Oryctos
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Accès privé :
| volume 1, 1998 |
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Gilles Cuny, Primitive neoselachian sharks : a survey. Oryctos 1, 3-21.
A study of the ultrastructure of the enameloid of isolated teeth demonstrates that the neoselachian sharks, characterized by a triple-layered enameloid, radiated just after the Carnian, at the same time as some "experimental", poorly known sharks (Vallisia, Raineria, Pseudodalatias and Doratodus). Most of the Triassic neoselachian teeth share a hybodont-like architecture of the crown and a well-developed lingual torus in the root. These latter can be traced back at least in the Early Triassic. The clade Eunemacanthus + Amelacanthus + Hopleacanthus + Acronemus + Neoselachii may have appeared as far back as the Carboniferous. Isolated Palaeozoic teeth belonging to Mcmurdodus and Anachronistes may not belong to neoselachian sharks. Most likely, these isolated teeth represent the result of a convergence phenomenon in tooth morphology and vascularisation.
Keywords: Neoselachii, early evolution, Palaeozoic, Triassic, enameloid ultrastructure.
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Paul H. Lambers, The genus Furo (Pisces, Halecomorphi) from the Upper Jurassic Plattenkalke of Germany. Oryctos 1, 23-35.
An overview of the species assigned to the genus Furo found in the German lithographic limestones of the Solnhofen-area (Bavaria) and Nusplingen (Baden-Wurttemberg) is presented and the monophyly of the Upper Jurassic Furo is discussed. Six species can be recognized: 'F.' latimanus, 'F.' longiserratus, 'F.' microlepidotes, 'F.' aldingeri, 'F.' angustus and 'F.' munsteri. Among these 'F.' angustus and 'F.' munsteri form a monophyletic group, to which 'F.' aldingeri might be related as well. 'F.' longiserratus might be closely related to the Ophiopsidae, whereas 'F.' microlepidotes shows similarities with the Caturidae. The position of 'F.' latimanus remains to be determined. There are no indications of a monophyletic genus of Furo and the relationships of the Upper Jurassic furids with the Lower Jurassic species of Furo remain to be examined.
Keywords: Eugnathus, Furo, Halecomorphi, phylogeny, Plattenkalke, Tithonian
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Paulo M. Brito , David M. Martill & Sylvie Wenz, A semionotid fish from the Crato Formation (Aptian, Lower Cretaceous) of Brazil: palaeoecological implications. Oryctos 1, 37-42.
A partial example of an articulated fish cf. Araripelepidotes sp. from the Nova Olinda Member of the Crato Formation (Aptian, Lower Cretaceous, Araripe Basin, Brazil) is the first record of this taxon from this formation. Fishes other than Dastilbe spp. are extremely rare in the Crato Formation and we consider the implications in terms of the overall ichthyofauna diversity and palaeoecology.
Keywords: Pisces, Lower Cretaceous, Brazil
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Haiyan Tong, Pleurodiran turtles from the Eocene of Saint Papoul (Aude), Southern France. Oryctos 1, 43-53.
Pleurodiran turtle remains including a well-preserved skull and isolated plates from the Eocene Saint Papoul locality (Aude, southern France) are described in detail and referred to the family Podocnemididae. The skull belongs to a new genus and species, Papoulemys laurenti. Its phylogenetic relationships are discussed.
Keywords : Eocene, Southern France, Testudines, Pleurodira, Podocnemididae, Papoulemys laurenti, Phylogeny
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Eric W.A. Mulder, John W.M. Jagt, Marcel M.M. Kuypers, Hans H.G. Peeters & Peggy Rompen. Preliminary observations on the stratigraphic distribution of Late Cretaceous marine and terrestrial reptiles from the Maastrichtian type area (SE Netherlands, NE
Despite the fact that many Late Cretaceous marine fossils from the Maastrichtian type area, and reptiles in particular, have become famous worldwide, the stratigraphic ranges of most of the species represented are still poorly known. In recent years, much progress has been made on the litho- and biostratigraphic subdivision of Campanian and Maastrichtian strata in the area. This makes it possible to collect stratigraphically well-documented material from the various working and disused quarries and natural outcrops in that area. In turn, these collections enable the ranges of the various taxa to be determined much more precisely. Naturally, collections made in the nineteenth century often suffer from lack of stratigraphic data. This is especially unfortunate since they comprise many type specimens. To make matters worse, specimens have often been completely freed from the matrix, making modern analyses of foraminiferal and/or bioclast contents impossible. The present paper summarises current knowledge of the stratigraphic distribution of marine as well as terrestrial reptiles known from the type area of the Maastrichtian Stage. This picture will undoubtedly be refined as field work continues; projects under way include an analysis of the distribution of possible prey items of mosasaur taxa and the description of juvenile turtles and mosasaurs.
