Taxonomic Composition and Trophic Structure of the Continental Bony Fish Assemblage from the Early Late Cretaceous of Southeastern Morocco

The mid-Cretaceous vertebrate assemblage from south-eastern Morocco is one of the most diversified continental vertebrate assemblages of this time worldwide. The bony fish component (coelacanths, lungfishes and ray-finned fishes) is represented by relatively complete specimens and, mostly, by fragmentary elements scattered along 250 kilometres of outcrops. Here we revisit the bony fish assemblage by studying both isolated remains collected during several fieldtrips and more complete material kept in public collections. The assemblage comprises several lungfish taxa, with the first mention of the occurrence of Arganodus tiguidiensis, and possibly two mawsoniid coelacanths. A large bichir cf. Bawitius, is recorded and corresponds to cranial elements initially referred to ‘Stromerichthys’ from coeval deposits in Egypt. The ginglymodians were diversified with a large ‘Lepidotes’ plus two obaichthyids and a gar. We confirm here that this gar belongs to a genus distinctive from Recent gars, contrary to what was suggested recently. Teleosteans comprise a poorly known ichthyodectiform, a notopterid, a probable osteoglossomorph and a large tselfatiiform, whose cranial anatomy is detailed. The body size and trophic level for each taxon are estimated on the basis of comparison with extant closely related taxa. We plotted the average body size versus average trophic level for the Kem Kem assemblage, together with extant marine and freshwater assemblages. The Kem Kem assemblage is characterized by taxa of proportionally large body size, and by a higher average trophic level than the trophic level of the extant compared freshwater ecosystems, but lower than for the extant marine ecosystems. These results should be regarded with caution because they rest on a reconstructed assemblage known mostly by fragmentary remains. They reinforce, however, the ecological oddities already noticed for this mid-Cretaceous vertebrate ecosystem in North Africa.     

A new species of Lapparentophis from the mid-Cretaceous Kem Kem beds,Morocco, with remarks on the distribution of lapparentophiid snakes

Two isolated trunk vertebrae from the ?uppermost Albian–lower Cenomanian Kem Kem beds of Morocco are described and assigned to Lapparentophis, an early snake genus known from coeval deposits in Algeria. The Moroccan specimens represent a new species, Lapparentophis ragei, which can be distinguished from the type and only known species, Lapparentophis defrennei, by its smaller size, its more elongate vertebrae, the presence of parazygosphenal foramina, and paradiapophyses extending anteroventrally closer to the cotyle. The discovery of Lapparentophis in the Kem Kem beds adds to the relatively diverse snake assemblage previously reported from this formation and extends the geographical range of the genus. The distribution of Lapparentophis and lapparentophiid-grade (?lapparentophiid) snakes is discussed. This poorly known family of terrestrial snakes seems to be restricted to the latest Albian–early Cenomanian of North Africa, with the exception of Pouitella from the early–middle Cenomanian of France. As for many other vertebrate taxa of this period, this distribution is consistent with a dispersal event from Africa to the western part of the European archipelago.     

A new late Cretaceous azhdarchid (Pterosauria,Azhdarchidae) from the Volga Region

A new azhdarchid genus and species, Volgadraco bogolubovi gen. et sp. nov., is described based on an anterior fragment of the mandibular symphysis (mandibular beak) and some postcranial elements from the Rybushka Formation (Upper Cretaceous, Lower Campanian) of the Shirokii Karamysh 2 locality, Saratov Region. The new taxon is intermediate in size and vascularization of the mandibular beak between medium-sized Turonian-Santonian azhdarchids (Azhdarcho, Bakonydraco) and the giant Maastrichtian azhdarchid Quetzalcoatlus.     

New records of Azhdarchids (Pterosauria,Azhdarchidae) from the late Cretaceous of Russia,Kazakhstan, and Central Asia

A review of 12 azhdarchid localities in Russia, Kazakhstan, Uzbekistan, and Tajikistan is given. New records of unidentifiable azhdarchids from the Khodzhakul (Cenomanian), Tyul’keli (Turonian-Coniacian), Kansai (Santonian), Malaya Serdoba, and Beloe Ozero (Campanian) localities and a new taxon, Aralazhdarcho bostobensis gen. et sp. nov. (Shakh-Shakh, Santonian-Campanian), are described.     

