Studies on Carboniferous Insects From Commentry, France: Part IV. The Genus Triplosoba

Among the unusual insects described by Brongniart from the Com- mentry shales in France was a nearly complete, well-preserved speci- men, apparently related to the mayflies. Now known as Triplosoba pulchella (Brongniart), the species has usually been considered as representing either a distinct order (Protephemerida) or the Ordei- Ephemeroptera itself. In either case, the insect has held a unique position as the oldest representative of the mayfly line of evolution. This fossil was well described by Brongniart and it has been dis- cussed. by Handlirsch ( I g06), Lameere ( I 9 I 7), Martynov ( I 923), Tillyard ( 1932), and Demoulin ( 1956). Aside from Brongniart, however, only Lameere based his account on an actual study of the fossil itself, the others mentioned depending on published descriptions, figures, or photographs2 Although there has been agreement on the general relationships of Triplosoba, much controversy has existed ovei the interpretation of its venation and consequently of its phylogenetic position within the palaeodictyopterous-ephemeropterous complex. Sev- eral of these authors, including Brongniart, have attempted to con- struct restorations of the complete insect, these also reflecting widely divergent views (see plate I 3) . The present paper has been written with the hope of eliminating some of the uncertainties and confusion about the structure of Trip- losoba. It is based upon my examination of the type specimen of pulchella in the Museum National d'Histoire Naturelle in Paris. Study of this fossil was made on three separate occasions. The first examination was in 1938, although at that time only one counterpart, the poorer of the two, could be found in the Museum collection. Fol- lowing the publication of Demoulin's account of Triplosoba in 1956 -