108 



metapterygoid. hyomandibular, symplectic and quadrate are chondral bones; whereas, the 

 entopterygoid and ectopterygoid are dermal elements (Arratia & Schultze 1991). 

 Entopterygoid (Figs.67A-D, 68A-D). In cyprinids, the entopterygoid is an irregularly 

 shaped plate-like dermal bone and located anteriorly to the metapterygoid. It sutures with 

 the anterior margin of the metapterygoid posteriorly, dorsal margin of the quadrate and 

 ectopterygoid ventrally, and posterior end of the autopalatine anteriorly. 

 In Phoxinus, variations of the entopterygoid are in two aspects: the general shape and the 

 articulation with the autopalatine. The entopterygoid is long (anterior-posterior dimensi- 

 on) and relatively narrow (ventral-dorsal dimension) in P. issykkulensis, tennesseensis, and 

 cumberlandensis (TS 122[1]); whereas the bone is short and relatively broad in other spe- 

 cies of Phoxinus (TS 122[0]). In P. eos, erythrogaster, and phoxinus, the entopterygoid 

 articulates with the posterior end of autopalatine (TS 123[1]); in other species of Phoxi- 

 nus and in the outgroups, it articulates with almost half of the autopalatine (TS 123[0]). 

 Ectopterygoid (Figs.67A-D, 68A-D). In cyprinids, the ectopterygoid is a small dermal 

 bone placed at the anteroventral side of the entopterygoid. Its posterior side articulates 

 with the anterior margin of the entopterygoid and the quadrate. The ectopterygoid is nar- 

 row, slender, and crescent in P. neogaeus, issykkulensis, erythrogaster, and phoxinus (TS 

 124[1]); it is relatively short and broad in other species of Phoxinus and in the outgroups 

 (TS 1 24[0] ). The ectopterygoid does not overlap the anterior portion of the entopterygo- 

 id in P. erythrogaster, issykkulensis, phoxinus, tennesseensis, and cumberlandensis (TS 

 1 25[ 1]); the ectopterygoid partially overlaps the entopterygoid in other species of Phoxi- 

 nus and in the outgroups (TS 125[0]). The dorsal margin of the ectopterygoid is far away 

 from the posterior end of the autopalatine in P. tennesseensis, issykkulensis, neogaeus, 

 erythrogaster, oreas, eos, and in the outgroups (TS 126[0]); whereas the two bones are 

 close to each other in other species of Phoxinus (TS 126[1J). 



Autopalatine (Figs 67A-D, 68A-D). This small endochondral bone is located at the an- 

 terior portion of the Suspensorium. The anterior portion of the autopalatine articulates with 

 the supraethmoid via a ligament, and connects with the kinethmoid, vomer, maxilla, and 

 infraorbital bone 1 anteriorly. The posterior portion of the autopalatine articulates with the 

 anterior margin of the entopterygoid posteriorly. As discussed under "ectopterygoid," the 

 relative position between the posterior end of the autopalatine and dorsal margin of the 

 endopterygoid varies among the species of Phoxinus. 



In Phoxinus, the autopalatine is a short bar- shaped bone with a forked structure at the an- 

 terior end. The shape of this forked structure shows intraspecific variation. Variation with 

 phylogenetic significance includes two aspects. In P. phoxinus, eos, cumberlandensis, and 

 issykkulensis, the autopalatine is short, slender, and not well-developed (TS 1 27[ 1 ]) when 

 the similar sized specimens of other Phoxinus species and outgroups are compared (TS 

 127[0]). In P. phoxinus and eos, the dorsal and ventral margins are concave (TS 128[1]); 

 the margins are almost straight in other species of Phoxinus and in the outgroups (TS 

 128[0]). 



Quadrate (Figs.67A-D, 68A-D). In cyprinids, the quadrate is located ventral to the ento- 

 pterygoid and anterior to the metapterygoid. It articulates with the symplectic dorsally, 

 and with the anguloarticular ventroanteriorly. 



