During skeletal muscle excitation-contraction (EC) coupling, membrane depolarizations activate the sarcolemmal voltage-gated L-type Ca ²⁺ channel (Ca _V 1.1). Ca _V 1.1 in turn triggers opening of the sarcoplasmic Ca ²⁺ release channel (RyR1) via interchannel protein–protein interaction to release Ca ²⁺ for myofibril contraction. Simultaneously to this EC coupling process, a small and slowly activating Ca ²⁺ inward current through Ca _V 1.1 is found in mammalian skeletal myotubes. The role of this Ca ²⁺ influx, which is not immediately required for EC coupling, is still enigmatic. Interestingly, whole-cell patch clamp experiments on freshly dissociated skeletal muscle myotubes from zebrafish larvae revealed the lack of such Ca ²⁺ currents. We identified two distinct isoforms of the pore-forming Ca _V 1.1α _1S subunit in zebrafish that are differentially expressed in superficial slow and deep fast musculature. Both do not conduct Ca ²⁺ but merely act as voltage sensors to trigger opening of two likewise tissue-specific isoforms of RyR1. We further show that non-Ca ²⁺ conductivity of both Ca _V 1.1α _1S isoforms is a common trait of all higher teleosts. This non-Ca ²⁺ conductivity of Ca _V 1.1 positions teleosts at the most-derived position of an evolutionary trajectory. Though EC coupling in early chordate muscles is activated by the influx of extracellular Ca ²⁺ , it evolved toward Ca _V 1.1-RyR1 protein–protein interaction with a relatively small and slow influx of external Ca ²⁺ in tetrapods. Finally, the Ca _V 1.1 Ca ²⁺ influx was completely eliminated in higher teleost fishes.