Must be morphologically unchanged since its fossil age

That’s interesting. So, genetically it could be significantly changed, but shape-wise, it must appear the same? In any case, I’m thinking certain molluscs might work. Sharks also might fit the bill, altho AFAIK they don’t fossilize well. Or, are there other gymnosperms beside ferns and Araucaria that could fit the bill? I suspect so…

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Now, feel free to hate on this, but I’ve found GPT pretty useful for issues like this. Evidently, there’s quite a few more candidates.