Convergent evolution and character correlation in burrowing reptiles: towards a resolution of squamate relationships

The affinities of three problematic groups of elongate, burrowing reptiles (amphisbaenians, dibamids and snakes) are reassessed through a phylogenetic analysis of all the major groups of squamates, including the important fossil taxa Sineoamphisbaena, mosasauroids and Pachyrhachis; 230 phylogenetically informative osteological characters were evaluated in 22 taxa. Snakes (including Pachyrhachis) are anguimorphs, being related firstly to large marine mosasauroids, and secondly to monitor lizards (varanids). Scincids and cordylids are not related to lacertiforms as previously thought, but to anguimorphs. Amphisbaenians and dibamids are closely related, and Sineoamphisbaena is the sister group to this clade. The amphisbaenian-dibamid-Sineoamphisbaena clade, in turn, is related to gekkotans and xantusiids. When the fossil taxa are ignored, snakes, amphisbaenians and dibamids form an apparently well-corroborated clade nested within anguimorphs. However, nearly all of the characters supporting this arrangement are correlated with head-first burrowing (miniaturization, cranial consolidation, body elongation, limb reduction), and invariably co-occur in other tetrapods with similar habits. These characters are potentially very misleading because of their sheer number and because they largely represent reductions or losses. It takes very drastic downweighting of these linked characters to alter tree topology: if fossils are excluded from the analysis, a (probably spurious) clade consisting of elongate, fossorial taxa almost always results. These results underscore the importance of including all relevant taxa in phylogenetic analyses. Inferring squamate phylogeny depends critically on the inclusion of certain (fossil) taxa with combinations of character states that demonstrate convergent evolution of the elongate, fossorial ecomorph in amphisbaenians and dibamids, and in snakes. In the all-taxon analysis, the position of snakes within anguimorphs is more strongly-corroborated than the association of amphisbaenians and dibamids with gekkotans. When the critical fossil taxa are deleted, snakes ‘attract’ the amphisbaenian-dibamid clade on the basis of a suite of correlated characters. While snakes remain anchored in anguimorphs, the amphisbaenian-dibamid clade moves away from gekkotans to join them. Regardless of the varying positions of the three elongate burrowing taxa, the interrelationships between the remaining limbed squamates (‘lizards’) are constant; thus, the heterodox affinities of scincids, cordylids, and xantusiids identified in this analysis appear to be robust. Finally, the position of Pachyrhachis as a basal snake rather than (as recently suggested) a derived snake is supported on both phylogenetic and evolutionary grounds.     

The skull of the Upper Cretaceous snake Dinilysia patagonica Smith‐Woodward, 1901, and its phylogenetic position revisited

The cranial anatomy of Dinilysia patagonica, a terrestrial snake from the Upper Cretaceous of Argentina, is redescribed and illustrated, based on high‐resolution X‐ray computed tomography and better preparations made on previously known specimens, including the holotype. Previously unreported characters reinforce the intriguing mosaic nature of the skull of Dinilysia, with a suite of plesiomorphic and apomorphic characters with respect to extant snakes. Newly recognized plesiomorphies are the absence of the medial vertical flange of the nasal, lateral position of the prefrontal, lizard‐like contact between vomer and palatine, floor of the recessus scalae tympani formed by the basioccipital, posterolateral corners of the basisphenoid strongly ventrolaterally projected, and absence of a medial parietal pillar separating the telencephalon and mesencephalon, amongst others. We also reinterpreted the structures forming the otic region of Dinilysia, confirming the presence of a crista circumfenestralis, which represents an important derived ophidian synapomorphy. Both plesiomorphic and apomorphic traits of Dinilysia are treated in detail and illustrated accordingly. Results of a phylogenetic analysis support a basal position of Dinilysia, as the sister‐taxon to all extant snakes. The fossil taxa Yurlunggur, Haasiophis, Eupodophis, Pachyrhachis, and Wonambi appear as derived snakes nested within the extant clade Alethinophidia, as stem‐taxa to the crown‐clade Macrostomata. The hypothesis of a sister‐group relationship between Dinilysia and Najash rionegrina, as suggested by some authors, is rejected by the results of our analysis. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164 , 194–238.     

