Capital with figures, fabulous creatures and sacrifice of a bull (Mithras?)

This twin capital is designed with Corinthian-like features and, instead of Abacus leaves, it displays reclining figures, an eagle, and a female bust. The southeast corner is occupied by a nude male figure who rides a scaled, fish-tailed mythical creature. On the northwest corner of the capital a similarly shaped mermaid with a nude torso embraces her muscular rider. The west side shows the vestiges of two figures locked in battle.
Obviously, the figure and scene composition on the east side of the capital constitutes a motif-based analogy to classical representations of the sun god Mithras, whose origins can be traced back to ancient Persia. This god defeated a bull, from whose seed and body all life originated and thus Mithras became the creator of the world. Until the 4th century A.D. the Mithras cult was widespread throughout the empire. It is not clear if the sculptor at Monreale chose a Roman prototype based on artistic considerations in order to depict the sacrifice of a bull – a sacrum sacrificium – or whether he actually intended the transmission of the cult.  On this question, Erwin Panofsky pointed to the fact that both the Middle Ages and the Renaissance had no idea of the true meaning of this representation. To this extent the capital may affirm the principle of the interpretatio christiana: “Occurring in the context of a programme … it belongs to a series of representa- tions which lend visual expression to the words of St. Paul (Hebrews 10:4): Impossibile enim est sanguine taurorum et hircorum auferri peccata’, ‘It is not possible that the blood of bulls and goats should take away sins’.”
Panofsky, Erwin: Renaissance and Renascences in Western Art, Stockholm 1960, p. 99-100

scaled eagle bust fish-tailed mythical-creature mermaid torso battle Mithras rider sun god Persia bull seed life body creator world cult sacrifice sacrum sacrificium empire sculptor Panofsky prototype Roman