Rhinatrema ron, Wilkinson, Mark & Gower, David J, 2010

Wilkinson, Mark & Gower, David J, 2010, A new species of Rhinatrema Duméril & Bibron (Amphibia: Gymnophiona: Rhinatrematidae) from Amazonas, Brazil, Zootaxa 2650, pp. 63-68 : 64-67

Rhinatrema ron sp. nov.

( Figs. 1–2 ; Table 1 )

Holotype. MZUSP 60016, a mature female, from Reserva INPA-WWF km 76 BR-174, Amazonas, Brazil. Collected by B. Zimmerman, 10 April, 1983.

Diagnosis. A Rhinatrema that differs from its congeners, R. bivittatum (Guérin-Méneville, 1838) and R. shiv Gower, Wilkinson, Sherratt & Kok, 2010 , in having a strongly plicate tongue and palatal mucosa, a more strongly mottled/flecked colour pattern with larger pale patches, a thicker lateral stripe, eyes that are much further from the lip than are the nares, and a much larger maximum body size (> 300 mm).

Description of holotype. Some morphometric and meristic data are given in Table 1 . Good condition except c. 30 mm midventral longitudinal incision c. 75 mm anterior to terminus, some open scale pockets, a possibly artefactually slightly flattened snout tip, narrow constriction caused by tag string c. 42 mm behind snout tip. Body subcylindrical, dorsoventrally compressed, fairly uniform, L/W = 26.3, tapering slightly posteriorly, narrowing more abruptly over last 20 mm. Tail short (L/T = 70.6), slightly laterally compressed, tip bluntly rounded, in lateral view tapers along dorsal edge, underside flat.

In dorsal view, head slightly more U- than V-shaped, as wide as adjacent nuchal region posteriorly, narrowing gently anteriorly to midway between eyes and nares. In ventral view, lower jaws virtually as wide as head, tip more bluntly rounded than snout anteriorly such that mouth marginally subterminal. In lateral view, a dorsal bulge posterior to eyes caused by adductor musculature makes posterior of head deeper than adjacent nuchal region, head tapers very gently anterior to eye level, quite sharply over anteriormost 2 mm, edges of mouth (lips) fairly straight, slightly downturned at CM, CM one and a half times further from top than from bottom of head, lower jaws robust (almost as deep as upper jaws at eye level).

Eyes small (0.6 mm), clearly visible through clear skin, slightly elevated above adjacent skin, slightly closer to top of head than to lip in lateral view, inset by about twice their diameters from outline of head in dorsal view; distances between eye and lip almost four times diameter of eye. TAs small (0.6 mm) quartercircle slits curving anteroventrally from anterodorsal edges of eyes, margins slightly elevated. Nares small (0.4 mm), ovate, visible dorsally inset about one and a half diameters from outline of head, posterior part a shallow depression sloping into deeper semi-lunate anterior aperture; in lateral view, each naris visible just behind anterior margin of mouth, inset a little more than one diameter from snout tip, approximately equidistant from top of head and margin of mouth; closer to lips (1.2 mm) than are eyes (1.8 mm), visible in anterior but not ventral views.

Teeth strongly recurved, outer rows largest, members of dentary series noticeably larger than ‘opposing’ premaxillary-maxillary teeth, IMs larger than ‘opposing’ vomeropalatine teeth. Outer rows with few small anteriormost teeth followed on each side by several widely-spaced, hypertrophied (up to 2 mm long), stilettolike teeth with slight medial curvature distally, ending with more recumbent, successively smaller, more closely spaced teeth. Inner tooth rows with similar but less substantial size variation (lacking hypertrophied elements), IM rows bending to form a tight angle anteriorly. Tongue strongly plicate over entire surface, narrow with free tip anteriorly, expands posterolaterally to cover all but six or seven anteriormost IMs on each side. Choanae subcircular, transverse diameters greater than distance between them. Entire palate posterior to choanae with extensive covering of longitudinal plicae.

Collar region poorly differentiated. NG1 faintly indicated midventrally and laterally. NG2 less faint ventrally, widely incomplete dorsally, somewhat sinusoidal, curving posteriorly from mid-venter and anteriorly across the stripe. NG3 (arbitrarily the first dorsal groove that clearly crosses stripe onto venter) widely incomplete ventrally. C1 shorter (3.3 mm) than C2 (5.7 mm), C2 with five TGs increasing in length from anterior to posterior, length of anteriormost about one third width of collar. AGs orthoplicate except for slight anteromedial curvature on venter close to vent and last eight with strong anterior flexure middorsally, many offset or otherwise irregular. Many anteriormost (perhaps all but one of first 30) AGs narrowly incomplete ventrally, otherwise mostly complete except for seven interrupted ventrally by disc. Tail (area behind the vent) with six (three ventrally incomplete) AGs. Terminal annulus slightly longer than preceding annuli.

