Mecistocephalus Punctifrons

''Mecistocephalus'' is the largest genus of centipedes in the family Mecistocephalidae, with about 140 species. This genus is among the most diverse and widespread of all the genera in the order Geophilomorpha. The British entomologist George Newport first proposed this genus in 1843 to contain a group of centipedes marked by an unusual elongation of the head.

Description

Centipedes in this genus range from 2 cm to 10 cm in length. The head, forcipular segment, and their appendages are often elongated, with a head that is obviously longer than wide. A pair of sclerotized teeth (spicula) project from the pleurites on the sides of the head.

The coxosternite of the first maxillae is divided down the middle by a longitudinal suture, but the coxosternite of the second maxillae is undivided. The second maxillae reach beyond the first maxillae and are well developed with a simple claw. The forcipular tergum is slightly wider than long and divided down the middle by a longitudinal furrow. Each of the first articles of the forcipules often features a pair of denticles, one distal and the other near the middle of the article. The body tapers distinctly toward the posterior. The first pair of legs are markedly reduced in size. The ultimate legs are slender and do not exhibit sexual dimorphism.

Centipedes in the genus ''Mecistocephalus'' usually have 45 to 51 pairs of legs, but some have more, up to as many as 101 leg pairs. Most species in this genus have 49 pairs of legs (e.g., '' M. punctifrons'' and '' M. pallidus''), but other species have 51 pairs (e.g., '' M. evansi'' and '' M. lifuensis''), 47 pairs (e.g., '' M. angusticeps'' and '' M. tahitiensis''), or 45 pairs (e.g., '' M. nannocornis'' and '' M. spissus''). Intraspecific variation in the number of leg-bearing segments within each sex has been recorded among the species with the greatest number of legs in this genus: '' M. diversisternus'', which has 57 or 59 leg pairs, '' M. japonicus'', which has 63 or 65 leg pairs, and '' M. microporus'', which has odd numbers of leg pairs ranging from 93 to 101, the maximum number recorded in the family Mecistocephalidae.

Phylogeny

A phylogenetic analysis of the family Mecistocephalidae using morphological features places the genus ''Mecistocephalus'' in the subfamily Mecistocephalinae along with the genera '' Tygarrup'', '' Krateraspis'', and '' Takashimaia.'' The genera in this subfamily share a set of distinctive traits. For example, these diagnostic features include a body that tapers toward the posterior end, a cephalic plate that is evidently longer than wide, a divided coxosternum of the first maxillae, an undivided coxosternum of the second maxillae, well developed second maxillae that each feature a reduced claw, and a forcipular tergum that is slightly wider than long.

Phylogenetic analysis based on morphology also places the genus ''Tygarrup'' on the most basal branch of a phylogenetic tree in the subfamily Mecistocephalinae, with the genus ''Krateraspis'' on the second most basal branch and the genus ''Takashimaia'' on the third most basal branch. This analysis leaves the species of ''Mecistocephalus'' in a clade forming a sister group for ''Takashimaia'', which emerges as the genus most closely related to ''Mecistocephalus''. These two genera share an especially extensive set of traits: For example, unlike the other genera in the same subfamily, both ''Mecistocephalus'' and ''Takashimaia'' feature a spiculum on each side of the head. These two genera can be distinguished, however, based on other traits. For example, the second maxillae extend beyond the first maxillae in the genus ''Mecistocephalus'' but not in the genus ''Takashimaia''.

Phylogenetic analysis based on morphology also indicates that the common ancestor of the subfamily Mecistocephalinae had 45 leg pairs, with species featuring more leg pairs evolving through a process that added leg pairs incrementally. For example, this analysis indicates that the common ancestor of the genus ''Mecistocephalus'' also had 45 leg pairs and places extant species with 45 leg pairs in a clade on the most basal branch of a phylogenetic tree in this genus. These species form a sister group for a clade containing all other ''Mecistocephalus'' species, which share a common ancestor with 47 leg pairs. The second most basal branch in this genus contains a clade with 47 leg pairs, which forms a sister group for a clade containing the remaining ''Mecistocephalus'' species, which share a common ancestor with 49 leg pairs. Thus, ''Mecistocephalus'' species with more than 49 leg pairs evolved from a common ancestor with 49 leg pairs, which in turn evolved from an ancestor with 47 leg pairs, which in turn evolved from an ancestor with 45 leg pairs.