The phylogeny of varanoid lizards and the affinities of snakes

Evidence that platynotan squamates (living varanoid lizards, snakes and their fossil relatives) are monophyletic is presented. Evolutionary relationships within this group are then ascertained through a cladistic analysis of 144 osteological characters. Mosasauroids (aigialosaurs and mosasaurs), a group of large marine lizards, are identified as the nearest relatives of snakes, thus resolving the long-standing problem of snake affinities. The mosasauroid–snake clade (Pythonomorpha) is corroborated by 40 derived characters, including recumbent replacement teeth, thecodonty, four or fewer premaxillary teeth, supratemporal–prootic contact, free mandibular tips, crista circumfenestralis, straight vertical splenio-angular joint, loss of posterior ramus of the coronoid, reduced basipterygoid processes, reduced interpterygoid vacuity, zygosphene–zygantral articulations, and absence of epiphyses on the axial skeleton and skull. After mosasauroids, the next closest relatives of snakes are varanids (Varanus, Saniwa and Saniwides) and lanthanotids (Lanthanotus and Cherminotus). Derived features uniting varanids and lanthanotids include nine cervical vertebrae and three or fewer pairs of sternal ribs. The varanid–lanthanotid–pythonomorph clade, here termed Thecoglossa, is supported by features such as the anteriorly positioned basal tubera, and the loss of the second epibranchial. Successive outgroups to thecoglossans are Telmasaurus, an unresolved polytomy (Estesia, Gobidermatidae and Helodermatidae), Paravaranus and Proplatynota. The ''necrosaurs'' are demonstrated to be an artificial (polyphyletic) assemblage of primitive platynotans that are not particularly closely related to each other.Snakes are presumed to have evolved from small, limbless, burrowing lizards and the inability of previous analyses to resolve the affinities of snakes has been attributed to extensive convergence among the numerous lineages of such lizards. The present study contradicts this claim, demonstrating that the problem is due instead to omission of critical fossil taxa. No modern phylogenetic analysis of squamate relationships has simultaneously included both mosasauroids and snakes: previous studies have therefore failed to identify the mosasauroid–snake association and the suite of derived characters supporting it. Mosasauroids are large aquatic animals with well-developed appendages, and none of the derived characters uniting mosasauroids and snakes is obviously correlated with miniaturization, limb reduction or fossoriality. Recognition that mosasauroids, followed by varanids and lanthanotids, are the nearest relatives of snakes will also facilitate studies of relationships within snakes, which until now have been hampered by uncertainty over the most appropriate (closely-related) lizard outgroups.     

Soft anatomy, diffuse homoplasy, and the relationships of lizards and snakes

Most previous phylogenetic analyses of squamates (‘lizards’ and snakes) employing large character sets have focused on osteology. Soft anatomical traits bearing on this problem have usually been considered in small subsets. Here, a comprehensive phylogenetic analysis of squamate soft anatomy is attempted. 126 informative characters are assessed for 23 squamate lineages, representing snakes, amphisbaenians, dibamids, and all the traditionally recognized ‘families’ of lizards. The traditionally recognized groupings Iguania, Scleroglossa, Gekkota, Scincomorpha, Anguimorpha and Varanoidea are corroborated in this analysis. More controversial taxa are resolved as follows. Xantusiids, amphisbaenians and dibamids cluster with gekkotans, and snakes are strongly allied with anguimorphs in general, and varanids in particular. Nearly all these clades are congruent with those found in a recent comprehensive osteological analysis; the strong support for snake‐varanid relationships found in both studies is particularly notable. This congruence is surprising given that previous studies of soft anatomy tended to give differing and often heterodox results. These previous results can be attributed to overrepresentation of misleading characters in small isolated data sets. Such misleading signals are minimized when data sets are combined. For instance, the snake‐varanid clade is contradicted by many characters, and analyses of particular organ systems therefore give differing results. However, characters that are incongruent with the snake‐varanid clade also disagree with each other (diffuse homoplasy), rather than forming coherent support for some particular alternative clade (concerted homoplasy). In a combined analysis these incongruent but diffuse characters cancel each other out to leave a very strong (and orthodox) phylogenetic signal. These results underscore the view that the raw amount of homoplasy — as revealed by consistency and retention indices — is not the only determinant of phylogenetic signal; the distribution of that homoplasy is also important. Thus, questioning a phylogenetic hypothesis (e.g. the snake‐varanid clade) by identifying numerous conflicting characters is insufficient — the structure of the conflicting characters should be assessed in a rigorous phylogenetic analysis.     

