Sharks are among the most successful and enduring predators in the planet’s history, having survived multiple mass extinction events over immense stretches of time. Determining when the first shark was “discovered” depends on whether you mean the first fossil evidence or the first modern scientific classification. The true answer to their origin, however, is measured in hundreds of millions of years, placing their ancestry far deeper in time than dinosaurs or even most land vertebrates.
The Ancient Timeline of Shark Evolution
The earliest evidence of shark-like ancestors dates back approximately 450 million years, which places their origin in the Late Ordovician Period. These initial traces are microscopic scales, suggesting the presence of cartilaginous relatives even before the widespread appearance of jawed fish. During the subsequent Devonian Period, often called the “Age of Fishes,” the first recognizable shark-like forms diversified.
The appearance of confirmed members of the Elasmobranchii—the group containing sharks and rays—is rooted firmly in the Devonian. This means the earliest ancestors of modern sharks were swimming in the oceans over 200 million years before the first dinosaurs walked the Earth. This incredible antiquity highlights a lineage that has demonstrated remarkable evolutionary staying power.
Interpreting the Fossil Evidence
Scientists identify these ancient creatures primarily through their specialized hard parts, which are the only components robust enough to survive fossilization. The most abundant evidence consists of isolated teeth and dermal denticles—the tiny, tooth-like scales covering a shark’s skin. Since sharks continuously shed these structures, and because denticles are composed of durable dentine and enamel-like tissue, they form a continuous part of the fossil record.
One of the earliest and most complete genera found is Cladoselache, which lived during the Late Devonian around 370 million years ago. This fast-moving marine predator had a streamlined body and a mouth located at the front of its snout, unlike many modern sharks. Earlier still are the Acanthodians, sometimes called “spiny sharks,” a group of jawed fishes from the Silurian and Early Devonian that share features with cartilaginous fish. These early examples offer a rare glimpse into the morphology of the first shark-like forms.
Why the Record Remains Incomplete
The biggest challenge in piecing together the full history of sharks stems from their classification as cartilaginous fish (Class Chondrichthyes). Unlike bony fish, whose mineralized skeletons preserve well, a shark’s skeleton is made almost entirely of soft cartilage. Cartilage rarely survives decomposition and the pressure of fossilization, meaning complete fossilized skeletons are exceptionally rare finds.
When a shark dies, the collagen fibers in the cartilage disintegrate, causing the skeleton to fall apart quickly. This reliance on preserving only the hardest structures, like teeth and scales, creates gaps in the evolutionary story. Paleontologists refer to these missing periods, where little fossil evidence exists, as “ghost lineages,” which complicates the precise tracking of early shark diversification.
Major Evolutionary Branches and Modern Relatives
Following their initial appearance, sharks underwent several major evolutionary radiations, particularly during the Carboniferous Period, sometimes called the “golden age of sharks.” An extinction event at the end of the Devonian eliminated many competing fish species, allowing sharks to diversify significantly. Subsequently, a group called the Hybodonts emerged, becoming a dominant group of shark-like fish throughout the Mesozoic Era.
The Rise of Modern Sharks
The rise of modern sharks, the Neoselachians, occurred later, primarily during the Jurassic Period, around 200 to 150 million years ago. This is when the main orders of today’s sharks first evolved, such as the Lamniformes (mackerel sharks, including Great Whites) and the Carcharhiniformes (ground sharks). The most famous extinct species, Otodus megalodon, appeared during the Paleogene and Neogene periods, ruling the oceans until about 3 million years ago. The persistence of lineages like the cow and frilled sharks, whose fossil teeth date back nearly 190 million years, links the deep past to the species we observe in the oceans today.