Classification of the Echinoidea

Natural History Museum - London, UK
 
Stem group Echinoidea
Family Bothriocidaridae Kelm, 1904
BothriocidarisNeobothriocidarisUnibothriocidaris              
....Family Eothuriidae MacBride & Spencer, 1938
..........Eothuria
Unnamed family
..........Aulechinus
....Unnamed family
..........Bromidechinus
....Family Echinocystitidae Gregory, 1897
..........Echinocystites
GotlandechinusRhenechinus
....Family Lepidesthidae Jackson, 1896
..........Lepidesthes, Meekechinus
....Family Lepidocentridae Loven, 1874
..........AptilechinusElliptechinusLepidechinoidesLepidocentrus,
..........LepidechinusMyriastrichesPalaeodiscusPholidechinus
....Family Cravenechinidae Hawkins, 1946
..........CravenechinusXenechinus
....Family Proterocidaridae Smith, 1984
..........FournierechinusHyattechinusPerischodomusPerischocidarisPholidocidarisPronechinusProtoechinusProterocidaris
....Family Palaechinidae McCoy, 1849
..........LovenechinusMaccoyaMelonechinusOligoporus,
..........PalaechinusPorechinusXystria
....Family Archaeocidaridae McCoy, 1844
..........AlbertechinusArchaeocidarisDeneechinusLepidocidaris,
..........NortonechinusPermocidarisPolytaxicidaris
....Stem group incertae sedis
..........LanternariusKongielechinusProtocidarisRhoechinus,
..........Silurocidaris, Tornquistellus

Primitive stem group Euechinoidea
Cidaroidea and/or advanced stem group Echinoidea
Family Tiarechinidae Gregory, 1897
..........Tiarechinus
Family Triadocidaridae Smith, 1990
..........LevicidarisMegaporocidarisMikrocidarisParvicidaris,
..........TriadocidarisVinchuscanchaiaZardinechinus
Family Serpianotiaridae Hagdorn, 1995
..........Serpianotiaris
Family Paurocidaridae Vadet, 2001
..........Paurocidaris

Crown group Echinoidea

Subclass Cidaroidea Smith, 1984
Order Cidaroida Claus, 1880
Stem group Cidaroida
† Family Triadotiaridae Hagdorn, 1995
† Family Serpianotiaridae Hagdorn, 1995
† Family Miocidaridae Durham & Melville, 1957
Crown group Cidaroida
† Family Polycidaridae Vadet, 1988
† Family Diplocidaridae Gregory, 1900
† Family Rhabdocidaridae Lambert, 1900
Superfamily Histocidaridea
Family Histocidaridae Lambert, 1900
Superfamily Cidaridea [possibly includes Paurocidaris Kier, 1977]
Family Cidaridae Gray, 1825 [includes Cidarinae Mortensen, 1928; †Stereocidarinae Lambert, 1900; †TypocidaridaeVadet, 1988; Phyllacanthina Smith & Wright, 1989; Goniocidaridae Mortensen, 1928]
Family Ctenocidaridae Mortensen, 1928 [incerta sedis]
Family Psychocidaridae Ikeda, 1936 [includes † Roseicidaridae Vadet, 1991]

Subclass Euechinoidea Bronn, 1860
Order Echinothurioida Claus, 1880
Family Kamtosomatidae Mortensen, 1934
Family Phormosomatidae Mortensen, 1934 [includes Paraphormosomatinae Smith & Wright, 1990]
Family Echinothuriidae Wyville Thompson, 1872 [includes Hygrosomatinae Smith & Wright, 1990 and Sperosomatinae Smith & Wright, 1990]
† Family Pelanodiademinae Hess, 1972 [includes Pelanechinidae Groom, 1887]

Infraclass Acroechinoidea Smith, 1981
Order Micropygoida Kroh & Smith, 2010
Family Micropygidae Mortensen, 1903
Order Aspidodiatematoida Korh & Smith, 2010
Family Aspidodiadematidae Duncan, 1889
Order Diadematoida Duncan, 1889 [restricted usage]
Family Diadematidae Gray, 1855
Order Pedinoida Mortensen, 1939
Family Pedinidae Pomel, 1883