A combined evidence phylogenetic analysis of Anguimorpha (Reptilia: Squamata)

Anguimorpha is a clade of limbed and limbless squamates with ca. 196 extant species and a known fossil record spanning the past 130 million years. Morphology‐based and molecule‐based phylogenetic analyses disagree on several key points. The analyses differ consistently in the placements of monstersaurs (e.g. Gila Monsters), shinisaurs (Crocodile Lizards), the anguid Anniella (American Legless Lizards), carusioids (Knobby Lizards), and the major clades within Varanus (Monitor Lizards). Given different data sources with such different phylogenetic hypotheses, Anguimorpha is an excellent candidate for a combined phylogenetic analysis. We constructed a data matrix consisting of 175 fossil and extant anguimorphs, and 2281 parsimony‐informative characters (315 morphological characters and 1969 molecular characters). We analysed these data using the computer program TNT using the “new technology search” with the ratchet. Our result is novel and shows similarities with both morphological and molecular trees, but is identical to neither. We find that a global combined evidence analysis (GCA) does not recover a holophyletic Varanoidea, but omission of fossil taxa reveals cryptic molecular support for that group. We describe these results and others from global morphological analysis, extant‐only morphological analysis, molecular data‐only analyses, combined evidence analysis of extant taxa, and GCA. © The Willi Hennig Society 2010.     

Molecular phylogenetics of squamata: the position of snakes, amphisbaenians, and dibamids, and the root of the squamate tree

Squamate reptiles (snakes, lizards, and amphisbaenians) serve as model systems for evolutionary studies of a variety of morphological and behavioral traits, and phylogeny is crucial to many generalizations derived from such studies. Specifically, the traditional dichotomy between Iguania (anoles, iguanas, chameleons, etc.) and Scleroglossa (skinks, geckos, snakes, etc.) has been correlated with major evolutionary shifts within Squamata. We present a molecular phylogenetic study of 69 squamate species using approximately 4600 (2876 parsimony-informative) base pairs (bp) of DNA sequence data from the nuclear genes RAG-1(approximately 2750 bp) and c-mos(approximately 360 bp) and the mitochondrial ND2 region (approximately 1500 bp), sampling all major clades and most major subclades. Under our hypothesis, species previously placed in Iguania, Anguimorpha, and almost all recognized squamate families form strongly supported monophyletic groups. However, species previously placed in Scleroglossa, Varanoidea, and several other higher taxa do not form monophyletic groups. Iguania, the traditional sister group of Scleroglossa, is actually highly nested within Scleroglossa. This unconventional rooting does not seem to be due to long-branch attraction, base composition biases among taxa, or convergence caused by similar selective forces acting on nonsister taxa. Studies of functional tongue morphology and feeding mode have contrasted the similar states found in Sphenodon(the nearest outgroup to squamates) and Iguania with those of Scleroglossa, but our findings suggest that similar states in Sphenodonand Iguania result from homoplasy. Snakes, amphisbaenians, and dibamid lizards, limbless forms whose phylogenetic positions historically have been impossible to place with confidence, are not grouped together and appear to have evolved this condition independently. Amphisbaenians are the sister group of lacertids, and dibamid lizards diverged early in squamate evolutionary history. Snakes are grouped with iguanians, lacertiforms, and anguimorphs, but are not nested within anguimorphs.     

Ecophysiological steps of marine adaptation in extant and extinct non-avian tetrapods

