What prominent structure projects backward from the nape of the Xenacanthus skull?
Answer
A stiff spine
The most recognizable feature defining the genus *Xenacanthus* is a prominent, stiff spine that projects posteriorly from the nape area of its skull. This cephalic spine is the reason for its name and serves as the primary diagnostic feature for paleontologists examining its fossils. This specialized projection is hypothesized to have served either a defensive function against predators attempting head-first strikes or perhaps acted as an element crucial for sexual display during mating rituals, contrasting sharply with the dermal armor of contemporaneous bony fishes.
Related Questions
What does the name Xenacanthus mean, hinting at its unusual feature?How is the general body plan of Xenacanthus described compared to modern sharks?What unique feature defined the fin arrangement of Xenacanthus along its back?What prominent structure projects backward from the nape of the Xenacanthus skull?During which geological period did the order Xenacanthiformes first appear?During which geological periods did the genus Xenacanthus achieve its peak activity?What habitat did Xenacanthus appear to remain steadfastly in throughout its documented history?What two main purposes have paleontologists hypothesized for the Xenacanthus cephalic spine?Within which order is Xenacanthus classified as a sister group or early branch?What factor might have gradually caused the final disappearance of Xenacanthus in the Early Cretaceous?