Concise hierarchy

(Kingdom) Animalia - (Phylum) Chordata

Phylogeny

Crown clade

Ref: T. Rowe, 1988: 247. [inferred]

First representative

†Obdurodon insignis Woodburne & Tedford, 1975

Ref: M.A. O'Leary et al., 2013: table S2 (p. 85).

Defined by the most recent common ancestor (and all its descendants) of

Ornithorhynchidae (Family) Gray, 1825		Ref: T. Rowe, 1988: 247.
Tachyglossidae (Family) Gill, 1872		Ref: T. Rowe, 1988: 247.

Included, by definition, in node-based clade

Mammalia (Clade) Linnaeus 1758 [Rowe 1988], nom. cl. inval.

Ref: T. Rowe, 1988: 247.

Excluded, by definition, from branch-based clade

Theriimorpha (Clade) Rowe 1993

Ref: T. Rowe, 1993: 139 ("monotremes").

Node-based clade

Monotremata (Clade) Bonaparte 1837 [Rowe 1988]

Ref: M.A. O'Leary et al., 2004: 491.

Current position

Prototheria (Clade) Gill 1872 [O'Leary, Allard, Novacek, Meng & Gatesy 2004]

Ref: M.A. O'Leary et al., 2004: fig. 28.2.

Alternative positions

Mammalia (Clade) Linnaeus 1758 [Rowe 1988], nom. cl. inval.

Ref: T. Rowe, 1988: 247.

Historical positions

Prototheria (Clade) Gill 1872 [O'Leary, Allard, Novacek, Meng & Gatesy 2004]	Ref: M.A. O'Leary et al., 2013: table S4 (p. 100).
Prototheria (Clade) Gill 1872 [O'Leary, Allard, Novacek, Meng & Gatesy 2004]	Ref: M.A. O'Leary et al., 2004: fig. 28.2.
Mammalia (Clade) Linnaeus 1758 [Rowe 1988], nom. cl. inval.	Ref: T. Rowe, 1988: 247, figs. 3, 4.