Question

please answer 8 my precious were incorrect

E. Identify and briefly describe the diversity (how manysecies and geographic distribution of the two main lineages of extant sarcopterygian fish. Names of lineages (towed 6n ny) How many species Distribution 8. Chondrichthyes have a long evolutionary history. (5) A. In class, we discussed the three main radiations of Chondrichthyes. As discussed in class, identify and briefly describe how three features associated with feeding (also discussed in your text) and locomotion changed during the three main radiations of Chondrichthyes Describe feature in early radiation Describe feature in current radiation Feature B. With respect to the extant Chondrichthyes, give the common names of fish that belong to the two main groups shanks, pays paths one gnou

Answer 1

Feeding character- The character associated with feeding is teeth in shark. In olden times sharks had limited teeth which then became most abundant and numerous. The dentition did not limit to once or twice replacement but could be replaced a 100 times. Also olden fishes like Chimaerans and rabbit fishes had crushing plate dentition. This plate was fused to brain and is now replaced by teeth which can be replaced if broken.

Locomotion- Olden fishes like ctenacanths and hybodonts did not have a soft central part of the spinal cord which made it slightly compressible hence these part were not strong enough to provide a momentum for great speed . in modern time fishes Neoselachians (modern sharks, skates and rays), the central part has become strong and non compressible aiding to great speed.

Feeding character- The Xenacanthida (e.g., Orthacanthus), had terminal mouth with weak jaws whereas modern sharks have greatly strengthened jaw articulations, subterminal mouth and an arrangement of cartilage in the pectoral and pelvic fins that allowed for greater freedom of movement.