Huxley, in 1868, divided the carinate birds into Dromaeo-, Schizo-, Desmo-, and Aegithognathae, an arrangement which for many years had a considerable influence upon classification.
Huxley regarded the above scheme as nearly representing the affinities of the various Carinate groups - the great difficulty being to determine the relations to the rest of the Coccygomorphae, Psittacomorphae and Aegithognathae, which he indicated " only in the most doubtful and hypothetic fashion."
Their body is generally compressed and slender; their broad ventral scutes are often carinate on the sides.