Mecistocephalidae

Species of this family are characterized by an elongated head with lateral margins converging backwards; first maxillae with a relatively elongate coxosternite and coxal projections that are much wider than the telopodites, with both appendages ending with a distinctly hyaline part; second maxillae with small simple claws; an elongate forcipular coxosternite with pleurites projecting anteriorly into scapular points and displaced dorsally so that the coxopleural sutures run anteriorly on the dorsal side; metatergites on the posterior part of the trunk that are distinctly longer than those on the anterior part.

This family differs from all other geophilomorphs insofar as the number of segments in mecistocephalids is generally fixed within each species and the same for each sex.{{Cite journal |last1=Minelli |first1=Alessandro |last2=Bortoletto |first2=Stefano |date=1988-04-01 |title=Myriapod metamerism and arthropod segmentation |url=https://doi.org/10.1111/j.1095-8312.1988.tb00448.x |journal=Biological Journal of the Linnean Society |volume=33 |issue=4 |pages=323–343 [329-330] |doi=10.1111/j.1095-8312.1988.tb00448.x |issn=0024-4066|url-access=subscription }}{{Cite journal |last1=Bonato |first1=Lucio |last2=Foddai |first2=Donatella |last3=Minelli |first3=Alessandro |date=2003 |title=Evolutionary trends and patterns in centipede segment number based on a cladistic analysis of Mecistocephalidae (Chilopoda: Geophilomorpha): Evolution of segment number in Mecistocephalidae |url=http://doi.wiley.com/10.1046/j.1365-3113.2003.00217.x |journal=Systematic Entomology |language=en |volume=28 |issue=4 |pages=539–579 |doi=10.1046/j.1365-3113.2003.00217.x|url-access=subscription }} The family includes centipedes with odd numbers of leg-bearing segments ranging from as few as 41 to as many as 101. A majority of the species in the genus Mecistocephalus have 49 pairs of legs,{{Cite journal |last1=Bonato |first1=L. |last2=Minelli |first2=A. |date=2004 |title=The centipede genus Mecistocephalus Newport 1843 in the Indian Peninsula (Chilopoda Geophilomorpha Mecistocephalidae) |url=http://www.tandfonline.com/doi/abs/10.1080/03946975.2004.10531198 |journal=Tropical Zoology |language=en |volume=17 |issue=1 |pages=15–63 |doi=10.1080/03946975.2004.10531198 |s2cid=85304657 |issn=0394-6975|url-access=subscription }} a majority so large that most species in the family Mecistocephalidae have 49 leg pairs, even though only one mecistocephalid species (Proterotaiwanella sculptulata) outside the genus Mecistocephalus shares this number.

The next most common numbers are 45 leg pairs, found in most species in the genus Tygarrup as well as in species distributed among five other genera, and 41 leg pairs, found in all species in the genera Agnostrup, Anarrup, Arrup, Nannarrup, and Partygarrupius as well as in two species of Dicellophilus;{{cite journal |last1=Bonato |first1=Lucio |last2=Dányi |first2=László |last3=Minelli |first3=Alessandro |year=2010 |title=Morphology and phylogeny of Dicellophilus, a centipede genus with a highly disjunct distribution (Chilopoda: Mecistocephalidae) |journal=Zoological Journal of the Linnean Society |volume=158 |issue=3 |pages=501–532 |doi=10.1111/j.1096-3642.2009.00557.x}} fewer mecistocephalid species have 47 leg pairs (e.g., Mecistocephalus angusticeps and M. tahitiensis) or 51 leg pairs (e.g., M. evansi and M. lifuensis),{{Cite journal |last=Evans |first=W. Edgar |last2=Brolemann |first2=Henry W. |date=1923 |title=VI.—Myriapods collected in Mesopotamia and N.W. Persia |url=https://www.cambridge.org/core/journals/proceedings-of-the-royal-society-of-edinburgh/article/abs/vimyriapods-collected-in-mesopotamia-and-nw-persia/FBE63D640959EDA3CB429CCB7C11F4AA |journal=Proceedings of the Royal Society of Edinburgh |language=en |volume=42 |pages=54–74 |doi=10.1017/S0370164600023841 |issn=0370-1646|url-access=subscription }} found only in the genus Mecistocephalus, and the other remaining numbers are even more rare (e.g., 43 leg pairs, found in Dicellophilus carniolensis).

