Gerrhonotus mccoyi sp. nov., 1828

García-Vázquez, Uri Omar, Contreras-Arquieta, Arturo, Trujano-Ortega, Marysol & de Oca, Adrián Nieto-Montes, 2018, A New Species of Gerrhonotus (Squamata: Anguidae) from the Cuatro Ciénegas Basin, Coahuila, Mexico, Herpetologica 74 (3), pp. 269-278 : 270-274

Gerrhonotus mccoyi sp. nov.

( Figs. 1 , 2 ; Table 1)

Gerrhonotus infernalis Baird 1859 : Good (1994), in part.

Holotype. — MZFC 29654 (field number UOGV 1438), adult male from Poza Churince , municipality of Cuatro Ciénegas, Coahuila, Mexico (26°55 ′ 11.9 ′ ′ N, 102°06 ′ 53.2 ′ ′ W; datum ¼ WGS84), 739 m elevation, collected 9 September 2007 by U.O. García-Vázquez, M. Trujano-Ortega, and A. Contreras-Arquieta.

Paratypes. — Fifteen specimens; all from the municipality of Cuatro Ciénegas , Coahuila, Mexico: 13 ( MZFC 29655–66 , 29669 ) from the same locality as the holotype and two ( MZFC 29667–68 ) from Pozas Azules, Rancho Pronatura (26°49 ′ 32.9 ′ ′ N, 102°01 ′ 20.9 ′ ′ W; datum ¼ WGS84), 714 m elevation .

Diagnosis. — Gerrhonotus mccoŋi sp. nov. can be distinguished from its congeners by a combination of characters which includes the presence of a cantholoreal scale (72%; n ¼ 16), a dark mark extending anteriorly from the lower temporal scales through the lower border of the orbit to the preocular or cantholoreal scales, keeled dorsal scales, usually (75%; n ¼ 16) 7–9 dorsal cross-bands mostly interrupted or barely discernible on middorsum (few cross-bands continuous, noticeable across middorsum in some specimens; midsection of cross-bands paler, narrower than the lateral sections), usually indiscernible vertical dark bars on the lateral fold (few, faint bars occasionally present), and black flecks scattered on the venter.

Comparisons with other species ( Table 2). — Gerrhonotus mccoŋi sp. nov. can be distinguished from the other species of the genus by having black flecks scattered on the venter (venter immaculate or with marks other than black flecks, or dark marks restricted to the sides of the venter in the other species [venter pale gray or pale brown, distinctly mottled with white in G. infernalis and G. rhombifer ; dark marks restricted to the sides of the venter rarely present in G. liocephalus , G. ophiurus , and G. parƲus ; usually a row of small dark spots on each side of the venter in G. cf. liocephalus from Western Mexico —in this latter species, the dark spots tend to merge into dark longitudinal stripes in some specimens, and a gray midventral stripe is present in some specimens]). Gerrhonotus mccoŋi sp. nov. differs from G. farri , G. lazcanoi , G. lugoi , G. parƲus , and G. rhombifer by having keeled dorsal scales (dorsal scales smooth in the other species); from G. farri , G. infernalis , G. lazcanoi , G. lugoi , G. ophiurus , G. parƲus , and G. rhombifer by having a dorsal body pattern usually composed of cross-bands mostly interrupted or barely discernible on middorsum (cross-bands continuous, conspicuous across middorsum present in the other species); and from G. liocephalus , G. ophiurus , and G. cf. liocephalus from Western Mexico by usually lacking discernible dark bars on the lateral fold (dark bars on the lateral fold prominent in the other species). Gerrhonotus mccoŋi sp. nov. can be distinguished from all of the species of the genus, except G. liocephalus and G. ophiurus , by having a dark temporal-cantholoreal mark (dark temporalcantholoreal mark absent in the other species [present only in young specimens, vestigial in adults, in G. infernalis and G. rombifer ; head completely black in G. lazcanoi ]); and from G. farri , G. infernalis , G. lazcanoi , and G. lugoi by usually having a cantholoreal scale (cantholoreal scale usually absent [92%, n ¼ 39] in G. infernalis , and absent in the other species).

