Monday, April 16, 2018

[Herpetology • 2018] Eremiascincus rubiginosus • A New Species of Eremiascincus (Squamata: Sauria: Scincidae) from the Pilbara region of Western Australia


Eremiascincus rubiginosus   Mecke & Doughty, 2018

VERTEBRATE ZOOLOGY. 68(1) 

Abstract 
Lizards of the genus Eremiascincus Greer, 1979 include species from the Australian monsoonal tropics and the Lesser Sundas as well as a widespread radiation of banded forms from the Australian arid zone, some of which are ‘sand-swimmers.’ Here we describe a new, rusty red-coloured species of Eremiascincus from the Pilbara region of Western Australia. Unlike other EremiascincusEremiascincus rubiginosus sp. nov. is saxicolous and usually associated with deep gorges in the Hamersley Range. The new species differs morphologically from all other members of the genus by a combination of numerous mensural and scalation characters, including typically seven supralabials, three pairs of chin shields, a moderate-sized elliptical ear opening, smooth scales on dorsum and dorsal surface of tail lacking longitudinal ridges, scales on dorsal surface of fourth toe arranged in multiple rows with oblique sutures with only the terminal 1–4 single scales possessing transverse sutures, 24 –31 subdigital lamellae under fourth toe that are grooved and bluntly callused, 10–13 plantar scales from heel to base of third toe and dark brownish-black calli on scales of palmar and plantar surfaces. Colouration and pattern are also unique in the genus, with a rich rusty red background colour on dorsum and tail, 17–24 narrow irregular bands on nape and dorsum that are at most a single scale wide and > 40 narrow bands on tail. The new species is the seventh Eremiascincus from Western Australia and also the sixth narrow-banded species in the genus.

Key words: Australia, arid zone, endemism, Eremiascincus rubiginosus sp. nov., Eremiascincus intermediusEremiascincus musivusEremiascincus pallidus, morphology, skink, taxonomy


Fig. 1. Holotype of Eremiascincus rubiginosus sp. nov. (WAM R174519). 
 (B) Dorso-lateral view of the holotype in life. (C) Lateral view of the front part of the holotype in life. (D) Detail of dorsal aspect of head. (E) Collection location of the holotype showing the habitat of Erubiginosus sp. nov. in Dale’s Gorge, Karijini National Park, Western Australia.
 (A) – Luke Kealley, (B–E) – Ryan J. Ellis.

Eremiascincus rubiginosus new species
 E: Rusty Skinks, G: Rost-Skink

Diagnosis. A moderate-sized Eremiascincus (adult SVL 60 –82 mm) with usually seven supralabials (rarely six or eight), three pairs of chin shields, a moderate-sized elliptical ear opening (Fig. 3A), smooth dorsal scales on dorsum and tail lacking longitudinal ridges (Fig. 1A & B, Fig. 2A), scales on dorsal surface of fourth toe arranged in multiple rows with oblique sutures with only the terminal 1 –4 scales single, possessing transverse sutures, 24 –31 subdigital lamellae under fourth toe that are grooved and bluntly callused, 10– 13 plantar scales from heel to base of third toe and dark brownish-black calli on scales of palmar and plantar surfaces (Fig. 3D); background colour of dorsum and tail rich rusty red in live specimens, 17 –24 narrow irregular dark bands on nape and dorsum that are at most a single scale wide and > 40 transverse narrow dark bands on original tail (Figs. 1A & B, Fig. 2A, Fig. 4).

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Habitat. Specimens of E. rubiginosus sp. nov. throughout the species’ range have been collected in gorges, rocky gullies, riverbeds or caves surrounded by woodland. The species appears to be largely restricted to rocky habitats and may be encountered in leaf litter covering rock formations or under rock ledges (see Fig. 1E).

Etymology. The specific name is based on the Latin adjective rubiginosus (rusty red). As common names we suggest ‘Rusty skinks’ (English) and ‘Rost-Skink’ (German).

Fig. 2. Comparison of body habitus and colouration pattern in narrow-banded Eremiascincus occurring in Western Australia. (A) E. rubiginosus sp. nov. from Duck Creek, Western Australia. (B) E. intermedius from West MacDonnell National Park, Alice Springs, Northern Territory. (C) E. musivus from Dampier, Western Australia. (D) E. pallidus from Exmouth, Western Australia.
(A & C) – Brad Maryan, (B) – Peter Soltys, (D) – Brian Bush.

