Eleutherodactylus auricarens (Myers and Donnelly, 2008) Myers & Donnelly, 2008

Myers, C. W. & Donnelly, M. A., 2008, The Summit Herpetofauna Of Auyantepui, Venezuela: Report From The Robert G. Goelet American Museum-Terramar Expedition, Bulletin of the American Museum of Natural History 2008 (308), pp. 1-147 : 72-79

Eleutherodactylus auricarens , new species Figures 42–45, 47B, 47C

Eleutherodactylus sp. : Myers, 1997: 3 (small forest species on Auyantepui).

Eleutherodactylus auricarens (nomen nudum): Sánchez H. and Bisbal E., ‘‘2002’’ [2004]: 17 (mention of type specimens in EBRG).

HOLOTYPE: EBRG 2725 (field no. CWM 19213), an adult female from summit of Auyantepui at 5 ° 549N, 62 ° 299W ( AMNH – TERRAMAR Camp 2), 1750 m elevation, Bolívar, Venezuela, collected February 9– 11, 1994, AMNH –TERRAMAR Expedition.

PARATOPOTYPES: AMNH A-164951– 164953, EBRG 2724, 2726–2727, with same collection data as holotype.

OTHER PARATYPES: Camp 1, 1700 m: AMNH A-164936–164950, EBRG 2709– 2723, collected 2–4 February, 1994. Camp 4, 1600 m: AMNH A-164954, EBRG 2728– 2729, collected 23 February 1994. All from the 1994 AMNH–TERRAMAR Expedition.

ETYMOLOGY: The specific name auricarens (‘‘lacking ears’’) is an adjective of common gender derived from the Latin auris (‘‘ear’’) + carens (the present participle of careo, ‘‘to be without’’), alluding to the absence of the tympanic apparatus.

DEFINITION AND DIAGNOSIS: A small Eleutherodactylus belonging to the unistriga-

tus species group and characterized by the following combination of characters (in the format of Lynch and Duellman, 1980, 1997): (1) dorsal skin tubercular, ventral skin areolate; (2) tympanic membrane and annulus absent (annulus possibly vestigial in a few specimens, see Remarks); (3) snout truncate to bluntly pointed in dorsal view, rounded in profile; canthus rostralis gently concave or nearly straight, rounded; (4) upper eyelid weakly tubercular (tubercles low, subequal); (5) vomerine odontophores small but distinct, with detectable teeth, oblique, well separated and situated between and behind choanae; (6) males lacking vocal slits/vocal sac; weak nuptial pads seemingly present; (7) finger I shorter than II; broad discs on fingers II–IV; (8) weak lateral keeling but no fringes on fingers; (9) ulnar tubercles absent or low and inconspicuous (not forming a distinct line); (10) no pronounced calcar tubercle; (11) inner metatarsal tubercle oval, much larger than small outer metatarsal tubercle; (12) toes weakly keeled, webless; toe discs broad, subequal with finger discs; fifth toe much longer than third; (13) varying shades of brown above, with interorbital bar and often a vague undulating longitudinal dark marking on dorsum; polymorphism limited, but occasionally with a pale postocular stripe posteriorly widening to cover flanks, or with a few oblique dark stripes extending posteroventrad from indefinitely patterned dorsum; (14) four males about 16–18 mm, nine females 20– 25 mm SVL.

Eleutherodactylus auricarens is distinguished from sympatric E. pulvinatus by absence of a distinct tympanic apparatus, which is externally well defined in E. pulvinatus (see following species account for other differences).18 The only other Eleutherodactylus known to lack the tympanic apparatus in eastern and southern Venezuela is E. yaviensis from the northwestern tepuis, although specimens in one population of

18 Occasional specimens of auricarens have small indistinct circular areas (<0.05 mm, fig. 47B, arrows) under the postocular (‘‘supratympanic’’) fold that are suggestive of concealed tympana, but if the surrounding skin is cut and reflected, the expected tympanic membrane and annulus are found lacking. The occurrence of possible vestiges of the annulus in a few specimens remains to be corroborated (see under Remarks).

yaviensis (Cerro Yutaje´) have a vestigial annulus and membrane concealed under the skin (see Remarks). E. yaviensis is a larger species with a higher degree of pattern polymorphism, although it lacks the vague undulating middorsal marking that is present in many specimens of auricarens (see Remarks for further comparisons between E. auricarens and E. yaviensis ).

