Retired in ISO 639-3: Split into Tandaganon [tgn] and Surigaonon [sgd] (new identifier)
Excerpt from change request document:
The Tandaganon language is distinct from Surigaonon and from other languages in northeastern Mindanao (Butuanon, Kamayo, Mamanwa, Manobo) and other Philippine languages. It was included in the Zorc dissertation/monograph on Bisayan languages, but overlooked by all other researchers afterwards (but will be included in the forthcoming Lobel dissertation, where it is treated a distinct language). Zorc's dissertation treats Tandaganon as coordinate with Surigaonon, as does the forthcoming Lobel dissertation. Native speakers of this language refer to it as "Tandaganon" or "Tagon-on" and not as Surigaonon. It is different enough from Surigaonon that Surigaonon speakers refer to it as "Kamayo" (which is the next language to the south of Tandaganon); On the other hand, it is different enough from Kamayo that Kamayo speakers refer to it as "Tandaganon", "Tagon- on", or "Surigaonon". Tandaganon speakers often have intelligibility of Surigaonon because Surigaonon speakers from northern Surigao del Sur often come to Tandag (the provincial capitol) in order to conduct business. Surigaonon speakers (and especially those from outside of Surigao del Sur province) have much less understanding of Tandaganon, and as previously stated, often mistakenly refer to it as "Kamayo", a language which is even more different from Surigaonon.