Original paper
Zur phylogenetischen Stellung und Evolution der Chelicerata
[On the Phylogenetic Position and Evolution of the Chelicerata]
Kraus, Otto
Entomologica Germanica Band 3 Heft 1-2 (1976), p. 1 - 12
22 references
published: Oct 4, 1976
DOI: 10.1127/entom.germ/3/1976/1
ArtNo. ESP346000301000, Price: 29.00 €
Abstract
Trilobita (Trilobitomorpha, respectively) and Chelicerata form sister-groups within Arthropoda. On the basis of facts now available and from the view-point of phylogenetic systematics, it is no longer possible to divide Chelicerata simply into two groups, Merostomata and Arachnida. Arachnida are merely a stage-group of terrestrial forms. The different orders are clearly distinguished by autapomorphous characters, but it seems very difficult to find synapomorphous features common to both. Basic differences in body-segmentation, structure of chelicerae, tendency to reduce segment VII, and the occurence of book-lungs at different segments are discussed. The difficulty of reaching clear conclusions on relationships is explained by the considerable high phylogenetic age of the orders. In addition, it seems probable that important phylogenetic ramifications even occured before transition (s) to terrestrial life; it is suspected that characters indicating such ramifications might have been superimposed by terrestrial adaptations in some cases.