Discussion: 

The description of Eremiascincus rubiginosus brings the number of described Eremiascincus species to 15. Most of these show a strong fidelity to certain habitat types and substrates (Mecke et al. 2013; pers. obs.). Eremiascincus rubiginosus is a typical species from the rocky country of the Pilbara, in that it is associated with gorges, rocky gullies, riverbeds and caves in the Hamersley Range, and exhibits a rich reddish colouration as is common for many species of animals from this region. In contrast, E. musivus and E. pallidus are sand-swimmers that readily will burrow into loose sand, with both only occurring along the sandy coastline of the Pilbara and the adjacent sandy deserts. While E. rubiginosus and E. musivus do not occur together, E. rubiginosus and E. pallidus may be encountered in sympatry in the Onslow area (Fig. 5). 

Morphologically, E. rubiginosus shares many characters with other narrow-banded Eremiascincus from the Australian arid zone, all of which are sand-swimmers. The saxicoline habitat preferences of Erubiginosus are intriguing, because it is the first narrow-banded species of Eremiascincus to have a strong association with rocky habitats and possesses characters (bluntly callused palmar and plantar scales, callused lamellae) that may be an adaption for rock climbing, similar to the saxicoline species Cryptoblepharus ustulatus Horner, 2007 from the same general area in the Hamersley Range. It is likely that Erubiginosus has evolved from an E. pallidus-like ancestor, such that the microhabitat of sand in gorges was a bridging habitat for the evolution of a more derived habitat preference of a gorge-dwelling lizard. Morphology in the genus Eremiascincus, however, may be of limited value to elucidate phylogenetic relationships, and former phenetic groupings (e.g., Greer 1979, 1989) have not been supported by molecular phylogenetic approaches (Reeder 2003; Rabosky et al. 2007; Skinner 2007; Mecke et al. 2009; S.C. Donnellan & P. Doughty, unpublished data). Studies on the phylogenetic position and ecology of E. rubiginosus would be of interest.


 Sven Mecke and Paul Doughty. 2018. A New Species of Eremiascincus (Squamata: Sauria: Scincidae) from the Pilbara region of Western Australia. VERTEBRATE ZOOLOGY. 68(1); 27-37. 

 Kurzfassung Die Gattung Eremiascincus Greer, 1979 beinhaltet Arten der australischen Monsunwälder und der Kleinen Sundainseln sowie eine weitverbreitete Gruppe von Formen mit dorsalen Bändern, die die australischen Trockengebiete bewohnt und von denen einige Arten aufgrund ihrer Lebensweise als ‘Australische Sandfische’ bezeichnet werden. Wir beschreiben hier eine neue, rostrot gefärbte Art der Gattung Eremiascincus aus der Pilbara-Region in West Australien. Im Gegensatz zu anderen Arten der Gattung ist Eremiascincus rubiginosus sp. nov. felsbewohnend und lebt überwiegend in tiefen Schluchten in der Hamersley Range. Die neue Art unterscheidet sich morphologisch von allen anderen Arten der Gattung durch eine Kombination zahlreicher metrischer und meristischer Merkmale, wie typischerweise sieben Supralabialia, drei paar Kinnschilden, einer mittelgroßen, elliptischen Ohröffnung, einer glatten dorsalen Rücken- und Schwanzbeschuppung, die keine längsorientierten Kiele aufweist, Schuppen auf der Dorsalseite der vierten Zehe bis auf die letzten 1–4 Schuppen in mehreren Reihen mit schrägverlaufenden Rändern, 24–31 gefurchte und mit Schwielen versehene Subdigitallamellen unter der vierten Zehe, 10–13 Plantarschuppen zwischen Ferse und Basis der dritten Zehe und dunkelgefärbten, braunschwarzen Schwielen auf den palmaren und plantaren Schuppen. Die Färbung und das Muster der neuen Art sind ebenfalls einzigartig innerhalb der Gattung und zeichnen sich durch eine satte rostrote dorsale Grundfarbe auf Rücken und Schwanz sowie 17 –24 schmale, irreguläre Bänder auf dem Rücken, die höchstens so breit sind wie eine Schuppenreihe, und > 40 Bänder auf dem Schwanz, aus. Eremiascincus rubiginosus sp. nov. ist die siebte Art der Gattung aus West Australien und die sechste Art mit schmalen Bändern. 

    

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