''Thorius'', also known as minute salamanders,
pigmy salamanders, or Mexican pigmy salamanders, is a genus of
salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten ...
s in the family
Plethodontidae
Plethodontidae, or lungless salamanders, are a family of salamanders. Most species are native to the Western Hemisphere, from British Columbia to Brazil, although a few species are found in Sardinia, Europe south of the Alps, and South Korea. In ...
. They are
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...
to Mexico and found in southern
Veracruz
Veracruz (), formally Veracruz de Ignacio de la Llave (), officially the Free and Sovereign State of Veracruz de Ignacio de la Llave ( es, Estado Libre y Soberano de Veracruz de Ignacio de la Llave), is one of the 31 states which, along with Me ...
and
Puebla
Puebla ( en, colony, settlement), officially Free and Sovereign State of Puebla ( es, Estado Libre y Soberano de Puebla), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its cap ...
to
Guerrero
Guerrero is one of the 32 states that comprise the 32 Federal Entities of Mexico. It is divided in 81 municipalities and its capital city is Chilpancingo and its largest city is Acapulcocopied from article, GuerreroAs of 2020, Guerrero the pop ...
and
Oaxaca
Oaxaca ( , also , , from nci, Huāxyacac ), officially the Free and Sovereign State of Oaxaca ( es, Estado Libre y Soberano de Oaxaca), is one of the 32 states that compose the political divisions of Mexico, Federative Entities of Mexico. It is ...
.
''Thorius'' is the most species-rich tropical salamander genus relative to its distribution area (''
Bolitoglossa
''Bolitoglossa'' is a genus of lungless salamanders, also called mushroom-tongued salamanders, tropical climbing salamanders, or web-footed salamanders, in the family Plethodontidae. Their range is between northern Mexico through Central Americ ...
'' and ''
Pseudoeurycea
''Pseudoeurycea'' is a genus of salamander in the family Plethodontidae. The members of this genus are commonly known as the false brook salamanders. They are found in Mexico and Guatemala.
In order to preserve ''Ixalotriton'' and ''Bolitoglossa ...
'' have many more species but also much wider distribution areas). It is not uncommon for two or even three species to occur in the same place. In such cases, species have diverged in terms of body size and dentition, apparently facilitating niche differentiation.
The members of this genus are characterized by a small body — some species are less than in snout–vent length (tail roughly doubles the total body length). Their extreme miniaturization is accompanied by determinate growth and skeletal reduction. Their skeleton also shows unique features, such as
ossification
Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...
s of many elements that remain
cartilaginous
Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck and ...
in other salamanders. Consequently, they are easy to distinguish from other salamanders. In contrast, they tend to be similar in appearance, making it difficult to distinguish species.
However, molecular genetic methods have greatly facilitated identification of new species.
Species
As of November 15, 2016, this genus is composed of the following 29 species:
PeerJ: Three new species of miniaturized tropical salamanders are already endangered;
References
{{Taxonbar, from=Q740923
Endemic amphibians of Mexico
Amphibian genera
Taxa named by Edward Drinker Cope
Taxonomy articles created by Polbot