Oryctos
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Accès privé :
| volume 3, 2000 |
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David M. Martill & Paulo M. Brito, First record of Calamopleurus (Actinopterygii: Halecomorphi: Amiidae) from the Crato Formation (Lower Cretaceous) of north-east Brazil. Oryctos 3, 3-8.
A partial skeleton represents the first occurrence of the amiid (Actinopterygii: Halecomorphi: Amiidae) Calamopleurus from the Nova Olinda Member of the Crato Formation (Aptian) of north east Brazil. The new specimen is further evidence that the Crato Formation ichthyofauna is similar to that of the slightly younger Romualdo Member of the Santana Formation of the same sedimentary basin. The extended temporal range, ?Aptian to ?Cenomanian, for this genus rules out its usefulness as a biostratigraphic indicator for the Araripe Basin.
Keywords: Amiidae, Calamopleurus, Early Cretaceous, Brazil
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Haiyan Tong & Eugene S. Gaffney, Description of the skull of Polysternon provinciale (Matheron, 1869), a Side-Necked Turtle (Pelomedusoides : Bothremydidae) from the Late Cretaceous of Villeveyrac, France. Oryctos 3, 9-18.
Polysternon is a European side-necked turtle based only on shell material. A skull found from the Late Cretaceous of Villeveyrac, Herault, France, is referred to this taxon because shells clearly belonging to Polysternon provinciale occur in the same beds. The skull of Polysternon shows that it is a bothremydid with the quadrate-basisphenoid covering the prootic ventrally, the eustachian tube separated from the stapes, precolumellar fossa absent, condylus occipitalis consisting only of exoccipitals and an exoccipital-quadrate contact. Polysternon lies in the Bothremys-Group because it has triangular, expanded triturating surfaces, extensive exposure of the palatine on the triturating surfaces, and a supraoccipital-quadrate contact. Polysternon is most closely related to Foxemys. They possess a number of characters in common including an open incisura columellae auris and a deep pterygoideus muscle concavity. Polysternon differs from Foxemys in having a broader midline, palatal depression, a narrower triturating surface with lower labial ridges, and a condylus occipitalis that is placed farther posterior.
Keywords: pleurodire, Polysternon, bothremydid, Late Cretaceous, France
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Yves Laurent, Eric Buffetaut & Jean Le Loeuff, A thoracosaurine skull (Crocodylia, Crocodylidae) in the Late Maastrichtian of Southern France. Oryctos 3, 19-27.
Important crocodilian remains have recently been discovered at a new late Maastrichtian locality near the village of Marignac-Laspeyres (Haute-Garonne, southern France). A skull and some postcranial elements have been referred to the longirostrine crocodilian Thoracosaurus Leidy, 1852, this being its first record from the Upper Cretaceous of France. The skull shows ante-orbital openings similar to those reported by Leidy in 1865 on a skull from New Jersey and hitherto mostly considered as accidental. These openings are reinterpreted and thoracosaurine palaeobiogeography is discussed.
Keywords : Late Maastrichtian, France, Paleobiogeography, Crocodylidae, Thoracosaurus
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Daniel J. Chure, Observation on the morphology and pathology of the gastral basket of Allosaurus, based on a new specimen from Dinosaur National Monument. Oryctos 3, 29-37.
A well preserved and complete gastral basket of Allosaurus (DINO 11541) corrects a number of earlier misinterpretations of this structure in Allosaurus. The basket consists of eighteen rows of gastralia. The first row has only one element per side and these do not overlap medially but rather form a cranially facing notch. All other rows have two elements per side, the medial one being the longer. The right and left medial elements overlap at the midline of the basket. Allosaurus has only four elements per gastral row. Previous interpretations for Allosaurus have been as high as nine elements per row. The supposed fused, V-shaped median gastral element is now known to be a furcula. The supposed four lateral elements in USNM 4734 are actually all part of a single medial element injured during life and healed as a series of pseudoarthroses. The presence of pseudoarthroses and calluses in other medial gastral elements of USNM 4734 further support this interpretation. The presence of similar pathologies in the gastralia of another specimen of Allosaurus (USNM 8367) as well as in the dorsal ribs specimen of Acrocanthosaurus atokensis (SMU 74646) suggests that such injuries were not uncommon in allosauroid theropods. These injuries may be the result of either struggles with prey or intraspecific behavior, such as kicking or head-flank butting. Keywords: Dinosauria, Theropoda, Osteology, Allosaurus, Gastralia, Jurassic, Morrison, Pathology
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Erika Posmosanu & Elizabeth Cook, Vertebrate taphonomy and dinosaur palaeopathology from a Lower Cretaceous bauxite lens, North West Romania. Oryctos 3, 39-51.
The Lower Cretaceous bauxite lens at Cornet, North West Romania, was deposited in a karstic environment as part of a system of sink holes, probably on an island in the Tethys Ocean. This bauxite lens has yielded thousands of bones and bone fragments since the initial excavations in 1978. The fauna is of restricted taxonomic diversity, and consists predominantly of ornithopod dinosaurs and rare pterosaurs. The bones have a limited size range, show a wide range of abrasion characteristics, are frequently broken and show little or no evidence of in situ weathering damage. Sorting of the skeletal elements is apparent: vertebral centra are over-represented in the collection. Of particular note are a few bones with evidence for predation or scavenging, in the form of circular punctures and elongate grooves, and pathological damage, including abnormal bone growth.