MEASUREMENTS OF HOLOTYPE (in mm): The holotype (figs. 44, 45) is an adult female as revealed by presence of large ova and convoluted oviducts. SVL 23.6 , tibia length 13.6, foot length from proximal edge inner metatarsal tubercle to tip of toe IV 11.2 , head width 9.2, head length on the diagonal from tip of snout to angle of jaw 8.0, upper eyelid width 2.7, interorbital distance 3.2, internarial distance 2.3, center of nostril to eye 3.0, eye length 3.1, tympanum absent, width of third finger disc and width of fourth toe disc both 1.3.

DESCRIPTION

The type series of 40 frogs includes only 13 specimens (48, 9♀) judged to be sexually mature. Maturity of females was determined through dissection by presence of enlarged ova and markedly convoluted oviducts. Maturity of males was more difficult to determine because vocal slits are absent, nuptial pads are but faintly developed, and testes are not greatly enlarged. However, the largest males (16.2, 16.8, 17.1, and 17.8 mm SVL) are considered adults, inasmuch as weak nuptial pads seem to be present and the last two specimens amplexed mature females in their plastic collecting bag. Data on size and proportions for both juveniles and adults are summarized in table 5.

MORPHOLOGY: Females are larger than males (x¯ female SVL/ x¯ male SVL 5 1.33). Head little wider than long, usually wider than body (body as wide as head in a few froglets, wider than head in some gravid females); head width 36 % –40 % of SVL in adults, 34 % –39 % in juveniles. Snout truncate to bluntly pointed in dorsal view, rounded in profile; eye-nostril distance 74 % –97 % of eye length in adults, 72 % –94 % in juveniles; nostrils slightly protuberant, directed dorsolaterally; canthus rostralis gently concave or nearly straight, edge rounded; loreal region concave, sloping outward to lip. Upper eyelid bearing low, more-or-less subequal small tubercles; upper eyelid width usually narrow- er than interorbital distance (82 % –95 % of interorbital distance in adults, 72 % –108 % in juveniles). Tympanic apparatus absent (as judged from dissection of all adults and selected juveniles, but see Remarks); a usually pronounced glandular ridge (‘‘supratympanic’’ fold) sloping from eye nearly to forearm, the skin below this fold varying from rugose to nearly smooth (see fn. 18 and Remarks). Two or three sometimes inconspicuous postrictal tubercles between corner of mouth and forearm. Choanae small to moderate, oval to round, not concealed by palatal shelf of maxillary arch; vomerine odontophores distinct, rounded to slightly elongate and slanted posteromedially, distinctly separated medially, situated posterior and median to choanae, each bearing several teeth. Tongue longer than wide, posterior edge varying from straight to rounded, with or without a slight notch, posterior half free. Adult males lacking vocal slits (hence there is no vocal sac); adult males appearing to have a weakly developed, unpigmented, nuptial pad along edge of thenar tubercle.

Dorsal skin finely granular in life (fig. 42) and weakly tuberculate, somewhat more strongly tuberculate on limbs; middorsal raphe present, although only anterior portion visible in some juveniles; throat smooth, venter areolate; a broad triangular area of glandular skin present on posteroventral thigh surfaces; discoidal fold (inconspicuous on most specimens) situated anterior to groin; no ulnar ridge or defined line of tubercles.

Relative lengths of appressed fingers III. IV. II. I; tip of first finger sometimes reaching disc of second; males seeming to have a weakly developed unpigmented nuptial pad along edge of thenar tubercle; fingers with lateral keeling absent or weak, but downward, tightly folded flaplike fringing developed in some adults on medial sides of fingers II – III and lateral side of V (e.g., AMNH A-164938 ♀, 164954 ♀). Finger discs broader than long, slightly rounded to nearly truncate, with subdigital pads much wider than long ; disc on thumb slightly expanded. Palmar tubercle large, cordiform; thenar tubercle oval, large; subarticular tubercles low to somewhat protuberant, either rounded or conical; several supernumerary palmar tubercles (fig. 43), either low or slightly protuberant, sometimes nearly as large as subarticular tubercles.

Hind limbs relatively long; heels overlap when held at right angles to sagittal plane; tibia 50 % –60 % of SVL (table 5). Relative lengths of appressed toes IV. V. III. II. I; tip of toe I not reaching disc of toe II; tip of toe V normally extending to the distal edge of, or well past, the ultimate subarticular tubercle of toe IV; tip of toe III extending to or slightly past the penultimate subarticular tubercle of toe IV.19 Toe discs broad, usually as broad or slightly broader than those on fingers. Toes with lateral keeling weak or absent, but downward, tightly folded flaplike fringing developed in some adults on medial sides of toes III – IV and lateral side of toe V (e.g., AMNH A-164938 ♀, 164954 ♀). Basal webbing essentially absent.20 Inner metatar-

19 Toe V is normally much longer than toe III, but in a few small juveniles (e.g., AMNH A-164941) the tip of toe V barely reaches the ultimate subarticular tubercle of toe IV and is only slightly longer than the third.

