scholarly journals Character and origin of thick sandstone bodies in the Middle Triassic Doig Formation of Western Canada

2010 ◽  
Author(s):  
J Dixon
Keyword(s):  
Middle Triassic ◽  
Western Canada

Helmolepis cyphognathus, sp. nov., a new platysiagid actinopterygian from the Lower Triassic Sulphur Mountain Formation (British Columbia, Canada)

2005 ◽  
Vol 42 (1) ◽  
pp. 25-36 ◽  
Author(s):  
Andrew G Neuman ◽  
Raoul J Mutter
Keyword(s):  
British Columbia ◽  
New Species ◽  
Central Europe ◽  
Middle Triassic ◽  
Lower Triassic ◽  
Western Canada ◽  
Early Triassic ◽  
East Greenland ◽  
The Family ◽  
A New Species

A new species of stem actinopterygian, Helmolepis cyphognatus sp. nov., is reported from the Lower Triassic Sulphur Mountain Formation of western Canada (probably Smithian). This taxon differs from the only other known Early Triassic platysiagid, H. gracilis from the Lower Triassic Wordie Creek Formation of East Greenland (Griesbachian), in counts of branchiostegal rays, shape of the maxilla, shape (and possibly counts) of extrascapulars, and the size ratio of major opercular bones. In spite of their overall unfavorable preservation, the numerous available specimens amend our knowledge of the little known genus Helmolepis considerably: it has become evident that the morphology of Helmolepis cyphognatus sp. nov. comes closest to Platysiagum minus (Middle Triassic Besano Formation of central Europe). This study suggests placement of the two genera in the family Platysiagidae. Investigation of this new species also shows certain features of the cheek and the caudal fin are more primitive than previously believed, whereas the snout region is probably derived but of yet uncertain affinities in Helmolepis.

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