pro-ostracumn.
/(ˌ)prəʊˈɒstrək(ə)m/, U.S. /ˌproʊˈɑstrək(ə)m/ Palaeontology.
An anterior prolongation of the guard or rostrum of a belemnite or other fossil cephalopod, usually long and flat.
ΘΚΠ
the world > life > biology > organism > fossil > [noun] > particular parts of
ostracite1601
horse-head1708
nucleus1734
orthoceras1734
orthoceratite1734
alveolus1747
volutite1802
strombite1811
helicite1828
turbinite1828
phragmocone1843
pro-ostracum1864
orthoceratoid1885
nema1901
the world > animals > invertebrates > subkingdom Metazoa > grade Triploblastica or Coelomata > class Cephalopoda > [noun] > member of > parts of > anterior prolongation of fossil
pro-ostracum1864
1864 T. H. Huxley in Figures & Descr. Brit. Org. Remains (Mem. Geol. Surv. U.K.: Monogr.) II. 3 As the part which commonly goes by the name of ‘pen’ in the Belemnite..corresponds to only a part of the structure already known as the ‘pen’ in recent Cephalopoda, I shall endeavour to avoid ambiguity, by using for it the appellation of pro-ostracum.
1872 H. A. Nicholson Man. Palæontol. xxvi. 297 The form of the ‘pro-ostracum’ varies greatly in different cases, and it affords important characters in the discrimination of specific and generic forms in the Belemnitidæ.
1958 J. E. Morton Molluscs xi. 205 The belemnoid shell had three parts: a small chambered phragmocone corresponding to the whole nautiloid shell, a solidly calcified rostrum which is the cigar-shaped part usually found fossil, and, extending forward, a broad shield, the pro-ostracum.
1993 E. N. K. Clarkson Invertebr. Palaeontol. & Evol. (ed. 3) viii. 246/2 The third component of the belemnite shell is the pro-ostracum: a long, flat, expanded tongue projecting forwards and presumably covering the anterior part of the body.
Derivatives
pro-ˈostracal adj. rare of, relating to, or of the nature of a pro-ostracum.
ΚΠ
1890 Cent. Dict. Proöstracal, forming or formed by the proöstracum; of or pertaining to a proöstracum.
1944 Amer. Midland Naturalist 32 763 Unfortunately he does not discuss the validity of the proostracal features by which von Bulow-Trunner characterized the Aulacoceratidae.
This entry has been updated (OED Third Edition, June 2007; most recently modified version published online March 2022).
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n.1864