tortes's Identifications

So this is definitely an unusual guy. The general appearance of the gills + appearance of the body would have made me guess a member within Leptohyphidae. However, the gills only seem to be present dorsally on abdominal segments 6 to 7, which is rather unusual. That would make me think maybe Ephemerellidae, but I'm not finding anything that keys to that gill placement. I suppose the other gills could have fallen off, that's not outside the realm of possibility. Something about how dark the gills on abdominal segment 6 are almost makes me think that's not the case though? Also, not sure if those are ventral gills present on the preceding abdominal segments in Figure 6. This mayfly was rather small. I might want to get better ventral pictures...