308 Evolution? The Fossils Say YES!
had little or no fossil record but had all this anatomical data in the soft tissues and skeletons
of the living members of the group. In many cases, these living groups with limited fossil
records had not entered into the analysis, because paleontologists were only concerned with
“connecting the dots” between the teeth that were actually preserved in their local basin.
By the late 1970s and early 1980s, mammalian paleontologists had been studying speci-
mens and collecting reams of anatomical data on every system in living mammals, as well
as the important information about the skeletons of fossil mammals. Malcolm McKenna,
Mike Novacek, and Andy Wyss published some of the first cladograms that covered all the
placental mammals, while I collaborated with Earl Manning on the first cladogram (origi-
nally prepared by him in 1977) that covered all the hoofed mammals, or ungulates. All of
these cladograms were published in the mid-1980s (Novacek and Wyss 1986; Novacek et al.
1988; Novacek 1992, 1994; Prothero et al. 1986, 1988), especially in the landmark volume on
amniote relationships from a 1986 London symposium (Benton 1988a, 1988b), and in a later
volume based on a 1990 American Museum symposium on mammalian interrelationships
(Szalay et al. 1993).
By the mid-1990s, almost all these cladograms on mammalian relationships seemed
to converge on a common topology, with some minor unresolved differences of opinion
(fig. 13.12). Some things, however, were very clear and were based on multiple well-supported,
well-corroborated analyses. As McKenna had predicted in 1975, the most primitive group
of placentals is not the insectivorous mammals (as paleontologists had long thought), but
the xenarthrans (sloths, armadillos, anteaters, and their relatives). The rodents and rab-
bits are closely related after all (most paleontologists thought they were convergent) and
formed a natural group called the Glires (pronounced “GLY-reez”). The closest relatives of
primates were the tree shrews (no surprise to anthropologists here) and also the colugos
(a bizarre Asian species incorrectly referred to as “flying lemurs,” even though they are
not lemurs and they glide but do not fly). These groups together were called the Archonta.
Carnivorous mammals formed their own clade, as did the true insectivores (shrews, moles,
and hedgehogs). Finally, the hoofed mammals (subject of the next chapter) also formed
a distinct well-supported clade, the Ungulata. Together, these groups seemed to cut the
Gordian knot of mammalian interrelationships that had puzzled the great minds of pale-
ontology for decades.
But science is never this simple. Once we seemed to have achieved consensus, another
source of information had to be considered: molecular data. In the 1980s and early 1990s, all
we had were a few protein sequences for a few examples of each order, and most of the data
seemed to be consistent with the topology that the anatomical cladograms were producing.
But by the late 1990s, molecular biologists were sequencing the mitochondrial and nuclear
DNA of mammals directly, and some of their results are still not consistent with what the
anatomy and fossil record seems to indicate (Springer and Kirsch 1993; Stanhope et al. 1993,
1996; Madsen et al. 2001; Springer et al. 2004, 2005; Murphy et al. 2001a, 2001b). For example,
tenrecs don’t seem to be related to other insectivores, elephant shrews don’t cluster with
Glires nor do elephants, aardvarks, and hyraxes cluster with Ungulata. Instead, they are
united (along with some other insectivorous African groups) in a molecular clade known as
Afrotheria, and their branch point is even more ancient than that of the xenarthrans. Ungu-
lates (excluding elephants and their relatives) still clustered together, but with carnivores
as their sister group, followed by the bats, and then the insectivores, forming a clade the
molecular biologists call Laurasiatheria. Rodents and rabbits still cluster as the Glires, with