Mecistocephalus microporus

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Mecistocephalus microporus is a large soil centipede from the Philippines, notable for its unusually variable number of leg pairs. Adults can reach up to 125 mm in length, and the number of leg-bearing segments ranges from 93 to 101 pairs. This variability is rare in its family, and M. microporus was the first Mecistocephalidae species where leg number was observed to vary.

Taxonomy and discovery
- Described in 1887 by German zoologist Erich Haase from a female holotype found on Luzon, Philippines. The holotype is 125 mm long and has 101 leg pairs.
- In 1920, American biologist Ralph Chamberlin described a new species, Megethmus pluripes, based on specimens also from Luzon with 97 leg pairs, and placed it in a newly proposed genus Megethmus.
- In 2001, Italian biologists Lucio Bonato, Donatella Foddai, and Alessandro Minelli redescribed M. microporus and concluded that Megethmus pluripes is a junior synonym of M. microporus, and that Megethmus is a synonym of Mecistocephalus. They also noted leg-number variation within M. microporus and re-evaluated relationships in the group.

Where it fits and how it differs from relatives
- M. microporus belongs to the genus Mecistocephalus within the Mecistocephalidae family. A closely related species is Mecistocephalus multidentatus from Taiwan, which has far fewer leg pairs (about 49) and different mouthparts.
- Both species share several features typical of Mecistocephalus, such as a head longer than wide and a tapering body. However, M. microporus shows more variation in leg numbers (93–101) and has specific differences in mouthparts and certain plate features that distinguish it from M. multidentatus.

Key distinguishing traits (highlights)
- Leg count: M. microporus has 93–101 leg-bearing segments; M. multidentatus has about 49.
- Plagulae (clypeal area) in M. microporus bear micropores; in M. multidentatus this feature is not present.
- Mandible teeth: M. microporus has about 6 teeth on the first lamella and around 15 on an intermediate lamella; M. multidentatus has more (about 10 on the first lamella and 30–40 on the intermediate lamella).
- These and other subtle head and trunk features help separate M. microporus from its close relative.

Summary in brief
- Species: Mecistocephalus microporus
- Habitat: Soil-dwelling centipede in the Philippines (Luzon and Cebu areas noted)
- Size: Up to about 125 mm
- Leg variation: 93–101 leg pairs, unusually variable for its family
- Taxonomic notes: Described 1887; Megethmus pluripes (1920) later merged as a synonym; Megethmus synonymized with Mecistocephalus in 2001
- Relation to other species: Closest notable relative is M. multidentatus; differs in leg number, plagulae pores, and mandible teeth, among other traits
- Evolutionary note: Cladistic analyses place M. microporus in a Mecistocephalus clade with a close relative, suggesting an ancestral lineage with fewer leg pairs that evolved to the current higher count.