Tiny holes in three fossil clams reveal that by 75 million years in the past, historic octopuses had been deviously drilling into their prey. The discover pushes proof of this conduct again 25 million years, scientists report February 22 within the Organic Journal of the Linnean Society.
The clams, Nymphalucina occidentalis, as soon as lived in what’s now South Dakota, the place an inland sea divided western and jap North America. Whereas inspecting the shells, now on the American Museum of Pure Historical past in New York, paleontologists Adiël Klompmaker of the College of Alabama in Tuscaloosa and AMNH’s Neil Landman noticed telltale oval-shaped holes. Every gap was between 0.5 and 1 millimeters in diameter, thinner than a strand of spaghetti.
A contemporary octopus makes use of a pointy ribbon of tooth known as a radula on its tongue to drill a gap into thick-shelled prey — helpful for when the shell is just too robust for the octopus to pop aside with its suckers. The octopus then injects venom into the outlet, paralyzing the prey and dissolving it a bit, which makes for simpler consuming. Octopus-drilled holes had been beforehand present in shells courting to 50 million years in the past, however the brand new discover suggests this drilling behavior advanced 1 / 4 million years earlier of their historical past.
Such drill holes increase the scant fossil document of octopus evolution. The smooth our bodies of the intelligent, eight-armed Einsteins don’t lend themselves properly to fossilization, tending as a substitute to decay away (SN: 8/12/15). What fossils do exist — a handful of specimens courting to about 95 million years in the past — recommend little change within the primary physique plan from historic to trendy octopuses.
The discover additionally places the evolution of octopus drilling squarely throughout the Mesozoic Marine Revolution, an escalation within the historic arms race between ocean predators and prey (SN: 6/15/17). In the course of the Mesozoic Period, which spanned 251 million to 66 million years in the past, predators lurking close to the seafloor grew to become adept at crushing or boring holes into the shells of their prey.