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Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana., (Copyright © 2015, American Association for the Advancement of Science.)

Derived large-mouthed snakes (macrostomatans) possess numerous specializations in their skull and lower jaws that allow them to consume large vertebrate prey. In contrast, basal snakes lack these adaptations and feed primarily on small prey items. The sequence of osteological and behavioral modifications involved in the evolution of the macrostomatan condition has remained an open question because of disagreement about the origin and interrelationships of snakes, the paucity of well-preserved early snake fossils on many continental landmasses, and the lack of information about the feeding ecology of early snakes. We report on a partial skeleton of a new 3.5-m-long snake, Sanajeh indicus gen. et sp. nov., recovered from Upper Cretaceous rocks of western India. S. indicus was fossilized in association with a sauropod dinosaur egg clutch, coiled around an egg and adjacent to the remains of a ca. 0.5-m-long hatchling. Multiple snake-egg associations at the site strongly suggest that S. indicus frequented nesting grounds and preyed on hatchling sauropods. We interpret this pattern as "ethofossil" preservation of feeding behavior. S. indicus lacks specializations of modern egg-eaters and of macrostomatans, and skull and vertebral synapomorphies place it in an intermediate position in snake phylogeny. Sanajeh and its large-bodied madtsoiid sister taxa Yurlunggur camfieldensis and Wonambi naracoortensis from the Neogene of Australia show specializations for intraoral prey transport but lack the adaptations for wide gape that characterize living macrostomatan snakes. The Dholi Dungri fossils are the second definitive association between sauropod eggs and embryonic or hatchling remains. New fossils from western India provide direct evidence of feeding ecology in a Mesozoic snake and demonstrate predation risks for hatchling sauropod dinosaurs. Our results suggest that large body size and jaw mobility afforded some non-macrostomatan snakes a greater diversity of prey items than previously suspected on the basis of extant basal snakes., Competing Interests: The authors have declared that no competing interests exist.

The apparent biotic affinities between the mainland and the island in the Western Ghats-Sri Lanka biodiversity hotspot have been interpreted as the result of frequent migrations during recent periods of low sea level. We show, using molecular phylogenies of two invertebrate and four vertebrate groups, that biotic interchange between these areas has been much more limited than hitherto assumed. Despite several extended periods of land connection during the past 500,000 years, Sri Lanka has maintained a fauna that is largely distinct from that of the Indian mainland. Future conservation programs for the subcontinent should take into account such patterns of local endemism at the finest scale at which they may occur.

Russell's viper, Vipera russelli (Shaw), is distributed erratically in 10 south Asian countries and is a leading cause of fatal snake bite in Pakistan, India, Bangladesh, Sri Lanka, Burma and Thailand. In Burma it has been the 5th most important cause of death. Its venom is of great interest to laboratory scientists and clinicians. The precoagulant activity of the venom was used by Macfarlane and others to elucidate the human clotting cascade. Up to 70% of the protein content is phospholipase A2, present in the form of at least 7 isoenzymes. Possible clinical effects of the enzyme include haemolysis, rhabdomyolysis, pre-synaptic neurotoxicity, vasodilatation and shock, release of endogenous autacoids and interaction with monoamine receptors. Russell's viper bite is an occupational hazard of rice farmers throughout its geographical range. Defibrination, spontaneous haemorrhage, shock and renal failure develop with frightening rapidity. In several countries, Russell's viper bite is the commonest cause of acute renal failure. There is a fascinating geographical variation in the clinical manifestations, doubtless reflecting differences in venom composition. Conjunctival oedema is unique to Burma, acute pituitary infarction to Burma and south India, and rhabdomyolysis and neurotoxicity to Sri Lanka and south India. Treatment with potent specific antivenom rapidly controls bleeding and clotting disorders, but may not reverse nephrotoxicity and shock. Causes of death include shock, pituitary and intracranial haemorrhage, massive gastrointestinal haemorrhage and acute tubular necrosis or bilateral renal cortical necrosis. The paddy farmer and the Russell's viper coexist in fragile symbiosis. The snake controls rodent pests but inevitably interacts with man, often with mutually disastrous results.

Calotes versicolor has single gland on the left side in neck region, just anterior to heart, while Ptyas mucosus and Bungarus caeruleus have 2 equal-sized glands located in the thyro-thymic region. The gland was spheroidal and measured 0.5 to 1.5 mm in diameter. Size of the gland varied individually in relation to the body size. The gland was composed of cell masses and follicles, and was well vascularized. Histology of the gland showed marked individual variation. Ciliated and goblet cells were present.