The Echinoid Directory

Phymosoma Haime, in d'Archiac & Haime 1853, p. 197

[=Cyphosoma Agassiz, 1838, p. 4, non Mannerheim, 1837; =Koenigia Pomel, 1883, p. 90 (objective); =Phymatosoma Bather, in Lambert & Thiery 1910, p. 223 (objective)]

Diagnostic Features	Test wheel-shaped, depressed above and below. Apical disc large, pentagonal, up to half test diameter in length, extending slightly into posterior interambulacrum. Plates not bound to corona, always missing; presumed monocyclic. Ambulacra straight; plating polygeminate (5-6 elelments to a plate), compounded in phymosomatid style. Pore-pairs undifferentiated; at the ambitus forming arcs but biserially arranged aborally and expanded into phyllodes adorally. A single primary tubercle to each compound plate; additional small secondaries and granules forming zig-zag line down perradius. Interambulacral plates wider than tall; with a single primary tubercle, positioned centrally plus a secondary tubercle almost as large to the adradial side on ambital and adapical plates, this tubercle diminishing in size adapically. On oral surface an adradial band of much smaller secondary tubercles. Scattered secondaries and granules interradially at the ambitus, but a well developed naked interradial zone present aborally, expanding towards the apex. Tubercles imperforate and crenulate. Peristome small, circular, slightly sunken, with small, but clearly defined buccal notches with thickened lip; no tag. No sphaeridial pits; no basicoronal interambulacral plate. Spines straight, tapering distally, moderately robust, a little less than the test diameter at their longest. Shaft smooth, with cortex. Lantern stirodont, teeth keeled.
Distribution	Middle Jurassic (Callovian) to Palaeocene, Europe, Former Soviet Union, North & South America, Africa.
Name gender	neuter
Type	Cidaris koenigi Mantell, 1822, p. 189, by subsequent designation of Lambert & Thiery, 1910, p. 223.
Species Included	P. koenigi (Mantell, 1822); Turonian-Campanian, Europe. P. peroni (Cotteau, 1864); Neocomian, Aptian, Europe. P. calloviense (Cotteau); Callovian, France. P. texanum (Roemer, 1836); Cenomanian, USA P. loryi (Gras, 1852); Valanginian-Aptian, Europe. P. paynei Smith & Wright, 1996; Albian, England. P. quinquangulare Schluter, 1881; Turonian, Europe. P. granulosum (Goldfuss, 1829); Campanian-Danian, Europe. P. ravni Schlüter, Kutscher, Smith, Jagt & Lees, 2012; Campanian-Maastrichtian, UK & Germany.
Classification and/or Status	Euechinoidea, Phymosomatoida, Phymosomatidae. Monophyletic.
Remarks	Closest to Cosmocyphus, but with pore-pairs expanded adorally to form phyllodes and without the deeply sunken peristome. d'Archiac, E. & Haime, J. 1853. Description des animaux fossiles du groupe Nummulitique de l’Inde, 373 pp., 36 pls. Gide and. Baudry, Paris. Smith, A. B. & Wright, C. W. 1996. British Cretaceous Echinoids. Part 4, Stirodonta 3 (Phymosomatidae, Pseudodiadematidae) and Camarodonta. Monograph of the Palaeontographical Society (publication no. 602, part of vol. 150), 268-341, pls 93-114.