ammonoid
Ancient coiled shellfish
Ammonoids are an extinct group of marine mollusks related to modern squids and nautiluses, known for their distinctive coiled shells divided into chambers.
Their fossils are abundant worldwide, making them useful for dating rock layers: The ammonoid fossils date this formation to the Jurassic.
The group includes ammonites, the most familiar members.
Flexible grasping appendages
- beakHorny avian mouthpart
- septaAnatomical partition walls
- suturesMedical wound closures
- chambersEnclosed functional rooms
aperture · keel · ribs · nodes · umbilicus · whorl · coiling · shell
Chambered marine mollusk
- cephalopodTentacled marine mollusk class
- molluskSoft-bodied invertebrate, often shelled
- belemniteExtinct squid-like mollusk
- squidTen-armed marine mollusk
octopus · cuttlefish · gastropod · bivalve · invertebrate
Complete vanishing of a species
- DevonianGeologic period, 419-359 million years ago
- CarboniferousCoal-depositing geological period
- PermianLate Paleozoic geological period
- TriassicFirst Mesozoic period
Jurassic · Cretaceous · Mesozoic · Paleozoic · evolution · phylogeny · diversification · radiation
Curve winding around center
- logarithmicBased on exponents
- whorlSpiral arrangement of ridges
- coilingLooping around repeatedly
- uncoiledReleased from spiral form
helix · involute · ornamentation · ribs · tubercles · spines · keel · symmetry
Organic remains becoming mineral
- petrifiedSolidified or fear-paralyzed
- amberHardened ancient tree secretion
- excavationAct of unearthing
- preservationMaintaining something's condition
mold · cast · impression · concretion · matrix · specimen · collecting · preparation
tentacles
Flexible grasping appendages
chambers · aperture · keel · ribs · nodes · umbilicus · whorl · coiling · shell · nacre
nautilus
Chambered marine mollusk
- cephalopodTentacled marine mollusk class
- molluskSoft-bodied invertebrate, often shelled
- belemniteExtinct squid-like mollusk
squid · octopus · cuttlefish · gastropod · bivalve · invertebrate
extinction
Complete vanishing of a species
- DevonianGeologic period, 419-359 million years ago
- CarboniferousCoal-depositing geological period
- PermianLate Paleozoic geological period
Triassic · Jurassic · Cretaceous · Mesozoic · Paleozoic · evolution · phylogeny · diversification · radiation · morphology
spiral
Curve winding around center
- logarithmicBased on exponents
- whorlSpiral arrangement of ridges
- coilingLooping around repeatedly
uncoiled · helix · involute · ornamentation · ribs · tubercles · spines · keel · symmetry · dimorphism
fossilization
Organic remains becoming mineral
- petrifiedSolidified or fear-paralyzed
- amberHardened ancient tree secretion
- excavationAct of unearthing
preservation · mold · cast · impression · concretion · matrix · specimen · collecting · preparation · display
ocean
Massive saltwater body
benthic · nekton · currents · marine · reef · Tethys · predation · prey · belemnite · nautiloid