Relationships between the major lineages of snakes are assessed based on a phylogenetic analysis of the most extensive phenotypic data set to date (212 osteological, 48 soft anatomical, and three ecological characters). The marine, limbed Cretaceous snakes Pachyrhachis and Haasiophis emerge as the most primitive snakes: characters proposed to unite them with advanced snakes (macrostomatans) are based on unlikely interpretations of contentious elements or are highly variable within snakes. Other basal snakes include madtsoiids and Dinilysia--both large, presumably non-burrowing forms. The inferred relationships within extant snakes are broadly similar to currently accepted views, with scolecophidians (blindsnakes) being the most basal living forms, followed by anilioids (pipesnakes), booids and booid-like groups, acrochordids (filesnakes), and finally colubroids. Important new conclusions include strong support for the monophyly of large constricting snakes (erycines, boines. pythonines), and moderate support for the non-monophyly of the trophidophiids' (dwarf boas). These phylogenetic results are obtained whether varanoid lizards, or amphisbaenians and dibamids, are assumed to be the nearest relatives (outgroups) of snakes, and whether multistate characters are treated as ordered or unordered. Identification of large marine forms, and large surface-active terrestrial forms, as the most primitive snakes contradicts with the widespread view that snakes arose via minute, burrowing ancestors. Furthermore, these basal fossil snakes all have long flexible jaw elements adapted for ingesting large prey ('macrostomy'), suggesting that large gape was primitive for snakes and secondarily reduced in the most basal living foms (scolecophidians and anilioids) in connection with burrowing. This challenges the widespread view that snake evolution has involved progressive, directional elaboration of the jaw apparatus to feed on larger prey.

The Madtsoiidae were medium sized to gigantic snakes with a fossil record extending from the mid-Cretaceous to the Pleistocene, and spanning Europe, Africa, Madagascar, South America and Australia. This widely distributed group survived for about 90 million years (70% of known ophidian history), and potentially provides important insights into the origin and early evolution of snakes. However, madtsoiids are known mostly from their vertebrae, and their skull morphology and phylogenetic affinities have been enigmatic. Here we report new Australian material of Wonambi, one of the last-surviving madtsoiids, that allows the first detailed assessment of madtsoiid cranial anatomy and relationships. Despite its recent age, which could have overlapped with human history in Australia, Wonambi is one of the most primitive snakes known--as basal as the Cretaceous forms Pachyrhachis and Dinilysia. None of these three primitive snake lineages shows features associated with burrowing, nor do any of the nearest lizard relatives of snakes (varanoids). These phylogenetic conclusions contradict the widely held 'subterranean' theory of snake origins, and instead imply that burrowing snakes (scolecophidians and anilioids) acquired their fossorial adaptations after the evolution of the snake body form and jaw apparatus in a large aquatic or (surface-active) terrestrial ancestor.

Understanding the origin and early evolution of snakes from lizards depends on accurate morphological knowledge of the skull in basal lineages, but fossil specimens of archaic snakes have been rare, and either fragmentary or difficult to study as a result of compression by enclosing sediments. A number of Cenozoic fossil snakes from Australia have vertebral morphology diagnostic of an extinct group, Madtsoiidae, that was widespread in Gondwana from mid-Cretaceous (Cenomanian) to Eocene times, and also reached Europe in the late Cretaceous period. Despite this long history, only about half the skull is known from the best-known species Wonambi naracoortensis, and the few known cranial elements of other species have added little further evidence for phylogenetic relationships. Conflicting hypotheses have been proposed for their relationships and evolutionary significance, either as basal ophidians with many ancestral (varanoid- or mosasaur-like) features, or advanced (macrostomatan) alethinophidians of little relevance to snake origins. Here I report two partial skeletons referred to Yurlunggur, from the late Oligocene and early Miocene of northern Australia, which together represent almost the complete skull and mandible. The exceptionally preserved skulls provide new evidence linking Yurlunggur with Wonambi and other madtsoiids, falsifying predictions of the macrostomatan hypothesis, and supporting the exclusion of Madtsoiidae from the clade including all extant snakes.

