Salvadora gymnorhachis, Hernández-Jiménez & Flores-Villela & Campbell, 2019

Hernández-Jiménez, Carlos Alberto, Flores-Villela, Oscar & Campbell, Jonathan Atwood, 2019, of patch-nosed snake (Colubridae: Salvadora Baird and Girard, 1853) from Oaxaca, Mexico, Zootaxa 4564 (2), pp. 588-600 : 589-596

Salvadora gymnorhachis , sp. nov.

Figs. 1, 2

urn:lsid:zoobank.org:act:FA3E5069-814D-4890-BC45-489F9AF4133B

Paratypes. Five, all from the state of Oaxaca, Mexico. A juvenile female ( AMNH 84992 ) from San Pablo Mitla , 1900 m ; an adult male ( AMNH 91090 ) from 8.3 km north of Mitla , 2100 m ; and an adult female ( AMNH 100910 ) from 2 km west of San Lorenzo Albarradas , 2000 m ; all three from Distrito de Tlacolula. An adult female ( AMNH 100909 ) from 12 km (via road) southwest of San Pedro y San Pablo Ayutla, 1760 m , Distrito de Mixe ; and an adult female ( UIMNH 56849 ), near Santa Catalina Quierí, 2364 m , Distrito de Yautepec .

Diagnosis. Salvadora gymnorhachis differs from all its congeners by lacking a pale vertebral line, and dorsolateral stripes extending only to about the middle of the body (vs other species in which these stripes extend by throughout whole length of the body) ( Table 1); Salvadora gymnorhachis also differs from S. grahamiae , S. bairdi , S. mexicana , and S. lemniscata by having 11 maxillary teeth followed by a diastema and three enlarged teeth (9–10+ 3 in S. grahamiae and S. bairdi ; 14–15+ 3 in S. mexicana and S. lemniscata ); it further differs from S. mexicana and S. lemniscata by having fewer than 105 subcaudals (vs more than 124), a divided preocular (vs single in S. mexicana and S. lemniscata ); from S. deserticola and S. hexalepis by having second and third supralabials in contact with loreal (vs third, fourth, and sometimes fifth contacting loreal); and from S. intermedia by having six and five scale rows separating dorsolateral stripes on anterior and middle part of body, respectively (vs 3 and 1-2 scale rows separating stripes on anterior and middle part of body, respectively).

Description of holotype. Rostral with free lateral edges, extending slightly between internasal suture; plates behind rostral on top of head including prefrontals, supraoculars, frontal and paired parietals; on side of head prenasal separated from second supralabial; loreal situated above second and third supralabials; two preoculars, upper larger, contacting prefrontal and supraocular; lower preocular small, situated above third and fourth supralabials; two postoculars at left side, lower contacting fifth and sixth supralabials; one postocular at right side touching the large fifth supralabial; temporals 2 + 2, lower contacting fifth, sixth, and seventh supralabials ( Fig. 2A ); 8/8 supralabials; fourth and fifth touching eye; 8/8 infralabials, first pair meeting at midventral line behind small mental, first four pairs reaching anterior genials; fourth infralabial enlarged more than length of anterior genials; posterior genials smaller than anterior genials, separated by single row of two median scales; dorsal scales in 19 rows immediately behind head at level of ventral 3, 17 rows at level of ventral scale 13; 16 rows at midbody at level of ventral scale 90, and 13 scale rows anterior to vent at level of ventral scale 170; 182 ventrals; cloacal scute divided, bordered laterally by small scales; tail incomplete, 80+ subcaudals; 11 maxillary teeth, increasing in size posteriorly, followed by diastema and three enlarged teeth (11+3).

Measurements. Total length 612 mm; SVL 471 mm; TaL 141 mm (tip missing), comprising about 23 % of total length.

Coloration. Pattern consisting of a pair of dark dorsolateral stripes (89 Jet black; Smithe, 1975) beginning at level of postoculars, extending to middle of body where stripes grade into ground color; dorsolateral stripes occupying upper half of second dorsal scale row and covering four scale rows on anterior part of body, reduced to three scales wide just before becoming inconspicuous at about mid-body; field between dorsolateral stripes brown (223B Verona brown), six rows wide at anterior part of body, five at middle of body where stripes begin to fade; posterior part of body gray (45 Smoke gray); ventral surface of body whitish (92 Pale horn) except for salmon color (6 Salmon) on lateral portion of ventrals of posterior part of body and venter of tail; lateral edges of ventral scales black.

