Lab 19-Order ARTIODACTYLA

(pigs, peccaries, hippos, camels, giraffes, deer, antelope, bison, goats, sheep)

diagnostic characters:

1. foot posture digitigrade (camels) or unguligrade

2. feet paraxonic – two principle digits present, nearly equal in size, not symmetrical in shape (axis of symmetry passes between third and fourth digits)

right front feet of a pig (Sus), hippo (Hippopotamus), elk (Cervus), and camel (Camelus)

3. two or four digits on all feet (three toes on hindfoot in peccaries)

4. femur without a third trochanter

5. calcaneus articulating with fibula

6. astragalus with pulley-like surface above and below

7. no alisphenoid canal

8. nasals usually not wide posteriorly

9. cheekteeth either bunodont (pigs, peccaries, hippos) or selenodont

bunodont teeth of a pig, Sus (left); selenodont teeth of a deer, Odocoileus (right)

Classification

Artiodactyls are the dominant group of ungulates, far overshadowing perissodactyls in taxonomic diversity and abundance. Perissodactyls appeared in the Paleocene and reached their greatest diversity in the Eocene; Artiodactyls appeared in the early Eocene, and the majority of their radiation occurred in the Miocene. Since then, perissodactyls have steadily declined, but the artiodactyls have remained diverse and ecologically highly successful. Of the 36 families present in the Cenozoic, 10 families (and about 85 genera) survive to the present. In contrast, the perissodactyls, represented by 14 Cenozoic families, are reduced today to only 3 families and some 6 genera.

Artiodactyls are generally divided into three suborders, and the most diverse families (Cervidae and Bovidae) into a number of subfamilies. One generally accepted classification is as follows:

Order Artiodactyla

Suborder Suiformes

Family Suidae -pigs

Family Tayassuidae - peccaries

Family Hippopotamidae - hippos

Suborder Tylopoda

Family Camelidae -camels, vicuña, guanaco, llama, alpaca

Suborder Ruminantia

Infraorder Tragulina

Family Tragulidae -chevrotains (mouse deer)

Infraorder Pecora

Superfamily Giraffoidea

Family Giraffidae -giraffes

Superfamily Cervoidea

Family Moschidae -musk deer

Family Cervidae -deer, elk, caribou, moose, raindeer

Family Antilocapridae - pronghorn

Superfamily Bovoidea

Family Bovidae -bison, muskox, goats, sheep, antelope, cows

note: Some recent molecular data support a phylogenetic link between cetaceans and hippos; it seems clear, however, that cetaceans and artiodactyls are at least sister groups, now united under the node Cetartiodactyla.

Suborder SUIFORMES

Includes taxa with bunodont molars, tusk-like canines, and feet usually retaining all four toes with complete and separate digits. The skull contrasts with those of other artiodactyls in having a posterior extension of the squamosal bone that meets the exoccipital bone and conceals the mastoid bone. Pigs have a non-ruminant type of stomach with as many as three chambers, but employ caecal fermentation; hippos, and possibly peccaries, have a multichambered stomach and gastric fermentation.

general characters:

1. foot posture unguligrade

2. digits 4-3 or 4-4

3. hoofs present

4. cannon bone lacking in all feet (partial fusion of metatarsals in Tayassuidae)

5. no horns or antlers

6. postorbital bar never complete

7. mastoid not exposed, obscured by broad contact of squamosal and occipital

8. one to three pairs of upper incisors present

9. canines tusk-like, sharp-edged

10. molars bunodont

11. stomach with two or three chambers

Family SUIDAE (pigs, hogs)

diagnostic characters:

1. size medium to large (110-200 cm)

2. body sparsely haired or with coarse bristles

3. digits 4-4, but usually only two functional in locomotion (side toes small)

4. snout elongate, mobile, flattened at end

5. nostrils opening anteriorly

6. no fusion of metacarpals or metatarsals

7. paroccipital process elongated

8. no ventral flange on angular process of lower jaw

9. canines usually with sharp edges; upper canines larger than lower canines, directed outward and upward

10. cheekteeth bunodont and brachydont

range: Old World, central and southern Europe, Africa (except for Sahara), Middle East through India to southern China and SE Asia, including Indonesian islands.

genera: Sus (pygmy hogs, wild boar, domestic pig, bearded pig), Babyrousa (babirusa), Potamochoerus (bushpig), Hylochoerus (giant forest pig), Phacochoerus (warthog)

