Unique Species - Count 1 missing

[weak remnant]

I have all 53 species from the nursery screen within my park - additional Microraptor and Archaeopteryx.
So in sum 55 unique species - but only 54 are counted. Why?
I double-checked it twice an counted again and made a list to check - there are 55 here.
Which one doesn't count?

[uncut raft]

one of them isn't registering, this was happening to me too
(holy cow, 300 animals)