A new eusuchian crocodyliform with novel cranial integument and its significance for the origin and evolution of Crocodylia

Crocodyliforms were one of the most successful groups of Mesozoic tetrapods, radiating into terrestrial, semiaquatic and marine environments, while occupying numerous trophic niches, including carnivorous, insectivorous, herbivorous, and piscivorous species. Among these taxa were the enigmatic, poorly represented flat-headed crocodyliforms from the late Cretaceous of northern Africa. Here we report a new, giant crocodyliform from the early Late Cretaceous (Cenomanian) Kem Kem Formation of Morocco. Represented by a partial braincase, the taxon has an extremely long, flat skull with large jaw and craniocervical muscles. The skull roof is ridged and ornamented with a broad, rough boss surrounded by significant vascular impressions, likely forming an integumentary structure unique among crocodyliforms. Size estimates using endocranial volume indicate the specimen was very large. The taxon possesses robust laterosphenoids with laterally oriented capitate processes and isolated epipterygoids, features allying it with derived eusuchians. Phylogenetic analysis finds the taxon to be a derived eusuchian and sister taxon to Aegyptosuchus, a poorly understood, early Late Cretaceous taxon from the Bahariya formation. This clade forms the sister clade of crown-group Crocodylia, making these taxa the earliest eusuchian crocodyliforms known from Africa. These results shift phylogenetic and biogeographical hypotheses on the origin of modern crocodylians towards the circum-Tethyean region and provide important new data on eusuchian morphology and evolution.     

Lower Middle Devonian,Eifelian, crinoids from central Guangxi,South China

The extensive Devonian marine deposits of South China have yielded few articulated crinoid cups or theca. Two Eifelian specimens, from the Gupa Member, are the first ones reported from the Yingtang Formation, Eifelian, from the Ma’anshan section, Guangxi, South China. The new taxon Guangxicrinus xiangzhouensis n. gen. n. sp. is the first report of a marsupiocrinid in China, extending the paleogeographic range of the family into the Paleotethys and the stratigraphic range of the family upward from the upper Silurian into the lower Middle Devonian, Eifelian. The occurrence of Halocrinites sp. is the third occurrence of a cupressocrinitid in China and extends the paleogeographic range from Yunnan to Guangxi.     

Partial mandible of a giant pterosaur from the uppermost Cretaceous (Maastrichtian) of the Hațeg Basin,Romania

We describe and interpret a posterior mandibular symphysis of a very large azhdarchid pterosaur. The specimen LPB (FGGUB ) R.2347 exhibits a series of morphological characters present in both azhdarchid and tapejarid pterosaurs, suggesting a more basal position within the clade Azhdarchidae. This fossil was collected from Maastrichtian continental deposits near V?lioara in the Ha?eg Basin, Romania, but cannot be confidently referred to the contemporaneous giant Hatzegopteryx thambema, also from V?lioara, due to the absence of overlapping skeletal elements. Remarkably, this mandibular symphysis shares a number of features the smaller azhdarchoid Bakonydraco galaczi from the Santonian of Hungary. Additional comparisons with previously described large‐sized azhdarchid mandibles indicate a certain degree of morphological and probably ecological disparity within the group. This specimen represents the largest pterosaur mandible ever found and provides insights into the anatomy of the enigmatic giant pterosaurs.     

Palaeoenvironmental distribution of the Rhaetian dinoflagellate cysts Dapcodinium priscum EVITT, 1961, emend. Below, 1987 and Rhaetogonyaulax rhaetica (SARJEANT) LOEBLICH and LOEBLICH, 1976, emend. Harland et al., 1975, emend. Below, 1987

In almost all Rhaetian marine assemblages of the Tethyan Realm, two dinoflagellate cyst species, Dapcodinium priscum EVITT, 1961, emend. Below, 1987, and Rhaetogonyaulax rhaetica (SARJEANT) LOEBLICH and LOEBLICH, 1976, emend. Harland et al., 1975, emend. Below 1987 are dominant. Thus, when one is relatively frequent the other scarce and vice versa. This paper considers the inverse relationship of the two species in 235 rock samples taken from Rhaetian strata well exposed along the western margin of the Mesozoic intracratonic basin of south-eastern France. The palynological variables recorded from the samples (seven types of phytoclasts and three marine taxa: D. priscum, R. rhaetica and micrhystridids) were submitted to principal components analysis, which shows that D. priscum occurs in deposits that reflect nearshore and restricted marine environments. R. rhaetica is indicative of more marine environments at greater water depth, as indicated by the relatively high proportions of buoyant needle-like phytoclasts. These observations suggest that D. priscum is the cyst of an opportunistic, euryhaline dinoflagellate taxon that occupied various ecological niches while R. rhaetica inhabited more normal open marine environments. The palaeoenvironmental distribution seems to have been influenced by the energy level of the water column. D. priscum is found in deposits that denote high to low energy while R. rhaetica is found in low energy sediments. Micrhystridid occurrences are similar to those of D. priscum; they are uncommon when the abundance of R. rhaetica increases.     

