Thamnophis ahumadai, Grünwald & Mendoza-Portilla & Grünwald & Montaño-Ruvalcaba & Franz-Chávez & García-Vázquez & Reyes-Velasco, 2024

Grünwald, Christoph I., Mendoza-Portilla, María del Carmen G., Grünwald, André J., Montaño-Ruvalcaba, Carlos, Franz-Chávez, Héctor, García-Vázquez, Uri O. & Reyes-Velasco, Jacobo, 2024, A new species of Thamnophis (Serpentes, Colubridae) from Jalisco, Mexico, with a discussion on the phylogeny, taxonomy, and distribution of snakes related to Thamnophis scalaris, Herpetozoa 37, pp. 157-179 : 157-179

Thamnophis ahumadai sp. nov.

Figs 2 , 4 , 5 , 7 a – e

Proposed standard English name.

Ahumada’s Alpine Garter Snake.

Proposed standard Spanish name.

Culebra Listonada de Montaña de Ahumada.

Type materials.

Holotype (Fig. 2 ). INIRENA 2933 (original field number CIG- 1612). Adult male collected under a log in a marshy meadow near a pond, 2.8 km E of Cumbre de Guadalupe , Municipio de Cuautla, Jalisco, Mexico (20.168991, - 104.684925, 2,353 m asl; datum = WGS 84; Fig. 4 a ), by Christoph I. Grünwald, María del Carmen G. Mendoza-Portilla, Iván Ahumada-Carrillo, and Ginny N. Weatherman on 23 August 2019.

Paratypes (Fig. 3 ). MZFZ 4593 (original field number CIG- 0500) adult male collected under a rock on a hillside above a stream at Cumbre de Guadalupe , Municipio de Talpa de Allende, Jalisco, Mexico (20.168902, - 104.711252, 2,137 m asl; datum = WGS 84) by Christoph I. Grünwald, Héctor Franz-Chávez, André J. Grünwald, Ámbar Lanomy Grünwald, Janelle Morales-Flores, and Karen I. Morales-Flores on 11 July 2015 . MZFZ 4594 (original field number CIG- 1609) adult female collected under trash in a grassy meadow amongst pine forest, 1.5 km N of Cumbre de Guadalupe , Municipio de Talpa de Allende, Jalisco, Mexico (20.186581, - 104.716188, 2,179 m asl; datum = WGS 84 ), by Christoph I. Grünwald, María del Carmen G. Mendoza-Portilla, Iván Ahumada-Carrillo, and Ginny N. Weatherman on 23 August 2019 . INIRENA 2932 and 2934 (original field numbers CIG- 1611 and CIG- 1613) adult male and adult female, respectively, with the same collection data as Holotype . MZFZ 4595 (original field number CIG- 1610) adult male collected under rock in meadow, 4.2 km airline ESE of Cumbre de Guadalupe , Municipio de Tomatlán, Jalisco, Mexico (20.157217, - 104.675059, 2,319 m asl; datum = WGS 84), by Christoph I. Grünwald, María del Carmen G. Mendoza-Portilla, Iván Ahumada-Carrillo, and Ginny N. Weatherman on 23 August 2019 . INIRENA 2935–36 (original field number CIG- 1700–01) 2 adult males, collected under logs at a large pond at 2.5 km SE of Atemajac de Brizuela , Municipio de Atemajac de Brizuela, Jalisco, Mexico (20.1151, - 103.7036, 2,422 m asl; datum = WGS 84; Fig. 4 b ), by Christoph I. Grünwald, André J. Grünwald, and Ámbar Lanomy Grünwald on 21 June 2020 .

Diagnosis.

