San Diego Natural History Museum
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Geologic Timeline: The last 144 million years of Earth's 4.6 billion year history.
Crab carapace.
Crab carapace is specimen 3581-59775
Left claw is specimen 3168-24395
Right claw is specimen 3552-66159.
From Chula Vista.

FOSSIL FIELD GUIDE

Cancer sp. cf. C. antennarius
Rock crab
Cancridae

Time
Pliocene Epoch

In Our Region
Cancer antennarius is known from at least 123 fossil locations in several Upper and Lower Pleistocene formations from Baja California to the San Joaquin Basin. Pliocene occurrences are known in the San Diego Formation, Etchegoin Formation, and at San Ysidro, Baja California. The geographic range of the species has never been wider than it is today.

Description
Worldwide, the genus Cancer is widely distributed in temperate oceans, being represented by 23 Recent (modern) species. In addition, there are about two dozen fossil species, a few of which come from Miocene-aged deposits (as old as 23.8 million years before present). On the West Coast, fossil occurences of the genus Cancer extend from Coos Bay, Oregon to Bahia del Rosario, Baja California, Mexico. Each of the nine Recent species of Cancer on the west coast of North America also are known as fossils.



Text and photos by Scott Rugh, Collections Manager, Invertebrate Fossils

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Pleistocene Epoch 1.8 million-10,000 years ago.
Pliocene Epoch 5-1.8 million years ago.
Miocene Epoch 24-5 million years ago.
Oligocene Epoch 34-24 million years ago.
Eocene Epoch 53-34 million years ago.
Paleocene Epoch 65-55 million years ago.
Cretaceous/Tertiary Boundary Rock, 65 million years ago.
Cretaceous Period 144-65 million years ago.
Earth's history began 4.6 billion years ago.
MYA = million years ago.