John D. Scanlon

Snake phylogeny based on osteology, soft anatomy and ecology.

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.

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

Current lists of species-level representation in faunas from 80 Cenozoic fossil localities at the Riversleigh World Heritage Area have been compiled by review of recorded occurrences of taxa obtained from both published and unpublished sources. More than 290 species-level taxa are represented, comprising mammals, amphibians, reptiles, birds, fishes, molluscs and crustaceans. The data are presented for the purpose of ongoing palaeoecological and biochronological studies.

Phylogeny of snakes (Serpentes): combining morphological and molecular data in likelihood, Bayesian and parsimony analyses

Abstract The phylogeny of living and fossil snakes is assessed using likelihood and parsimony approaches and a dataset combining 263 morphological characters with mitochondrial (2693 bp) and nuclear (1092 bp) gene sequences. The ‘no common mechanism’ (NCMr) and ‘Markovian’ (Mkv) models were employed for the morphological partition in likelihood analyses; likelihood scores in the NCMr model were more closely correlated with parsimony tree lengths. Both models accorded relatively less weight to the molecular data than did parsimony, with the effect being milder in the NCMr model. Partitioned branch and likelihood support values indicate that the mtDNA and nuclear gene partitions agree more closely with each other than with morphology. Despite differences between data partitions in phylogenetic signal, analytic models, and relative weighting, the parsimony and likelihood analyses all retrieved the following widely accepted groups: scolecophidians, alethinophidians, cylindrophiines, macrostomatans (sensu lato) and caenophidians. Anilius alone emerged as the most basal alethinophidian; the combined analyses resulted in a novel and stable position of uropeltines and cylindrophiines as the second‐most basal clade of alethinophidians. The limbed marine pachyophiids, along with Dinilysia and Wonambi, were always basal to all living snakes. Other results stable in all combined analyses include: Xenopeltis and Loxocemus were sister taxa (fide morphology) but clustered with pythonines (fide molecules), and Ungaliophis clustered with a boine‐erycine clade (fide molecules). Tropidophis remains enigmatic; it emerges as a basal alethinophidian in the parsimony analyses (fide molecules) but a derived form in the likelihood analyses (fide morphology), largely due to the different relative weighting accorded to data partitions.

Phylogeny of Australasian venomous snakes (Colubroidea, Elapidae, Hydrophiinae) based on phenotypic and molecular evidence

Scanlon, John D. & Lee, Michael S. Y. (2004). Phylogeny of Australasian venomous snakes (Colubroidea, Elapidae, Hydrophiinae) based on phenotypic and molecular evidence. — Zoologica Scripta, 33, 335–366.

Skull of the large non-macrostomatan snake Yurlunggur from the Australian Oligo-Miocene

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.

A Late Cretaceous (Maastrichtian) Snake Assemblage from the Maevarano Formation, Mahajanga Basin, Madagascar

ABSTRACT 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, head-first 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.

The Cretaceous marine squamate Mesoleptos and the origin of snakes

SYNOPSIS. The poorly known marine squamate Mesoleptos is reassessed based on two previously known specimens and a newly referred specimen. The three specimens of Mesoleptos zendrinii share unique characters such as long, posteriorly tapering centra and distally straight but non-pachyostotic ribs. Mesoleptos had a narrow neck (and presumably small head), long laterally compressed body, and small fore- and hindlimbs. Phylogenetic analysis suggests that Mesoleptos is the nearest relative of snakes; this phylogenetic position is consistent with its morphology being intermediate between typical marine squamates (e.g. mosasauroids) and primitive marine snakes (pachyophiids). However, this interpretation remains tentative because Mesoleptos is very poorly known, and many of the characters uniting it with mosasauroids and primitive snakes are correlates of marine hab its and/or limb reduction.

A new giant python from the Pliocene Bluff Downs Local Fauna of northeastern Queensland

Liasis dubudingala n. sp., described on the basis of isolated vertebrae from the Early Pliocene Bluff Downs Local Fauna, is the largest snake known from Australia. Dependance of vertebral proportions on intracolumnar position indicates that the fossil taxon can be excluded from the Morelia/Python clade. High neural spines suggest possible affinity with Liasis olivacea, whereas a posterior dentary fragment with small teeth is unlike L. olivacea and more similar to Liasis mackloti or species of Bothrochilus and Leiopython. As these extant species have all recently been treated as members of Liasis, the new species is assigned to that genus.

