What unique feature defined the fin arrangement of Xenacanthus along its back?
Answer
Two separate dorsal fins
A key distinguishing characteristic of *Xenacanthus*, setting it apart from the morphology common to most modern sharks, was its dorsal fin configuration. This ancient cartilaginous fish possessed two distinct, separate dorsal fins positioned along its back. This feature, combined with a single anal fin and a V-shaped tail fin, contributed to a body layout markedly different from the classic shark template. The presence of this dual dorsal fin structure is a fundamental trait classifying it within the order Xenacanthiformes.
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?