Black (1927 p. 21) established Sinanthropus pekinensis based on an isolated molar tooth from Level 1. The paper attributed authorship of the taxon jointly to Black & Zdansky.
Campbell (1965) listed Sinanthropus pekinensis Black & Zdansky, 1927 (in Black, 1927) as an available and potentially-valid taxon. Campbell (1965) described the type specimen as a lower left molar.
Groves (1989) listed Sinanthropus as a junior synonym of Homo, and Homo erectus pekinensis Black, 1927 as an available, valid taxon. Goves described the type just as "Molar tooth". (p. 282). Groves attributed authorship to Black alone, but as noted above, it should be attrbuted jointly to Black and Zdansky.
Zanolli et al. (2018) described the ?type specimen PMU M3550. They refer to this specimen as the type of Sinanthropus pekinensis, however M3550 is an upper molar and the tooth imaged in Plate II of Black (1927) is a lower. Further work is needed to confirm the catalog number of type specimen.
