Revised descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990)
(Pl. 8u): GS3869, J41/f8539, Lorne, inland from Oamaru, Kaiatan (GNS)
Beu & Maxwell (1990): Chapter 8; p. 128; pl. 8 u.
Synonymy: Styliola annulata Tate 1887b, p. 195; Clio annulata; Clio rangiana (Tate, 1887) (not of Tate); Hyalocylis annulata, Beu & Maxwell 1990, p. 128
Classification: Cavoliniidae: Creseinae
Description: Rather large for family (length 15-35 mm), thin-shelled, tubular, of circular cross-section, slowly tapering, straight or gently curved. Apical details not known. Teleoconch sculpture of narrow, low, transverse ridges with wider interspaces, not quite perpendicular to axis of tube.
Comparison: Although this rather nondescript fossil superficially resembles some scaphopods (e.g. species of Fustiaria) it differs radically in having a very thin shell and except for its much larger size, it is very similar to the extant thecosome pteropod Hyalocylis striata (Rang, 1828). At most of the localities listed it is associated with undoubted pteropods, particularly species of Spiratella, and there can be little doubt that it too is a thecosome. H. striata sheds the early part of the shell, leaving a curved septum in the remaining portion, and it seems very likely that Praehyalocylis annulata had a similar habit, although none of the available specimens is sufficiently well preserved to be certain.
Praehyalocylis annulata is very similar to certain pteropods of Late Eocene and Oligocene age from Europe, Syria and USSR (e.g. H. maxima (Ludwig, 1864), H. cretacea (Blanckenhorn, 1890) and Praehyalocylis chivensis Korobkov & Makarova, 1962), and in view of the wide distribution of most modern thecosomes it is not unlikely that all of these names apply to a single widespread species. Although the genus-group name Praehyalocylis Korobkov & Marakova, 1962 is available for these outsize species, Beu & Maxwell (1990, p. 128) did not think there were any convincing criteria by which it can be differentiated from Hyalocylis. However, Janssen (1989, p. 28) recognised Praehyalocylis as a genus for these very large, early species in the evolution of the Hyalocylis group, and was followed by Maxwell (2009). Janssen (1989) redescribed Tate's types and defined the relationships of P. annulata and related species, recognising P. chivensis (Uzbekistan) as a synonym, and confirming its occurrence in New Zealand and the NE Pacific. H. cretacea turns out to be Miocene in age, and one of the descendents of P. annulata.
Distribution: Bortonian-Runangan; Middle-Late Eocene, Aldinga, South Australia (type); Waihao Greensand, Black Point, Bortons; Waiareka Volcanic Formation, Lorne; Kapua Tuff, Waihao River; Trig M, Totara; Bridge Point, Kakanui. Janssen (1989, pp. 28-32) discussed the characters, age and range of Praehyalocylis annulata in detail, and concluded that it occurs in Late Eocene rocks of New Zealand, southern Australia, NE Pacific and southern Uzbekistan (south of the Aral Sea; H. chivensis Korobkov & Makaraova, 1962); presumably originally cosmopolitan.
Cite this publication as: "A.G. Beu and J.I. Raine (2009). Revised
descriptions of New Zealand Cenozoic Mollusca from Beu and Maxwell (1990). GNS
Science miscellaneous series no. 27."
© GNS Science, 2009
(Included with a PDF facsimile file copy of New Zealand Geological Survey Paleontological Bulletin 58 in CD version from: Publications Officer, GNS Science, P.O. Box 30368 Lower Hutt, New Zealand)