Brasilitherium, Chaoyangodens, Akidolestes and Kuehneotherium

Chaoyangodens lii (Hou and Meng 2014; early Cretaceous, 120mya) was considered a eutriconodont mammal with a reduced post-canine tooth formula and four incisors. The fifth tooth is a tiny canine. Here this specimen nests in the monotreme clade with Brasilitherium. The teeth are large for the skull. The scapula is perforated. The pelvis is unfused and simple.

Brasilitherium riograndensis (Bonaparte et al., 2003; Early Norian, Late Triassic, 208 mya) was considered a stem mammal, but here nests at the base of the monotreme mammals despite the not-quite mammalian jaw joint. This may explain why monotreme ear bones are below and medial to the jawline, but in other mammals they are posterior to the jaw joint. The long rostrum includes as many as seven premolars and 4 molars.

Bonaparte JF, Martinelli AG, Schultz CL and Rubert R 2003. The sister group of mammals: small cynodonts from the Late Triassic of Southern Brazil. Revista Brasileira de Paleontologia 5:5-27.

Kermack Dm, Kermack KA, Mussett F 1968. The Welsh pantothere Kuehneotherium praecursoris. Journal of the Linnean Society of London, Zoology. 47 (312): 407–423.

Li G and Luo Z-X. 2006. A Cretaceous symmetrodont therian with some monotreme-like postcranial features. Nature, 439:195–200.

Luo Z-X, Ji Q, Wible JR and Yuan C-X 2003. An Early Cretaceous tribosphenic mammal and metatherian evolution. Science 302:1934–1939.

Patterson B and Olson EC 1961. A triconodont mammal from the Triassic of Yunnan. In Vandebroek G (ed.), International Colloquium on the Evolution of Lower and Non Specialized Mammals. Koninklijke Vlaamse Academir voor Wetenschappen, Letteren en Schone Kunsten can Belgie 129-191.

Shaw G 1799. The Naturalist's Miscellany.

wiki/Chaoyangodens
wiki/Kuehneotherium

Mammalia

Chaoyangodens

Marsupiala - Metatheria

Eomaia and kin

Monodelphis and kin