74 



lateral ethmoid expands forming a triangular-shaped portion. Posteriorly, the lateral eth- 

 moid is triangular-shaped. Anteriorly, the lateral ethmoid is similar to its posterior view 

 in shape. Medially, the medial side of the bone is concave and bears a notch at its ven- 

 tral margin. The bone has a T-shaped ridge-like appearance dorsally. 

 Variation of the lateral ethmoid among Phoxinus species affects its shape. Ventrally, the 

 anterior and posterior portions are acute in P. cumberlandensis and erythrogaster (TS 

 50[0]; Fig.39D). In P. erythrogaster, the anteroventral portion is elongated and forms a 

 process. The anterior and posterior portions of the ventral aspect are blunt in other spe- 

 cies of Phoxinus (TS 50[1]; Fig.39C). 



The concave medial side bears a notch at its dorsal margin in P. tennesseensis and cum- 

 berlandensis (TS 51[1]) (Fig.39D); the notch is not present in other species of Phoxinus 

 (TS 51[0]; Fig.39C). 



In the outgroups, the anterior and posterior portions of the ventral aspect of the lateral 

 ethmoid are acute; no notch is present at the dorsal margin of the medial aspect of the la- 

 teral ethmoid. 



Orbital Region 



Located posteriorly to the ethmoidal region, the orbital region consists of orbitosphenoid. 

 pterosphenoid, frontal, supraorbital, and infraorbital bones. 



Frontal (Figs 40A-F). In cyprinids, the frontal is the largest bone in the neurocranium 

 (but in Aristichthys the frontal is a small bone - Ramaswami 1955a), and forms the an- 

 terodorsal cover of braincase. Shape of the frontal varies from short and broad (e.g., Rho- 

 deus) to very slender and elongated (e.g., Elopichthys bambusa, Luciobrama 

 macrocephalus - Howes 1978, Chen 1987c). Dorsally, it shares a suture with the supra- 

 ethmoid anteriorly, lateral ethmoid anterolaterally, sphenotic posterolaterally, and parietal 

 posteriorly. In some cyprinids, there is a small fontanel between the anterior margin of 

 the frontal and the posterior margin of the supraethmoid (e.g., species of Aristichthys) 

 (Ramaswami 1955a). The left and right frontals meet one another at their mesial margins 

 with slight overlap. Ventrally, the frontal meets the lateral ethmoid anteriorly, orbitosphe- 

 noid and pterosphenoid laterally. Anteriorly, the frontal roofs the posterior part of the 

 olfactory capsule. 



In Phoxinus, frontal sutures with other bones similar to that in other cyprinids. The fon- 

 tanel between frontal and supraethmoid is absent in the genus. The frontal is a rectangular- 

 shaped bone with a posterolateral process at posterior portion of the lateral margin and an 

 anterior process at its anterior margin. The posterior margin of the posterolateral process 

 sutures with the anterior margin of the sphenotic. Shape of the posterolateral process varies 

 among the species of Phoxinus. The posterolateral process is sharp and elongated in P. 

 neogaeus, issykkulensis, brachyurus, and phoxinus (TS 52[1]); the process is relatively 

 short and broad in other species of Phoxinus (TS 52 [0]) and in the outgroups. Thus the 

 elongated and sharp posterolateral process is proposed as an apomorphic condition, and 

 the short and broad one a plesiomorphic condition. 



The frontal bears the supraorbital canal in Phoxinus. The supraorbital canal might be con- 

 tinuous or inteiTupted. On the ventral side of the frontal bone in Phoxinus three concavi- 



