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Cephalaspidomorphi - Wikipedia, the free encyclopedia (258 words) |
 | Some biologists no longer use the name Cephalaspidomorphi because relations among osteostraci and anaspida are unclear, and the affinities of the lampreys are also contested. |
| Others have restricted the cephalaspidomorphs to include only groups more clearly related to the Osteostraci, such as Galeaspida and Pituriaspida, that were largely unknown in the 1920s. |
| Many reference works still regard Cephalaspidomorphi as a Linnean class whose sole living representaties are the lampreys. |
| Palaeos Vertebrates 50.600 Thelodonti: Osteostraci (2730 words) |
| The Osteostraci share a number of unique characteristics - synapomorphies - with the gnathostomes or jawed fish (true bone, epicercal tail, sclerotic ring, endolymphatic openings, dorsal jugular vein, concentrated paired fins) and were clearly closely related. |
| The Osteostraci are biogeographically limited to the Euramerican Province (Laurentia and Baltica), and are useful biostratigraphic indicators. |
| The brain turns out to be quite similar to the lamprey brain, which is also taken as a sign that the Osteostraci are but a fruit stand on the broad highway to the gnathostomes. |
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