1 / 17

Evolution & Adaptations of Placoderms

Evolution & Adaptations of Placoderms. Justin Waraniak, Yovaan Totharam, Hanjie Mo, Kevin Hsiao. What are placoderms?. Main group of vertebrates in aquatic environments during the Devonian Period (~420-360 Mya ) . Diverse G roup found everywhere on earth

ugo
Download Presentation

Evolution & Adaptations of Placoderms

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Evolution & Adaptations of Placoderms Justin Waraniak, Yovaan Totharam, Hanjie Mo, Kevin Hsiao

  2. What are placoderms? Main group of vertebrates in aquatic environments during the Devonian Period (~420-360 Mya). Diverse Group • found everywhere on earth • adapted to many different lifestyles. • included both the largest and smallest vertebrates of the time.

  3. What are placoderms? Had a set of bony plates that covered the anterior of the body. One of the first groups to evolve a complex set of jaws.

  4. Why study placoderms? Bony plates make well-preserved fossils; make itpossible to see details in morphology and bodily structures.

  5. Why study placoderms? Interesting Morphologies • Dunkleosteus - jaws • Bothriolepis - possible lungs Unknown Relationship to Other Gnathostomes Extinction Extinction

  6. Dunkleosteus terrelli • Arthrodira • 380-360 million years ago • Large size, "tank-like," posterior unknown • Gluttonous predator • Jaw diversification

  7. Study Methods • Difficulty with prehistoric ecological issues • Biomechanical Models, laws of physics • Cleveland Shale • Muscle cast measurements

  8. Results • 6000N, 7000N • Suction capability, 1/15s • Four Bar Linkage mechanism (Anderson, 2007)

  9. Evolutionary History • Short Lifespan • Sharks • Gouges and Scratches • Anterior bite margin • Evolutionary trend • Derived fish lower jaws • T-rex and Alligator bite

  10. Bothriolepis • Found worldwide, specifically in shallow marine and freshwater environments • head and trunk shield (anti-predator) • bottom feeders • spiral digestive tract

  11. Lungs of Bothriolepis • Often cited as the earliest vertebrates with both gills and lungs • large pectoral fins could have been used for support • "if sedimentary structures could be interpreted as traces of some digestive organs, none could be interpreted as putative lungs." (Goujet, 2011) • discovery of soft-tissue preservation shows that if not "lungs" some how part of the branchial chamber (Janvier, 2007)

  12. Phylogenetic Relationships Within the Placoderms Johanson’s statements: Antiarchs have blood vessels that go through scapulocoracoid, pectoral fin, and wall of gill chamber Rostrocaudal canal goes to the back of the gill chamber Antiarchs more similar to Osteostraci – armored agnathans Young’s views: Johanson’s conclusions were wrong Rostrocaudal canal does not go to the back of the gill chamber. Monophyly maintained. (Young, 2008)

  13. Evolutionary Placement of Placoderms 3 Hypotheses (Gardiner, 1984) 1. Placoderms are the collateral descendants of all other gnathostomes 2. Placoderms are more closely related to chondrichthyans than to other gnathostomes 3. Placoderms are more closely related to osteichthyans than to chondrichthyans (Young, 2010)

  14. Structures

  15. Extinction Went extinct atthe end of the Devonian Mass extinction between the Frasnian and Famennian periods. Allowed Chondrichthyans and Actinopterygians to diversify. (Sallan, 2010)

  16. Future Work/ Conservation • More fossils being uncovered. • Resolve the evolutionary tree of gnathostomes • Understand why/how such a diverse group went extinct; understand how mass extinctions occur.

  17. Overview/ Questions • http://www.youtube.com/watch?v=L0PmA5ZjpOA

More Related