Hervé Lelièvre

PRIMITIVE JAW STRUCTURE IN AN ARTICULATED BRACHYTHORACID ARTHRODIRE (PLACODERM FISH; EARLY DEVONIAN) FROM SOUTHEASTERN AUSTRALIA

Abstract A unique ‘buchanosteid’ arthrodire specimen from Emsian limestones at Burrinjuck represents the complete articulated remains of the head and cheek, and most of the trunk armor bones from a single fish, together with well-ossified braincase and jaw cartilages. The structure of the toothplates and jaws are described, and compared with primitive brachythoracid material from Saudi Arabia of similar age. Both the palatoquadrate and meckelian cartilages are well preserved, and perichondrally ossified as single elements. As previously described in some phlyctaeniids, the dermal gnathal elements carry crowded denticles similar to the normal tubercular ornament, enlarged along anterior and lateral margins. Six characters concerning gnathal plates of brachythoracids, which have been used in phylogenetic analysis, are discussed and reformulated.

The biostratigraphical and palaeogeographical framework of the earliest diversification of tetrapods (Late Devonian)

Abstract The earliest diversification of tetrapods is dated as Late Devonian based on 10 localities worldwide that have yielded bone remains. At least 18 different species are known from these localities. Their ages span the ‘middle’–late Frasnian to latest Famennian time interval, with three localities in the Frasnian, one at the F/F transition (though this one is not securely dated) and six in the Famennian. These localities encompass a wide variety of environments, from true marine conditions of the nearshore neritic province, to fluvial or lacustrine conditions. However, it does not seem possible to characterize a freshwater assemblage in the Upper Old Red Sandstone based upon vertebrates. Most of the tetrapod-bearing localities (8 of 10) were situated in the eastern part of Laurussia (=Euramerica), one in North China and one in eastern Gondwana (Australia), on a pre-Pangean configuration of the Earth, when most oceanic domains, except Palaeotethys and Panthalassa, had closed.

Thermal strategies and energetics in two sympatric colubrid snakes with contrasted exposure.

The thermoregulatory strategy of reptiles should be optimal if ecological costs (predation risk and time devoted to thermoregulation) are minimized while physiological benefits (performance efficiency and energy gain) are maximized. However, depending on the exact shape of the cost and benefit curves, different thermoregulatory optima may exist, even between sympatric species. We studied thermoregulation in two coexisting colubrid snakes, the European whipsnake (Hierophis viridiflavus, Lacépède 1789) and the Aesculapian snake (Zamenis longissimus, Laurenti 1768) that diverge markedly in their exposure, but otherwise share major ecological and morphological traits. The exposed species (H. viridiflavus) selected higher body temperatures (~30°C) than the secretive species (Z. longissimus, ~25°C) both in a laboratory thermal gradient and in the field. Moreover, this difference in body temperature was maintained under thermophilic physiological states such as digestion and molting. Physiological and locomotory performances were optimized at higher temperatures in H. viridiflavus compared to Z. longissimus, as predicted by the thermal coadaptation hypothesis. Metabolic and energetic measurements indicated that energy requirements are at least twice higher in H. viridiflavus than in Z. longissimus. The contrasted sets of coadapted traits between H. viridiflavus and Z. longissimus appear to be adaptive correlates of their exposure strategies.

GNATHOSTOME MICROREMAINS FROM THE LOWER DEVONIAN JAWF FORMATION, SAUDI ARABIA

Abstract Calcareous horizons in the Qasr and Hammamiyat members (Lower Devonian, ?Pragian and lower Emsian) of the Jawf Formation, northwestern Saudi Arabia, yielded a rich assemblage of microremains from acanthodian, placoderm, chondrichthyan, and sarcopterygian vertebrates. The most abundant elements are scales from acanthodians Nostolepis spp., Milesacanthus ancestralis n. sp., Canadalepis? sp., and Gomphonchus? fromensis, scales and dermal bone fragments from acanthothoracid and ?rhenanid placoderms, and teeth from onychodontids. Rarer occurrences include ?chondrichthyan scales of several different morphotypes, and petalichthid and ?ptyctodontid placoderm elements. The Qasr Member assemblage shows a close resemblance to slightly older faunas from the Lochkovian of Brittany and Spain. The Hammamiyat Member microvertebrate fauna shows closest affinity with that of the stratigraphically lower Qasr Member, with similarities also to coeval faunas from southeastern Australia, late Emsian/Eifelian faunas from west-central Europe, and the Givetian Aztec Siltstone fauna from Antarctica.

Rhombichthys intoccabilis, gen. et sp. nov. (Ellimmichthyiformes, Clupeomorpha, Teleostei), from the Cenomanian (Upper Cretaceous) of Ein Yabrud, Middle East: Anatomical Description and Phylogenetic Implications

ABSTRACT A new double-armored member of the Ellimmichthyiformes (Clupeomorpha, Teleostei) is described from the Cenomanian (Upper Cretaceous) of Ein Yabrud, near Ramallah, Middle East. The anatomical description of Rhombichthys intoccabilis, gen. et sp. nov., is based on 13 subcomplete or incomplete acid-prepared specimens. This taxon shows several remarkable characters such as an important dorsoventral elongation of the lateral wings of the ventral scutes that give an apex-shaped ventral profile in the biggest specimens. Some dorsal fin rays are very extended and branched, and the dorsal fin extends along the major part of the dorsal margin of the body. Rhombichthys intoccabilis, gen. et sp. nov., shares the synapormorphies of the family Paraclupeidae and the subfamily Paraclupeinae. It appears closely related to the genera Triplomystus and Ezkutuberezi, mainly in the basis of the shape of dorsal and ventral scutes and the absence of a hypural diastema.

