What morphological feature did the caudal fin of Xiphactinus share with modern tuna?
Answer
Deeply forked shape
The caudal (tail) fin of *Xiphactinus* possessed a deeply forked shape. This specific morphology is a significant indicator of an animal evolved for high cruising speeds and sustained swimming performance. This adaptation is comparable to that seen in modern, fast-swimming pelagic species like tuna, suggesting that *Xiphactinus* relied on speed and endurance, powered by a streamlined, muscular body structure, to pursue its prey effectively through the open waters of the seaway.
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