Stewart Robert Hinsley wrote:
It appears that the Asplenium nidus of commerce is composed of one or
more members of a species complex, and should be referred to as
Asplenium nidus hort, rather than Asplenium nidus L. ..............

No need for that, the plant grown as 'Asplenium nidus' is A.
australasicum - a relatively common species in its native Australia. By
contrast, the true A. nidus is quite rare in nature and very much more
so in horticulture.

As for the identity of the leaf it could be from A. australasicum, but
the picture is too poor for anyone to give a definite identification.

--
Dave Poole
Torquay, Coastal South Devon UK
Winter min -2C. Summer max 35C.
Growing season: March - November