- Hadrocodium
Taxobox
name = "Hadrocodium"
fossil_range = EarlyJurassic
regnum =Animal ia
image_width = 250px
image_caption = "Hadrocodium" skull
phylum =Chordata
subphylum =Vertebrata
unranked_classis =Amniota
classis =Synapsida
unranked_ordo =Mammaliaformes
genus = "Hadrocodium""Hadrocodium wui" is an extinct basal
mammal species that lived during the LowerJurassic (approx. 195 million years ago, during theSinemurian stage) in what is now theYunnan province ofChina . "Hadrocodium" was a mere 3.2 cm (1.35 in) in length (about 2 grams), and is one of the smallest mammals of either theMesozoic orCenozoic periods."Hadrocodium" is the earliest known example of several features distinctive to mammals [ [http://www.palaeos.com/Vertebrates/Units/Unit420/420.300.html Symmetrodonta - Palaeos] ] , including mammal-like mandible and
middle-ear structures and a relatively largebrain cavity [ [http://archives.cnn.com/2001/TECH/science/05/24/tiny.ancestor/index.html Tiny creature may be ancestor of all mammals - CNN] ] . The discovery of "Hardocodium" suggests that the origination of these distinctivemammaliaform features was much older (45 million years older) than previously thought.Whether "Hadrocodium" was endothermic or
cold-blooded has not been settled, although its apparent nocturnal features would seem to place it in the endotherm group.References
Bibliography
* cite journal
author = Z.-X. Luo, A. W. Crompton and A.-L. Sun
year = 2001
title = A New Mammaliaform from the Early Jurassic and Evolution of Mammalian Characteristics
journal =Science
volume = 292
pages = 1535–1540
url = http://www.carnegiemnh.org/vp/media/Luo(Hadrocodium).pdf
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