Belongs within: Cassiduloida.
The Pliolampadidae are a heterogenous group of irregular echinoids known from the Upper Cretaceous to the present (Kier 1966).
Characters (from Kier 1966): Medium-sized to large, apical system monobasal, three or four genital pores; petaloid pores strongly conjugate, single pore in all ambulacral plates beyond petals; periproct marginal, inframarginal or supramarginal, usually longitudinal; bourrelets usually well developed; buccal pores present; usually no naked zone in interambulacrum 5 adorally.
<==Pliolampadidae |--+--Santeelampas Cooke 1959K66 | | `--*S. oviformis (Conrad 1850) [=Catopygus oviformis]K66 | |--Gitolampas Gauthier 1889 (see below for synonymy)K66 | | |--*G. tunetana (Gauthier 1889) [=Pliolampas tunetana, *Bothriolampas tunetana]K66 | | |--‘Echinanthus’ georgiensis Twitchell 1915 [=*Echanthus georgiensis]K66 | | |--G. lamberti Checchia-Rispoli 1921 [=*Gitolampopsis lamberti]K66 | | `--G. zuffardii Checchia-Rispoli 1921SG93 | `--+--Neocatopygus Duncan & Sladen 1882K66 | | `--*N. rotundus Duncan & Sladen 1882K66 | |--Ilarionia Dames 1878K66 | | `--*I. beggiatoi (Laube 1868) [=Echinanthus beggiatoi]K66 | |--Kephrenia Fourtau 1909K66 | | `--*K. lorioli Fourtau 1909K66 | `--Daradaster Tessier 1952K66 | `--*D. peroni Tessier 1952K66 `--+--Zuffardia Checchia-Rispoli 1931K66 | `--*Z. sanfilippoi (Checchia-Rispoli 1914) [=Pseudocatopygus sanfilippoi]K66 `--+--Termieria Lambert 1931K66 | `--*T. henrici Lambert 1931K66 |--Pseudopygaulus Coquand 1862 (see below for synonymy)K66 | |--*P. trigeri (Coquand 1862) [=Catopygus trigeri]K66 | |--‘*Eolampas’ antecursor Duncan & Sladen 1882K66 | |--‘*Petalaster’ maresi Cotteau 1885K66 | `--‘*Ottiliaster’ pusillus Penecke 1885K66 `--+--Pliolampas Pomel 1888 (see below for synonymy)K66 | |--*P. gauthieri (Cotteau 1880) [=Echinolampas gauthieri, *Plesiolampas gauthieri]K66 | |--P. baixadoleitensis (Maury 1934) [=Breynella baixadoleitensis]SG93 | |--‘Echinolampas’ elegantulus Cotteau 1883 [=*Milletia elegantula]K66 | `--‘Pygorhynchus’ vassalli Wright 1855 [=*Breynella vassalli]K66 `--Studeria Duncan 1891 (see below for synonymy)K66 |--*S. elegans (Laube 1869) [=Catopygus elegans]K66 |--‘*Phaleropygus’ oppenheimi de Loriol 1902K66 |--S. recens Agassiz 1879 [=*Hypselolampas recens]K66 `--‘Nucleolites’ subcarinatus Goldfuss 1826 [=*Tristomanthus subcarinatus]K66
Gitolampas Gauthier 1889 [=Bothriolampas Gauthier 1889; incl. Echanthus Cooke 1942, Gitolampopsis Checchia-Rispoli 1921]K66
Pliolampas Pomel 1888 [=Plesiolampas Pomel 1883 non Duncan & Sladen 1882; incl. Breynella Gregory 1891, Milletia Duncan 1891]K66
Pseudopygaulus Coquand 1862 [incl. Eolampas Duncan & Sladen 1882, Ottiliaster Penecke 1885, Petalaster Cotteau 1885 non Gray 1840]K66
Studeria Duncan 1891 [incl. Hypselolampas Clark 1917, Phaleropygus de Loriol 1902, Tristomanthus Bittner 1892]K66
*Type species of generic name indicated
References
[K66] Kier, P. M. 1966. Cassiduloids. In: Moore, R. C. (ed.) Treatise on Invertebrate Paleontology pt U. Echinodermata 3 vol. 2 pp. U492–U523. The Geological Society of America, Inc., and The University of Kansas Press.
[SG93] Simms, M. J., A. S. Gale, P. Gilliland, E. P. F. Rose & G. D. Sevastopulo. 1993. Echinodermata. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 491–528. Chapman & Hall: London.