Acanthosaura aurantiacrista

Molecular analyses

Molecular comparisons of 698 nucleotides of the ND2 gene revealed differences of 0-1.2% amongst seven specimens of Acanthosaura aurantiacrista sp. n. (GenBank MH777406, MK798128, MK798129, MK798130, MK798131, MK798132 and MK798133) (Table 2). The ND2 gene sequences of the seven specimens of A. aurantiacrista sp. n. showed differences of 10.9-14.5% compared to eight specimens of A. crucigera (GenBank GU817389, HM143889, MH777402, MH777403, MH777404, MH777405, MH777407 and MH777408); differences of 13.8-15.0% compared to two specimens of A. cardamomensis (GenBank GU817397 and GU817400); differences of 16.2-16.3% compared to two specimens of A. armata (GenBank AB266452 and NC014175); differences of 18.0-19.6% compared to two specimens of A. lepidogaster (GenBank AF128499 and KR092427); and differences of 19.1-19.8% compared to a specimen of A. capra (GenBank AF128498) (Table 4). The phylogenetic relationships within the genus Acanthosaura revealed through Maximum-Likelihood trees and Bayesian Inference tree of the ND2 gene showed high posterior probabilities and high bootstrap support values (Fig. 1). The A. aurantiacrista sp. n. lineage was sister to the A. crucigera and A. cardamomensis lineage and warrants separate species recognition.

Mophological comparison

Acanthosaura aurantiacrista sp. n. differs from A. armata in presenting fewer INFRAL (9-11 vs. 12-15), more FI (17-23 vs. 13-17), more TO (25-29 vs. 19-26), fewer NS (5-6 vs. 6-10), fewer NCS (11-13 vs. 10-17) and the presence of a BEP and more GP (1-4 vs. 1) (Suppl. material 1).

Acanthosaura aurantiacrista sp. n. differs from A. bintangensis in presenting greater TaL/SVL ratio (1.40-1.70 vs. 1.30-1.40), greater PS/HL ratio (0.24-0.84 vs. 0.07-0.19), greater DS/HL ratio (0.15-0.38 vs. 0.08-0.09), fewer DIASN (8-9 vs. 11-15), more VENT (63-66 vs. 51-55), fewer NSSOS (5 vs. 6-7), fewer NS (5-6 vs. 8) and the presence of a LKP.

Acanthosaura aurantiacrista sp. n. differs from A. brachypoda in presenting greater PS/HL ratio (0.24-0.84 vs. 0.11), greater DS/HL ratio (0.15-0.38 vs. 0.06), fewer RS (4-6 vs. 5-9), fewer NS (5-6 vs. 9) and more GP (1-4 vs. 0).

Acanthosaura aurantiacrista sp. n. differs from A. capra in presenting fewer INFRAL (9-11 vs. 12-13), more FI (17-23 vs. 16-17), more TO (25-29 vs. 22-24), fewer NS (5-6 vs. 9) and the presence of an occipital spine and scales surrounding the occipital spine.

Acanthosaura aurantiacrista sp. n. differs from A. cardamomensis in presenting fewer RS (4-6 vs. 7-9), fewer NS (5-6 vs. 7-10) and fewer NSSLC (9-13 vs. 10-19).

Acanthosaura aurantiacrista sp. n. differs from A. coronata in presenting greater TaL/SVL ratio (1.40-1.70 vs. 0.60-1.00), more FI (17-23 vs. 13-14), more TO (25-29 vs. 17-19), fewer RS (4-6 vs. 9), fewer NS (5-6 vs. 7-9), fewer NR (1-2 vs. 3-4) and the presence of a postorbital spine, nuchal spine, dorsal spine, diastema, occipital spine, YAS, ND, BEP and more GP (1-4 vs. 0).

Acanthosaura aurantiacrista sp. n. differs from A. crucigera in presenting fewer DIASN (8-9 vs. 9-25), more VENT (63-66 vs. 55-63), more FI (17-23 vs. 16-18), more TO (25-29 vs. 21-26), fewer RS (4-6 vs. 7-8), fewer NS (5-6 vs. 7-9) and more GP (1-4 vs. 1-2).

