Brookesia nana
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Brookesia nana ( |
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| Glaw , Köhler , Hawlitschek , Ratsoavina , Rakotoarison , Scherz & Vences , 2021 |
Brookesia nana is a species of the stubby-tailed chameleon (Brookesiinae) from northern Madagascar . With a total body length of around 22 to 29 mm, the species is possibly one of the smallest reptiles in the world. Their distribution area is in the Sorata massif , where the speciesoccursin the mountain rainforest . So far only two specimens of Brookesia nana have been found, which is why nothing more is known about the way of life of the animals.
Both animals were collected as part of an expedition in 2012 and described as a new species in 2021. Together with its sister species Brookesia karchei and a number of similarly small Brookesia species, it forms the subgenus Evoluticauda . In the absence of findings, there is no reliable knowledge about the size and conservation status of the population. Like other chameleon species in Madagascar, Brookesia nana is likely to be endangered by intensive logging and the associated loss of habitat.
Research history and etymology
Brookesia nana is so far (as of January 28, 2021) only known from two individuals, an adult male ( holotype ZSM 1660/2012) and an adult female ( paratype UADBA-R / FGZC 3752). Both specimen copies were discovered in the Sorata massif in northern Madagascar from the end of November to the beginning of December 2012 and described for the first time in 2021 by Frank Glaw , Jörn Köhler , Oliver Hawlitschek , Fanomezana M. Ratsoavina , Andolalao Rakotoarison , Mark D. Scherz and Miguel Vences .
The additional species is derived from the nominative singular of the Latin noun nana with the meaning "dwarf".
features
Brookesia nana is an extremely small member of the genus Brookesia . The male holotype specimen has a head-torso length of 13.5 mm with a total length of 21.6 mm. The female (paratype) is slightly larger with a head-torso length of 19.2 mm and a total length of 28.9 mm. The fully developed hemipenes of the male and developing eggs of the female prove that both specimens are not juveniles, but sexually mature adults .
Males show a pale brown basic color with somewhat lighter, beige-colored spots on the back, which expand into four indistinctly defined stripes in the area of the upper flanks. The basic pattern is occasionally interspersed with small, blackish spots and tubercles . Another beige-colored stain is present in the front area of the head. Two dark stripes run from the eye to the corner of the mouth. The outside of the limbs is slightly darker than the body and marbled brown to gray. The eyelids have dark stripes. The iris is dark red.
The basic color of the female is brown, interspersed with darker colored tubercles, dots and spots. There are no signs of patterning, as in the male.
On the basis of the small body size, the relatively short tail, rows of tubercles that run dorsolaterally along the spine, as well as a thorn-like appendage in the hip area ( English pelvic spine ), the species can be assigned to the genus Brookesia . Brookesia nana differs from other members of the genus in that it is extremely small and has a very short, non-spiked tail compared to the length of the head and body. In addition, the species has a thorn-like extension in the hip area instead of the typical "hip shield" (English pelvic shield ). The pale brown basic color with only a few darker accents and the lack of spines in the apical area of the Hemipenes also make the animals stand out from their closest relatives.
Systematics
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| Systematic position of Brookesia nana within the Evoluticauda simplified according to Glaw et al. (2021) |
Based on its mitochondrial DNA , Brookesia nana can be phylogenetically classified together with around a dozen other species in the subgenus Evoluticauda . This clade , which split off from the rest of the Brookesia genus around 43 million years ago in the Eocene, brings together chameleons that are as small as Brookesia nana . Within this group, Brookesia karchei is the closest and, with a total length of more than 50 mm, the largest relative of the species. Species such as B. micra , B. minima , B. tedi and B. tuberculata , which have comparatively small body dimensions, are not closely related . Whether B. nana is a “typical” representative of a group that has turned out to be extremely small with a few exceptions or whether the strong dwarfism of the Evoluticauda species has developed several times independently of one another is open in view of these relationships.
The adjacent cladogram shows in a simplified form the systematic position of Brookesia nana within the subgenus Evoluticauda based on molecular genetic data according to Glaw et al. , 2021.
Inventory and status
Brookesia nana is one of around 14% of the recent lizard species (as of 2021) that are only known from where they were first found. In view of this poor location, it is hardly possible to draw reliable conclusions about the size and development of the species population. However, it is not unlikely that B. nana only inhabits an extremely limited area: This would at least correspond to the previous knowledge about other dwarfs of the genus Brookesia . A strong variation in height of the occurrences would therefore not be expected. At the time of the first discovery, the rainforest in the Sorata massif was already in decline. Especially in valleys it gives way to agricultural areas; but also in higher altitudes there was increased clearing up to 2012. In the meantime, the Sorata massif has received protection status as part of the COMATSA North Reserve, but there is currently no overview of the habitat development in the area. Frank Glaw and his co-authors propose a classification as critically endangered ' critically endangered ' by the IUCN as soon as possible in view of the narrowly delimited area, the lack of sites and the decline in potential habitat .
Web links
Individual evidence
- ↑ a b c d e f g Frank Glaw, Jörn Köhler, Oliver Hawlitschek, Fanomezana M. Ratsoavina, Andolalao Rakotoarison, Mark D. Scherz, Miguel Vences: Extreme miniaturization of a new amniote vertebrate and insights into the evolution of genital size in chameleons . In: Scientific Reports . Volume 11, 2021, Article Number 2522, doi : 10.1038 / s41598-020-80955-1 .
- ↑ Glaw et al. 2021, pp. 5 & 10.
- ↑ Glaw et al. 2021, pp. 8 & 9.