First Jurassic dinosaur tracksite from Guizhou Province,China: morphology,trackmaker and paleoecology

Abstract

Sauropod tracks from the Early Jurassic Maanshan Member of the Ziliujing Formation in the Dazhuanwan area of Guizhou represent the first Jurassic dinosaur track record for this province. The best preserved and longest trackway is narrow gauge (Brontopodus type), and indicates a relatively small trackmaker (footprint length ~35.0 cm). In conjunction with sauropodomorph skeletal remains these tracks suggest that basal sauropodomorphs and primitive sauropods coexisted in this region during the Early Jurassic. This pattern is same in the Lufeng and Sichuan basins. Thus, sauropod tracks from southwest China are diverse in the Early Jurassic, and include narrow gauge Parabrontopodus, wide gauge Brontopodus-type, and basal sauropodomorph tracks.     

A reappraisal of azhdarchid pterosaur functional morphology and paleoecology

Azhdarchid pterosaurs were among the most widespread and successful of pterosaur clades, but their paleoecology remains controversial. Morphological features common to all azhdarchids include a long, shallow rostrum; elongate, cylindrical cervical vertebrae that formed a long and unusually inflexible neck; and proportionally short wings with an abbreviated fourth phalanx. While azhdarchids have been imagined as vulture-like scavengers, sediment probers, swimmers, waders, aerial predators, or stork-like generalists, most recent authors have regarded them as skim-feeders, trawling their lower jaws through water during flight and seizing aquatic prey from the water's surface. Although apparently widely accepted, the skim-feeding model lacks critical support from anatomy and functional morphology. Azhdarchids lack the many cranial specialisations exhibited by extant skim-feeding birds, most notably the laterally compressed lower jaw and shock absorbing apparatus required for this feeding style. Well-preserved azhdarchid skulls are rare, but their rostra and lower jaws appear to have been sub-triangular in cross-section, and thus dissimilar to those of skim-feeders and sediment probers. Taphonomic data indicates that azhdarchids predominately inhabited inland settings, and azhdarchid morphology indicates that they were poorly suited for all proposed lifestyles bar wading and terrestrial foraging. However, azhdarchid footprints show that their feet were relatively small, padded and slender, and thus not well suited for wading. We argue that azhdarchids were stork- or ground hornbill-like generalists, foraging in diverse environments for small animals and carrion. Proficient terrestrial abilities and a relatively inflexible neck are in agreement with this interpretation.     

Ordovician receptaculitids from California and their significance

Well preserved receptaculitids from the Middle Ordovician in the Grapevine Mountains of Eastern California have been collected and studied. These highly variable specimens are regarded as intrapopulational variants of one species. This variation is due to differences in the microenvironment and to the occurrence of individuals at various stages of growth. These specimens are assigned to Ischadites mammillaris (Walcott 1884).This species differs from the similar species of Ischadites and Receptaculites in the following features: (1) small, numerous outer plates; (2) interlocking rays between the elements; and (3) curved and bifurcated inner shafts. Ischadites mammillaris is described and its morphology is compared to that of sponges and dasycladacean algae. Recent algal interpretations that regard the closed extremity of the receptaculitid as the growing end are believed to be incorrect. It is concluded that Ischadites mammillaris as well as other similar receptaculitids should retain their tentative alignment with the Porifera.     

Orbital variations, climate and paleoecology

One of the most exciting discoveries in the earth sciences in recent decades has been the proof that ice ages are governed by deterministic variations in the earth's orbit. These variations modify the latitudinal and seasonal distribution of solar radiation at periods ranging from 103 to 10(5) years, and alternately produce conditions for building and melting continental ice. The same solar radiation variations also govern other aspects of world climate, including the temperatures of the midlatitude continental interiors, the intensity of upwelling in the tropical oceans, and the strength and extent of the monsoons. The interplay of solar radiation, seasonality and ice-sheet changes is responsible for the complex ecological history documented in the fossil record of the past 20 000 years. But the orbital variations have occurred throughout earth's history, and have caused periodic environmental changes in both terrestrial and marine environments even during times when there was no ice. Species have responded to these changes by range migration, an evolved ability that may maintain their genetic coherence in the face of a continually changing environment.     