Marine reptiles and mammals are phylogenetically so distant from each other that their marine adaptations are rarely compared directly. We reviewed ecophysiological features in extant non-avian marine tetrapods representing 31 marine colonizations to test whether there is a common pattern across higher taxonomic groups, such as mammals and reptiles. Marine adaptations in tetrapods can be roughly divided into aquatic and haline adaptations, each of which seems to follow a sequence of three steps. In combination, these six categories exhibit five steps of marine adaptation that apply across all clades except snakes: Step M1, incipient use of marine resources; Step M2, direct feeding in the saline sea; Step M3, water balance maintenance without terrestrial fresh water; Step M4, minimized terrestrial travel and loss of terrestrial feeding; and Step M5, loss of terrestrial thermoregulation and fur/plumage. Acquisition of viviparity is not included because there is no known case where viviparity evolved after a tetrapod lineage colonized the sea. A similar sequence is found in snakes but with the haline adaptation step (Step M3) lagging behind aquatic adaptation (haline adaptation is Step S5 in snakes), most likely because their unique method of water balance maintenance requires a supply of fresh water. The same constraint may limit the maximum body size of fully marine snakes. Steps M4 and M5 in all taxa except snakes are associated with skeletal adaptations that are mechanistically linked to relevant ecophysiological features, allowing assessment of marine adaptation steps in some fossil marine tetrapods. We identified four fossil clades containing members that reached Step M5 outside of stem whales, pinnipeds, sea cows and sea turtles, namely Eosauropterygia, Ichthyosauromorpha, Mosasauroidea, and Thalattosuchia, while five other clades reached Step M4: Saurosphargidae, Placodontia, Dinocephalosaurus, Desmostylia, and Odontochelys. Clades reaching Steps M4 and M5, both extant and extinct, appear to have higher species diversity than those only reaching Steps M1 to M3, while the total number of clades is higher for the earlier steps. This suggests that marine colonizers only diversified greatly after they minimized their use of terrestrial resources, with many lineages not reaching these advanced steps. Historical patterns suggest that a clade does not advance to Steps M4 and M5 unless these steps are reached early in the evolution of the clade. Intermediate forms before a clade reached Steps M4 and M5 tend to become extinct without leaving extant descendants or fossil evidence. This makes it difficult to reconstruct the evolutionary history of marine adaptation in many clades. Clades that reached Steps M4 and M5 tend to last longer than other marine tetrapod clades, sometimes for more than 100 million years.     

Anatomy and relationships of Pachyrhachis problematicus,a primitive snake with hindlimbs

The anatomy of Pachyrhachis problematicus, an elongate, limb-reduced squamate from the Upper Cretaceous of Israel, is described and evaluated in detail. Previously considered a snake-like ''lizard'' of uncertain affinities, it is here shown to be the most primitive snake, and the sister-group to all other snakes. Pachyrhachis exhibits numerous derived characters uniting it with modern snakes (scolecophidians and alethinophidians): e.g. mobile premaxilla-maxilla articulation, braincase enclosed by frontals and parietals, sagittal parietal crest, absence of tympanic recess, single postdentary bone, over 140 presacral vertebrae, and complete loss of shoulder girdle and forelimb. However, it is more primitive than all modern snakes in retaining some strikingly primitive (lizard-like) features: presence of a jugal, squamosal, normal sacral attachment, and well-developed hindlimb composed of femur, tibia, fibula, and tarsals. Pachyrhachis provides additional support for the hypothesis that snakes are most closely related to Cretaceous marine lizards (mosasauroids). Almost all of the derived characters proposed to unite snakes and mosasauroids are highly developed in Pachyrhachis: the mobile mandibular symphysis, intramandibular joint, long and recurved pterygoid teeth, quadrate suspended by the supratemporal, loosely united pelvic elements (ilium, ischium, and pubis), and separate astragalus and calcaneum.     

Higher-level relationships of snakes inferred from four nuclear and mitochondrial genes

Higher-level snake relationships are inferred from sequence analyses of one nuclear gene (C-mos) and three mitochondrial genes (12S rRNA, 16S rRNA and cytochrome b). Extant snakes belong to two lineages: the fossorial Scolecophidia, which feed on small prey on a frequent basis, and the ecologically diverse Alethinophidia ('typical' snakes), which feed on large prey on an infrequent basis. The vast majority of Alethinophidia, if not all of them, belong to two clades, corresponding to two distinct prey neutralization modes: unimodal constriction for the Henophidia (locomotor and feeding systems coupled) and injection of toxic saliva, in addition (or not) to diverse alternate modes of constriction, for the Caenophidia (locomotor and feeding systems uncoupled). Within Alethinophidia, non-macrostomatan (small gape) Aniliidae (genus Anilius) and macrostomatan (large gape) Tropidophiidae (genera Trachyboa and Tropidophis), both from the Neotropics, are closest relatives. Although our data are insufficient to robustly infer the ancestral mode of life of snakes, we find evidence of plasticity in the basic ecological and trophic modes of snakes. Consequently, the macrostomatan condition should not be treated a priori as a derived character state devoid of homoplasy.     

