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Blastoid Pentrerites, stemmed Echinoderm (No.116)

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Blastoid Pentrerites, stemmed Echinoderm (No.116)
Blastoid Pentrerites, stemmed Echinoderm
from Illinois, USA 320 Million Years
Carboniferous Period

Measurements of specimen  Approx.     Measurement of Matrix Approx.
Height - 1.1 cm                                             Height - 1.6 cm
Width - 1.2 cm                                             Width - 4.5 cm
Length - 1.4 cm                                            Length - 6.2 cm



Blastoids (class Blastoidea) are an extinct type of stemmed echinoderm. Often called sea buds, they first appear, along with many other echinoderm classes, in the period, and reached their greatest diversity in the Mississippian sub-period of the Carboniferous period. However, blastoids may have originated in the Cambrian. Blastoids persisted until their extinction at the end of Permian, about 250 million years ago. Although never as diverse as their contemporary relatives, the crinoids, blastoids are common fossils, especially in many Mississippian-age rocks.



Like most echinoderms, blastoids were protected by a set of interlocking plates of calcium carbonate, which formed the main body.

The mouth was located at the summit of the body. Radiating like flower petals from the center were five food grooves, or ambulacra. Each ambulacrum had many long, thin, fine structures called brachioles, which were used to trap food particles and bring them to the mouth.

Like crinoids, blastoids were high-level, stalked suspension feeders (feeding mainly on planktoinc organisms) that inhabited clear-to-silty, moderately agitated ocean waters from shelf to basin.


 

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