As pancrustacea or Tetraconata a group which is Arthropod referred to in which the insect with the crustaceans are combined into one group. This is the subject of various phylogenetic hypotheses.
The systematics within the euarthropods (arthropods in the narrower sense without Onychophora and Tardigrada ) is, like their relationship to outside groups, still controversial.
Traditional outline
Traditionally, the chelicerates ( horseshoe tails and arachnids ) are compared to the mandibular animals (mandibulata) ( millipedes , crabs and insects ). Within the taxon Mandibulata, the question is open whether the insects should be grouped with the millipedes as Tracheata (Antennata). Arguments for this are similarities, such as the reduction of the 2nd antenna and the possession of specific trachea :
After various investigations, the hypothesis is often put forward in the literature that the insects within the mandibular animals are closer to the crustaceans ( Crustacea ) and are to be compared to the millipedes as a common taxon Tetraconata. The most important argument for this is the construction of the complex eyes in crabs and insects. They match in their structure down to the last detail and have two corneagen cells, four Semper cells and eight retinula cells.
Some authors assume that the insects evolved within the crustaceans . This would make " Crustacea " a paraphylum if the insects were not included. This thesis is expressed by the term Pancrustacea . Developmental biology in particular provides arguments for this .
The Myriochelata hypothesis is also supported by some authors. Hereinafter, the form Millipede with the jaw claws supports the monophylum Myriochelata, which is compared with the Tetraconaten. The main argument that arachnids are related to millipedes is the matching number of neuronal immigration centers in ganglia formation.
H. Paulus: Euarthropoda, Arthropods ieS In W. Westheide and R. Rieger (Hrsg.): Special Zoology Part 1: Protozoa and invertebrates. Spektrum Verlag, Heidelberg 2006; Pp. 463-473
J. Regier, J. Shultz, A. Zwick, A. Hussey, B. Ball, R. Wetzer, J. Martin, & C. Cunningham: Arthropod relationships revealed by phylogenomic analysis of nuclear protein-coding sequences. Nature, 2010 doi : 10.1038 / nature08742
