A new Frenguelliidae (Insecta: Odonata) from the Eocene of Arroyo Chacay, Patagonia, Argentina

Abstract

The family Frenguelliidae Petrulevičius & Nel, 2003 was hitherto known from two genera and three species: Frenguellia patagonica Petrulevičius & Nel, 2003, F. iglesiasi Petrulevičius & Nel, 2013 and Treintamilun vuelvenlucha Petrulevičius, 2017. Frenguelliidae is a very interesting group, controversially considered either an Epiproctophora, basal to Euepiproctophora by Petrulevičius & Nel (2003, 2007, 2013) and Petrulevičius et al. (2011), or a Zygoptera by Nel & Arillo (2006), Nel et al. (2008), Lak et al. (2009) and Bechly & Poinar (2013). Only the epiproctophoran hypothesis was discussed and based principally in a putative character of the group, the curved CuP (Petrulevičius & Nel, 2003, 2007, 2013). The zygopteran hypothesis could be reasonably adopted due to the presence in Frenguelliidae of a character which is absent in the basal Epiproctophora: the IR2 aligned with the subnodus (Petrulevičius, 2017). Other characters shared by Frenguelliidae and other Zygoptera are homoplastic and are also present in some Epiproctophora, i.e., arculus nearer to Ax2 than to Ax1 in Cyclothemistidae: Triassoneura (Fujiyama, 1991) and Epiophlebiidae: Mesoepiophlebia (Nel & Jarzembowski, 1996); the lack of pterostigmal brace in Campterophlebiidae: Ctenogampsophlebia (Petrulevičius et al., 2011); absence of secondary antenodals could also occur in Triassoneura. The morphology of the new species does not contradict the hypothesis postulated by Petrulevičius & Nel (2003, 2007, 2013) about the phyletic position of the group which remains uncertain and its resolution exceeds the possibility of the present work but is a nice topic for future research.