Asaphus expansusAsaphus expansus (/ˈæsæfʌs ɛkspænsʌs/) is the type species of the asaphid trilobite genus Asaphus. It was previously classified as Entomostracites expansus before being split off into its own genus.Cephalon (arthropod head)The cephalon is the head section of an arthropod. It is a tagma, i.e., a specialized grouping of arthropod segments. The word cephalon derives from the Greek κεφαλή (kephalē), meaning "head".
PygidiumThe pygidium (pl.: pygidia) is the posterior body part or shield of crustaceans and some other arthropods, such as insects and the extinct trilobites. In groups other than insects, it contains the anus and, in females, the ovipositor. It is composed of fused body segments, sometimes with a tail, and separated from thoracic segments by an articulation.
Hypostome (trilobite)The hypostome is a plate covering the mouth on the underside of the head in some arthropods, notably including trilobites. In trilobites, The hypostome can be classified into three types based on whether they are permanently attached to the rostrum or not and whether they are aligned to the anterior dorsal tip of the glabella.
TrilobiteClass of extinct, Paleozoic arthropodsTrilobites (; meaning "three-lobed entities") are extinctmarinearthropods that form the classTrilobita. One of the earliest groups of arthropods to appear in the fossil record, trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described.
Holochroal eyeHolochroal eyes are compound eyes with many tiny lenses (sometimes more than 15,000, each 30-100μm, rarely larger). They are the oldest and most common type of trilobite eye, and found in all orders of trilobite from the Cambrian to the Permian periods. Lenses (composed of calcite) covered a curved, kidney-shaped visual surface in a hexagonal close packing system, with a single corneal membrane covering all lenses.
Anatomical terms of locationStandard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and axes.
Type (biology)In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to anchor or centralizes the defining features of that particular taxon. In older usage (pre-1900 in botany), a type was a taxon rather than a specimen.
Synonym (taxonomy)In biological taxonomy, a synonym is one of two or more scientific names that apply to the same taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. In botanical nomenclature, a synonym is a scientific name that applies to a taxon that now goes by a different scientific name.
ThoraxThe thorax (pl.: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the body, each in turn composed of multiple segments. The human thorax includes the thoracic cavity and the thoracic wall.
OrdovicianThe Ordovician ( or-də-VISH-ee-ən, -doh-, -VISH-ən) is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 43.75 million years from the end of the Cambrian Period 486.85 Ma (million years ago) to the start of the Silurian Period 443.1 Ma.BasilicusBasilicus (Ancient Greek: Βασιλικός) was a rhetorician and sophist of Nicomedeia. Many scholars believe he was one of the teachers of Apsines of Gadara, therefore he must have lived about 200 CE.*As an Amazon Associate I earn from qualifying purchases.