Palynostratigraphie du Callovien-Oxfordien (Jurassique) dans les Terres noires, sud-est France

The Terre noires are monotonous sedimentary deposits comprising thick, dark marls and thin carbonaceous layers. They constitute a lithostratigraphical group known in the major part of the SE French Basin. In the East of this basin this group, dated from late Bajocian to mid Oxfordian, is well developed; on the other hand on the West, it is reduced until it disappears locally on the border of the Massif Central. In the East, the succession is precisely dated by ammonites, whereas in the west, ammonites are not consistently present, and do not permit the same precision. Analysis of dinoflagellate cyst assemblages, at the Callovian-Oxfordian boundary, show that it is possible to correlate the eastern to the western succession. Two marker species allow the correlation of four outcrop sections. The first index, Wanaea fimbriata, is well known; its first appearance datum is exactly at the Callovian-Oxfordian limit in the Boreal and Mediterranean realms. It is the index taxon of the palynological parazone Wfi. The second index, Stephanelytron ceto, an endemic taxon in the SE French, has its last appearance datum within the Scarburghense horizon, the second subzone of the oldest zone of the Oxfordian (Mariae zone). The first section studied was sampled in the east part of the basin (Hautes Alpes department). It corresponds to the maxima of marine deposits and is used as the palynostratigraphical reference. The three other sections analyzed, sampled in the west part of the basin (Ardèche department) where marine deposits are more condensed, are correlated and dated due to dinoflagellate cyst markers observed in the reference section. These results indicate that dinoflagellate cysts are a reliable correlation tool. Batiacasphaera rugosa (Courtinat, 1980) nov. comb is proposed.     

La microflore de diatomées au passage mio-pliocène en Corse

The “Aleria formation”, described in northeastern Corsica, consists of siliciclastic deposits referred to a deltaic environment and comprises diatomitic lenses exposed at Casabianda. The Aleria formation fills a depression of the Messinian erosional surface and is overlain by Early Pliocene sediments in several places. This suggests a late Messinian-earliest Pliocene age. Diatom microflora is well-preserved and contains 59 species. Pennates indicate a very large diversity with 54 species, while Centrics are represented only by five species. Diatom assemblages show a relative constant composition along the studied interval. The species Aulacoseiragranulata is the dominant taxon with about 90% in all samples. Taxa are of different salinity classes and different modes of life (planktic, tychoplanktic, benthic, epiphytic…), suggesting multiple environmental factor interactions. The environmental model suggested by sedimentological and biological data led as to assume a pond-like coastal receptacle common in deltaic system. This receptacle was slightly influenced by the close marine waters and was supplied by permanent freshwaters from continental run-off and alluvial sheet. This model based on diatom assemblages provides new data for palaeoenvironmental and chronological interpretations of the so-called Messinian Lago-Mare deposits.     

Sequence biostratigraphy and paleoenvironmental reconstruction in the Early Eocene Figols Group of the Tremp-Graus Basin (south-central Pyrenees, Spain)

