Anomaloglossus megacephalus, Kok, Philippe J. R., Macculloch, Ross D., Lathrop, Amy, Willaert, Bert & Bossuyt, Franky, 2010

Kok, Philippe J. R., Macculloch, Ross D., Lathrop, Amy, Willaert, Bert & Bossuyt, Franky, 2010, A new species of Anomaloglossus (Anura: Aromobatidae) from the Pakaraima Mountains of Guyana, Zootaxa 2660, pp. 18-32 : 20-26

Anomaloglossus megacephalus sp. nov.

( Figs. 1–4 ; Table 1 )

Anomaloglossus tepuyensis ( La Marca, 1998) in part; Grant et al. (2006: 120, 158)

Anomaloglossus tepuyensis (La Marca, 1997 [sic]); MacCulloch & Lathrop (2009: 11, figs. 5–6, plate B)

Holotype. IRSNB 1986 (field number PK 1881), an adult female collected by Philippe J. R. Kok, Paul Benjamin and Claudius Perry, 20 November 2007 at 16h30, eastern base of Mount Maringma, Cuyuni- Mazaruni District, Guyana (05° 12’ 37”N, 060° 33’ 59”W, 1060 m elevation).

Paratypes. ROM 39637-38, adult females collected by Amy Lathrop and Carter Cox, 28 October 2000, northeastern plateau of Mount Ayanganna, Cuyuni-Mazaruni District, Guyana (05° 24’ N, 59° 57’ W, 1490 m elevation).

Etymology. The specific epithet is a combination of mega (Greek meaning "large") and cephalus (Greek meaning “head”), which refers to the large head of the species and is used as a noun in apposition.

Adult definition and diagnosis. (1) large-sized Anomaloglossus (male unknown, female 27.3–28.3 mm SVL); (2) body robust, but relatively more slender than most known congeners, head large; (3) skin on dorsum smooth to granular, more tuberculate posteriorly, skin on venter smooth to slightly granular; (4) Finger I subequal or shorter than II; (5) tip of Finger IV surpassing the base of the distal subarticular tubercle on Finger III when fingers adpressed; (6) distal tubercle on Finger IV present; (7) condition of Finger III in males unknown; (8) fingers with keel-like lateral folds (sensu Myers & Donnelly 2008), best developed preaxially on Fingers II and III; (9) toes moderately webbed, with well-developed folded flaplike fringing (sensu Myers & Donnelly 2008); (10) tarsal keel well-defined, weakly curved, slightly tuberclelike; (11) presence of black arm gland in males (sensu Grant & Castro-Herrera 1998, see also Grant et al. 2006) unknown; (12) symmetrical cloacal tubercles present; (13) pale paracloacal mark present; (14) dorsolateral stripe absent in female (condition unknown in males); (15) ventrolateral stripe present, inconspicuous; (16) oblique lateral stripe present, broken in spots or relatively well-defined; (17) condition of sexual dichromatism in throat colour unknown; (18) condition of sexual dichromatism in ventral colouration unknown; (19) iris with metallic pigmentation and pupil ring; (20) large intestine anteriorly pigmented; (21) colour of testes unknown; (22) mature oocytes partly pigmented; (23) median lingual process short, wider than long, tapered (24) maxillary teeth present, small.

Description of the Holotype. An adult female 27.3 mm SVL in excellent condition of preservation. Dorsal skin granular, more tuberculate posteriorly; ventral skin slightly granular. In preservative, a barely distinct epidermal ridge borders the tip of snout dorsally. Dorsal surface of hind limbs granular and tuberculate, with two distinct symmetrical enlarged tubercles located laterally between urostyle and vent ( Fig. 1 ; see Grant et al. 1997 for a description and illustration of the cloacal tubercles).

Head longer than wide (HL2> HW), greatest width 34% of SVL. Snout bluntly pointed in lateral view, extending past the lower jaw, bluntly pointed in ventral and dorsal views. Nares located close to tip of snout, directed posterolaterally; nares visible from front, barely visible from above and below; posterior rim of naris bordered behind by a crescent-shaped ridge; rim bearing a small tuberclelike prominence posterodorsally, this “bump” is distinct in frontal, dorsal and ventral views; internarial distance 40% of greatest head width. Canthus rostralis well defined; loreal region straight, sloping outward to lip. Interorbital distance 83% of eye length, 90% of upper eyelid width. Snout length 123% of eye length, 49% of head length; distance from anterior corner of eye to posterior margin of naris 60% of eye length. Postrictal tubercles inconspicuous. Tympanic membrane inconspicuous, round, concealed posterodorsally by a diffuse supratympanic swelling; tympanic annulus prominent anteroventrally; tympanum 43% of eye length, separated from eye by a distance equal to 23% of eye length. Midline distance from tip of snout to arm insertion greater than distance from arm insertion to thigh insertion (HL3> BEL).

