by the Bartlett Expedition near the Azores at 37 13'18" N 28 lj'j, 30" W, proved that a related form existed during the Pleistocene ice ages.

Transcription

1 Zoologisch Museum Bulletin I 0 NIVERSITEIT VAN AMSTERDAM Vol. 6 No Cliobartlettin.sp., a fossil new to science closely related to Clio cuspid ata (Gastropoda, Thecosomata) S. van der Spoel Abstract by the Bartlett Expedition near the Azores at Clio bartletti n. sp. is described from a 37 3'8" N 28 lj'j, 30" W, proved that a related sediment sample containing a mixture of late form existed during the Pleistocene ice ages. Pleistocene and recent pelagic and benthic sediment. The is described sample and correlated As far as could be reconstructed fron the with climatic fluctuations using protoconch fossilized fragments, this taxon differs from size as a indicator. In all temperature probability the new species is an Alleröd fossil. the recent in the same characters as Linnaeus, 767, forma pyramidata, differs from the tropical forma lanceolata (Lesueur, 83). The shell is more (Bosc, 802) occupies a rather slender because of the less diverging lateral ribs, isolated position within the genus Clio., A and the protoconch is significantly larger than large shell aperture and long, laterally in. That this newly described projecting ribs are found only in this species. taxon belongs to a cold water fauna is proved Recent examination of a sediment sample, taken by other acconpanying cold water elements.

2 - 0 DESCRIPTION OF THE SAMPLE The sample, which was taken with a rock dredge, sediment, as recently grown Bryozoa colonies consisted of recently sedimented hyalinepteropod are commonly found on the brown concretions and and heteropod shells, whitish pteropod shells of moulds of shells. Vulcanic activities in the an older period, brown pteropod shells, and dark area of the Azores may have contributed to brown moulds of shells. Besides the brown shells, the disturbance and mixing of glacial sediments small particles of dark brown concretion of sand, It is evident that material of three periods Foraminifera, Bryozoa and shell fragments were is found mixed in the sample. These periods also found. Other groups represented were: non are indicated below as "recent", "subfossil" planktonic Mollusca, Crustacea and fish-otoliths. and "fossil". In table I the pteropod fauna of Secondary deposition must have occurred in the the sample is given. TABLE I. Pteropod fauna of Bartlett stat. 2. Number of specimens Protoconch volume in mrrr^ RECENT MATERIAL Y s N Limacina inflata 9 Styliola subula Diacria trispinosa 2 Cavolinia inflexa SUBFOSSIL MATERIAL Limacina retroversa f. balea 5 Styliola subula id. typical: lanceolata Clio bartletti n. sp Diacria trispinosa 2 FOSSIL MATERIAL Limacina inflata Limacina retroversa f. balea 20 Sty liola subula id. typical: lanceolata

