''Echinosphaerites'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of rhombiferan cystoid

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...

s that lived in the Early to Middle

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. T ...

of North America and Europe (Bockelie, 1981).

Biology

Echinosphaerites had branched biserial brachioles which is rare for species belonging to the Class

Rhombifera The Eocrinoidea are an extinct class of echinoderms that lived between the Early Cambrian and Late Silurian periods. They are the earliest known group of stalked, arm-bearing echinoderms, and were the most common echinoderms during the Cambrian. ...

. Echinosphaerites had a skeletal meshwork like many other blastozoan echinoderms, with a fine outer mesh layer and an inner coarse mesh layer. During evolution the number and location of these brachioles, including the branching patterns, increased in the number of brachioles and complexity of the branching pattern. The exothecal pore structures increased in the complexity of patterns of tangential canals (Bockelie, 1981).

References

* Bockelie, J.F., 1981. Functional morphology and evolution of the cystoid ''Echinosphaerites''. Lethaia 14: 189–202.

External links

''Echinosphaerites''
in the

Paleobiology Database The Paleobiology Database is an online resource for information on the distribution and classification of fossil animals, plants, and microorganisms. History The Paleobiology Database (PBDB) originated in the NCEAS-funded Phanerozoic Marine Pale ...

Functional morphology and evolution of the cystoid ''Echinosphaerites''
in the Wiley Online Library Cystoidea Blastozoa genera Ordovician echinoderms of Europe Fossils of the Czech Republic Letná Formation Ordovician echinoderms of North America Early Ordovician first appearances Middle Ordovician extinctions {{paleo-echinoderm-stub