Head capsule, chephalic central nervous system and head circulatory system of an aberrant orthopteran, Prosarthria teretrirostris (Caelifera, Hexapoda)

The head capsule, the circulatory system and the central nervous system of the head of Prosarthria teretrirostris (Proscopiidae) is described in detail, with special consideration of modifications resulting from the aberrant head shape. The transformations of the head are completely different from those found in phasmatodeans, which are also characterised by twig mimesis. The circulatory system is distinctly modified. A hitherto undescribed additional structure in the posterior head region very likely functions as a pulsatile organ. The cephalic central nervous system is strongly elongated, with changes in the position of the suboesophageal ganglion, the corpora cardiaca and the course of the nervus mandibularis. Three-dimensional reconstructions of these two organ systems in combination with the pharynx were made using Alias® Maya 6.0™ software. Comparisons with other representatives of Caelifera suggest a clade comprising Proscopiidae and Morabinae. The presence of a transverse muscle connecting the antennal ampullae in Prosarthria shows that this structure likely belongs to the groundplan of Orthoptera, even though it is missing in different representatives of this group. The transverse ampullary muscle is a potential synapomorphy of Orthoptera, Phasmatodea and Dictyoptera.