Comment by bryanrasmussen
9 hours ago
In British English it is totally reasonable and in fact relatively elegant, in American it might take a couple of seconds to figure out what was being said and it would seem ungainly for this reason.
On the British elegance: in British English one could of course use "thought to be extinct" and in these kinds of structures it has become common as a stylistic touch to drop the helping infinitive, "to be", considering it implied.
Right. But, one says "X is thought extinct." or "X is thought to have been extinct for 6000 years" (or "gone extinct ... ago").
As written don't you think it begs the question (joke, fellow language pedant :) of who was doing the thinking that it was extinct over the course of those 6,000 years?