Localities of the Cretaceous:

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 surrounding sediments.

Hadrosaur femur Oyster on dino bone
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

Hadrosaurs (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.

Armored Dinosaur

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.

Nodosaur armor isolated scute
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.