The dinoflagellate cyst, palynofacies and foraminiferal records from the Early Eocene Figols Group of the Spanish Pyrenees exhibit major changes associated with relative sea-level fluctuations and variations in efficiency of the fluvial systems. The mixed siliciclastic-carbonate marine succession exposed in the Merli-Esdolomada area was deposited on the shelf in a tectonically active basin, under oxic conditions, in shallow to moderately deep marine waters (close to the lower boundary of the photic zone) influenced by river discharge from adjacent emerged lands. Sedimentary cycles are mainly recorded by fine-grained deposits. The paleoenvironmental interpretation of palynological and calcareous microfaunal records allows the definition of depositional sequences and enables to trace basinward surfaces identified in more proximal settings by means of sedimentological facies analysis. At the same time, the solid regional stratigraphic framework already available for the Figols Group allows new insights on the paleoecology of extinct taxa.The Merli-Esdolomada section (ME) spans two 3rd order sequences. The upper sequence reflects more marginal marine conditions than the lower one, thus pointing to an overall shallowing trend with time. In the lower sequence the maximum flooding interval is characterised by a rich and diverse microfauna, highest relative abundances of marine phytoplankton and typically neritic dinoflagellate cyst (dinocyst) assemblages dominated by Spiniferites and Cordosphaeridium. The final phase of the highstand systems tract, in proximity of the main sequence boundary, is characterised by a decrease in abundance and diversity of dinocysts, with the dominance of the lagoonal genus Polysphaeridium, and by decreased microfaunal diversity (discorbids, miliolids, larger foraminifers).Palynological records permit the reconstruction of activation and deactivation phases of the fluvial systems, variations in runoff from the hinterland, nutrient delivery to the sea and productivity in surface waters of the Tremp-Graus Basin. The overall abundance of Spiniferites and the scarcity of peridinioid cysts, Lingulodinium, Pediastrum and Botryococcus algae are interpreted to indicate oligotrophic conditions during the deposition of the investigated succession. Recurrent intervals where the temporary disappearance of Spiniferites corresponds to highest relative abundances of Operculodinium and herbaceous debris are the main evidence for river plumes and denote periods of enhanced fluvial discharge reflecting a Milankovitch-type cyclicity. The Rotalia group, which shows abundance peaks of Cuvillierina spp. in the shallower intervals, is often associated with these episodes, thus suggesting for this taxon more tolerance to turbidity than larger foraminifera. Within the maximum flooding zone, a Thalassiphora patula acme corresponding to the local disappearance of Homotryblium is deemed to record the distal expression of a fluvial activation which triggered water salinity stratification. Despite broad morphological similarities, Homotryblium exhibits more cosmopolitan preferences than Polysphaeridium, which is instead confirmed as a lagoonal euryhaline taxon. The increase of Spinizonocolpites pollen toward the top of the Figols Group records the northwestward migration of Nypa mangrove-palms from southern Europe during the mid Early Eocene.     

Isolated theropod teeth from the Kem Kem Beds (Early Cenomanian) near Taouz, Morocco

Thirty-seven well-preserved, isolated theropod teeth from the Early Cenomanian Kem Kem beds, Morocco, are identified by using morphometric data and direct comparison with teeth previously described in the literature. Direct comparison reveals that four different morphotypes (MT 1–4) are present in the sample. The teeth of MT 1 are characterised by unserrated carinae and belong to spinosaurid dinosaurs. The teeth of MT 2–4 have serrated carinae, and our data analysis indicates they are of carcharodontosaurid, dromaeosaurid, and abelisaurid origin. Three types of crown enamel ornamentation are present among the teeth of MT 1, which implies that, apart from Spinosaurus aegyptiacus STROMER 1915, more than one species of spinosaurine theropods may be present in the Early Cenomanian of Northern Africa. Our results also confirm the occurrence of abelisaurids, dromaeosaurids, and carcharodontosaurids in Morocco.     

Reinvestigation of conchostracans (Crustacea: Branchiopoda) from the Permian–Triassic transition in Southwest China

Sedimentary deposits of the Permian–Triassic transition are well-exposed in numerous outcrops of South China. Depending on the palaeogeographic positions of the sections, their lithofacies vary from fully marine, shallow marine, lagoonal, lacustrine, and fluvial to alluvial. In the present study, conchostracans (Crustacea: Branchiopoda) were newly collected from the continental deposits of the Kayitou and Jialingjiang formations around the Kangdian Highland elevated by the Emeishan Basalt in the southern Sichuan, western Guizhou, and northeastern Yunnan provinces. The conchostracan fauna of the Kayitou Formation is composed of Pseudestheria chatangensis, Euestheria fuyuanensis, and Euestheria sp. aff. E. gutta. These species occur in varying lithofacies types of different sections. In particular, the late Permian Pseudestheria chatangensis occurs in grey siltstones interbedded with pebbly sandstones, which are interpreted as lacustrine deposits. Euestheria fuyuanensis and Euestheria sp. aff. E. gutta were obtained from yellowish to greenish–grey clay- and siltstones, interpreted as coastal plain deposits. In comparison to other regions, occurrences of Euestheria gutta are indicative of an early Induan to Olenekian (Early Triassic) age. The fossil record of Euestheria fuyuanensis is so far restricted to a few occurrences in the Kayitou Formation of Southwest China and, therefore, using this species for long-distance biostratigraphic correlation requires further investigation. The distribution of late Permian pseudestheriid and Early Triassic euestheriid species in the respective sections possibly depends on the local lithofacies and, therefore, a diachronous age of the Kayitou Formation within the study area can be assumed. Additionally, Magniestheria sp. aff. M. mangaliensis and Magniestheria sp. aff. M. subcircularis were recorded in the Jialingjiang Formation, which represents a lithostratigraphic unit considered as late Early Triassic (Olenekian). Further investigations of both taxonomy and the real stratigraphic ranges of the conchostracan species as well as cross-correlations with other age data are recommended, in order to better constrain the position of the Permian–Triassic boundary and the specific timing of the terrestrial end-Permian mass extinction in continental deposits of Southwest China.     