20 There is very minimal fleshy ‘‘webbing’’ between the toes, but no thin, clear webbing. The determination of basal webbing as minimal or absent is therefore somewhat subjective.

sal tubercle large, an elongated ovoid, much larger than small round outer metatarsal tubercle; several or many small to moderate supernumerary plantar tubercles (fig. 43), low or protuberant; subarticular tubercles larger, moderately protuberant, rounded to nearly conical. Calcar tubercles low and indistinct, none prominent. Tarsus somewhat tuberculate, lacking a tarsal fold or constantly positioned tarsal tubercle (a small tubercle sometimes distinguishable on distal part of tarsus near inner metatarsal tubercle).

COLORATION: In life (fig. 42), dorsal coloration some shade of brown—gray-brown, brown, blackish brown, greenish brown, orange-brown—with darker interorbital bar and often with a vague, ill-defined, middorsal longitudinal dark marking that usually has a few transverse or sometimes chevronlike lateral extensions or undulations (fig. 44). The longitudinal dorsal mark is lacking in some specimens, including the following: one male and two females each have a dark dorsum and a contrasting pale (orange or gray in life) postocular stripe that extends ventrolaterally and expands on the flank; and a few females have indefinite dark dorsal coloration, from which a few dark stripes extend obliquely (posteroventrally) onto the flank.

Some specimens with an ill-defined dark stripe below the canthus rostralis from eye to snout, often broken or incomplete, with only the anterior half remaining as a longitudinal dark blotch enclosing the nostril, absent in some. Often a brown postocular stripe with or without conspicuously darkened upper and lower edges, sometimes represented only by its upper edge—a narrow black line superimposed on the postocular (‘‘supratympanic’’) fold. Frequently, one to several dark bars radiating from eye to lip, with pigment- ed but slightly lighter interspaces, but lip sometimes moderately pigmented without obvious pattern.

Dark crossbanding on limbs sometimes indistinct, but forearms usually with one distinct band, thighs usually with two, shanks usually with three. Groin suffused with orange, which color often occurs also on concealed part of shank, anterior side of thigh and/or top and rear of thigh. In other specimens, the posterior thigh and concealed part of the shank is uniformly gray or brown in life, uniform or with pale dots.

There is some ontogenetic change in ventral coloration. In life, the ventral surfaces are nearly black in the smallest juveniles, then becoming gray or greenish gray in larger specimens. Ventral coloration tends to be darkest (blackish) under the head, where an occasional specimen has a weakly developed pale midgular line (which is usually absent, see fig. 45); there may be patches or dots of bronze on the gray chest and sometimes on the throat as well. Some sexual dimorphism was suggested by two amplectant males, whose ventral surfaces and posterior thighs (as well as dorsal surfaces, see fig. 42) were much darker than in their respective females, but in preservative there are males and females showing a range of ventral pigmentation from pale to dark. In preservative, the ventral surfaces are pale yellowish, sparsely to densely punctuated with brown, the throat usually being somewhat darker to much darker than the belly (fig. 45). Palms and soles lightly pigmented, palmar and plantar tubercles tending to be somewhat darker, some subarticular tubercles on feet also may be pigmented.

There is individual variation in the living color of the iris, which may be light to dark bronze, golden bronze, or greenish bronze, tending to be paler above than below pupil, and with a red or reddish brown horizontal stripe (which may be ill-defined) through pupil.

NATURAL HISTORY

Eleutherodactylus auricarens was found in patches of forest at camps 1, 2, and 4. It is evidently nocturnal, having been found at night on leaf litter and perched on leaves up to about 1 m aboveground; many were found in leaf litter by day. Two males (AMNH A- 164951, EBRG 2724) amplexed adult females (AMNH A-164952 and EBRG 2725, respectively) in the collecting bag; the females are, respectively, 7.6 and 5.7 mm larger (SVL) than the smaller males (e.g., fig. 42 bottom).