1-3 1 2-4 3 3 1 2-4 3

= 34-44

warthog (Phacochoerus) skull

Family TAYASSUIDAE (peccaries)

diagnostic characters:

1. size medium (75-105 cm)

2. body covered with stiff bristly hairs

3. digits 4-3, but only two functional in locomotion

4. snout elongate, mobile, flattened at end

5. nostrils opening anteriorly

6. middle two metatarsals fused proximally; metacarpals free

7. paroccipital process small

8. no ventral flange on angular process of lower jaw

2 1 3 3 3 1 3 3

= 38

9. canines with sharp cutting edges; upper canines approximately same size as lower canines, directed downward

10. cheekteeth bunodont, brachydont

range: tropical rainforest and deciduous forests of the New World, from southern Mexico to Argentina

genera: three genera – Catagonus (Chacoan peccary), Pecari (collared peccary or javelina), Tayassu (white-lipped peccary)

skull of a collared peccary, Pecari tajacu

Family HIPPOPOTAMIDAE (hippo, pygmy hippo)

diagnostic characters:

1. mouth very large

2. incisors large (especially inner pair of lower ones), tusk-like

3. size very large (165-500 cm)

4. body virtually hairless

5. digits 4-4, all functional in locomotion

6. snout broad, not mobile or flattened at end

7. nostrils opening dorsally

8. no fusion of metacarpals or metatarsals

9. paroccipital process small

10. angular process of lower jaw with large flange projecting ventrally

11. canines very large, tusk-like; upper canines much smaller than lower canines, directed

range: tropical Africa, south of Sahara

genera: Hippopotamus (hippo); Choeropsis (pygmy hippo)

2-3 1 4 3 1-3 1 4 3

= 38-42

skull of a hippopotamus, Hippopotamus amphibius

Suborder TYLOPODA

Includes the camels and relatives, primitive ruminant ungulates that are restricted to arid and semiarid regions. Camelus, with two species, occupies the Old World, with wild populations persisting only in the Gobi Desert of Asia. Lama, with three species (two domestic [the llama and alpaca] and one wild [guanaco]) and Vicuña occur in the Andes from Peru to Tierra del Fuego. The foot of camels is digitigrade, not unguligrade, although the third and fourth medapodials are fused; they are the only extant fully digitigrade ungulates. The broadened camel foot provides effective support on soft, sandy soils. The skull of camels can be distinguished from that of ruminants by the presence of upper incisors (three pairs in young animals, one in adults). Camels have most of their evolutionary history in North America, spreading to Eurasia and Africa and South America only during the Pleistocene over land bridges; they are now extinct in North America.

Family CAMELIDAE (camels, llamas, vicuñas, guanacos, alpacas)

diagnostic characters:

1. foot posture digitigrade

2. digits 2-2

3. nails present (no hoofs)

4. canon bone in all feet, but fusion not complete at distal end

5. no horns or antlers

6. postorbital bar complete

7. mastoid exposed

8. one pair of upper incisors present in adults, caniniform

1 1 2-3 3 3 0-1 2-3 3

= 30-34

9. canines present, not sharp-edged

10. molars selenodont

11. stomach with three chambers

range: wild populations in Old World limited to Gobi Desert of central Asia; domestic stock introduced worldwide; Andes of New World, from Peru to Tierra del Fuego

genera: Camelus (dromedary and Bactrian camel); Lama (llama, alpaca, guanaco); Vicugna (vicuña)

skull of the dromedary, Camelus dromedaries

Suborder RUMINANTIA

Ruminants are the most evolutionarily derived group of artiodactyls as well as the most taxonomically diverse and abundant. All members are strict herbivores and all are modified for a highly cursorial locomotion. Ruminants chew their cud; the stomach as three or four chambers and supports microorganisms for cellulose digestion (i.e., these are all “foregut” fermenters). All Ruminants have selenodont cheekteeth and the anterior dentition is variously specialized by loss or reduction of the upper incisors, by the development of incisiform lower canines, and commonly by the loss of upper canines. The skull differs from those of members of the suborder Suiformes in the exposure of the mastoid bone between the squamosal and exoccipital bones. Antlers or horns, often large and complex structures, are present in most. The limbs show a pronounced trend toward elongation of the distal segments, fusion of the carpals and tarsals, and perfection of the two-toed foot. Those families in the Infraorder Pecora lack upper incisors, have incisiform lower canines, and fusion of the navicular and cuboid bones of the ankle, which are centered over the astragalus (unfused in Tragulidae, Infraorder Tragulina).

