| Hemicidaris Temporal range: Middle Jurassic-Early Cretaceous | |
|---|---|
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| Hemicidaris intermedia fossil from France in Cosmocaixa, Barcelona. | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Echinodermata |
| Class: | Echinoidea |
| Subclass: | Euechinoidea |
| Order: | Hemicidaroida |
| Genus: | Hemicidaris Agassiz, 1838 |
Hemicidaris is an extinct genus of echinoids that lived from the Middle Jurassic to the Early Cretaceous. Its remains have been found in Africa, Asia, and Europe.
A genus is a taxonomic rank used in the biological classification of living and fossil organisms, as well as viruses, in biology. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclature, the genus name forms the first part of the binomial species name for each species within the genus.
The Middle Jurassic is the second epoch of the Jurassic Period. It lasted from about 174 to 163 million years ago. Fossil-bearing rocks from the Middle Jurassic are relatively rare, but some important formations include the Forest Marble Formation in England, the Kilmaluag Formation in Scotland, the Daohugou Beds in China, Itat Formation in Russia, and the Isalo III Formation of western Madagascar.
The Early Cretaceous or the Lower Cretaceous, is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 146 Ma to 100 Ma.