3 DATING AND PALEOCLIMATE present material. The living species is not known from plankton samples in the area of The presence of Limacina retroversa at this the Azores, it occurs only more northwestwards latitude indicates that the subfossil and fossil of this area. Its presence in the non-recent material is of Pre-Boreal or older origin. Comparison with Mediterranean sediments described by Pastouret (970) shows that the subfossil material originates from the Alleröd fraction of the sample points to a climate colder than found in recent times. Styliola subula (Quoy & Gaimard, 827) shows the same distribution as L. i nflata which (presence of Diacria trispinosa), and that the fossil material may date from the Late Würm. makes its indicatory important. value for this area less The protoconch size of is a useful indicator for water temperatures (Diester- Linnaeus, 767 (fig- ~2, 8-9) is normally found in this area over Haass & Van der Spoel, in press). The values longer geological periods, and the protoconchae for the volume of the protoconchae in the are only of value for paleoclimatological recent Clio material are slightly higher than indications as discussed above. expected for the latitude of 37 N. The subfossil (Bosc, 902) (fig. 0), is a material consists of two types of shells, one common species for this area, ranging north with an average protoconch volume of 0.0 mm to about 60 N. Its absence in the subfossil and the other with an average of material and its presence in the fossil fraction which indicates that material of a colder and is, however, also an indication for the a warmer period is mixed. Associated with these specimens of, a species relatively cold climate during which the subfossil fraction has sedimented. In this cold closely resembling is found with period the next species may be considered to a volume protoconch of 0.08 The normal cuspidata at this latitude is volume for C so that the relative of C. cuspidata seems to be a cold water form, which lived together with the specimens of C. pyramidata replace C. cuspidata Clio bartletti n. sp., see below. (Rang, 827) shows the same distribution as L. inflata and S. subula and gives no special information on the sample. with the protoconch volume of 0.0 mm'. The The fragments of this species were too small fossil material shows relatively small volumes to identify it as to forma, but most probably for the protoconchae, reflecting the presence it will be the forma atlantica Van der Spoel, of the tropical forma lanceolata (protoconch volume inn') 970. Diacria trispinosa (De Blainville, 82) is together with a form transitional between the cold water forma pyramidata and the tropical forma (protoconch volume mm'). Probably comparable in distribution with the preceding species, though it penetrates still further north. Cavolinia inflexa (Lesueur, l8l3), only found the brown shells of this sample, "the fossils", as recent specimens, also gives no information are from the interstadial before the Dryas, whereas the "sub-fossil" fraction reflects a period concerning the age of the sediment. of strong warming up, mixed with cold water forms. Clio bartletti n. sp. (fig. 3-5) FAUNA OF THE SAMPLE Limacina inflata (d'qrbigny, 836) is a common Holotype: ZMUC one protcconch with part of teloconch. Paratypes: ZMUC two protoconohae species in this area ranging north to about 50 N. L. retroversa (Fleming, 823), (fig. 6-7) is with fragment of teleconch. Type locality: Bartlett Exped., Station 2; 37 3'W N 28 l4u'30" W, 480m depth, rock dredge, considered to be composed of two forms of which Description: Shell fragments, usually with the forma balea (Möller, 84) is found in the protoconchae, are smaller than 4 mm in length.

4 2 Holotype, 3.M mm long,.48 mm wide and ACKNOWLEDGEMENTS 2 rtm thick at the aperture. The pyramidal The author is very much indebted to Dr. J. Knudsen, shell is slightly bent ventrally, strongly Zoological Museum, University of Copenhagen (ZMUC ), compressed laterally, and provided with who carefully sorted out and provided thebartlett nearly straight lateral sides in ventral material. view. In the upper part of the fragments the LITERATURE first transversal ribs (3 in the holotype) are seen and the beginning of the lateral DIESTER-HAASS, L. & S. VAU DER SPOEL ( in press ). Late Pleistocene pteropod-rich sediment layer in the NE ribs. The whitish, somewhat glossy shells Atlantic and protoconch variation of show cracks, especially in the lower parts. The embryonic shell is relatively short but still of the droplet shape. Linnaeus, Palaeogeogr., palêocl im., palaeoecol., 25 pp. PASTOURET, L Etude sédimentologique et paléoclimatique de carottes prélevées enméditerranée orientale.-téthys 2 ( ): , fig. -lu,pl. -3. Dr. S. van der Spoel Institute of Taxonomic Zoology University of Amsterdam Plantage Middenlaan DC Amsterdam Received : 23 November 977 The Netherlands Mailing date: 5 August 978

5 Fig. -2 Linnaeus, 767, from the fossil fraction. : specimen seen from ventral side. 2: same specimen seen from aperture side. Fig. 3-5 Clio bartletti n. sp. 3: holotype seen from ventral side. 4: same specimen seen from lateral side. 5: same specimen seen from aperture side. Fig. 6-7 Limacina retroversa (Fleming, 823) from fossil fraction. Fig. 8-9 Linnaeus, 767, from recent fraction. 8: specimen seen from ventral side. 9: same specimen seen from lateral side. Fig. 0 (Bosc, 802) from fossil fraction seen from ventral side.