While it is a prominent feature of the body plans of numerous animals today, tracing the origin of these structures has proven very difficult.įossils of tubular (tube-like) exoskeletal assemblages, like those of G. The animal skeletal system is thought to have emerged 550–520 million years ago during the Cambrian explosion. This animal inhabited the region millions of years ago during the Cambrian Period, and was possibly one of the first animals to have evolved a functioning exoskeleton. The 514 million year old fossils, discovered by a team of researchers in Yunnan, China, consist of multiple preserved forms of the now-extinct Gangtoucunia aspera. These forms are characterized by an interwoven suture called the ammonite pattern.Scientists have recently unearthed a collection of ancient fossils that might hold the key to finally understanding the evolutionary history and origin of the animal skeletal system. Most ammonoid genera became extinct at the end of that period, but a few survived and evolved into many diverse forms during the Cretaceous Period. Ammonoids characterized by a more highly folded suture, called ceratite, replaced the goniatites and were most abundant in the Triassic Period (252 million to 201 million years ago). Those with a simple suture pattern, called goniatite, flourished during the Paleozoic Era (541 million to 252 million years ago). Three groups of ammonoids succeeded one another through time, each group having a more complex suture pattern. Ammonoids are important index fossils because of their wide geographic distribution in shallow marine waters, rapid evolution, and easily recognizable features. Ammonoids are characterized and distinguished from nautiloids by the highly crenulated and complex suture that occurs where internal partitioning walls come in contact with the outer shell wall. The shells, which are either straight or coiled, served as protective and supportive structures as well as hydrostatic devices, enabling the animal to compensate for varying water depths. There is evidence that these animals consumed zooplankton, crustaceans, and other ammonoids. The ammonoids were shelled forms, and nearly all are thought to have been predacious in habit. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!Īmmonoid, also called ammonite, any of a group of extinct cephalopods (of the phylum Mollusca), forms related to the modern pearly nautilus ( Nautilus), that are frequently found as fossils in marine rocks dating from the Devonian Period (began 419 million years ago) to the Cretaceous Period (ended 66 million years ago).Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.Demystified Videos In Demystified, Britannica has all the answers to your burning questions. This Time in History In these videos, find out what happened this month (or any month!) in history.
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