Forearm slightly longer than upper arm, no distinct ulnar fold. Hand moderate in size, HAND III 27 % of SVL, 78% of HW. Relative length of fingers III> IV> I ≥ II. Fingers unwebbed. Discs of fingers expanded, disc on Finger IV widest, discs on other fingers subequal. Fingers with keel-like lateral folds (sensu Myers & Donnelly 2008), best developed pre- and (slightly) postaxially on Finger II and preaxially on Finger III ( Fig. 2 A).

Palmar tubercle large, rounded, slightly heart-shaped; thenar tubercle smaller, elliptical; one or two round to ovoid subarticular tubercles (one each on Fingers I and II, two each on Fingers III and IV, with distal tubercles on Finger III and IV slightly less conspicuous). A very low, barely distinct outer metacarpal fringe. Tip of Finger IV distinctly surpassing the base of distal subarticular tubercle on Finger III when fingers adpressed. No fleshy supracarpal fold atop wrist ( Fig. 2 A).

Hind limbs robust, moderately long, with heel of adpressed leg reaching anterior corner of eye; TIL 49% of SVL. Relative lengths of adpressed toes IV> III> V> II> I; first toe short, slightly surpassing the base of subarticular tubercle of second toe. Toe discs expanded, slightly larger than finger discs, largest on Toes II and IV. Feet moderately webbed; all toes with well developed folded flaplike fringing (sensu Myers & Donnelly 2008), except on postaxial edge of Toe V on the right side. Webbing formula I 0+– 2- II 1-–2 ½ III 2 -–3+ IV 3 ½– 2- V ( Fig. 2 A).

Inner metatarsal tubercle small, elliptical; outer metatarsal tubercle small, round, about half the size of the inner; a distinct oval medial metatarsal tubercle present on both sides. One to three round to ovoid subarticular tubercles (one each on Toes I and II, two each on Toes III and V, and three on Toe IV, with distal tubercle on Toe IV the smallest and least conspicuous). A strong outer metatarsal fold coextensive with the folded flaplike fringing on Toe V, almost reaching the outer metatarsal tubercle on the left side; outer metatarsal fold absent on the right side. A slightly tuberclelike tarsal keel weakly curved at proximal end, extending proximolaterad from preaxial edge of inner metatarsal tubercle, not continuous with the fringe along the outer edge of the first toe ( Fig. 2 A).

Maxillary teeth present, small. Tongue longer than wide, wider and free posteriorly, with rounded margin; median lingual process short, wider than long, tapered.

Colour of the Holotype in life. Dorsal ground colour medium brown, with a dark brown V-shaped interorbital bar slightly outlined with light creamish brown, followed by two less defined dark brown bars, the first more or less V-shaped, at the level of arm insertion, the second just anterior to sacrum. Small, poorly defined, dark brown flecks on snout, between and on dorsal bars. Upper surface of arm light brown with welldefined dark brown transverse bands on forearm and wrist, a less defined one on elbow; upper surface of thigh, shank, and foot light brown with well-defined dark brown transverse bands. A yellow wash on the anterior face of the thigh. Flanks dark brown, slightly lighter ventrally with a few bluish irregular spots and a few whitish irregular blotches on the lower part forming a broken inconspicuous ventrolateral stripe. A few white spots (covering small tubercles) form a broken oblique lateral stripe that does not extend to arm insertion. No dorsolateral stripe. Upper lip creamish brown suffused with melanophores, two bluish marks below eye; loreal region and side of head dark brown; tympanum area light creamish brown concealed in a poorly defined light stripe from posterior corner of eye to arm insertion. A dark brown stripe is present on the anterior edge of upper arm, tapering from arm insertion to forearm. Throat light brown, blotched with white and dark brown; belly light grey, blotched with dark brown, blotches more numerous and larger laterally. Undersurface of upper arm light brown with a few dark markings; undersurface of forearm blackish; undersurface of thigh and shank light grey blotched with dark brown; rear of thigh and cloacal region blackish. Pale reddish orange paracloacal marks present. Tip of digits whitish. Palms and soles black. Iris mostly orange-bronze, darkened with black suffusion, with two oblique metallic white marks separated by a black triangular mark below pupil ( Fig. 1 A–B).

