ammonites

Extinct spiral mollusks

Ammonites are extinct marine mollusks with distinctive spiral shells, related to modern nautiluses.

Their fossils are among the most recognizable, appearing in rocks from the Devonian through Cretaceous periods.

The shells divided into chambers, with the animal occupying only the outermost one.

Geologists use ammonite fossils to date rock layers because different species existed during specific time periods.

The cliff face was studded with ammonites. (Capitalized Ammonites refers to a biblical people.)

cephalopod

nautilus

Chambered marine mollusk

molluskSoft-bodied invertebrate, often shelled
tentaclesFlexible grasping appendages
shellHard outer covering

chambered · septa · cephalopod · belemnite · squid · octopus · cuttlefish · marine · carnivore

fossil

paleontology

Study of ancient organisms

CretaceousFinal Mesozoic period
JurassicDinosaur-dominated geological period
MesozoicAge of Reptiles

fossilization · excavation · sedimentary · stratigraphy · petrified · preservation · specimen · imprint · cast · mold

shell

spiral

Curve winding around center

whorlSpiral arrangement of ridges
coilWound circular arrangement
ribbedWith raised parallel lines

chambered · suture · keel · spines · ornamentation · aperture · umbilicus · venter · septum · uncoiled

Categories

Mesozoicdinosaurs, Velociraptor, Brachiosaurus, Spinosaurus, pterosaurs
Extinct Animalsdinosaur, dinosaurs, tyrannosaurus, dodo, mammoth
extinct creaturesdinosaurs, trilobites, mammoths, pterosaurs, plesiosaurs
fossilsdinosaur bones, amber, fossils, fossil, fossil bones
natural history museumfossils, dinosaurs, specimens, taxidermy, gemstones
natural history museumsdioramas, taxidermy, specimens, exhibits, displays

Opposites

evolutionary status

ammonitesnautiluses

Cephalopods with spiral shells

chambered nautilus · octopuses · living fossils · cuttlefish · squids

Family

Familiarity: Top 500,000
Profile: Used worldwide · Timeless · Concrete · Rated G