No feminine formation from PS *ṯawr- ‘bull, ox’ is attested outside PArm. *ṯawr-at-. The only exception is Arb. ṯawrat-, but this rare word is certainly no basic designation of “cow” in Arabic (in TA 10 338, only one verse by al-Aḫṭal is adduced as an illustration, which may testify to the restricted use of this lexeme).