72 



In the outgroups, the nasal bone is narrow and elongated, and located over the meseth- 

 moid and lateral ethmoid; the nasal portion of the supraorbital canal is not interrupted. 

 Preethmoid (Fig.38A, B). In cyprinids, the paired preethmoid is located between the 

 anteroventral side of the mesethmoid and anterolateral side of the vomer. Ramaswami 

 (1955a) stated that Phoxinus lacks the preethmoid. This is not the case in the specimens 

 of Phoxinus I studied. All species of Phoxinus have the preethmoid. 

 In Phoxinus, the preethmoid is semi-spherical in shape. Its position in the skull is similar 

 to that in other cyprinids. The variations of the preethmoid among Phoxinus species is in 

 its relative size. The preethmoid is well-developed and large in P. phoxinus (TS 47[1]). It 

 is smaller, not well-developed in other species of Phoxinus and in the outgroups (TS 



Mesethmoid (Figs.38A-B, 39A-B). In cyprinids, the mesethmoid is an endochondral 

 single bone resting on a cartilage (planum ethmoidale) on the vomer, and located at the 

 ventral side of the supraethmoid (Mayden 1989). In Phoxinus, the planum ethmoidale is 

 observed in a 33 mm standard length specimen of P. eos (Fig.38A). The cartilage is re- 

 duced or absent in larger specimens. Dorsally and anteriorly, the mesethmoid shares su- 

 tures with the posterior side of the supraethmoid (Fig.38A-B). The mesethmoid sutures 

 with the lateral ethmoid posteriorly. 



The mesethmoid is irregular in shape. Anterolaterally, the bone bears two foramina for 

 nerves (Fig.38A-B). Anteriorly, the mesethmoid is concave; the anterior surface of the 

 mesethmoid sutures with the posterior surface of the supraethmoid. Ventrally, the mes- 

 ethmoid bears one or two conea (Gasowska 1979), the anterior and posterior ones, which 

 are concave and position at the ventral side of the mesethmoid (Fig.39A-B). 

 Variation in the mesethmoid of Phoxinus occurs mainly at its ventral aspect. In P. phoxi- 

 nus, neogaeus, and eos, the ventral side of the bone is broad and relatively short (TS 

 48[ 1 ] ) and bears two conea (TS 49[0]; Fig.39B). In these three species, the anterior Co- 

 nus is broad, short, and surrounded by the arch-like posterior one. In other species of Pho- 

 xinus, the bone is relatively elongated and narrow (TS 48[0]), only one conus is present 



In the outgroups, the ventral side of the mesethmoid is narrow and relatively elongated, 

 but bears two conea. However, the relationships between the two conea in the outgroups 



47[0]). 



(TS 49[1]). 



Fig.38: Lateral view of eth- 

 moidal region of (A) Phoxi- 

 nus eos (KU 12255, 33.0 mm 

 SL), and (B) P. phoxinus (KU 

 22856. 58.0 mm SL). Scale 

 bar = 1 mm. 



A 



B 