Population paleoecology and comparative taphonomy of two edrioasteroid (echinodermata) pavements: Upper ordovician of kentucky and Ohio

Two strophomenid brachiopod shell pavements bearing abundant edrioasteroid epizoans occur stratigraphically within the top 4.5 m of the Corryville Formation (Upper Ordovician, Maysvillian) in Boone County, Kentucky, and Hamilton County, Ohio. Both assemblages are dominated by Isorophus cincinnatiensis and contain Carneyella pilea and Streptaster vorticellatus as lesser constituents. Pedicle exterior valves of Rafinesquina “alternata”; are the preferred substratum for all species at both sites, but the Kentucky population occurs mainly on unabraded, articulated shells and the Ohio population occupies abraded, disarticulated shells. The Kentucky population includes a greater size range of Isorophus (at least three cohorts) than the Ohio population (at least two cohorts), suggesting a greater time span of colonization for the Kentucky site. Host shells from Kentucky have anterior‐posterior axes strongly aligned NE‐SW whereas the Ohio shells are unoriented. Isorophus in Kentucky show a preference for the anterior margin of the Rafinesquina pedicle exterior valve, whereas Isorophus in Ohio show no preferred location on host shells. The Kentucky edrioasteroids are inferred to have attached to mainly live Rafinesquina in brachial‐valve‐up position. Host shells were inverted and oriented by a NE‐SW storm surge, then buried rapidly. Ohio edrioasteroids occupied mainly dead, already inverted host shells not oriented by storm surge possibly because of their more downslope (distal) location. Comparative taphonomic relationships between the two coeval populations are consistent with a model of proximal to distal distribution along a gentle shallow subtidal N‐S paleoslope subject to episodic storm activity.     

Vertebrate paleoecology: A current perspective

Vertebrate paleoecology, a study with a long history, has thrived during the last four decades and has become the focal point of intensive investigation since about 1965. It has followed a somewhat different course from studies of marine invertebrate paleoecology questions about the utility, validity and relationships of paleoecology to ecology continue to be raised and discussed.Paleoecology draws on and contributes to essentially all areas of paleontology. Several subdisciplines in which there has been particularly intensive investigation are singled out for discussion. Taphonomy lies at the base of all paleoecological studies for, along with systematic analysis, it provides the basic data upon which all reconstructions of the living biota are made from the fossil deposits to which they contributed. Very active in development of taphonomy have been the students of Paleoecology of the Hominidae. This area of study has passed from a dominance of speculation in the first decades of this century to objective analysis based upon the application of biological principles, extended and detailed field work, and current evolutionary concepts to the evolution of the family Hominidae.Extinctions have recently received extensive analyses, with emphasis on mass extinctions such as that at the Cretaceous-Tertiary boundary. The analyses have extended the uses of taphonomic research into the difficult areas of time intervals generally not available in the fossil record. Physiological-Ecological and Behavioral studies are casting new light upon the problems of interpretation of extinct animals which lack close living counterparts. Community Structure has been of special interest among terrestrial vertebrates since the early 1950's. It's study has required reinterpretations of samples and sampling procedures and development of models to aid in analysis of the biases in fossil assemblages. Both community types and substantive communities have received careful attention, including pragmatic definitions, studies of the use of analogies and introspection on possible contributions to ecology as whole. Such researches have been elaborated into studies of the relationships communities through time under the general heading of Community Evolution. Problems of evolution in a slowly changing community and in the evolution of new community types have been central themes in this area.     

Equilibrium theory and paleoecology

Although several paleontologists have recently attempted to apply MacArthur & Wilson's equilibrium theory to the fossil record, their efforts have not met with overwhelming success. The major difficulties have involved the use of questionable methodologies and the application of a fundamentally inappropriate theoretical base. In the first category it appears as if previous methods of data collection and their subsequent analyses must be critically reviewed in order to adequately test the equilibrium theory. Thus detailed species lists that include population numbers must be compiled for spatially restricted habitats. Sampling of local stratigraphic sections must be carried out on a centimeter by centimeter basis rather than at meter intervals. It appears most likely that the use of colonization curves, coupled with a determination of species saturation levels, will provide a rigorous, quantitative technique for the analysis of equilibrium states. It has become obvious over the past ten years that paleoecologists need to be more critical in their application of ecological theories to the fossil record and in substantiation of this claim, and contrary to earlier reports, it seems as if a valid test of the equilibrium theory in the fossil record has yet to be made.     

