Why don't these count for the quest..lots of horns & tusks in this group.

Presumably because the extinct critters are already part of the quests -- they are one of the rewards.

(They don't count for any of the quests.)

Also wondering why the Horns and Tusks quest is actually only horns! There are elephants with tusks and walrus to name but two non extinct animals:) None of the tusked critters are named on the list for horns and tusks

It's only the one level where it's only horns - and that's presumably to make it easier.  Other levels ask for other combinations of horns/tusks.

There are other quests where there are particular requirements which don't include certain wildlife in some levels which are accepted in others the Ugly Bug Ball at level 3 asks for one butterfly and one caterpillar, for instance, when in other levels any bug will do.  And for some of the This Is Nuts and Black and White quests, some levels are all albinos/melanistic - none of the other wildlife which counts for other levels count.

And for the levels where it's both horns AND tusks required, both are listed as part of the requirements.

Ah! I did wonder but haven't moved to those levels yet! Thanks Tracey:)