Imperial College London

Dr. Martin D. Brazeau

Faculty of Natural SciencesDepartment of Life Sciences (Silwood Park)

Lecturer
 
 
 
//

Contact

 

+44 (0)20 7594 2254m.brazeau

 
 
//

Location

 

W2.2KennedySilwood Park

//

Summary

 

Publications

Citation

BibTex format

@article{Giles:2015:10.1038/nature14065,
author = {Giles, S and Friedman, M and Brazeau, MD and Giles, S and Friedman, M and Brazeau, MD and Giles, S and Friedman, M and Brazeau, MD and Giles, S and Friedman, M and Brazeau, MD},
doi = {10.1038/nature14065},
journal = {NATURE},
pages = {82--U175},
title = {Osteichthyan-like cranial conditions in an Early Devonian stem gnathostome},
url = {http://dx.doi.org/10.1038/nature14065},
volume = {520},
year = {2015}
}

RIS format (EndNote, RefMan)

TY  - JOUR
AB - The phylogeny of Silurian and Devonian (443-358 million years (Myr) ago) fishes remains the foremost problem in the study of the origin of modern gnathostomes (jawed vertebrates). A central question concerns the morphology of the last common ancestor of living jawed vertebrates, with competing hypotheses advancing either a chondrichthyan- or osteichthyan-like model. Here we present Janusiscus schultzei gen. et sp. nov., an Early Devonian (approximately 415 Myr ago) gnathostome from Siberia previously interpreted as a ray-finned fish, which provides important new information about cranial anatomy near the last common ancestor of chondrichthyans and osteichthyans. The skull roof of Janusiscus resembles that of early osteichthyans, with large plates bearing vermiform ridges and partially enclosed sensory canals. High-resolution computed tomography (CT) reveals a braincase bearing characters typically associated with either chondrichthyans (large hypophyseal opening accommodating the internal carotid arteries) or osteichthyans (facial nerve exiting through jugular canal, endolymphatic ducts exiting posterior to the skull roof) but lacking a ventral cranial fissure, the presence of which is considered a derived feature of crown gnathostomes. A conjunction of well-developed cranial processes in Janusiscus helps unify the comparative anatomy of early jawed vertebrate neurocrania, clarifying primary homologies in 'placoderms', osteichthyans and chondrichthyans. Phylogenetic analysis further supports the chondrichthyan affinities of 'acanthodians', and places Janusiscus and the enigmatic Ramirosuarezia in a polytomy with crown gnathostomes. The close correspondence between the skull roof of Janusiscus and that of osteichthyans suggests that an extensive dermal skeleton was present in the last common ancestor of jawed vertebrates, but ambiguities arise from uncertainties in the anatomy of Ramirosuarezia. The unexpected contrast between endoskeletal structure in Janusiscu
AU - Giles,S
AU - Friedman,M
AU - Brazeau,MD
AU - Giles,S
AU - Friedman,M
AU - Brazeau,MD
AU - Giles,S
AU - Friedman,M
AU - Brazeau,MD
AU - Giles,S
AU - Friedman,M
AU - Brazeau,MD
DO - 10.1038/nature14065
EP - 175
PY - 2015///
SN - 0028-0836
SP - 82
TI - Osteichthyan-like cranial conditions in an Early Devonian stem gnathostome
T2 - NATURE
UR - http://dx.doi.org/10.1038/nature14065
UR - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000352027700041&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR - http://hdl.handle.net/10044/1/20097
VL - 520
ER -