A review of iguanian and anguimorph lizard genitalia (Squamata: Chamaeleonidae; Varanoidea, Shinisauridae, Xenosauridae, Anguidae) and their phylogenetic significance: comparisons with molecular data sets

We compare phylogenetic hypotheses for iguanian (chameleonids) and anguimorph lizard groups (varanoids, xenosauroids, anguids) which were generated from analyses of genital (hemipenial) morphology, with recent molecular phylogenetic approaches towards the same groups. Taxa with infraspecific communication by means of visible, sexually dimorphic epigamic characters usually have less diverse genital structures than taxa with less developed visible epigamic characters but with a more highly developed chemical intersexual communication. Generally, it turned out in the cases considered here, that phylogenetic hypotheses based on hemipenial characters coincide much better with molecular-genetic phylogenies than with earlier concepts based solely on external morphology. It seems that genital morphological characters are phylogenetically more informative – on both the species and the supraspecific level – than external morphological characters at least in these examples, because the former seem not to be affected by environmental selective pressures but seem to be only subject to sexual selection. Our data suggest that sexual selective pressure on genital structural diversity is higher the less sexually dimorphic, optical cues for infraspecific communication have evolved. They further suggest a correlation with the mating system (single versus multiple matings).     

A NEW ANGUIMORPH LIZARD FROM THE LOWER MIOCENE OF NORTH-WEST BOHEMIA, CZECH REPUBLIC

Abstract:  The cranial remains of a new Lower Miocene anguimorph, Merkurosaurus ornatus gen. et sp. nov., are described from north-west Bohemia (Czech Republic). The animal is morphologically very similar to the Recent Shinisaurus crocodilurus , but it differs in several ways. The distinctive features of Merkurosaurus are: the nasal process of premaxilla is long and slender with a bilaterally constricted shaft and bilaterally broadened dorsal portion; the dorsal portion of the nasal process divides into three processes of which the median one is the longest; the ornamented surface of the parietal is subdivided into five pustule-like mounds on both right and left sides, with one further mound around the posterior and lateral margins of the parietal foramen. A close phylogenetic affinity to the anguimorph genera Shinisaurus , Bahndwivici , Dalinghosaurus and Carusia , and partially to Xenosaurus , is indicated by characters such as: frontal fused with deep cristae cranii; lateral border of frontals strongly constricted between orbits; double interorbital row of large mounds diverge posteriorly along orbital margin; sculptured postorbital ramus of jugal; small mounds on frontal and parietal with ornamented vermiculate structures; and parietal foramen within parietal but close to anterior margin. Merkurosaurus is the only taxon of this affinity known from the Cenozoic of Eurasia.     

Hidden support from unpromising data sets strongly unites snakes with anguimorph ‘lizards’

A combined analysis of nuclear, mitochondrial and morphological data robustly resolves snakes as the sister taxon to anguimorph ‘lizards’. Analysed in isolation, nuclear DNA (nDNA) produces a trichotomy between snakes, iguanians and anguimorphs, mitochondrial DNA (mtDNA) is largely uninformative at deeper levels, and morphology tends to nest snakes deep within anguimorphs or with various legless squamate groups. When analysed simultaneously, the nuclear signal is sufficiently strong that mtDNA and morphology are constrained to choose between alternative resolutions of the iguanian–anguimorph–snake trichotomy (generated by the nDNA) – and both support the snake–anguimorph solution. Combined analyses of fast‐evolving or idiosyncratically evolving markers (mtNDA, morphology) with conservative traits (e.g. nuclear genes) might be the best way to resolve ancient, closely spaced divergences. Fast or idiosyncratic markers potentially provide the most information about short, ancient internodes, but can converge on spurious trees if analysed in isolation. However, if constrained to only choosing between plausible trees, such data can contribute unique and valuable phylogenetic signal that resolves such problematic divergences.     

Molecular Phylogenetics, tRNA Evolution, and Historical Biogeography in Anguid Lizards and Related Taxonomic Families

Phylogenetic relationships among lizards of the families Anguidae, Anniellidae, Xenosauridae, and Shinisauridae are investigated using 2001 aligned bases of mitochondrial DNA sequence from the genes encoding ND1 (subunit one of NADH dehydrogenase), tRNA(Ile), tRNA(Gln), tRNA(Met), ND2, tRNA(Trp), tRNA(Ala), tRNA(Asn), tRNA(Cys), tRNA(Tyr), and COI (subunit I of cytochrome c oxidase), plus the origin for light-strand replication (O(L)) between the tRNA(Asn) and the tRNA(Cys) genes. The aligned sequences contain 1013 phylogenetically informative characters. A well-resolved phylogenetic hypothesis is obtained. Because monophyly of the family Xenosauridae (Shinisaurus and Xenosaurus) is statistically rejected, we recommend placing Shinisaurus in a separate family, the Shinisauridae. The family Anniellidae and the anguid subfamilies Gerrhonotinae and Anguinae each form monophyletic groups receiving statistical support. The Diploglossinae*, which appears monophyletic, is retained as a metataxon (denoted with an asterisk) because its monophyly is statistically neither supported nor rejected. The family Anguidae appears monophyletic in analyses of the DNA sequence data, and statistical support for its monophyly is provided by reanalysis of previously published allozymic data. Anguid lizards appear to have had a northern origin in Laurasia. Taxa currently located on Gondwanan plates arrived there by dispersal from the north in two separate events, one from the West Indies to South America and another from a Laurasian plate to Morocco. Because basal anguine lineages are located in western Eurasia and Morocco, formation of the Atlantic Ocean (late Eocene) is implicated in the separation of the Anguinae from its North American sister taxon, the Gerrhonotinae. Subsequent dispersal of anguine lizards to East Asia and North America appears to have followed the Oligocene drying of the Turgai Sea. The alternative hypothesis, that anguine lizards originated in North America and dispersed to Asia via the Bering land bridge with subsequent colonization of Europe and Morocco, requires a phylogenetic tree seven steps longer than the most parsimonious hypothesis. North African, European, and West Asian anguines were isolated from others by the rapid uplift of Tibet in the late Oligocene to Miocene. Phylogenetic analysis of evolutionary changes in the gene encoding tRNA(Cys) suggests gradual reduction of dihydrouridine (D) stems by successive deletion of bases in some lineages. This evolutionary pattern contrasts with the one observed for parallel elimination of the D-stem in mitochondrial tRNAs of eight other reptile groups, in which replication slippage produces direct repeats. An unusual, enlarged TpsiC (T) stem is inferred for tRNA(Cys) in most species.