2006) Current status of species-level representation in faunas from selected fossil localities in the Riversleigh World Heritage Area,

snakes (Colubroidea, Elapidae, Hydrophiinae) based on phenotypic and molecular evidence. -Zoologica Scripta , 33 , 335 -366. Phylogenetic relationships among Hydrophiinae (Australasian and marine elapid snakes) are inferred using 87 characters from external, skeletal, hemipenial and internal anatomy, ecology, and chromosomes as well as available sequences of two mitochondrial genes (cytochrome b and 16S rRNA). Parsimony analysis of the combined data retrieves many widely accepted clades; while observed bootstrap or branch (Bremer) support for these is often weak, most have never been corroborated previously by a rigorous numerical analysis. Sea kraits ( Laticauda ) and Solomon Islands elapids are basal to the remaining hydrophiines (Australian terrestrial forms and hydrophiin sea snakes). The latter clade includes three main lineages: a large-bodied oviparous lineage, a small-bodied oviparous lineage, and a viviparous lineage (which also includes the hydrophiin sea snakes, strongly reaffirmed as monophyletic). While the Solomons retain a relictual fauna, New Guinea has less endemism and has been invaded multiple times by Australian lineages, so there is no clear 'stepping stone' pattern supporting a northern (Asian, rather than Gondwanan) biogeographical origin.

No abstract

The rare Australian venomous elapid snake`Echiopsis' atriceps has been the subject of considerable taxonomic instability with the ®ve known specimens assigned to four genera by various authorities. Phylogenetic af®nities of the rare Elapognathus minor also are poorly understood and have been the subject of some disagreement. To examine the phylogenetic af®nities of these two rare taxa, a molecular data set comprising 1680 base pairs of mtDNA was assembled from a representative of each of the terrestrial Australian viviparous elapid genera and two species of Drysdalia, a genus about which there also has been phylogenetic controversy. A total of 936 base pairs of 12S rRNA, 454 base pairs of 16S rRNA and 290 base pairs of cytochrome b mtDNA were sequenced for 15 species. The Asian elapid Naja naja was used as the outgroup. These mtDNA regions provided 195, 38 and 72 parsimony informative sites, respectively, for a total of 315 parsimony informative characters. Unweighted phylogenetic analyses were performed under both parsimony and neighbour-joining criteria. Parsimony analyses of the unweighted, combined data set resulted in a single fully resolved most parsimonious tree 1225 steps long. The neighbour-joining tree differed by only a single weakly supported branch. These data strongly support a sister group relationship between`Echiopsis' atriceps and the Australian broadheaded snakes of the genus Hoplocephalus with a bootstrap value of 99%. Templeton tests soundly reject all previous taxonomic arrangements for this species. Our data also strongly support a sister group relationship between Elapognathus minor and Drysdalia coronata with a bootstrap value of 98%. Importantly, Drysdalia coronata and Drysdalia coronoides do not form a monophyletic group, supporting some previous studies. Based on our results, we allocate`Echiopsis' atriceps to a new monotypic genus and re-describe Elapognathus to include`Drysdalia' coronata.

A Late Cretaceous (Maastrichtian) assemblage of snakes from the Maevarano Formation of the Mahajanga Basin, northwestern Madagascar, constitutes the only fossil record of snakes from the island. The assemblage, which lived in a highly seasonal, semi-arid climate, includes only archaic forms belonging to the Madtsoiidae and Nigerophiidae, and therefore no representatives of extant Malagasy clades. A large sample of exquisitely preserved vertebrae and several ribs are assigned to Madtsoia madagascariensis, a long (almost 8 m), heavy-bodied ambush predator inferred to have subdued its prey via constriction. A new madtsoiid genus and species, Menarana nosymena, is represented by several associated vertebrae and rib fragments, and part of the basicranium. It was approximately 2.4 m long and appears to have been a powerful, headfirst burrower, or at least to have had a burrowing ancestry. Kelyophis hechti, by far the smallest snake in the assemblage (<1 m long), is a new genus and species of primitive nigerophiid based on six isolated vertebral specimens. It was not as specialized for the aquatic lifestyle inferred for other nigerophiids. Although recent molecular phylogeographic studies suggest an early colonization of Madagascar by snakes ancestral to modern Malagasy boids, with subsequent vicariant evolution, the Maevarano Formation assemblage offers no support for this hypothesis. The repeated pattern of extinct archaic lineages being replaced on Madagascar by basal stocks of extant clades (e.g., Anura, Crocodyliformes, Avialae, Mammalia) after the Late Cretaceous is also a plausible scenario for the origin of the extant Malagasy snake fauna.