page_title: Myriapoda
section_title: Myriapod relationships
hierarchical_section_title: Myriapoda / Classification / Myriapod relationships
caption_attribution_description: English: Major hypotheses for the relationships among myriapod classes. (a, b) Traditional views based on morphology (c) Hypotheses based on molecular analyses
context_page_description: Myriapoda is a subphylum of arthropods containing millipedes, centipedes, and others. The group contains over 16,000 species, most of which are terrestrial. Although their name suggests they have myriad legs, myriapods range from having up to 750 legs to having fewer than ten legs.
  The fossil record of myriapods reaches back into the late Silurian, although molecular evidence suggests a diversification in the Cambrian Period, and Cambrian fossils exist which resemble myriapods. The oldest unequivocal myriapod fossil is of the millipede Pneumodesmus newmani, from the late Silurian. P. newmani is also important as the earliest known terrestrial animal. The phylogenetic classification of myriapods is still debated.
  The scientific study of myriapods is myriapodology, and those who study myriapods are myriapodologists.
context_section_description: A variety of groupings (clades) of the myriapod classes have been proposed, and married, some of which are mutually exclusive, and all of which represent hypotheses of evolutionary relationships. Traditional relationships supported by morphological similarities (anatomical or developmental similarities) are challenged by newer relationships supported by molecular evidence (including DNA sequence and amino acid similarities).
  Dignatha (also called Collifera) is a clade consisting of millipedes and pauropods, and is supported by morphological similarities including the presence of a gnathochilarium (a modified jaw and plate apparatus) and a collum, a legless segment behind the head.
  Trignatha (also called Atelopoda) is a grouping of centipedes and symphylans, united by similarities of mouthparts.
  Edafopoda is a grouping of symphylans and pauropodans that is supported by shared genetic sequences, yet conflicts with Dignatha and Trignatha.
  Progoneata is a group encompassing millipedes, pauropods and symphylans while excluding centipedes. Shared features include reproductive openings (gonopores) behind the second body segment, and sensory hairs (trichobothria) with a bulb-like swelling. It is compatible with either Dignatha or Edafopoda.
caption: Some of the various hypotheses of myriapod phylogeny. Morphological studies (trees a and b) support a sister grouping of Diplopoda and Pauropoda, while studies of DNA or amino acid similarities suggest a variety of different relationships, including the relationship of Pauropoda and Symphyla in tree c.
exif: {}