general characters:

1. foot posture unguligrade

2. functional digits usually 2-2, side toes reduced or absent

3. hoofs present

4. cannon bone usually present in all feet (not in forelimbs of tragulids)

5. horns or antlers usually present, at least in males (not in tragulids)

6. postorbital bar complete

7. mastoid exposed

8. no upper incisors

9. if canines present, not sharp-edged

10. molars selenodont

11. stomach complex, usually 4-chambered (3-chambered in tragulids)

phylogenetic relationships among families of the Ruminantia

Infraorder TRAGULINA

Family TRAGULIDAE (chevrotains, mouse deer)

diagnostic characters:

1. size small (height at shoulder less than 30 cm)

2. no horns or antlers

3. tail short

4. neck short

5. digits 4-4; side toes slender, but well developed

6. no lacrimal depression

7. nasal and lacrimal bones adjoining or with little or no separation

8. one lacrimal foramen present, inside orbit

9. upper canines present, long and tusk-like in males

10. surfaces of molars smooth in texture

11. stomach with 3-chambers

range: tropical forests of central and west Africa (Hyemoschus, water chevrotain) and India and SE Asia (Tragulus, mouse deer)

genera: Hyemoschus (chevrotain) and Tragulus (mouse deer)

0 1 3 3 3 1 3 3

= 34

mouse deer, Tragulus, skull

Infraorder PECORA

Superfamily GIRAFFOIDEA

Family GIRAFFIDAE (giraffes)

diagnostic characters:

1. “horns” each composed of a distinct bone (horn is an outgrowth of the frontal bone in other ruminants)

2. additional swelling or “horn” often present medial and anterior to others

3. size very large (height at shoulder 1.5 – 3.7 m)

4. “horns” present in both sexes, unbranched, permanently covered with skin and hair (in “velvet”); velvet and bony core both non-deciduous

5. tail long, tufted at end

6. neck very long

range: Africa, south of Sahara

genera: two genera – Giraffa (the giraffe) and Okapia (okapi)

Superfamily CERVOIDEA

Family MOSCHIDAE (musk deer)

diagnostic characters:

1. small size (height at shoulder 50-70 cm)

2. no horns or antlers

3. tail short

4. digits 4-4, but side toes non-functional

5. lacrimal depression present

6. nasal and lacrimal separated by large oblong opening or fenestration

0 1 3 3 3 1 3 3

= 34

7. one lacrimal foramina present at front edge of orbit

8. upper canines well developed, saber-like

9. surfaces of molars smooth in texture

10. stomach with 4-chambers

11. males have musk gland on abdomen

range: central Asia, from Afghanistan east to China and southern Siberia

genera: the family is monotypic, with the single genus Moschaus (three species)

Family CERVIDAE (deer, elk, muntjac, caribou, reindeer, moose, brockets, pudu)

diagnostic characters:

1. size small to large (height at shoulder 30-240 cm)

2. antlers found only in males (except Rangifer), usually complexly branched (spike-like in most small genera), bony core sheathed in skin and fur (“velvet”) while growing; antler and velvet shed separately, usually annually

3. antlers grow from a pedicle (“ped”), a non-deciduous projection

4. tail short

5. neck short (Alces) to moderately long

6. digits 4-4; side toes small and non-functional

7. lacrimal depression present (lacrimal vacuity – “lv” above)

8. nasal and lacrimal bones separated by large oblong opening or fenestra (antorbital vacuity – “aov” above)

9. two lacrimal foramina present at front edge of or outside orbit (“dlo” above)

10. upper canines present in some taxa, either small and rounded or tusk-like

11. surfaces of molars smooth in texture stomach with 4-chambers

range: worldwide, except for all but extreme northern Africa and all of Australasia (introduced into New Zealand)

0 0-1 3 3 3 1 3 3

=32-34

genera: 16 genera, including Hydropotes (water deer), Muntiacus (muntjacs), Elaphodus (tufted deer), Dama (fallow deer), Axis (axis deer), Cervus (red deer, elk), Elaphurus (Père David’s deer), Odocoileus (mule and white-tailed deer), Capreolus (roe deer), Alces (moose), Rangifer (reindeer), Blastocerus (marsh deer), Ozotoceros (pampas deer), Hippocamelus (huemul), Mazama (brockets), Pudu (pudu)

heads and antler types of representative cervids: clockwise from lower left – Père David’s deer (Elaphurus), moose (Alces), caribou (Rangifer), white-tailed deer (Odocoileus), Chinese water deer (Hydropotes), and pudu (Pudu). Skull is of a sika deer (Cervus)

