“-ii is from when they Latinized the author’s name as well. So if it’s called thomasii it’s because Thomas was latinized to Thomasius, then with the possessive replacing the suffix it becomes thomasii. -i is when the root is the unlatinized name” - @kmagnacca
https://forum.inaturalist.org/t/where-do-i-start-with-pronouncing-scientific-names/33080/33?page=2
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