To determine the taxonomic classification of an unfamiliar animal, the most informative observation would be:
The animal has sharp, pointed teeth.
This observation can indicate specific dietary habits and adaptations, which are important factors in classification. For example, sharp, pointed teeth can suggest the animal is a carnivore, which could provide significant clues regarding its phylogenetic relationships with other species. The other observations, while they may provide context or behavioral insights, do not directly inform the systematic classification as effectively as dental morphology does.