The following passage is an excerpt from a natural science essay on evolutionary biology.
While both the Early Devonian placoderms and the later Carboniferous chondrichthyans possessed jaw structures derived from the first pharyngeal arch, their functional mechanics diverged. Placoderms utilized a perichondral joint system that locked the upper jaw directly to the braincase, restricting lateral movement but maximizing vertical shearing force. Conversely, chondrichthyans developed a hyostylic jaw suspension, which, by utilizing the hyoid arch as a dynamic hinge, permitted the jaw to protrude forward. Thus, unlike the placoderms, whose static cranial integration limited prey size, chondrichthyans could swallow prey larger than their oral cavity.
According to the passage, which of the following represents an explicit contrast between the jaw structures of Early Devonian placoderms and Carboniferous chondrichthyans?
- APlacoderms utilized a hyostylic suspension to maximize vertical shearing force, whereas chondrichthyans relied on a perichondral system to restrict lateral jaw movement.
- Chondrichthyans possessed a flexible suspension that allowed the jaw to extend forward, whereas placoderms had a static integration that locked the upper jaw to the braincase.Answer
- CChondrichthyans developed their jaw structures prior to the formation of the first pharyngeal arch, whereas placoderms evolved their perichondral systems much later.
- DChondrichthyans had a perichondral joint system that allowed them to swallow prey of any size, whereas placoderms used a hyoid arch that limited prey size.