prothecan.
/prəʊˈθiːkə/, U.S. /proʊˈθikə/ Zoology and Palaeontology.
An enclosing structure or sheath, or a part of one, which is primary in nature or basal in position (cf. theca n. 3a); esp. (a) (in a coral polyp) the theca in its initial or rudimentary form (rare); (b) (in a foraminiferan of the superfamily Fusulinacea) an unmodified primary wall; (c) (in a graptolite of the order Graptoloidea) the basal part of a theca, attached to the sicula. Cf. prototheca n. at proto- comb. form 2a.
ΘΚΠ
the world > animals > invertebrates > protozoa > class Sarcodina > order Rhizopoda > [noun] > suborder Foraminifera > member of > primary wall
protheca1907
1907 Science 10 May 734/1 This paper considers..Streptelasma and allied genera of the rugose corals and describes the protheca as observed in these genera.
1937 L. G. Henbest in Jrnl. Palaeontol. 11 212/1 I am applying the term epitheca to all secondary shell material [of Fusulina] such as tectorium and chomata, and the term protheca to the primary wall-layers.
1940 Chambers's Techn. Dict. 680/1 Protheca, the calyx rudiment in coral formation.
1958 Philos. Trans. (Royal Soc.) B. 241 495 The first theca [in Monograptus separatus]..begins with a slowly widening protheca; near the tip of the sicula the rate of prothecal widening increases.
1972 Jrnl. Paleontol. 46 925/1 A second table summarizes the regression analyses..between radius vector and protheca thickness [sc. in fusulinids].
1993 E. N. K. Clarkson Invertebr. Palaeontol. & Evol. (ed. 3) x. 311/2 Each theca [in Saetograptus chimaera] has two parts: the protheca, proximal to the nema, through which the common canal runs; and a metatheca, which is the external part.
This is a new entry (OED Third Edition, September 2007; most recently modified version published online March 2022).
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n.1907