Chaltenobatrachus grandisonae Lynch 1975, comb. nov.

Abstract

Chaltenobatrachus grandisonae (Lynch 1975) comb. nov. Telmatobius grandisonae Lynch (1975) Atelognathus grandisonae Lynch (1982) Alsodes monticola Cei and Gil (1996) New specimens. CNP A–392, 393, 342, 343, 394–400 collected 27 January 1997, Lago del Desierto, Santa Cruz Province, Argentina (49º04’41’’S, 72º54’17’’W). Description (based on types and new available specimens). Small to medium frog (adults up to 46 mm SVL; Table 1) with frog–like appearance, body and limbs of regular proportions. Head somewhat smaller than one third of body length, depressed, rounded in dorsal view, wider than long. Snout shorter than ocular diameter, rounded to slightly truncate in dorsal view; sloping, with a noticeable angle at the level of the nostrils in lateral profile. Upper lip slightly protruding over lower lip. Nostrils oval, somewhat protuberant, directed dorsolaterally, approximately equidistant between the tip of the snout and the eye. Canthus rostralis rounded, loreal region weakly concave and strongly sloping towards the lip. Eyes large, very prominent and fairly lateral (in dorsal view protruding from the mandibular branches), oriented laterally. Pupil rhomboidal; a small and round ventral pupillary nodule on lower border of iris evident in some specimens. Interocular distance smaller than upper eyelid width, and similar to internarial distance. Tympanum absent. Supratympanic fold noticeable and thick, extending from the posterior end of the eye to the insertion of the arm. Tongue rounded, somewhat emarginate posteriorly (notched in exemplar MLP A–5259), free laterally and posteriorly. Premaxillary and maxillary teeth large; vomerine teeth in two oval, prominent patches, located close together, between and at posterior level of the choana. Choanae rounded, not concealed by the pars palatine of maxilla. Arms thin and of moderate length. Fingers moderately long, with noticeable interdigital membrane, more developed between the pollex and second finger and between the second and third fingers; tips of fingers rounded (Figure 3 a). Pollex very wide at its base. Length of fingers in increasing order: 1=2–4–3. Metacarpal tubercles large but low, the inner oval, the external weakly bifid; subarticular tubercles large and rounded or wider than long, the proximal ones larger and more protuberant; supernumerary palmar tubercles absent. Forearms somewhat more robust than arms. Legs thin and of moderate length. Toes depressed, with thick interdigital membrane, deeply incised, continuing as a dermal fringe on all toes until almost the rounded tip. Toe V with narrow dermal fringe. Length of toes in increasing order: 1–2–5–3–4. Plantar skin turgid; two little, low, noticeable metatarsal tubercles (Figure 3 a), the inner one oval and the outer one smaller and circular; subarticular tubercles small, rounded; supernumerary plantar tubercles absent. Tarsal fold noticeable, extending along most of the tarsus and continuous with the dermal fringe of the first toe. Tibiotarsal articulation reaching the eye. When femurs and tibias placed at right angle to the sagittal plane, the tibiotarsal articulations not in contact. Skin thin and mucoid. Back of the head, dorsum, and legs finely granulated with numerous warts, soft and turgid, of variable size and shape (rounded or elongated). Ventral skin smooth and loose; seat patch with turgid vascularized warts, restricted to the lower side of the thighs near the vent. Gular fold faint. Males with nuptial excrescences in the form of asperities, little pigmented, wide on the dorsal and inner side of the pollex and less extensive on the inner side of the second finger; also reaching the inner edge of the inner metacarpal tubercle. Color in life. Back of the body and limbs fairly uniform bright green color, with brown to reddish warts (Figure 2). Dark, diffuse transverse bands on the dorsal side of the legs, more evident in juveniles. Belly and lower part of the flanks greyish, evenly speckled with tiny black spots. Throat whitish speckled with small dark spots. Ventral skin of the legs brownish and translucent. A diffuse dark brown band from the tip of the snout to the eye, including the nostrils, continuing to the axillary region along the supratympanic fold. A dark patch under the eye reaching the upper lip. Iris orange with gold spots; a dark vertical line under the pupil. Metamorphs show the typical species coloration. Juveniles with more intense colouring of the transverse bands of the legs, the dorsal warts and the bands on the head. Osteology. (Description based on CNP A–392, adult male). Skull as long as wide (Figure 3 b). Frontoparietals paired, moderately extensive, exposing a thin frontoparietal fontanelle (frontoparietals nearly contacting each other in holotype), widely separated from nasals. Nasals relatively small, separated from one another medially and from the pars facialis of the maxilla laterally. Maxillary arch incomplete, lacking