Some ammonites had long, straight shells, while others had helix-shaped shells. Most species, however, had coiled shells lined with progressively larger chambers separated by thin walls called septa.

Ammonites' growing shells typically formed into a flat spiral, known as a planispiral, although a variety of shapes did evolve over time. Shells could be a loose spiral or tightly curled with whorls ...

Miners Looking for Ammonite Stumble on Rare Complete Fossils of 'Ocean Predators' From 100 Million Years Ago Evidence of ...

1. Research ammonites and find your favourite species. Ammonites came in a variety of shapes and sizes. Pay attention to features including shell shape, the presence of any ribs, and ornamentation ...

and notable among them is the death of another species. A new study published in Nature Communications has overturned the long-held belief that ammonites were in decline before their extinction 66 ...

Fossils found in the northern part of Hokkaido are a new type of ammonite, the once-ubiquitous spiral-shelled creatures that went extinct with the dinosaurs 65 million years ago, researchers said.

Global warming triggered by heavy volcanic activity is hypothesized by some scientists to have caused the end-Triassic extinction event that obliterated up to 80 percent of Earth’s species. These ...

His attention was particularly directed to the Brachiopoda and Ammonites of the Inferior Oolite ... was led to create a multitude of genera and species far beyond what had hitherto been deemed ...