A relatively small Garter Snake, with a maximum of 565 mm SVL and 705 TotL; head narrow, scarcely wider than neck, with a short muzzle ( INK + PFK = 3.0 mm); tail long in length, 31–36 % of SVL and 23–27 % of TotLin males, 25–26 % of SVL and 20–21 % of TotLin females; internasals wider than long; frontal 2–2.25 times longer than wide; loreal slightly longer than wide; one preocular; 2–4 postoculars; temporals 1 + 2; 7 supralabials, third and fourth entering orbit; 9–10 infralabials, first four in contact with anterior chinshields; anterior chinshields shorter than posterior. Dorsal scales always in 19-17 - 17 rows, strongly keeled except for the outermost row, which is smooth; ventral scales in males 134–142, in females 139–141; subcaudals in males 61–69, in females 54–55; anal scale undivided. Dorsal pattern consists of a pale mid-vertebral stripe restricted to the mid-dorsal row and a pale lateral stripe on second scale row. One or two rows of dark brown or black dorso-lateral spots, usually in one row on the anterior third of the dorsum, then divided into two rows along the remaining posterior two thirds. Ventral coloration dark, pale anteriorly, becoming progressively darker until dark gray or black posteriorly.

Comparisons.

Thamnophis ahumadai can be distinguished from T. scalaris (comparison character traits in parenthesis) by possessing 19-17 - 17 dorsal scale rows (vs. 17-17 - 17); 61–69 subcaudals in males (vs. 69–77, but see below for Querétaro population); a shorter tail length in males, 23–27 % TL / Totl ratio (vs. 26–33 %) and also in females, 20–21 % (vs. 20–25 %); a black nuchal blotch (vs. brown); two rows of dark brown or black dorsal blotches between mid-dorsal and dorso-lateral pale stripes (vs. one row of large brown dorsal blotches); and a dark gray to black ventral coloration on latter two thirds of body (vs. ventral coloration same as darker portions of lateral coloration).

Thamnnophis ahumadai can be distinguished from T. errans ( T. errans character traits in parenthesis) by possessing 134–142 ventral scales in males (vs. 150–166) and 139–141 ventral scales in females (vs. 146–160); 61–69 subcaudals in males (vs. 78–94) and 54–55 subcaudals in females (vs. 67–83); a shorter tail length in females, 20–21 % TL / TotL ratio (vs. 23–25 %); a dorsal pattern with at least some larger dorsal spots fusing together towards the anterior portion of the body (vs. all dorsolateral spots in two alternating rows); and by possessing small black spots on the lateral pale stripe (vs. black spotting absent on lateral pale stripe).

Thamnophis ahumadai can be distinguished from T. godmani ( T. godmani character traits in parenthesis) by possessing 19-17 - 17 dorsal scale rows (vs. 17-17 - 17); 54–69 subcaudals in males (vs. 74–88) and 54–55 subcaudals in females (vs. 61–77); a shorter tail length in males, 23–27 % TL / TotL (vs. 25–29 %), and also in females, 20–21 % (vs. 25–27 %). Thamnophis ahumadai can be distinguished from T. bogerti ( T. bogerti character traits in parenthesis) by possessing 19-17 - 17 dorsal scale rows (vs. 17-17 - 15), 134–142 ventral scales in males (vs. 135–157); 54–55 subcaudal scales in females (vs. 56–68). Moreover, Thamnophis ahumadai is distinguished from both species by possessing two rows of alternating dark brown or black blotches between the mid-dorsal stripe and lateral stripes on dorsum (vs. two rows of dark spots between mid-dorsal stripe and lateral stripe may be absent, limited to randomly occurring black scale outlines, or consist of small black spots).

Thamnophis ahumadai can be distinguished from T. scaliger ( T. scaliger character traits in parenthesis) by possessing supralabials that are all entirely pale-colored, with black pigment along each scale suture (vs. several posterior supralabials darkly pigmented by the encroachment of an occipital blotch, anterior ground color of anterior supralabials pale); 61–69 subcaudal scales in males (vs. 49–58), and 54–55 subcaudal scales in females (vs. 40–49); a longer tail length in males, 23–27 % TL / Totl ratio (vs. 17–21 %) and in females 20–21 % TL / TotL (vs. 16–19 %); no pale coloration along head scale sutures (vs. pale coloration present along head scale sutures); a black nuchal blotch (vs. brown); and two rows of dark brown or black dorsal blotches between the mid-dorsal and dorso-lateral pale stripes (vs. one row of large brown dorsal blotches).

