Cretaceous Dinosaurs 
15 
TABLE 1. Hypsibema crassicauda and H. missounense, measurements of centra in 
mm (slightly corrected for abrasion). Data on largest vertebra of H. missounense 
(USNM 16735) from Gilmore and Stewert (1945). 
Maximum length 
Maximum width at posterior end 
Height at center of posterior end 
ANSP 
USNM 
ANSP 
USNM 
15338 
7189 
15308 A 
16735 
114 
113 
93 
91 
105 
100 
79 
87 
82 
65 
56 
91 
bed was the McNairy Sand Member of the Ripley Formation, considered 
early Maestrichtian in age. In analyzing these vertebrae Gilmore ex- 
plicitly noted their similarity to Hypsibema crassicauda ; but accepting 
without question the hadrosaurian nature of the latter, he dismissed it 
from comparison on the grounds that the vertebrae from Missouri could 
not pertain to a member of the Hadrosauridae. Now that Hypsibema has 
been freed of hadrosaurian encumbrances its generic identity with 
Parrosaurus becomes obvious. Every morphological feature cited for the 
Missouri vertebrae can be matched in those from North Carolina. Indeed, 
the possibility of specific identity cannot be dismissed: but until better 
material is available we prefer to maintain Hypsibema missounense 
(Gilmore), n. comb., as a separate species. 
\ 
Affinities of Hypsibema . — A genus known only by its tail bones is 
necessarily somewhat difficult to characterize and classify. Regrettably, 
the meager sampling of dinosaur bones from North Carolina affords no 
additional element that can be attributed to Hypsibema crassicauda. Even 
more regrettably, no attempt has apparently been made to recover the 
rest of the skeleton of H. missounense which (we suspect) lies buried a few 
meters underground on the Chronister farm. At present the caudal ver- 
tebrae provide the only basis for comparison. 
Hypsibema shares with the Hadrosauridae its slightly amphicoelous 
caudal centra, the amidships position of its neural arch, and the shortness 
of its anterior zygapophyses. Within that family (as John S. McIntosh has 
pointed out to us) Hypsibema bears some similarity to a series of 
diminutive caudal vertebrae assigned to Orthomerus transylvanicus by 
Nopcsa (1928, PL 6, Fig. 4). But otherwise, as Gilmore justly noted in his 
analysis of Parrosaurus , the caudals are distinctly un-hadrosaurian. Con- 
spicuously lacking, indeed, is the feature that appears to have been a 
basic adaptation of the hadrosaurs: a laterally-compressed tail height- 
ened by neural and haemal spines to form an effective propulsive organ 
for swimming. The Ceratopsia and Ankylosauria are excluded from com- 
parison by the relative shortness of their caudal centra, while the other 
