The Molluscan Shell: Patterns, Some More Complex and Evolution Showcase the Reign of the Ammonites Beautiful Than Others
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Ammonites had one very Molluscs important feature: older parts of Both cephalopods and gastropods belong to Utah Museum of Natural History their shells were sealed off as & The Olivera Laboratory the same large invertebrate group: the mol- the animal grew. This created lusca. Most of the soft-bodied creatures in this air-filled chambers in the shell, which helped the group have hard shells, which means they are animal to float. We can see the well preserved in the fossil record. chambers in the shells, marked by The Molluscan Shell: patterns, some more complex and Evolution Showcase The reign of the ammonites beautiful than others. These At the time of the dinosaurs, the ammonites patterns are seen in these baculite were widespread in prehistoric oceans. They examples. The modern nautilus has a similar shell were very successful creatures. Although structure. Yet, despite the similarities between commonly coiled, as seen in some examples nautilus and ammonites, the latter failed to survive here, the ammonites took on other forms in the the mass extinction that also killed the dinosaurs. Cretaceous period, uncoiling themselves in various ways. The long, straight shell of the Cone Shells Some shells of Molluscs that are common today baculites is just one of the forms that the am- are not found in Henrieville or sites of similar age. monite shell took. It seems that the baculites This is the case for the cone shells, a more recently F rom Ocean Bottom were in their heyday when the Henrieville site evolved group. Yet, in a site formed in the to the Hilltops of was formed, and their shells are among the mountains of Austria, 15 million years later than largest and most impres- Henrieville, there are remains of turret snails. And Southern Utah sive of the Henrieville tucked into the crevices of the fossil plate fossils. In this example containing these turrets is a small we can see several bacu- cone snail fossil. From this we lite shells fossilized in the can tell that cone snails appeared same nodule. Presumably, sometime between the they all perished together. disappearance of the ammonites and the formation of this Austrian fossil. We know that ammonites and baculites lived Learn more about the Olivera Lab in: together because in fossil The Glory of the Sea: Mollusc Shells and the Animals In- side Them sites of the same age as An exhibit developed by the Utah Museum of Natural His- Henrieville we see fossil tory in collaboration with the Olivera Lab plates covered with both On display at: forms. This also shows The Utah Museum of Natural History their abundance at the 1390 E. Presidents Circle, Salt Lake City 2/12/10 – 9/3/10 time. Coiled ammonite shell Baldomero (Toto) Olivera and Caitriona Gunning Photos by Kerry Matz Thanks to Jim Jenks for the loan of his fossils UMNH & Olivera Lab F rom Ocean Bottom.. to the Hilltops of Southern Utah Utah´s Fossils Jim Jenks Turritella Jim Jenks, who has spent a lifetime collecting, Also found at the Henrieville site is a long, Utah is famous for its dinosaur fossils. We researching and preparing Triassic coiled shell known as a turret shell (Turritella) can picture their huge forms roaming East- ammonoids, found many of these fossils in Hen- that was probably the second most common ern and Southern Utah. Imagine a different rieville, Utah. As a young geologist he studied snail species at Henrieville. scene. Imagine Southern several fossil sites in the Intermountain West. Turret shells are a very Utah as part of a prehis- One of these sites was Henrieville, a spot just successful group today, with toric ocean during the over 80 different species living east of Bryce Canyon where outcrops of the Cretaceous period, as in all the oceans of the world. Tropic Shale Formation are widespread. shown on this map. Its This image shows a turret shell inhabitants include some sharing a fossil plate with the remnants of a rod- Jim Jenks discovered strange marine creatures that we no longer Marine Snail Fossils like baculite shell. see today. his first fossils while found at Henrieville Sometimes, in one nodule, we find an Aporrhais in Junior High in This exhibit shows some of the diversity of While many of the or turret shell juxtaposed with other types of Montana. He found the marine creatures that lived in Utah in the fossils found there are shells, such as ammonites (above, and center some clam shells and Cretaceous period. extinct creatures, some front cover image). This indicates that these a dinosaur bone. species lived and died at the same time. In much of Southern Utah, there is a geo- of the shells recovered F rom that day on, by However, while some of these species live on logical layer called the Tropic Shale forma- from the Henrieville his own admission, today, like the gastropods Aporrhais and tion, which formed at the bottom of the nodules are strikingly Turritella, others, like the ammonites, are ocean, 70 million years ago. In SouthWest- similar to shells that live extinct. ern Utah, this layer is exposed on the sur- in today´s oceans. Ammonites face of the land, on the hill tops where wind One of these is the Pelican´s Foot shell has eroded away top layers of the earth. The rod-like baculite in the center front cover (Aporrhais pespelecani) that now lives in the Here in the rock lie the fossilized remains of picture belongs to the same group as the coiled Atlantic Ocean. Today there are fewer species marine animals. shells: the ammonites. Ammonites are than there were 70 million years ago. At the cephalopods. They are extinct creatures which How are these fossils found? Henrieville site, one species in particular, Apor- belong to the same family as nautilus and squid. Nodules that look like smooth grey rocks rhais prolabiata is very common. In form, it is are found on the surface of this layer. Each quite similar to some of Here is an ammonite fossil nodule is believed to be formed by the death the modern shells. The found in Henrieville. It is of an animal millions of years ago. By care- image on the right shows coiled in the classic fully removing the surrounding rock, the fossilized shells next to a ammonoid shape. It also has fossil can be exposed. modern shell. Notice ridges, which may have acted how similar they are. as armor for the shell. Map: Ron Blakey NAU Geology .