Infraclass Carinacea Kroh & Smith 2010 † Family Hemicidaridae Wright, 1857 [includes Pseudocidarinae Smith & Wright, 1993]
† Family Pseudodiadematidae Pomel, 1883
† Family Orthopsidae Duncan, 1889

Crown group Echinacea Claus, 1876
Order Stomopneustoida nov. † Family Stomechinidae Pomel, 1883
Family Stomopneustidae Mortensen, 1903
Family Glyptocidaridae Jensen, 1982
Unnamed clade [Arbacioida + Camarodonta]
† Family Glyphopneustidae Smith & Wright, 1993 [incerta sedis]
Order Arbacioida Gregory, 1900
† Family Glypticidae Lambert & Thiéry, 1914
† Family Acropeltidae Lambert & Thiéry, 1914
Family Arbaciidae Gray, 1855 [includes Coelopleuridae Märkel, 1969]
Order Camarodonta Jackson, 1912
Family Parasaleniidae Mortensen, 1903 
Superfamily Temnopleuridea nov.
Family Temnopleuridae A. Agassiz, 1872
† Family Glyphocyphidae Duncan, 1889
† Family Zeuglopleuridae Lewis, 1986
Family Trigonocidaridae Mortensen, 1903
Superfamily Echinidea nov.
Family Echinidae Gray, 1825
Family Parechinidae Mortensen, 1903
Superfamily Odontophora Kroh & Smith, 2010
Family Toxopneustidae Troschel, 1872
Family Strongylocentrotidae Gregory, 1900
Family Echinometridae Gray, 1855

Calycina Gregory, 1900
Stem group Calycina
Order Phymosomatoida Mortensen, 1904
† Family Diplopodiinae Smith & Wright, 1993
† Family Emiratiidae Ali, 1990
† Family Heterodiadematidae Smith & Wright, 1993
Family Phymosomatidae Pomel, 1883
Order Salenioida Delage & Herouard, 1903
Stem group Salenioida
† Family Acrosaleniidae Gregory, 1900
† Family Pseudosaleniidae Vadet, 1999b
† Family Goniophorini Smith & Wright, 1990
† Family Hyposaleniinae Mortensen, 1934
Crown group Salenioida
Family Saleniidae L. Agassiz, 1838 [includes Salenocidarini Smith & Wright, 1990 and † Holosaleniini Smith & Wright, 1990]

Irregularia Latreille, 1825
Stem group Irregularia
† Family Pygasteridae Lambert, 1900
Order Holectypoida Duncan, 1889
† Family Discoididae Lambert, 1900
† Family Coenholectypidae Smith & Wright, 1999
† Family Holectypidae Lambert, 1900
† Family Anorthopygidae Wagner & Durham, 1957
Crown group Irregularia
Order Echinoneoida H. L. Clark, 1925
Family Echinoneidae L. Agassiz & Desor, 1847
Superfamily Conulidea Kroh & Smith, 2010
† Family Galeritidae Gray, 1825
† Family Conulidae Lambert, 1911
[† Family Neoglobatoridae Endelman, 1980]

Microstomata Smith, 1984
Stem group Microstomata
† Family Desorellidae Vadet, 1997
† Family Galeropygidae Lambert, 1911
† Family Clypeidae Lambert, 1898

