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Their definition of Mammalia is roughly equal to the Mammaliaformes as defined by McKenna and Bell (1997) and other authors. They also define their taxonomic levels as clades and do not apply Linnean hierarchies. Mammalia †Sinoconodon - earliest and most basal of mammals; Unnamed clade 1 - a clade that contains all other mammals.
Amborella trichopoda, the most basal extant angiosperm. The flowering plant family Amborellaceae, restricted to New Caledonia in the southwestern Pacific, [n 9] is a basal clade of extant angiosperms, [13] consisting of the most species, genus, family and order within the group that are sister to all other angiosperms (out of a total of about 250,000 angiosperm species).
Cladotheria is a clade (sometimes ranked as a legion) [2] of mammals. It contains modern therian mammals (marsupials and placentals) and several extinct groups, such as the "dryolestoids", amphitheriids and peramurids. The clade was named in 1975 by Malcolm McKenna.
One study based on DNA analysis suggests that Scandentia and Primates are sister clades, but does not discuss the position of Dermoptera. [9] Although it is known that Scandentia is one of the most basal Euarchontoglires clades, the exact phylogenetic position is not yet considered resolved, and it may be a sister of Glires, Primatomorpha or Dermoptera or to all other Euarchontoglires.
An evolutionary tree of mammals. [3] Modern mammals (class Mammalia) are divided into Monotremes, Marsupials, and Placentals. The subclass Prototheria (Monotremes) comprises the five species of egg-laying mammals: platypus and four echidna species. The infraclasses Metatheria (Marsupials) and Eutheria (Placentals) together form the subclass Theria.
Figure 1:In mammals, the quadrate and articular bones are small and part of the middle ear; the lower jaw consists only of dentary bone.. While living mammal species can be identified by the presence of milk-producing mammary glands in the females, other features are required when classifying fossils, because mammary glands and other soft-tissue features are not visible in fossils.
Eutheria (from Greek εὐ-, eú-'good, right' and θηρίον, thēríon 'beast'; lit. ' true beasts '), also called Pan-Placentalia, is the clade consisting of placentals and all therian mammals that are more closely related to placentals than to marsupials.
Definition of an evolutionary grade [ edit ] An evolutionary grade is a group of species united by morphological or physiological traits, that has given rise to another group that has major differences from the ancestral group's condition, and is thus not considered part of the ancestral group, while still having enough similarities that we can ...