The phylogeny of squamate reptiles (lizards, snakes, and amphisbaenians) inferred from nine nuclear protein-coding genes

Squamate reptiles number approximately 8000 living species and are a major component of the world's terrestrial vertebrate diversity. However, the established relationships of the higher-level groups have been questioned in recent molecular analyses. Here we expand the molecular data to include DNA sequences, totaling 6192 base pairs (bp), from nine nuclear protein-coding genes (C-mos, RAG1, RAG2, R35, HOXA13, JUN, alpha-enolase, amelogenin and MAFB) for 19 taxa representing all major lineages. Our phylogenetic analyses yield a largely resolved phylogeny that challenges previous morphological analyses and requires a new classification. The limbless dibamids are the most basal squamates. Of the remaining taxa (Bifurcata), the gekkonids form a basal lineage. The Unidentata, squamates that are neither dibamids nor gekkonids, are divided into the Scinciformata (scincids, xantusiids, and cordylids) and the Episquamata (remaining taxa). Episquamata includes Laterata (Teiformata, Lacertiformata, and Amphisbaenia, with the latter two joined in Lacertibaenia) and Toxicofera (iguanians, anguimorphs and snakes). Our results reject several previous hypotheses that identified either the varanids, or a burrowing lineage such as amphisbaenians or dibamids, as the closest relative of snakes. Our study also rejects the monophyly of both Scleroglossa and Autarchoglossa, because Iguania, a species-rich lineage (ca. 1440 sp.), is in a highly nested position rather than being basal among Squamata. Thus iguanians should not be viewed as representing a primitive state of squamate evolution but rather a specialized and successful clade combining lingual prehension, dependence on visual cues, and ambush foraging mode, and which feeds mainly on prey avoided by other squamates. Molecular time estimates show that the Triassic and Jurassic (from 250 to 150 Myr) were important times for squamate evolution and diversification.     

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.     

Combining phylogenomics and fossils in higher-level squamate reptile phylogeny: molecular data change the placement of fossil taxa

Molecular data offer great potential to resolve the phylogeny of living taxa but can molecular data improve our understanding of relationships of fossil taxa? Simulations suggest that this is possible, but few empirical examples have demonstrated the ability of molecular data to change the placement of fossil taxa. We offer such an example here. We analyze the placement of snakes among squamate reptiles, combining published morphological data (363 characters) and new DNA sequence data (15,794 characters, 22 nuclear loci) for 45 living and 19 fossil taxa. We find several intriguing results. First, some fossil taxa undergo major changes in their phylogenetic position when molecular data are added. Second, most fossil taxa are placed with strong support in the expected clades by the combined data Bayesian analyses, despite each having >98% missing cells and despite recent suggestions that extensive missing data are problematic for Bayesian phylogenetics. Third, morphological data can change the placement of living taxa in combined analyses, even when there is an overwhelming majority of molecular characters. Finally, we find strong but apparently misleading signal in the morphological data, seemingly associated with a burrowing lifestyle in snakes, amphisbaenians, and dibamids. Overall, our results suggest promise for an integrated and comprehensive Tree of Life by combining molecular and morphological data for living and fossil taxa.     

Rib and vertebral micro‐anatomical characteristics of hydropelvic mosasauroids

Houssaye, A. & Bardet, N. 2011: Rib and vertebral micro‐anatomical characteristics of hydropelvic mosasauroids. Lethaia, Vol. 45, pp. 200–209. Mosasauroids are squamates secondarily adapted to an aquatic life that dominated the sea during the Late Cretaceous. Mosasauroids display distinct types of morphologies illustrating steps in the adaptation of this lineage to increasing obligatory habits. Hydropelvic mosasauroids (sensu Caldwell & Palci) were the most highly adapted to an open‐sea environment. Contrary to plesiopelvic forms, they are considered to have relied on a hydrodynamic, rather than hydrostatic buoyancy and body trim control strategies. This led previous authors to consider that these taxa would favour bone lightening (osteoporotic‐like condition) rather than bone mass increase. Although an osteoporotic‐like state was indeed described in Clidastes and Tylosaurus, bone mass increase was reported in Platecarpus. As a matter of fact, the new analysis of vertebral thin sections of various taxa combined with the reanalysis of the rib sections available in Sheldon’s PhD thesis in a micro‐anatomical perspective reveals the absence of both bone mass increase and bone lightening in these organisms. These taxa in fact display a vertebral micro‐anatomy much peculiar within squamates. It characteristically corresponds to a true network of thin trabeculae whose tightness varies between taxa, probably as a result of both species and individual size differences, particularly the latter. In addition, analysis of the pattern of vascularization as observed in hydropelvic mosasauroids, which is unique amongst squamates, suggests that large size in hydropelvic mosasauroids would mainly rely on protracted rather than faster growth rates. □Histology, hydropelvic mosasauroids, micro‐anatomy, ribs, vascularization, vertebrae.     