Thamnophis ahumadai can be distinguished from T. exsul ( T. exsul character traits in parenthesis) by possessing 19-17 - 17 dorsal scale rows (vs. 17-17 - 17); 134–142 ventral scales in males (vs. 142–150) and 139–141 ventral scales in females (vs. 152–156); and a pale mid-dorsal stripe always present (vs. absent or only present anteriorly).

Thamnophis ahumadai can be distinguished from both T. mendax and T. sumichrasti by possessing 134–142 ventral scales in males (vs. 145–149 in T. mendax and 151–161 in T. sumichrasti ); from T. sumichrasti by possessing 139–141 ventral scales in females (vs. 147–159) and by possessing 61–69 subcaudals in males (vs. 72–78); from T. mendax by possessing 54–55 subcaudal scales in females (vs. 56–60) and by shorter tail in females 20–21 % TL / TotL (vs. 21–23 %); from both T. mendax and T. sumichrasti by possessing a lateral pale stripe (vs. absent); furthermore T. ahumadai does not present two pattern classes, and can readily distinguished from the blotched pattern class of T. mendax and both pattern classes of T. sumichrasti by possessing a pale mid-dorsal stripe (vs. lacking in both species).

The mountains of central Jalisco have numerous other species of Thamnophis that occur in sympatry or near sympatry with T. ahumadai . These species (except T. copei ) are all distantly related to T. ahumadai and can be readily distinguished by their appearance. Thamnophis ahumadai differs from T. cyrtopsis , T. eques , and T. pulchrilatus by having 17 dorsal scale rows at mid-body (vs. 19 or more) and by having a tongue that is black (vs. red with black tips). From the apparently closely related T. copei (see below), T. ahumadai differs by possessing a loreal (vs. fused with prefrontal), 17 dorsal scale rows (vs. 15), and a longer head with seven supralabials (vs. 5).

For comparative purposes, we include photographs of T. ahumadai and closely related species in Fig. 6 and at a higher resolution in Suppl. material 5.

Description of holotype

(Fig. 2 ). All measurements in mm. An adult male, 357 SVL, 122 TL, 479 TotL, tail relatively long, with TL / SVL ratio 0.34 and TL / TotL ratio 0.25. Head short, twice as long as wide, and HL / SVL 0.04. All dorsal scales keeled except in first lateral row, dorsal scales in 19 rows anteriorly, reducing to 17 at the 21 st ventral scale row and then 17 throughout rest of body. Ventral scales 135, anal scale undivided, 62 / 63 divided subcaudal scales. Rostral wider (3.2) than high (2.3); internasals wider (2.2 / 2.1) than long (1.7); prefrontal subequal, slightly longer (2.7 / 2.6) than wide (2.5 / 2.6); frontal 5.4 long, anterior edge 4.0 from snout; frontal 2.7 wide anteriorly and 2.5 wide posteriorly; parietal longer (6.3 / 6.1) than wide (3.4 / 3.5); loreal slightly longer (1.7 / 1.6) than wide (1.3); seven supralabials on each side and nine infralabials on each side. One preocular on each side and ¾ postoculars. Eye relatively small, ED 3.2, and ED / HL ratio 0.22. Mental wider (2.4) than long (1.25); anterior chin shields (4.8 / 4.3), in contact with 4 infralabials on each side; posterior chin shields longer than anterior chin shields (5.1 / 5.0). For a detailed drawing of the head scalation, see Fig. 5 .