Scales begin in TGs of collar region, a single row in shallow pocket at third annulus, tiny on venter, larger and wider than long (e.g., 1.5 x 0.6 mm) on dorsum. At midbody, one or two rows of larger (e.g., 2.2 x 1.1 mm) scales in pockets c. 1.25 times deeper than the length of an annulus. Posteriorly, one main row of large (up to 3.2 x 2.7 mm) scales in very deep pockets (2.5 times length of annulus) with incomplete second row of smaller scales in places. Vent irregular, very slightly longitudinal, formed at centre of an irregular collection of partially subdivided denticulations converging from close to indistinct margins of subcircular cloacal disc.

Dark brownish lavender mottled with irregular paler spots, many merging, the paler colour dominating dorsally except for anteriormost c. 65 mm. Thick, fairly uniform, lateral cream stripes extend from close to tail tip to CMs, except for weak interruptions 9–10 annuli anterior to cloacal disc and clearer gaps on C1, narrower and slightly ventrally expanded on C2. Small breaks in lateral stripes about 20 annuli from terminus and over last 10 annuli, difficult to ascertain precise end point. Head paler than adjacent body dorsally, with irregular darker blotches. Throat darker than body with less pale mottling bounded by broad pale stripes along the mandibles. Annuli with narrow pale edges. Disc pale, with some dark pigmentation on some, especially posterior, denticulations proximal to vent.

Etymology. Named in honour of our esteemed colleague Professor Ronald A. Nussbaum, University of Michigan, USA, in recognition of his many outstanding scholarly contributions to the systematics and biology of caecilians, and celebrating his insights into the fundamental differences between rhinatrematids and all other caecilians. For nomenclatural purposes, the species epithet is considered a noun in apposition.

Suggested common name. Ron’s Rhinatrema .

Figures

FIGURE 1. Preserved holotype (MZUSP 60016) of Rhinatrema ron sp. nov. Photos by Phil Hurst (The Natural History Museum, London). Scale gradations = 1 mm.

FIGURE 2. Anterior view into mouth of holotype (MZUSP 60016) of Rhinatrema ron sp. nov. showing plicate lingual and palatal mucosa.

Tables

TABLE 1. Meristic and morphometric data for the holotype of Rhinatrema ron (MZUSP 60016) and comparative data for the other species of Rhinatrema (from Gower et al. 2010). Values given as means (with ranges in parentheses). E = eye; L = lip; N = naris; V = ventrally; W = width. See Materials and Methods for other abbreviations. Note: a) counts made ventrally and dorsally, respectively; b) counts made just dorsal to stripe; c) n = 2; d) n = 7.

	R. ron	R. shiv (n = 10)	R. bivittatum (n = 28)
TL Tail Length	353 5	153.8 (127–184) 2.7 (2.3–3)	176 (127–219) 2.2 (1.4–2.7)
Tail Length as % of TL	1.4	1.8 (1.5–2)	1.3 (0.8–1.6)
Vertebrae Total annuli	98 321, 347a	97 (95–99) 356 (335–378)b	93 (88–99) 335 (273–384)b
Tail annuli (those behind vent) TGs	5 5	8 (6.5–9.5) 4.6 (4–5)	5 (4–6.5) 4.1 (3–6)
E-E	7.2	2.6 (2.2–2.8)	3.7 (2.9–4.4)
N-N E-N	2.9 5.2	1 (0.9–1.1) 2.3 (2–2.6)	1.4 (1–1.7) 2.9 (2.2–3.4)
Head width (HW) at CM	12.1	4.1 (3.5–4.7)	5.3 (3.5–6.4)
HW at N1 Length of collar region	12.7 9	4.5 (4–5.2) 2.8 (2.4–3.8)	5.6 (4.5–7.4) 3.1 (2.3–4.3)
ST-N1, laterally	16.7 / 18.7	6.8 (5.6–7.4)	8.6 (6.7–10.6)
ST-E ST-CM	7 15.1	2.7 (2.5–3) 4.9 (4.5–5.6)	3.5 (2.5–4.3) 6.6 (4.6–8.3)
ST-CM as % of TL	4.3	3.2 (2.9–3.6)	3.8 (3.1–4.4)
E-CM E-L	7.5 2.1	2 (1.7–2.5) 0.6 (0.4–0.6)	2.7 (1.7–3.7) 0.5 (0.4–0.7)
N-L	1.3	0.5 (0.4–0.6)	0.6 (0.4–0.7)
Head depth behind CM Range in SW at midbody	7.5 5.1–6.3	3.1 (2.8–3.6) (0.5–1.7)	3.5 (2.4–4.6) (0.80–3.5)
W/S	2.4	6.1 (5.2–7.2)	3.6 (2.9–4.6)
Annuli behind end of stripe Midbody width	1–2 or 8 13.4	8.4 (6–11) 5.4 (4.7–6.2)	4.5 (2–7.5) 7.1 (4.2–10)
Body width at vent	6.5	2.9 (2.3–3.6)	2.9 (1.8–4.1)
Midbody circumference Premaxillary-maxillary teeth	43 30	17.6 (14–20) 26 (26)c	21.2 (12–28) 26.3 (24–28)d
Vomeropalatine teeth	40	37 (36–38) c	35.9 (31–39)d
Dentary teeth (Ds) Inner mandibular teeth (IMs)	26 22	29 (28–30) c 26.5 (25–28) c	32.9 (30–35)d 25.7 (24–28)d