independent quadratojugal. Alary processes of premaxillae extensive, directed dorsally. Pars dentalis of premaxilla bearing 9−11 well developed pedicellate teeth; pars palatina narrow, with prominent palatine process. Pars facialis of maxilla rectangular; pars dentalis bearing 26−28 teeth extending up to the middle of the orbit; pars palatina narrow, no pterygoid processes developed. Parasphenoid triradiate; cultriform process lanceolate, not reaching anteriorly the level of the planum antorbitale; parasphenoid alae directed laterally. Vomers relatively small, widely separated medially; dentigerous processes situated between and partially posterior to choanae, each bearing 2−3 well developed teeth; prechoanal, postchoanal, and anterior processes of vomer well developed; anterior processes widely separated from the maxillary arcade. Palatines relatively long, reaching the maxilla, bearing well developed anterior processes. Pterygoids triradiate; anterior ramus of pterygoid in contact with maxilla, not reaching the planum antorbitale; medial ramus of pterygoid in contact with otic capsule but not bearing a bony articulation. Zygomatic rami of squamosals relatively long; otic rami shorter than zygomatic rami, overlapping the cartilaginous cristae parotica. Sphenethmoid well ossified, extending anteriorly notably beyond the anterior edge of nasals, with an anteromedial ossification between the nasal capsules; bony sphenethmoid not reaching the anterior margin of optic foramen posteriorly. Prootics fused with exoccipitals; epiotic eminences well developed. Occipital condyles lacking a constricted base and slightly separated medially. Opercula present, not mineralized. Columellae and tympanic annuli absent. Hyoid plate width approximately equal to medial length (Figure 3 c); hyalia long, lacking anterior processes; anterolateral and posterolateral hyoid processes present, long and slightly expanded distally; posteromedial hyoid processes long and well ossified. Eight procoelous, nonimbricate presacral vertebrae. Cotylar facets of atlas narrowly separated, approaching a Type II condition (Lynch 1971). Transverse processes of presacrals II −IV broader than those of vertebrae V −VIII. Transverse processes of presacrals II, VII and VIII distinctly oriented anteriorly; processes of presacrals V–VIII slightly shortened. Sacral diapophyses slightly deflected posteriorly; moderately dilated. Sacrococcygeal articulation bicondylar. Urostyle with small dorsal crest on proximal half. Pectoral girdle arciferal (Figure 3 d). Omosternum cartilaginous; elongate, with anterior end expanded. Scapula bicapitate. Clavicle arched, not overlaying the pars acromialis of the scapula. Coracoid narrowly dilated at its distal and proximal ends. Sternum cartilaginous, expanded posterolaterally. All cartilage of pectoral girdle calcified to some degree in adult specimen examined. Cleithrum cleft distally. Ilial shaft cylindrical, elongate; dorsal crest poorly developed; dorsal prominence directed dorsolaterally; protuberance evident; preacetabular angle approximately 90°. Ischia small, lacking prominent processes. Pubis cartilaginous, calcified. Humerus slender, bearing distinct crests; crista ventralis moderate; crista medialis slightly larger than crista lateralis. Phalangeal formula of hand 2–2–3–3. Terminal phalanges knobbed. Prepollex with two ossified elements. Inner metacarpal with a notorious distal flange at medial margin of the bone. Prehallux with one basal element ossified and three distal cartilaginous elements. Phalangeal formula of foot 2–2–3–4–3. Tadpole (based on 6 specimens at stages 31 to 39 sensu Gosner (1960), CNP A–395–400) Medium–sized larva (up to 56 mm) (Figure 4 a,b; Table 2). Body elliptic in dorsal view, with a slight constriction posterior to the head; body 2 times longer than high, somewhat depressed (1.2 times wider than high), 35–40% of total length. Snout rounded in dorsal and lateral view. Nostrils small and circular, with an elevated internal rim, in dorsolateral position, slightly closer to the snout than to the eyes, opening into a depression, not raised. Distance between nostrils smaller than distance between eyes (0.4 to 0.6 times). Eyes large, in lateral position, oriented dorsolaterally, small umbraculum (fleshy projection of the iris over part of the pupil) present. Spiracular tube sinistral and conspicuous; the distal end free from the body wall. Spiracle posterolaterally directed, located beneath the mid-line of the body, 46–62% of body length, inner wall free. Vent tube dextral, short, with dextral opening. Tail slightly higher than the body, about 60−65% of total length. Caudal musculature robust, not reaching the tip of the tail. Tail axis straight. Dorsal and ventral fins well developed, of similar height, with gently arched margins; dorsal fin arising from the last part of the body or at the tail-body junction; ventral fin arising at the level of the cloacal opening. Tip of the caudal fin rounded.