Shane Gross / American crocodile (Crocodylus acutus) with open mouth amongst Seagrass (Alismatales). Gardens of the Queen National Park, Cuba.

Mark Bowler / Isula / Bullet ant (Paraponera clavata) close-up showing mandibles, Peru

Franco Banfi / Killer whale (Orcinus orca) jaw with four teeth, on sand, washed up on beach. Vrangel Bay, Primorsky Krai, Russia.

Franco Banfi / Jawbone of extinct Gamssulzen cave bear (Ursus ingressus) that lived in Central Europe during the late pleistocene. Krizna Jama / Cross cave, Loz valley, Bloska Polica, Slovenia.

Emanuele Biggi / Stag beetle (Prosopocoilus spp.) close up of manibles, occurs in Southeast Asia.

Ingo Arndt / Alpine marmot skull {Marmota marmota}

Edwin Giesbers / Jaguar (Panthera onca) female yawning, native to Southern and Central America, captive

Doug Perrine / Snaggletooth shark (Hemipristis elongata) teeth from lower jaw, on display at Oceanographic Museum of Monaco, Principality of Monaco (digitally modified)

Doug Perrine / Snaggletooth shark (Hemipristis elongata) teeth from upper jaw, on display at Oceanographic Museum of Monaco, Principality of Monaco (digitally modified)

Doug Perrine / Whorl tooth shark (Helicoprion bessonovi) fossil mould of the spiral lower jaw tooth whorl, 245-290 million years, on display at Oceanographic Museum of Monaco, Principality of Monaco (digitally modif...

Doug Perrine / Shortfin mako shark (Isurus oxyrinchus) teeth from upper jaw on display at Oceanographic Museum of Monaco, Principality of Monaco (digitally modified)

Doug Perrine / Zebra shark (Stegostoma fasciatum) detail of lower jaw teeth used for crushing shells of molluscs and crustaceans, and for grasping small fish, Birch Aquarium, La Jolla, California, USA