Lab 14-Orders PRIMATES & SCANDENTIA

ORDER PRIMATES: shared and derived characters

1. locomotor characters:

· grasping hands and feet with opposable pollux (thumb) and hallux (big toe)

· hallux contains a nail

· nails present on all or most digits (may be modified secondarily into a claw)

· elongation of the calcaneus

· hindlimb dominance during locomotion (except in brachiators)

· center of gravity shifted towards hindlimbs

Strepsirhines:

lemur (Eulemur: Lemuridae)

sifaka (Propithecus: Indridae)

potto (Arctocebus: Loridae)

aye-aye (Daubentonia: Daubentoniidae)

Haplorhines:

tarsier (Tarsius: Tarsiidae)

marmoset (Callitrhrix: Callitrichidae)

spider monkey (Brachyteles: Cebidae)

gorilla (Gorilla: Hominidae)

hands (left) and feet (right) of strepsirhine (above) and haplorhine (below) primates

Locomotor styles among primates are perhaps more variable than any other group of mammals. Those illustrated here include, from left to right: arboreal plantigrade [note longer hind limbs] (lemur), arboreal vertical clingers and leapers (tarsier), terrestrial plantigrade [note longer forelimbs] (vervet monkey), terrestrial knuckle-walking (gorilla), brachiation [note extremely long forelimbs] (gibbon), bipedal terrestrial walking (chimpanzee)

2. Stereoscopic vision

· forward rotation of the orbits and narrowing of the interorbital distance

· enlargement of the orbital cavity

· exposure of the ethmoid bone on the inner orbital wall

· stereoscopic vision in which approximately half of the retinal axons project to the ipsilateral side of the brain

· complete postorbital bar or plate (plate of haplorhine primates unique among mammals)

3. Auditory bulla bony; the floor formed by the petrosal bone, with tympanic ring or

tube present

4. Dentition

a. dental formula with two incisors and three premolars (loss of one incisor and one premolar from primitive eutherian condition)

b. molars tritubercular or quadritubercular, bunodont and brachydont

Phylogeny and classification

Primates are traditionally divided into two suborders, the composition of which varies depending upon the placement of the tarsier (family Tarsiidae). Older classifications tended to place tarsiers with lemurs and lorises, into the Suborder Prosimii, with monkeys and apes in the Suborder Anthropoidea. Most primatologists now believe that tarsiers are wither more closely related to monkeys and apes, and thus define two suborders (Strepsirhini and Haplorhini) based on characteristics of the nose and the enclosed bony orbit, or regard tarsiers as a third group equally distinct from both prosimian and anthropoid primates.

The classification in most common use at the moment is the following:

Suborder Strepsirhini

Family Cheirogaleidae – dwarf lemurs

Family Lemuridae – lemurs

Family Megaladapidae – sportive lemurs

Family Indriidae – woolly lemur and sifaka

Family Daubentoniidae – aye-aye

Family Loridae (also called Lorisidae) – lorises, potto

Family Galagonidae – galagos

Suborder Haplorhini

Infraorder Tarsii

Family Tarsiidae – tarsiers

Infraorder Platyrrhini

Family Callitrichidae – marmosets and tamarins

Family Cebidae – New World monkeys

Infraorder Catarrhini

Family Cercopithecidae – Old World monkeys

Family Hylobatidae – gibbons

Family Hominidae – orang, gorilla, chimp, man

Suborder STREPSIRHINI

diagnostic characteristics:

1. naked, glandular rhinarium with median cleft (called the philtrum) and slit-like nostrils (diverticulum nasi) directed laterally. [This is the primitive condition for mammals in general.]

2. presence of a tooth comb, composed of lower incisors and canine teeth (secondarily lost in Daubentoniidae) projecting forward from lower jaw, used in grooming (Tupaiidae [Scandentia] have a similar tooth comb, but one that does not include the canines)

3. grooming claw on the second digit of the foot

Family LEMURIDAE

(lemurs)

general characters: 1. size medium (50-100 cm) 2. limbs subequal in length 3. digits each bearing a nail, except for 2^nd digit of hindfoot which bears a claw 4. tail long, furred 5. fur woolly 6. ventral surface of hindfoot naked 7. braincase elongate 8. rostrum elongate 9. orbits large, usually with prominent ridge around each 10. ectotympanic ring in bulla free, not fused ventrally to petrosal bulla 11. upper incisors uniformly small, peg-like, with median diastema 12. molars tritubercular

range: Madagascar, Comoro Islands

Family CHEIROGALEIDAE

(dwarf and mouse lemurs)

defining characters: similar in cranial details to true lemurs, but differ by being very small to small (12-30 cm) and the upper incisors are well developed, not small and peg-like, and are not separated by a median diastema. As with other lemurs, a tooth comb comprised of the incisors and canines is present on the lower jaw. genera: Microcebus (mouse lemurs), Allocebus (dwarf lemurs), Phaner (fork-marked lemurs)

pygmy mouse lemur (Microcebus myoxinus)

Family MEGALADAPIDAE

(sportive lemurs)

defining characters: similar in cranial details to true lemurs, but lack upper incisors in adults and lack the bold markings often characterizing true lemurs. genera: monotypic – Lepilemur (sportive lemurs)

sportive lemur (Lepilemur mustelinus)

Family INDRIIDAE Family DAUBENTONIIDAE

(indri, sifakas, woolly lemurs) (aye-aye)

Verreau’s sifaka (Propithecus verreauxi)

aye-aye (Daubentonia)

Family LORIDAE (often incorrectly spelled LORISIDAE)

