Suborder Hystricomorpha

Suborder Hystricomorpha:

1) Angular process of jaw not in same plane as most of dentary

(hystricognathous; “gnath” = “jaw”)

2) Coronoid process more reduced than in sciurognaths

3) Often has prominent shelf projecting outwards from near base

of last molar

4) Hystricomorphous musculature means medial masseter

muscle passes through often enlarged infraorbital foramen

5) 18 families! Mostly African, South American, Caribbean, now

in tropical N Am, some in SE Asia (but you only need to know

9)

Family Bathyergidae (African mole rats)

• 6 genera, 17 species

• Sub-Saharan Africa

• Small, fossorial; reduced eyes and

external ears, loose skin, robust skull

• Dig using mostly incisors; incisors

procumbent, protrude from mouth even

when mouth is closed, roots extend

behind molars; cheek teeth are ring or

8-shaped

• Herbivorous, eat primarily underground

storage organs of plants; elaborate

burrows systems, some solitary, some

eusocial

Bathyergus

Heterocephalus

Family Hystricidae (Old World porcupines)


• Africa, Italy, southern and SE Asia

• Large (up to 27 kg), plantigrade,

terrestrial; covered in spines (which lack

barbs), inflated rostrum in some African

species

• Nocturnal, herbivorous, dig burrows

• Give birth once a year in an

underground chamber, young born fully

developed, but with soft spines which

harden after a couple of hours

Brush-tailed porcupine;

Atherurus

Crested porcupine; Hystrix

Family Erethizontidae (New World porcupines)


• Forests in N. America & northern S.

America

• Large (900 g-16 kg), terrestrial and

arboreal; covered in spines (with barbs)

mixed with hairs

• Herbivorous (esp. cambium in winter),

nocturnal, solitarily or in pairs (will share

winter dens) Coendou

Erethizon

Family Chinchillidae (chinchillas & viscachas)

• Southern S. America, high country of

Peru and Bolivia, through Argentina

• Medium to large (500 g-8 kg), 4 toes on

front feet, 3-4 on hind feet; dense fur;

long, well-furred tails

• Burrows & rock crevices; good jumpers;

Lagostomus highly cursorial

• Very vocal, vocalizations used in social

interactions, live in colonies;

herbivorous; diurnal

• Breed year round, usually twins, young

born fully furred with eyes open

• Hunted & farmed for fur

Mountain

viscacha;

Lagidium

Plains

viscacha

Chinchilla

Lagostomus

Family Caviidae (capybaras, maras, & guinea pigs)


• S. America in diverse habitats

• 400 g-79 kg, even larger forms (200 kg giant

capybara) existed during the Pliocene

• Diurnal, nocturnal, or crepuscular (varies by

species), herbivorous, rows of cheek teeth

converge anteriorly

• Mating & social systems vary: maras can be

monogomous, but most cavies are

promiscuous or live in groups dominated by a

top male

Capybara

Mara;

Dolichotis

Cavy; Cavia

Hydrochoerus

Family Dasyproctidae (agoutis & acouchis)


• Southern Mexico through the Amazon Basin,

mostly in tropical forest

• Up to 2 kg; digitigrade, slim legs, many

cursorial adaptations; toes are thick & hoof-

like, short tail

• Premaxillae & nasals extend past thin

incisors

• Herbivorous, scatterhoard fruits and nuts;

important seed dispersers

• Largely diurnal; solitary, but will group

around food resources

• Young born fully developed

• Fast runners & good swimmers Acouchi;

Myoprocta

Agouti

Agouti

Dasyprocta

Family Cuniculidae (Pacas)

Paca; Cuniculus

• 1 genus, 2 species

• Central Mexico to southern Brazil in

tropical forests along streams, rivers

• Up to 12 kg; nearly tailless; conspicuous

white stripes and spots; short legs and

blunt heads

• 4 digits on front feet, 5 on hind feet

(most others we discussed so far have 3

toes on hind)

• Resonating chambers formed by

maxillaries and greatly broadened

zygomatic arches

• Herbivorous, including fruit; single

young; hunted as food

Good to eat

Family Ctenomyidae (tuco-tucos) • 1 genus, 60 species

• Sandy/loamy soils in southern 2/3 of S. America

• Up to 700 g; fringe of stiff hairs on feet (used for

moving soil); long claws, procumbent stout

incisors, small external ears and other typical

fossorial adaptations; kidney-shaped cheek teeth

(3rd molar vestigial)

• Fossorial, herbivorous (esp. underground plant

parts), usually live in “colonies” of solitary

individuals, but at least 1 species social

• Same ecological role as gophers in N. America

(but no external cheek pouches)

Ctenomys

Family Myocastoridae (nutrias)


• S. & Central America, introduced to Europe &

the U.S. in fur farms

• Up to 8 kg; webbed hind feet, long & bare tail;

dense underfur

• Excellent swimmers (stay under water up to 5

min), live in burrows in river banks, eat

vegetation on land & in shallow water

• Breed year round & are prolific

• Nipples are high on females sides so young

can nurse while mother is in water

• Live in groups up to 10 individuals

Nutria; Myocastor

Family Echimyidae (spiny rats)


• Tropical regions of S. & Central America

(also West Indies until 1880s)

• Long tail which can break off (but

doesn’t regenerate), bristly hairs on back

& rump of most

• Nocturnal, can be fossorial, terrestrial, or

arboreal, most species are solitary

Family Capromyidae (hutias)

• Of 8 genera and 20 species, at least 8

species recently extinct

• Found in West Indies, most diverse in

Cuba

• Up to 7 kg, plantigrade, 5 toes on

each foot with strong curved claws

• Tail varies- vestigial to prehensile

• Mostly terrestrial, but some are

partially arboreal, nest in trees & rock

crevices

• Primarily herbivorous, but will eat

insects & even lizards

Order Lagomorpha

(rabbits, hares, & pikas)

• Unlike rodents, males have no baculum

• Like marsupials, testes are in front of penis

• Born with 3 pairs of upper incisors (evergrowing), but lose outer

pair with age

• 2nd pair of incisors found behind first pair & lack sharp edge

• Form 2 types of fecal pellets- 1 is re-ingested to extract nutrition


• Holarctic: N. America, eastern Europe, &

northern Asia

• N Am: rocky outcrops and talus; Eurasia:

variety of habitats, including steppe or

plains as well as rocky outcroppings

• 100-150 g; stocky bodies, short, round

ears; short limbs; hairy soles of feet; no

external tail; males lack scrotum

• Diurnal, herbivorous; steppe-dwelling pikas

prolific breeders like rabbits, but N Am

talus-dwellers only 1 litter per year

• Lay out vegetation to dry & store for use as

food & bedding in winter

• Social systems vary- solitary to large

colonies, communicate with loud whistles

Family Ochotonidae (pikas)

Ochotona

Family Leporidae (rabbits & hares)


• Found worldwide, but introduced in S.

America, Australia, New Zealand, Indonesia,

& Madagascar

• 300 g-5 kg (females larger than males);

elongated hind legs, short tail, ears longer

than wide

• Rabbits dig burrows for shelters, hares

typically do not; rabbits born naked/blind,

hares born fully formed

• Variety of habitats; herbivorous

Pygmy rabbit;

Brachylagus

Jackrabbit;

Lepus Sumatran striped

rabbit; Nesolagus

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Suborder Hystricomorpha