Mecistocephalus lifuensis

Mecistocephalus lifuensis is a species of soil centipede in the Mecistocephalidae family.^[1][2][3] This centipede is found in New Caledonia, a French overseas territory in Melanesia.^[4][5] This species is notable for featuring 51 pairs of legs rather than the 49 leg pairs usually observed in the genus Mecistocephalus.^[6][7]

Mecistocephalus lifuensis
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Myriapoda
Class:	Chilopoda
Order:	Geophilomorpha
Family:	Mecistocephalidae
Genus:	Mecistocephalus
Species:	M. lifuensis
Binomial name
Mecistocephalus lifuensis Pocock, 1899

Discovery and taxonomy

This species was first described in 1898 by the British zoologist Reginald Innes Pocock.^[8] He based the original description of this species on type material found on Lifou Island in New Caledonia.^[8][9] In 1923, the French zoologist Henri Ribaut placed this species in the genus Lamnonyx,^[5] which Pocock and others deemed to be a junior synonym for Mecistocephalus.^[8][9] Authorities now agree that Mecistocephalus is the valid name for Lamnonyx.^[10][11]

Phylogeny

A phylogenetic analysis of the family Mecistocephalidae based on morphology places M. lifuensis in a clade nested among Mecistocephalus species with 49 leg pairs in a phylogenetic tree. This analysis indicates that the ancestor of M. lifuensis had 49 leg pairs. Thus, this species evolved from this ancestor through a process that added two leg-bearing segments and two leg pairs.^[4]

Description

This species has 51 pairs of legs and can reach 41 mm in length.^[5] The body is yellow, but the head is a reddish shade of brown.^[8] The head is elongated and narrower at the back, with a posterior margin only 0.65 as wide as the anterior margin. The head is 1.75 times as long as its width at the front. The sternite of the forcipular segment is slightly wider than long and features a wide groove down the middle. The first article of each forcipule features two tubercles on the inner margin, each intermediate article features one tubercle on the inner margin, and the claw features a small denticle at the base.^[5]

The first pair of legs are short, only two-thirds as long as the legs of the second pair.^[5] Each sternite on the anterior segments features a groove down the middle that is Y-shaped.^[8] The fork in this groove disappears at about the 23rd segment.^[5] The basal element of each of the ultimate legs feature 20 large scattered pores.^[8] The ultimate legs are slender and lack claws.^[5] The telson is shaped like a triangle pointed toward the posterior end, with a broad base and anal pores.^[8][5][12]

This species shares many traits with other centipedes in the genus Mecistocephalus. For example, like other species in this genus, M. lifuensis features a head with a transverse frontal line, a coxosternite of the first maxillae that is divided down the middle by a suture, and an undivided coxosternite of the second maxillae.^[4] Furthermore, like other species in this genus, M. lifuensis features a head that is evidently longer than wide and slender ultimate legs. Unlike most other species of Mecistocephalus, however, M. lifuensis features 51 leg pairs rather than the 49 pairs usually observed in this genus.^[5][7]

Although some other species of Mecistocephalus also have 51 leg pairs, these species may be distinguished from M. lifuensis based on other traits. For example, like the species M. lifuensis, the species M. erythroceps is found in Oceania and features not only 51 leg pairs but also a bifurcated median groove on the sternites. This bifurcation is faint in M. erythroceps, however, and thus less distinct and more obscure than in M. lifuensis.^[9][13]

Distribution

The species M. lifuensis is found in New Caledonia, where it has been recorded in the commune of Koné in the North Province on the island of Grande Terre as well as in the communes of Lifou and Maré in the Loyalty Islands Province.^[5][8][4]