Cymbospondylus

Mixosaurus

Ichthyosaurs In Kern County
Submitted by Ben Nafus
Paleo Artwork By Ben Nafus

The oldest fossil found in Kern County dates back 220 million years(MY) to the middle Triassic Period, Ladinian Age times when the all of California was sea bottom with perhaps a few islands dotting the tropical sea surface. Swimming in these waters were the first of the Ichthyosaurs, a group of marine reptiles that appear suddenly in the fossil record without any known origin. It is agreed among the experts that they are the first of those animals to have returned to a totally marine life from terrestrial beginnings from somewhere on the supercontinent, Pangaea. As a group of marine predators, they were very successful, living over 160(MY) to finally die out about ten million years before the last of the dinosaurs went extinct 65 million years ago.

The first ichthyosaur found be found in Kern Co. was unearthed in the northwestern corner of the county near Orchard Peak. Unfortunately, the fragmented fossils could not be assigned to any particular genus. However, considering the age of the formation, early, middle Triassic, in which the fossils were found, two genera become apparent. The first: Cymbospondylus, has a primitive reptile appearance without any dorsal fin or a fishlike tail. Further, the fish-like shape of the short, inefficient appearing paddles suggests that the animal used the lateral undulations its long flat tail to propel it through the water. The second is Mixosaurus, which like Cymbospondylus, had the typically long ichthyosaur, beaklike jaws equipped with conical shaped sharp teeth commonly used by four legged fish eaters.

Here, these two genera's description depart: Mixosaurus took on a more dolphin shape with the tail resembling that of a very early Devonian fish. Clearly, it used its improved paddles to propel and steer its torpedo like body through the water more efficiently. These, with the addition of shark-dolphin like dorsal fin on the animal's back provided greater stability and maneuverability, and developed a very effective predator that could speed after its prey at speeds of between 25 to 40 miles per hour.

References: Dupras, D. 1988, Ichthyosaurs of California, Nevada, and Oregon. Used with the permission by the California Department of Conservation, Division of Mines and Geology. Dixon, D., Cox, B., Savage, R., Gardiner, B., and McKenna M. 1988, The MacMillan Illustrated Encyclopia of Dinosaurs and Prehistoric Animals.

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