#paleontology

• Anthropolit — A fossilized human remain or a human body petrified through incrustation with mineral substances (lime, silica) inside cave sediments or ancient geological layers. This rare technical term is used in fossil studies to denote prehistoric skeletal specimens that have undergone a complete process of diagenesis and structural mineralization.
• Anthropopithecus — An archaic or historical scientific name given to a hypothetical genus of transitional fossil primates, considered linking bridges between higher apes and humans; ape-man. In the 19th century, the term was used by paleontologists to classify fossils presenting a structural mixture of simian and hominid traits, prior to the establishment of modern Homo and Australopithecus taxonomies.
• Apatosaurus — A genus of gigantic sauropod dinosaur, a herbivore that lived during the Late Jurassic period in what is now North America. This remarkable prehistoric animal was characterized by an extremely long neck, a long whip-like tail used for defense, and massive pillar-like limbs that supported a structural weight of dozens of tons, historically known also under the popular name of brontosaurus.
• Arietites — A fossil genus of ammonites (extinct marine cephalopod mollusks) from the Early Jurassic period, characterized by a large, planospiral shell with prominent transverse ribs and a distinct central keel; the name suggests the resemblance of the coiled shell to the horns of the Egyptian god Ammon or a ram, serving as a critical index fossil for dating geological strata of the Sinemurian stage.
• Aristogenesis — An idealistic evolutionary theory, formulated by paleontologist Henry Fairfield Osborn, stating that the evolution of living organisms is determined by the gradual emergence of new, superior adaptive genes and characters directly from the internal potential of the germ plasm, independent of natural selection or the direct influence of the environment. In modern biology, the term is considered historical, describing a predetermined biological improvement mechanism.
• Artinskian — An age or stage in the Cisuralian epoch of the Permian period, geochronologically dated between approximately 290 and 283 million years ago; relating to this stage. In theoretical geology, the term describes an era marked by major climate shifts and massive marine sediment depositions, originally defined in the Ural Mountains region of Russia.
• Aspidoceras — An extinct genus of ammonites (coiled marine cephalopod mollusks) in the family Aspidoceratidae, which lived during the Late Jurassic and Early Cretaceous periods. Fossils of this genus are recognized by their robust, evolute shell, characterized by distinctive rows of nodes or spines arranged on the flanks, used by paleontologists as index fossils for dating marine geological strata.
• Astaco- — A scientific combining form (prefixoid) extracted from the Greek language (from 'astakos'), used in rare scientific, zoological, and paleontological terminology to refer to crayfish, decapod crustaceans of the Astacidae family, or to describe anatomical and fossil structures belonging to or closely related to this group of aquatic organisms.
• Astacoid — Resembling a crayfish or the species of the Astacus genus in form, structure, or general appearance; a morphological adjective used to describe fossil specimens, crustacean larvae, or external anatomical characters (such as the carapace or claws) reminiscent of the river crayfish's structural configuration.
• Fossilized crayfish — The fossilized remnant, petrified imprint, or petrographic cast of a prehistoric crayfish or a part of the exoskeleton of a decapod crustacean from the Astacidae family; these structural fossil formations are used in stratigraphical geology as biofacial indicators for reconstructing ancient freshwater aquatic environments.
• Aulacoceras — An extinct genus of dibranchiate cephalopods from the order Belemnoidea, characteristic of the Triassic period. This ancient marine organism was notable for an elongated, conical, calcareous internal shell marked on its outer surface by prominent longitudinal grooves.
• Autunian — A transitional geological stage located at the base of the Lower Permian (or late Upper Carboniferous), defined by successions of oil shales rich in fossil flora (Callipteris conferta) historically researched in the basin of Autun, France; as an adjective, it refers to the formations, rocks, or fauna specific to this time interval.
• Auversian — A regional subdivision or transitional geological stage of the Middle Eocene within the Paleogene period, defined by the fossiliferous sand deposits researched in Auvers-sur-Oise, Paris Basin (France); as an adjective, it denotes the sedimentary formations or marine fauna characteristic of this epoch.