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similarities are due to convergent evolution and that they are not a monophyletic group (Birstein <br />et al. 2002; Dillman et al. 2007). <br />Morphology, Meristics and Morphometrics: <br />In general, pallid sturgeon are similar in appearance to shovelnose sturgeon. The primary <br />differences, noted in the original description, between the two species were the number of ribs <br />(21 to 22 in pallid vs. 10 or 11 in shovelnose), the naked breast and belly in pallid sturgeon and <br />the presence of sub-rhombic plates on the shovelnose sturgeon, and the length of the air bladder <br />to standard length (8 times in pallid sturgeon and 5 times in shovelnose) (Forbes and Richardson <br />1905). <br />Subsequent analyses by Bailey and Cross (1954) illuminated other differentiating <br />meristic and morphomeric characteristics. This suite of differences between pallid and <br />shovelnose sturgeon led to the development of a number of Morphological Character Indexes <br />(Bailey and Cross 1954; Keenlyne et al. 1994b; Sheehan et al. 1999) designed to aid in species <br />identification. These morphological character indexes have proved useful for field identification <br />of the different sturgeon species. Recent studies have built upon previous work and used several <br />qualitative characters such as the shape of papillae on the barbells and lip lobes and the shape of <br />gill rakers to distinguish pallid sturgeon from shovelnose sturgeon (Kuhajda et al. 2007). One <br />issue with the use of morphological character indexes is how to assign individuals with <br />intermediate meristic and morphometric characters which are suspected to be hybrids between <br />shovelnose and pallid sturgeon (Bailey and Cross 1954; Carlson et al. 1985; Keenlyne et al. <br />1994a; Murphy et al. 2007a; Murphy et al. 2007b; Sheehan et al. 1999). These assignments have <br />been facilitated by the development of genetic markers.