Colour of the Holotype in preservative. Dorsal ground colour brown, with a dark brown V-shaped interorbital bar slightly outlined with light brown, followed by two less defined dark brown bars, the first more or less V-shaped, at the level of arm insertion, the second just anterior to sacrum. Small, poorly defined, dark brown flecks on snout, between and on dorsal bars. Upper surface of arm light brown with well-defined dark brown transverse bands on elbow, forearm and wrist; upper surface of leg light brown with well-defined dark brown transverse bands on thigh, shank, and foot. Flanks dark brown, with some irregular spots and a few whitish irregular blotches on the lower part forming a broken inconspicuous ventrolateral stripe. A few white spots (covering small tubercles) form a broken oblique lateral stripe that does not extend to arm insertion. No dorsolateral stripe. Upper lip dirty brown suffused with melanophores, two whitish marks below eye; loreal region and side of head black; distinct whitish stripe extending from posterior corner of eye to arm insertion including most of tympanum. A dark brown stripe is present on the anterior edge of upper arm, tapering from arm insertion to forearm. Throat and belly whitish, blotched with dark brown. Undersurface of upper arm whitish with a few dark markings; undersurface of forearm blackish; undersurface of thigh whitish blotched with dark brown; undersurface of shank light grey blotched with dark brown; rear of thigh and cloacal region blackish. Light brown paracloacal marks present. Palms and soles black ( Fig. 1 B–C).

Variation. See Table 1 for morphometric measurements of the holotype and the paratypes and Figs. 2 B and 3 for intra- and interpopulational variation.

Symmetrical enlarged cloacal tubercles are clearly visible in the holotype. Those tubercles are present, but less visible in the paratypes probably due to an artefact of preservation (cloacal tubercles are most visible in well preserved specimens).

Only the holotype and one paratype have a medial metatarsal tubercle, a character that is sometimes present in other Anomaloglossus species as well.

Only the holotype lacks folded flaplike fringing on the postaxial edge of Toe V and a coextensive strong outer metatarsal fold on the right side, indicating an aberrant condition.

An additional difference between the holotype and the paratypes is the length of Finger I, which is slightly longer than II in the holotype on the left hand (vs. shorter in the two paratypes), and subequal on the right hand (vs. shorter in the two paratypes).

Character IRSNB 1986 ROM 39637 ROM 39638 Toe webbing variation in females (male unknown) is I 0+-2- II (1- -1½)–(2½-3-) III (2- -2)–(3+-3½) IV (3½- 3½)–(2- -2) V.

The condition of the oblique lateral stripe is variable among specimens, from a series of light spots/ blotches extending diagonally from the groin across the flanks and barely reaching the level of the insertion of the arm (e.g. IRSNB 1986) to an almost solid, clearly visible stripe extending diagonally from the groin across the flanks to the level of the insertion of the arm, then breaking in a series of light spots almost reaching the eye (e.g. ROM 39638). Slight variation also occurs between the right and the left flank.

In life, ROM 39638 was darker and the dark dorsal bars less detectable ( Fig. 2 B).

Tadpole description. Two tadpoles were collected in a stream at 1490 m on Mt. Ayanganna. Description and illustrations of one of the two stage-25 tadpoles are provided in MacCulloch and Lathrop (2009: 11, under Anomaloglossus tepuyensis ).

Comparison with other known Anomaloglossus tadpoles occurring in the Pantepui region.- Tadpoles of A. megacephalus most resemble those of A. parkerae ( Meinhardt & Parmalee, 1996) and A. tepuyensis , which are also deposited in streams. The tadpole of A. parkerae was described by Duellman (1997), that of A. tepuyensis by Myers and Donnelly (2008). Both descriptions contain drawings and written descriptions. Two items are noteworthy: (1) Duellman (1997) describes the oral disc of A. parkerae as “not emarginate”, whereas Myers and Donnelly (2008) describe the oral disc of A. tepuyensis as “emarginate”. The oral disc margins of these two species are very similar ( Duellman 1997, fig. 12; Myers & Donnelly 2008, fig. 17) and we follow Grant et al. (2006) in describing the oral discs of Anomaloglossus as emarginate; (2) Duellman (1997) describes the LTRF of A. parkerae as 2(1)/3, although the oral disc illustrated shows a LTRF 2(2)/3. This is obviously an error and the LTRF of A. parkerae is 2(2)/3, like in A. tepuyensis and A. megacephalus .

