Marisora syntoma, Mccranie & Matthews & Hedges, 2020

Mccranie, James R., Matthews, Amy J. & Hedges, S. Blair, 2020, A morphological and molecular revision of lizards of the genus Marisora Hedges & Conn (Squamata: Mabuyidae) from Central America and Mexico, with descriptions of four new species, Zootaxa 4763 (3), pp. 301-353 : 322-325

Marisora syntoma sp. nov.

Tehuantepec Skink

Fig. 8

Mabuia agilis : Günther 1885:33 (in part); Gadow 1905:195 (in part).

Mabuya mabouya mabouya : Hartweg & Oliver 1940:17; Smith & Langebartel 1949:410; Smith & Taylor 1950:156 (in part).

Mabuya mabouya alliacea : Burger 1952:186 (in part); Chrapliwy & Fugler 1955:125.

Mabuya brachypoda : Webb 1958:1304 (in part); Holman 1964:49.

Mabuya unimarginata : Miralles et al. 2009b:602 (in part; tissue sample only); Miralles & Carranza 2010:861 (in part; tissue sample only).

Marisora brachypoda : Hedges & Conn 2012:244 (in part); Lara-Resendiz et al. 2017:226 (in part; spot locality map).

Mabuya unimarginata complex: Pinto-Sánchez et al. 2015:204 (in part; by implication only, no specimens examined).

Holotype. USNM 113677 , an adult male from Tehuantepec , Oaxaca, Mexico, 16°19’21.72”N, 95°14’32.39”W, 35 m elevation, collected by Hobart M. Smith, 4 January 1940.

Paratypes (14). MEXICO— Oaxaca: USNM 113679–80, 113685, adult males, USNM 113681–83, 113692, 113694, adult females, all from the type locality; USNM 46684, adult male, from Santa Efigenia; USNM 113701, 113705, adult males, USNM 113702–03, 113707, adult females, all from Tres Cruces ( NW of Tehuantepec).

Referred specimens (23; all examined). MEXICO. Chiapas: USNM 113666 , Cruz de Piedra; USNM 47138 , Ocozocoautla de la Espinosa; USNM 192534 , between Tonala and Arriacaga. Oaxaca: KU 33804 , 12 miles S, 5 miles E of Nejapa de Madero; USNM 113678 , 113684 , 113686–91 , 113693 , 113695–700 , Tehuantepec (type locality); USNM 113708–09 , Tenango; USNM 113704 , 113706 , Tres Cruces ( NW of Tehuantepec ).

Diagnosis. Marisora syntoma sp. nov. is a relatively small species of Marisora characterized (data from 7 males, 8 females in type series) by (1) maximum known SVL in males 68.5 mm; (2) maximum known SVL in females 75.0 mm; (3) SW 3.0–4.6% SVL in males, 3.0–4.6% in females; (4) HL 19.3–22.0% SVL in males, 16.3– 21.8% in females; (5) HW 10.4–13.1% SVL in males, 10.1–13.1% in females; (6) EAL 0.8–2.0% SVL in males, 0.7–1.9% SVL in females; (7) Toe IV length 8.7–10.4% SVL in males, 7.4–11.4% in females; (8) prefrontals one per side; (9) supraoculars four per side; (10) supraciliaries four per side in 96.7%, five in 3.3%; (11) frontoparietals one per side; (12) fifth supralabial below orbit; (13) nuchal rows one per side; (14) dorsals 53–57 (55.6 ± 1.5) in males, 53–58 (55.4 ± 1.8) in females; (15) ventrals 56–60 (57.4 ± 2.3) in males, 57–63 (59.8 ± 2.0) in females; (16) dorsals + ventrals 108–117 (113.0 ± 3.4) in males, 113–119 (115.1 ± 2.5) in females; (17) midbody scale rows 28 in 80.0%, 26 in 13.3%, 27 in 6.7%; (18) Finger IV lamellae 9–12 (10.4 ± 1.0) per side in males, 9–13 (10.6 ± 1.6) in females; (19) Toe IV lamellae 12–14 (13.3 ± 0.8) per side in males, 13–14 (13.5 ± 0.5) in females; (20) Finger IV + Toe IV lamellae 22–26 (23.7 ± 1.4) on one side in males, 22–27 (24.1 ± 1.8) in females; (21) supranasals in medial contact in 66.7%, not in medial contact in 33.3%, thus frontonasal in contact with rostral in 33.3%; (22) prefrontals almost always not in contact (93.3%), but point contact made in 6.7%; (23) supraocular 1-frontal contact absent in 86.6%, contact made in 6.7%, point contact made in 6.7%; (24) parietals in contact posterior to interparietal; (25) pale middorsal stripe absent; (26) dark dorsolateral stripe absent and a pale dorsolateral stripe at best indistinct; (27) dark brown lateral stripe present; (28) distinct pale lateral stripe present; (29) palms and soles pale brown or cream; (30) total lamellae for five fingers 37–44 (40.0 ± 2.4) in males, 39–46 (41.4 ± 2.3) in females; (31) total lamellae for five toes 41–56 (48.0 ± 4.4) in males, 42–54 (49.5 ± 4.4) in females. In addition, this is a short-limbed species with a FLL + HLL/SVL 47.8–58.3% in males, 42.3–54.3% in females, and has two chinshields contacting infralabials ( Table 3 ).