Oligocene vertebrate assemblages in central Kazakhstan: Faunas,biogeography and paleoecology

The history of research in Oligocene paleozoology of Central Kazakhstan is described. Continental Oligocene strata may be recognized on the basis of different Oligocene fossil vertebrates, taking into account the stratigraphic occurrence of mammal genera and species, their belonging to subdivisions of the General Stratigraphic Scale as well as statistical determination of assemblage formation time. At least two stratigraphic levels occur in this region. These are: Saryin (Myneskesuyek, Mogila Saty localities), the lower part of Chelkarnura (Shintuzsay) Svitas (upper half of the Lower Oligocene—Upper Oligocene); and the upper part of Chelkarnura (Chelkar‐Teniz) and Betpakdala (Kyzyl‐Kak) Svitas (Upper Oligocene). Apparently the Chelkar‐Teniz vertebrate assemblage originated in several stages. They require future studies of stratigraphic position of fossils.

Origin and ways of migration of mammalian genera from the Oligocene faunistic assemblages of Central Kazakhstan are discussed.

A preliminary paleoecological study suggests that animals of open and rarefied landscapes dominated in the Myneskesuyek region, the faunistic assemblage of which appears to have been the most ancient. Vertebrate inhabitants of partly open and open, as well as forest habitats probably were present in Chelkar‐Teniz. Animals primarily of forest and scattered woodland dwellers predominated in the Kyzyl‐Kak locality.     

Cenomanian-Turonian rudists from Western Sinai, Egypt: Systematic paleontology and paleoecology

The Cenomanian-Turonian sequence is well exposed in western central Sinai and contains a considerable number of rudist species. The identified rudists belong to Radiolitidae, Hippuritidae and Requieniidae. Fifteen species are described, belonging to ten genera: Requienia, Toucasia, Apricardia, Radiolites, Eoradiolites, Praeradiolites, Sphaerulites, Sauvagesia, Hippurites, and Vaccinites. Eleven species are reported in the Cenomanian and four species in the Turonian. Within the Cenomanian, two new species are described: Requienia tortuosi and Eoradiolites lenisexternus. The genus Requienia and the species Apricardia carentonenis d’Orbigny, Eoradiolites syriacus (Conrad), Sphaerulites agariciformis Delamétherie, Sphaerulites depressus Blanckenhorn and Vaccinites cf. grossouvrei (Douvillé) are reported for the first time from Egypt. The Cenomanian and Turonian rudists in the western Sinai show either elevator or clinger morphotypes, with the predominance of the former type; recumbent mode of life is rarely represented by some Requieniidae. The elevators are of isolated and clustered occurrences and more represented in the Cenomanian sequence. Rudists of the study area are mainly of parautochthonous fabrics with low to dense packing. Autochthonous fabrics are also achieved by some species, mainly in the Turonian. The disappearance of rudists from the middle part of the sequence and above the Cenomanian/Turonian boundary is due to a deeper setting that resulted from sea-level rise or seafloor subsidence (shelf drowning). The occurrence of rudists with oysters and other benthic fossils in the siliciclastic and carbonate sediments of the Cenomanian and Turonian sedimentary rocks in the Sinai indicate that the sequence was deposited on a broad, shallow shelf. Although the first marine transgression invaded the central Sinai in the late Cenomanian, transgressive deepening conditions continued until the Turonian. The rudists of central Sinai are of Tethyan affinity with significant relation with North Africa, the Middle East, and Southern Europe.     

Larval cement gland of frogs: comparative development and morphology

The cement gland (CG) is a transient mucus-secreting organ, found in most anuran embryos and early larvae and located normally on the anteroventral side of the head. Its sticky secretion allows newly hatched larvae to attach to the egg jelly or to another support and remain hidden and stationary until feeding starts. Analysis of CG morphology in 20 anuran species from six families using scanning electron microscopy revealed five distinct patterns of development, which partly related to families. The five patterns are described, as well as additional details such as CG surface ciliation and asymmetry. Three species lacked a CG. This was expected in two cases, a late-hatching phyllomedusine hylid and a direct-developing eleutherodactylid, but not in the foam-nesting Leptodactylus fuscus, which hatches at the same stage as many species that develop a CG. Lack of the CG in L. fuscus suggests that its posthatching period in the foam nest may be obligate. In both L. fuscus and the phyllomedusine hylid, there remain morphological traces of CG development.     

