Agreed, the taxonomic and area analysis threads are really interesting to read with regards to this. Since birds are unfortunately unlikely due to the extra effort of creating rigs for turkeys/pelicans etc, I think by far the most lacking group is primates. We would literally need 2 back to back primate packs to bring them to where they belong with regards to both diversity and representation in zoos. And since I've mentioned it I can't help but actually list what I think could go in the packs (3 old world, 3 new world, 1 lemur for each):After this India pack i feel like those gaps are no longer about places lacking animals (with the exceptions of Patagonia/ Tropical South America) but more about types of animals (birds, reptiles, monkeys all around) or specific animals (coati, tree roo, musk ox).
Pack 1: Golden Lion Tamarin, Emperor Tamarin, Black Howler Monkey, Gelada, Hanuman Langur, De Brazza's Monkey, Aye-Aye
Pack 2: Common Marmoset, Bolivian Squirrel Monkey, Geoffroy's Spider Monkey, Golden Snub-nosed Monkey, Mantled Guereza, Barbary Macaque, Crowned Lemur