Marisora syntoma sp. nov. is a member of the M. alliacea group and is most closely related to M. urtica sp. nov. ( Fig. 3 ). Marisora syntoma differs from all other Mexican and Central American species of Marisora , except M. aquilonaria , in being a smaller species with a maximum known SVL of 68.5 mm in males and 75.0 mm in females (versus 77.0 mm in males of M. urtica [female M. urtica unknown], 81.0 mm in males and 89.0 mm in females of M. brachypoda ), 80.9 mm in males and 92.5 mm in females of M. lineola , 76.1 mm in males and 90.2 in females of M. roatanae , 85.7 mm in males and 95.1 mm in females of M. magnacornae , 79.0 mm in males and 90.3 mm in females of M. alliacea , and 84.0 mm in males and 90.3 mm in females of M. unimarginta ). Marisora syntoma differs further from M. urtica in having two chinshields contacting infralabials (versus one chinshield contacting an infralabial in M. urtica ) and in lacking brown dorsal lines (versus 2–3 fairly distinct to indistinct brown dorsal lines, especially anteriorly, in M. urtica ). Marisora syntoma differs further from M. magnacornae in having shorter limbs (FLL + HLL/SVL 47.8–58.3% in males and 42.3–54.3% in females versus 60.8–68.7% in males and 55.8–68.0% in females of M. magnacornae ) and in lacking distinct dorsolateral stripes (versus pale and dark dorsolateral stripes normally present in M. magnacornae ). Marisora syntoma is further distinguished from M. alliacea in having shorter limbs (FLL + HLL/SVL 47.8–58.3% in males and 42.3–54.3% in females versus 62.5–74.6% and 58.0–67.6%, respectively in M. alliacea ), in lacking distinct dorsolateral and dorsal stripes (versus pale and dark dorsolateral stripes and dark brown dorsal stripes present in M. alliacea ), and in having pale brown to cream palms and soles (versus palms and soles dark brown to black in M. alliacea ). Marisora syntoma can be distinguished from M. aquilonaria by having 4 supraciliaries per side in 96.7% (versus 5 supraciliaries in 81.3% in M. aquilonaria ) and having 22–26, x = 23.7 ± 1.4 combined Finger IV and Toe IV lamellae per side in males and 22–27, x = 24.1 ± 1.8 in females (versus 26–29, x = 27.1 ± 1.0 in males and 25–30, x = 26.3 ± 1.6 in females in M. aquilonaria ). Marisora syntoma is further distinguished from M. brachypoda by having 28 scales around midbody in 80.0% or 26–27 in 20% versus 28 scales around midbody in 35.7%, 30 in 35.7%, or 29 or 31–32 in remainder in M. brachypoda ). Marisora syntoma is further distinguished from M. lineola by lacking dark brown dorsolateral stripes or dashes and having 56–60, 57.4 ± 2.3 ventrals in males (versus those stripes or dashes present and male ventrals 61–69, 63.9, ± 2.6 in M. lineola ). Marisora syntoma also differs from M. roatanae in having pale palms and soles and 26–28 scales around midbody with 28 in 80% (versus distinct dark brown to nearly black soles and palms almost always present and 30–32 scales around midbody in 76.7% and 28 in only 17.9% in M. roatanae ). Marisora syntoma differs from the extralimital M. pergravis by having fewer ventrals (56–63 in both sexes combined versus 70–73 in M. pergravis ), fewer dorsals (53–58 versus 62–63 in M. pergravis ). Marisora syntoma has sometimes been confused with M. unimarginata of the M. unimarginata group, but in addition to the size differences discussed above, differs in lacking distinct dark dorsal spots (versus distinct dark dorsal spots present in M. unimarginata ) and having the fifth supralabial below the orbit (versus sixth in 81.9% in M. unimarginata ). Marisora syntoma is known to differ from the extralimital and poorly known M. berengerae (incomplete morphological data available from the literature only from the unsexed holotype) of the M. unimarginata group only from genetic data; furthermore a huge geographical hiatus inhabited by other species of Marisora occurs between those two species.

