(en) A study of the various combinations of the orders of the Gospels (see RTL, 30, 1999, pp.297-314) and the Biblical orders of the Four Living Creatures demonstrates that the identification of the Evangelists with the Living Creatures attempted in the first place to express the unity of the one and fourfold Gospel before characterizing their differences. Two systems prevailed in Christian antiquity. In the oldest, Mark is identified with the eagle (Irenaeus, Victorinus, etc.); in another system, Mark is identified with the Man (Hippolytus, etc.); in the received system, finally, Mark is identified with the Lion (Epiphanius, Jerome). Originally, Revelation (4, 5) was the fundamental Biblical locus, but in the East and then in the West, Ezekiel (1, 10) supplanted it. The conjunction of the received order of the Gospels and the sequence of the Living Creatures in Ezekiel 1, 10 resulted in the system which became usual after St. Jerome: Mt = Man; Mk = Lion; Lk = Bull; Jn = Eagle.
Bogaerts, P. (2001). Les Quatre Vivants, l’Évangile et les évangiles. Revue théologique de Louvain, 32(4), 457-478. https://doi.org/10.2143/RTL.32.4.2017495 (Original work published 2001)