Crown group Microstomata
Neognathostomata Smith, 1981
Stem group Neognathostomata
† Family Nucleolitidae L. Agassiz & Desor, 1847
Crown group Neognathostomata
Family Apatapygidae Kier, 1962
† Family Pygaulidae Lambert, 1905
† Family Archiaciidae Cotteau & Triger, 1869 [includes † Claviasteridae Ali, 1992]
† Family Clypeolampadidae Kier, 1962
Order Cassiduloida L. Agassiz & Desor, 1847
Superfamily Cassidulina Philip, 1963
Family Cassidulidae L. Agassiz & Desor, 1847
† Family Faujasiidae Lambert, 1905 [includes † Stigmatopyginae Smith & Wright, 2000]
Superfamily Neolampadina Philip, 1963 [ex. Neolampadoida]
Family Neolampadidae Lambert, 1918 [includes † Pliolampadidae Kier, 1962]
Order Echinolampadoida Kroh & Smith, 2010.
Family Echinolampadidae Gray, 1851
Order Clypeasteroida L. Agassiz, 1835
Stem group Clypeasteroida
† Family Plesiolampadidae Smith & Jeffery, 2000
† Family Conoclypeidae Zittel, 1879
† Family Oligopygidae Duncan, 1889
Crown group Clypeasteroida
Suborder Clypeasterina L. Agassiz, 1835
Family Clypeasteridae L. Agassiz, 1835 [includes Clypeasterinae L. Agassiz, 1835; Ammotrophinae Durham, 1955; Arachnoidinae Duncan, 1889]
† Family Fossulasterinae Philip & Foster, 1971 [includes † Scutellinoididae Irwin, 1995]
Suborder Scutellina Haekel, 1896
Stem group Scutellina
† Family Scutellinidae Cotteau, 1892
Infraorder Laganiformes Desor, 1847
Family Fibulariidae Gray, 1855 [includes Echinocyamidae Lambert & Thiéry, 1914]
Family Laganidae A. Agassiz, 1873 [includes Laganinae A. Agassiz, 1873; † Neolaganinae Durham, 1954]
Infraorder Scutelliformes Haekel, 1896
Family Taiwanasteridae Wang, 1984 [incertae sedis]
Stem group Scutelliformes
† Family Protoscutellidae Durham, 1955
Crown group Scutelliformes
Family Echinarachniidae Lambert, 1914
† Family Scutellidae Gray, 1825
† Family Eoscutellidae Durham, 1955
† Family Scutasteridae Durham, 1955
Family Dendrasteridae Lambert, 1889
† Family Abertellidae Durham, 1955
Family Rotulidae Gray, 1855 
Family Astriclypeidae Stefanin, 1911
† Family Monophorasteridae Lahille, 1896
Family Mellitidae Stefanini, 1911

Atelostomata Zittel, 1879
Stem group Atelostomata
† Genus Hyboclypus L. Agassiz, 1839
† Genus Pygorhytis Pomel, 1883 [Family † Pygorhytidae Lambert, 1909]
† Family Collyritidae d'Orbigny, 1853
† Family Tithoniidae Solovjev, 1966
† Family Disasteridae Gras, 1848
† Family Acrolusiidae Mintz, 1968
Crown group Atelostomata
Order Holasteroida Durham & Melville, 1957
Stem group Holasteroida
† Family Hemipneustidae Lambert, 1917
† Family Pseudholasterinae Smith & Jeffery, 2000]
† Family Stenonasteridae Lambert, 1922
Meridosternata Lovén, 1883
† Family Echinocorythidae Wright, 1856
† Family Holasteridae Pictet, 1857
Infraorder Cardiasterina Pomel, 1883 [includes Stegasterina Lambert, 1917]
† Family Stegasteridae Lambert, 1917
† Family Cardiasteridae Lambert, 1917 [includes Cardiotaxinae Smith & Jeffery, 2000]
Crown Group Meridosternata
Family Corystidae Foster & Philip, 1978 [incertae sedis]
Family Calymnidae Mortensen, 1907
Infraorder Urechinina H.L. Clark, 1946
Family Carnarechininae Mironov, 1993
Family Urechinidae Duncan, 1889
Family Plexechinidae Mooi & David, 1996
Family Pourtalesiidae A. Agassiz, 1881

Order Spatangoida L. Agassiz, 1840
Stem group Spatangoida
† Family Toxasteridae Lambert, 1920
† Family Somaliasteridae Wagner & Durham, 1966
Crown group Spatangoida
Family Micrasteridae Lambert, 1920 [includes Cyclasterinae Poslavskaya, 1964]
Family Aeropsidae Lambert, 1896 [includes † Corasterinae Lambert & Thiéry, 1924]
† Family Ovulasteridae Lambert, 1896
Family Hemiasteridae H. L. Clark, 1917
Family Palaeostomidae Lovén, 1868
Suborder Paleopneustina 
Superfamily Schizasteridea Lambert, 1905
Stem group Paleopneustina
† Family Periasteridae Lambert, 1920
Crown group Paleopneustina
Family Schizasteridae Lambert, 1905 [includes Brisasterinae Markov, 1994]
Family Prenasteridae Lambert, 1905 [includes † Unifasciidae Cooke, 1959]
Superfamily Paleopneustidea A. Agassiz, 1904
Family Pericosmidae Lambert, 1905
Family Paleopneustidae A. Agassiz, 1904
Superfamily Brissidea Stockley et al. 2005
Stem group Brissidea
† Family Brissidea Lambert, in Lambert & Thiéry, 1924
Family Palaeotropidae Lambert, 1896
Family Brissidae Gray, 1855 [including Brissopsidae Lambert, 1905]
Suborder Spatangina Fischer, 1966
Stem group Spatangina
† Family Megapneustinae Fourtau, 1905
† Family Macropneustidae Lambert, 1895
Crown groupSpatangina
Family Spatangidae Gray, 1825
Family Eupatangidae Lambert, 1920
Family Maretiidae Lambert, 1905
Family Eurypataginae Kroh, 2007
Family Loveniidae Lambert, 1905 [includes Breyninae Lambert, 1905; Echinocardiidae Wythe Cooke, 1942]
 
