Acipenserid

1989, Laurie J. Bryant, Non-dinosaurian Lower Vertebrates Across the Cretaceous-Tertiary Boundary in Northeastern Montana, Geological Sciences: Volume 134, University of California Press, page 17, A second distinct acipenserid morphotype occurs in the Hell Creek and Tullock formations. It is not found in the Lance Formation in Wyoming, although acipenserids are so rare in the Lance Formation that this is possibly the result of sampling error.

While acipenserid outgroups lack any extensive scalation, the most distinctive hallmark of acipenserids is their scutes (Character 1).

Why is it that shortnose sturgeon - the far more residential of the two sturgeons - appears to nearly stop growing at adulthood and at a small size for an acipenserid whereas the more marine Atlantic sturgeon continues to grow and to a potentially massive size?