1. Lecture 18. Rodents 1

2. Carleton & Musser, 2005, p. 751 Carleton & Musser, 2005, p. 751
"We retain Brandt’s (1855) names for three of the five suborders (Sciuromorpha, Myomorpha, and Hystricomorpha), whereas some foremost rodent authorities have pointedly advised against continued employment of these Brantian epithets, especially at the subordinal rank (e.g., Landry, 1999:283; Wood, 1985). They have argued that the descriptive meaning of the terms does not strictly concord with the morphologies of included members, and that this contradiction will only continue to engender confusion. That the logical connotation of a taxon’s name should uniformly correspond to its taxonomic intention strikes us as puzzling. Not all members of the Superorder Afrotheria live in Africa, nor are all species of the Order Carnivora carnivorous. The species- to family-group ranks are rife with valid names whose logical meaning, as intended by the original descriptor, is partially inconsistent or actually misleading in terms of the currently accepted contents of the taxon, whether in strict morphological accuracy, indication of distribution, or implication of phylogenetic alliance. In reviewing 150 years of rodent classifications, we are impressed that few of our predecessors applied the features of infraorbital configuration and jaw shape in an overridingly typological touchstone of all rodent classification. Most made the distinction between, e.g., Myomorpha in its taxic sense and myomorphy as a morphological condition and routinely consulted additional traits. Thus, the hystricomorphous Dipodidae have been nearly always included within Myomorpha (in retrospect, correctly it would seem), and the sciuromorphous Geomyoidea have been considered by many to also fit within Myomorpha (in retrospect, perhaps incorrectly). And while Brandt’s taxonomic names qua morphological descriptors may not perfectly correspond to all members, they nonetheless do conform very well. The core family members of Sciuromorpha, Myomorpha, and Hystricomorpha have remained largely the same, and most, not all, do exhibit those fundamental zygomasseteric structures. More importantly, these core assemblages have survived recent scrutiny using ever more explicit principles for systematic classification and sophisticated methods for inferring phylogenetic relationship and assessing descent from a common ancestor."
Carleton & Musser, 2005, p. 751
Carleton & Musser, 2005, p. 751

3. Rodentia Sub-orders (Mammal Species of the World, 3rd ed., 2005)
Lecture 18. Rodents 1
Rodentia Sub-orders (Mammal Species of the World, 3rd ed., 2005)
Sub-order
Masseteric condition
Mandibular condition
Number of families / species
Sciuromorpha
protogomorphous (Aplodontidae), sciuromorphous (Sciuridae), “pseudo-myomorphous” (Gliridae)
sciurognathous
3 / 307
Castorimorpha
sciuromorphous
3 / 102
Myomorpha
myomorphous
(except Dipodidae, hystricomorphous)
7 / 1569
Anomaluromorpha
hystricomorphous
2 / 9
Hystricomorpha
sciurognathous (only Ctenodactylidae)
hystricognathous (rest)
18 / 290
The distribution of these two important characters, the masseteric and the lower jaw condition, among the major groups of rodents is hsown in this table, Our current understading of their phyloeny indicates that the different morphologies evolved more than once, or that were lost in some groups.
DIPODIDAE IS HYSTRICOMORPHOUS, BUT PHYLGENETICALLY/TAXONOMICALLY IN MYOMORPHA. SEE P. 751 OF MSW3. SEE ALSO MARCELO’S FROM NOV THERE MAY BE OTHER EXCEPTIONS.

4. Aplodontidae Monotypic (1 species) Restricted to NW US
“Primitive” rodent
Protrogomorphous-Sciurognathous

5. Sciuridae 50 genera, 273 species
Worldwide except Australia and southern South America
Wide range of ecolomorphs
Although Hayssen 2008 (J. Mammalogy) breaks squirrel morphology into 4 or so types. Should use!

6. Squirrel body plans (N. American examples)
Ground
Tree
Flying
Tamias
Spermophilus
Marmota
Sciurus
Tamiasciurus
Glaucomys

7. Tamias minimus
Least Chipmunk

8. Castoridae 1 genus, 2 species Holarctic Semi-aquatic
Specialize on cambium

10. Muridae >250 genera, >1300 species
Mice, rats, voles, hamsters, gerbils

11. Muridae: Subfamilies Murinae Old World mice & rats Cricetidae! voles
Sigmodontinae New World mice & rats
Gerbillinae gerbils
Spalacinae blind mole-rats
+ 12 others!!!
Alaska

12. Anomaluridae Scaly-tailed squirrels 3 genera, 7 species
Western-central Africa

13. Suborder: Hystricomorpha Africa AKA “Phiomorpha”
Bathyergidae mole rats
Hystricidae Old World porcupines
Petromuridae rock rats, dassie rats
Thryonomyidae cane rats

14. Suborder: Hystricomorpha South America AKA “Caviomorpha”
Erethizontidae
Chinchillidae
Dinomyidae
Caviidae
Hydrochaeridae
Dasyproctidae
Agoutidae
Ctenomyidae
Octodontidae
Abrocomidae
Echimyidae
Capromyidae
Myocastoridae

15. Erethizontidae New World porcupines 4 genera, 12 species
Lowland tropics to montane forests, deserts, coniferous forests
Herbivores