114 



In Phoxinus the subopercle is an elongated triangular bone; thus three angles can be re- 

 cognized, i.e., the anterodorsal, anteroventral, and posterior angles. The subopercle is broa- 

 der at its anterior portion than at its posterior portion. The dorsal and ventral margins of 

 the bone are much longer than the anterior margin. The posterior angle is elongated and 

 blunt. The anterodorsal angle might be acute or blunt with intraspecific variation. The an- 

 teroventral angle is blunt. In P. neogaeus, issykkulensis, and tennesseensis, the anterior 

 margin of the bone is straight (TS 141 [1]); in other species of Phoxinus and in the out- 

 groups, the margin is concave (TS 141 [0]). 



Branchial Region 



Bones included in the branchial region are pharyngobranchials, epibranchials. ceratobran- 

 chials, hypobranchials, basibranchials, and pharyngeal bones. These bones form the gill 

 arch. They can be grouped into two sets, i.e., the dorsal and ventral elements. The dorsal 

 elements include epibranchials and pharyngobranchials, both of which are suspended on 

 the ventral aspect of neurocranium. The ventral elements include rest of the bones. 

 Pharyngobranchials (PHB, Fig.72A-F). In cyprinids, the pharyngobranchials are 

 placed at the dorsomedial portion of the gill arches and contact the ventral side of the pa- 

 rasphenoid. There are four paired elements, i.e., pharyngobranchials 1, 2, 3, and 4 (from 

 anterior to posterior). Pharyngobranchials 2 and 3 are fused in cyprinids (Chen 1986b. 

 Mayden 1989); whereas the pharyngobranchial 4 is a cartilage present in some species 

 only (e.g., Luciobrama macrocephalus - see Howes 1978). Howes (1978) and Kim & 

 Kang (1986) recognized the two pharyngobranchials (PHB 1, and 2+3 herein) in cypri- 

 nids (their infrapharyngobranchials) as the pharyngobranchials 2 and 3. the cartilage in 

 front of the first pharyngobranchial was interpreted as the pharyngobranchial 1 . 

 In Phoxinus, pharyngobranchial 1 (Fig.72A-F) articulates with epibranchials 1 and 2 la- 

 terally, and pharyngobranchial 2+3 posteriorly. The bone is crescent and shallowly con- 

 cave at its medial margin. The anterior portion of the pharyngobranchial 1 is broader than 

 the posterior portion of the bone, its posterior margin is not forked in P. brachyurus, pho- 

 xinus, neogaeus, eos, tennesseensis, oreas, cumberlandensis, and ei~y thro gast er (TS 

 142[0]); especially in P. neogaeus, the anterior portion of the bone is much broader than 

 its posterior portion, and the bone is wedge-shaped. In P. issykkulensis. the posterior por- 

 tion of the pharyngobranchial 1 is broader than the anterior portion of the bone, its po- 

 sterior margin is deeply forked (TS 142[ 1 ] ). 



In the outgroups, the pharyngobranchial 1 is crescent, the anterior portion is broader than 

 the posterior portion, its posterior margin is not forked. 



Pharyngobranchial 2+3 (Fig.72A-F) is an elongated bone; it is larger than, and located 

 posteriorly to pharyngobranchial 1 . It articulates with pharyngobranchial 1 anteriorly, epi- 

 branchials 2 and 3 laterally, and pharyngobranchial 4. if any. posteriorly. 



Pharyngobranchial 2+3 is crescent-shaped in P. eos, oreas, erythrogaster, tennesseensis. 

 and cumberlandensis (TS143[1]). The bone bears a concavity at its lateral and medial 

 sides, the posterior portion of the bone is generally broader than the anterior portion in P. 

 neogaeus, phoxinus, brachyurus, issykkulensis, and the outgroups (TS 143[0]). In P. neo- 

 gaeus, the concavity is not well developed. 