Intraspecific variation in the number of leg-bearing segments within each sex has been recorded among the mecistocephalid species with the greatest number of legs: Mecistocephalus 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.{{Cite journal |last=Minelli |first=Alessandro |date=2020 |title=Arthropod Segments and Segmentation – Lessons from Myriapods, and Open Questions |url=http://opuscula.elte.hu/PDF/Tomus51_S2/Op_%20Minelli_Arthropod_segmentation.pdf |journal=Opuscula Zoologica (Budapest) |volume=51(S2) |pages=7–21 [10] |doi=10.18348/opzool.2020.S2.7 |s2cid=226561862}} Other mecistocephalid species with many legs are known from samples too small to provide persuasive evidence of intraspecific invariance (e.g., M. cyclops, with 57 leg pairs in the only known specimen).{{Cite journal |last1=Bonato |first1=Lucio |last2=Minelli |first2=Alessandro |date=2010 |title=The geophilomorph centipedes of the Seychelles (Chilopoda: Geophilomorpha) |url=https://islandbiodiversity.com/Phelsuma%2018-1.pdf |journal=Phelsuma |volume=18 |pages=9–38}} The mecistocephalid species Krateraspis sselivanovi has 53 leg pairs without intraspecific variation,{{Cite journal |last1=Dyachkov |first1=Yurii V. |last2=Bonato |first2=Lucio |date=2022-04-14 |title=Morphology and distribution of the Middle Asian centipede genus Krateraspis Lignau, 1929 (Chilopoda, Geophilomorpha, Mecistocephalidae) |journal=ZooKeys |language=en |issue=1095 |pages=143–164 |doi=10.3897/zookeys.1095.80806 |issn=1313-2970 |pmc=9023436 |pmid=35836682|doi-access=free }}{{Cite journal |last=Dyachkov |first=Yu. V. |date=2019 |title=New data on the family Mecistocephalidae Bollman, 1893 (Chilopoda: Geophilomorpha) from Middle Asia |url=https://kmkjournals.com/journals/AS/AS_Index_Volumes/AS_28/AS_28_3_368_373 |journal=Arthropoda Selecta |language= |volume=28 |issue=1 |pages=368–373 |doi=10.15298/arthsel.28.3.02 |s2cid=216530363 |issn=0136-006X|doi-access=free }} which may be the maximum number evidently fixed by species in the class Chilopoda.{{Cite journal |last1=Minelli |first1=Alessandro |last2=Chagas-Júnior |first2=Amazonas |last3=Edgecombe |first3=Gregory D. |date=2009 |title=Saltational evolution of trunk segment number in centipedes |url=https://onlinelibrary.wiley.com/doi/10.1111/j.1525-142X.2009.00334.x |journal=Evolution & Development |language=en |volume=11 |issue=3 |pages=318–322 [319] |doi=10.1111/j.1525-142X.2009.00334.x |pmid=19469859 |s2cid=40909871|url-access=subscription }}

This family includes the following genera distributed among three subfamilies:{{Cite web |title=ITIS - Report: Mecistocephalidae |url=https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=913871#null |access-date=2022-12-28 |website=www.itis.gov |language=en-US}}

;Subfamily Arrupinae Chamberlin, 1912

• Agnostrup Foddai, Bonato, Pereira & Minelli, 2003
• Arrup Chamberlin, 1912
• Nannarrup Foddai, Bonato, Pereira & Minelli, 2003
• Partygarrupius Verhoeff, 1939

;Subfamily Dicellophilinae Cook, 1896

• Anarrup Chamberlin, 1920
• Dicellophilus Cook, 1896
• Proterotaiwanella Bonato, Foddai & Minelli, 2002

;Subfamily Mecistocephalinae Bollman, 1893

• Krateraspis Lignau, 1929
• Mecistocephalus Newport, 1843
• Takashimaia Miyosi, 1955
• Tygarrup Chamberlin, 1914

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Category:Centipede families

Category:Geophilomorpha