Everted hemipenes are the length of seven subcaudals; they are long and narrow with no noticeable widening in the apical region.

Coloration in preservative

(Fig. 2 b, c ). Head scales brown, but frontal, supraoculars, and parietals pale gray, apparently damaged as the snake was pre-ecdysis. Supralabials cream-white, with black lines along sutures. Dark nuchal blotch 1–3 scales long, black in coloration, complete dorsally from below the labial region on both sides. Pale mid-dorsal stripe white, starting on the fourth dorsal scale posterior to the parietals and running to the tip of the tail. One row of large dorso-lateral blotches, nine on the left, six on the right; large blotches divided into two rows of alternating dorso-lateral blotches. Lateral pale stripe bluish-gray, one second and third scale rows on the neck, and then limited to the second scale row on the rest of body and tail, slowing fading in intensity on tail. A single, lateral row of black spots present on the first dorsal scale row, spots about half a scale in size on the anterior quarter of the body, then reducing to about a third a scale in size on the posterior three quarters of the body. Ventral surfaces of head and throat creamy-white until the fourth ventral scale, becoming pale bluish gray until approximately the 50 th ventral scale, then progressively turning darker until the 78 th ventral scale, where the venter takes on a dark gray-black coloration that continues posteriorly to the tip of the tail.

Coloration in life

(Fig. 2 a ). Dorsal coloration chocolate brown, with 80 pairs of black dorso-lateral blotches present on dorsum. Pale mid-dorsal stripe present, pale yellow on anterior half of body, and then fading to a cream pigment posteriorly until the tail tip. Pale stripe involving only the vertebral row of scales. Top of head brown, including parietals, frontal, supraoculars, prefrontals and internasals, with rostral and front part of internasal pale cream, similar to supralabials. Supralabials pale cream on first three supralabials, then pale yellow on the latter four supralabials. Supralabials 2–6 have a black outline along the upper posterior suture. Nasal cream below, brown above, with a black outline posteriorly. Loreal anterior half cream, posterior half black. Single preocular cream; four postoculars also cream; upper one with black outline on posterior border. Anterior temporal brown above and black below; posterior temporals brown and black. A bilobed dark nuchal spot present behind head, dark brown anteriorly, and black posteriorly. Nuchal spot three scales long at mid-dorsal line, extending ventrally to the height of the jawline. This nuchal blotch partially divides the pale-yellow coloration on the posterior supralabials and the pale lateral stripe on the lower portion of the dorsum. Pale lateral stripe on first three scale rows anteriorly, pale yellow, then restricted to second scale row on the anterior four-fifths of the dorsum, only slightly involving the first and third scale rows. After the anterior fifth of the dorsum, the first scale row is cream with dark black markings on the posterior edge of each scale, giving the appearance of small black vertical blotches. Tail same color as posterior body, black above, cream below, with a pale cream mid-dorsal stripe and small black spots on the cream colored first scale row. Iris copper.

Measurements

(mm). SVL 357; TL 122 mm; TotL; 479; HL 14.; HW 7.3; ED 3.2 mm; RH 2.3; RW 3.2; INL 1.7; INW 2.1; PFL 2.7 / 2.6; PFW 2.5 / 2.6; FL 5.4; MAFW 2.7; MPFW 2.4; PL 6.2 / 6.1; PW 3.4 / 3.5; LL 1.6; LH 1.3; ML 1.25; MW 2.4; ACSL 4.8 / 4.3; PCSL 5.1 / 5.0.

Variation.

