Rena Baird & Girard, 1853

Adalsteinsson, Solny A., Branch, William R., Trape, Sébastien, Vitt, Laurie J. & Hedges, S. Blair, 2009, Molecular phylogeny, classification, and biogeography of snakes of the Family Leptotyphlopidae (Reptilia, Squamata), Zootaxa 2244, pp. 1-50 : 19-20

Genus Rena Baird & Girard, 1853

Rena Baird and Girard, 1853: 142 . Type species: Rena humilus Baird and Girard, 1853 , by subsequent designation by Stejneger, 1892 [dated 1891]: 501.

Diagnosis. Species of Rena have 14 midbody scale rows, 10 (12 rarely) midtail scale rows, 168–312 middorsal scale rows, 9–21 subcaudals, 2–3 supralabials, moderate or large (rarely small) anterior supralabials, 205–389 mm maximum adult total length, a body shape of 26–60 (total length/width), a relative tail length of 3.1–8.6 %, a tail shape of 1.9–3.8, no striped pattern, brown or purplish brown dorsal color, and white venter (Table 2). They also have a small supraocular scale. They are distinguished from the other genus in this subtribe, Tricheilostoma , by having a white (not brown or pale brown) venter, usually two supralabials (three in R. bressoni , R. dissecta , and R. myopica ), and in having a higher number (on average) of middorsal scales (Table 2). The support for this group was 100% BP and 100% PP for the four-gene tree ( Fig. 3); only one species was included in the nine-gene tree ( Fig. 4).

Content. Eleven species ( Table 1; Fig. 7).

Distribution. Rena is distributed from North America (California, Utah, and Kansas) south through Middle and South America (exclusive of the high Andes) to Uruguay and Argentina on the Atlantic side ( Fig. 8).

Etymology. The generic name is feminine and derived from the Latin noun ren (kidney), apparently in allusion to the kidney color (reddish brown) of the type species.

Remarks. Species placed here in Rena include members of the former dulcis Group of " Leptotyphlops " ( Orejas-Miranda 1967; Peters 1970) but exclude those placed by Orejas-Miranda (1967) in the " macrolepis Group." Even earlier, Klauber (1940) referred to this assemblage as the dulcis - humilus Group. We recognize the species Rena boettgeri (southern Baja California, Mexico), originally described as a full species ( Werner 1899) but more recently treated as a subspecies ( Smith & Larsen 1974) or placed in the synonymy of R. humilis ( McDiarmid et al. 1999) . It has a relatively large sequence divergence ( Fig. 3) from a nearby sample of Rena humilis ( Fig. 3) from northern Baja California, and the two taxa have nearly non-overlapping middorsal scale count differences ( Grismer 1999; Hahn 1979). Five representatives of Rena ( R. boettgeri , R. dissecta , R. dulcis , R. humilis , and Rena sp. B ) were included in the molecular phylogenetic analyses, and they formed a strongly supported group, deeply divergent from T. macrolepis . Because of this, and the concordance in scalation and coloration distinguishing these two groups of species, we recognize the former " macrolepis Group" as the Genus Tricheilostoma (see below). However, the original character used to define the group, the relationship between the posterior border of the rostral and the eye level ( Orejas-Miranda 1967), is not useful in diagnosing the two genera. Most members (seven of 11) of Rena occur in Middle and North America, together with several species in the genus Epictia (subtribe Epictina ). We concur with the taxonomic arrangement for R. dulcis and relatives proposed by Dixon and Vaughn (2003). The species R. nicefori was not included in the size range for total length because the adult status of the single specimen (90 mm) is unknown ( Hedges 2008).

Rena is distributed in three isolated areas ( Fig. 8): North and Middle America ( Rena boettgeri , R. bressoni , R. dissecta , R. dulcis , R. humilis , R. maxima , and R. myopica ), northern South America ( Rena affinis , R. dimidiata , and R. nicefori ), and Argentina ( R. unguirostris ). Species in these three areas are distinct morphologically as well. Compared with the species from northern South America, the North and Middle American species have relatively high middorsal scale counts (199–309 versus 168–215) and short tails (3.1– 6.7 versus 5.7–8.6). In both characters, R. unguirostris is similar to the North and Middle American species (241–312 and 3.1–5.1, respectively), but it has a small anterior supralabial scale, which is unusual among New World leptotyphlopids. Based on this evidence, the three groups could be recognized as species groups: the humilis Group, the dimidiata Group, and the unguirostris Group. Future molecular sampling will determine whether the dimidiata and unguirostris groups belong to the Genus Rena .