Examining the utility of categorical models and alleviating artifacts in phylogenetic reconstruction of the Squamata (Reptilia)

Reconstruction artifacts are a serious hindrance to the elucidation of phylogenetic relationships and a number of methods have been devised to alleviate them. Previous studies have demonstrated a striking disparity in the evolutionary rates of the mitochondrial (mt) genomes of squamate reptiles (lizards, worm lizards and snakes) and the reconstruction artifacts that may arise from this. Here, to examine basal squamate relationships, we have added the mt genome of the blind skink Dibamus novaeguineae to the mitogenomic dataset and applied different models for resolving the squamate tree. Categorical models were found to be less susceptible to artifacts than were the commonly used noncategorical phylogenetic models GTR and mtREV. The application of different treatments to the data showed that the removal of the fastest evolving sites in snakes improved phylogenetic signal in the dataset. Basal divergences remained, nevertheless, poorly resolved. The proportion of both fast-evolving and conserved sites in the squamate mt genomes relative to sites with intermediate rates of evolution suggests rapid early divergences among squamate taxa and at least partly explains the short internal relative to external branches in the squamate tree. Thus, mt and nuclear trees may never reach full agreement because of the short branches characterizing these divergences.     

Complete mitochondrial genomes of three lizard species and the systematic position of the Lacertidae (Squamata)*

Complete mitochondrial (mt) genomes were sequenced from representatives of three lacertid lizards: Podarcis siculus, Podarcis muralis and Phoenicolacerta kulzeri. In all three genomes the arrangement of the 22 tRNAs, the two rRNAs and the 13 protein‐coding genes conforms to the common vertebrate arrangement. The phylogenetic position of Lacertidae within the order Squamata was determined through sequence analyses based on large sections of complete mt genomes. The number of nucleotide sites used for tree construction was 9234 when outgroup taxa were included, and 10 499 when only Squamata were compared. The phylogenetic analyses confirmed the sister group relationship between Lacertidae and Amphisbaenia as previously proposed on the basis of molecular data. Additionally, Bayesian analysis revealed a well supported clade comprising (Gekkonidae (Lacertidae + Amphisbaenia)), which is not in accordance with the traditional morphological view and most of the previous molecular studies. It confirms, however, the close relationship between Gekkonidae and Amphisbaenia as revealed in a recent study based on complete mt genomes from a smaller number of taxa. Intra‐ and intergeneric sequence comparisons of six commonly used marker genes showed rather high levels of divergence within the Lacertidae. In the intrageneric comparison the control region proved to be considerably more conserved than the protein coding genes.     

Scolecophidia (Serpentes) of the Late Oligocene and Early Miocene,North America,and a fossil history overview

