[see papers in reader by Lillegraven and Hayssen et al.]
[in addition to paper by Novacek from your reader, the following are good statements of relationships among extant and extinct eutherian orders]:
6. Szalay, F.S., M.J. Novacek, and M.C. McKenna (eds.). 1993. Mammal
Phylogeny. Placentals. Springer-Verlag, New York.
|In the accompanying figures, we have represented hypothesized
phylogenetic relationships among the orders of extant eutherian (or "placental")
mammals, based on the classifications of Simpson (1945) and McKenna and
Bell (1997). We also provide a hypothesized phylogeny of living orders
based on a consensus of molecular data published recently in the journal
Systematic Biology (volume 48, number 1, March 1999).
|Simpson (1945) - remember that Simpson's
classification is Linnean-based and reflects both ancestor-descent relationships
and shifts in way of life (change of adaptive zone). He also believed,
in part based on the available fossil record at the time of his work, that
modern eutherian mammals radiated explosively following the dinosaur extinction
at the Cretaceous-Paleocene (K-T) boundary about 65 million years ago.
|McKenna and Bell (1997) - their classification
is a node-based one, wherein the phylogeny can be read directly from the
classification itself. In theory, all nodes in the tree should be
resolved into dichotomous branches but, in reality, some nodes remain polytomies
because hierarchical relationships have not as yet become established.
Only Magnorder and Grandorder levels in their classification are given,
and the ordinal names used are those that largely follow Simpson because
of the familiarity of these names.
|The consensus molecular tree is "the best estimate
of placental relationships based on our own extensive analyses of published
and unpublished data" (Waddell et al., 1999, Syst. Biol. 48:1-5). There
are three major branches in this molecular-based hypothesis, as follows:
 An unnamed clade that consists of the Glires [Rodentia and Lagomorphs]
and the typical archontan orders exclusive of the bats [tree shrews (Scandentia),
and colugos (Dermoptera) plus primates (Primates)]. The archantan clade
is termed Euarchonta to reflect the exclusion of the bats, and dermopterans
and primates are collectively named the Primatomorpha to reflect their
 The Laurasiatheria (so named because of the largely northern hemisphere origin and distribution) is a fully resolved clade with "true" lipotyphlans (Eulipotyphyla: shrews [Soricidae], moles [Talpidae], and hedgehogs [Erinaceidae]) on the first branch, followed by bats (Chiroptera), then the combination of cetaceans and artiodactyls (Cetartiodactyla) reflecting the molecular linkage of whales and hippos, then the odd-toed ungulates (Perissodactyla), and finally the pangolins (Pholidota) and carnivorans (Carnivora, including the Pinnipedia).