Tuesday, February 25, 2014

A new systematic arrangement for skinks

One-quarter of all lizards are skinks, and they have been traditionally placed in the single family  Scincidae. 1,579 species of skinks are known and they compose the largest group of saurians.  Other large lizard families, such as Gekkonidae and Iguanidae have been partitioned into multiple families , based mainly on evidence from molecular phylogenies. Subfamilies and informal suprageneric groups have been used for skinks, defined by morphological traits and supported increasingly by molecular phylogenies.

In a new paper S. Blair Hedges morphological diagnoses all nine families of skinks (Scincomorpha).

Recently, a seven-family classification for skinks was proposed to replace that largely informal classification, create more manageable taxa, and facilitate systematic research on skinks.

Representatives of 125 (84%) of the 154 genera of skinks are available in the public sequence databases and have been placed in molecular phylogenies that support the recognition of these families. However, two other molecular clades with species that have long been considered distinctive morphologically belong to two new families described in this paper:  Ristellidae and Ateuchosauridae.

The Ateuchosauridae is a family of lygosomoid skink possessing diagnostic characters: Meckel's groove not recorded; parietals small or absent and nuchals absent ; the outer preanal scales overlap the inner preanals; scales on digits in two rows; the iris is nearly as dark as the pupil. Also, the frontoparietals are paired; the frontal is long and constricted, longer than frontoparietals plus interparietal; and the prefrontals are small and separated. Ateuchosauridae is distributed in Japan (Ryukyu Archipelago), southeastern China, and northeastern Vietnam.The family includes the Chinese forest skin shown below.


The Ristellidae contains the genus Lankascincus  (10 sp.) and Ristella Gray (4 sp.). This is a family of lygosomoid skink with: more than 11 premaxillary teeth; Meckel's groove is completely obliterated (closed) by the overlapping and fusion of dentary; parietals meet behind interparietal; parietal bordered along its posterior edge by two or more temporals; nuchals usually absent (undifferentiated); outer preanal scales overlap inner preanals; scales on dorsal surface of fourth toe mostly in a single row; iris variable. Ristellidae is distributed in southern India and Sri Lanka.  The family includes the genus Lankascincus shown below.


The family Acontidae  holds 26 species of African and Madagascar skinks. Including the Acontia sp. shown below.



The family Egerniidae holds 58 species in nine genera including the Tribolonotus shown below. The family occurs in Australia and Australasia



The family Eugongylidae  holds 418 species in 37 genera. including the Lampropholis guichenoti shown below. The family occurs in Australia and Australasia



The family Lygosomidae 52 species including the Mochlus guineensis  shown below, the family is Asian



The family Mabuyidae has 190 species and is Neotropical in distribution. Copeoglossum aurea shown blow is a member of this family.

The family Sphenomorphidae has 546 species and has an Asian and Australian distribution. It includes the Sphenomorphus sabanus from Borneo below.

The family Scincidae contains 273 species that are distributed from Africa and Asia to the Western Hemisphere and includes Plestiodon fasciatus shown below.


Citation
Hedges SB 2014. The high-level classification of skinks (Reptilia, Squamata, Scincomorpha). Zootaxa 3765:317-338.

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