The Smallest Lizard

Brookesia micra from Nosy Hara, northern Madagascar. (A) adult male on black background, showing orange tail colouration; (B) juvenile on finger tip; (C) juvenile on head of a match; (D) habitat along a small creek on western flank of Nosy Hara, where part of the type series was collected. This is Figure 8 from the original paper.
Size determines much biology in living organisms: what an organism can eat and what eat its, how fast or slow an organims may loose or gain heat and water, and where an organism can or cannot hide. The largest animals tend to be well known, but the smallest may go undetected and overlooked. Until today, the smallest lizard was the gecko Sphaerodactylus ariasae with a snout-vent length of 18 mm and a total length of 33 mm.

Madagascar has about 80 (43%) of the 185 chameleons, and they are all in three genera Brookesia, Calumma, and Furcifer. Brookesia contains about 26 species of ground dwellers that forage in the leaf litter rainforest and dry deciduous forest, climbing to low perches in the vegetation for sleeping. Brookesia are typically dull brown or green, have a short non-prehensile tail that is used as “fifth leg” in walking, and are relative small in size, about 15–65 mm in body length and 25–105 mm in total length. Most species of Brookesia have very small geographic distributions, with almost half of the species known from single localities.

During recent fieldwork in northern Madagascar, Glaw and colleagues discovered several new populations assignable to the Brookesia minima group, some of which are morphologically and genetically distinct from all described species, and they describe four new species in a PLoS One artcile published today.

One of the newly discovered dwarf chameleons is striking cases of miniaturization and microendemism and suggest the possibility of a range size-body size relationship in Malagasy reptiles. The newly described Brookesia micra reaches a maximum snout-vent length in males of 16 mm, and its total length in both sexes is less than 30 mm, ranking it among the smallest amniote vertebrates in the world. With a distribution limited to a very small islet, this species may represent an extreme case of island dwarfism. Brookesia micra was found active on the ground during the day in a mosaic of eroded limestone boulders and dry forest leaf litter, and at night roosting on branches in very low vegetation (about 5–10 cm above the ground). The entire article is available on-line.

Citation
Glaw F, Köhler J, Townsend TM, Vences M (2012) Rivaling the World's Smallest Reptiles: Discovery of Miniaturized and Microendemic New Species of Leaf Chameleons (Brookesia) from Northern Madagascar. PLoS ONE 7(2): e31314. doi:10.1371/journal.pone.0031314

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