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Prionocidaris granulostriata (Desor, 1855)

 

Fragmentary remains and isolated spines of Prionocidaris granulostriata are common in the southwest, though relatively scarce elsewhere, ranging from the Upper Cenomanian to Middle Turonian (Terebratulina lata zone).  The test is distinctive - tall and large, with a large number of primary tubercles / interambulacral plates.  Rare complete examples are a classic fossil of the Devonshire Chalk.  The closely related Prionocidaris vendocinensis has a similar test, but in practise P. granulostriata can be distinguished by its stratigraphic occurrence (pre-Sternotaxis plana zone) and its spine form - the spines attributed to P. granulostriata are relatively short, with a narrow spindle-like profile and coarse ribs (those of P. vendocinensis are extremely long and tapering with a barb-like ornament).

 

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1).  (A) A rare, medium-sized example of a complete test (x2.1, lowermost Turonian, Holywell Nodular Chalk, 30 cm above the Stacked Hardgrounds of Mortimore et al.,  2001, Beer, Devon, A. Lindsay Collection, image used by kind permission);  (B) A primary spine of the form attributed to P. granulostriata (x2.3, Lower Turonian, Branscombe, Devon, BMNH (British Museum (Natural History) London) E82368.  Image  2010 The Natural History Museum, by kind permission.

 

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B

2).  (A) Apical and (B) lateral views of the above specimen (A x2.0, B x2.4) (Images used by kind permission of A. Lindsay).

 

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B

3).  A seemingly unique specimen - a large test retaining a large and partially articulated lantern; (A) Apical and (B) oral views (x1.7, White Chalk?, Devon(?), Booth Museum, by kind permission of John Cooper).