Ophiocrossota sp. - fossil brittle star in fossiliferous sandy limestone from the Miocene of California, USA. (field of view: ~6.4 centimeters across)
<p>This specimen may be Ophiocrossota baconi or Ophiocrossota oweni.
</p><p>"Brittle stars" are technically called ophiuroids.  They are starfish-like organisms with a central disc and slender, snake-like arms.  Brittle stars first appear in the Ordovician and continue into the Holocene.  Unlike starfish, brittle stars do not have coelomic extensions in their arms.  Each arm is skeletal and composed of pieces of calcite called vertebrae (vertebral plates).  Brittle star arms move in a serpentine manner and tend to break off easily.  The arms may be complexly branched.  In terms of locomotion, ophiuroids are more mobile than starfish.  The feeding style for most brittle stars is filter feeding or scavenging, but some are predatory.
</p><p>The ophiuroid specimen seen here is in a remarkable fossiliferous limestone that is almost all brittle star bodies.  The limestone matrix has a significant component of quartz sand.
</p><p>Classification: Animalia, Echinodermata, Asterozoa, Ophiuroidea, Ophiurida, Ophiuridae
</p><p>Stratigraphy: Santa Margarita Formation (possibly the lower Santa Margarita Formation), Upper Miocene
</p><p>Locality: private ranch in the Lopez Lake area, above the town of San Luis Obispo, southern California, USA
</p>
<hr><p>See info. at:
en.wikipedia.org/wiki/Brittle_star
and
</p>
en.wikipedia.org/wiki/Ophiuridae
James St. John
CC BY 2.0
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