Meristic variation is minimal amongst the paratypes. Specimen ranged in size from 255 mm (INIRENA 2935) to 565 mm (INIRENA 2934). The shortest relative tail length was 0.20 TL / TotL in INIRENA 2934, whereas the longest relative tail length was 0.27 in INIRENA 2932. Interestingly, both were males from the same locality. Most all specimens had more ventral scales than the holotype, with MZFZ 4595 possessing the highest count (142). The ventral scale + subcaudal scale combinations amongst specimens ranged from 194 (INIRENA 2934) to 210 / 211 ( MZFZ 4595). No variation in number of dorsal scale rows or supralabials was documented. Two specimens (INIRENA 2934, 2936) had 10 infralabials on both sides. Postoculars usually three on at least one side, but MZFZ 4593 has 4 / 4 and MZFZ 4594 has 4 / 6. The two females (INIRENA 2934, MZFZ 4594) have a head HL / HW ratio of 1.1–1.4, whereas the males have a HL / HW ratio of 1.5–2.0. Color pattern variation exists. The vertebral stripe ranges from orange (INIRENA 2932), yellow or yellowish (INIRENA 2936, MZFZ 4595), to cream ( MZFZ 4593, INIRENA 2935). MZFZ 4593 is unique in that it presents dorsolateral blotches that are fused, similar to T. scalaris and T. scaliger . INIRENA 2934 has a dark dorsal coloration, which makes the dorsal pattern barely visible and gives the snake a dark, unpatterned appearance. Morphological and meristic variation of the all available specimens, including the holotype and all paratypes is given in Table 1 .

Distribution and habitat.

This species appears to be restricted to grasslands and meadows in pine-oak woodland and pine forest above 2100 m asl. Only known from two mountain ranges in Jalisco, the Cumbre de Guadalupe region of the Sierra Cacoma, and in the vicinities of the towns of Atemajac de Brizuela and Juanacatlán in the Sierra de Tapalpa. This species has been collected at elevations ranging from 2140 to 2450 m asl. We have included a range map with known localities of this species and closely related species in Fig. 7 .

Etymology.

A patronym honoring Iván Trinidad Ahumada-Carrillo (1984 –), who has made many contributions to diverse areas in herpetology, including extensive studies of the herpetofauna of Jalisco and Zacatecas. Iván collected the first specimen of this new species in the Sierra Cacoma ( MZFZ 4593) and pointed out its distinctiveness from typical T. scalaris and T. errans .

Conservation.

This species of garter snake is only known from two relatively small high-elevation areas in the highlands of Jalisco, which fall within the “ Jaliscan Transverse Range Pine-Oak Woodland (42) ” and “ Jaliscan Sierra Madre del Sur Mixed Temperate Woodland (46) ” biogeographical formations as mapped by Grünwald et al. (2015). Due to its small distribution, we recommend that this species be rewarded with the highest level of protection possible from the Mexican government. As habitat destruction such as logging and farming is ongoing in both localities where it occurs, this species may qualify as Endangered under the IUCN criterion. However, it can also be considered to be in the DD (data deficient) category due to uncertainties about whether or not this species occurs in Michoacán (see below). More fieldwork should be done to determine the full extent of the distribution of T. ahumadai and whether or not it is present in other highland regions of Jalisco or adjacent Michoacán.

Figures

Figure 2. Thamnophis ahumadai sp. nov. holotype (INIRENA 2933) from the vicinity of Cumbre de Guadalupe, in the Municipio de Cuautla, Jalisco, Mexico.

Figure 3. Thamnophis ahumadai sp. nov. paratypes. A. Male (INIRENA 2932) from same locality as holotype; B. Male (INIRENA 2936) from 2.5 km SE of Atemajac de Brizuela, Municipio de Atemajac de Brizuela, Jalisco, Mexico; C. Male (MZFZ 4595) from 4.2 km airline ESE of Cumbre de Guadalupe, Municipio de Tomatlán, Jalisco, Mexico; D. Male (INIRENA 2935) from 2.5 km SE of Atemajac de Brizuela, Municipio de Atemajac de Brizuela, Jalisco, Mexico; E. Male (MZFZ 4593) from Cumbre de Guadalupe, Municipio de Talpa de Allende, Jalisco, Mexico.

