The best observation that would help in finding the taxonomic classification of the unfamiliar animal is:
The animal has sharp, pointed teeth.
This observation provides information about the animal's morphology, which is crucial for taxonomic classification. Morphological traits such as teeth shape and size can indicate dietary habits and evolutionary relationships, helping to place the animal within a specific taxonomic group. The other observations—temperament, location near deer, and the act of biting—are less relevant to formal classification.