REMARKS

The phylogenetically nearest relative of Eleutherodactylus auricarens may be E. yaviensis , a frog of the northwestern tepuis, which are situated several hundred km west of Auyantepui. The two species are similar in lacking vocal slits and in loss (or near loss, see below) of the tympanic apparatus, as well as in most other morphological detail, including hand and foot structure. Although we indicated the presence of basal webbing on the feet of yaviensis (Myers and Donnelly, 1996: 21) , the determination of minimal basal webbing is subjective (see fn. 20); direct comparison of the two species shows that, although somewhat translucent, the skin (‘‘webbing’’) between the bases of the digits is fleshy and that webbing could as well be coded as absent in both taxa.

Eleutherodactylus yaviensis is a larger species than E. auricarens , with little size overlap ( auricarens 8 about 16–18 mm, ♀ 20–25 mm SVL, versus about 18–21 and 24– 30 mm in yaviensis ). In life, both species (especially adults) tend to have orangish coloration in the groin, on the anterior and posterior thigh surfaces, and on the concealed part of the shank, although this color is more conspicuous and forms orange-red ‘‘flash marks’’ in yaviensis , whereas it is more variable and best described as a ‘‘suffusion of orange’’ in auricarens . Ventral surfaces are pigmented brownish or grayish, sometimes with a yellowish ( yaviensis ) or greenish ( auricarens ) cast, with patches or flecking of bronze on the throat and chest of yaviensis and some specimens of auricarens . Each has a reddish horizontal stripe through the pupil, but the rest of the iris color is somewhat variable in both species.

Although Eleutherodactylus yaviensis is more variable in color pattern (Myers and Donnelly, 1996; 20, fig. 13; 2001: 40, figs. 26, 27), it lacks the vague undulating middorsal marking that is present in many specimens of E. auricarens (compare figs. 44 and 46). However, some specimens of E. yaviensis have, just posterior to the interorbital bar, an indefinite dark blotch that resembles the anterior end of the longitudinal blotch of E. auricarens . This vague anterior blotch is present in some specimens of E. yaviensis from both Cerro Yaví (fig. 46) and Cerro Yutajé (e.g., AMNH A-159162); the anterior blotch may be more evident in preserved specimens of E. yaviensis than in life (in Myers and Donnelly [2001: 40–41], compare their fig. 26, bottom, with same specimen in their fig. 27). Although some frogs in both species have an indefinite dorsal pattern, most of the distinctive pattern morphs of E. yaviensis seem to be lacking in E. auricarens , except for one morph characterized by a conspicuous pale lateral stripe.

We recently called attention to an unusual case of intrapopulational variation in presence or absence of the tympanic annulus and membrane in E. yaviensis , in which the tympanic apparatus, when present, is a feebly developed structure that is concealed beneath the skin (see Myers and Donnelly, 2001: 42– 43, fig. 28).

Because of the variation in E. yaviensis , we dissected (on one side) all 13 adult specimens and five selected juveniles of E. auricarens . We found no compelling or clear-cut evidence of a concealed or vestigial annulus or tympanic membrane in most specimens. However, in a few specimens (e.g., AMNH A-164937, left side; A-164938, right side), there is the faintest suggestion of what might be a small tympanic annulus tipped under the anterior edge of the m. depressor mandibulae (fig. 47C). As already stated (fn. 18), some other specimens of auricarens externally have small indistinct circular areas situated under the postocular (‘‘supratympanic’’) fold. Although corresponding tympanic structures could not be found, these areas, measuring about 0.05 mm across, are externally suggestive of concealed tympana (fig. 47B).

Thus, we suspect that there are external and/or possibly internal vestiges in some specimens of a tympanic structure that otherwise has virtually disappeared in Eleutherodactylus auricarens . However, the situation is not as clear-cut as in E. yaviensis , in which vestigial tympana are clearly present in some specimens (Myers and Donnelly, 2001: fig. 28).

In Eleutherodactylus auricarens , the anterior part of the m. depressor mandibulae either (1) overlaps and appears to originate in part from the epimysium of the m. adductor mandibulae, or (2) the anterior edge of the depressor mandibulae is sharply defined, with its fibers more clearly originating from a thin, white tendinous edge. Somewhat similar variation was noted in earless specimens of Eleutherodactylus yaviensis . In four specimens of E. yaviensis having concealed tympana, a small portion of the m. depressor mandibulae was seen to originate from the posteroventral part of the tympanic annulus in three cases, but not in a fourth specimen in which the tympanic structure seemed particularly vestigial and possibly too weak for even partial anchorage of the depressor mandibulae (Myers and Donnelly, 2001: 42– 43). Such variation in the jaw musculature seems likely to be correlated with ongoing loss of the last internal remnants of the tympanic structure in E. yaviensis , and at least the last external remnants in E. auricarens .