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Lu et al
- 1. THE RISE OF BONY VERTEBRATE BODY PLAN J. Lu1,2,3,*, M. Zhu1,2,3,*, P.E. Ahlberg4,*, B. Choo5, X.D. Cui3, and Y.-A. Zhu1,2 1Key CAS Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences (CAS), Beijing 100044, China 2CAS Center for Excellence in Life and Paleoenvironment, Beijing 100044, China 3University of Chinese Academy of Sciences, Beijing 100049, China 4Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden 5College of Science and Engineering, Flinders University, Adelaide, Australia *E-mail: lujing@ivpp.ac.cn; zhumin@ivpp.ac.cn; Per.Ahlberg@ebc.uu.se NOTE: PLEASE DO NOT POST THE CONTENT IN OTHER PLACES AS THESE ARE MOSTLY UNPUBLISHED DATA
- 2. Qujing Yunnan Background info: Silurian Xiaoxiang Fauna, QujingďźYunnanďź China Zhu et al., 2009 Zhu et al., 2013 Zhu et al., 2016 Field Work from 2008
- 3. Background info: recent advances and new questions of gnathostome evolution A crown-group or modern gnathostomes comprises osteichthyans, chondrichthyans and acanthodians as stem chondrichthyans are now well-established. Discovery of âmaxillateâ placoderms in Silurian of South China begin to blur the boundary of placoderm and other jawed vertebrates Crown-group gnathostomes Zhu et al., 2013 Zhu et al., 2016
- 4. An exceptionally large fossil fish in the Silurian Choo et al. (2014) Megamastax, represents the largest jawed vertebrate in Silurian
- 5. Field Work in 2014
- 6. New material of Megamastax found from the same site, a complete head
- 7. dorsal flank scales median dorsal scales Scale morphology and squamation 5mm
- 8. Part of the trunk Reconstruction part of Megamastax body scales
- 9. 0.5 mm Morphotype 5 Morphotype 5 anteroventral process Concave dorsal margin 0.5 mm Megamastax: Scale morphology and squamation 0.5 mm Morphotype 1 concave dorsal margin convex ventral margin keel combined peg and anterodorsal processes 0.5 mm Morphotype 3 broad anterior depressed field ventral process straight dorsal margin thick keel
- 10. Chen, 2010 0.5mm 1mm Qu et al., 2013 Psarolepis Andreolepis Youngolepis 0.5mm Megamastax anterior flank scale Scale morphology in selected osteichthyans
- 11. nostril orbit maxillary maxillary opercular subopercular cheek bone posttemporal The head of Magamastax
- 12. CL scanning reveals the sensory canals supraorbital sensory canal infraorbital sensory canal X-ray computed laminography scanner
- 13. dorsal view ventral view jugal premaxilla tooth cushion lower jaw tooth base hyomandibular braincase extrascapulars postorbital premaxilla maxilla Upper jaw Attempting restoration of Magamastax head
- 14. The replacement of the tooth cushion, showing the primitive dental acarde of the bony fish Two types of tooth cushion I II Thicken labial edge
- 15. Tooth cushions of Lophosteus The replacement of the tooth cushion, showing the primitive dental acarde of the bony fish
- 16. facial lamina palatal lamina facial lamina palatal lamina Magamastax Premaxilla without palatal lamina Eusternopteron Entelognathus The premaxilla of Magamastax is with palatal lamina
- 17. The premaxilla of Magamastax is with palatal lamina facial lamina palatal lamina facial lamina palatal lamina Magamastax Premaxilla without palatal lamina Eusternopteron Entelognathus
- 18. Elongate post-hypophysial region of braincase The braincase of Magamastax is like that of placoderms in following featuresďź Entelognathus Mimipiscs Magamastax ⢠Elongate post-hypophysial region of braincase ⢠Enclosed aortic canals
- 19. marginal teeth ectopterygoid basicranial fenestral The braincase of Magamastax is like that of osteichthyans in following featuresďź Magamastax Eusthenopteron marginal teeth ectopterygoid basicranial fenestral ⢠Marginal teeth ⢠Presence of ectopterygoid & coronoid ⢠Presence of basicranial fenestral
- 20. Conclusions The new materials of Magamastax reveals that: ď˛ Tooth cushions resemble those of the stem osteichthyans Lophosteus and Andreolepis. ď˛ Very small and thin rhomboid scales, and no large median dorsal plates. ď˛ The dermal cheekbones resemble those of primitive osteichthyans such as Psarolepis and basal actinopterygians, but the premaxilla differs from known osteichthyans and instead resembles the âmaxillate placodermâ Entelognathus. ď˛ The braincase lacks an intracranial joint and has chondrichthyan-like enclosed aortic canals. ď˛ This trait combination suggests a position close to the gnathostome crown group node and opens novel perspectives on how early osteichthyans evolved their diagnostic features.
- 21. Acknowledgement Thanks to C.-H. Xiong for specimen preparation. And thanks to Y.-M. Hou for the CT Scanning. This work was supported by the Strategic Priority Research Program of Chinese Academy of Sciences, and the National Natural Science Foundation of China
- 22. Thanks for your attention! Questions and comments are welcome!