The posterior margin of the lower lip has often been described as forming a posteriorly opening pouch or pocket between the lip and the skin of the throat. B. ambusticauda can be differentiated from B. melanopterus by a shorter snout. Also, in B. ambusticauda the rictus (junction of the premaxilla and maxilla at the corner of the mouth) has posteriorly direct grooves that are curved instead of straight.
The lower lip's posterior edge is frequently depicted as a pouch or pocket opening posteriorly between the lip and throat skin. B. ambusticauda can be distinguished from B. melanopterus by its shorter snout. Additionally, in B. ambusticauda, the rictus (junction of the premaxilla and maxilla at the mouth corner) has posteriorly directed grooves that curve rather than being straight.