''Schistometopum thomense'' is a species of

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

in the family

Dermophiidae The Dermophiidae are a family of neotropical caecilians. They are found in Central and South America, and Africa. Like other caecilians, they superficially resemble worms or snakes. They are the only viviparous caecilians (species that give bi ...

endemic Endemism is the state of a species being found only 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 foun ...

São Tomé São Tomé is the capital and largest city of the Central African island country of São Tomé and Príncipe. Its name is Portuguese for " Saint Thomas". Founded in the 15th century, it is one of Africa's oldest colonial cities. History Álv ...

and

Ilhéu das Rolas Ilhéu das Rolas (also: ''Ilheu Gago Coutinho'') is an islet in the African island nation of São Tomé and Príncipe. It lies on the Equator, off the southern tip of São Tomé Island, separated by Canal das Rolas. Its maximum elevation is . I ...

. This species may be referred to as the São Tomé caecilian (with various spellings of the island's name), as the Agua Ize caecilian, or as the island caecilian, or by the local name of ''cobra bobo''.Species of the week: Cobra Bobo
/ref> It is found in most soils on São Tomé, from tropical moist lowland

forest A forest is an ecosystem characterized by a dense ecological community, community of trees. Hundreds of definitions of forest are used throughout the world, incorporating factors such as tree density, tree height, land use, legal standing, ...

s to coastal

coconut The coconut tree (''Cocos nucifera'') is a member of the palm tree family (biology), family (Arecaceae) and the only living species of the genus ''Cocos''. The term "coconut" (or the archaic "cocoanut") can refer to the whole coconut palm, ...

plantation Plantations are farms specializing in cash crops, usually mainly planting a single crop, with perhaps ancillary areas for vegetables for eating and so on. Plantations, centered on a plantation house, grow crops including cotton, cannabis, tob ...

s. It is absent only from the driest northern areas of the island. Schistometopum thomense 96192876

It is typically around 30 cm (12 in) in length, and is often bright yellow. The size of ''S. thomense'' can vary throughout São Tomé, however, and it is the only known caecilian to follow Bergmann's rule, which states that a decreasing temperature due to factors such as increasing altitude will cause an increase in the body size of endothermic vertebrate species. The island of São Tomé is a massive shield volcano, and it therefore has differing altitudes throughout the island, potentially resulting in the size diversity of ''S. thomense.''

Synonyms

The species has been described under the following synonyms: *''Siphonops thomensis'' — Bocage, 1873 *''Siphonops brevirostris'' — Peters, 1874 *''Dermophis brevirostris'' — Peters 1880 *''Dermophis thomensis'' — Peters, 1880 *''Schistometopum thomense'' — Parker, 1941 *''Schistometopum ephele'' — Taylor, 1965 *''Schistometopum brevirostris'' — Taylor, 1965 *''Schistometopum brevirostre'' — Taylor, 1968

Phylogenetics

Interfamilial and intergeneric relationships of the São Tomé caecilian are well supported by analyses of mitochondrial (mtDNA) sequence data. At the genus level, ''

Schistometopum ''Schistometopum'' is a genus of amphibian in the family Dermophiidae. ''S. thomense'' is only known from two islands in the Bight of Benin The Bight of Benin, or Bay of Benin, is a bight in the Gulf of Guinea area on the western African coas ...

'' was recovered as sister to ''Dermophis,'' a genus of caecilians found in South America; these two genera are paired in a clade. Within ''Schistometopum,'' Wilkinson et al. (2003) found that ''S. thomense'' is sister to '' S. gregorii'' (an East African species distributed in

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

and

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

) which was also determined to be its lone congener. This congeneric grouping was later supported by sequence analyses of thirteen complete mitochondrial genomes from twelve caecilian species. However, species-level phylogenetic relationships of ''S. thomense'' have yet to be fully determined, given the recent discovery of ''Schistometopum ephele'', a cryptic species on São Tomé Island. Available information on species-level relationships (inclusive of ''S. ephele'') is limited to a single line of evidence that the common ancestor of ''S. thomense'' and ''S. ephele'' diverged from its sister species (''S. gregorii'') ~1 Ma. Further information is needed to fully understand phylogenetic relationships at the species level. Zooming out to higher-level phylogenetic relationships, ''S. thomense'' was historically placed in the

Caeciliidae Caeciliidae is the family of common caecilians. They are found in Central and South America. Like other caecilians, they superficially resemble worms or snakes. Although they are the most diverse of the caecilian families, the caeciliids do ha ...

, a highly unresolved grouping that was paraphyletic with respect to the

Typhlonectidae Typhlonectidae, also known as aquatic caecilians or rubber eels, are a family of caecilians found east of the Andes in South America. They are viviparous animals, giving birth to young that possess external gills. Of the five extant genera in th ...

and the

Scolecomorphidae The Scolecomorphidae (from , 'wormlike' and , 'form') are a family of caecilians also known as tropical caecilians, buried-eyed caecilians, or African caecilians. They are found in Cameroon in West Africa, and Malawi and Tanzania in East Africa ...

. This classification remained until 2011, when a nine-family level

taxa In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

(

Rhinatrematidae Rhinatrematidae is a family of caecilians, also known as the Neotropical tailed caecilians, American tailed caecilians. or beaked caecilians. They are found in the equatorial countries of South America. They are usually regarded as the most basa ...

Ichthyophiidae The Ichthyophiidae are the family of Asiatic tailed caecilians or fish caecilians found in South and Southeast Asia as well as southernmost China. They are primitive caecilians, lacking many of the derived characters found in the other families ...

, Scolecomorphidae,

Herpelidae Herpelidae are a family of caecilians, sometimes known as the African caecilians. They are found in Sub-Saharan Africa. Like other caecilians, they superficially resemble worms or snakes. They are the sister group to the newly discovered Chikili ...

, Caeciliidae, Typhlonectidae, Indotyphlidae,

Siphonopidae The Siphonopidae are the family of common caecilians. They are found in Central and South America. Like other caecilians, they superficially resemble worms or snakes. They are the sister group to Dermophiidae, also of South America. Siphonopi ...

, and

) for caecilians that resolved the paraphyly of Caeciliidae and placed the genus ''Schistometopum'' in the Dermophiidae ('' Dermophis, Geotrypetes,

Gymnopis ''Gymnopis'' is a Central America Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the ...

,'' and ''Schistometopum''), sister to Siphonopidae, was proposed. Subsequent studies on caecilians used this nine-family classification.

References

{{Taxonbar, from=Q2237200 thomense Endemic fauna of São Tomé Island Ilhéu das Rolas Amphibians described in 1873 Taxonomy articles created by Polbot