#ammonites

• Acanthoceras — A genus of extinct fossil cephalopod mollusks (ammonites) within the Acanthoceratidae family, characteristic of the Late Cretaceous epoch. These marine organisms were distinguished by their massive, planospiral coiled shells heavily ornamented with prominent ribs and rows of sharp tubercles or spine-like outgrowths along the outer whorls, serving as critical index fossils for dating geological strata of that period.
• Ammonites — The plural form of amonit; an extensive group of fossil marine cephalopod mollusks characterized by chambered spiraled shells, similar to the modern nautilus. In historical geology, these representatives serve as essential index fossils for delineating and dating sedimentary biozones of past eras, providing clues about prehistoric ocean climate and dynamics.
• Anisian — A geological stage or substage located at the base of the Middle Triassic epoch, chronologically spanning from approximately 247 to 242 million years ago. As an adjective, the term refers to rocks, sediments, or fossils formed during this time interval, internationally defined by the appearance of specific ammonite and conodont assemblages within reference Alpine geological sections.