Dinosaurs in California
Dinosaurs in California
Very few dinosaur fossils
have been found in California. Why?
Becuase during the time when dinosaurs lived, most of California was covered
by the ocean, and any sediments that accumulated in the areas that were dry
land have since eroded away. Why do we find dinosaur fossils in areas that
were ocean? They may have drowned in a river and been carried out to sea
by currents, as happens sometimes to large mammals today. We know that the
dinosaur skeletons were deposited in the ocean because we find shells of
marine animals where they grew on the dinosaur bones as well as in the
Dinosaur Bones : On the left, you can compare the size of a hadrosaur
femur (thigh bone) with the paleontologist who found it. On the right, a
Nodosaurus tibia (shin) that later became a home for oysters when the
bone was washed out to sea.
Hadrosaurs from California
(duck-billed dinosaurs) were common large herbivorous dinosaurs
that lived near the end of the Cretaceous, at the same time as
Triceratops and Tyrannosaurus. Most of the dinosaur fossils
found in California are isolated bones of hadrosaurs, which can be identified
by their distinctive arrangement of knobs and muscle attachment scars.
In 1987, part of the skeleton of a type of armored dinosaur called a
nodosaur was found in an excavation near Carlsbad. This was the first of
this type of dinosaur found west of the Rocky Mountains, and provided
important evidence about connections between the west coast and the interior
of the United States. The nodosaur is very similar to species known from
Wyoming and Kansas, which supports the idea that dinosaurs on the west coast
were part of a cosmopolitan fauna rather than a unique regional group.
Dinosaur Armor : On the left, a portion of the sacral (hip) armor
from a nodosaur found in the Pt. Loma Formation of California. On the
right is a single large platelike scute, also from a nodosaur's armor.
Oysters grew on dinosaur skeletons
This armored dinosaur skeleton found in Carlsbad, California, had shells of
oysters and rock scallops attached to the bones, in addition to many shells
of marine animals in the surrounding rock. (See the picture near
the top of this page.) Why were there shells on the bones?
Oysters need a solid surface to attach to and live on. On a soft, muddy
seafloor, hard surfaces are scarce, and large bones that stick up out of the
mud may be the only place for oysters to live. During the Cretaceous,
dinosaur bones on the seafloor provided a home for oysters and other animals
that needed a solid foundation to grow on.