Rhinatrema ron Wilkinson & Gower, 2010

Maciel, Adriano O. & Hoogmoed, Marinus S., 2011, Taxonomy and distribution of caecilian amphibians (Gymnophiona) of Brazilian Amazonia, with a key to their identification, Zootaxa 2984, pp. 1-53 : 44-46

Rhinatrema ron Wilkinson & Gower, 2010

Diagnosis. Maximum known TL 353 mm. A Rhinatrema without large cephalic spot on anterior part of head, TBA 276–347. No tail tubercles in males or females. Vent may be transverse or longitudinal. Only first nuchal groove clearly distinct. Tongue with distinct longitudinal grooves. Palatal mucosa distinctly plicate. Rhinatrema ron differs from R. bivittatum mainly in having a plicate palatal mucosa; lacking a large yellow spot on the anterior region of head; lacking pale spots on dorsal and ventral surfaces of the tail; in the absence of tail tubercles in males and in having only first nuchal groove distinct. Rhinatrema ron differs from R. shiv Gower et al., 2010 in having a lower number of TBA (276–347 instead of 335–382 in R. shiv ).

Description. TL 19.6–27.7 times (24.3 ± 4.7; n = 33) BW. Nostrils subcircular, visible from above, near tip of snout. Eyes visible in open orbit; medially positioned between nostrils and corner of mouth, slightly closer to nostrils than corner of mouth in most specimens. Eyes at same level as, or slightly above, nostrils. Palatal mucosa plicate. First nuchal groove distinct dorsally and ventrally, no dorsal transverse groove; second and third nuchal grooves indistinct. Body subcylindrical, slightly wider than deep. Most annular grooves complete, except some anterior grooves which are ventrally incomplete (e.g. four in MPEG 19966), and grooves interrupted by the vent. Small terminal shield on tip of tail. Tail small and slender, maximum length 3.5 mm (MPEG 26477). All tail annuli complete in males and females; no tubercles on ventral region of tail in either sex. Dermal scales from first body annulus to last tail annulus; one row of dermal scales per body annulus, completely encircling the body, except in first few incomplete body annuli. The vent may be transverse or longitudinal ( Fig. 22 ); AD 13–20 (15.4 ± 5.4; n = 29). Paired anal papillae may be present; found in 14 of 22 males and two of 10 females specimens assessed. PMT maximally 30 with slight variation in size, maxillary teeth slightly larger, they may extend posteriorly of choanae, as PPT. PPT maximally 40, with little variation in size. No diastema between PVT and PT; teeth smaller than those in maxillary series DT maximally 26, approximately same size as PMT. ST maximally 22, approximately same size as PPT.

Color. Two color patterns for the dorsum of the body can be discerned ( Fig. 24 ). In the first, the dorsal region is predominantly dark brown with sparse yellow spots. The other pattern is characterized by more and closer spaced yellow spots than in the first pattern. The holotype (MZUSP 60016; Wilkinson & Gower, 2010) has the second pattern. Border of lower jaw, as well as dorsal and lateral surface of head above the commissure of the mouth differ from dorsal body color pattern in having yellow spots of larger size. A specimen from Urucará municipality (MPEG 26945) and the holotype from Manaus, state of Amazonas, Brazil have a more yellowish head than specimens from Oriximiná, state of Pará, Brazil. Yellow stripe with dorsal and ventral border not well defined on sides of body from nuchal region to level of vent; it may extend anteriorly to corner of mouth. Ventral surface of body paler than dorsum, with fewer yellow spots. In preservative, yellowish body parts become whitish or pale yellow, and brownish parts become bluish in some specimens. See photos of live specimens ( Fig. 24 ) and those of the preserved holotype in Wilkinson & Gower, 2010.

Variation. There is no sexual variation in color. Females have higher means in most of the morphometric characters studied. Given the rather small number of specimens, we did not apply ANOVA to test sexual dimorphism and only present the differences in Table 14 .

Distribution. Known from the type locality, approximately 70 km north of Manaus, and in the municipality of Urucar, state of Amazonas north of the Amazon, Brazil. Also in the southern and northern parts of the municipality of Oriximin, state of Par, Brazil ( Fig. 23 ).

A rhinatrematid larva from Parque Nacional Montanhas do Tumucumaque, Amap state, Brazil is present in the material of IEPA (IEPA/TQ634). The specimen has a longitudinal vent and because of this might belong to R. ron , but because hardly anything is known about the ontogeny of Rhinatrema , we prefer not to include this specimen in the treatment of this species or the distribution map. This specimen has no annuli in the anteriormost part of the body, which might be a larval character. The specimen hails from an area (Tumuc Humac) from which only R. bivittatum is known, but because of the longitudinal vent we prefer to mention this specimen here.

Natural history. According to field notes of Délio Baêta and of Emiliane G. Pereira, most specimens were collected in pitfall traps. MPEG 26477 was collected at 22.55 h on the ground in rainforest (M.A. Ribeiro-Junior, pers. comm.). These data are consistent nocturnal foraging on the surface of the soil.

Figures

FIGURE 22. Views of vent region of Rhinatrema. From left to right: female of R. bivittatum IEPA TQ 347; male of R. bivittatum IEPA / TQ 287; female of R. ron MPEG 20177.

FIGURE 23. Distribution of the genus Rhinatrema. Square represents R. shiv. Circles represent R. bivittatum and triangles R. ron. 1. Kaieteur National Park, Guyana (Kok & Kalamandeen, 2008; Gower et al., 2010); 2. Winiperu, Guyana (Nussbaum & Hoogmoed, 1979); 3. Brownsberg Natural Reserve, Suriname (Nussbaum & Hoogmoed, 1979); 4 - 10. Localities in French Guiana plotted as an adaptation of map of Lescure & Marty (2000: 295); 11. Parna Montanhas do Tumucumaque, Laranjal do Jari, Amapá, Brazil; 12. Serra do Acaraí, Oriximiná, Pará, Brazil; 13. Floresta Nacional Amapá, Ferreira Gomes, Amapá, Brazil; 14. Reserva de Desenvolvimento Sustentável do rio Iratapuru, Laranjal do Jari, Amapá, Brazil; 15. Almeirim, Pará, Brazil; 16. Laranjal do Jari, BR 156, Amapá, Brazil; 17. Porto Trombetas, Oriximiná, Pará, Brazil; 18. Urucará, Amazonas, Brazil; 19. Reserva INPA-WWF, km 76 BR 174. Amazonas Brazil.

FIGURE 24. Live specimens of Rhinatrema ron showing two color patterns. Above, specimen from Trombetas, Oriximiná, Pará, Brazil, photo by Gleomar Maschio, and below a specimen from Urucará, Amazonas, Brazil, photo by Ricardo Kawashita Ribeiro.