Species Description: Scherz MD, CR Hutter, A Rakotoarison, JC Riemann, M-O Rödel, SH Ndriantsoa, J Glos, SH Roberts, A Crottini, M Vences, and F Glaw. 2019. Morphological and ecological convergence at the lower size limit for vertebrates highlighted by five new miniaturised microhylid frog species from three different Madagascan genera. PLoS One 14: e0213314.
© 2019 Miguel Vences (1 of 1)
The forelimb is slender and its length (sum of the hand, upper arm, and lower arm lengths) is 49% of the average snout vent length. The subarticular tubercles are single and faint. The outer metacarpal tubercle is paired and faint, while the inner metacarpal is distinct and elongated. The hands are not webbed. The first finger is reduced, and the relative length of fingers is 1 < 2 = 4 < 3. The finger tips are not expanded. The hind limbs are robust with a total length (sum of foot length, thigh length, and tibiofibular length) that is 125% of the snout vent length. The tibiofibular length specifically is 34% of the snout vent length. The lateral metatarsalia is strongly connected. The inner and outer metatarsal tubercles are thin and small, respectively, with both being indistinct. The toes have no webbing, and the first toe is highly reduced. The relative toe length is 1 < 2 < 5 < 3 < 4. The dorsal skin is smooth (both in preservative and in life), but in life there are also scattered tubercles and a distinct ridge above the scapular region. The ventral skin is granular in live frogs (Scherz et al. 2019).
Rhombophryne proportionalis has no clavicles, which distinguishes it from most other miniature frogs. However, S. achillei, S. analanjirofo, S. contumelia, S. davidattenboroughi, S. makira, S. obscoena, and some specimens of S. tridactyla similarly have no clavicles. Rhombophryne proportionalis can be further distinguished by a dark colouration on the lateral surface of the head with a distinct color border, as well as fewer reduced fingers and toes. Other adult species in its genus, Rhombophryne, can be distinguished by their greater size. Rhombophryne proportionalis also has a unique call, different from other frogs in Madagascar. Its call is a rapid series of high pitched tonal notes (Scherz et al. 2019).
In alcohol, the dorsum is a chocolate brown color that is darker on the head, with a faint dark brown line that runs from the inguinal region anteriorly toward the eye. Laterally, the head has a distinct color border to the dorsum. The head is a darker brown and its border is defined by the supratympanic fold. The dorsal skin of the leg has a dark brown crossband on the shank. The color border between the flank and venter is indistinct. The venter is brown with cream flecks, getting slightly darker and having fewer flecks on the chin. The legs and arms have the same color ventrally as the abdomen. The bottom of the foot is dark brown down the medial half. Coloration is the same in life, just more vibrant (Scherz et al. 2019).
Morphologically, there is little variation between the three specimens studied. However, sometimes the supratympanic fold is less curved and more of a straight line from the eye to above the arm. The coloration of the three specimens is fairly consistent as well. Dorsolateral lines are sometimes not present, and instead can be broken into spots above the suprascapular region and lines in the inguinal region (Scherz et al. 2019).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Madagascar
Life History, Abundance, Activity, and Special Behaviors
Rhombophryne proportionalis call during the day on the ground in open, shrubby landscape. In some areas, several R. proportionalis can be heard calling in a chorus. Its call is a rapid series of high pitched tonal notes. The calls are repeated at long and irregular intervals, with each call consisting of a series of 9 – 17 notes (Scherz et al. 2019).
Trends and Threats
The species is named with the epithet “proportionalis,” meaning “proportional” in Latin. This is in reference to the comparatively proportional dwarfism of R. proportionalis (Scherz et al. 2019).
Scherz, M. D., Hutter, C. R., Rakotoarison, A., Riemann, J. C., Rödel, M. O., Ndriantsoa, S. H., et al. (2019). "Morphological and ecological convergence at the lower size limit for vertebrates highlighted by five new miniaturised microhylid frog species from three different Madagascan genera." PLoS ONE, 14(3). [link]
Originally submitted by: Jessica Pan (2022-03-10)
Description by: Jessica Pan (updated 2022-03-10)
Distribution by: Jessica Pan (updated 2022-03-10)
Life history by: Jessica Pan (updated 2022-03-10)
Trends and threats by: Jessica Pan (updated 2022-03-10)
Comments by: Jessica Pan (updated 2022-03-10)
Edited by: Ann T. Chang (2022-03-10)
Species Account Citation: AmphibiaWeb 2022 Rhombophryne proportionalis <https://amphibiaweb.org/species/8990> University of California, Berkeley, CA, USA. Accessed Aug 8, 2022.
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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 8 Aug 2022.
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