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| Rhombophryne longicrus Scherz, Rakotoarison, Hawlitschek, Vences & Glaw, 2015 DOI: 10.3897/zse.91.4979 |
Abstract
The Madagascar-endemic microhylid genus Rhombophryne consists of a range of partly or completely fossorial frog species. They lead a poorly known, secretive lifestyle, and may be more diverse than previously thought. We describe a new species from the high altitude forests of the Sorata massif in north Madagascar with unusual characteristics for this genus; Rhombophryne longicrus sp. n. has long, slender legs, unlike most of its fossorial or semi-fossorial congeners. The new species is closely related to R. minuta, a much smaller frog from the Marojejy massif to the southeast of Sorata with similarly long legs. We discuss the morphology of these species relative to the rest of the genus, and argue that it suggests adaptation away from burrowing and toward a more saltatorial locomotion and an accordingly more terrestrial lifestyle. If this is the case, then these frogs represent yet more ecological diversity within the already diverse Cophylinae. We recommend an IUCN Red List status of Endangered B1ab(iii) for R. longicrus sp. n., because it is known only from a single site in a forested area of roughly 250 km2, which is not yet incorporated into any protected area.
Key Words: Rhombophryne longicrus sp. n., Integrative taxonomy, Rhombophryne minuta, Osteology, Cophylinae, X-ray micro-computed tomography
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| Rhombophryne longicrus sp. n. in life. Holotype ZSM 1630/2012 |
Rhombophryne longicrus sp. n.
Diagnosis:
A microhylid assigned to the genus Rhombophryne on the basis of overall morphology, including the possession of maxillary and vomerine teeth, absence of expanded toe pads, and absence of an enlarged prepollex. Confirmed as a member of the genus Rhombophryne on the basis of its phylogenetic relationships as assessed by mitochondrial DNA, as there are no known morphological characters by which Rhombophryne may be distinguished from Plethodontohyla.
Rhombophryne longicrus sp. n. is distinguished from all other Madagascan frog species by the following set of characters: SVL 23.8–27.9 mm, head wider than long, horizontal tympanum diameter 47% of eye diameter, absence of superciliary spines, weak supratympanic fold, dark supratympanic region and nostril, tibiotarsal articulation reaching the nostril, total hindlimb length 183–185% of SVL, second finger shorter than fourth, and fifth toe shorter than third. It is also separated by a pairwise genetic distance of at least 6.8% in the 16S mitochondrial gene from all other known species of the genus Rhombophryne.
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Distribution: This species has only been found at high altitude in the montane forests of the Sorata massif in north Madagascar. Its distinctiveness leads us to hypothesize that it has never been found elsewhere and misidentified, so it may be microendemic to this small area. Additional surveys are required in areas in and around Sorata to identify its full distribution.
Ecology: Both specimens described here were captured in the early evening on the ground along a path through primary montane forest. The stomachs of both specimens contained remains of several small insects (mostly Coleoptera) and a spider (possibly belonging to the family Salticidae), mixed with moss, suggesting an opportunistic diet of arthropods. Calls of this species are unknown. The female holotype had more than twenty immature oocytes with the largest having diameters ranging from 1.3 to 1.6 mm. As a member of the Cophylinae, it is likely that R. longicrus lays its eggs away from running water or large water bodies, and has endotrophic tadpoles.
Etymology: The species epithet is an invariable noun in apposition to the genus name, derived from the Latin words longus (meaning long), and crus (meaning leg), and refers to the unusually long legs of this species.
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| Rhombophryne longicrus sp. n. in life. dorsolateral view of the holotype ZSM 1630/2012 |
Mark D. Scherz, Andolalao Rakotoarison, Oliver Hawlitschek, Miguel Vences and Frank Glaw. 2015. Leaping towards A Saltatorial Fifestyle? An Unusually Long-legged New Species of Rhombophryne (Anura, Microhylidae) from the Sorata Massif in northern Madagascar. Zoosystematics & Evolution 91(2): 105-114. DOI: 10.3897/zse.91.4979
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