• Molecular developmental evidence supports the revised 'outside-in' hypothesis for fish tooth origin, involving ectodermal scales and endodermal mesenchyme.
• Fish dentin is classified into four types: orthodentin, osteodentin, pseudodentin, and vascular dentin, reflecting morphological diversity.
• Enameloid mineralization evolved from vesicle-mediated (cartilaginous fish) to collagen-templated (teleosts) mechanisms.
• Core signaling pathways (FGF, Shh, Wnt) are functionally conserved but exhibit species-specific regulatory adaptations.