Another problem has been that the taxon "C. a. unicolor" described by Spix (1823) and further defined by Hershkovitz was indistinguishable from "C. a. albinos"; the two are synonymous. Hershkovitz (1949) originally named 13 subspecies, while Hernández-Camacho and Cooper (1976) described eight subspecies for Colombia. Colin Groves assessed the species in 2001, further reducing the number. One notable subspecies outside of Colombia is the critically endangered Trinidad white-fronted capuchin. The following subspecies were recognised by assessors working for the IUCN as of 2015. The IUCN list differs from that by Groves (2005) in that Groves excluded "C. a. cesarae" and "C. a. malitiosus" but included "Cebus albifrons unicolor" as a subspecies. In the "Handbook of the Mammals of the World" (2013) Mittermeier and Rylands limit "C. albifrons" to the Humboldt's white-fronted capuchin ranging in the upper Amazon basin in southern Venezuela, southern and eastern Colombia and northwest Brazil, based largely on the work of Jean Boubli, Thomas Defler and Jorge Hernández-Camacho. In particular, the following forms that had previously been considered subspecies or populations of "C. albifrons" have been reclassified as separate species:   Mittermeier and Rylands consider the Trinidad white-fronted capuchin to be synonymous with the brown weeper capuchin ("C. brunneus"), but other authors including the IUCN regard it as a separate species, "C. trinitatis". The difficulties in identifying separate subspecies and species have been pronounced. Hernández-Camacho and Cooper reported some specimens of capuchin from the Barranquilla animal market had supposedly come from the middle valley of the San Jorge River. It is difficult to determine whether these are white-faced capuchins ("Cebus capucinus") or white-fronted capuchins. Intermediate characteristics include a dark crown that is high and removed from the forehead. The white parts on the face are more distinctively bald and the outside parts of the arms and legs are more clear; this suggests they are white-headed capuchin. Some specimens of "C. versicolor" seen in the market at Magangué‚ and probably captured in the lower Cauca River, show similar tendencies to the above, except that there is no increase in the dark pigmentation.