PERMIAN MAYFLY NYMPHS 
By Jarimila Kukalova* * 
Charles University, Prague 
Although adult mayflies are not infrequently found in the fossil 
state, nymphs have been very rarely collected. The few fossil nymphs 
which are known have been placed in six families, four of them 
extant (Siphlonuridae, Leptophlebiidae, Ephemerellidae and Baeti- 
dae), and two extinct (Hexagenitidae and Misthodotidae) . Three 
of the existing families are known in the geological record only from 
these nymphs. The Leptophlebiidae are known from the Pliocene of 
Australia (genus Atalophlebia doubtfully determined) and from the 
Jurassic of the Soviet Union ( Mesobaetis ) and the Oligocene of 
Colorado (also Mesobaetis) . The Baetidae are known from the 
Pliocene of Australia ( Cloeon ) and the Ephemerellidae from the 
Jurassic of China {Turfinella) and the Jurassic of the Soviet Union 
{Mesoneta) . Since, as noted above, these three families are known 
as fossils only by the nymphs, the family determinations are probably 
not very reliable. One existing family, Siphlonuridae, is known 
from the Jurassic of the Soviet Union and is represented by 
wing fragments and nymphs ( Stackelbergisca , Tshernova, 1967). 
The extinct family Hexagenitidae, known only from the Jurassic of 
Siberia, is represented by adults as well as nymphs (Ephemeropsis) . 
The adults are well-known and have been fully described (Tsher- 
nova, 1961) but the nymphs are less satisfactorily known. The 
Misthodotidae, known from Lower Permian deposits in North Amer- 
ica and the Soviet Union, is represented by adults and a single, frag- 
mentary nymph (Tshernova, 1965). Finally, mention should be 
made of two extinct genera, Dyadentomum and Phthartus , both 
based on nymphs from the Permian of the Soviet Union, but so 
little-known that they have not been placed in any family (familiae 
incertae) P 
The present paper deals with the first well-known Permian rep- 
*Currently Alexander Agassiz Lecturer in Zoology, Museum of Com- 
parative Zoology, Harvard University. This research has been aided by 
Grant No. GB 7308 from the National Science Foundation (F. M. Carpenter, 
Principal Investigator). 
I am deeply indebted to Professor Carpenter, who suggested this study 
and was extremely helpful in its preparation. 
*A species of Phthartus has been described from the Triassic of South 
Africa but its assignment to that genus is most questionable (Haughton, 
1924). 
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