All-Terrain Cyclocopter Capable of Aerial, Terrestrial, and Aquatic Modes

This paper describes the design and experimental validation of an all-terrain cyclocopter micro air vehicle capable of power-efficient aerial, terrestrial, and aquatic locomotion with seamless transition between the modes. The vehicle has a mass of 1010 g and solely relies on its four cycloidal rotors (cyclorotors) to achieve all modes of locomotion. The cyclorotor rotational speeds and thrust vectors are individually modulated to sustain stable hover in aerial mode. A similar control strategy using aerodynamic forces generated by cyclorotors is also implemented for aquatic locomotion. The wheels are efficiently integrated into the carbon fiber rotor endplates since cyclorotors rotate about the horizontal axis. As a result, the cyclocopter maneuvers in terrestrial mode by directly relying on motor torque. Seamless transition is accomplished using a retractable landing gear system equipped with polystyrene foam pontoons. In aerial mode, the cyclorotors operate at 1550 rpm and consume 232 W to sustain hover. Forward translation at 2 m/s in terrestrial mode requires 28 W, which is a 88% reduction from hover. In aquatic mode, the cyclorotors operate at 348 rpm and consume 19 W, which is a 92% reduction from hover. Overall, a versatile platform capable of multimodal operation is successfully demonstrated with only a modest addition in total mass.

A buoyancy, balance and stability challenge to the hypothesis of a semi-aquaticSpinosaurusStromer, 1915 (Dinosauria: Theropoda)

A recent interpretation of the fossil remains of the enigmatic, large predatory dinosaurSpinosaurus aegyptiacusStromer 1915 proposed that it was specially adapted for a semi-aquatic mode of life—a first for any predatory dinosaur. To test some aspects of this suggestion, a three-dimensional, digital model of the animal that incorporates regional density variations, lungs and air sacs was generated, and the flotation potential of the model was investigated using specially written software. It was found thatSpinosauruswould have been able to float with its head clear of the water surface, although it was laterally unstable and would tend to roll onto its side. Similarly detailed models of another spinosauridBaryonyx(Suchomimus)tenerensisSereno et al. 1998, along with models of the more distantly relatedTyrannosaurus rexOsborn 1905,Allosaurus fragilisMarsh 1877,Struthiomimus altusLambe 1902, andCoelophysis bauriCope 1887 were also able to float in positions that enabled the animals to breathe freely, showing that there is nothing exceptional about a floatingSpinosaurus. Validation of the modelling methods was done with floated models of an alligator and an emperor penguin. The software also showed that the center of mass ofSpinosauruswas much closer to the hips than previously estimated, similar to that observed in other theropods, implying that this dinosaur would still have been a competent walker on land. With its pneumatised skeleton and a system of air sacs (modelled after birds), theSpinosaurusmodel was found to be unsinkable, even with its lungs deflated by 75%, and this would greatly hinder a semi-aquatic, pursuit predator. The conclusion is thatSpinosaurusmay have been specialized for a shoreline or shallow water mode of life, but would still have been a competent terrestrial animal.

An enigmatic aquatic snake from the Cenomanian of Northern South America

We report the first record of a snake from the Cretaceous of northern South America. The remains come from the La Luna Formation (La Aguada Member, Cenomanian of Venezuela) and consist of several vertebrae, which belong to the precloacal region of the vertebral column. Comparisons to extant and extinct snakes show that the remains represent a new taxon,Lunaophis aquaticusgen. et sp nov. An aquatic mode of life is supported by the ventral position of the ribs, indicating a laterally compressed body. The systematic relationships of this new taxon are difficult to determine due to the scarcity of fossil material; it is, however, a representative of an early lineage of snakes that exploited tropical marine pelagic environments, as reflected by the depositional conditions of the La Aguada Member.Lunaophisis also the first aquatic snake from the Cenomanian found outside of the African and European Tethyan and Boreal Zones.

Blood Cell Profiles of the Tadpoles of the Dubois's Tree Frog,Polypedates teraiensisDubois, 1986 (Anura: Rhacophoridae)

The present paper describes a sequential study of the leukocyte profiles and the changes in morphometry and morphology of erythrocytes in the tadpoles ofPolypedates teraiensisduring their development and metamorphosis, that is, transfer from an aquatic mode to a terrestrial mode of life. Blood smears of 21 different stages (Gosner stage 26 to 46) of tadpoles were investigated. Population of erythrocytes was heterogeneous in population represented by various forms (oval, elliptical or rounded cells, comma shaped, teardrop shaped, schistocytes, senile erythrocytes, crenulated RBCs). Correlation between various morphometric values of erythrocytes was determined with different developing stages of tadpoles. Amongst the leucocytes, the lymphocytes were the most abundant cells followed by neutrophils. Neutrophils and monocytes showed varied morphologic forms. The percentage of lymphocytes and neutrophils showed a negative whereas percentage of eosinophil, basophil, and monocytes showed a positive correlation with the developmental stages of tadpoles. Blood platelets were also observed, which were rounded in shape and found in aggregates.