Acanthosaura aurantiacrista sp. n. differs from A. lepidogaster in presenting greater TaL/SVL ratio (1.40-1.70 vs. 1.00-1.50), greater PS/HL ratio (0.24-0.84 vs. 0.06-0.17), greater NSL/HL ratio (0.35-0.95 vs. 0.12-0.15), greater DS/HL ratio (0.15-0.38 vs. 0.06-0.15), fewer DIASN (8-9 vs. 10-14), more VENT (63-66 vs. 52-61), more TO (25-29 vs. 22-23), greater OS/HL ratio (0.19-0.44 vs. 0.14-0.15), fewer NS (5-6 vs. 7-8), fewer PM (4 vs. 5), absence of scale on tympanum and more GP (1-4 vs. 0-1).

Acanthosaura aurantiacrista sp. n. differs from A. murphyi in presenting greater PS/HL ratio (0.24-0.84 vs. 0.16-0.34), greater NSL/HL ratio (0.35-0.95 vs. 0.24-0.43), fewer INFRAL (9-11 vs. 12-14), more FI (17-23 vs. 15-18), more TO (25-29 vs. 21-23), fewer RS (4-6 vs. 8-9), fewer NS (5-6 vs. 7-8), fewer NR (1-2 vs. 3-4) and the absence of a tympanum scale.

Acanthosaura aurantiacrista sp. n. differs from A. nataliae in presenting fewer VENT (63-66 vs. 64-71), fewer RS (4-6 vs. 7), fewer NSSLC (9-13 vs. 13-16) and the presence of an occipital spine, scales surrounding the occipital spine, ND and LKP.

Acanthosaura aurantiacrista sp. n. differs from A. phongdienensis in presenting greater PS/HL ratio (0.24-0.84 vs. 0.06-0.09), greater NSL/HL ratio (0.35-0.95 vs. 0.07-0.18), larger DS/HL ratio (0.15-0.38 vs. 0.03-0.07), more FI (17-23 vs. 14-17), more TO (25-29 vs. 19-23) and the presence of a diastema.

Acanthosaura aurantiacrista sp. n. differs from A. phuketensis in presenting greater NSL/HL ratio (0.35-0.95 vs. 0.21-0.39), fewer DIASN (8-9 vs. 12-17), more FI (17-23 vs. 15-17), more TO (25-29 vs. 21-24), fewer RS (4-6 vs. 5-9), fewer NS (5-6 vs. 7-8) and more GP (1-4 vs. 1-2).

Acanthosaura aurantiacrista sp. n. differs from A. titiwangsaensis in presenting greater PS/HL ratio (0.24-0.84 vs. 0.14-0.18), greater NSL/HL ratio (0.35-0.95 vs. 0.11-0.18), greater DS/HL ratio (0.15-0.38 vs. 0.07-0.09), fewer DIASN (8-9 vs. 10-13), more VENT (63-66 vs. 47-57), fewer NS (5-6 vs. 8) and the presence of a LKP.

Acanthosaura aurantiacrista sp. n. differs from A. tongbiguanensis in presenting greater PS/HL ratio (0.24-0.84 vs. 0.13-0.19), greater NSL/HL ratio (0.35-0.95 vs. 0.15-0.21), greater OS/HL ratio (0.19-0.44 vs. 0.16-0.23), fewer RS (4-6 vs. 6-9), fewer NS (5-6 vs. 8-9) and more GP (1-4 vs. 1-2).

Diagnosis

Acanthosaura aurantiacrista sp. n. is differentiated from all other congeners by this combination of characters: A large size (maximum SVL 130.1 mm for males and 119.3 mm for females) and a single long conical spine above the posterior margin of the eye; a large spine on the occiput between the tympanum and nuchal crest; tympanum naked, large, roundish; large developed gular pouch; scales on flanks randomly intermixed with small keeled and small tubercle scales; large nuchal crest with 8 large dagger-like and pointed spines; narrow diastema with 8-9 scales between the nuchal and vertebral crests; vertebral crest composed of large dagger-like, pointed spines beginning at the shoulder region and decreasing in size until the base of the tail; nuchal and dorsal crests are orange in females and yellow in males; tail 1.40-1.70 times the SVL; and black collar and black eye patch present, extending posteriorly until reaching the nuchal crest.