A NEW PTEROSAUR FROM THE LIAONING PROVINCE OF CHINA, THE PHYLOGENY OF THE PTERODACTYLOIDEA, AND CONVERGENCE IN THEIR CERVICAL VERTEBRAE

Abstract:  The largest known flying organisms are the azhdarchid pterosaurs, a pterodactyloid clade previously diagnosed by the characters of their extremely elongate middle-series cervical vertebrae. The named species of the Azhdarchidae are from the Late Cretaceous. However, isolated mid-cervical vertebrae with similar dimensions and characters have been referred to this group that date back to the Late Jurassic, implying an almost 60 million year gap in the fossil record of this group and an unrecorded radiation in the Jurassic of all the major clades of the Pterodactyloidea. A new pterosaur from the Early Cretaceous of Liaoning Province of China, Elanodactylus prolatus gen. et sp. nov., is described with mid-cervical vertebrae that bear these azhdarchid characters but has other postcranial material that are distinct from the members of this group. Phylogenetic analysis of the new species and the Pterodactyloidea places it with the Late Jurassic vertebrae in the Late Jurassic–Early Cretaceous Ctenochasmatidae and reveals that the characters of the elongate azhdarchid vertebrae appeared independently in both groups. These results are realized though the large taxon sampling in the analysis demonstrating that the homoplastic character states present in these two taxa were acquired in a different order in their respective lineages. Some of these homoplastic characters were previously thought to appear once in the history of pterosaurs and may be correlated to the extension of the neck regions in both groups. Because the homoplastic character states in the Azhdarchidae and Ctenochasmatidae are limited to the mid-cervical vertebrae, these states are termed convergent based on a definition of the term in a phylogenetic context. A number of novel results from the analysis presented produce a reorganization in the different species and taxa of the Pterodactyloidea.     

Comparison of the Levels of Bacterial Diversity in Freshwater,Intertidal Wetland,and Marine Sediments by Using Millions of Illumina Tags

Sediment, a special realm in aquatic environments, has high microbial diversity. While there are numerous reports about the microbial community in marine sediment, freshwater and intertidal sediment communities have been overlooked. The present study determined millions of Illumina reads for a comparison of bacterial communities in freshwater, intertidal wetland, and marine sediments along Pearl River, China, using a technically consistent approach. Our results show that both taxon richness and evenness were the highest in freshwater sediment, medium in intertidal sediment, and lowest in marine sediment. The high number of sequences allowed the determination of a wide variety of bacterial lineages in all sediments for reliable statistical analyses. Principal component analysis showed that the three types of communities could be well separated from phylum to operational taxonomy unit (OTU) levels, and the OTUs from abundant to rare showed satisfactory resolutions. Statistical analysis (LEfSe) demonstrated that the freshwater sediment was enriched with Acidobacteria, Nitrospira, Verrucomicrobia, Alphaproteobacteria, and Betaproteobacteria. The intertidal sediment had a unique community with diverse primary producers (such as Chloroflexi, Bacillariophyta, Gammaproteobacteria, and Epsilonproteobacteria) as well as saprophytic microbes (such as Actinomycetales, Bacteroidetes, and Firmicutes). The marine sediment had a higher abundance of Gammaproteobacteria and Deltaproteobacteria, which were mainly involved in sulfate reduction in anaerobic conditions. These results are helpful for a systematic understanding of bacterial communities in natural sediment environments.     

