morpha relative to the other two groups is uncertain. Re-
cently, several molecular phylogenetic studies have ad-
vanced our knowledge of relationships among families and
genera of Old World and New World hystricognaths (Ned-
bal et al. 1994; Huchon et al. 2001; Rowe 2002; Honeycutt
et al. 2003; Ingram et al. 2004). In terms of interfamilial
relationships, the monophyly of several clades are well sup-
ported, including (fig. 2.5): (1) the Bathy-Phiomorpha and
the Thryonomyoidea; (2) Caviomorpha and the superfam-
ilies Octodontoidea (families Octodontidae, Ctenomyidae,
Echimyidae, Myocastoridae, Capromyidae, and Abrocomi-
dae), Cavioidea (Caviidae, Hydrochaeridae, Agoutidae,
and Dasyproctidae), and the Chinchilloidea (Chinchilli-
dae); (3) a well-resolved phylogeny for the Bathyergidae,
which places Heterocephalus glaberat the base of the phy-
logeny; (4) grouping of the Dinomyidae within the Chin-
chilloidea rather than the Erethizontoidea; and (5) strong
support for an association between the superfamilies Chin-
chilloidea and Octodontoidea. Problems still persist rela-
tive to the placement of the Erethizontoidea (New World
porcupines) and Hystricomorpha (Old World porcupines).
Although not shown, phylogenies of genera and species are
published for the families Octodontidae and Bathyergidae
(Honeycutt et al. 2003; Ingram et al. 2004).Rodent Evolution, Phylogenetics, and Biogeography 17Figure 2.5 Maximum likelihood tree derived from a combined analysis of two nuclear genes, exon 10 of growth
hormone receptor and intron 1 of the prealbumin transthyretin gene. Bootstrap values are indicated for nodes with
greater than 50% support, with the symbols * and ** representing 90% and 100% support, respectively. Based
on results from Rowe (2002).