Sexual dimorphism in plains minnow, Hybognathus placitus

Hybognathus placitus collected From several west Texas streams exhibit sexu al dimorphism in body form, which is unusual in cyprinids, Seventeen morpho logical measurements, including standard length, were made on 62 specimens and analyzed for sexual dimorphism. Partial warp scores were used to descri be sexual dimorphism in body shape. There was no difference in standard len gth between males and females (ANOVA, P = 0.9038, F-1.60 = 0.0147), but the re was a highly significant (MANOVA, F-1.60 = 4.78, P < 0.001) sexual dimor phism in body shape. Overall, males have relatively longer first dorsal fin rays, larger heads, and caudal peduncles, whereas females are deeper bodie d and have relatively longer trunks, from the pelvic fin insertion to the a nal vent, Differences between male and female H, placitus in length of the first dorsal fin ray are readily apparent and can potentially be used for f ield identification.