A Revision of the Macraster species (Echinodermata,Echinoidea) occurring in the Albian deposits of the Zagros basin,Southwest Iran

The paper describes the spatangoid echinoids belonging to Macraster, which could be found in the Albian deposits (Kazhdumi Formation) at the Anneh anticline situated in Zagros Mountains, Southwest of Iran. The aim is to re-examine, and redefine three species: M. douvillei, M. longesulcatus and M. obtritus. Douvillaster and Macraster genera are synonymized and then the assignment of nominal Tethyan species belonging to the same genera is reviewed. The substantial reduction of species does not strongly impact the biodiversity patterns. Neither the bio-geographical provinciality nor the temporal trends of taxonomic richness are affected. Among the Cretaceous spatangoids, Macraster is a highly specialized taxon that displays outstanding adaptations of the ambulacra to improve in the gaseous exchanges. This, in return, triggers the higher frequency of the taxon in the warm shallow waters of the Tethyan margins, and in oxygen-depleted environments.     

Conodonts from the Permian Jisu Honguer (Zhesi) Formation of Inner Mongolia, China

The Jisu Honguer Formation (“Zhesi Formation”) is a North China marine carbonate unit of Permian age containing a mixed fauna of Tethyan, Boreal and endemic elements. The age of the Jisu Honguer Formation has been thought to range from Artinskian to Kazanian based on previous studies using mostly benthic macrofossils. A typical Mesogondolella aserrata conodont fauna is reported from the lower part of the upper member of the Jisu Honguer Formation in the Ulanqub District, Zhesi area, of northern China. The fauna indicates a Middle Permian (Guadalupian) age, most likely late Wordian to early Capitanian, for the strata yielding conodonts. The whole Jisu Honguer Formation could be assigned to the Wordian to early Capitanian age. The overlying Yihewusu Formation is probably of Capitanian age. There are no Wuchiapingian marine deposits in the Zhesi area. As characteristic of the open sea Guadalupian conodont faunas of the Tethys, smooth Mesogondolella dominate the fauna. The view that all Tethyan Guadalupian conodont faunas consist exclusively of serrated Mesogondolella cannot be confirmed. Three new species are described: Mesogondolella neoprolongata C. - y. Wang, Mesogondolella mandulaensis C. - y. Wang and Wardlawella jisuensis C. - y. Wang.     

Messinian Lago-Mare deposits near the Strait of Gibraltar (Malaga Basin,S Spain)

A new stratigraphic unit (named LM unit) located at the base of the Pliocene marine succession in the eastern sector of the Malaga Basin has been distinguished. This unit is composed of two fining-upward sequences bounded by a discontinuity related to synsedimentary tectonic activity. Both sequences are made up of basal alluvial deposits overlain by subaquatic deposits. The lower sequence contains rich mollusc faunas characterized by bivalves Lymnocardiinae and Dreissenidae of Paratethyan origin, and non-marine gastropods, typical of oligo-low mesohaline shallow waters, and low diversified ostracod faunas of Paratethyan origin (Loxocorniculina djafarovi, Tyrrhenocythere pontica, Euxinocythere (Maeotocythere) praebaquana and Amnicythere propinqua) typical of low mesohaline waters. Alternances of monospecific ostracod assemblages made of Cyprideis agrigentina or oligotypic assemblages made of C. agrigentina and Loxoconcha spp. and richer assemblages made of L. djafarovi accompanied by several Amnicythere spp. and Camptocypria sp.1 characterize the upper sequence, pointing to more unstable environment affected by salinity and depth changes. Some samples collected from this upper sequence yielded rare, planktonic and benthic foraminifera, which could suggest the sporadic establishment of quasi-normal marine conditions in the westernmost Mediterranean during the deposition of this sequence. The palaeontological data and the palaeomagnetic results obtained in both the LM unit and the overlying Pliocene marine sediments restrict the age of the former to the post-evaporitic late Messinian. The age and the environmental conditions correlate these deposits with the Lago-Mare event occurring throughout the Mediterranean before the quick and widespread marine flooding of the Mediterranean at the beginning of the Pliocene.     