Description of holotype ( Fig. 1 ). —Adult male with both hemipenes partially everted. Head scales flat, smooth. Snout bluntly rounded in dorsal view, truncate in lateral view. Rostral ~ 1.5 X wider than tall, bordered posteriorly by one medial postrostral and one anterior internasal on each side of postrostral. Postrostral kite-shaped, 1.3 X wider than long, in narrow contact anteriorly with rostral, broad contact anterolaterally with anterior internasal and posterolaterally with supranasal on each side, and narrow contact posteriorly with posterior internasals. Anterior internasals approximately as wide as, and slightly shorter than, postrostral, each in contact laterally with first supralabial and nasal, and posteriorly with postrostral and supranasals. Supranasals 1.2 X wider than long, obliquely oriented, separated medially from each other by postrostral. Posterior internasals larger than supranasals, obliquely oriented, each in broad contact laterally with supranasal and upper postnasal, posterolaterally with canthal, and posteriorly with frontonasal. Frontonasal 1.5 X wider than long, in contact laterally with canthal on either side and posteriorly with prefrontals. Prefrontals 1.2 X wider than long, in narrow and broad contact laterally with canthal and cantholoreal, respectively; in contact posteriorly with first median supraocular, one small scale between first median supraocular and frontal, and frontal. Frontal 2.1 X longer than wide, in contact laterally with one small scale between prefrontal and second median supraocular, second and third median supraoculars, and frontoparietal on either side, and posteriorly with interparietal. Frontoparietals approximately as wide as long, each in contact laterally with third and fourth median supraoculars, posterolaterally with upper primary temporal, and posteriorly with parietal. Median supraoculars 5/5; first 1.9 X longer than wide; second as wide as long; third, fourth, and fifth 1.2–1.6 X wider than long; lateral supraoculars 3/3, much smaller than median supraoculars. Interparietal 1.3 X longer than wide, kite-shaped, enclosed by frontoparietals, parietals, and interoccipital; pineal eye poorly defined, situated on its posterior half. Parietals 1.1 X longer than interparietal, in contact anterolaterally with upper primary temporal, posterolaterally with a larger upper temporal (presumably representing fused upper secondary and upper tertiary temporals), posteriorly with occipital, and posteromedially with interoccipital. Two rows of postoccipitals; transverse scale rows on each side of postoccipitals extending laterally to upper margin of ear.

Nasals elongate antero-posteriorly, with naris situated posteriorly; separated from rostral by anterior internasal. Postnasals 2/2, subequal in size; lower ones in narrow and broad contact with second and third supralabials, respectively. Canthus rostralis rounded. Canthals 1/1, slightly longer than wide. Loreals 1/1, slightly wider than long, slightly larger than canthals. Cantholoreals 1/1, about as large as canthal and loreal combined, in contact anteriorly with canthal and loreal, posteriorly with first superciliary and upper preocular, and ventrally with fourth and fifth supralabials on left side and fifth supralabial on right side. One roughly triangular scale between cantholoreal, upper preocular, and supralabials on either side. Preoculars 1/1, approximately as wide as long; suboculars 2/2, anterior one slightly longer than wide, posterior one longitudinally elongate; postoculars 3/3. Superciliaries 7/7; first superciliary larger than remaining superciliaries. Supralabials 13/13; last three much larger and higher than anterior ones. Temporal scales in five rows. Primary temporals 4/4, lower primary temporal in contact with 11th and 12th supralabials on either side. Upper secondary and upper tertiary temporals presumably fused into one large scale in dorsal contact with parietal and occipital on either side; 3/3 and 4/4 secondary and tertiary temporals, respectively, extending ventrally from presumably fused upper secondary and upper tertiary temporal scales. Lower secondary and lower tertiary temporals in contact with 12th and 13th and 13th supralabials, respectively, on either side.

Mental approximately 1.5 X wider than long. Infralabials 12/11. Two postmentals. Six pairs of chinshields; those of first pair in broad contact with each other, those of second and third pairs separated by one and two scales, respectively.

External ear opening oval, vertically elongate (maximum width ¼ 0.8 mm, maximum height ¼ 3.0 mm), without lobules or spines. Dorsal scales keeled, imbricate, nearly equal in size to ventrals; in 10 longitudinal rows on neck and 14 rows at level of midbody; in 47 transverse rows from first row of nuchals to last scale row lying at least partially over posterior portion of thighs. Lateral fold well developed. Ventral scales in 40 transverse rows from anterior insertion of forelimbs to vent; in 12 longitudinal rows at level of midbody. Medial pair of precloacal scales nearly twice as large as lateral precloacal scales. Scales on dorsal surface of forelimbs smooth except for some faintly keeled scales on arms; scales on anterodorsal surface of thighs and dorsal surface of shanks smooth. Supradigital scales in one row; subdigital lamellae rounded. Subdigital lamellae on manus I 7/8, II 11/11, III 14/13, IV 16/17, V 11/11. Subdigital lamellae on pes I 8/7, II 12/12, III 15/14, IV 18/18, V 12/12. Hemipenes bifurcate distally.