 
Echinolampas ovalis, Middle EoceneCivrac-en-Médoc, France.

The earliest echinoid fossils date to the upper part of the Ordovician period (circa 450 Mya), and the taxon has survived to the present as a successful and diverse group of organisms. Spines may be present in well-preserved specimens, but usually only the test remains. Isolated spines are common as fossils. Some echinoids (such as Tylocidaris clavigera, from the Cretaceous period's English Chalk Formation) had very heavy, club-shaped spines that would be difficult for an attacking predator to break through and make the echinoid awkward to handle. Such spines simplify walking on the soft sea floor.

 
Pseudocidaris club-shaped spine; Matmor Formation (Middle Jurassic) of Makhtesh GadolIsrael.

Most of the fossil echinoids from the Paleozoic era are incomplete, consisting of isolated spines and small clusters of scattered plates from crushed individuals, mostly in Devonian and Carboniferous rocks. The shallow-water limestones from the Ordovician and Silurian periods of Estonia are famous for echinoids. Paleozoic echinoids probably inhabited relatively quiet waters. Because of their thin tests, they would certainly not have survived in the wave-battered coastal waters inhabited by many modern echinoids. During the upper part of the Carboniferous period, a marked decline in echinoid diversity occurred, and this trend continued to the Permian period. They neared extinction at the end of the Paleozoic era, with just six species known from the Permian period. Only two lineages survived this period's massive extinction and into the Triassic: the genus Miocidaris, which gave rise to modern cidaroida (pencil urchins), and the ancestor that gave rise to the euechinoids. By the upper part of the Triassic period, their numbers began to increase again. Cidaroids have changed very little since the Late Triassic and are today considered to be living fossils. Diversity of echinoids have been fluctuating across the eons. Among the different proxies, marine facies variation in combination with outcrop area best explains the palaeodiversity curve.[38]

The euechinoids, though, diversified into new lineages throughout the Jurassic and into the Cretaceous periods, and from them emerged the first irregular echinoids (superorder Atelostomata) during the early Jurassic, and later the other superorder (Gnathostomata) of irregular urchins, which evolved independently. These superorders today represent 47% of all extant species of echinoids because of their adaptive breakthroughs, which allowed them to exploit habitats and food sources unavailable to regular echinoids. During the Mesozoic and Cenozoic eras, the echinoids flourished. Most echinoid fossils are often abundant in the restricted localities and formations where they occur. An example of this is Enallaster, which exists by the thousands in certain outcrops of limestone from the Cretaceous period in Texas. Many fossils of the Late Jurassic Plesiocidaris still have the spines attached.

Some echinoids, such as Micraster, which is found in the Cretaceous period Chalk Formation of England and France, serve as zone or index fossils. Because they evolved rapidly, they aid geologists in dating the surrounding rocks. However, most echinoids are not abundant enough and are of too limited range to serve as zone fossils.

In the Paleogene and Neogene periods (circa 66 to 1.8 Mya), sand dollars (order Clypeasteroida) arose. Their distinctive, flattened tests and tiny spines were adapted to life on or under loose sand. They form the newest branch on the echinoid tree.

 
Sea Urchin Phylogeny [39]
 
The Cidaroida like this Stylocidaris affinis constitute a specific branching among modern sea urchins.

Phylogeny

 
Sea urchins belonging to the Irregularia like this Clypeaster have lost their spherical shape and their radial symmetry.

According to WoRMS:[40]

Source: en.wikipedia.org/wiki/Sea_urchin