987), une remarque bienveillante du Dr. V. Aellen (Muséum d'Histoire Naturelle de Genève) a attiré l'attention de l'auteur sur un point précis du Code International de Nomenclature Zoologique. 

The fauna studied in the following work involves the dentitions and skulls more or less complete of 5 genera, among which only Cephalomys was previously known by its skull. One must notice that the Salla's species of this genus is a new one. Sallamys, rather small, shows a dentition rather similar to that of Platypittamys Wood from Patagonia. The upper molars, more primitive than those of this last genus, according to the smaller dimensions of the hypocone, retain a distinct metaloph. This metaloph tends to be reduced in a way which may give us a possibility to understand how it disappeared in Platypittamys. The upper P4 can be compared as well to that of Platypittamys as to that of Gaudeamus from the African Oligocene. The lower P4, more molarized than that of Platypittamys, is already moving towards the miocene type of structure. The infraorbital foramen is wide and the insertion of the masseter on the muzzle is spacious. Branisamys, genus of a great size, shows an auditory region partly preserved, peculiarly the promontorium with the fenestra rotunda, entirely of the Hystricognathi type. Upper molars are very clearly pentalophodont. A new reconstruction is proposed for the tooth called Villarroelomys by Hartenberger. This tooth is shown to be a lower D4, perhaps of Branisamys , certainly of a rather nearly allied form, and Hartenberger does agree with the essential part of this new conclusion. Of Incamys, two incomplete skulls are known, each one being admitted to be the type of a distinct species, the first one being I. bolivianus, I. pretiosus the second. The infraorbital foramen is of a great size and the impression of the masseter on the muzzle is spacious. The sphenopalatine foramen is widely developed and of a really very uncommon great size. Only Thryonomys from Africa shows a similar tendency to the enlargement of this foramen, but not so extreme. The main basicranial foramina can be observed. The upper teeth, hemi-hypsodont, show, either a vestigial metaloph, similar to that of recent Thryonomys from Africa, associated with a well developed mesoloph, either a well developed metaloph, while the mesoloph is reduced or absent. Cephalomys was previously known by anterior parts of the skull showing a wide infraorbital foramen and a spacious facial insertion of the masseter. Its lacrymal is of the phiomorph type and the spheno-palatine foramen is seemingly of great size, like in Incamys. The species is new. The varied peculiarities of the upper teeth of these genera can be easily understood if we refer to the plan of the teeth of Phiomys andrewsi from the Oligocene and Miocene of Africa. The structure of this genus, clearly more primitive, still typically brachyodont, shows and clearly explains the fundamental coherence of the varied realisations arised from such a structure. Luribayomys n.g. is known only by an anterior half of a skull without teeth. It is remarquable by the great development of the masseter's insertions on the muzzle and by the lacrymal region, well preserved, typically phiomorphid. The classification previously published by A.E. Wood and B. Patterson is granted in its essential parts, provisionally, but not as a definitive solution. Nevertheless the Dasyproctidae are integrated within the Cavioidea, following the conclusions of Bugge and of Vucetich, reached independently. The conclusion emphasizes the exceptional meaning of the fauna of Salla-Luribay. This shows that Platypittamys, while interesting, can no more be supposed certainly representative of the normal structure of the Oligocene Caviomorph, and not even of their ancestors. The anatomical peculiarities exhibited in these new samples, auditory region, lacrymal, spheno-palatine foramen, reinforce the primitive structural identity with the Phiomorpha. Similarly, the new lower D4 favour very close relationships, ever if the affinities of the D4 has been questioned or minimized by Wood and Patterson. It is certainly possible to admit that parallelism could explain limited similarities, like the presence in North America of Rodents with an hystricomorph type of infraorbital foramen and an hystricognath mandible. But if the parallelism could be a sufficient explanation of the identical association of multiple and complete structures observed in the Caviomorpha and Phiomorpha, all the Zoological systematic would have to be questioned. The last positions of A.E. Wood on the subject (1975) are revised and criticised, and the recent publications studying the problems of distance between Africa and South America in Eocene time, as a consequence of the drift, are quoted; the possibility of transportation by rafts is shown. A new hypothesis is proposed about the interrelationships of Pentalophodont Rodents, with interesting paleobiogeographic implications. 

The Tertiary of the Salla-Luribay basin consists of red beds affected by the second period of the andine compression, of Miocene ending age. The Tertiary layers are exposed at an approximate elevation of 3.500 to 4.000 meters. Two stratigraphic units can be distinguished in them: the Luribay conglomerates, in which vertical clifts result from erosion, and the Salla layers consisting mostly of consolidated clays. These clays are very fossiliferous and have furnished a rich vertebrate fauna which gave to R. Hoffstetter the possibility to establish the Oligocene age of these beds. Sediments of same age has been reported to be present in several other places of Bolivia, particularly near Lacayani, where have been collected highly hypsodont Rodents, different from those found in Salla-Luribay basin. 

