<p>Pentremites sp. - fossil blastoid head in the Mississippian of Kentucky, USA.
</p><p>Blastoids are an extinct group of echinoderms.  They resemble crinoids in having a head, or theca, perched atop a long stem of stacked columnals composed of calcite.  Crinoids and blastoids are pelmatozoans - stalked echinoderms.  Both groups are sessile, benthic, filter-feeding organisms.  The overall structure and morphology of crinoid heads and blastoid heads are quite different.  Blastoid heads have pentaradial symmetry and somewhat resemble closed flower buds or nuts.  They have five ambulacral grooves extending outward and downward from the summit of the theca.  During life, many thin, delicate brachioles extended from the ambulacral grooves - these structures captured tiny particles of food from seawater as the blastoid engaged in filter feeding.
</p><p>Classification: Animalia, Echinodermata, Blastozoa, Blastoidea, Spiraculata, Pentremitidae
</p><p>Stratigraphy: Raney Creek Member, Slade Formation, Chesterian Series, Upper Mississippian
</p><p>Locality: Bighill Mountain Outcrop - Route 421 roadcut through Bighill Mountain, ~county line between Rockcastle County and Madison County, south of the town of Bighill, east-central Kentucky, USA (vicinity of 37° 31’ 24.89” North latitude, 84° 12’ 28.15” West longitude)
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<hr><p>More info. at:
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&lt;a href="<a class="external free" href="https://en.wikipedia.org/wiki/Blastoid">https://en.wikipedia.org/wiki/Blastoid</a>" rel="nofollow"&gt;en.wikipedia.org/wiki/Blastoid&lt;/a&gt;
<a rel="nofollow" class="external text" href="https://www.flickr.com/people/47445767@N05">James St. John</a>
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<a rel="nofollow" class="external text" href="https://www.flickr.com/photos/jsjgeology/43924000000/">Pentremites sp. (fossil blastoid) (Raney Creek Member, Slade Formation, Upper Mississippian; Bighill Mountain roadcut, south of Bighill, Kentucky, USA) 1</a>