Myersiohyla KANAIMA

ON MYERSIOHYLA KANAIMA

MacCulloch and Lathrop (2005) reported on 23 specimens of Myersiohyla kanaima collected on Mount Ayanganna, Guyana. The authors reported that “enlarged black-and-white eggs, 1 mm in diameter, were present in 13 of the 17 females; the remainder had small white ova.” However, our dissection of female USNM 549311 (SVL 46.4 mm.) revealed 19 eggs in the left ovary (largest diameter 2.9–3.2, ẍ = 3.07, s = 0.12); these eggs are densely pigmented overall, and the animal and vegetal poles are not distinguishable. This observation is more in line with Duellman and Hoogmoed’s (1992) report for three female M. kanaima, which had “relatively large (1.8 mm diameter) ... pigmented oviducal eggs.” Differences in egg size and coloration seem most likely to reflect state of maturity.

MacCulloch and Lathrop (2005) further described a series of tadpoles that they assigned to Myersiohyla kanaima on the basis of the presence of two subadults and two recently metamorphosed individuals (stage 45) on the bank of the stream, plus one metamorph (stage 43) collected along with the other tadpoles. These tadpoles differ from those of M. aromatica, M. chamaeleo, M. inparquesi, and M. neblinaria most notably in having an oral disc with a 2/4 LTRF.

On the basis of the taxonomic distribution of LTRFs in Cophomantini, Faivovich et al. (2005) suggested that an increase in the number of labial tooth rows is likely a putative synapomorphy of Cophomantini, because all known larvae of Hyloscirtus and Myersiohyla at that time had a minimum of 6/7 labial tooth rows. They stressed, however, that the minimum number of labial tooth rows that would be a synapomorphy was ambiguous because the tadpole of M. kanaima was unknown at that time.

Taking into account the position of Myersiohyla kanaima in our phylogenetic hypothesis, nested within a group where the minimum known labial toothrow formula is 6/7, a 2/4 LTRF is a stark contrast. This could well be simply another case of homoplasy, and as such it should be considered until new evidence is gathered. The possibility of a mistaken association between subadults, juveniles and metamorphs that led to the identification of these tadpoles should also remain open to question.

MATERIAL: The first author examined the following specimens that had been assigned to Myersiohyla kanaima: Guyana: Mazaruni-Potaro: northern slope of Mount Roraima: USNM 549311 ♀; Guyana: District 7: Mt. Ayanganna: ROM 39587 ♀, 39575– 76 ♂♂, 39590 ♀, 43861 ♂, 43871 ♂, USNM 561828– 29 ♀♀.