Based on material from 30 localities, morphologic dental, cranial and biometric analyses have permitted the characterization of two parallel Issiodoromyine lineages, and also the definition of diverse species representing several evolutive stages. Thus it is that new lineages complete the contribution made by the Theridomyinae and Cricetidae and permit, for the Quercy in particular, additional precision in the biochronologic succession of the localities. One of the lineages is limited to the genus Pseudoltinomys LAVOCAT; the other evolves from the genus Elfomys HARTENBERGER to the genus Issiodoromys BRAVARD in GERVAIS. The latter is affected by profound anatomical changes due to a functional modification of the mastication apparatus. These changes seem to be able to be put in relation with the aridification and cooling of the climate at the end of the Eocene. At the end of the middle Oligocene, a new chewing structure is achieved. It is found in diverse living rodents that inhabit a rather arid steppe environment (Cavia, Pedetes, Ctenodactylus). To these supposed nearby ecologic conditions, these rodents have responded in a convergent fashion. It is possible to attribute to the extreme specialization of Issiodoromys its incapacity to adapt to the new climatic crisis of the end of the Oligocene. The arrival of immigrants may be considered as another cause of its disappearance at this time, complementary or not with the first. 

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.

  

Editorial for celebrating the publication of the volume 20.

La revue PALEOVERTEBRATA a été fondée en 1967 par Louis THALER, à une époque où il n'existait, au plan international, que deux périodiques uniquement consacrés aux vertébrés fossiles. Actuellement ce nombre n'est que de quatre. A l'origine la revue fut essentiellement créée pour diffuser les résultats des chercheurs du Laboratoire de Paléontologie de l'Université de Montpellier, alors en début d'expansion et plusieurs thèses et de nombreux travaux directement liés à des thèses y furent publiés ce qui n'excluait déjà pas la publication d'articles d'auteurs étrangers.
[...] 

New and hitherto unpublished mammals from the stratigraphical levels Unterkohle, Untere Mittelkohle and Obere Mittelkohle of the Geiseltal near Halle, GDR, are described (= biochronological levels MP 11-13, Geiseltalian sensu Franzen & Haubold 1986a, b). The marsupial taxa Amphiperatherium aff. maximum (MP 12), A. goethei (MP 12), and Peratherium aff. monspeliense (MP 12 and 13) are recorded for the first time. A lectotype for Amphiperatherium giselense is designated, and the alleged primate Microtarsioides voigzi is assigned to Marsupialia, incertae sedis. A new insectivore species, Saturninia ceciliensis n. sp., is described (MP 13). The anteater Eurotamandua joresi is recorded for the first time outside its type locality, Grube Messel, FRG (MP 11). The present humerus and ulna display the autapomorphic features of the myrmecophagids. 

Valverde's cenogram method is used to analyse mammalian communities from the late Eocene to late Oligocene of southern France, mainly from the "Phosphorites du Quercy". Cenogram analysis involves plotting the size of each component species in a fauna on a semilog diagram in rank order, permitting fossil faunas to be compared with Recent ones. The configurations of Recent communities serve as models for establishing the general environmental characteristics of fossil mammalian faunas. This method of analysis applied to faunal sequence can reveal major and sudden ecological perturbations. The paleobiogeographical event (i.e. the mammalian immigration wave) at the Eocene-Oligocene Boundary in western Europe, known as the «Grande Coupure", is here shown to represent a drastic and sudden ecological change: late Eocene tropical environments in Europe deteriorated rapidly turning to subdesert or desert environments al the beginning of the Oligoccne. 

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. 

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.
  

There is only one suid known in the Upper Miocene of Montredon (Hérault): Microstonyx (Limnostonyx nov. subgen.) antiquus (KAUP). It is differenciated from Microstonyx major by the presence of upper and lower canines which are considerably longer and biger. Its presence at Montredon corroborates the palustrine habitat for the species. 

The genus Parasteiromys AMEGHINO, 1904 is revalidated, and P. friantae sp. nov. (Hystricognathi, Erethizontidae) from Colhuehuapian (early Miocene) sediments of the southern cliff of Colhue-Huapi Lake (Province of Chubut, Argentina), is described. The molar morphology of these taxa and of living porcupines adds new elements to understand the dental evolution of the Erethizontidae, and to propose the hypothetical ancestral molar pattern for this family. This pattern does not correspond to any of the morphologies traditionally proposed as ancestral for South American hystricognathous rodents. The proposed pattern is characterized by a metaloph disconnected from the posteroloph and oriented towards the hypocone, and the third loph incompletely developed with the lingual portion homologous to the mesolophule of Baluchimyinae (Chapattimyidae) from the Miocene of Pakistan. The inferred steps of the molar evolution of erethizontids towards the pentalophodont condition, considered derived for the family, are illustrated. This study strengthens the hypothesis placing erethizontids in a basal position among rodents of the suborder Hystricognathi.

  

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). 

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.