Tettigidea armata species group

Diagnosis: Slender or moderately robust body. Facial carinae and frontal costa not thickened, in lateral view moderately prolonged, rounded or obliquely truncated, almost as a horn-like. Spine of the anterior margin of the pronotum developed. Macro or brachypronotal forms. Median carina of the pronotal disc slightly elevated. Hind wings developed or not.

Species included: two recent species, T. acuta Morse, 1895 and T. armata Morse, 1895, and T. unicornis (Gorochov, 2012) from Eocene of North America.

Distribution: North America: Eastern United States (Fig. 38) and Western (Eocene of Wyoming).

Comments: Eotetrix Gorochov, 2012 syn. nov. is proposed here as a synonym of Tettigidea . Heads et al. (2014) suggests that Eotetrix is similar to the extant genus Scaria in the form of the anterior pronotal spine, although Gorochov & Labandeira (2012) did not publish photographs of their fossils, the drawings provided in the authors’ publication indicate more similarity with Tettigidea than with Scaria and relative genera such as Rehnidium and Batrachidea, since the head is robust and the fastigio-facial angle is more prominent, the structure of the pronotum and the curvature of the dorsal carina of the sub-elevated pronotal disc suggests more similarity with Tettigidea . For these reasons we propose the new synonymy. Furthermore, the only species described in Eotetrix is located in the armata species group of Tettigidea, making the new combination effective Tettigidea unicornis (Gorochov, 2012) comb. nov., having the typical appearance of the other two species included in the group, with a spine in the anterior margin of the pronotum, ruling out its affiliation with the lateralis species group, another group of North American Tettigidea species.

Only two groups of Tettigidea species are distributed in North America, the other groups with the majority of species are known in South America, this supports the proposal of Rehn & Grant (1958), which mentioned that Tettigidea species arrived in North America at times and different lineages. With the inclusion of T. unicornis in this genus, the possible arrival of the ancestors of the species of the armata species group to North America can be dated to about 6-1 mya, estimated time range of the fossils found in the Green River Formation (Gorochov & Labandeira, 2012). In addition, the distribution of the armata group could have been broader in the past, inhabiting what is currently Colorado and Wyoming, localities distant from the current distribution of this group of species.