During which geological period did the order Xenacanthiformes first appear?
Answer
Devonian Period
The evolutionary timeline for the order encompassing *Xenacanthus*, the Xenacanthiformes, begins in the Devonian Period. This indicates that this lineage of sharks existed even before the major terrestrial expansion was fully established. While the order had a long temporal span, persisting until the Early Cretaceous Period, its origins trace back significantly into the earlier Paleozoic era, showcasing remarkable evolutionary persistence across hundreds of millions of years, including surviving several major extinction events.
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?