Title isn't very good at describing my question, but in a pool of images, because of "https://e621.net/wiki_pages/show_or_new?title=tag_what_you_see " "external information can be used to help identify what character or species is supposed to be depicted in the post in cases where it isn't obvious", can I tag a species based on one of the images in the pool making it clear that it's a specific species?

lost_again said:
Title isn't very good at describing my question, but in a pool of images, because of "https://e621.net/wiki_pages/show_or_new?title=tag_what_you_see " "external information can be used to help identify what character or species is supposed to be depicted in the post in cases where it isn't obvious", can I tag a species based on one of the images in the pool making it clear that it's a specific species?

Only general tags are strictly bound by Tag What You See (TWYS), in that you only tag what you can see.
Character and species tags are semi-bound by TWYS, in that you may use your own discretion in tagging the characters/species shown but not to overstep that discretion when visual facts conflict with what is being tagged.

If the first image of the pool shows a dog, then it is safe to assume that subsequent images would also show a dog, even though they may be partially or mostly obscured (e.g., the second post only shows the paw of the character with the same fur colour/features). Thus, it would be safe to tag dog in the next post.
However, if the second post shows nothing at all (e.g., offscreen_character) or shows something completely different (e.g., showing a hoof of a character that does not remotely resemble the first character), then you may not tag the post as showing a dog and standard TWYS rules apply.

lost_again said:
Title isn't very good at describing my question, but in a pool of images, because of "https://e621.net/wiki_pages/show_or_new?title=tag_what_you_see " "external information can be used to help identify what character or species is supposed to be depicted in the post in cases where it isn't obvious", can I tag a species based on one of the images in the pool making it clear that it's a specific species?

Short answer: Yes

Longer answer straight from the source:

Tags in the Character and Species categories are partially dependent upon TWYS: that is, external information can be used to help identify what character or species is supposed to be depicted in the post in cases where it isn't obvious, but it cannot actively conflict with what is seen in the post. For example, you can tag character a if the artist claims that a disembodied hand in the post belongs to character a, unless the hand looks nothing like character a and instead looks exactly like it belongs to character b. In that case, TWYS overrides the artist's word.