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Sea urchins are spiny, globular echinoderms in the class Echinoidea. About 950 species of sea urchin are distributed on the seabeds of every ocean and inhabit every depth zone from the intertidal seashore down to 5,000 meters. The spherical, hard shells (tests) of sea urchins are round and covered in spines. Most urchin spines range in length from 3 to 10 cm, with outliers such as the black sea urchin possessing spines as long as 30 cm (12 in). Sea urchins move slowly, crawling with tube feet, and also propel themselves with their spines. Although algae are the primary diet, sea urchins also eat slow-moving (sessile) animals. Predators that eat sea urchins include a wide variety of fish, starfish, crabs, marine mammals, and humans.
Diadema is a genus of sea urchins of the family Diadematidae.
Coelopleurus is an extant genus of echinoids with fossil records dating back to the Eocene, with remains found in Europe and North America.
Cassiduloida is an order of sea urchins. The group was extremely diverse with many families and species during the Mesozoic, but today, only seven extant species remain.
The Echinothurioida are an order of sea urchins in the class Echinoidea. Echinothurioids are distinguished from other sea urchins by the combination of a flexible test and hollow spines. The membrane around the mouth contains only simple plates, in contrast to the more complex mouth parts of their close relatives, the Diadematoida. They are nearly all deepsea dwellers.
The Camarodonta are an order of globular sea urchins in the class Echinoidea. The fossil record shows that camarodonts have been in existence since the Lower Cretaceous.
Holasteroida is an order of irregular sea urchins.
Tripneustes is a genus of sea urchins belonging to the family Toxopneustidae.
Calveriosoma gracile is a species of sea urchin in the order Echinothurioida. It is a deep water species and is found on the seabed in western parts of the Pacific Ocean at depths of 200 to 800 metres.
Irregularia is an extant infraclass of sea urchins that first appeared in the Lower Jurassic.
The Echinothuriidae are a family of sea urchins in the order Echinothurioida. Due to their soft skeletons, most are called "leather urchins", but species in the genus Asthenosoma are also known as "fire urchins" due to their bright colors and painful, venomous sting.
Toxopneustes roseus is a species of sea urchin from the East Pacific. It is sometimes known as the rose flower urchin or the pink flower urchin. Like the related flower urchin, they are venomous.
Toxopneustes elegans is a species of sea urchin endemic to Japan. Like the closely related flower urchin, they are venomous.
Toxopneustes maculatus is a rare species of sea urchin found in the Indo-West Pacific.
Chondrocidaris is a genus of sea urchins of the family Cidaridae described in 1863 by Alexander Agassiz. There are two living species and several fossil species dating as far back as the Miocene.
Asterocidaris is a genus of fossils sea urchins in the family Hemicidaridae. These epifaunal grazer-deposit feeders lived in the Middle and Upper Jurassic age.
Araeosoma is a genus of deep-sea sea urchins in the family Echinothuriidae.
Tetragramma donaldtrumpi is a species of fossil sea urchins discovered and identified by William R. Thompson Jr. in 2016. The specimen locality is from the Lower Cretaceous, Trinity Group, of the Glen Rose Formation near Fischer, Texas, in the United States.
Amblypneustes is a genus of sea urchins, belonging to the family Temnopleuridae.
Tetrapygus is a genus of sea urchins in the family Arbaciidae. It is a monotypic genus and the only species is Tetrapygus niger which was first described by the Chilean naturalist Juan Ignacio Molina in 1782. It is found in the southeastern Pacific Ocean on the coasts of South America.
References
- ↑ "Tetragramma Agassiz, 1838". The Echinoid Directory. Natural History Museum, London. Retrieved 2017-01-22.
- ↑ Kroh, A. (2010). Tetragramma L. Agassiz, 1838 †. In: Kroh, A. & Mooi, R. (2015) World Echinoidea Database. Accessed at http://www.marinespecies.org/Echinoidea/aphia.php?p=taxdetails&id=512465 on 2017-01-22
- 1 2 3 Vaziri, M. R.; Arab, A. L. (2013). "Echinoids of the genus Tetragramma Agassiz (Phymosomatoida) from the Aptian sediments of the Basab region, northwest of Kerman, Iran". Journal of Sciences, Islamic Republic of Iran. 24 (2): 149–155.
- ↑ Thompson, William R. (2016). Fossil Echinoids of Texas: A Monograph of Fossil Sea Urchins. River Stix. ISBN 978-1617042782.
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