prosiphonn.
/prəʊˈsʌɪfn/, U.S. /proʊˈsaɪf(ə)n/ Palaeontology.
The primitive siphon in an embryonic ammonoid, consisting of a kind of ligament attached to the protoconch.
ΚΠ
1890 Cent. Dict. Prosiphon, the predecessor of the protosiphon in the Ammonites, consisting of a kind of ligament united to the wall of the initial chamber.
1895 Cambr. Nat. Hist. III. 387 The protoconch is present, and contains a prosiphon.
1925 P. Radin & V. C. C. Collum tr. E. Perrier Earth before Hist. iii. i. 225 In the inner shell of the Spirulidæ..the siphuncle goes through the last partition and terminates in a small ovoid sac, the ovisac, which is attached to the top of the shell by a ligament, the prosiphon.
1943 Jrnl. Palaeontol. 17 5/2 The prosiphon..appears as a slightly curved fine line extending obliquely from the adapical end of the caecum to the inner wall of the protoconch.
1985 Paleobiology 11 311/1 Their early whorls consist of such common structural elements as protoconch and outer shell walls, prosiphon and its accessory ones (secondary prosiphons), caecum, prosepta, flange, septa, and siphuncular tube.
Derivatives
proˈsiphonal adj. rare
ΚΠ
1890 Cent. Dict. Prosiphonal, of or pertaining to the prosiphon.
1965 Philos. Trans. (Royal Soc.) B. 250 88 Caecal and prosiphonal structures have been described for numerous post-Devonian ammonoids.
This entry has been updated (OED Third Edition, June 2007; most recently modified version published online March 2022).
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n.1890