Einiges zur Stammesgeschichte der Spinnentiere (Arthropoda, Chelicerata)

Some remarks on the phylogeny of chelicerates (Arthropoda, Chelicerata). WEYCOLDT & PAULUS (1979) and SHULTZ (1990) proposed two of the most discussed cladograms of the Arachnida, which differ in many points. One of the main difference is the position of scorpions. The first authors see in the scorpions the sistergroup of all remaining arachnids (named Lipoctena) whereas SHULTZ thinks that pseudoscorpions alone are the sistergroup of scorpions. In some new publications about fos- sil chelicerates the scorpions are positioned as a sistergroup of Eurypterida. This means the polyphyly of the Arachnida. Another point of discussion is the question whether the basic Arachnida invaded the land only once (so WEYGOLDT & PAULUS) or if they did it several times independently (so SHULTZ and others, mainly palaeontologists). One of the arguments of the palaeontologists is the interpretation that the early fossil scorpions had been marin. This review shows that the complex structure and function of sense organs (eyes, slit-organs, trichobothria, combs) support strongly the monophyly of the Arachnida together with the hypothesis of only one single invasion of the land. The resulting phylogenetical sys- tem of the Euchelicerata is proved with synapomorphies.