Morphology of the earliest reconstructable tetrapod Parmastega aelidae.

The known diversity of tetrapods of the Devonian period has increased markedly in recent decades, but their fossil record consists mostly of tantalizing fragments1-15. The framework for interpreting the morphology and palaeobiology of Devonian tetrapods is dominated by the near complete fossils of Ichthyostega and Acanthostega; the less complete, but partly reconstructable, Ventastega and Tulerpeton have supporting roles2,4,16-34. All four of these genera date to the late Famennian age (about 365-359 million years ago)-they are 10 million years younger than the earliest known tetrapod fragments5,10, and nearly 30 million years younger than the oldest known tetrapod footprints35. Here we describe Parmastega aelidae gen. et sp. nov., a tetrapod from Russia dated to the earliest Famennian age (about 372 million years ago), represented by three-dimensional material that enables the reconstruction of the skull and shoulder girdle. The raised orbits, lateral line canals and weakly ossified postcranial skeleton of P. aelidae suggest a largely aquatic, surface-cruising animal. In Bayesian and parsimony-based phylogenetic analyses, the majority of trees place Parmastega as a sister group to all other tetrapods

A new species of Varanus (Anguimorpha: Varanidae) from the early Miocene of the Czech Republic, and its relationships and palaeoecology

Skeletal remains of a new early Miocene (Ottnangian, MN 4 mammal zone) monitor lizard, Varanus mokrensis sp. nov., are described from two karst fissures in the Mokrá-Western Quarry (1/2001 Turtle Joint; 2/2003 Reptile Joint), Czech Republic, providing the first documented example of a European varanid for which osteological data permit a well-supported assignment to the genus Varanus. The new species is morphologically similar to the Recent Indo-Asiatic varanids of the Varanus bengalensis group. It differs from all other Varanus species on the basis of a single autapomorphy and a combination of 11 characters. As a distinguishing feature of V. mokrensis, the parietal and squamosal processes of the postorbitofrontal form a narrowly acute angle. The teeth show distinct, smooth cutting edges along the mesial and distal margins of the apical portion of their crowns. This feature is not observed in most extant Asiatic Varanus species and may represent a plesiomorphic condition. The results of parsimony phylogenetic analyses, with and without character reweighting, reveal poor resolution within Varanus. A Bayesian analysis shows V. mokrensis to be closely related to extant representatives of the Indo-Asiatic Varanus clade, with close affinities to the V. bengalensis species group. The topology of the Bayesian tree supports the hypothesis that Miocene monitors from Mokrá are representatives of a lineage that is ancestral to the well-defined clade of extant African varanids, including the early Miocene V. rusingensis. In addition, our results support a Eurasian origin for the varanid clade. The extant African Varanus species probably originated in the late Oligocene. The radiation of African varanids probably occurred during the late Oligocene to early Miocene time interval. The occurrence of Varanus in the early Miocene of Mokrá-Western Quarry corresponds to the warm phase of the Miocene Climatic Optimum. Remains of a diverse aquatic and heliophobe amphibian fauna at the 2/2003 Reptile Joint site indicate more humid conditions than those at the 1/2001 Turtle Joint site

Dynamical, biological and anthropic consequences of equal lunar and solar angular radii

The nearly equal lunar and solar angular sizes as subtended at the Earth is generally regarded as a coincidence. This is, however, an incidental consequence of the tidal forces from these bodies being comparable. Comparable magnitudes implies strong temporal modulation, as the forcing frequencies are nearly but not precisely equal. We suggest that on the basis of paleogeographic reconstructions, in the Devonian period, when the first tetrapods appeared on land, a large tidal range would accompany these modulated tides. This would have been conducive to the formation of a network of isolated tidal pools, lending support to A.S. Romer's classic idea that the evaporation of shallow pools was an evolutionary impetus for the development of chiridian limbs in aquatic tetrapodomorphs. Romer saw this as the reason for the existence of limbs, but strong selection pressure for terrestrial navigation would have been present even if the limbs were aquatic in origin. Since even a modest difference in the Moon's angular size relative to the Sun's would lead to a qualitatively different tidal modulation, the fact that we live on a planet with a Sun and Moon of close apparent size is not entirely coincidental: it may have an anthropic basis.Comment: 12 Pages, 4 figures, To appear Proc Roy Soc (A