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Arthraster dixoni (Forbes)

 

Remains of this large and distinctive starfish are exceptionally scarce.  The arms are elongate and finger-like.  The ossicles of the aboral surface bear pronouced central ridges.  The higher level affinities of Arthraster have not yet been resolved, but several morphological features suggest they belong with the Stauranderastids. 

 

1).  A well preserved but contorted specimen, exposing both the oral and aboral surface of the arms (x2.1, White Chalk, Berwick(?), Sussex(?), Potter  collection, Booth Museum, BMB 017043, by kind permission of John Cooper).

 

2).  Detail of the above specimen, showing the aboral (upper) surface of an arm.  The characteristic central-ridges of the ossicles are well displayed (x6.5).

 

3).  The large type specimen, displaying the oral surface (x1.3, Lower Chalk, Balcombe Pit, near Amberley, West Sussex, Dixon Collection, BMNH (British Museum (Natural History) London) 47000.  Image  2005 The Natural History Museum, by kind permission.

 

4).  The aboral surface of the above specimen (x2.0).  Image  2005 The Natural History Museum, by kind permission.