. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 26 Bulletin Museum of Comparative Zoology, Vol. 146, No. 1. Fig. 10. Am'ia calva (648 mm SL) caudal: A, Whitehouse (1910) and Lund's (1967) definition of first ural; B, Nybelin's (1963) definition of first ural; C, first fused ural. 3992). The range for the number of centra in this region of Recent A. calva is 33 to 37. There is considerable variation in total number of centi'a {, segments) in Recent A. calva (81-90), which may pose a prob- lem in comparing specific vertebrae. Thus in two A. calva, for example, th
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 26 Bulletin Museum of Comparative Zoology, Vol. 146, No. 1. Fig. 10. Am'ia calva (648 mm SL) caudal: A, Whitehouse (1910) and Lund's (1967) definition of first ural; B, Nybelin's (1963) definition of first ural; C, first fused ural. 3992). The range for the number of centra in this region of Recent A. calva is 33 to 37. There is considerable variation in total number of centi'a {, segments) in Recent A. calva (81-90), which may pose a prob- lem in comparing specific vertebrae. Thus in two A. calva, for example, the eightieth vertebral segment of one individual might not correspond to the same position in the vertebral column or even type of centrum as the eightieth segment of the second indi- vidual. This should be considered in any comparisons of several A. calva individuals, as well as in comparisons of the fossil forms, which share this variation in vertebral seg- ments (Table 9). Also, fusion of vertebral elements may occur in Recent A. calva. In some specimens, as many as five centra were found fused together at points throughout the vertebral column; this con- dition was present to a lesser degree or absent in other specimens (Tables 10-12). These fused centra also occur in the fossil forms, as in A. uintaensis (YPM 6244). The actual number of such fused centra can often be established only by counting ex- ternal features such as basapophyses, neural facets, aortal facets, or haemal facets. Romer and Fryxell's (1928) study of "Paramiatus gurleyi" is the only pubHshed description of a complete articulated fossil amiid. They distinguished this form from the Recent species by the supposed pres- ence of a deeper body, and also noted that the number of centra was considerably less than in A. calva. The vertebral column is completely preserved, so that it is possible to obtain an accurate count of the vertebrae (Plate IB). "Paramiatus p,iirleyi" has 67 vertebral segm
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