With the addition of more taxa,
the lineage of synapsids (including mammals) is filling up nicely — and a little differently than what was once thought. In 1982 TS Kemp produced this image (Fig. 1).
is built, more or less, from past efforts. Sometimes this can be a problem when the root cladogram has unrecognized problems.
Kemp (1982) produced his family tree (Fig. 1) without the aid of phylogenetic software and prior to the discovery of several key taxa. He was building on past work by Romer and Price (1940) and others before them. The large reptile tree also builds upon early work.
Kemp TS 1982. Mammal-Like Reptiles and the Origin of Mammals. Academic Press: London. 363 pp.
Romer AS and Price LW 1940. Review of the Pelycosauria. Geological Society of America Special Papers 28: 1-538.