Tshernova (1972) established the genus Vietnamella for a new species of Asian Ephemerellidae, Vietnamella thani. Allen (1980), with little discussion, placed Vietnamella as a subgenus of CincticostellaAllen, 1971, in the tribe Ephemerellini. Later, Allen (1984), with somewhat more discussion of the nymphal characters, in particular the nymphal gills, admitted that the placement of Vietnamella as a subgenus of Cincticostella had been incorrect. He established a new subtribe of the Ephemerellini, Vietnamellae, for Vietnamella.
Edmunds and Murvosh (1995) transferred the genus Vietnamella to the related subfamily Teloganodinae and retained the tribe name Vietnamellini for it.
McCafferty and Wang (1997) presented evidence that Vietnamella was closely related to AustremerellaRiek, 1963, and, apparently over-looking the existence of the subfamily name Vietnamellinae, established a new subfamily, Austremerellinae, in the family Teloganodidae for the two genera. Then, McCafferty and Wang (2000) proceeded to raise the taxon to a family, which they called Austremerellidae.
According to the International Code of Zoological Nomenclature (ICZN 1999: Article 36.1) establishment of Vietnamellae (Allen 1984) had the effect of also establishing names for all other ranks in the family group (coordinate taxa: e.g., family, subfamily, tribe). This means that the name Vietnamellidae became available and valid at that time.
In determining the valid name of a zoological taxon, the “Principle of Priority” applies (ICZN 1999: Article 23). It states that “The valid name of a taxon is the oldest available name applied to it . . .” Although the Code does make exceptions for family names in prevailing usage (IC2N 1999: Article 35.5), Article 23.9.1 describes prevailing usage to require, among other things, that the senior synonym has not been used as a valid name after 1899. This is clearly not the case here. Vietnamellae (and its coordinate taxa) was established in 1984 and was an available and valid name at the time Austremerellidae was established.
Therefore the valid name for this family of Ephemerelloidea is Vietnamellidae Allen, and Austremerellidae McCafferty and Wang is a junior synonym.