Ammonites: From Ocean Hunters to Shelf Decor

Practice fill-in-the-blank flashcards covering the evolutionary timeline, morphology, biomineralization, ecology, and extinction causes of ammonites based on the lecture notes.

Ammonites were coiled shelled cephalopods that ranged in size from less than $2\,\text{cm}$ to over __________ in diameter.

$$2\,\text{m}$$

Extant Nautilus and extinct ammonite reconstructions display a striking visual resemblance despite having __________ evolutionary lineages.

independent

The subclass Ammonoidea is grouped into three major geological index orders: Goniatitida, Ceratitida, and __________.

Ammonitida

The first documented historical record of ammonites was written in 77 CE by Pliny the Elder, who called them __________.

Ammonis cornua

Ammonites were named for the resemblance of their coiled fossils to the curved horns of the Egyptian ram-god __________.

Ammon

Modern scientific biostratigraphy was established in the 1850s by Friedrich Quenstedt and __________.

Albert Oppel

The internal phragmocone shell of an ammonite is divided into gas- and fluid-filled chambers called __________.

camerae

An organic strand called the __________ runs through the shell chambers along the ventral margin to regulate hydrostatic buoyancy.

siphuncle

The comparative evolutionary sequence of cephalopod suture patterns progressed from simple nautiloid lines to Goniatitic, Ceratitic, and complex fractal __________ walls.

Ammonitic

The outer shell of an ammonite is constructed from calcium carbonate __________ crystals within a protein matrix.

aragonite

Gem-grade Canadian Ammolite forms exclusively in the __________ Formation in Alberta.

Bearpaw

The iridescent rainbow colors of ammolite are produced by microscopic stacked aragonite layers reflecting light through __________ wave interference.

constructive

During the Late Cretaceous, the Western Interior Seaway divided North America into Laramidia and __________.

Appalachia

Ammonites hunted small crustaceans and zooplankton using a feeding organ called a __________ and a sharp chitinous beak.

radula

Fossilized shells of Placenticeras sp. frequently exhibit double-row V-shaped bite marks left by predatory marine reptiles known as __________.

mosasaurs

The Chicxulub asteroid impact occurred 66 million years ago when an asteroid struck the __________ Peninsula.

Yucatán

Planktonic ammonitella hatchlings were exceptionally vulnerable to ocean acidification because their ultrathin aragonite shells dissolved rapidly in __________ surface waters.

acidic

While an extreme r-selected reproductive strategy doomed ammonites, modern nautiloids survived by employing a __________ strategy with large benthic eggs.

K-selected

In medieval English folklore, fossilized coiled ammonites were believed to be petrified headless snakes known as __________.

serpentstones

Following the extinction of ammonites, their vacated ecological niches were subsequently colonized by early marine mammals and modern __________ fish.

teleost