Variation of Paratypes . Except for minor differences in scutelation, paratypes closely resemble holotype ( Table 2); ventrals in females 176–184, single male with 186 ventrals; subcaudals 92–103 in females, tail incomplete in single male; supralabials 8/ 8 in most specimens, except in female from near Municipality of San Lorenzo Albarradas , Oaxaca with 9 on one side; third and fourth supralabial reaching second (lower) postocular on individuals from District of Tlacolula , Oaxaca , whereas female from Municipality of Santa Catalina Quieri , Oaxaca ( UIMNH 56849 ) and female from Municipality of San Pedro y San Pablo Ayutla , Oaxaca (AMNH R– 100909) with only fifth supralabial touching postocular; anterior nasal in contact with second supralabial in all specimens, except the one from Municipality of Mitla ( AMNH 91090 ), Oaxaca, in which anterior nasal slightly separated from second supralabials; two supralabials, reaching loreal in all specimens except for one female ( AMNH 100910 ) with three on left side; body length 852 to 975 mm, male being largest in series and female holotype smallest ( Table 2).

Male closely resembling females, including holotype, in lacking vertebral stripe; male paler, however, with little more than vestiges of dorsolateral stripes; prior to preservation lips and throat white, in contrast to yellow venter of anterior portion of trunk and two lowermost rows of scales (Bogert, unpublished notes); posteriorly yellow color of the venter grading into salmon color extending to underside of tail; basal portions of lower dorsal scales on the posterior of trunk appreciably darker than margins; individual having brownish body flanked with yellow anteriorly gradually becoming gray speckled with black posteriorly; dorsolateral stripes obsolescent in preserved specimen, more conspicuous in live snake.

Etymology. The specific epithet comes from the Greek “ gymnós ”, meaning “naked”, and “ ráchḭ ” dorsum, in reference that this is the only species of Salvadora that does not have dorsal vertebral stripes and has incomplete dorsolateral ones.

Habitat and Conservation. The holotype was found beneath a rock in a transitional area between a crop field and pine-oak forest ( Fig. 3A ). The distribution of this species undoubtedly has been greatly modified by anthropogenic activities, which has increased the rate of deforestation at the type locality ( Fig. 3B ). None of the collection sites are located in protected areas. Despite intensive fieldwork in Oaxaca, only six specimens of this species have been collected, all between 1960 and 2014.

Distribution. Most individuals have been collected in central Oaxaca along the unnumbered State secondary road between Mitla and Ayutla in the Distritos de Tlacolula and Mixe at elevations of 1760 to 2364 m. The species is also known in the south near Santa Catalina Quierí in Distrito de Yautepec at elevations exceeding 1600 m. The entire range of this species is drained by the upper tributaries of the Río Tehuantepec ( Fig. 4 ). Most of the river valleys of the region contain fingers of upper tropical deciduous forest extending from lower coastal regions and the higher slopes and ridges are covered with pine-oak forest.

The phylogenetic analysis performed gave one phylogenetic tree ( Fig. 5 ) with maximun likelihood value of - 2709.59. The genus Salvadora is retrieved as monophyletic, with sampled species forming two strongly supported clades ( mexicana group and grahamiae group). Salvadora gymnorachis is nested within the grahamiae group as the sister taxon of Salvadora intermedia .

Figures

FIGURE 2. Head of holotype of Salvadora gymnorhachis sp. nov. (MZFC 28775). A, lateral view. B, dorsal view. Drawing based on a photograph taken of preserved specimen.

FIGURE 3. Habitat of Salvadora gymnorhachis sp. nov. A, type locality, pine-oak vegetation at 2060 m elevation. B, general view of the area at the type locality with habitat degradation (deforested areas, corn field and road), San Pedro y San Pablo Ayutla, Distrito Mixe, Oaxaca.

FIGURE 4. Geographic distribution of Salvadora gymnorhachis sp. nov. The star indicates the type locality, circles localities for paratypes.

FIGURE 5. Molecular phylogenetic relationships of the genus Salvadora, based on ND4 mitochondrial gene, under the criterion of Maximun Likelihood (HKY+G model). Numbers under the nodes represent Maximum likelihood bootstrap support values.