BISC 316 Lecture Notes - Lecture 5: Tullimonstrum, Branchial Arch, Semicircular Canals
11 Dec 2016
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Paraphyleti(cid:272) asse(cid:373)(cid:271)lage of jawless fishes (cid:272)alled (cid:862)ostra(cid:272)oder(cid:373)s(cid:863) Plus other: living agnathans, new fossil evidence. Majority of fossil agnathans found in north america; some from australia and china. Continental position different: north america, europe, and asia were equatorial, most of north america covered by tethys sea. Fossil bed analysis: all animals were marine. Means they were evolved in the ocean, not freshwater: first vertebrates were benthic. Benthic means they were associated with the bottom of a water-body: abundant flora. Algael reefs at the time of origin of vertebrates. Used for feeding and hiding in the reefs. Three major groups: cambrian agnathans, ostracoderms. Hagfishes and lampreys: cambrian agnathans, myllokunmingia and haikouichthys, early cambrian (~540 mya, vertebrate characterisitcs, cranium, w-shaped myomeres, notochord with vertebral elements, sense organs clustered in head region. Inner ear: branchial arches, appear to be more derived than hagfishes, have dorsal fin, numerous other things that hagfish do not have, no bone or mineralized water.
