Know your teeth.

The 'crow shark' was a Cretaceous opportunist — a scavenger that left bite marks on hadrosaur and mosasaur bones across the Western Interior Seaway. Its leaf-shaped, coarsely serrated teeth are the everyday currency of New Jersey's Cretaceous creek beds.

The biggest of the crow sharks. Broader, more triangular, and noticeably larger than S. kaupi. Latest Cretaceous — the genus made it almost to the K-Pg extinction.

An ancestral mackerel shark and the great-grandparent of Otodus and the megalodon lineage. The narrow blade with sharp triangular cusplets at the shoulders is unmistakable once you've seen one.

An ancestor of the modern goblin shark. Tall, narrow, awl-like teeth made for grabbing — not slicing — soft prey in deep water. The fine vertical lines on the enamel are diagnostic.

Not a shark — a 40+ foot marine lizard that ruled the Late Cretaceous seas. Its teeth are conical, faceted, and unmistakable once you've held one. A complete mosasaur tooth from a NJ creek is a find of a lifetime.

The 'Ginsu shark' — a 20+ foot apex predator of the Western Interior Seaway. Smooth, broad triangular teeth that look like an unsherrated meg in miniature. Famously preserved as articulated skeletons in the Niobrara Chalk of Kansas.

An ancestral mackerel shark and the great-grandparent of Otodus and the megalodon lineage. The narrow blade with sharp triangular cusplets at the shoulders is unmistakable once you've seen one.

The dominant sand tiger of the Eocene. Tall, slender, slightly recurved blades with a pair of pointed lateral cusplets. The 'workhorse' tooth of phosphate-mine spoil piles in the Carolinas and the bagged Aurora gravels.

The most common 'pretty' tooth — a slender awl-shaped spike with two needle-like cusplets, one on each shoulder. Hasn't changed much in 50 million years.

The dominant sand tiger of the Eocene. Tall, slender, slightly recurved blades with a pair of pointed lateral cusplets. The 'workhorse' tooth of phosphate-mine spoil piles in the Carolinas and the bagged Aurora gravels.

Megalodon's transitional ancestor. Looks almost identical to a small meg but retains tiny lateral cusplets — vestiges of its Otodus ancestry — that disappear entirely in true megalodon.

The grandparent of megalodon — a 30-foot apex predator of Oligocene seas. Its hallmark prominent triangular cusplets give it away instantly.

The most common 'pretty' tooth — a slender awl-shaped spike with two needle-like cusplets, one on each shoulder. Hasn't changed much in 50 million years.

The undisputed king of fossil teeth. Reached an estimated 50–60 feet long and ruled coastal seas worldwide for 20 million years before vanishing in the Pliocene. A complete 5"+ tooth is the find of a lifetime.

Megalodon's transitional ancestor. Looks almost identical to a small meg but retains tiny lateral cusplets — vestiges of its Otodus ancestry — that disappear entirely in true megalodon.

The likely ancestor of today's great white shark. Its smooth blade — sharp as a scalpel — was perfected for slashing fast prey in Miocene oceans.

Often called the 'unmistakable' tooth — a sharply curved cockscomb with a deeply notched, double-serrated edge that hasn't changed in 15 million years.

A collector favorite. Lower teeth are tall and narrow with a smooth blade; upper teeth flare into wickedly serrated leaves. The contrast in the same jaw makes this species unmistakable.

A small carcharhinid often confused with juvenile tiger sharks. Its blade is twisted (contortus) — almost corkscrewing as it curves.

The most common 'pretty' tooth — a slender awl-shaped spike with two needle-like cusplets, one on each shoulder. Hasn't changed much in 50 million years.

Stout, broad triangular blade with fine serrations — a workhorse of the Carcharhinid family. The bulk and broad root tell it apart from sand tigers and tigers.

A narrow smooth-bladed tooth with a flat root and fine serrations only at the very base of the blade. Often mistaken for sand tigers.

The undisputed king of fossil teeth. Reached an estimated 50–60 feet long and ruled coastal seas worldwide for 20 million years before vanishing in the Pliocene. A complete 5"+ tooth is the find of a lifetime.

The likely ancestor of today's great white shark. Its smooth blade — sharp as a scalpel — was perfected for slashing fast prey in Miocene oceans.

Modern apex predator. Recent (sub-fossil) teeth wash up on Florida and Georgia beaches alongside Pleistocene specimens.

Often called the 'unmistakable' tooth — a sharply curved cockscomb with a deeply notched, double-serrated edge that hasn't changed in 15 million years.

A collector favorite. Lower teeth are tall and narrow with a smooth blade; upper teeth flare into wickedly serrated leaves. The contrast in the same jaw makes this species unmistakable.

The most common 'pretty' tooth — a slender awl-shaped spike with two needle-like cusplets, one on each shoulder. Hasn't changed much in 50 million years.

The shortfin mako — fastest shark in the ocean. Recent and Pleistocene teeth wash up frequently on Florida beaches, often paler than their Miocene cousins.

Stout, broad triangular blade with fine serrations — a workhorse of the Carcharhinid family. The bulk and broad root tell it apart from sand tigers and tigers.

A narrow smooth-bladed tooth with a flat root and fine serrations only at the very base of the blade. Often mistaken for sand tigers.

Modern apex predator. Recent (sub-fossil) teeth wash up on Florida and Georgia beaches alongside Pleistocene specimens.

Often called the 'unmistakable' tooth — a sharply curved cockscomb with a deeply notched, double-serrated edge that hasn't changed in 15 million years.

The most common 'pretty' tooth — a slender awl-shaped spike with two needle-like cusplets, one on each shoulder. Hasn't changed much in 50 million years.

The shortfin mako — fastest shark in the ocean. Recent and Pleistocene teeth wash up frequently on Florida beaches, often paler than their Miocene cousins.

Stout, broad triangular blade with fine serrations — a workhorse of the Carcharhinid family. The bulk and broad root tell it apart from sand tigers and tigers.

A narrow smooth-bladed tooth with a flat root and fine serrations only at the very base of the blade. Often mistaken for sand tigers.

Modern apex predator. Recent (sub-fossil) teeth wash up on Florida and Georgia beaches alongside Pleistocene specimens.

Often called the 'unmistakable' tooth — a sharply curved cockscomb with a deeply notched, double-serrated edge that hasn't changed in 15 million years.

The most common 'pretty' tooth — a slender awl-shaped spike with two needle-like cusplets, one on each shoulder. Hasn't changed much in 50 million years.

The shortfin mako — fastest shark in the ocean. Recent and Pleistocene teeth wash up frequently on Florida beaches, often paler than their Miocene cousins.

Stout, broad triangular blade with fine serrations — a workhorse of the Carcharhinid family. The bulk and broad root tell it apart from sand tigers and tigers.

A narrow smooth-bladed tooth with a flat root and fine serrations only at the very base of the blade. Often mistaken for sand tigers.