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Figured above is the holotype of Gisortia
gisortiana pterophora Schilder, 1927,
from the Middle Eocene of northern France;
length 260 mm. (over 10 inches).
The largest living cowry is Macrocypraea cervus LINNAEUS from Florida, which according to PRESBREY (1913) grows up to 7
inches (i.e. 178 mm.); however, the largest specimen measured by the writer in forty years investigations is "only" 157 mm.
long (British Museum). The second rank is occupied by Cypraea tigris LINNAEUS, the Philippines race of which, named
schilderiana CATE, attains in deep water 147 mm. (KAY 1961). The third rank must be attributed to Chelycypraea testudinaria
LINNAEUS: the largest specimen of its western race ingens SCHILDER & SCHILDER, preserved in coll. DAUTZENBERG, is not 142 mm.
long (as indicated by SCHILDER 1929), but only 140 mm. (SCHILDER & SCHILDER 1952). It may be observed, that these three giant
species among living Cypraeidae belong to the subfamily Cypraeinae, while the largest Nariinae and Cypraeovulinae are
distinctly smaller.
Some fossil cowries, however, attained even larger dimensions, in fact more than double the length of the largest living
species named above! There is a subfamily Gisortiinae which tends to gigantism, as well as to a reduction in the
denticulation of the lips. They descended from the subfamily Cypraeorbinae which flourished from Cretaceous times to Eocene,
and of which very few species have survived as relics to recent times. The Gisortiinae evidently originated in India in the
Paleocene (about 65 million years ago), flourished during the Lower and Middle Eocene near the Eocene equator from West
America to Europe and India and as far as Taiwan. Then suddenly they became extinct, with the few exceptions, which survived
up to the upper Eocene (about 40 million years ago). No species has been detected in Oligocene beds. During these 25 million
years a general increase in size can be observed, in a hyperbolic way, i.e. the enlargement became gradually faster and
faster -- till the size exceeded the natural limits of existence, and the Gisortiinae became extinct. But let us hope that
one day a living relic of this subfamily may be found in deep water, which has yielded, in these last decennaries, so many
surprising discoveries.
The species was established by Duclos in 1833 (Mag. de Zool., Mollusqu., Paris), and illustrated on page 26. Monographers of
the genus Cypraea, such as Reeve, Sowerby, Roberts, and Hidalgo, erroneously recorded the species from various Indo-Pacific
localities, with the "Philippine Islands" being the favourite locality quoted; Hidalgo even reported it from the "Sandwich
Islands". Most authors treated C. esontropia as a valid species, and the Schilders, in all their papers, restricted the
distribution of the species to Mauritius.
Doubt about the species taxonomic status and distributional range, was raised by Dr. Verdcourt in his monograph on East
African Cowries (Journ. E. Afr. Nat. Hist. Soc., 23(7):282), who suggested that C. esontropia may be no more than a variety
of C. cribraria Linnaeus. A specimen of C. cribraria, with small, pale wine-coloured spots on the labial margin, collected by
Penn at Shanzu, Kenya, was thought to be C. esontropia by Mr. W. Old, Jr. (in Verdcourt).
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