Confirmed "Gigantopithecus" remains have since been found in 16 different sites across southern China. The northernmost sites are Longgupo and Longgudong, just south of the Yangtze River, and southernmost on Hainan Island in the South China Sea. An isolated canine from Thẩm Khuyên Cave, Vietnam, and a fourth premolar from Pha Bong, Thailand, could possibly be assigned to "Gigantopithecus", though these could also represent the extinct orangutan "Pongo weidenreichi". Two mandibular fragments each preserving the last two molars from Semono in Central Java, Indonesia, described in 2016 could represent "Gigantopithecus". The oldest remains date to 2 million years ago from Baikong Cave, and the youngest 380,000–310,000 years ago from Hei Cave. In 2014, a fourth confirmed mandible was discovered in Yanliang, Central China. Indicated by extensive rodent gnawing marks, teeth primarily accumulated in caves likely due to porcupine activity. Porcupines gnaw on bones to obtain nutrients necessary for quill growth, and can haul large bones into their underground dens and consume them entirely, except the hard, enamel-capped crowns of teeth. This may explain why teeth are typically found in great quantity, and why remains other than teeth are so rare.