Although there are few quantifiable differences among the larvae of Anomaloglossus megacephalus , A. parkerae and A. tepuyensis , the tadpole of A. megacephalus markedly differs from that of A. parkerae and A. tepuyensis in having a longer tail [tail length of stage-25 tadpoles is 68% of total length in A. megacephalus (n=2) vs. 62-63% in A. parkerae (n=4) and A. tepuyensis (n=29) tadpoles in the same stage], in having the maximum height of tail similar to body height (distinctly higher in A. parkerae and A. tepuyensis ), and in having the upper fin noticeably lower than tail musculature at midtail (higher or equal in A. parkerae and A. tepuyensis ).

When compared to other known Anomaloglossus tadpoles from the Pantepui region, A. megacephalus differs from A. beebei and A. roraima by stream habitat (phytotelmata habitat in A. beebei and A. roraima ); from A. kaiei and A. praderioi in having the upper fin slightly increasing in length from tail-body junction [first quarter of upper fin straight before increasing in length to about midlength in A. kaiei (n=30) and A. praderioi (n=11)]; and from A. tamacuarensis ( Myers & Donnelly, 1997) in having a longer tail [body length of stage-25 tadpoles is 68% of total length in A. megacephalus (n=2) vs. 63-65% in A. tamacuarensis (n=12) tadpoles in the same stage], and in having less marginal papillae and shorter lateral processes.

Distribution and ecology. Anomaloglossus megacephalus is currently only known from the eastern base of Maringma Tepui, Guyana, where it occurs at 1060 m elevation in low-canopy forest, and from the northeast plateau of Mt. Ayanganna, Guyana on the basis of two specimens collected at 1490 m elevation in dense lowcanopy, high-tepui forest ( Fig. 4 ).

Anomaloglossus megacephalus appears to be uncommon and elusive, with only three specimens collected. It is a diurnal species, the holotype was found on the sandy bank of a small forest stream. The Ayanganna specimens were collected in wet forest not closely associated with stream banks.

Egg deposition site unknown. Tadpoles are deposited in streams. Advertisement call is unknown.

Figures

FIGURE 1. Anomaloglossus megacephalus sp. nov. A: Dorsolateral view of the holotype in life (IRSNB 1986, 27.3 mm SVL). B: Ventral view of the holotype in life. C: Dorsal view of the preserved holotype. D: Ventral view of the preserved holotype. Photos by PJRK.

FIGURE 2. Anomaloglossus megacephalus sp. nov. A: Ventral views of left hand (left) and left foot (right) of the female holotype (IRSNB 1986, 27.3 mm SVL). Scale bars are 2 mm. B: ROM 39638, female paratype (27.9 mm SVL), from Mt. Ayanganna. Photos by PJRK (A) and AL (B).

FIGURE 3. Anomaloglossus megacephalus sp. nov., showing intra- and interpopulational variation in dorsal (A) and ventral (B) pattern in preservative. Two upper specimens are from Mt. Ayanganna: ROM 39637 (upper left, female 28.3 mm SVL) and ROM 39638 (upper right, female 27.9 mm SVL). Lower specimen is the holotype (female 27.3 mm) from Maringma Tepui. Photos by PJRK.

FIGURE 4. Map of the eastern Pantepui region showing the known distributions of Anomaloglossus megacephalus sp. nov. (circles): 1 = type locality, Mount Maringma, Guyana; 2 = Mount Ayanganna, Guyana. The type locality of A. tepuyensis is indicated by a triangle. Maps elaborated after a radar image of South America by NASA / JPL / NIMA available at http: // photojournal. jpl. nasa. gov / catalog / PIA 03388.

Tables

TABLE 1. Morphometric measurements (in mm) of the type series of Anomaloglossus megacephalus. Abbreviations are defined in the text. Male is unknown.

SVL 27.3	28.3	27.9
HL1 8.8	8.5	9.1
HL2 10.5	10.7	10.8
HL3 12.2	10.8	11.7
HW 9.2	9.9	9.6
SL 4.3	4.4	4.2
EN 2.1	2.2	2.3
IN 3.8	3.5	3.6
EL 3.5	3.6	3.5
IO 2.9	3.1	2.8
TYM 1.5	1.4	1.5
FAL 5.7	5.8	6.6
HAND I 5.4	5.0	5.6
HAND II 5.2	5.9	5.9
HAND III 7.3	8.0	7.6
HAND IV 6.0	6.2	6.1
WFD 0.9	1.0	1.1
FL 12.7	13.4	14.3
WTD 1.2	1.2	1.2
TIL 13.5	13.9	14.5
AL 5.7	5.6	5.6
BEL 10.5	10.8	12.0