Document Detail


Description of a cranial endocast from a fossil platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the relevance of endocranial characters to monotreme monophyly.
MedLine Citation:
PMID:  16710845     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
A digital cranial endocast of the Miocene platypus Obdurodon dicksoni was extracted from high-resolution X-ray computed tomography scans. This endocast represents the oldest from an unequivocal member of either extant monotreme lineage and is therefore important for inferring character support for Monotremata, a clade that is not well diagnosed. We describe the Obdurodon endocast with reference to endocasts extracted from skulls of the three species of extant monotremes, particularly Ornithorhynchus anatinus, the duckbill platypus. We consulted published descriptions and illustrations of whole and sectioned brains of monotremes to determine which external features of the nervous system are represented on the endocasts. Similar to Ornithorhynchus, well-developed parafloccular casts and reduced olfactory bulb casts are present in the Obdurodon endocast. Reduction of the olfactory bulbs in comparison with tachyglossids and therian mammals is a potential apomorphy for Ornithorhynchidae. The trigeminal nuclei, ganglia, and nerves (i.e., trigeminal complex) are enlarged in Obdurodon, as evidenced by their casts on the endocast, as is the case in the extant platypus. The visibility of enlarged trigeminal nucleus casts on the endocasts of Obdurodon and Ornithorhynchus is a possible synapomorphy of Ornithorhynchidae. Electroreception and enlargement of the trigeminal complex are possible synapomorphies for Monotremata.
Authors:
Thomas E Macrini; Timothy Rowe; Michael Archer
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Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Journal of morphology     Volume:  267     ISSN:  0362-2525     ISO Abbreviation:  J. Morphol.     Publication Date:  2006 Aug 
Date Detail:
Created Date:  2006-08-14     Completed Date:  2006-09-08     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  0406125     Medline TA:  J Morphol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1000-15     Citation Subset:  IM    
Copyright Information:
Copyright 2006 Wiley-Liss, Inc.
Affiliation:
Jackson School of Geosciences and University of Texas High-Resolution X-ray Computed Tomography Facility, University of Texas at Austin, 78712, USA. tmacrini@mail.utexas.edu
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MeSH Terms
Descriptor/Qualifier:
Animals
Fossils
Monotremata / anatomy & histology
Platypus / anatomy & histology*
Skull / anatomy & histology*,  radiography
Species Specificity

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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