Keywords: Lower Cretaceous, Bauxite, Karst, Dinosaur, Taphonomy, Palaeopathology, Romania
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James W.R. Martin, Cyril A. Walker, Richard H.C. Bonser, and Gareth J. Dyke, A new species of large auk from the Pliocene of Belgium. Oryctos 3, 53-60.
A new species of fossil auk, Alca stewarti from the Kattendijk Sands Formation (early Pliocene) of Belgium is described. Preserved elements of this new species include humeri and ulnae, all of which are longer than those of the largest auk currently known, the recently extinct Great Auk (Pinguinus impennis). The relative proportions and structure of these wing elements, together with our estimates of body mass and wing loading suggest that this new species was capable of flapping flight. We consider the biomechanical implications for a large flighted auk, and speculate on the lifestyle and appearance of this new species. We also estimate the likely flight speed and flapping frequency of Alca stewarti.
Keywords: Auk, Belgium, Pliocene, Flight
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Dominique Delsate, Presence of a small Multituberculata at the Paleocene-Eocene transition of Dormaal (Belgium, MP7). Oryctos 3, 61-69.
Successive field campaigns and sediment sortings from the Belgian locality Dormaal, well known by its abundant mammalian fauna, yielded only two Multituberculate teeth. Despite identification possibilities of these anterior premolars are very poor, they are assigned to Neoplagiaulacidae incertae sedis.
Keywords: Multituberculata, Neoplagiaulacidae, Paleocene-Eocene transition, MP7, Dormaal, Belgium
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Norihisa Inuzuka, Preliminary Report on the Evolution of Aquatic Adaptation in Desmostylians (Mammalia, Tethytheria). Oryctos 3, 71-77.
Forty nine trends indicating aquatic adaptation are recognized based on the distribution of osteological characters in 16 species of four living mammalian taxa. Among them, 39 trends are also found in desmostylians. In the present paper their distribution is examined in four genera of Desmostylia, for which skeletons are known, i.e. Behemotops and Paleoparadoxia (family Paleoparadoxiidae), and Ashoroa and Desmostylus (family Desmostylidae). Characters inserted on the phylogenetic tree elucidate the evolution of aquatic adaptation within the order Desmostylia. The present paper introduces preliminary results: although the phylogenetic divergence of the two families shows no relation to aquatic adaptation, the Desmostylidae became more adapted to aquatic life than did the Paleoparadoxiidae, with Desmostylus representing the highest level of aquatic specialization on present fossil evidence.
Keywords: Desmostylia, aquatic adaptation, comparative morphology, functional morphology
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Jason S. Anderson and Lawrence G. Barnes, A Fossil Miocene Whale from the Tipam Sandstone, St. Martin's Island, Bangladesh. Oryctos 3, 79-84.
The first vertebrate fossil, a lumbar vertebra from a mysticete whale, known from the Tipam Sandstone of the Bengal Basin is presented and described. Large mysticete remains from Miocene deposits surrounding the Indian Ocean are exceedingly rare, making this specimen, while isolated, important for discussions of cetacean evolution and biogeography, as well as for understanding the geologic context of St. Martin's Island. Miocene Asian Cetacea are known from fragmentary material, requiring the reduction of two nominal taxa, Mioceta bigelowi and Mioceta magna, to nomina dubia.
Keywords: Mysticeti, cetacean, Tipam Formation, Bengal Basin
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Federica Marcolini , Giovanni Zanchetta & Francesco Paolo Bonadonna, Some preliminary data on two small mammal bearing paleosols from the Tyrrhenian and Adriatic sides of Italy. Oryctos 3, 95-94.
Two Middle Pleistocene paleosols from the Tyrrhenian (Campani quarry, Pisa, Lower Valdarno) and Adriatic (Catignano, Pescara) sides of Italy, both covered by tephra layers, were studied for their paleontological content (molluscs and small mammals). At Campani quarry the volcanic ash level was dated by fission tracks both on glass (0.59±0.08 Ma; 0.62±0.07 Ma) and on the apatites (0.46±0.05 Ma). Stratigraphic evidences suggest a Middle Pleistocene age for Catignano paleosol. However, age determination on the apatites belonging to the Catignano volcanic level is currently under way. The Campani quarry paleosol yielded a rich assemblage of land molluscs characterised by high species diversity indicating that a wooded environment developed in conditions of mild climate. The small mammal assemblage is dominated by murids, confirming the presence of a developed wood cover. Catignano paleosol shows a lower number for species of both small mammals and molluscs, the latter dominated by open ground and steppe taxa. A comparison between these two Middle Pleistocene levels shows that molluscs and small mammals data agree suggesting that different environmental conditions prevailed when the two paleosols developed.
Keywords: Biochronology, Small mammals, Molluscs, Middle Pleistocene, Central Italy
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Eric Buffetaut, Mantell, Cuvier, Buckland and the identification of Iguanodon : a correction. Oryctos 3, 95-97.
Contrary to what was claimed by the author in a previous paper, Cuvier did use the name Iguanodon in his palaeontological works, both in the third edition (and subsequent ones) of his Discours sur les révolutions de la surface du globe (1825), and in the captions of figures illustrating teeth from Tilgate Forest in the last edition of Recherches sur les ossemens fossiles. However, the name Iguanodon never appeared in the main text of the Recherches.
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