Lab 2

Apomorphic

"derived"; evolutionary novelties that were newly-evolved in the last common ancestor of the group in question - in this case all primates. Among the derived characteristics that distinguish primates from other mammals are: 1. grasping hands and feet with an opposable big toe (hallux) and thumb (pollex) 2. nails instead of claws 3. apical pads on the tips of the digits 4. forward-facing eyes 5. stereoscopy and a wide binocular visual field 6. eye sockets ("orbits") completely encircled by bone (a postorbital bar) 7. a large number of visual areas in the brain 8. small litter sizes (usually just 1 offspring per birth) 9. a long period of infant dependency

Plesiomorphic

"primitive"; ancient characteristics retained from a more distant ancestor. Other primitive traits that characterize primates include: 1. a generalized / relatively unspecialized dentition 2. retention of five digits on the hands and feet 3. retention of the clavicle (collar bone)

Platyrrhini

1. (P/D?) flat noses with nostrils that point inferolaterally 2. (P) three premolars: most have a 2.1.3.3/2.1.3.3 dental formula, except the callitrichids 3. (P) cartilaginous ear tube (external acoustic meatus), i.e., no bony ear tube 4. found in Central and South America (New World monkeys) 5. all are diurnal (active by day), except the for the owl monkey (Aotus) 6. all are arboreal (tree-living) 7. (D) some have prehensile tails (e.g. Ateles, the spider monkey) 8. consists of two families, the Cebidae and the Callitrichidae 9. Zygomatic and parietal cranial bones contact, frontal and sphenoid do not

Hominoidea

1. includes apes and humans 2. apes include the smaller-bodied gibbons and siamangs ("lesser" apes) and the larger-bodied apes : gorillas, chimpanzees, bonobos, and orangutans ("great" apes). 3. found in Asia (gibbons, siamangs, and orangutans) and Africa (chimps, bonobos, and gorillas) 4. (D) mediolaterally broad, ventrodorsally shallow thorax 5. (P) Y-5 molars (lower molars have 5 cusps separated by Y-shaped valley) 6. (D) lack tails

Phylogeny

is a hypothesis of evolutionary relationships.

Catarrhini

1. (P/D?) narrow nostrils point forward or downward 2. (D) two premolars: dental formula is 2.1.2.3/2.1.2.3 3. (D) bony ear tube (external acoustic meatus) 4. non-human catarrhines are found in Africa and Asia 5. consist of two Superfamilies, the Cercopithecoidea (Old World monkeys) and the Hominoidea (apes and humans) 6. vary in molar morphology: members of the Cercopithecoidea have bilophodont molars and members of the Hominoidea have Y-5 molars 7. includes both arboreal and terrestrial species 8. all are diurnal 9. Frontal and sphenoid cranial bones contact, zygomatic and parietal do not 9. Catarrhini can be further subdivided into two Superfamilies: Cercopithecoidea (Old World monkeys) and Hominoidea (humans and apes). There are two subfamilies of cercopithecoids with different dietary adaptations: the primarily folivorous (leaf-eating) Colobinae and the primarily frugivorous (fruit-eating) Cercopithecinae.

Cercopithecoidea

1. Old World monkeys 2. (P) mediolaterally narrow, ventrodorsally deep thorax (chest) 3. (D) bilophodont molars (molar teeth with two transverse ridges)

