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Bailey and Cross (1954) measured morphological characteristics of pallid <br />sturgeon collected from the middle and lower Missouri River and middle <br />Mississippi River. They found the ratio between the lengths of the inner and <br />outer barbels of pallid sturgeon and shovelnose sturgeon to be one of the <br />quickest and most reliable means for separation of these two Scaphirhynchus <br />species: the outer barbel is 1.2 -1.5 times longer than the inner barbel in <br />the shovelnose and 1.7 to 2.4 times longer in the pallid. Bailey and Cross <br />(1954) also found that the inner barbels of pallid sturgeon typically lie <br />ahead of the outer barbels, unlike on shovelnose sturgeon, where they are <br />typically in -line. Furthermore, in pallid sturgeon, all the barbels are <br />further back on the lower surface of the snout than in shovelnose sturgeon: <br />the "snout tip to outer barbel /mouth to inner barbel" ratio varies from 2.3 to <br />3.3 in pallid sturgeon and 1.3 to 2.2 in shovelnose sturgeon (Bailey and Cross <br />1954) (Figure 1). <br />A 1.3 -2.2 A - 2.3 -3.3 <br />C E- 1.1 -1.4 E- 1.6 -2.0 <br />B in F - 4.0 -5.0 Bin F - 5.5 -7.0 <br />A - 1.3 -2.5 A - 2.6 -3.7 <br />shovelnose C in D - 1.2 -1.5 C in D - 1.7 -2.4 pallid <br />Sturgeon F - 3.6 -5.8 F - 6.3-8.0 Sturgeon <br />K NI <br />D <br />N 1 <br />Figure 1: Comparative diagrams of the ventral surface of the head of <br />shovelnose sturgeon and pallid sturgeon, showing several measurement <br />ratios of value for identification. Redrawn from Bailey and Cross <br />(1954). <br />