Ptychodus decurrens is an extinct durophagous (shell crushing) shark. The name Ptychodus comes from the Greek words ptychos (fold/layer) and odon (tooth). The teeth fit together like paving stones to form a plate on both the lower and upper jaws. The teeth are rounded and are used for crushing and grinding. Their jaws had as many as 550 teeth, with about 220 in the lower jaw and about 260 in the upper jaw.
They lived during the Late Cretaceous (65.5 million years ago). They swam in the shallow sea which extended from the current Gulf of Mexico to Canada. The sea included the states of Texas, Oklahoma, Kansas, Colorado, Nebraska, the Dakotas and Canada. Their diet consisted of mollusks, shell fish, crustaceans, and occasionally scavenged carcasses. Ptychodus grew to about 33 feet long.
This specimen is from South Dakota.
Kingdom: Animalia, Phylum: Chordata, Class: Condrichthyes, Order: Hybodontiformes, Family: Ptychodontidae, Genus: Ptychodus, Species: decurrens.
Ptycodus decurrens - tooth 
Quantity in Basket: None
Code: TMPD-105
Price: $40.00
Shipping Weight: 0.30 pounds
Time: Late Cretaceous 65.5 million years ago.
Location: South Dakota.
Dimensions: 3/4"W x 9/16"H