The Echinoid Directory

Jacksonaster Lambert in Lambert & Thiery, 1914, p. 313

Diagnostic Features	Test ovate to pentagonal in outline; margin variable in thickness. Apical disc with 5 gonopores; hydropores in sinuous groove. Internal buttressing complex with peripheral concentric partitions. Petals well developed; closing distally. Basicoronal plates strongly stellate in arrangement, with projecting ambulacral plates. First pair of interambulacral plates greatly elongate. Periproct oral and transversely elongate; close to the posterior margin; opening between first and second paired post-basicoronal plates. Food grooves prominent orally; straight and simple.
Distribution	Miocene to Recent of the Indo-Pacific.
Name gender	masculine
Type	Laganum depressum L. Agassiz, 1841, by subsequent designation of Lambert, 1915, p. 28 (The earlier designation of type as Jacksonaster conchatus (McClelland, 1840) by Lambert & Thiery, 1914, p. 313 is based on an indeterminate specimen that is probably a Laganum depressum L. Agassiz, 1841 - See Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen, p. 320).
Species Included	J. depressum (Agassiz, 1841); Upper Miocene-Recent, Indo-West Pacific. J. fudsiyama (Doderlein, 1885); Miocene- Recent, Indo West Pacific. J. pachycraspedum Nisiyama, 1968; Miocene, Japan. Most of the species listed by Mortensen (1948) under Laganum.
Classification and/or Status	Clypeasteroida; Scutellina; Laganiformes; Laganidae; Laganinae. Presumed monophyletic.
Remarks	The five gonopores distinguish Jacksonaster from Peronella and the much longer petals distinguish Jacksonaster from Hupea. Laganum is closely similar, Jacksonaster differing primarily in having the first pair of post-basicoronal interambulacral plates greatly elongate so that the periproct opens closer to the posterior margin. Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen. Durham, J. W. 1955. Classification of clypeasteroid echinoids. University of California Publications in Geological Sciences 31(4), 73-198. Lambert, J. & Thiéry, P. 1909-1925. Essai de Nomenclature Raisonnée des Echinides. L. Ferrière, Chaumont, fasc. 1: i-iii, 1-80, pls. 1-2 (March 1909); fasc. 2: 81-160, pls. 3-4 (July 1910); fasc. 3: 161-240, pls. 5-6 (May 1911); fasc. 4: 241-320, pls. 7-8 (March 1914); fasc. 5: 321-384, pl. 9 (Sept. 1921); fasc. 6-7: 385-512 , pls. 10-11, 14 (Dec. 1924); fasc. 7-8: 513-607, pls. 12, 13, 15 (Feb. 1925) pp. Nisiyama, S. 1968. The echinoid fauna from Japan and adjacent regions part II. Palaeontological Society of Japan Special Papers 13, 1-491, pls 1-30.