Distribution

This genus is distributed over a large geographic range. Centipedes in this genus are found mainly in tropical and subtropical regions of south and east Asia, with some also found in temperate areas and in the Americas. Maximum diversity in terms of species occurs in the region of Japan and southeast Asia.

Species

There are about 140 valid species, including:

* '' Mecistocephalus angusticeps'' (Ribaut,1914)
* '' Mecistocephalus apator'' Chamberlin, 1920
* '' Mecistocephalus brevisternalis'' Takakuwa, 1934
* '' Mecistocephalus capillatus'' Takakuwa, 1935
* '' Mecistocephalus castaneiceps'' Haase, 1887
* '' Mecistocephalus ciliatus'' Takakuwa, 1942
* '' Mecistocephalus collinus'' Verhoeff, 1937
* '' Mecistocephalus consocius'' Chamberlin, 1944
* ''Mecistocephalus diversisternus'' (Silvestri, 1919)
* ''Mecistocephalus erythroceps'' Chamberlin, 1920
* ''Mecistocephalus evansi'' Brölemann, 1922
* '' Mecistocephalus furculigera'' (Verhoeff, 1925)
* '' Mecistocephalus gigas'' Haase, 1887
* '' Mecistocephalus glabridorsalis'' Attems, 1900
* '' Mecistocephalus gracilis'' (Verhoeff, 1925)
* '' Mecistocephalus hebrides'' (Chamberlin,1944)
* '' Mecistocephalus heteropus'' Humbert, 1865
* ''Mecistocephalus japonicus'' Meinert, 1886
* '' Mecistocephalus kabasanus'' (Chamberlin, 1920)
* '' Mecistocephalus kurandanus'' Chamberlin, 1920
* '' Mecistocephalus labasanus'' (Chamberlin, 1920)
* ''Mecistocephalus lifuensis'' Pocock, 1899
* '' Mecistocephalus magister'' Chamberlin, 1939
* '' Mecistocephalus manokwarius'' Chamberlin, 1944
* '' Mecistocephalus marcusensis'' Miyosi, 1953
* '' Mecistocephalus mater'' (Verhoeff, 1925)
* '' Mecistocephalus modestus'' (Silvestri,1919)
* '' Mecistocephalus nagasaunus'' Chamberlin, 1920
* ''Mecistocephalus nannocornis'' Chamberlin, 1920
* '' Mecistocephalus nigriceps'' Chamberlin, 1920
* '' Mecistocephalus ocanus'' Chamberlin, 1946
* '' Mecistocephalus okabei'' Takakuwa, 1942
* '' Mecistocephalus ongi'' Takakuwa, 1934
* '' Mecistocephalus porosus'' Haase, 1887
* '' Mecistocephalus pseustes'' (Chamberlin,1939)
* ''Mecistocephalus punctifrons'' Newport, 1843
* '' Mecistocephalus siaronus'' (Chamberlin, 1920)
* '' Mecistocephalus simplex'' Chamberlin, 1920
* '' Mecistocephalus smithii'' Pocock, 1895
* '' Mecistocephalus somonus'' (Chamberlin, 1920)
* ''Mecistocephalus spissus'' Wood, 1862
* '' Mecistocephalus subgigas'' (Silvestri,1919)
* '' Mecistocephalus subinsularis'' (Silvestri, 1919)
* ''Mecistocephalus tahitiensis'' Wood, 1862
* '' Mecistocephalus tsenapus'' Chamberlin, 1944
* '' Mecistocephalus turucanus'' (Chamberlin, 1920)
* '' Mecistocephalus uncifer'' (Silvestri,1919)
* '' Mecistocephalus waikaneus'' Chamberlin, 1953
* '' Mecistocephalus waipaheenas'' (Chamberlin, 1953)
* '' Mecistocephalus zygethus'' Chamberlin, 1939

References

{{Taxonbar, from= Q10578924

Centipede genera
Animals described in 1843
Taxa named by George Newport