Mineralized tissue in the context of "Dentin"

Marine invertebrates are invertebrate animals that live in marine habitats, and make up most of the macroscopic life in the oceans. It is a polyphyletic blanket term that contains all marine animals except the marine vertebrates, including the non-vertebrate members of the phylum Chordata such as lancelets, sea squirts and salps. As the name suggests, marine invertebrates lack any mineralized axial endoskeleton, i.e. the vertebral column, and some have evolved a rigid shell, test or exoskeleton for protection and/or locomotion, while others rely on internal fluid pressure to support their bodies. Marine invertebrates have a large variety of body plans, and have been categorized into over 30 phyla.

Biomineralization, also written biomineralisation, is the process by which living organisms produce minerals, often resulting in hardened or stiffened mineralized tissues. It is an extremely widespread phenomenon: all six taxonomic kingdoms contain members that can form minerals, and over 60 different minerals have been identified in organisms. Examples include silicates in algae and diatoms, carbonates in invertebrates, and calcium phosphates and carbonates in vertebrates. These minerals often form structural features such as sea shells and the bone in mammals and birds.

Organisms have been producing mineralized skeletons for the past 550 million years. Calcium carbonates and calcium phosphates are usually crystalline, but silica organisms (such as sponges and diatoms) are always non-crystalline minerals. Other examples include copper, iron, and gold deposits involving bacteria. Biologically formed minerals often have special uses such as magnetic sensors in magnetotactic bacteria (Fe₃O₄), gravity-sensing devices (CaCO₃, CaSO₄, BaSO₄) and iron storage and mobilization (Fe₂O₃•H₂O in the protein ferritin).

Palaeozoology or paleozoology (Greek: παλαιόν, palaeon "old" and ζῷον, zoon "animal") is the branch of paleontology and evolutionary biology that specifically deal with the study of prehistoric organisms from the kingdom Animalia and the recovery and identification of their fossil remains from geological (or even archeological) contexts. The field also extends to the use of these fossil records for reconstructive phylogeny (via comparative anatomy and phylogenetics) and paleoecology, i.e. the study of ancient natural environments and ecosystems.

While speculative fossils of earliest animals (in the form of primitive sponges such as Otavia) can trace back to the late Tonian period of the mid-Neoproterozoic era, definitive macroscopic metazoan remains are mainly found in the fossil record from the Ediacaran period onwards, although they do not become common until after the Cambrian Explosion, and vertebrate fossils do not become common until the Late Devonian period in the latter half of the Paleozoic era. Perhaps the best known macrofossils group is the dinosaurs. Other popularly known animal-derived macrofossils include trilobites, crustaceans, echinoderms, brachiopods, mollusks, bony fishes, sharks, Vertebrate teeth, and shells of numerous invertebrate groups. This is because hard organic parts, such as bones, teeth, and shells resist decay, and are the most commonly preserved and found animal fossils. Exclusively soft-bodied animals — such as jellyfish, flatworms, nematodes, and annelids — are consequently rarely fossilized, as these groups have few mineralized tissues that can survive geological processes, although trace fossils of their existence and activities can be preserved.