A new genus and species of thamnocephalid fairy shrimp (Branchiopoda: Anostraca) from Argentina (Chubut Province)

Abstract

Aeginecta longicauda n. gen., n. sp. is described from material collected from aseasonally astatic aquatic habitat in Argentina. It is only known from the typelocality and two male specimens; at this point the female remains unknown.Specific unique gonopod and genital segment features demonstrate that thistaxon represents a unique genus within the Thamnocephalidae. Aeginecta n.gen most closely resembles Phallocryptus Biraben, 1951 and ThamnocephalusPackard, 1877. This new genus is easily diagnosed by the compound eyepeduncle being extremely short, the frons and anterior surface of antennaeII broadened laterally, with an intervening slit through which the compoundeye may view the area forward on the animal, and the cercopods are as longas the abdomen. The gonopod proximal portion is bulbous with a transversecleft, and projects ventrally from the segment. The gonopod distal eversibleportion is minute, lamellar, and lies within proximal portion cleft. This is thefifth thamnocephalid genus reported from South America. The Neotropicalregion has the greatest thamnocephalid generic diversity in the world.