A new fossil katydid of the genus Arethaea Stål (Orthoptera: Tettigoniidae) with exceptionally preserved internal organs from the Eocene Green River Formation of Colorado

Orthoptera (grasshoppers, crickets, and katydids) are abundant and diverse in the lower–middle Eocene Green River Formation of the Piceance Basin in northwestern Colorado, though remain almost entirely unstudied. Here, we describe a new species of the katydid genus Arethaea Stål (Tettigoniidae: Phaneropterinae: Insarini) from the Parachute Creek Member at a locality near Meeker in Rio Blanco County. Arethaea solterae Heads, Thomas & Hedlund sp. nov. is the first fossil member of the genus and the first tettigoniid described from the Green River Formation. The holotype and only known specimen is remarkable for the exceptional preservation of internal organs including the anterior midgut (ventriculus) and what appear to be a testis, accessory glands, and possible fat body.