Exobiology does not, at present, study the different species of aliens that people (claim to) have encountered. A new word should therefore be created for the discipline that does describe these different species. Exophenotypology could thus be described as the typology or classification of extraterrestrials based upon the observable characteristics of their physical appearance. Patrick Huyghe probably was the first to make a systematic classification based upon phenotypes, i.e. the observable characteristics, of aliens.
Personally, I am using a slightly different categorization, that uses the following main categories:
- humanoid mammalian
- non-humanoid mammalian
- hybrids and clones
- others, including non-physical and group