Color in preservative. —Head, body, limbs, and tail ground color light brown dorsally and laterally, white ventrally. Head immaculate dorsally and laterally except for one dark brown spot on anteroventral corner of lower primary temporal scale on each side, one dark scale on temporal region on right side, and another one on nuchal region on left side. Body with eight dark, dorsal cross-bands; one at level of midneck and seven between levels of anterior insertion of arms and groin; cross-bands heterogeneous; their midsection narrower and paler than lateral sections, composed of two or three often fragmented rows of intermingled white, pale brown, or dark brown scales; their lateral sections wider, overall darker, usually composed of 2– 4 (occasionally 5) short scale rows checkered with white, dark brown, and black scales; cross-bands separated from each other by 2–3 transverse scale rows. Lateral fold white; vertical dark bars indiscernible except for few (<5), barely perceptible, poorly defined bars on each side. Thighs with few, small, irregular dark spots on anterodorsal surface. Tail with four dark, dorsal cross-bands on anterior end; first at level of posterior insertion of legs, remaining ones separated from each other by two scale rows; each cross-band composed of three scale rows checkered with white, pale brown, and dark brown scales; first cross-band conspicuous; remaining ones gradually becoming fainter posteriorly. Ventral surface of head, body, limbs, and tail immaculate white except for some irregular, scattered black flecks on belly.

Variation. —This section is based on all of the paratypes. Multistate characters: Postrostral separated from posterior internasal by supranasal on right side in MZFC 29660; separated from posterior internasals by one tiny scale in MZFC 29660. Supranasal divided on right side in MZFC 26667. Cantholoreal absent on both sides in four specimens, absent on left side in MZFC 29664. Upper primary temporal in contact with first supraocular on left side in MZFC 29665. Meristic characters: Canthals 1–3, ¯X ¼ 1.5 (1/1 [n ¼ 7], 1/2 [n ¼ 1], 2/1 [n ¼ 1], 2/2 [n ¼ 5], 3/2 [n ¼ 1]); loreals 1–3, ¯X ¼ 1.5 (1/1 [n ¼ 3], 2/2 [n ¼ 9], 3/2 [n ¼ 1], 3/3 [n ¼ 2]); superciliaries 6–8, ¯X ¼ 6.5 (6/6 [n ¼ 5], 6/7 [n ¼ 3], 7/6 [n ¼ 2], 7/7 [n ¼ 4], 8/7 [n ¼ 1]); supralabials 12–13, ¯X ¼ 12.7 (12/ 12 [n ¼ 1], 12/13 [n ¼ 3], 13/12 [n ¼ 4], 13/13 [n ¼ 7]); preoculars 1–2, ¯X ¼ 1.1 (1/1 [n ¼ 13], 1/2 [n ¼ 1], 2/2 [n ¼ 1]); suboculars 1–3, ¯X ¼ 2.1 (1/2 [n ¼ 1], 2/2 [n ¼ 10], 2/3 [n ¼ 4]); postoculars 3–4, ¯X ¼ 3.1 (3/3 [n ¼ 12], 3/4 [n ¼ 2], 4/4 [n ¼ 1]); primary temporals 4–5, ¯X ¼ 4.2 (4/4 [n ¼ 10], 4/5 [n ¼ 3], 5/4 [n ¼ 2]); secondary temporals 3–4, ¯X ¼ 3.1 (3/3 [n ¼ 13], 3/4 [n ¼ 2]). Longitudinal dorsal scale rows 16 in all specimens; transverse dorsal scale rows 45–49, ¯X ¼ 47.1; lamellae under fourth toe 17–21, ¯X ¼ 18.9 (17/18 [n ¼ 2]; 17/ 19 [n ¼ 1]; 18/19 [n ¼ 3]; 18/20 [n ¼ 4]; 19/19 [n ¼ 1]; 19/20 [n ¼ 1]; 19/21 [n ¼ 1]; 20/20 [n ¼ 1]; 21/21 [n ¼ 1]).

Color pattern (in preservative). — This section is based on all of the paratypes unless noted otherwise. The head, body, limbs, and tail ground color was pale to medium brown on the dorsal and lateral surfaces. A dark brown mark on the side of the head was present in all of the specimens (n ¼ 14; MZFC 29656 damaged); however, it was highly variable in distinctness and extent. Usually, the mark consisted of a dark brown spot on the anteroventral corner of the lower primary temporal (gradually becoming diffuse on the rest of the scale) that extended anteriorly through the lower postocular, then narrowed into a thin line along the dorsal margin of the suboculars, and broadened again into a diffuse splotch on the upper portion of the preocular. The mark was usually evident on the lower primary temporal and lower postocular, but became barely perceptible on the dorsal margin of the suboculars and upper portion of the preocular in most of the specimens. The mark further extended to the cantholoreal in three specimens ( MZFC 29655 , 29662 , and 29664), to the lower secondary temporal in MZFC 29668 , to the cantholoreal and the dorsal margin of the supralabials adjacent to the lower primary temporal in MZFC 29661 , and (if faintly) to the cantholoreal and the middle of the lower secondary temporal in MZFC 29666 . In addition, the mark was barely discernible on the lower postocular on the left side in MZFC 29667 , absent on the lower postocular on the right side in MZFC 29669 , absent on the lower primary temporal on the left side in MZFC 29657 , and absent on the lower primary temporal on the right side in MZFC 29663 . A small, dark brown spot was present on the posterodorsal corner of the temporal region in 10 specimens ( MZFC 29658–63 [absent on left side in MZFC 29663 ] and MZFC 29665–68 ) .