THE BASICRANIAL MORPHOLOGY OF MADTSOIID SNAKES (SQUAMATA, OPHIDIA) AND THE EARLIEST ALETHINOPHIDIA (SERPENTES)

JOHN D. SCANLON*, School of Biological Sciences, University of New South Wales, UNSW Sydney 2052, AustraliaSnakes of the extinct family Madtsoiidae are known from early LateCretaceous to Eocene deposits in Madagascar, western and northernAfrica, southwestern Europe (Spain and possibly France), and SouthAmerica (reviewed by Rage, 1998; Rage and Werner, 1999). Two gen-era occur in both the Campanian or Maastrichtian of Argentina and theearly Eocene of Australia (Patagoniophis and Alamitophis, Albino,1986; Scanlon, 1993; see Boles, 1999, for recent discussion and con-firmation of the Eocene date), and Australia is the only region in whichmadtsoiids are known later than the Eocene. Wonambi naracoortensisSmith, 1976, occurs in Pleistocene and Pliocene deposits (Scanlon andLee, 2000), and large species of Yurlunggur Scanlon, 1992, also rangefrom late Oligocene to late Pleistocene (Mackness and Scanlon, 1999).The highest known diversity and some of the best-preserved materialof madtsoiids are from the late Oligocene and Miocene of Riversleigh,northwestern Queensland, including Wonambi barriei, one or more un-named species of Yurlunggur, two small species of Nanowana, and atleast one additional new taxon (Scanlon, 1996, 1997; Scanlon and Lee,2000).Cranial remains of Wonambi naracoortensis from Naracoorte, SouthAustralia (Barrie, 1990; Scanlon and Lee, 2000), provide the best evi-dence of the morphology and affinities of any madtsoiid (though thefamily as currently recognized may not be monophyletic; see below).These specimens were originally interpreted as supporting the inclusionof Madtsoiidae in Alethinophidia (Barrie, 1990; Scanlon, 1992), butreinterpretation of the morphology and more comprehensive phyloge-netic analyses placed this lineage outside a clade including all livingsnakes, including scolecophidians as well as alethinophidians (Scanlon,1996; Scanlon and Lee, 2000; Lee and Scanlon, 2002). These resultsconfirm the interpretations of Hoffstetter (1961:155) and McDowell(1987) regarding the primitive features of madtsoiid vertebrae relativeto those of all living snakes, and conflict with the widespread assump-tions that scolecophidians are basal snakes and that all known fossilsnakes are either scolecophidians or alethinophidians (e.g., Underwood,1967; Rage, 1984, 1987; Rieppel, 1988; Zaher and Rieppel, 1999;Tchernov et al., 2000).Part of the braincase of a second Australian madtsoiid, similar to thatof Wonambi but differing conspicuously in proportions, has been rec-ognized from a late Oligocene or early Miocene deposit at Riversleigh,northwestern Queensland. This deposit contains vertebrae, ribs, and jawelements representing several taxa of madtsoiids including Nanowanagodthelpi, N. schrenki, and Wonambi barriei (Scanlon, 1996, 1997;Scanlon and Lee, 2000). However, the only vertebrae consistent in sizewith the braincase fragment are similar to those of Yurlunggur cam-fieldensisScanlon, 1992, allowing the braincase fragment to be referredto the same genus (Scanlon, 1996). All Yurlunggur vertebrae knownfrom Riversleigh have relatively higher neural spines than the somewhatlater Y. camfieldensis, so are considered specifically distinct, but taxo-nomic treatment of vertebrae is deferred pending study of recently dis-covered articulated remains.As well as Wonambi, comparisons are made with extant snakes ofsome basal lineages (anilioids and booids) and with Dinilysia patagon-* Present address: Department of Environmental Biology, Univer-sity of Adelaide, and Department of Palaeontology, South AustralianMuseum North Terrace, Adelaide SA 5000, Australia, e-mail: scanlon.john@saugov.sa.gov.auica Woodward, 1901 (?Coniacian, Late Cretaceous; Estes et al., 1970;Caldwell and Albino, 2001), which has been interpreted as a basal al-ethinophidian or a pre-alethinophidian