Description

Description of the holotype: Adult female. SVL 105.7 mm; TaL 151.8 mm (1.44 times SVL), tail complete; HL (23.3 mm) slightly longer than HW (18.9 mm); HL one-fifth SVL (0.22 times SVL), HW narrow (0.179 times SVL) and HD tall (0.64 times HL); head triangular in dorsal and lateral views; SL moderately long (0.46 times HL); RW wide (2.31 times RH); steeply sloping anteriorly; CS prominent, forming a large projecting shelf extending above eye, composed of 14/13 large scales; shelf terminates with a notch anterior to postorbital spine; rostrum moderate in size, rectangular, bordered laterally by first SUPRALs and posteriorly by five smaller scales; nostrils roundish, surrounded by one prenasal anteriorly, four postnasals posteriorly and two subnasals; six NS; oval supranasals; large scales above orbit weakly keeled; three rows of moderately-keeled scales below orbit extending from the anterior margin of the eye to posterior; large EYE (0.28 times HL) and ORBIT (0.44 times HL); interorbital, prefrontal and frontal scales slightly keeled and smaller than scales below orbit; seven large, keeled, azygous prefrontal scales arranged in a Y-shaped pattern; parietal eyespot surrounded by a larger row of scales; large conical PS above posterior margin of the eye surrounded by five small lanceolate scales; single row of seven large keeled scales extending from suborbital below posterior margin of eye to above tympanic margin, increasing in size posteriorly; elongated conical OS on lateral margin of nape surrounded by a rosette of five small lanceolate NSSOS; tympanum exposed, roundish, with a size two-thirds that of EYE (0.69 times EYE), surrounded by tiny conical scales; thirteen rectangular SUPRALs similar in size; mental pentagonal, larger than adjacent INFRALs; two postmentals similar in size, four scales contacting PM; chin shields large, extending posteriorly to angle of jaw, separated from infralabials by one scale row anteriorly and three at angle of jaw; eleven rectangular INFRALs of similar size; gular scales sharply keeled and spinose with a larger midventral row; extensible dewlap present; nuchal crest composed of eight elongated, dagger-like scales, bordered on each side by two rows of large, flat, keeled, triangular scales; nuchal crest followed by a diastema of nine DIASN at base of nape; dorsal body crest extending from posterior margin of diastema to base of tail; dorsal crest composed of small laterally compressed, triangular epidermal scales, bordered by a row of smaller paravertebral triangular scales; DS slightly decreasing to sacrum, then fading progressively; and nuchal and dorsal crests present as orange in live specimen (Fig. 2).

Body robust, triangular in cross-section; dorsal body scales small, mixed with some large-keeled scales without a regular pattern, keels projecting posteriorly; pectoral and abdominal scales larger than DS; keeled, semi-transverse rows arranged; keeled scales anterior to large vent; limbs relatively long, dorsal forelimb and hindlimb scales keeled and larger than VENT; five digits on manus; subdigital scales keeled, FI 23/21; five digits on pes; subdigital scales keeled, TO 27/26; TaL 1.44 times SVL, tail covered with keeled spinose scales, keels on subcaudals directed posteriorly; subcaudals much longer than supracaudals; TBW 10.3 mm; and four white creamy eggs with a diameter of approximately 10 mm inside the body.