(pottos, lorises)

general characters: 1. size relatively small (18-80 cm) 2. hindlimbs much longer than forelimbs 3. digits each bearing a nail except for the 2^nd digit of hindfoot, which bears a claw 4. tail very short or absent 5. fur soft, dense, somewhat woolly 6. ventral surface of hindfoot haired at heel 7. rostrum short 8. braincase spherical 9. orbits large, usually with prominent ridge around each 10. ectotympanic ring fused to petrosal bulla ventrally 11. upper incisors uniformly very small, peg-like, and with median diastema 12. lower incisors usually comb-like, procumbent 13. lower canine incisiform 14. molars quadritubercular

dental formula:

1-2 1 3 3 2 1 3 3

= 34-36

genera: Arctocebus (potto), Loris (slender loris), Nycticebus (slow lorises), Perodictus (potto)

range: Africa, south of the Sahara; India and Sri Lanka; Southeast Asia; East Indies.

slender loris (Loris)

potto (Perodicticus potto)

slender loris (Loris tardigradus)

Family GALAGONIDAE

(galagos or bush babies)

general characters:

1. small size (like a squirrel), large eyes, expressive ears that resemble those of some bats

2. tail long and well furred

3. hindlimbs especially long with powerful thigh muscles

4. skull with long rostrum

5. lower incisors and canines procumbent, specialized as tooth-comb (used in grooming and feeding on tree resin)

6. ectotympanic ring fused to petrosal bulla ventrally

7. both pollux and hallux large and opposable

8. 4^th digits are unusually long

9. distal most pad of all digits with well developed traction ridges used in climbing

10. 2^nd digit of hindfoot short and bears a claw for grooming; all other digits with flattened nails

11. hindfoot especially elongated (tarsal elements), for springing locomotion

dental formula:

2 1 3 3 2 1 3 3

= 36

genera: Galago (bush babies), Galagoides (dwarf bush baby), Otolemur (thick-tailed bush baby)

range: Africa, south of the Sahara

Otolemur (thick-tailed bush baby)

Suborder HAPLORHINI

diagnostic characters:

1. nose with simple nostrils, no rhinarium, philtrum vestigial or absent; internarial breadth wide in Tarsius and all platyrrhines (with nostrils directed somewhat laterally) and comparatively narrow in all catarrhines (with nostrils directed forward)

2. orbit and temporal fossa separated by postorbital plate (see illustrations above)

3. braincase relatively large and rounded, not elongated

4. foramen magnum more or less directly ventrally

Infraorder TARSII

Family TARSIIDAE

(tarsiers)

general characters: 1. size relatively small (20-45 cm) 2. hindlimbs longer than forelimbs 3. claws on 2^nd and 3^rd digits of hindfoot and nails on remaining digits 4. digits very elongate, terminating in enlarged discs 5. tail long, naked or sparsely haired, often tufted at end 6. rostrum short 7. orbits enormous, with prominent ridge around each 8. orbit incompletely walled off from temporal fossa 9. auditory bulla extending laterally as a bony tube 10. upper and lower incisors well developed, not equal in size; no median diastema in upper incisors; lower incisors vertical, not procumbent 11. molars tritubercular

dental formula:

2 1 3 3 1 1 3 3

= 34

genera: the family is monotypic – Tarsius (tarsier)

range: Indonesian and Philippine islands

tarsier (Tarsius)

upper right molars 1^st and 2^nd lower left molars

tarsier (Tarsius)

Infraorder PLATYRRHINI

Platyrrhine primates are exclusive to the New World, and include the traditional families Callitrichidae (tamarins and marmosets) and Cebidae (howler, spider, capuchin, woolly, squirrel, owl, titi, saki, and other monkeys). Sometimes Goeldi’s monkey (Callimico) is placed in its own family, the Callimiconidae. Phylogenetic analyses, including both anatomical characters as well as molecular sequences, however, suggest that this simple arrangement is incorrect. The tree below (from Horovitz, I. 1999. A phylogenetic study of living and fossil platyrrhines. American Museum Novitates, no. 3269) illustrates one phylogenetic arrangement that places the owl monkey (Aotus) and a clade comprised of the capuchins (Cebus) and squirrel monkeys (Saimiri) as sisters to the tamarins/marmosets, with the larger monkeys arranged in two clades (the Pithecidae and Atelidae). We will follow the traditional division of the Callitrichidae (including Callimico) and Cebidae here, but you should be aware of recent suggested changes.

Platyrrhines are differentiated from the Old World catarrhine monkeys and apes by the following characters:

1. three premolars above and below, instead of two

2. nostrils directed laterally, as opposed to forward

3. prehensile tail present (in some genera only; unique among primates)

4. no ischial callosities (not present in catarrhine family Hominidae)

5. dichromatic, rather than trichromatic, color vision (except howler monkey)

Family CALLITRICHIDAE

(marmosets and tamarins)

general characters: 1. size small (30-90 cm) 2. forelimbs approximately equal in length to hindlimbs 3. pollex not opposable; hallus opposable 4. digits each bearing a claw except for hallux, which bears a flat nail 5. tail long, not prehensile 6. auditory bulla not extending laterally as bony tube 7. molars tritubercular 8. three premolars and two molars above and below (except Callimico, which has three molars)

dental formula:

2 1 3 2 2 1 3 2

= 32 (3 molars above and below in Callimico)

genera: Callimico (callimico – sometimes placed in own family, Callimiconidae), Callithrix (tamarins), Cebuella (pygmy marmoset), Leontopithecus (lion tamarins), Saquinus (tamarins)

range: New World tropics, from Panama to southern Brazil

Saguinus (tamarin)