Order RODENTIA--rodents I. Characteristics - tamuk.edu

Order RODENTIA--rodents
I. Characteristics

1. 1/1 ever-growing, curved incisors with beveled tips and enamel on anterior surface only
2. no canines and a large diastema between the incisors and the cheekteeth (Figure 13-2)
3. Specialized zygomasseteric structure (Figs. 13-2, 13-3, 13-5)

A. Protrogomorphous
B. Sciuromorphous
C. Myomorphous
D. Hystricomorphous

4. Two types of lower jaw angle (Figure 13-4)
A. Sciurognathous
B. Hystricognathous

II. Families
1. Family Aplodontidae--Sewellel or mountain beaver (Figs. 13-6, -7, - 8)
A. protogomorphous, sciurognathous
B. dental formula 1/1,0/0,2/1,3/3
C. cheek teeth evergrowing, with a simple pattern
D. flattened, triangular skull shape; flask-shaped auditory bullae
E. stocky body; limbs short, no external tail

2. Family Sciuridae--tree squirrels, ground squirrels (marmots, prairie dogs), "flying" squirrels
A. sciuromorphous, sciurognathous
B. dental formula 1/1,0/0,1-2/1,3/3
C. cheek teeth rooted, with prominent cusps or ridges
D. supraorbital (incomplete postorbital) process large
E. tail generally long and bushy except in most ground squirrels

3. Family Castoridae--beaver (Figure 13-12, -13)
A. sciuromorphous, sciurognathous
B. dental formula 1/1,0/0,1/1,3/3
C. cheek teeth hypsodont, with prominent ridges; more or less parallel rows
D. tail large, broad and flat
E. hind feet webbed
F. large bodied
G. long guard hairs overly a fine, dense underfur.

4. Family Geomyidae--pocket gophers
A. sciuromorphous, sciurognathous
B. infraorbital foramen on rostrum, small,
visible in lateral view
C. zygomatic arch robust
D. dental formula 1/1,0/0,1/1,3/3
E. external, furred cheek pouches
F. eyes and pinnae very small
G. forefoot with powerful claws
H. thickset body
I. tail short

5. Family Heteromyidae--pocket mice, Kangaroo rats (Figs. 13-16, -17)
A. sciuromorphous, sciurognathous
B. infraorbital foramen relatively large, pierces the rostrum, visible in lateral view
C. dental formula 1/1,0/0,1/1,3/3
D. external, furred cheek pouches
E. pinnae evident
F. infraorbital foramen small, on rostrum.

6. Family Dipodidae--jumping mice, jerboas
A. hystricomorphous, sciurognathous
B. dental formula 1/1, 0/0, 1-0/0, 3/3
C. jumping mice are small, have a long tail, and long hind limbs

Superfamily Muridoidea--rats and mice
(including murids and cricetids)
A. myomorphous, sciurognathous
B. dental formula 1/1, 0/0, 0/0, 3/3
7. Family Muridae--: Old World rats and mice [Figs. 13-28 to -32]

A. occlusal pattern of cheek teeth forms chevrons by connecting three transverse cusps.

8. Family Cricetidae
9. Subfamily Sigmodontinae: New World rats and
mice
a. anterior cheek tooth with, at most, two pairs
of cusps opposite each other; pairs may be
united to form lophs.

10. Subfamily Arvicolinae [Microtinae]: voles,
lemmings, and muskrats
a. complex occlusal pattern of cheek teeth of
acute triangles; teeth are rootless
b. frequently with compact body and short tail
c. muskrats have a long, laterally compressed
tail and partially-webbed hind feet.

HYSTRICOMORPHA
11. Family Pedetidae--springhaas

A. hystricomorphous, sciurognathous [Fig.13-34]
B. dental formula 1/1,0/0,1/1,3/3
C. cheekteeth are evergrowing with a simplified crown pattern

12. Family Erethizontidae--American porcupines [Fig. 13-42]
A. hystricomorphous, hysticognathous, but with angular process deflected internally
B. dental formula 1/1,0/0,1/1,3/3
C. pelage conspicuously spiny, with barbs
D. Tubercles on pads of manus to increase traction
E. paroccipital process short, never extending below bulla

13. Family Myocastoridae--nutria
A. hystricomorphous, hysticognathous
B. dental formula 1/1,0/0,1/1,3/3
C. hind feet webbed
D. tail round and scaly
E. paroccipital process long

14. Family Cuniculidae--pacas
A. hystricomorphous, hysticognathous
B. dental formula 1/1,0/0,1/1,3/3
C. large rugose cheek plate, outer surface of zygomatic
arch pitted; inner surface with deep depression.

15. Family Chinchillidae--chinchillas
A. hystricomorphous
B. angular process delicate and not strongly
hysticognathous
C. auditory canal oriented vertically and with
accessory foramina at base
D. dental formula 1/1,0/0,1/1,3/3
E. cheekteeth evergrowing, pattern of lamellar plates

Order LAGOMORPHA-rabbits, hares, pikas
Characters

A. 2/1 incisors (Fig. 13-53)
B. fenestrated maxilla
C. scrotum anterior to penis (as in marsupials)
D. soles of feet entirely furred
E. hypsodont cheek teeth

FAMILIES
1. Family Ochotonidae--pikas (figs. 13-56, 13-57)

A. pinna short, no tail, short limbs
B. maxilla with one large fenestra
C. no supraorbital process

2. Family Leporidae--rabbits and hares (Fig. 13-58)
A. pinna long, pointed, tail distinct, hindlimbs long
B. highly fenestrated (lattice-like perforations) maxilla (fig 17.2); squamosals and parietals weakly
fenestrated
C. supaorbital process present
What is the dental formula of leporids?