Oryctos
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Accès privé :
| volume 4, 2002 |
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Dorin Sorin Baciu & Bruno Chanet, Fossil flatfishes (Teleostei: Pleuronectiformes) from the Oligocene of Piatra Neamt (Romania). Oryctos 4, 17-38.
The aims of this paper are: I) to report the presence of fossil pleuronectiformes in the Middle Oligocene of Piatra Neamt (Romania), ii) to specify their systematic position, iii) to present data they can bring about the phylogeny of flatfishes. Two species have been recognised: Scophtalmus stamatini (Paucã, 1931) and Oligobothus pristinus n. g. n. sp. The present study provides new arguments to assess that the first species is the oldest known scophthalmid and then the first record of a fossil member of this flatfish family. As the latter possesses myorhabdoi, some peculiar intermuscular bones only present in bothids, Oligobothus pristinus n. g. n. sp. is the oldest known member of the family Bothidae. These results suggest that the dichotomies between the Bothidae, the Scophthalmidae and the remaining Pleuronectiformes occurred before Middle Oligocene.
Keywords: Teleosteans, Pleuronectiformes, Bothidae, Scophthalmidae, Oligocene, Piatra Neamt, Romania
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Eric Buffetaut & Varavudh Suteethorn, Remarks on Psittacosaurus sattayaraki Buffetaut & Suteethorn, 1992, a ceratopsian dinosaur from the Lower Cretaceous of Thailand. Oryctos 4, 71-73.
The validity of Psittacosaurus sattayaraki, from the Early Cretaceous of Thailand, has recently been questioned by Sereno, who claims that the material is poorly preserved and can only be referred to as “Ceratopsia incertae sedis”. We correct several inaccuracies in Sereno’s discussion, and reassert that the Thai material warrants identification as a distinct species of the genus Psittacosaurus.
Keywords : Psittacosaurus, Early Cretaceous, Thailand, preservation, identification
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Gerald Mayr, A postcranial skeleton of Palaeopsittacus Harrison, 1982 (Aves incertae sedis) from the Middle Eocene of Messel (Germany). Oryctos 4, 75-82.
A nearly complete postcranial skeleton of Palaeopsittacus cf. georgei Harrison, 1982 (Aves incertae sedis) is described from the Middle Eocene of Messel, Germany. This is the first articulated skeleton assigned to Palaeopsittacus, which before was only known from few isolated bones from the Lower Eocene of England. Further, the new specimen is the first record of Palaeopsittacus outside the type locality Walton-on-the-Naze. Palaeopsittacus is not closely related to the Psittaciformes (parrots) to which it was originally assigned, though its true systematic affinities remain uncertain. In the morphology of the tarsometatarsus, the Eocene genus resembles Recent Podargidae (Caprimulgiformes). An isolated skull from Messel is figured which might also belong to Palaeopsittacus.
Keywords: fossil birds, Middle Eocene, Messel, Paleopsittacus georgei, new specimen
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Kathrin Dietze, Heterochrony within Amblypterydae (Actinopterygii; Permo-Carboniferous)? Oryctos 4, 3-15.
Certain morphological traits of the Amblypteridae, i.e. Amblypterus and Paramblypterus, suggest local heterochromic processes by paedomorphosis. Since data on the ontogenetic stages of an ancestral paramblypterid species are not available, Elonichthys palatinus, a fairly basal actinopterygian species, is used as a model for the potential ontogeny to polarize patterns of heterochrony in the Amblypteridae. Presumaly, ornamentation and shape of the skull, squamation, and growth of the opercular series of Paramblypterus and/or Amblypterus were affected by processes related to heterochrony.
Keywords: lower actinopterygians, Permo-carboniferous, heterochrony, paedomorphosis, skull, squamation, opercular series
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Marie Pincemaille-Quillevéré, Description of a partial skeleton of Rhabdodon priscus (Euornithopoda) from the Upper Cretaceous of Vitrolles (Bouches du Rhône, France). Oryctos 4, 39-70.
An incomplete partially articulated skeleton of the ornithopod dinosaur Rhabdodon priscus Matheron, 1869, has been discovered in the lower Maastrichtian of Vitrolles (Bouches du Rhône, France). The description of its remains allows us to clarify the diagnosis of Rhabdodon priscus. This study also provides discussion on the systematic placement of Rhabdodon priscus within the Euornithopoda. Numerous anatomical characters suggest that it is closely related to Tenontosaurus tilletti, a Lower Cretaceous basal iguanodontian from North America.
Keywords: Dinosauria, Ornithischia, Ornithopoda, Euornithopoda, Rhabdodon
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Peter J. Adam & Annalisa Berta, Evolution of Prey Capture Strategies and Diet in Pinnipedimorpha (Mammalia, Carnivora). Oryctos 4, 83-107
Pinnipeds represent a lineage of terrestrial carnivores that have secondarily adapted to a marine existence and must capture and process prey under water. We examined known diets and skull morphologies associated with different prey capture strategies in extant and fossil pinnipedimorphs using a phylogenetic context to reveal their evolutionary feeding history and diversity. Unlike their arctoid ancestors, no extant pinnipedimorph masticates food. Prey capture is accomplished by four methods, characterized by numerous craniodental features (in parentheses): 1) pierce feeding (homodonty; M1 anterior to dentary midlength; enlarged orbit); 2) suction feeding (elongate and vaulted palate; robust pterygoid hamuli; mandibular fusion); 3) filter feeding (high-crowned, intricately cusped postcanine teeth; upper and lower teeth interdigitating; post-dental ridges); and 4) grip and tear feeding (straight, sharply pointed postcanine cusps; enlarged incisors). Pierce feeding is typical of most pinnipedimorphs, while filter feeding is limited to extant crabeater seals and grip and tear feeding to living leopard seals. A tendency toward suction feeding occurs in at least four independent lineages (otariine sea lions, bearded seal, and dusignathine and odobenine walruses), although it is best developed in odobenines. Only a weak correlation between functional anatomy and diet was observed for extant taxa. For example, suction feeding is utilized by walruses to capture and consume benthic mollusks, but skulls with convergent evolution of suction associated characters are also well designed for capturing larger fish and squid (e.g. Otaria byronia).
Keywords : Pinnipedia, Phocidae, Otariidae, Odobenidae, Evolution, Adaptation, Feeding, Diet, Morphology, Skull
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