Microremains of vertebrate near the devonian-carboniferous boundary of Southern China (Hunan province) and their biostratigraphical significance

Abstract Microvertebrate remains of chondrichthyans, acanthodians, actinopterygians and sarcopterygians have been collected in three sections of Central Hunan, China. The investigated sections show Upper Devonian formations of which one, the Malanbian Formation, bears localy the Devonian-Carboniferous boundary. The other sections having yielded microremains of vertebrates belong to the Tuzitang and to the top of the Magunao Formations respectively dated as crepida and marginifera conodont zones. A new species of Orodus, O. aramisi nov. sp. is erected and based on a tooth. The significance of these microremains, specially that of chondrichthyans, is analysed. They do not appear to have more importance than other higher taxa for the discussion of the Devonian-Carboniferous boundary in China, elsewhere their importance is questionable. In the Hunan and Guizhou Provinces mainly two taxa, Protacrodus orientalis and Acanthodes guizhouensis could provide pertinent information on the Devonian-Carboniferous boundary and biostratigraphy. Although our present knowledge remains poor, comparisons with Belgian microvertebrate faunas of the same age are tentatively drawn.

A new placoderm fish (Acanthothoraci) from the Early Devonian Jauf Formation (Saudi Arabia)

ABSTRACT An exceptionally well-preserved new acanthothoracid (placoderm fish) presenting complete endocranium and skull roof, from Saudi Arabia (Qasr Limestone Member, Jauf Formation), Early Devonian in age, is described as Arabosteus variabilis n. gen., n. sp. Compared to other Acanthothoraci, the new taxon exhibits a skull roof variable in its dermal plate distribution (e.g., a supernumerary plate: the posterior central plate) and sensory line pattern. Even the different specimens of this taxon show such variability between them. Arabosteus variabilis n. gen., n. sp. enlarges the scope of our knowledge of Acanthothoraci and Placodermi in general. Traditionally, the Arthrodira, one of the historically earliest described groups, provide the standard reference model for the placoderm skull roof pattern. The interpretation of the acanthothoracid skull roof pattern of the Saudi taxon from an arthrodiran model and the establishment of homologies is impossible to resolve unless based on prior assumptions (e.g., hypothesis of fragmentation or fusion for the paranuchal plate complex). The lateral line system of A. variabilis n. gen., n. sp. is unstable (e.g., presence or absence of the postmarginal sensory line canal) making it ambiguous to define bone homology and terminology. Consequently spatial distribution of skull roof plates has been retained for such a task with a minimal reference to the instable features of the sensory line groove distribution.

Two Syntopic Colubrid Snakes Differ In Their Energetic Requirements and In Their Use of Space

Abstract Spatial ecology is crucial to determining how animals exploit resources in their environment. Snakes display highly varied energetic and space use strategies; we hypothesized that snakes with higher energy demands are more mobile to fulfill their energy needs. We studied the spatial ecology of two syntopic colubrid snakes (Hierophis viridiflavus and Zamenis longissimus) that show a marked divergence in energetics. Specifically, we predicted that H. viridiflavus should be more active than Z. longissimus because of its higher energy requirements. Because reproductive status also influences movement patterns, we investigated its effect within each species. We indeed found that H. viridiflavus moved more frequently and covered longer distances during the postreproductive period, probably because of foraging activity. Both species displayed similar activity during the reproductive period, however. The extended movements during the reproductive period may be related to mate-searching in males and egg-laying in females.

New paleontological and geological data about Jbel Tselfat (Late Cretaceous of Morocco)

The ridge of Jbel Tselfat is located at about 30 km north of Meknes (Morocco). It is composed of a Jurassic core surrounded by Miocene levels. Some fossiliferous outcrops of black shales, dated from Late Cretaceous, are present in a thrust sheet in the north and east. Jbel Tselfat was carefully explored by the French paleontologist Arambourg, between 1934 and 1954, and a large amount of actinopterygian fishes has been collected from two localities, Aïn el Kerma and Sigda. In the framework of the ongoing collaborative Franco-Moroccan research project, a fieldwork has been carried out in autumn 2008 in three sites near Aïn el Kerma and in Sigda. An abundant material has been collected. This new fish assemblage is dominated by dercetids, but yielded also pycnodonts, clupavids, protostomiids and acanthopterygians. Other taxa never observed until now in this locality have been found associated with fishes, such as one ammonite and several plant remains. Ongoing geological studies and thin sections analysis allow a better understanding of geological and paleoenvironmental contexts of these vertebrate bearing strata of Jbel Tselfat. They show a deep and quiet marine paleoenvironment, probably close to the coast, in good agreement with Arambourgs ideas. Comparison with other ‘mid-Cretaceous’ fossil fish localities permits to review the dating of Jbel Tselfat and considers it close to the Cenomanian–Turonian boundary. The deposition of black shales is possibly associated to the Oceanic Anoxic Event 2.

Palaeozoic vertebrates ofnorthern France and Belgium. Part I: Heterostraci; Osteostraci; Thelodonti; Placodermi (Devonian)

Abstract Heterostraci; Osteostraci and Thelodonti are known from the Lower Devonian of the Ardenne Allochthonous unit of the Palaeozoic orogen encountered between the Strait of Dover and the Rhine river; in northern France and southern Belgium. Heterostracans have been used to define six interval biozones from the lowermost Devonian up to the Emsian. Osteostracans are rare. Thelodonts correlate with other Lower Devonian sequences of the southern margin of the Old Red Continent. Placoderms are known from the Lochkovian (lower Lower Devonian) up to the Famennian (upper Upper Devonian); from both the Ardenne Allochthonous and the Brabant Parautochthonous units of the orogen. They are represented mainly by endemic species. The richest placoderm fauna is upper Famennian in age. No Eifelian record has been confirmed.