Eugh, I want this to be in the contest, but I don't see where words can be cut out, either.
Instead of describing it as capable of shapeshifting, you can describe it as occasionally involuntarily doing so?
Like, this is what you have:
SCP-XXXX is an entity capable of altering its appearance and bodily composition. Currently, SCP-XXXX maintains the forum of a juvenile Chiloscyllium punctatum (Brown-banded bamboo shark), with wing structures similar to that of Sasakia charonda (Japanese emperor or great purple emperor) sprouting from near its dorsal fin.
Though SCP-XXXX appears capable of assuming various unnatural forms, this ability appears to be involuntary. Furthermore, major morphological changes are invariably accompanied by deformities, including signs of malnutrition and injury. These disfigurements are noted to abate with time, albeit at a highly regressed rate of healing regardless of the care provided.
This is one alternative:
SCP-XXXX is an entity that spontaneously experiences involuntary morphological changes. Currently, SCP-XXXX maintains the forum of a juvenile Chiloscyllium punctatum (Brown-banded bamboo shark), with wing structures similar to that of Sasakia charonda (Japanese emperor or great purple emperor) sprouting from near its dorsal fin. Its morphology invariably features deformities, including signs of malnutrition and injury. These disfigurements are noted to abate with time, albeit at a highly regressed rate of healing regardless of the care provided.
I'm not even sure if that's a smaller word count and how the footnotes would play into my version, but hopefully this helps!
Disregarding contest facets of this, its neat.