Phylogenetic and biogeographical remarks on Thyridates (Mecoptera: Bittacidae), with the first fossil record of the taxon

PETRULEVICIUS J. F.

Cracovia

Congreso; II International Congress on Palaeoentomology (Fossil insects); 2001

Until know, no representatives of Thyridates have been recorded as fossil. A specimen representing a new species was recovered from the late Paleocene of Northwest Argentina. The genus Thyridates Navás, 1908 was monospecific until Willmann (1983) made a rediagnosis of the genus and transferred 11 South American species from Bittacus. After that, Collucci and Amorim (2000) added two North American species of Bittacus into this genus. Thyridates sensu Willmann (1983) has two autapomorphies supporting its monophyly, i.e. (1) RP1+2 forks from RP nearly at right angle; (2) presence of crossveins between Sc and wing margin. However, the last synapomorphy is less accurate because some individuals have not these crossveins. Also such a crossvein is present in some other Jurassic and Cretaceous genera. Collucci and Amorim (2000) added 5 supposed autapomorphies for Thyridates, i.e. (3) fork of RP more basal than apex of Sc; (4) crossvein sc-r1 apical; (5) thyridium well defined; (6) elongated pterostigma; (7) relatively large wings. Among these, character (3) could also correspond to a symplesiomorphy because it is also present in some Mesozoic genera, or a synapomorphy with Palaeobittacus Carpenter, Harpobittacus Gerstaecker and Thyridates. Other characters are not suitable for the definition of the genus. Characters (4) and (5) are also present in most genera. Character (6) is not well defined. But an elongated and (primarily) sagged pterostigma linked (primarily) with RP by two crossveins could be an autapomorphy of Thyridates. Character (7) is not an autapomorphy of the genus since the new species is distinctly smaller than other Thyridates (wing length estimated in 11 mm). Concerning character (1), the new species and two others have their RP1+2 forked with an angle of about 45°. Then, this character is not shared by all the species and could have been acquired later in the evolution of the genus. I define a new character present in some species of this genus and strictly absent in all other Bittacidae, i.e. (8) bifurcation of MP1 - MP2 arising at the same level that both bifurcations: RP3+4 - MA, and MP3 - MP4+CuA. The bifurcation of MP1 - MP2 became more basal reaching the crossveins ma-mp1+2-mp3+4. On this way, one of the sides of the "Kreuz der Bittaciden" appears forked. With the most parsimonious approach, characters (1) and (8) are considered as synapomorphies of the group. The homoplasies found in this analysis could be explained by a reversion occurring in one or both characters. Until now, Thyridates was considered to be an American genus. Nevertheless, Collucci and Amorim (2000) taking into account some remarks of Willmann (1983), considered the possibility of finding some Bittacus in Asia and Africa "with closer phylogenetic relationships with the group tropical of Thyridates". I propose to transfer two African species into this genus. One of these species has the forked "Kreuz" and RP1+2 forked from RP forming nearly a right angle, concluding that both characters were present in this genus before the separation of Africa and South America. The analysis supports a Gondwanian origin for this genus.