Keywords: Reptiles, Late Cretaceous, Belgium, the Netherlands, stratigraphy.
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Denis Vasse & Stéphane Hua, Diversité des crocodiliens du Crétacé supérieur et du Paléogène. Influences et limites de la crise Maastrichtien-Paléocène et des "Terminal Eocene Events". Oryctos 1, 65-77.
L'étude de la diversité des crocodiliens au cours du Crétacé supérieur et du Paléogène permet de suivre la manière dont ce groupe a réagi à la crise K/T et aux "Terminal Eocene Events". Il est nécessaire de ne pas traiter les crocodiliens comme une entité homogène d'un point de vue taxinomique et écologique : la distinction de quatre modes de vie met en évidence l'importance du remplacement des anciennes lignées crocodiliennes (mésosuchiens) par les modernes (eusuchiens) et relativise l'influence de la crise Crétacé-Paléocène. L'étude de diversité générale, par types écologiques, ainsi que les taux d'extinctions et d'apparitions montrent que les changements survenant parmi les crocodiliens sont progressifs et non nécessairement synchrones avec les crises. Les variations assimilables à la limite K/T peuvent être en partie expliquées indépendamment de cette crise. Les limites climatiques indiquées par les crocodiliens correspondent bien aux changements de l'Eocène supérieur et définissent un cadre pour la crise K/T. Cela rappelle que l'étude des groupes ayant bien franchi une crise peut apporter des éléments pour mieux la définir, préambule nécessaire à son explication.
Mots Clés : Crocodylia, Diversité, Crises, Crétacé, Paléogène
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David M. Martill & Eberhard Frey, A new pterosaur Lagerstätte in N. E. Brazil (Crato Formation; Aptian, Lower Cretaceous) : preliminary observations. Oryctos 1, 79-85.
Although pterosaurs are rare in the Nova Olinda Member of the Crato Formation (Aptian, Lower Cretaceous, Araripe Basin, N.E. Brazil), their remains have been recovered in increasing numbers over the last five years from the numerous stone pits between Nova Olinda and Santana do Cariri. Several distinct forms are known including tapejarids, a possible ornithocheirid and a possible azdharchid. Some specimens exhibit soft tissue preservation and structures previously unknown in related pterosaurs from other sites have been revealed. Preservational styles are variable in that some specimens are articulated, but examples also occur as partially articulated remains; associated, but disarticulated elements and as isolated bones.
Keywords: Pterosaur, Lower Cretaceous, Brazil, Lagerstätte
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Zoltan Csiki & Dan Grigorescu, Small Theropods from the Late Cretaceous of the Hateg Basin (Western Romania) - an unexpected diversity at the top of the food chain. Oryctos 1, 87-104.
The Late Maastrichtian deposits of the Hateg Basin have yielded numerous remains of herbivorous dinosaurs (titanosaurids, ornithopods, nodosaurids); but those of theropods are scarce, represented mostly by teeth and hindlimb elements. New material allows the recognition of an unexpected diversity of these predators in the Hateg fauna. Teeth of various morphologies are reported here to represent several distinct taxa of small theropods: a velociraptorine dromaeosaurid, a "troodontid-like" small theropod, cf. Euronychodon and perhaps a fourth, peculiar small theropod with sharp, but unserrated carinae on the teeth. Re-examination of previously published theropod material also suggests such diversity. Femora, previously referred to Elopteryx, probably belong to a derived maniraptoran. A distal end of a femur seems to document a small ceratosaur, while some tibiotarsi (holotypes of Bradycneme and Heptasteornis) may represent a non-maniraptoran tetanuran theropod. Without diagnostic remains of small theropods, it is inappropriate to give the reported material generic names; consequently informal use of the published names 'Elopteryx' and 'Bradycneme' is recommended. Moreover, for most part of the isolated theropod remains from Hateg there are no reasons to group them under the same name; one such case may be represented, however, by some skull elements and the velociraptorine teeth. The diversity of the small theropods in the Hateg fauna, together with the absence of a large "top" theropod, represents the first such case reported for Late Cretaceous faunas. This phenomenon is probably linked to the restricted, insular habitat of the Hateg fauna, which could not accommodate and support any larger sized predator.
Keywords : Hateg Basin, Late Maastrichtian, ceratosaurs, maniraptorans, dromaeosaurids, Euronychodon, diversity, insular habitat.
