Cephalomorpha

Cephalomorpha is a proposed infraorder of myriapods that includes the class Pauropoda and the class Symphyla. This grouping is based on shared morphological and molecular characteristics. Pauropods are small, millipede-like creatures found in soil and leaf litter, characterized by their short antennae and reduced eyes. Symphylans are also small, centipede-like arthropods, often found in similar damp environments, distinguished by their long antennae and presence of spinnerets.

The primary justification for grouping these two classes into Cephalomorpha comes from genetic studies, which indicate a closer evolutionary relationship between pauropods and symphylans than with other myriapod groups. Morphologically, both groups share a tendency towards reduced body segmentation and the presence of a "head shield" or collum segment that covers the base of the head. However, these similarities are subtle and have led to debate among scientists regarding the validity of this infraorder.

Alternative classifications exist, with some researchers preferring to keep Pauropoda and Symphyla as distinct classes within the subphylum Myriapoda without a formal infraordinal grouping. The debate highlights the ongoing process of understanding arthropod phylogeny and the challenges of classifying groups with unique evolutionary histories. Further research, particularly in genomics and developmental biology, will continue to refine our understanding of the relationships within the Myriapoda and the position of Cephalomorpha.