Sharks survived five mass extinctions before trees even existed on land

Nature · Published 24 October 2026 Swipe more like this →

In short: While dinosaurs were still a distant dream, sharks were already perfecting their craft. These cartilaginous predators have navigated 450 million years of oceanic history, evolving from toothless ancestors into the diverse array of apex hunters and bizarre deep-sea dwellers we recognize today.

Sharks are among the most enduring lineages on Earth, having survived five distinct mass extinction events. Their evolutionary journey began approximately 450 million years ago during the Late Ordovician Period. However, identifying the 'first' shark remains a subject of scientific debate. While fossil evidence from this era includes shark-like scales, no teeth have been found, leading researchers to question whether the earliest forms were actually toothless or if the scales belonged to unrelated animals. These ancient creatures have inhabited our oceans for hundreds of millions of years. They are often incorrectly labeled as living fossils despite their significant evolutionary changes.

The group is defined by their cartilaginous skeletons—flexible tissue that makes up nearly their entire structure, with teeth being a notable exception. This lineage includes not only famous predators like great whites and whale sharks, but also rays, skates, sawfishes, guitarfishes, and the elusive chimaeras (also known as ghost sharks). Molecular evidence suggests that chimaeras diverged from the rest of the group roughly 420 million years ago, a period that coincided with the first plants invading land. Modern chimaera species currently reside primarily in deep ocean environments. This group includes various names like rabbit fish and ratfish.

The transition to more recognizable shark anatomy continued into the Early Devonian Period. The oldest shark-like teeth discovered date back 410 million years and belong to Doliodus problematicus. Despite its name, this species is described as the 'least shark-like shark,' originating from a group called acanthodians or spiny sharks, which possessed diamond-shaped scales and spines in front of their fins rather than the classic shark silhouette. These spiny sharks featured distinct diamond-shaped scales on their bodies. They also possessed prominent spines located ahead of all their fins.

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