The Gemara concludes that when one shechts an animal with a dangling limb, the shechita is effective on the limb on a Torah level both to prevent it from having an issur status of neveila (or eiver min ha'chai) and to prevent a tu'mah status of neveila. The Rabbonon imposed a rabbinic prohibition against eating it, but didn't impose any tu'mah status. The Rambam (Hilchos Ma'achalos Asuros 5:6) in codifying this halacha writes that the status of a dangling limb on an animal that was shechted is that it is assur but there is no malkus (if it died by itself, it has a status of eiver min ha'chai both for issur and for tu'mah). It is unclear from the language of the Rambam אסור ואין לוקין עליו whether he means to say that it is an issur d'rabonon or an issur d'oraysa just that there is no malkus. The Pri Chadash (Y.D. 62) explains that according to the Rambam it is an issur d'oraysa but since ultimately included in the לאו שבכללות of בשר בשדה טרפה (as the gemara says 73b), there is no malkus. The Maharatz Chiyus quotes that the Pri Chadash proves this from the Tosefta that says that a dangling limb is assur for Goyim. Generally speaking we don't find Rabbinic prohibitions on Goyim, therefore the fact that it is considered אבר מן החי even for a Goy implies that it is an issur d'oraysa.