Variation

The female paratypes resemble the holotype in all aspects, and the observed differences were a larger PS (7-10.5 vs. 5.7) and OS (5.3-7.5 vs. 4.5) and greater NSL (9.6-12.7 vs. 8.3), wider WNC (0.9-1.6 vs. 0.6), more SUPRAL (10-11/10 vs. 13/13) and fewer number of FI (18-20/17-20 vs. 23/21), higher number of NSSLC (10 vs. 13) in QSMI1446, QSMI1447, THNHM28521 and THNHM28522, and larger GP (3 vs. 1) in QSMI1446 and THNHM28522. The adult male paratype (QSMI1448) differs from the adult female holotype in presenting a longer SVL (130.1 vs. 105.7), greater TaL (202.2 vs. 151.8) and SL (22.3 vs. 10.7), wider TBW (19.2 vs. 10.3), greater HD (21.7 vs. 14.9), larger ORBIT (8.5 vs. 6.4), longer PS (19.1 vs. 5.7), OS (10 vs. 4.5), greater NSL (21.6 vs. 8.3), FOREL (54.2 vs. 49.8), HINDL (71.4 vs. 59.7) and GP (4 vs. 1) size, wider WNC (2.9 vs. 0.6), narrower DIAS (3.5 vs. 5.4) and fewer number of SUPRAL (10 vs. 13) and FI (19/18 vs. 23/21). Two subadult male paratypes are smaller and present fewer differences in morphological characters compared with the holotype, except for a longer PS (5.5-7.5 vs. 5.7) and OS (5.9 vs. 4.5) in THNHM28523, a greater WNC (0.7-0.8 vs. 0.6) in THNHM28523 and THNHM28524 and higher number of TO (29/29 vs. 27/26) (Fig. 3). Morphometric and meristic data for the type series are shown in Table 3.

Coloration in life

Males – Front of head dark with brownish-yellow colouration on the canthals; lips yellow; black eye patch; lateral head and neck yellow; gular pouch white; postorbital and occipital spines creamy yellow; nuchal crest bright yellow with some orange; dorsal crest orange-yellow; body rusty-brown with some brownish-yellow keeled scales; whitish-yellow ocellated spot at the knee and elbow; ventral creamy white with some dark spots or dirty brown colouration on the abdomen with creamy brown colouration on pectoral and forelimbs; forelimbs and hindlimbs dark brown dorsally; tail banded with dark brown and dirty light brown (Fig. 4).

In addition, the hemipenis of QSMI1448 is everted approximately 10 mm from the cloaca opening to the hemipenis tip on each side. The hemipenis on each side diverged to a symmetrical spongy millet shape with a width of approximately 5 mm. In preserved ethanol, the hemipenes exhibited a creamy yellow colouration.

Females - Front of head whitish-yellow or creamy white; lips orange-yellow; black eye patch; lateral head and neck yellow intermixed with orange; gular pouch white or yellow intermixed with white; postorbital and occipital spines creamy yellow; nuchal crest yellowish-orange or reddish-orange; dorsal crest reddish-orange; body with brownish-grey or rusty-grey marbled reticulum with some grey keeled scales; whitish or whitish-yellow ocellated spot at the knee and elbow, with certain others indicated on the forelimbs and hindlimbs; ventral creamy white or creamy yellow intermixed with some dark brown on the abdomen, ventral region of forelimbs and hindlimbs; forelimbs and hindlimbs brownish-grey dorsally; tail banded with dark brown and dirty light brown.

Etymology

The specific epithet aurantiacrista came from a combination of the Latin words aurantiaco (orange) and crista (crest). The name refers to a distinctive characteristic of the first discovered female specimen, which exhibited nuchal and dorsal crests with an orange colour. We suggest the following common names: kingkakhaownaam seesom (Thai), orange crested horned lizard (English), orange-verzierter gehörnter Nackenstachler (German) and Acanthosaurus à crête orange (French).

Distribution

Acanthosaura aurantiacrista sp. n. occurs in the Thanon Thong Chai Mountain Range in northern Thailand: Mae Sariang District, Mae Hong Son Province (18°14'54.8"N, 97°98'38.2"E) at 728 m a.s.l.; Sop Khong Subdistrict, Omkoi District, Chiang Mai Province (17°63'55.4"N, 98°18'15.6"E) at 935 m a.s.l.; and Nang Lae Subdistrict, Mueang District, Chiang Rai Province (20°02'35.3"N, 99°54'12.1"E) at 636 m a.s.l. This species usually lives in rainforests on mountains at elevations over 600 m a.s.l. (Fig. 5).

Ecology

Acanthosaura aurantiacrista sp. n. has been found in evergreen forests on hills up to at least 600 m elevation (Fig. 6). It is active during the day on the ground, logs or rocks or 1-2 m above the ground on trees. During night, it is inactive and sleeps on twigs or trees 1-2 m above the ground. This species displays a defence mechanism against approach or provocation consisting of falling to the ground and running away to find refuge under rocks, log hollows or shrubs.