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Jean Le Loeuff & Eric Buffetaut, A new dromaeosaurid theropod from the Upper Cretaceous of Southern France. Oryctos 1, 105-112.
New dromaeosaurid remains from the Upper Cretaceous of southern France (Var Department, Fox-Amphoux syncline) include vertebrae and a right humerus. This material belongs to a new genus and species of dromaeosaurid, described as Variraptor mechinorum. Among its derived features are double pleurocoels on the cervico-dorsal vertebrae and a strong medial tubercle on the humerus. Variraptor mechinorum is interpreted as a representative of an isolated European lineage of dromaeosaurids which evolved from an Early Cretaceous Euramerican ancestral stock.
Keywords : Theropoda, Dromaeosauridae, Variraptor, Late Cretaceous, France
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John Martin, Valérie Martin-Rolland & Eberhard Frey, Not cranes or masts but beams. The biomechanics of sauropod necks. Oryctos 1, 113-120.
The mechanics of sauropod necks are still poorly understood, judging from many recent life reconstructions. Only seven or eight sauropod taxa have necks well-enough known for their mobility and posture to be reconstructed fully and reliably. In these animals, the limits of mobility imposed by the zygapophyseal and central articulation structures may be calculated. Simple biomechanics shows that sauropod necks were segmented beams, and that the way in which segmented beams must be braced adds further limits to mobility. The bracing systems implied by the vertebral anatomy can be reconstructed, based partly on an appreciation, from extant animals, of what soft-tissue structures were possible given a particular set of bone geometries. Sauropod necks were dorsally-braced, ventrally-braced or a combination of the two: each system was associated with a distinctive, exclusive, group of vertebral features - high, low or divided neural spines, large or small transverse processes and short or elongated cervical ribs. The two sets of mobility-controlling systems (joint morphology and bracing) made the necks of all "popular" sauropods relatively, or very, rigid structures, and also show that they were habitually carried with the ventral aspect "down" with respect to gravity - in other words as beams, not masts.
Keywords : Dinosaur, sauropod, biomechanics, necks, life reconstructions.
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Julio Company, Angel Galobart & Rodrigo Gaete. First data on the hadrosaurid dinosaurs from the Upper Cretaceous of Valencia, Spain. Oryctos 1, 121-126.
Recently, remains of dinosaurs assigned to the family Hadrosauridae have been recovered from the Upper Cretaceous locality of La Solana, Spain. The material presented here consists of a lower jaw and several fragmentary isolated teeth. Diagnostic features of bones place the hadrosaurs from Spain closer to the hadrosaurid dinosaurs from southern France than to Telmatosaurus transsylvanicus from the Maastrichtian of Romania.
Keywords.- Upper Cretaceous, hadrosauridae, dentary, La Solana locality, Spain.
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Mette Elstrup Rasmussen, Notes on the morphology and the orientation of the forelimb of Ouranosaurus nigeriensis. Oryctos 1, 127-130.
The forelimb of O. nigeriensis was closely examined. In the wrist, the intermedium is fused to the radiale and not, as previously thought, to the ulnare. The morphology of the forelimb, and particularly that of the radius and ulna, has implications regarding the orientation of the manus. In the articulated forelimb, the palm of the manus would have faced nearly medially, not posteriorly, as it has often been portrayed. The medial orientation is even more pronounced in the forelimb of other iguanodontids.
Keywords: Dinosauria, Ouranosaurus, carpus, manus
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Eric Buffetaut, First evidence of enantiornithine birds from the Upper Cretaceous of Europe : postcranial bones from Cruzy (Hérault, southern France). Oryctos 1, 127-130.
A coracoid and an incomplete femur from a newly discovered Late Campanian to Early Maastrichtian locality at Cruzy (Hérault, France) are described and identified as the first remains of enantiornithine birds to be reported from the Upper Cretaceous of Europe. This find extends to Europe the already wide known geographical distribution of Late Cretaceous Enantiornithes, and confirms the important part played by this peculiar group of birds in avifaunas in many parts of the world until late in the Cretaceous.
Keywords : Aves, Enantiornithes, Late Cretaceous, France.
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Paulette Pauc & Eric Buffetaut, Reproduction de perles circulaires en coquille d'oeufs de dinosaures. Oryctos 1, 137-146.
Nous décrivons ici le processus de la reproduction des perles circulaires en coquilles d'oeufs de dinosaures, tout comme devaient probablement les réaliser les artisans protohistoriques du Désert de Gobi en Mongolie.
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