12 Chondrichthyes first appeared in the fossil record more than The Devonian and

Question

12 Chondrichthyes first appeared in the fossil record more than The Devonian and were common by the Devonian. had ancestral features such as lack of claspers, elongate skull, amphistylic jaw suspension, broad-based triangular, paired fins, and no anal fin. These early sharks had sharp, multicusped teeth that showed signs of wear (indicating slow tooth replacement). a. b. c. d. 200 mya e. 100 mya 600 mya 400 mya 300 mya Acanthodii (spiny sharks) Xenacanthii (xenacanth sharks) Holocephali (chimaeroid sharks) Cladoselachii (cladoselachian sharks) Neoselachii (hybodont sharks) 13 Based on morphological similarities and recent molecular evidence,_are the considered by most ichthyologists to be the closest living piscine relatives of tetrapods. a. Bichirs/reedfishes b. Coelacanths c. Lungfishes d. Osteolepids 14 The first lungs were formed by a. dorsal outpouchings of the gut of bony fishes b. ventral outpouchings of the gut of bony fishes c. dorsal outpouchings of the kidneys of sharks d. ventral outpouchings of the pharynx of agnathans

Explanation / Answer

Condrichthyes i.e cartilaginous fishes first appeared in the fossil record by about 395 million years ago, during the middle Devonian. So the answer is 400 mya. The devonian cladoselachii had ancestral features like lack of claspers, elongate skull, amphistylic jaw suspension, broad-based triangular, paired fins and no anal fin. These early sharks have sharp multicusped teeth that showed signs of wear.

13) Based on morphological similarities and recent molecular evidence, lungfishes are the considered by most ichthyologists to be the closest living piscine relatives of tetrapods.

14) The first lungs were formed from the ventral outpouching of the gut of bony fishes. It is formed from swim bladder which is formed from the gut or digestive tube outpouching.

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