A detailed account can be found in the Catfish of the Month article (link below).
\nThe species is sometimes confused with L448 (LDA068), which is very similar, but grows larger. The main key for distinguishing them is that juvenile L448 have stripes/squiggles/scribes on the head, which only appear in mature Panaque maccus. The mature size of L448 can be over 100mm, something not seen in P. maccus.
Like all members of the genus, males grow elongated interopercular odontodes during the breeding season. Males develop noticeable odontodes along the dorsum (back of the body) as well. Males develop small pointed genital papillae, whereas mature females will have large, rounded, swollen papillae. Additionally, gravid females have noticeably wider bodies between the pectoral and pelvic fins when viewed from above, compared to males.