. Comparative anatomy. Anatomy, Comparative. BDELLOSTOMA. VGILL APERTURES (?) â ""'''" â C. PETR0MY2DN Fig. 16.âThree characteristic genera of CyclostomesâBdellostoma, Myxine, and Petromyzon. That they are the most primitive vertebrates is shown in many traits, such as a permanent notochord, absence of paired appendages and jaws, etc. (Redrawn after Dean.) There are no scales in the skin, and the teeth are horny. Some species are hermaphroditic. Paired appendages are absent. The lamprey, Petromyzon, is a familiar genus which undergoes meta- morphosis during its development. Its
. Comparative anatomy. Anatomy, Comparative. BDELLOSTOMA. VGILL APERTURES (?) â ""'''" â C. PETR0MY2DN Fig. 16.âThree characteristic genera of CyclostomesâBdellostoma, Myxine, and Petromyzon. That they are the most primitive vertebrates is shown in many traits, such as a permanent notochord, absence of paired appendages and jaws, etc. (Redrawn after Dean.) There are no scales in the skin, and the teeth are horny. Some species are hermaphroditic. Paired appendages are absent. The lamprey, Petromyzon, is a familiar genus which undergoes meta- morphosis during its development. Its larval stage is known as ammo- coetes. Other genera are Myxine and Bdellostoma. Class Ostracodermi The ostracoderms are fossil forms which, as Stensio and others have shown, resemble cyclostomes in some striking respects. UnUke the latter, however, their heads were covered by heavy bony armor. Like the lam- preys they lacked jaws and paired appendages. As in cyclostomes the nasal aperture was median and dorsal in position. It has been asserted but not demonstrated that the ostracoderms are the ancestors of carti- laginous fishes, which are consequently assumed to have lost their heavy body exoskeletons. Most morphologists, however, consider ostracoderms. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Neal, Herbert V. (Herbert Vincent), 1869-1940; Rand, Herbert W. (Herbert Wilbur), 1872-1960. Philadelphia : P. Blakiston's Son
Size: 2913px × 858px
Photo credit: © The Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookpublisherphi, booksubjectanatomycomparative