Family ANTILOCAPRIDAE (pronghorn)

diagnostic characters:

1. size moderate (shoulder height 90 cm)

2. horns, not antlers, present; bone core covered by keratinized sheath that is forked in mature individuals; sheath shed annually (unique characteristic of family); both sexes have horns, but those in females are small and inconspicuous

3. tail short

4. neck moderately long

5. legs especially long and thin

6. digits 2-2; no lateral digits present

7. tarsus with navicular and cuboid fused and ectocuneiform and middle cuneiform fused

8. lacrimal depression absent

0 0 3 3 3 1 3 3 = 30-32

9. nasal and lacrimal bones separated by large opening

10. two lacrimal foramina present, on side of orbit

11. upper canines absent

12. surfaces of molars smooth in texture

13. cheekteeth hypsodont

14. stomach with 4-chambers

range: temperate arid and semiarid grasslands of North America

genera: the family is now monotypic, with the single genus Antilocapra (pronghorn)

Superfamily BOVOIDEA

Family BOVIDAE (antelope, bison, buffalo, cows, goats, muskox, sheep)

diagnostic characters:

1. size small to large (height at shoulder 25-200 cm)

2. horns always present in males, variable in females, unbranched, with hardened keratin sheath; sheath and bony core non-deciduous

3. tail long or short, not tufted

4. neck moderately long

5. digits usually 4-4, but side toes small and non-functional (occasionally absent)

6. lacrimal depression present or absent

7. nasal and lacrimal bones separated or united

8. one lacrimal foramen present, usually inside orbit

9. upper canines absent

10. surfaces of molars smooth in texture

11. stomach with 4-chambers

0 0 3 3 3 1 2-3 3

= 30-32

range: North America, Eurasia, Africa (absent from South America and Australasia); by far the greatest diversity occurs in Africa, secondarily (primarily sheep and goats) in Asia

genera: 45 genera and approximately 140 species, divided into nine subfamilies, including:

Aepycerotinae Aepyceros impala Africa

Alcelaphinae Alcelaphus hartebeest Africa

Connochaetes wildebeest Africa

Damaliscus topi, blesbok Africa

Antilopinae Ammodorcas dibatag Africa

Antidorcas springbok Africa

Antilope bushbuck Africa

Gazella gazelle Africa

Litocranius gerenuk Africa

Madoqua dik-dik Africa

Oreotragus klipspringer Africa

Ourebia oribi Africa

Saiga saiga Eurasia

Bovinae Bison bison NAmer,Europe

Bos cattle worldwide

Boselaphus nilgai Asia

Bubalus Asiatic buffalo Asia

Syncerus African buffalo Africa

Taurotragus eland Africa

Tragelaphus bushbuck, nyala, kudu, bongo Africa

Caprinae Ammotragus barbary sheep Africa

Capra ibex, goat holarctic

Hemitragus tahr Asia

Naemorhedus goral Asia

Oreamnos mountain goat NAmer

Ovibos muskox NAmer

Ovis mouflon, argali, bighorn, sheep holarctic

Rupicapra chamois Eurasia

Cephalophinae Cehalophus duiker Africa

Sylvicapra bush duiker Africa

Hippotraginae Addax addax Africa

Hippotragus roan, sable Africa

Oryx oryx Africa

Peleinae Pelea rhebuck Africa

Reduncinae Kobus waterbuck, kob, lechwe Africa

Redunca reedbuck Africa

ßSuggested phylogeny of bovids, with typical horn morphology for members of each group (tribe) indicated

heads, horn shapes, and sizes of selected bovids: A – suni antelope (Neotragus), B – klipspringer (Oreotragus), C – Grant’s gazelle (Gazella); D – waterbuck (Kobus), E – hartebeest (Alcelaphus), wildebeest (Connochaetes), G – addax (Addax); and H – oryx (Oryx)

skull of a dik-dik (Madoqua)à

ßskull of a bighorn sheep, Ovis canadensis

skull of an oryx (Oryx)

skull of a kob (Kobus) skull of an American bison (Bison)

skull of a steinbuck (Raphiceros)

[skulls drawn proportionally]