Dorsal cross-bands 7–9 (¯X ¼ 8.1). Most or all of the crossbands were continuous across the dorsum (their mid portion composed of 2–3 scale rows checkered with pale and dark brown scales, often flecked with white) in three specimens ( MZFC 29667–69 ); there were no, or only few (usually 2–3, occasionally 4 or 5), cross-bands discernible across the dorsum (their mid portion usually composed of a single row of pale brown scales, thus rendering the middorsum distinctly paler than the flanks) in the remaining specimens. The chest and venter exhibited from few to numerous scattered black flecks (faint in MZFC 29655 ) .

Etymology. —The species epithet is a noun in the genitive case and a patronym for the late Clarence Jack McCoy in recognition of his many and significant contributions to the knowledge of the amphibians and reptiles from the Cuatro Ciénegas Basin.

Distribution and ecology. — Gerrhonotus mccoŋi sp. nov. is known only from the shores of several small lagoons in the Cuatro Ciénegas Basin, Coahuila ( Fig. 3 ). The vegetation on the Cuatro Ciénegas Basin was described by Pinkava (1979, 1984) as composed of grasslands, sedges, and marshes, gypsum dune assemblages, desert scrub, and chaparral. The climate at the type locality is temperate (mean annual temperature ¼ 21.4°C; mean temperatures of the coldest and warmest months are 12°C and 28°C, respectively) and arid, with annual seasonal precipitation averaging <200 mm, and a rainy season that extends from May through December (Instituto Nacional de Estadística, Geografía e Informática [INEGI] 1994). All specimens of this species were collected at night, when most of them were active on the vegetation around the pools at heights of up to 2 m ( Fig. 4a ). The activity of this species appears to be restricted to the period of the summer with the highest precipitation (between June and September).

Conservation. —The conservation status of the CCB lagoons has long been a matter of concern (i.e., Pinkava 1987; Breunig 2006). Currently, the Basin is considered the continent̕s second-smallest freshwater ecoregion (492 km 2). Because of its large number of unique (endemic) organisms and the imminent threats to their existence, it is classified, along with only 11 of North America̕s 76 freshwater ecoregions, in the First Priority class for conservation action by the World Wildlife Fund ( Abell et al. 2000). Agricultural development and associated water extraction in the region have placed pressure on the ecological integrity of this unique ecosystem ( Souza et al. 2006). Water extraction has significantly reduced the amount of habitat available for the endemic species of amphibians and reptiles that are closely associated with the humid zones in the Basin ( McCoy 1984), which has reduced their distribution within the Basin ( García-Vázquez et al. 2010). Unless urgent conservation strategies are implemented to regulate water extraction in the CCB, many species in the Basin could disappear.

Figures

FIG. 1.—Gerrhonotus mccoŋi sp. nov. holotype (MZFC 29654). Head scales in dorsal (top), left lateral (middle; intentionally mirrored), and ventral (bottom) views. Scale bars ¼ 3 mm.

FIG. 2.—Gerrhonothus mccoŋi sp. nov. in life. (A) Male (paratype, MZFC 29668). (B) Female, not collected. Photographs by UOG-V and P. Heimes, respectively. A color version of this figure is available online.

FIG. 3.—Collecting localities of Gerrhonotus mccoŋi and other species of Gerrhonotus distributed in central Coahuila, México (inset). White line represents state boundaries.

FIG. 4.—Habitat and color pattern in life of species of Gerrhonotus in the Cuatro Ciénegas region, México. (A) G. mccoŋi sp. nov. (B) G. infernalis. (C) G. lugoi. Photographs of habitats and specimen of G. infernalis by UOG-V; those of specimens of G. mccoŋi sp. nov. and G. lugoi by P. Heimes and J. Jones, respectively. A color version of this figure is available online.

Tables

TABLE 1.—Variation in selected morphometric characters in the type series of Gerrhonotus mccoŋi sp. nov., including the holotype (n ¼ 16). SVL ¼ snout–vent length; HW ¼ head width; HL ¼ head length; EW ¼ ear width; FL ¼ forelimb length; HIL ¼ hind limb length; TI ¼ tibia length; DL ¼ fourth toe length; TL ¼ trunk length; T ¼ tail length; SE ¼ standard error. * ¼ Holotype.

Trait
Specimen	Sex	Age	SVL	HW	HL	EW	FL	HIL	TI	DL	TL	T