100 



As a whole, the dentary is relatively short and blunt in P. issykkulensis, brachyurus, and 

 eos (TS 103 [1]); it is relatively slender and elongated in other species of Phoxinus (TS 

 103[0]). The coronoid process is perpendicular to the anterior portion of the dentary, and 

 not posteriorly sloped to the dorsal margin of the dentary in P. cumberlandensis, issykku- 

 lensis, oreas, and phoxinus (TS 1 04 [ 1 ] ) ; it is sloped to the dorsal margin of the dentary 

 in other species of the genus (TS 104 [0]). The dentary is slender, and the coronoid pro- 

 cess is sloped to the dorsal margin of the dentary in the outgroups. 

 Retroarticular (Figs.59A-B, 60A-C. 61A-B). The retroarticular is a triangular en- 

 dochondral bone. It articulates with posteroventral side of the anguloarticular dorsally and 

 ventroposterior portion of the dentary anteriorly. It is well-developed, its length is longer 

 than one-third of the anguloarticular's total length in P. phoxinus (TS 105 [ 1 ] ). It is less 

 developed, its length is much less than one-third of the anguloarticular 's length in other 

 species of Phoxinus and in the outgroups (TS 105[0]). 



Sesamoid bone (or sesamoid articular) (Figs.59A-B, 60A-C, 61A-B). The sesamoid 

 bone is a dermal element and located at the medial side of the anguloarticular and of the 

 dentary. It is irregular-shaped with individual variations. The variation of phylogenetic sig- 

 nificance is in the relationship between the sesamoid bone and the dentary. In P. oreas, 

 erythrogaster, and cumberlandensis, about one-third of the sesamoid bone overlaps the 

 dentary (TS 106[0]); whereas about half of the sesamoid bone overlaps the dentary in 

 other species of Phoxinus (TS 106[ 1 ]). 



In the outgroups, the sesamoid bone is knife-shaped and only one third of the bone over- 

 laps the dentary. 



Anguloarticular (Figs.59A, B, 60A-C, 61A-B). The anguloarticular is placed at po- 

 steromedial side of the dentary, and extends to middle of the dentary. The anguloarticu- 

 lar articulates with the retroarticular ventrally and with quadrate ventroposteriorly. 



Fig. 61: Lower jaw of some species of Phoxinus in lateral (a) and medial (b) views. A: P. tennes- 

 seensis (UT 44.5274, SL 50.0 mm): B: P. erythrogaster (KU 5773. SL 52.5 mm SL). Scale bars = 1 

 mm. 



