Contributed by Andreas Kroh, February 2010
[Plesiosalenia Valette, 1906, p. 276 ]
|Diagnostic Features||Acrosaleniids with
|Distribution||Middle to Late Jurassic (Bathonian to Tithonian), England and France.|
|Type||Acrosalenia gauthieri Cotteau, 1879, by subsequent designation of Fell & Pawson 1966, p. U376.
Valette originally included the following species: Acrosalenia bradfordensis Rigaux. Acrosalenia gauthieri Cotteau. Acrosalenia lamberti Cotteau. Acrosalenia libyca Peron & Gauthier. Acrosalenia pulchella Cotteau. Acrosalenia lowei Wright. Diadema lamarcki Desmoulins. Perisalenia cotteaui Valette, 1906.
|Classification and/or Status||Calycina, Salenioida (stem group)
|Remarks||Originally established by Valette (1906) for acrosaleniids with reduced or lacking primary tubercles on the adapical ambulacral plates.
The apical disc structure amongst acrosaleniids and primitive calycines offers a clear means for separating clades. Acrosalenia has a hemicyclic apical disc with the anterior three genital plates in broad contact, and with one large suranal plate clearly differentiated. Wrightechinus has a monocyclic apical disc whose plates are only loosely bound to the corona, and with genital plates not much larger than ocular plates. In Milnia the periproct is strongly diplaced to the posterior and genital plate 5 is much reduced. In Wrightechinus, a large pavement of tessellated periproctal plates lies inside the ring of ocular and genital plates. In Perisalenia, the apical disc plating is hemicyclic, with narrow contact maintained between the anterior genital plates and with a pavement of tessellated periproctal plates. Monodiadema differs from Perisalenia in having small ambulacral primary tubercles that are hardly differentiated from granulation, even adorally.
Vadet (2005) separated Perisalenia from Plesiosalenia based on whether adapical tubercles in interambulacral zones were more or less noticeably reduced in size. While this may be useful at species level, the more fundamental differences in apical disc structure offer a more secure basis for the higher classification of this group.
Smith, A. B. 2016. British Jurassic regular echinoids. Part 2 Carinacea. Monographs of the Palaeontographical Society (no. 646), pp. 69-176, pls 42-82.
Vadet, A. 2005. Echinides fossiles du Boulonnais du Bajocien au Tithonien: Echinothurioidea, Pedinoidea, Orthopsida, Hemicidaroida. Annales de la Societe d'Histoire naturelle du Boulonnais 4(2), 1-108.
Valette, A. 1906. Etude sur la formule porifere d'un certain nombre d'echinides reguliers. Bulletin de la Societe des Sciences Historiques et Naturelles de L'Yonne, 59 (1905): 271-311.