85 



Fig.48: Pterotic of (A) Phoxinus erythrogaster (KXJ 5773, 51.5 mm SL), and (B) P. cumberlanden- 

 sis (KU 18934, 52.0 mm SL) (a: ventral view; b: dorsal view). Scale bars = 1 mm. 



In the outgroups, the epioccipital is more or less rectangular; it bears a small sharp pro- 

 cess at its posterior margin, and its anterior concavity on the ventral side bears no small 

 deeper "subconcavity". 



Intercalar. The intercalar is a small paired endochondral bone placed at the postero- 

 ventral side of the pterotic. It is triangular in shape and does not vary significantly among 

 Phoxinus species. 



Pterotic and lateral extrascapula (Figs.44A, B; 48A, B). Dorsally, in Phoxinus, the 

 pterotic sutures the sphenotic anteriorly and epioccipital posteromedially. Ventrally the 

 pterotic sutures the sphenotic anteriorly, the prootic mesially, and the exoccipital posteri- 

 orly. The dorsal aspect of the pterotic is partially overlapped by the lateral extrascapular 

 and the posttemporal in some species of the genus. The posterior portion of the pterotic 

 forms the anterior part of the subtemporal fossa, and the lateral portion of the pterotic 

 forms the dorsolateral portion of hyomandibular fossa. 



The pterotic is irregular-shaped in Phoxinus. The dorsal aspect (dermopterotic) of the 

 pterotic is plate-like. The otic canal of the cephalic lateral line runs on the dorsal side of 

 the bone. At the anterior part of the bone, an anteriorly directed process is present in most 

 Phoxinus species (TS 75[1]), but the process is absent in P. tennesseensis, oreas, and 

 erythrogaster (TS 75 [0]). A posteriorly directed process varying among the Phoxinus spe- 

 cies exists on the posterolateral margin of the pterotic. The process is long and acute in 

 P. cumberlandensis (TS 76[1]), but short and blunt in other species of Phoxinus and in 

 the outgroups (TS 76 [0]). 



Ventrally, the pterotic bears two concavities, i.e., the anterior and posterior concavities se- 

 parated by ridges. The anterior concavity, with the concavity formed by prootic, forms the 

 otic capsule. The medial concavity forms part of subtemporal fossa. 



