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Evolution in the Pacific

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Notable Fossil Finds:


  • The remains of thousands of animals from more than 600 species have been found in Los Angeles's La Brea tar pits since 1901. Many of these animals, which lived between 40,000 and 8,000 years ago, are now extinct in North America, including native horses, camels, mammoths, and saber-toothed cats.

  • In 1997, a virtually complete mastodon skeleton was found in Modoc County, Calif. The 12-foot long, 12-foot tall creature lived between 3 million years ago and 10,000 years ago. With only the animal's tusks missing, the skeleton is among the state's best-preserved fossils.

  • In 1992, a lava tube containing hundreds of bird skeletons was found on the slopes of Hualalai, Hawaii. Among the extinct species were a giant, flightless goose and the largest honeycreeper ever discovered. The bones suggest that seed-eaters, plant-eaters, insect-eaters, and flesh-eaters once inhabited Hawaii's forests.

  • In the early 1900s, a graveyard of 225-million-year-old porpoise-like marine reptiles called ichthyosaurs was discovered a mile above sea level in Berlin, Nev., in the Shoshone Mountains. Over several years, the remains of 37 ichthyosaurs were found at this site. (See one at the Las Vegas Museum of Natural History.)

  • In 1868, ichthyosaur vertebrae were discovered in the New Pass Range in north-central Nevada. This was America's best-known ichthyosaur before the Berlin discoveries.

  • Beginning in the 1850s, a bone bed at Sharktooth Hill near Bakersfield, Calif., has yielded fossils of 125 species of sharks, bony fishes, marine mammals, sea turtles, crocodiles, birds, and land mammals. Eighteen of these were species never before been identified.

  • From 1960 to 1963, during a major excavation on Sharktooth Hill, the near-complete skeleton of a 15-million-year-old sea lion was discovered. Another mostly complete specimen was discovered nearby several years later.

  • In 1971, the complete skeleton of an extinct flightless goose was found on Molokai, Hawaii, in a sand dune.

Endangered Species:

Photo of Mauna Kea silversword The following animal and plant species are among those listed in the federal government's register of endangered species in this region.


 Mauna Kea silversword

Mauna Kea silversword (flowering plant)

  • Appearance: Silvery, dagger-like leaves spread out in a rosette two feet in diameter; a five-foot-tall stalk produces hundreds of small sunflowers perhaps only once in 50 years
  • Habitat: The last naturally occurring population (50 plants) lives on the slopes of Mauna Kea volcano at altitudes of 9,000 feet and higher
  • Threat: Introduced species (esp. sheep, goats, and insects); because native pollinating insects are in decline, and because plants are now spread so far apart, many are hand-pollinated
  • Fast fact: Of the state's more than 260 endangered plants, 16 species have only one plant remaining in the wild, 68 have ten or fewer, and 169 have a hundred or fewer.

California kangaroo rats (land mammals)

  • Appearance: Brown to yellowish-brown with a long tail and long hind legs used for hopping (4 to 14 inches, excluding tail)
  • Habitat: Underground burrows, where they store food -- which includes seeds, leaves, and other plant parts, as well as insects -- for the winter
  • Threat: Habitat loss to development, pesticides, domestic cats
  • Fast fact: Of the six endangered kangaroo rat species, fewer than 60 Morro Bay kangaroo rats were recently counted, and giant kangaroo rats inhabit an area of only five square miles.

Hawaiian hoary bat (land mammal)

  • Appearance: Compared with other hoary bats, the Hawaiian subspecies is much smaller, reddish (not gray-brown) in color, and lacks the characteristic white tinge (wingspan: six to seven inches)
  • Habitat: Roosts in trees or small caves on Hawaii's big island, Lanai, and Maui and feeds on moths, mosquitoes, and termites
  • Threat: Habitat loss to deforestation
  • Fast fact: This is Hawaii's only native land mammal and one of the world's rarest bats.

California condor (bird)

  • Appearance: Adults, which are black with white under their wings, have bald yellow, red, or orange heads. This condor is one of the world's largest flying birds. (wingspan: 9 feet)
  • Habitat: Forages in grasslands at lower elevations; nesting sites are located at higher elevations on cliffs
  • Threat: Habitat destruction, collisions with man-made structures (buildings, power lines)
  • Fast fact: With populations down to about 20 individuals in the 1980s, all remaining animals were captured for their protection. Beginning in 1992, some were released back into the wild.

Ash Meadows Amargosa pupfish (fish)

  • Appearance: A small, chubby fish, with a proportionally long head and lower than average number of scales and fin-rays (1.3 inches)
  • Habitat: Confined to warm springs in the Amargosa Desert (Nevada); feed on blue-green algae and small invertebrates
  • Threat: Previously, diversion of springs for irrigation; now, introduced species (esp. crawfish and bullfrogs)
  • Fast fact: Ash Meadows's 50 freshwater springs support perhaps the highest number of endemic species than any other place in the U.S.
Geology:

California and Nevada
Until about 300 million years ago, the entire west of what is now North America was covered by shallow seas. For this reason, the only fossils of early life in the region were left by marine plants and animals. Reminders of this watery heritage -- shells and imprints of ancient bivalves, snails, and squid -- are found in the Great Basin, the vast depression between the Rocky Mountains and the Sierra Nevada ranges.

Between 225 and 65 million years ago -- the dinosaur age -- much of the non-mountain west was again underwater. For this reason, dinosaur fossils are rare in the region. Some of the dinosaurs' marine contemporaries, though, including sharks, jellyfishes, and highly diverse marine reptiles, are well known to fossil collectors. Nevada's Shoshone Mountains, a full mile above sea level, contain a graveyard of porpoise-like ichthyosaurs.

Glaciers never reached as far south as Nevada and California, but climate was cooler and much wetter during the last Ice Age, which began 2 million years ago. Large lakes covered what is today arid land. The Pacific region's fossil record of Ice Age land animals is extensive. Mastodons, saber-toothed cats, and giant ground sloths all appear among the thousands of creatures trapped in California's La Brea tar pits.

Hawaii
Hawaii, an island chain born from volcanoes, dates only to the Miocene epoch -- well after the dinosaur extinction. The oldest island, only 6 million years old, is the smallest, while the youngest, at 1 million years old, is the biggest. Hawaii's fossil record is limited by its relative youth. Limestone and lava tubes have preserved thousands of skeletons, however, including those of extinct creatures like a flightless goose. Birds and bats, which are Hawaii's only two native land vertebrates, probably didn't evolve on the islands until volcanoes had eroded and formed enough soil for plants to grow in.



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