Figure 4. Collection localities for Thamnophis ahumadai sp. nov., including the type locality at 2.8 km E of Cumbre de Guadalupe, Municipio de Cuautla, Jalisco, Mexico (A) and 2.5 km SE of Atemajac de Brizuela, Municipio de Atemajac de Brizuela, Jalisco, Mexico (B).

Figure 5. Head drawings of the holotype of Thamnophis ahumadai sp. nov. (INIRENA 2933). A solid line depicts 1 cm. Drawings by Iván T. Ahumada-Carrillo.

Figure 6. Photographs of species related to Thamnophis ahumadai sp. nov. in life, all from Mexico. Thamnophis ahumadai sp. nov. (A) from Cumbre de Guadalupe, Municipio de Talpa de Allende, Jalisco; Thamnophis ahumadai sp. nov. (B) from 2.8 km E of Cumbre de Guadalupe, Municipio de Cuautla, Jalisco; Thamnophis ahumadai sp. nov. (C) 4.2 km airline ESE of Cumbre de Guadalupe, Municipio de Tomatlán, Jalisco; Thamnophis ahumadai sp. nov. (D) from 2.5 km SE of Atemajac de Brizuela, Municipio de Atemajac de Brizuela, Jalisco; Thamnophis ahumadai sp. nov. (E) from Tapalpa, Municipio de Tapalpa, Jalisco; Thamnophis ahumadai sp. nov. (F) from 2.5 km SE of Atemajac de Brizuela, Municipio de Atemajac de Brizuela, Jalisco; Thamnophis errans (G) from vicinity of Los Amoles, Sierra Huichol, Jalisco; Thamnophis errans (H) from Los Charcos, Municipio de Mezquital, Durango; Thamnophis errans (I) from Los Charcos, Municipio de Mezquital, Durango; Thamnophis errans (J) from 28 km SSW of Tepehuanes, Municipio de Tepehuanes, Durango; Thamnophis errans (K) from La Catedral, Municipio de Guadalupe y Calvo, Chihuhua Thamnophis exsul (L) from Peña Nevada, Nuevo León (photo by Robert Hansen) Thamnophis scalaris (M) from Volcán Chichinautzin, Municipio de Huitzilac, Morelos; Thamnophis scalaris (N) from Villa Victoria, Municipio de Villa Victoria, Estado de México (photo by Hugo Plata-Tinoco); Thamnophis scalaris (O) from Huamantla, Municipio de Huamantla, Tlaxcala (photo by Anibal Díaz de la Vega Pérez); Thamnophis scalaris (P) from Pico de Orizaba, Veracruz (photo by Alfredo Gutiérrez); Thamnophis scalaris (Q) from 1 km N of Pinal de Amoles, Municipio de Pinal de Amoles, Quéretaro; Thamnophis scalaris (R) from 1 km N of Pinal de Amoles, Municipio de Pinal de Amoles, Quéretaro; Thamnophis godmani (S) from San Vicente, Municipio de Chilpancigo de los Bravo, Guerrero; Thamnophis godmani (T) from San Vicente, Municipio de Chilpancigo de los Bravo, Guerrero; Thamnophis bogerti (U) from La Doncella, Municipio de San Mateo Río Hondo, Oaxaca; Thamnophis bogerti (V) from Sierra Miahuatlán, Oaxaca; Thamnophis bogerti (W) from Llano de las Flores, Sierra Juárez, Oaxaca; Thamnophis bogerti (X) from Puerto del Aire, Municipio de Acultzingo, Veracruz.

Figure 7. Distribution map of snakes similar to Thamnophis scalaris in Mexico. Circles represent museum records; squares represent verified iNaturalist observations, or field observations made by us but without a specimen deposited in a collection. The diamond represents the type locality of Thamnophis ahumadai sp. nov. We have included the different populations of Thamnophis bogerti in the key with their former names in quotation marks, and we used different shades of green to depict their individual ranges.