snake of similar grade to madt-soiids (reviewed by Scanlon and Lee, 2000). I also make some com-parisons with a putative madtsoiid braincase fragment from the Ceno-manian of Wadi Abu Hashim, Sudan (Rage and Werner, 1999), andcomment on its significance.Comparisons with recent taxa are based on collections of the Queens-land Museum, Australian Museum, Macleay Museum, South AustralianMuseum, M. Archer, D. J. Barrie, and the author (details available onrequest).Riversleigh fossils are prepared using acetic acid (e.g., Archer et al.,1991) and the specimen described here is completely free of carbonatematrix. The course of canals and foramina was determined visuallyunder a binocular microscope, using a hair as a probe.Terminology for cranial anatomy either follows that in Rieppel’s(1979) review of snake basicranial evolution, or Rieppel’s terms arenoted parenthetically when different ones are preferred.Institutional Abbreviations QM F, Queensland Museum (Pa-laeontology), Brisbane.SYSTEMATIC PALEONTOLOGYREPTILIASQUAMATAOPHIDIAYURLUNGGUR Scanlon, 1992YURLUNGGUR sp.Material QM F23041.Locality Mike’s Menagerie Site (Mike’s Menagerie Local Fauna),Godthelp Hill, Riversleigh World Heritage Fossil Property, northwesternQueensland.Age The deposit forms part of ‘Tertiary System B,’ interpreted tobe late Oligocene or early Miocene in age (Archer et al., 1989, 1997).Description A fragment 22.0 mm in length comprises most of theco-ossified basisphenoid and parasphenoid (Fig. 1), here referred to as‘sphenoid’ for brevity; the width of the cultriform process immediatelyanterior to the basipterygoid processes is 7.3 mm; the same, immedi-ately anterior to ossified portions of trabeculae is 5.0 mm; the maximumwidth across the basipterygoid processes is 10.7 mm; the length of thecanal for the abducens nerve is 6.4 mm; the length of the articulatorysurface of the basipterygoid process (right) is 7.5 mm; the length of thevidian canal is greater than 6.6 mm.The dorsal surface (Fig. 1A) bears an oval, bowl-like hypophysial pit(sella turcica) centered just anterior to a line joining the posterior endsof the basipterygoid processes. It is not recessed below the posteriordorsum sellae (crista sellaris); the posterior and lateral walls are nearlyvertical, while the anterior wall is more oblique but demarcated ante-riorly by a shallowly overhanging crest approximately 2 mm across.This crest is interrupted by three small troughs probably accommodatingblood vessels (one to the left of the midline, two smaller ones to theright). A similar pattern of three anterior troughs is seen in Calabariareinhardti, and a slightly less similar condition in Xenopeltis unicolorand Loxocemus bicolor (Rieppel, 1979:figs. 5, 7), where they representthe anterior course of the ramus cranialis of the cerebral carotid.In the midline within the hypophysial pit, 0.7 mm posterior to thetransverse anterior crest, is a small foramen opening posteriorly, re-

An Oligo-Miocene Magpie Goose (Aves: Anseranatidae) from Riversleigh, Northwestern Queensland, Australia

ABSTRACT The magpie goose Anseranas semipalmata (Aves: Anseranatidae), the sole modern representative of the family, is endemic to Australia. The fossil record of Anseranatidae in Australia was until now restricted to Pliocene and younger sediments. Here we describe an anseranatid from the Oligo-Miocene Carl Creek Limestone in the Riversleigh World Heritage Property, Boodjamulla (Lawn Hill) National Park, in northwestern Queensland, as a new species and genus, based on a coracoid and two scapulae. These fossils extend the known age of the Anseranatidae lineage in Australia to about 25 million years ago. The fossil distribution of Anseranatidae now includes the Paleocene in North America, Eocene and Late Oligocene of Europe, and the Late Oligocene to earliest Miocene in Australia, indicating a globally widespread distribution of the family during the early-mid Tertiary.