National Geographic - USA (2019-12)

Lower

jaw

Rounded teeth

Upper

jaw

Section view (front)

Upper,

ded teeth Adult

Four rotations

New tooth

formed

here

Great white

Helicoprion

Juvenile

Two rotations

Newest

tooth

First

three

teeth

New tooth

One

rotation

40 ft, maximum length

Helicoprion Narrower body

Great white

20 ft

Gum

line

Root

Root

Enamel

Modern sharks shed old teeth to make

way for new ones. Helicoprion juveniles

were born with three teeth they never lost;

new teeth shifted old ones in rotations

of up to 150 teeth encased in cartilage

and attached to a single root.

WHIRLING INTO ADULTHOOD

he jaw snapped shut, it forced

ged spiral into a notch in the upper

d with small, rounded teeth. Prey

ckly sliced in two and swallowed.

Actual size

of teeth from a

large whorl fossil

1.5 feet in diameter

Fossil

Reconstruction

ice

EQUATOR

osphoria Sea

LaurussianSeaway

Paleotethys

Neotethys

PANTHA

LAS

SA

NTH
ALASS
A

PA

NG

AE

A

daho, U.S. Kazakhstan

Ural MRussiats.,

Australia

Mexico

Canada

Japan

islandsArctic

Laos China

EQUATOR

OCEANATL.

OCEANPACIFIC

OCEANPACIFIC

INDIANOCEAN

AFRICA ASIA

AUS.

EUR.

SOUTHAMER.

N. AMER.

Idaho, U.S. Ural MRussiats.,

Modern fossil sites 282–275 million years ago Number of fossils found since 1886: 1 2-5 25 100

RAPHIC MAP) PHOTO: EVELYN VOLLMER AT IDAHO VIRTUALIZATION LAB, IDAHO MUSEUM OF NATURAL HISTORY

DECODER FERNANDO G. BAPTISTA AND PATRICIA HEALY