Oklahoma's number one blog for natural and cultural history.

 

Inside the Treasure Box: Week Nine

Some 455 million years ago, long before the wind came sweeping down the plains, Oklahoma was nothing more than a fragment of the ocean floor. A diverse array of marine life inhabited the waters above the future United States and left behind a rich prehistoric past. How do invertebrate paleontolgoists know all of this? Though these early sooners may be long gone, their skeletons remain.

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Trilobites embedded in limestone

This specimen, from the invertebrate paleontology department, is one of several slabs of limestone crowded with complete skeletons of the trilobite Homotelus. Trilobites are extinct marine arthropods that disappeared roughly 250 million years ago. In case you need a refresher, arthropods are a classification of animals with segmented bodies and external skeletons, like scorpions, crabs and butterflies.

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The Asian forest scorpion is an example of an arthropod.

The trilobite specimen shown above is important to scientists because it provides a snapshot into the behavior of these arthropods. Complete skeletons of trilobites are rare, as they would normally fall apart quickly after death. It is highly unusual to find hundreds of skeletons clustered together this way, as a result. Invertebrate paleontolgoists believe that the trilobites may have gathered in large numbers to spawn, much like modern horseshoe crabs along the east coast of the United States. 

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Horseshoe crabs

It’s also important to note that geography played a prominant role in the recovery of this specimen. Geological evidence indicates that the embedded trilobites were buried very quickly by mud, possibly by a storm close to shore that would have stirred up the sea floor and carried mud-laden waters offshore. After the storm waned, this mud was likely dumped on the sea bottom, burying the trilobites. Nearly 455 million years later, scientists discovered their skeletons, still intact, buried in the Ordovician rocks of the Criner Hills in southern Oklahoma.

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The Criner Hills are in Carter County, Okla.

Thanks to this discovery, invertebrate paleontologists now have a unique glimpse into the life of extinct animals. They also know that the reproductive behavior of trilobites resembles modern marine arthropods. Of course, you don’t have to look 455 millions years into the past to see Oklahoma’s astounding contributions to history. In fact, next week we’ll be looking at a more recent group of Oklahomans. Can you guess who?