Total group (also total clade, stem clade, or panstem clade) is a term used in systematics to refer to a crown clade plus its stem group. It thus refers to all organisms sharing more recent ancestry with a group of living organism (extant members of the crown clade) than with any other living organisms. Basal members of total groups show few distinguishing features from related groups, and may thus be hard to assign to the total group. More derived members, however, show increasing numbers of synapomorphies of the crown group. Biological systematics is the study of the diversity of life on the planet earth, both past and present, and the relationships among living things through time. ... A crown group is a living monophyletic group or clade, consisting of the last common ancestor of all living examples, plus all of its descendants. ... A clade is a term belonging to the discipline of cladistics. ... In palaeontology, a stem group is a systematic grouping that is required to accommodate fossils in the classification of organisms. ... This article or section does not cite its references or sources. ... Extant means still existing. It is the opposite of extinct, and can be applied to species, cultures and works of culture (e. ... Shared characteristics that define a cladistic grouping. ... A crown group is a living monophyletic group or clade, consisting of the last common ancestor of all living examples, plus all of its descendants. ...

Terminology

When referring to a systematic grouping, there is a danger of confusion between the crown and total groups, although they mean different things. For example, simply referring to a fossil as a "bird" does not tell you whether it is a familiar example derived from the last common ancestor of all living forms, or whether it is a more basal form. (By definition, all living forms fall into the crown group.)

Since all total groups correspond to a crown group, some systematists have suggested using a standardized prefix (e.g., Pan-) to form names of total clades from the names of their corresponding crown clades. For example, Panmammalia (or Pan-Mammalia or pan-Mammalia) would be the total clade including Mammalia but no living non-mammals. Others have pointed out that there are already names for many total clades; for example, Synapsida and Theropsida have both been used to refer to the total mammalian clade. Biological systematics is the study of the diversity of life on the planet earth, both past and present, and the relationships among living things through time. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... Groups Caseasauria Eupelycosauria    Sphenacodontia       Therapsida          (...mammals) Synapsids (fused arch), formerly known as mammal-like reptiles, are a group of amniotes (reptiles and all their ancestors) that developed one hole in their skull (temporal fenestra) behind each eye, about 320 million years ago (Ma) during the late Carboniferous. ... Orders & Suborders Order Pelycosauria * Suborder Caseasauria Suborder Eupelycosauria * Order Therapsida * Suborder Biarmosuchia Suborder Dinocephalia Suborder Anomodontia Suborder Gorgonopsia Suborder Therocephalia Suborder Cynodontia * For complete phylogeny, see text. ... A clade is a term belonging to the discipline of cladistics. ...