Description of the Holotype. An adult male ( Fig. 8 ) in a good state of preservation with a SVL of 55.0 mm; TAL 91.5 mm; HL 12.1 mm; HW 6.2 mm; SW 2.2 mm; EAL 0.5 mm; ear opening nearly oval; Toe IV length 7.6 mm; toe lengths in descending order I<V<II<III<IV.

Head scalation. Rostral wider than high, contacting first supralabial, anterior nasal, and supranasals. Paired supranasals making point contact medially, thus preventing frontonasal-rostral contact, supranasals also contacting upper edge of anteriormost loreal. Frontonasal decagonal, wider than long, laterally in contact with anterior loreal. A pair of pentagonal prefrontals, separated medially, and in contact with frontonasal, anterior and posterior loreals, first supraciliary, frontal, and first supraocular. Frontal heptagonal, in contact with first and point contact with second supraocular, with frontonasal, and with paired frontoparietals. Frontoparietals also in contact with supraoculars 2–4 and with parietals and interparietal. Interparietal tetragonal and lanceolate, separated from nuchals by parietals. Parietal eye not visible externally. Parietals in contact with upper primary, secondary and tertiary temporal scales. Four supraoculars per side, second one largest. Four supraciliaries per side, second longest. Nostril in medial part of nasal, forming nasal division. Postnasal bordered by frontonasal, supranasal, anterior loreal, and first supralabial. Anterior and posterior loreals squarish. One upper preocular and one lower preocular. Seven supralabials, fifth widest and located below orbit. Three small postoculars, considerably smaller than temporal scales. Two primary temporals, two secondary temporals, and two tertiary temporal scales. All temporal scales imbricate, smooth, cycloid, not distinctly delineated from nape scales. Eight infralabials. Mental scale wider than long, posterior margin straight. Postmental and two chinshields per side in contact with infralabials. Chinshields paired, both anterior and posterior in medial contact.

Body and limb scalation. One row of a single enlarged nuchal scale per side, in contact medially (left nuchal scale damaged). Other scales on nape similar in size and shape to dorsals. Lateral neck scales slightly smaller than dorsolateral nape scales. Dorsal scales cycloid, imbricate, smooth, 57 in a longitudinal row. Axillary pit absent, but tiny scales present in that region. Ventral scales similar in size and shape to dorsals, 60 in a longitudinal row. Twenty-six scales around midbody. No distinct boundaries between dorsals, laterals, and ventrals. Scales on base of tail and limbs similar in shape to dorsals, but smaller on limbs. Palmar and plantar surfaces with small, slightly conical scales, subequal in size, and delineated by a surrounding region of slightly larger, flat scales. Subdigital lamellae smooth, single, 11 on Finger IV, 14 on Toe IV. Preanal scales slightly larger than ventrals. No enlarged median subcaudal scales.