Strepsirrhines

1. lemurs: found only on the island of Madagascar (off the southeastern coast of Africa) 2. lorises: found in both mainland Africa and Asia 3. galagos: found only in mainland Africa Traits that characterize strepsirrhines include (P = primitive for the group, D = derived for the group): 1. (P) unfused mandibular symphysis (right and left halves of the mandible separated) 2. (P) unfused frontal suture (right and left halves of the frontal bone separated) 3. (P) postorbital bar (bony strut that forms the lateral margin of the orbit) 4. (D) grooming claw on the second digit of the foot 5. (D) tooth comb (procumbent and elongated lower teeth, including incisors and canines, used for grooming fur) 6. (P) presence of a rhinarium (moist hairless nose similar to dogs and cats) Of these features, only the grooming claw and tooth comb are synapomorphies (= shared apomorphies) of strepsirrhines. All of the other features listed are strepsirrhine symplesiomorphies (= shared plesiomorphies) retained from the last common ancestor of all primates. As mentioned earlier, tarsiers (genus Tarsius) are sometimes placed with strepsirrhines in the alternative primate suborder Prosimii (= "prosimians") because (like many strepsirrhines) tarsiers are small, nocturnal, and insectivorous. Tarsiers also share some of the primitive features of strepsirrhines such as an unfused mandibular symphysis, but tarsiers do not have a tooth comb. Tarsiers are unique in having two grooming claws on each foot rather than one as in strepsirrhines. Tarsiers do share many apomorphies with anthropoids (= monkeys, apes, and humans), such as the presence of a retinal fovea, loss of the rhinarium, a reduction in the size and complexity of the nasal fossa, and a disk-shaped placenta. These shared derived features (synapomorphies) indicate that tarsiers are phylogenetically more closely related to anthropoids than they are to strepsirrhines. Accordingly, most modern taxonomists place tarsiers with anthropoids into the suborder Haplorhini rather than with strepsirrhines in the suborder Prosimii.

Colobinae

1. primarily folivorous 2. narrow incisors 3. (D) high sharp molar cusps for shearing leaves 4. (D) complex, sacculated stomachs 5. more arboreal than the cercopithecines and often have longer hindlimbs

Cercopithecinae

1. primarily frugivorous 2. broader incisors than colobines 3. (P) low rounded molar cusps for mashing fruit 4. (D) cheek pouches 5. many are terrestrial (ground dwelling) and have shorter hindlimbs than colobines

Example of apomorphic and plesiomorphic characteristics

For example, forward-facing eyes are an apomorphic feature of primates because forward-facing eyes were newly-evolved in the last common ancestor of all living primates. Similarly, hair is a plesiomorphic feature of primates, because hair was newly-evolved in the common ancestor of all mammals. Hair is simply retained in most mammalian orders (including primates) that share this common ancestor.

Tarsiers

In primates for example, we have two different taxonomic schemes depending on the relationship of tarsiers (Tarsius) to the rest of the primates. Taxonomists have been typically considered tarsiers (Tarsius) as morphologically and ecologically more similar to lemurs and lorises than to monkeys, apes and humans. As a result, tarsiers have historically been placed in the Suborder Prosimii (prosimians) with lemurs and lorises, whereas monkeys, apes and humans are placed in Anthropoidea. However, cladistic techniques for phylogenetic reconstruction (which rely solely on evolutionary novelties, or apomorphies, to generate phylogenies) clearly demonstrate that tarsiers are more closely related to monkeys, apes and humans than they are to lemurs or lorises. Accordingly, many modern taxonomists recognize the common ancestry of tarsiers, monkeys, apes and humans by placing these primates in Haplorhini, and placing lemurs and lorises in Strepsirrhini.

Taxonomy

The branch of biology that deals with naming, classifying, and grouping organisms. Modern taxonomy recognizes that organisms often have similar morphological characteristics because they share common ancestry. Remember - organisms are placed into various taxa based upon shared characteristics. For example, all members of superfamily Hominoidea (including humans, chimps, bonobos, gorillas, orangutans, and gibbons) lack a tail.

Anthropoids

are a more diverse taxonomic group than the prosimians, and can be further subdivided into two infraorders: Platyrrhini (New World monkeys) and Catarrhini (Old World monkeys, apes, and humans). Anthropoid traits include: 1. (D) fused mandibular symphysis (right and left halves of the mandible fused) 2. (D) fused frontal (metopic) suture (right and left halves of the frontal bone fused) 3. (D) complete postorbital closure = bar + plate of bone completely separating the eyes from the chewing muscles on the side of the braincase 4. (P/D?) absence of a grooming claw 5. (D) relative brain size is typically larger than that found in prosimians