Molecules and morphology: comparative developmental genetics of the Brassicaceae

For approximately 20 years Arabidopsis has been a model system to investigate developmental and physiological questions in plant biology, leading to the identification of genes and genetic systems involved in many processes. Extending ideas arising from knowledge of developmental genetic systems in Arabidopsis to other species of the Brassicaceae will require the application of genomics technologies developed in Arabidopsis and the establishment of additional genetic systems and resources in other species. Morphological variation in all plant organs, as well as in growth habit, mating systems, and physiology are represented in the breadth of Brassicaceae species offering ample opportunity to investigate the molecular basis of morphological evolution in this family. In addition, the frequent recent hybridization events in Brassica and Arabidopsis facilitate study of this pervasive force in the evolution of all plants.     

Polymorphism and vestigiality: comparative anatomy and morphology of bryozoan avicularia

Avicularia are polymorphic zooids characteristic of cheilostome bryozoans. Avicularia are assumed to have a defensive role yet ascertaining the presence of sensory structures to support this theory has been overlooked. We examine palatal morphology of the avicularia from five species of cheilostome bryozoans and compare the ultrastructural anatomy of the avicularia from two bugulid species from different habitats. SEM analysis revealed an array of palatal morphologies. Small tufts of cilia emerge from the orifice in the palate of the avicularia of Tricellaria catalinensis, Arachnopusia unicornis and Catenicella pseudoelegans. A ciliated vestigial polypide emerges from the orifice in the palate of Rhynchozoon zealandicum and comprises eleven papillae, or vestigial tentacles, seven of which are covered in microvilli. The vestigial polypide of the bird’s head avicularium of the cosmopolitan Bugula flabellata consists of a mass of ciliated and unciliated cells containing numerous granular vesicles. The avicularium of B. flabellata is capable of detecting tactile stimulation by virtue of the tuft of sensory cilia and is proactive in the capture of invertebrate epibionts. In contrast, in the deep-sea Nordgaardia cornucopioides, the vestigial polypide consists of a ciliated vestigial tentacle encased by glandular secretory cells. Avicularia possess structures derived from a feeding autozooid, and we show how the homologous structures have evolved and suggest that avicularia have been modified to carry out a variety of specific functions.     

The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass

Martinez, J.-N. & Sudre, 1. 1995 11 30 The astragalus of Paleogene artiodactyls: comparative morphology, variability and prediction of body mass. Lethaia , Vol. 28, pp. 197–209. Oslo. ISSN 0024–1164.
The morphology of the astragalus is analysed in nineteen Paleogene artiodactyls (suborders Palaeodonta, Suina, Ancodonta and Ruminantia). This morphology is related to the functional adaptations of the appendicular skeleton, but some diagnostic characters can be seen at the family level. For the populations examined, the proportions of this bone show a low intraspecific variability, which does not allow detection of any dimorphism. An allometric relationship between the dimensions of the astragalus and the body mass has been established for extant species, allowing estimates for the fossil species. In most cases, the interval between the two extreme estimations using the astragalus includes the estimated body mass using M/1 area. The limits of this method are discussed, and it is suggested that the dimensions of the astragalus give a better estimation of the body mass than the dental area. □ Artiodactyls, astragalus, comparative morphology, body mass, allometry, Paleogene .     

Laryngotracheal morphology of Afro-Madagascan geckos: a comparative survey

The structural variation of the gekkonid larynx and trachea is examined within a representative subset of 17 species of Afro-Madagascan gekkonines to determine if there are underlying morphological correlates of vocalization. The documented morphology is compared to that of the tokay (Gekko gecko), which has previously been described. Data were obtained from gross anatomical observations, scanning electron microscopy, histological examinations and computer-generated, three-dimensional, skeletal reconstructions. Although there is limited variation among most Afro-Malagasy gekkonids, the larynges of Ptenopus garrulus and Uroplatus fimbriatus exhibit marked degrees of differentiation, suggesting that laryngeal and tracheal morphology may account for the documented vocal variability of gekkonid lizards. Cladistic analyses indicated that parallel adaptive trends characterize the laryngeal morphology of the examined taxa. Alternate designs and refinements to a model of gekkonid phonation are presented, and the evolution of acoustic communication in the Gekkonidae is considered.