The taxonomy,chronostratigraphy and paleobiogeography of glyptosaurine lizards (Glyptosaurinae,Anguidae)

Glyptosaurine lizards (Glyptosaurinae, Anguidae) are an extinct group of heavily armored lizards known from North America, Europe and Asia. Glyptosaurine lizards, taxa that possess fully developed tuberculated dermal armor, appear to have been established in North America by late early Puercan time (To3). “Proxestops,” a taxon distinguished by a combination of vermiculate and tuberculated osteoderm sculpturing, is considered to be a non-glyptosaurine, a sister taxon of the Glyptosaurinae. Known from only fragmentary remains, its wide chronostratigraphic distribution suggests that “Proxestops” is a form genus that, in all probability, represents more than one taxon, that ranges from the middle Paleocene to the early Eocene of North America. Moreover, the taxa Odaxosaurus piger, Parodaxosaurus sanjuanensis and “Proxestops” are best considered “proto-glyptosaurines”. “Melanosaurins” and glyptosaurins were well-established by the early Eocene, especially in North America, and are here documented by their type species and chronostratigraphic levels. Both tribes are present in Europe (MP7), too, but the record is not as estensive as that of North America. The North American taxon Gaultia silvaticus (Wa0) is transitional between a “melanosaurin” and glyptosaurin. Because it lacks the well-defined hexagonal osteoderms that characterize the Glyptosaurini, it is removed from that group and considered to be a “melanosaurin”. The “melanosaurin” taxon “Xestops” savagei (Wa4–Wa6) cannot be referred to Xestops (Br2) based on non-corresponding elements and because superficial similarity does not justify assignment to this taxon. Arpadosaurus sepulchralis (Wa6?), whose holotype is a fragmentary right frontal, is considered a subjective junior synonym of A. gazinorum, based on minor differences in the epidermal scale pattern that probably represent individual variation. “Glyptosaurus” agmodon (Wa6?), based on a partial right maxilla, cannot be referred to Glyptosaurus (sensu stricto), and the material upon which this taxon is based bears strong resemblance to material identified as cf. “?Paraglyptosaurus” yatkolai (Wa5–Wa6). “Glyptosaurus” rhodinos (Wa5) is based on an incomplete parietal, and its reference to Glyptosaurus is considered problematic. Eoglyptosaurus donohoei (Wa7) is probably valid and is re-established here. Glyptosaurus (sensu stricto) is known solely from the middle Eocene (Br2) by G. sylvestris. Dimetoposaurus wyomingensis (Br3) is removed from Xestops vagans because its synonymy was based on superficial similarities. Helodermoides tuberculatus, the largest and last glyptosaurin (Ch3), is restricted to the Chadronian of North America. Only the “melanosaurin” Peltosaurus granulosus (Or2–Or3), which includes the species P. abbotti, seems to have crossed the Eocene-Oligocene boundary, and appears to be largely restricted to the Orellan, but extended into the Arikareean. European glyptosaurines are also represented by both glyptosaurins and “melanosaurins” early in the Eocene (MP7). Placosauriops-like “melanosaurins” are known from Dormaal (MP7), and the glyptosaurin taxon?Placosaurus ragei occurs at the same level. “Placosauriops abderhaldeni” has been identified from the Grube Messel (MP11), but this assignment remains dubious because the species has not been adequately diagnosed, and the holotype species is from the Geiseltal (MP13), which is some 4.5 million years younger. Placosauriops weigelti (MP13) is the only valid species of this genus. Paraxestops stehlini (MP14) is not referable to the North American taxon Xestops, and its relationship to Placosauriops has not been studied. The late Eocene glyptosaurins Placosaurus estesi (MP17) and P. rugosus (MP18) are the last glyptosaurines known from Europe and appear to have gone extinct at the Eocene-Oligocene boundary, casulties perhaps of the “Grande Coupure”. Asian glyptosaurines are known solely from one species, Stenoplacosaurus mongoliensis, from the middle Eocene (Sharamurunian) of China. Glyptosaurines most likely originated in North America, diversified by late Paleocene time, and rapidly spread across the North Atlantic into Europe by the early Eocene. Both “melanosaurins” and glyptosaurins took a foothold in Europe by the early Neustrian, but the glyptosaurins, aside from one occurrence (Dormaal, MP7), were conspicuously absent for most of Neustrian through early Robiacian time. In North America, glyptosaurins diversified during the early and middle Eocene, while in Europe small “melanosaurins” were a prominent part of the paleoherpetofauna, and glyptosaurins are unknown for most of the Neustrian through the Geiseltalian, in both the fossilferous Lagerstätten of Messel and Geiseltal. Stenoplacosaurus is the only known glyptosaurin glyptosaurine from Asia, and its abrupt appearance during the late Eocene suggests the possiblity of a Beringian dispersal from North America into Asia.