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Some comments on the Placoderm parasphenoid

Kim DENNIS-BRYAN

en Bulletin du Muséum national d'Histoire naturelle, 4ème série – section C – Sciences de la Terre, Paléontologie, Géologie, Minéralogie 17 (1-4) - Pages 127-142

Published on 01 September 1995

Parasphenoids have or are being described in thirty-nine genera of the Placodermi. All but three of the genera are arthrodires. The actual number of parasphenoids preserved is very small. A review of the literature reveals that many questions regarding this bone remain unanswered e.g., its origin, what is the primitive and advanced condition, what changes occur during growth. Though used by some authors as a character that is diagnostic of particular groups of arthrodire, it seems on existing evidence that the parasphenoid is species specific. There are few indications, at the present time, that the bone is useful in working out placoderm relationships.
Keywords :
Placodermi, parasphenoid