A review of Pachyvaranus crassispondylus Arambourg, 1952, a pachyostotic marine squamate from the latest Cretaceous phosphates of Morocco and Syria

The discovery of new specimens of Pachyvaranus crassispondylus Arambourg, 1952 from the Maastrichtian phosphates of Morocco and Syria enables us to (1) redescribe in detail this poorly known varanoid lizard, (2) provide a more detailed diagnosis and (3) re-evaluate the systematic affinities of this taxon within squamates. The latter is placed in Pachyvaranidae nov., considered a new unranked clade of non-pythonomorph Varanoidea. The intense pachyosteosclerosis observed in the vertebrae and ribs suggests a primarily aquatic mode of life for Pachyvaranus. This is in accordance with the sedimentological context (shallow marine environment). As for its palaeobiogeographical distribution, Pachyvaranus is a component of the marine reptile assemblages from the southern margin of the Mediterranean Tethys, around palaeolatitudes 20° N. The osteoderms previously referred to this taxon by Arambourg are reanalysed and assigned to a teleost fish.

Breeding activity patterns, reproductive modes, and habitat use by anurans (Amphibia) in a seasonal environment in the Pantanal, Brazil

Annual patterns of breeding activity, reproductive modes, and habitat use are described for a frog community in a seasonal environment, in the southern Pantanal, Mato Grosso do Sul, Brazil. Data were collected monthly between January 1995 and December 1998. A total of 24 species from four families; Bufonidae (3 species), Hylidae (10 species), Leptodactylidae (9 species), and Microhylidae (2 species) were registered. Three reproductive activity patterns are recognized among these species: continuous, explosive, and prolonged; 50% of the species were explosive breeders. Seasonal pattern of reproduction was verified for three analyzed years (1995-1997); most species reproduced during the rainy season (Nov-Jan). The reproduction was aseasonal in 1998; unexpected rains in the dry season lead to an unusual breeding activity. Five reproductive modes were noted — 62.5% of the species have the generalized aquatic mode, and 33.3% deposit eggs embedded in foam nests. Many species used the same sites for reproduction, although temporal partitioning and calling site segregation was observed. The occurrence of many species that exhibit explosive breeding early in the rainy season is common in seasonal and open environments with variable and unpredictable rainfall, as is the case in the Pantanal.

Extinction Patterns in the Herpetofauna of the Pleistocene of Britain and Europe

As we have seen in Chapter 4, many invalid European Pleistocene amphibian and reptile species were named on the basis of insufficient and inadequately described fossils (e.g., Estes, 1981, 1983; Rage, 1984c; Sanchiz, in press). Some of these forms have been synonymized with modern species, but others are in taxonomic limbo because of the international rules of zoological nomenclature. We now turn to a consideration of the few European Pleistocene fossil herpetological species that have been recognized as valid in recent years. These taxa fit into three catagories: (1) an extinct Pliocene anuran taxon that extended into the Pleistocene, (2) large Lacerta species that lived on oceanic islands, and (3) Pleistocene species that are probably morphological variants of living forms. All of the following taxa are addressed in Chapter 4. No extinct species of Pleistocene salamanders are currently recognized in Britain or Europe. The genus * Pliobatrachus from the Pliocene of eastern Europe extended into the Lower Pleistocene of Poland and the Middle Pleistocene of Germany in the form of * Pliobatrachus cf. Pliobatrachus langhae. The *Palaeobatrachidae, the only family in the history of the Anura that became totally extinct (Roček, 1995), represents the only extinct herpetological family known in the Pleistocene of Britain and Europe, and *Pliobalrachus represents the only extinct herpetologcal genus known in the Pleistocene of the region. Rocck (1995) suggested that the *Palaeobatrachidae did not survive the Pleistocene cooling because of their prevailingly aquatic mode of life, unlike, for instance, the Ranidac and Bufonidae that were able to withdraw from iceobliterated areas and return when climatic conditions improved. *Lacerta goliath is a Pleistocene or Holocene species that is known only from two localities in the Canary islands (see Chapters 4 and 5). It is twice the size of Lacerta lepida, the largest modern European Lacerta. *Lacerta maxima is another very large Pleistocene or Holocene Lacerta that is endemic to the Canary Islands. This species is known from a single fossil locality (see Chapters 4 and 5) and is differentiated from * Lacerta goliath on the basis of several trenchant osteological characters.

A new pachypleurosaur (Reptilia: Sauropterygia) from the Middle Triassic of Monte San Giorgio, Switzerland

Pachypleurosaur material from the Middle Triassic ‘ Grenzbitumen’-horizon (Anis-Ladin boundary) of Monte San Giorgio, Kanton Tessin, Switzerland, is described as a new genus and species, Serpianosaurus mirigiolensis .A detailed morphological description is followed by a quantitative analysis. The taxon differs from other pachypleurosaurids primarily by its relatively large skull and its straight lower jaw. Rib pachyostosis is absent. In most characters the taxon remains plesiomorphous with respect to other pachypleurosaurs from the Middle Triassic deposits of Monte San Giorgio, which accords well with its early stratigraphic occurrence at that locality. Sexual dimorphism is expressed by the size and shape of the humerus. A cladistic analysis shows the Pachypleurosauridae to constitute the sistergroup of all other Sauropterygia. The Sauropterygia and the Placodontia together form a monophyletic group, the Euryapsida, which is subordinated to the Diapsida and to the Neodiapsida, but which is classifed outside the archosauromorph-lepidosauromorph dichotomy within the Neodiapsida. A concluding paragraph discusses the status of the pachypleurosaurs within the Sauropterygia. Skull structure, and jaw mechanics in particular, suggest a relatively plesiomorph position of pachypleurosaurs within the Sauropterygia. Their adaptation to an aquatic mode of life was not carried to the degree observed in other sauropterygians, and the ability for rapid and deep dives seems to have been limited by middle-ear structure.