Exila, Hedges & Conn, 2012

Hedges, S. Blair & Conn, Caitlin E., 2012, A new skink fauna from Caribbean islands (Squamata, Mabuyidae, Mabuyinae) 3288, Zootaxa 3288 (1), pp. 1-244 : 85

Genus Exila gen. nov.

Amazonian Gracile Skinks

Type species. Mabuya nigropalmata Andersson, 1918:8 .

Diagnosis. Species in this genus are characterized by (1) frontoparietals, one, (2) supraciliaries, five, (3) supraoculars, four, as reported in original description ( Andersson 1918), but supraoculars were not reported by Miralles et al. (2009), (4) prefrontal contact, present, (5) parietal contact, present, (6) rows of nuchals, 2–3, (7) dorsals + ventrals, undetermined (46–58 dorsals and 30–47 ventrals as reported by Miralles et al., 2009a, but those counts were made using a different counting method than used here), (8) total lamellae, not reported, (9) a dark middorsal stripe, absent, (10) dark dorsolateral stripes, absent, (11) a dark lateral stripe, present, and (12) dark ventral striping, absent. Body size was not reported by Miralles et al. (2009), but Andersson (1918) noted in the original description that the largest specimen was 60 mm SVL ( Table 2).

Having a single (fused) frontoparietal separates Exila from all others except Notomabuya and Panopa (single frontoparietal) and Aspronema (1–2 frontoparietals). Contact between the prefrontals separates Exila from Brasiliscincus , Capitellum , Notomabuya , and Psychosaura (no contact) and from Alinea , Aspronema , Copeoglossum , Mabuya , Manciola , Maracaiba , and Marisora (contact only rarely). From Aspronema , Brasiliscincus , Manciola , Orosaura , Panopa , Psychosaura , and Spondylurus , it is distinguished by the absence of dark dorsolateral stripes. It differs from Brasiliscincus , Capitellum , Copeoglossum , Manciola , Maracaiba , Notomabuya , Orosaura , and Varzea by having more than one pair of nuchals.

Content. A single species is placed in this genus: Exila nigropalmata ( Table 1).

Distribution. This genus is distributed in the Western Amazonian Basin and on the eastern slopes of the Andes, in Bolivia, Brazil, and Peru ( Miralles et al. 2009a; Fig. 8C ).

Etymology. The generic name ( Exila ) is a feminine noun derived from the Latin adjective exilis (lean), alluding to the thin body shape and unusually low number of midbody scale rows in this species (24–28).

Remarks. The single species placed in this genus, Exila nigropalmata , was found to be a unique and divergent lineage in published molecular phylogenies ( Miralles et al. 2009a; Miralles & Carranza 2010) and in our tree ( Fig. 5 ). Its phylogenetic position has not yet been firmly established among the various generic clades (e.g., Copeoglossum , Spondylurus ). Its possession of a unique mix of characters (one frontoparietal, contact of prefrontals, multiple nuchals, five supraciliaries, no dark dorsolateral stripes, high number of toe-IV lamellae, and thin body shape) separate it from all other genera. Recently collected material ( Miralles et al. 2009a) added knowledge to the systematics, distribution, and natural history of this otherwise poorly known species and genus.

Figures

FIGURE 5 (continued on the next page)

FIGURE 8. Distribution of the 16 genera of Neotropical skinks, Family Mabuyidae, Subfamily Mabuyinae. (A) Genera occurring in the greater Caribbean region. (B) Genera occurring exclusively in South America. (C) Additional genera occurring in South America, including one with representatives on Caribbean islands.