A morphological study of Timema cristinae vickery with implications for the phylogenetics of phasmida

Abstract

The results of an investigation of the exosketetal and visceral morphology of Timema cristinae are presented, with a literature summary, and discussion of phylogenetically important characters. Further evidence is presented against the claim that Timema exhibit neoteny; the proposed similarities of Timema with nymphal Grylloblattodea are shown to be based on an error. The left genital process and vomer are tentatively proposed to be homologous. Possible autapomorphies of Phasmida include a swollen lateral region of the frons, prothoracic defense glands, pyriform filament bearing processes on the mesenteron, numerous short and parallel lateral dorso-ventral muscles of the abdomen and the movable sclerotized process in the region of male sternum X (left genital process and vomer). The monophyly of Timema may be supported by the presence of three fused basal tarsomeres, the mesal lobe of the right cercus of the male, and the egg-coating behavior of the female. The assumed condition of an undivided sternum IX of the male is contradicted by observations of T. cristinae. Timema cristinae possesses a suite of character states apparently plesiomorphic for Phasmida. The hypothesis that Timema is the sister-group of all other extant Phasmida receives tentative support.