Pattern and coloration in preservative. Dorsal ground color pale brown with scattered indistinct brown spots less than one scale in size. Pale and dark dorsolateral stripes absent. Dark lateral stripe rather indistinct. A single, thin (ca. 1/2 scale row high), cream lateral stripe present per side, extending from rostral onto anterior portion of tail, not passing along upper edge of hind limb, passing across lower half of ear opening and with an equal height below ear opening. Lateral cream stripe bordered below by a thin (1/3 scale high) darker brown line. A few indistinct dark brown spots present on medium brown dorsal surfaces of limbs. Ventral surfaces pale brown, without darker scale edges. Palmer and plantar surfaces pale brown, similar color as adjacent undersides of limbs and adjacent lamellae.

Variation. Little color and pattern variation in preservative was noticed among the paratypes other than the thin dark brown ventrolateral line below the pale lateral stripe can be indistinct or absent. Variation in some important morphometric and meristic characters is presented in Table 3 .

Distribution. Marisora syntoma is known to occur on the Pacific versant from southeastern Oaxaca just to the west of the Isthmus of Tehuantepec to west-central and southwestern Chiapas, Mexico ( Fig. 6 ). Its known elevational range is from about 30 m to at least 1100 m.

Ecology and conservation. Nothing has been published on the habitats of skinks that we call Marisora syntoma , other than the brief notes provided by Gadow (1905) that might pertain to this species (see M. aquilonaria section). No conservation information has been published pertaining to this species, but as noted above, species of Marisora generally adapt well to human presence. Thus, M. syntoma is considered a species of little or no conservation concern (although see comments in account of M. lineola regarding the susceptibility of mabuyid skinks to invasive predators).

Reproduction. Nothing has been published on reproduction in Marisora syntoma , but the species is certainly viviparous as are other species in the genus.

Etymology. The specific name syntoma , a noun in apposition, is taken from the Greek syntomos, meaning shortened. The name is used in reference to the short limbs found in this species.

Remarks. Our genetic results ( Fig. 3 ) also support Marisora syntoma as a distinct species from all other known Middle American species (also see similar results in Pinto-Sánchez et al. 2015; their monophyletic clade containing RLR1110 through ANMO1045 MX in their tree Cluster 3). Thus, the distinctiveness of M. syntoma was first discov- ered by genetic-only analyses. We were unable to locate voucher specimens for the genetic data, but examination of morphological characters of specimens from the area of the type locality to those sequenced samples further support the genetic results.

Many of the Oaxaca localities for Marisora syntoma were included on a map in Duellman (1960).

Figures

FIGURE 3A. Phylogenetic tree of the genus Marisora from a maximum-likelihood analysis of DNA sequences of three mitochondrial genes (12S rRNA, 16S rRNA, and cyt b) and three nuclear genes (NGFB, R35, and RAG2) in 140 individuals (4,029 bp). A scale bar (2% sequence divergence) is indicated below. The numbers at left of nodes are bootstrap support values. The tree is rooted with Mabuya dominicana. Species delimited using ABGD indicated by black vertical lines at right; samples with horizontal bars missing cytochrome b Figure continues on two pages.

FIGURE 6. Map showing the localities of the Marisora specimens examined for this study. The gray arrow points to island record for M. urtica. Two extralimital species are also indicated: M. berengerae (San Andres, purple arrow) and M. pergravis (Providencia, yellow arrow).

FIGURE 8. Adult male holotype (USNM 113677) of Marisora syntoma (Oaxaca, Mexico) in preservative, SVL 55.0 mm.