"
ae" is how Latins most generally wrote "
ai"... (Unless the 'i' had a consonant function, that is--but we would now usually write the letter 'j' rather than 'i' in most such cases.)
Masculine personal names with a genitive in -
ae are in no way unusual. Standard Latin names (classical nominative in
-a):
Numa,
Catilina,
Murena (genitive
Numae,
Catilinae,
Murenae); also names inherited from Greek with nom. in
-as:
Aeneas,
Lucas,
Judas,
Thomas (gen.
Aeneae,
Lucae,
Judae,
Thomae); as well as a few other such names in
-es:
Anchises (Aeneas' father),
Perses (gen.
Anchisae,
Persae).
Otoh, second-declension nouns or names in
-aus are basically non-existent in Latin. (The only genuinely Latin nouns with a nominative that ends in
-aus are
fraus, gen.
fraudis, and
laus, gen.
laudis: both third-declension words, and both feminine...) However some Greek masculine nouns/names in -αος were used by Latins in a way that produced genitives in
-ai (eg. Greek Μενελαος, in Latin
Menelaus, gen.
Menelai). A name or noun with an
-ai ending in a Latin text looks immediately pretty exotic, though.
The Code explicitly allows both endings:
-ae (under Art. 31.1.1) and
-ai (under Art. 31.1.2) (see the treatment of Poda
in the examples that come with these articles), and protects the original spelling.
Groves used
azarai for
Aotus azarae in 1993, citing "Art. 31" of the ICZN (but overlooking 31.1.1 and 31.1.3).
In 2005, he himself reverted to the original spelling.
(Note that "a ruling of the ICZN" would be a decision made on a specific case by the International
Commission of Zoological Nomenclature. There was no ruling here, I believe; it was just a personal interpretation of an article of the International
Code of Zoological Nomenclature.)