An abundant fossil record of the snake clade Scolecophidia exists in Europe; however, the minute snake is noticeably absent in reports about the North American Paleogene and Neogene. Presented here are four localities from Florida, USA, that contain scolecophidian remains older than the Pleistocene: Thomas Farm (late Early Miocene, Hemingfordian Land Mammal Age, LMA), Live Oak (Oligocene-Miocene transition, latest Arikareean LMA), White Springs 3B (late Arikareean LMA), and Brooksville 2 (Late Oligocene, middle Arikareean LMA). These remains extend their known existence by about 26 m.y. and are now the oldest reported scolecophidian remains in North America. Molecular evidence on extant scolecophidians concludes that these tiny snakes have a Gondwanan origin. Interestingly, the oldest record of a scolecophidian is from Europe (Belgium) and dates back to the middle Paleocene (MP 1–5). The earliest African record of the snake clade comes from the Paleocene-Eocene boundary in Morocco. The clade is apparently absent from Europe and Middle East deposits dating from the latest Eocene through to the latest Oligocene (MP 19–30) and to the Early Miocene (MN 4). A portion of this time is known as the booid ‘Dark Period’ which represents an apparent response to global aridization and cooling. Scolecophidians appear to re-emerge into the southern Eurasian record in the Early Miocene (MN 4) and become widely dispersed throughout Europe and Middle East. The fossil record of these minute snakes is largely absent in southern Asia and South America. It is possible that the current lack of a decent fossil scolecophidian record outside of Europe and Middle East is due mainly to a bias in the methodology to recover fossils; wet sieving sediments through < 1.0 mm mesh is needed to recover the minuscule vertebrae.     

Integrated Analyses Resolve Conflicts over Squamate Reptile Phylogeny and Reveal Unexpected Placements for Fossil Taxa

Squamate reptiles (lizards and snakes) are a pivotal group whose relationships have become increasingly controversial. Squamates include >9000 species, making them the second largest group of terrestrial vertebrates. They are important medicinally and as model systems for ecological and evolutionary research. However, studies of squamate biology are hindered by uncertainty over their relationships, and some consider squamate phylogeny unresolved, given recent conflicts between molecular and morphological results. To resolve these conflicts, we expand existing morphological and molecular datasets for squamates (691 morphological characters and 46 genes, for 161 living and 49 fossil taxa, including a new set of 81 morphological characters and adding two genes from published studies) and perform integrated analyses. Our results resolve higher-level relationships as indicated by molecular analyses, and reveal hidden morphological support for the molecular hypothesis (but not vice-versa). Furthermore, we find that integrating molecular, morphological, and paleontological data leads to surprising placements for two major fossil clades (Mosasauria and Polyglyphanodontia). These results further demonstrate the importance of combining fossil and molecular information, and the potential problems of estimating the placement of fossil taxa from morphological data alone. Thus, our results caution against estimating fossil relationships without considering relevant molecular data, and against placing fossils into molecular trees (e.g. for dating analyses) without considering the possible impact of molecular data on their placement.     

A reevaluation of early amniote phylogeny

A new phylogenetic analysis of early amniotes based on 124 characters and 13 taxa (including three outgroups) indicates that synapsids are the sister-group of all other known amniotes. The sister-group of Synapsida is Sauropsida, including Mesosauridae and Reptilia as its two main subdivisions. Reptilia is divided into Parareptilia and Eureptilia. Parareptilia includes Testudines and its fossil relatives (Procolophonidae, Pareiasauria and Millerettidae), while Eureptilia includes Diapsida and its fossil relatives (Pakothyris and Captorhinidae). Parts of the phylogeny are robust, such as the sister-group relationship between procolophonids and testudines, and between pareiasaurs and the testudinomorphs (the clade including procolophonids and testudines). Other parts of the new tree are not so firmly established, such as the position of mesosaurs as the sister-group of reptiles. The new phylogeny indicates that three major clades of amniotes extend from the present to the Palaeozoic. These three clades are the Synapsida (including Mammalia), Parareptilia (including Testudines), and Eureptilia (including Sauria). In addition, the Procolophonidae, a group of Triassic parareptiles, are the sister-group of Testudines.     

A tiny lizard (Lepidosauria,Squamata) from the Lower Cretaceous of Spain

Abstract: The smallest living amniotes are all lizards, but the fossil history of this size trait in Squamata is difficult to follow because small skeletons have low preservation potential and are often hard to detect in the field. A new squamate taxon, Jucaraseps grandipes gen. et sp. nov., is here described on the basis of an articulated skeleton from the Early Cretaceous Spanish lagerstätten of Las Hoyas. It differs from other known Mesozoic lizards in combining very small body size with a short rostrum, low maxillary tooth count, a relatively slender and elongated body, and short limbs with large hind feet. Phylogenetic analysis using TNT places it on the stem of a clade encompassing scincomorphs, gekkotans, snakes, amphisbaenians and anguimorphs. Comparison with modern lizards suggests it was probably a cryptic surface or subsurface ground dweller but not a burrower.