106 



elongated with a shallow constriction on its anterior portion; its posterior portion is broa- 

 der than its anterior portion. The anterior margin of the bone is concave in P. cumber- 

 landensis and tennesseensis (TS 117[1]); the margin is not concave in other species of 

 Phoxinus (TS 117[0]) and in the outgroups. Moreover, a notch is present at the anterior 

 margin of the anterior ceratohyal in P. phoxinus and issykkulensis (TS 1 1 8[ 1 ]). This notch 

 is absent in other species of Phoxinus and in the outgroups (TS 1 1 8[0] ). 

 Hypohyal (Figs.65A-D, 66A-B). In cyprinids, two hypohyals, i.e., dorsal and ventral 

 ones (dorsohyal and ventrohyal in Howes 1978), are present at each side. The dorsal and 

 ventral hypohyals are joined each other by ligaments (Howes 1978). The posterior side 

 of the dorsal hypohyal contacts the dorsoanterior side of anterior ceratohyal, and the ven- 

 troposterior side of the ventral hypohyal articulates with the ventroanterior side of the an- 

 terior hypohyal. Both hypohyals articulate with the posterior side of the basihyal anteriorly. 

 In Phoxinus, the two hypohyals are not identical in shape. Generally, the bones are rect- 

 angular with a notch at the ventral side of the dorsal hypohyal, and a notch at the dorsal 

 side of the ventral hypohyal. The hyoid foramen is usually formed between the two 

 hypohyals (Fig.66A). This condition is present in all species of Phoxinus, except P. eos, 

 and in the outgroups (TS 119[0]). In P. eos, the foramen is formed by the single ventral 

 hypohyal (TS 119[1]) (Fig.66B). In P. neogaeus, a concavity is present at the dorsal side 

 of the ventral hypohyal and the ventral side of the dorsal hypohyal (TS 120[1]) - an apo- 

 morphic condition found in this species only. In other Phoxinus and in the outgroups, the 

 concavity is not present (TS120[0]). 



Basihyal (Fig.65A-D). In cyprinids, the basihyal is a single bone located anterior to the 

 hypohyal, and articulates with the left and right hypohyals posteriorly. It is rod- or bar- 

 shaped. In Phoxinus, the middle of the lateral side of the basihyal is concave. In P. cum- 



