Each of the animals in the list is extinct. What’s more, each lived exclusively during a single period of geologic time. The letters in the top-left of each row of the image suggest that periods are important, as they are the first letters of the most recent seven periods from newest to oldest: Quaternary, Neogene, Paleogene, Cretaceous, Jurassic, Triassic, and Permian.
It turns out that exactly three of the animals belong in each period. Keeping the creatures in alphabetic order, the chart can be filled in as below:
There remains one number per period which hasn’t been used. Using the numbers to index into the names on their blank gives the answer HOMINID.