The difference between ammonites and nautiloids can be a little confusing for the average person. Both are mollusks, but they have different shells and inhabit different parts of the ocean. Ammonites are more common in sediments on the sea floor, while nautiloids are usually found in shallower water. Nautiloids also have a more complex shell than ammonites. If you’re ever unsure which one you’re looking at, just remember that ammonites always have a winding shell, while nautiloid shells are straight.
What is Ammonite?
Ammonites are an extinct group of marine mollusk animals in the subclass Ammonoidea of the class Cephalopoda. These mollusks are more closely related to living coleoids (i.e. octopuses, squid, and cuttlefish) than they are to shelled nautiloids such as the living Nautilus species. The earliest ammonites appear during the Devonian period, and the last species died out during the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and it is often possible to link a particular rock layer to the time period in which it was deposited.
Their fossil shells usually take the form of planispirals, although there were some helically spiraled and nonspiraled forms (known as heteromorphs). Ammonites varied in size from less than 1 cm (0.4 in) in diameter to over 1 m (3 ft 3 in). These creatures lived in shallow water, either floating or crawling along the sea bottom. They are thought to have preyed on fish and other small marine animals.
What is a Nautiloid?
Nautiloids are a group of cephalopods that includes the living Nautilus species and their extinct relatives. These creatures are characterized by a hard, protective outer shell that contains chambers filled with gas. Nautiloids use these chambers to maintain buoyancy, and they also use them to control their movement through the water.
Nautiloids are thought to have first appeared during the Cambrian period, and they quickly diversified into a wide variety of shapes and sizes. Over time, however, nautiloids declined in diversity, and today only a handful of species remain. Nevertheless, these fascinating creatures continue to captivate the imaginations of scientists and laypeople alike.
Difference between Ammonites and Nautiloids
Ammonites and nautiloids are both members of the cephalopod family, which also includes squid, octopus, and cuttlefish. Ammonites are extinct relatives of the squid, while nautiloids are closely related to the modern-day squid. Both ammonites and nautiloids had coiled shells and lived in the ocean. However, there are several key differences between these two groups of cephalopods. Ammonites had a simple spiral shell, while nautiloids had a complex,multi-chambered shell.
Ammonites also had shorter tentacles than nautiloids, and they did not have an ink sac. These differences likely reflect the different ecological niches occupied by these two groups of cephalopods. Ammonites were likely bottom-dwellers that scavenged for food, while nautiloids were agile predators that hunted for live prey. Despite their different lifestyles, both ammonites and nautiloids were successful groups of cephalopods that thrived for millions of years.
Conclusion
The difference between ammonites and nautiloids is an important distinction for paleontologists and collectors. Ammonites are more common, but nautiloids often have a more intricate shell. Understanding the difference between these two types of cephalopods can help you identify fossils with greater accuracy and know what to look for when collecting specimens.
