Lab1Example - Sections 1 , ,smallcuspsonmolars,,wide...

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Sections: 1. As a result of our observations, we believe that the anthropoid common ancestor had a dental formula of 2­1­3­3, small cusps on molars, a sexually dimorphic canine, wide incisors, and a diet that consisted mainly of fruit. Any trait that both anthropoids possess is one that their anthropoid common ancestor most likely had as well. Both the spider monkey and the orangutan have small cusps on their molars, relatively large canines, wide incisors, and diets that were largely centered around consuming fruit. With traits that differ between the spider monkey and the orangutan (both anthropoids), it was necessary to refer to the outgroup, the prosimian (lemur). The outgroup acted as a tiebreaker for dental morphology. Both the lemur and spider monkey had the dental formula 2­1­3­3, so it is reasonable to assume that the anthropoid common ancestor had the same formula. In terms of evolutionary significance, broad incisors and low cusps on premolars and molars tend to show that the primate was a frugivore. This leads to the assumption that the animal was an energy maximizer that spent more than average energy searching and protecting food. Relatively larger canines, compared to Lemurs, in the common ancestor suggests more frequent male aggression. The differences in traits in prosimians and anthropoids in the reconstruction demonstrate evolutionary adaptations. 2. After measuring the arms and legs of the two anthropoids (orangutan and spider monkey) and the prosimian (lemur), I discovered that two of the three primates’ mode of locomotion was quadrupedal. I was able to conclude this because their intermembral indexes fell around the 95 range. Intermembral indexes were found by dividing arm lengths in centimeters by leg lengths in centimeters, and then multiplying that number by 100. The spider monkey’s index was ~85 and the lemur’s index was ~90. The other anthropoid we

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