AP BIOLOGY

CLASSIFICATION

CHARACTERISTICS OF PRIMATES

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Which of the following traits is useful for grouping catarrhines together as a clade?
A
2.1.2.3 dental formula
B
fused frontal sutures
C
the loss of tail
D
Y-5 molars
Explanation: 

Detailed explanation-1: -A major feature that distinguishes catarrhine primates from their platyrrhine relatives is the number of premolars on each quadrant. Catarrhines only possess two premolars, in contrast to the three premolars of New World monkeys. This leads to a dental formula of 2.1.2.3 (Fig. 1c).

Detailed explanation-2: -They are characterized by having a narrow nose. Their nostrils are close together as opposed to platyrrhines that have a flat-bridged nose. Other distinctive features include having flat fingernails and toenails, eight instead of 12 premolars, and lacking prehensile tails.

Detailed explanation-3: -Platyrrhines have broad noses with nostrils that are far apart + face outward. Catarrhines have narrow noses with nostrils that are close together + face downward.

Detailed explanation-4: -They are small to medium sized primates (ranging from 0.1 kg to 15 kg) and are distinguished from the catarrhines by several features. Firstly, NWMs have broad, flat nostrils, while catarrhines have narrow, downward pointing nostrils (Figure 1). Secondly, NWMs have three premolar teeth, while catarrhines have two.

Detailed explanation-5: -In many primates, from Old World monkeys to great apes, the typical dental formula is 2:1:2:3. This means that if we divide the mouth into quadrants, each should have two incisors, one canine, two premolars and three molars. In total that is eight teeth a quadrant, for a total of 32 teeth.

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