Glomerida is an order of pill-millipedes found primarily in the Northern Hemisphere. They superficially resemble pill-bugs or woodlice, and can enroll into a protective ball. They have twelve body segments, 17 to 19 pairs of legs, and males have enlarged rear legs involved in mating. The order includes about 30 genera and at least 280 species, including Glomeris marginata, the common European pill-millipede. The order contains members in Europe, South-east Asia and the Americas from California to Guatemala. Although historically considered closely related with the similar sphaerotheriidans that also enroll, some DNA evidence suggest they may be more closely related to glomeridesmidans, a poorly known order that does not enroll.
Temporal range: Cenomanian–Recent
Plesiocerata Verhoeff, 1910
Glomeridans are small, oval-shaped millipedes reaching up to 20 mm (0.79 in) long. Like the Sphaerotheriida (so-called Giant Pill-millipedes), they are capable of enrolling into a ball ("volvation"), a trait also shared with the unrelated pillbugs (Oniscidean crustaceans). They possess 12 body segments, although the second and third dorsal plates (tergites) may be fused, and the 11th tergite may be small or partially hidden to appear as 11 segments. The last tergite is enlarged and shield like. The head is relatively large and round, possessing long, slender antennae, and horseshoe-shaped Tömösváry organs. Eyes may be present or absent. The collum (first segment behind the head) is small while the second tergite is greatly enlarged. Defensive glands (ozopores) are situated dorsally, in contrast to the lateral ozopores of most other millipedes. Males and females differ in the number of leg pairs: males have 19 while females have 17. Additionally, in mature males the last leg pair is modified into clasping appendages known as telopods.
Glomerida is predominantly a northern hemisphere group. It contains members in Europe, North Africa, Central and Southeast Asia, and the Americas. Four species are present in the British Isles. Only in Southeast Asia do any members cross the equator, extending as far south as Indonesia. In the western hemisphere, Glomeridans occur in three disparate areas: an eastern, somewhat Appalachian region from Kentucky to northern Florida and Mississippi; a California region from the San Francisco Bay to the Monterey Bay, and a neotropical region from eastern Mexico (Nuevo León) to central Guatemala. Numerous undescribed fossils are known from the Cenomanian aged Burmese amber, which constitue the oldest known records of the order, though the group probably originated much earlier.
Glomerida contains approximately 30 genera, but the relationship of these to each other is debated. Some authors divide the order into three families, the large family Glomeridae, Glomeridellidae, and Trachysphaeridae, while others classify the order into a more elaborate system of subfamilies and tribes and recognize the families Glomeridellidae, and Glomeridae and Protoglomeridae. Estimates of numbers of species range from 280 to 450. The genus Glomeris is the largest, containing at least 100 species and many more subspecies or varieties.
Glomerida is traditionally classified along with Sphaerotheriida in the superorder Oniscomorpha, which contains short-bodied millipedes capable of volvation. Oniscomorphs are united with the poorly known Glomeridesmida in the infraclass Pentazonia, which is characterized by posterior telopods and relatively short bodies, and is the sister group to the Helminthomorpha, or "worm-like" millipedes. This classification is supported by morphological similarities. However, some studies based on DNA sequence comparisons have suggested that Glomerida is more closely related to Glomeridesmida than to Sphaerotheriida, a hypothesis which would imply the enrolling behavior evolved twice or was lost in the ancestors of Glomeridesmidans.
- "Diagnostic features of Millipede Orders" (PDF). Milli-PEET Identification Tables. The Field Museum, Chicago. Retrieved 25 October 2013.
- "Putative apomorphies of millipede clades" (PDF). Milli-PEET: Millipede Systematics. The Field Museum, Chicago, IL. 26 September 2006.
- "Biogeography of millipede families" (PDF). Field Museum of Natural History. Retrieved December 27, 2016.
- "Millipedes of Britain and Ireland: systematic check list". British Myriapod and Isopod Group. Retrieved December 27, 2016.
- Shelley, R. M., & Golovatch, S. I. (2011). "Atlas of Myriapod Biogeography. I. Indigenous Ordinal and Supra-Ordinal Distributions in the Diplopoda: Perspectives on Taxon Origins and Ages, and a Hypothesis on the Origin and Early Evolution of the Class". Insecta Mundi. 158: 1–134.CS1 maint: uses authors parameter (link)
- Wesener, Thomas; Moritz, Leif (2018-12-17). "Checklist of the Myriapoda in Cretaceous Burmese amber and a correction of the Myriapoda identified by Zhang (2017)". Check List. 14(6): 1131–1140. doi:10.15560/14.6.1131. ISSN 1809-127X.
- Wesener, T. (2012). "Nearctomeris, a new genus of Pill Millipedes from North America, with a comparison of genetic distances of American Pill Millipede Genera (Glomerida, Glomeridae)" (PDF). Zootaxa. 3258: 58–68. doi:10.11646/zootaxa.3258.1.5.
- Brewer, Michael S.; Sierwald, Petra; Bond, Jason E. (2012). "Millipede Taxonomy after 250 Years: Classification and Taxonomic Practices in a Mega-Diverse yet Understudied Arthropod Group". PLoS ONE. 7 (5): e37240. doi:10.1371/journal.pone.0037240. PMC 3352885. PMID 22615951.
- Golovatch, Sergei; Mauriès, Jean-Paul; Akkari, Nesrine; Stoev, Pavel; Geoffroy, Jean-Jacques (2009). "The millipede genus Glomeris Latreille, 1802 (Diplopoda, Glomerida, Glomeridae) in North Africa". ZooKeys (12): 47–86. doi:10.3897/zookeys.12.179.
- Sierwald, P.; Shear, W. A.; Shelley, R. M.; Bond, J. E. (2003). "Millipede phylogeny revisited in the light of the enigmatic order Siphoniulida". Journal of Zoological Systematics and Evolutionary Research. 41 (2): 87–99. doi:10.1046/j.1439-0469.2003.00202.x.
- Sierwald, Petra; Bond, Jason E. (2007). "Current Status of the Myriapod Class Diplopoda (Millipedes): Taxonomic Diversity and Phylogeny". Annual Review of Entomology. 52 (1): 401–420. doi:10.1146/annurev.ento.52.111805.090210. PMID 17163800.
- Regier, Jerome C.; Wilson, Heather M.; Shultz, Jeffrey W. (2005). "Phylogenetic analysis of Myriapoda using three nuclear protein-coding genes". Molecular Phylogenetics and Evolution. 34 (1): 147–158. doi:10.1016/j.ympev.2004.09.005. PMID 15579388.