Four subspecies recognized:
coeruliceps (Gould 1836); type locality Tamaulipas, Mexico
Occurs in northeastern Mexico, from Nuevo León and Tamaulipas south to northern Veracruz
Differs from other subspecies by having the center of the crown blue (Ridgway 1914, Chapman 1923); thus, this is only truly blue-crowned member of the "Blue-crowned Motmot" complex (!).
goldmani Nelson 1900; type locality Motzorongo, Veracruz, Mexico
Occurs from southeastern Mexico (north to southern Veracruz) south to northern Guatemala
Similar to lessonii, but underparts greener; also differs "in the absence of cobalt-blue in the posterior blue margin to the black pileum" (Chapman 1923).
exiguus Ridgway 1912; type locality Temax, Yucatán, Mexico
Occurs in southeastern Mexico in Campeche and Yucatán
Greener than lessonii and goldmani; differs from goldmani "in having the blue nuchal band margined posteriorly with smalt-blue" (Chapman 1923).
lessonii Lesson 1842; type locality Realejo, Nicaragua
Occurs from southwestern Mexico (Chiapas) south to western Panama (Chiriquí and the Azuero Peninsula)
See Detailed Description.
Momotus coeruliceps (monotypic) and Momotus lessonii (including goldmani and exiguus) both were classified as separate species by most early authorities (e.g. Cory 1918, Chapman 1923), until Peters (1945) included them within a broadly defined, polytypic Momotus momota; as recognized by Peters, Momotus momota (Amazonian Motmot) also included the taxa currently assigned to Momotus coeruliceps, Momotus subrufescens (Whooping Motmot), Momotus bahamensis (Trinidad Motmot), and Momotus aequatorialis (Andean Motmot). The Peters concept of a broadly defined species, with a geographic range extending from Mexico south to southern Brazil, was widely followed for many years.
A very recent and thorough study was conducted by Stiles (2009). The criteria for redefining the species of Momotus were generated by detailed analyses of external measurements, plumage patterns and primary 'hooting' call. Stiles focused on 10 taxa in regions within Nicaragua, northern Peru, Trinidad, Tobago and Guyana. The species limits were drawn on the basis of two general criteria: "diagnosability, and the probability that differences observed would assure maintenance of reproductive isolation should currently allopatric groups enter into contact" (Stiles 2009). Based upon the results of his analyses, Stiles concluded that the genus Momotus can be broken into five species-level taxa: M. coeruleiceps, M. aequatorialis, M. bahamensis, M. subrufescens and M. momota. Collectively, these five species constitute the "Blue-crowned Motmot" complex. Stiles (2009) did not investigate, however, the relationships between coeruliceps and the lessonii group.