pteropod

Pteropoda

The name 'Pteropoda' is an obsolete (but quite convenient) indication for holoplanktonic molluscs belonging to the orders of Thecosomata and Gymnosomata. The species have in common that the original foot has developed into a pair of 'wings' (parapodia), increasing the animals' capacity of buoyancy and locomotion.

The various lower taxonomic units are characterised by rather specialised reproductive and feeding mechanisms, and anatomical structures, such as the mantle appendages in the Euthecosomata, or the 'hooks' in the Gymnosomata. This is not the place to go deeper into these anatomical features. Quite a lot of information on these subjects, also for other holoplanktonic molluscs, and inclusive of beautiful illustrations of the living animals, can be found in Lalli & Gilmer (1989).

Species of which the adult individuals possess shells are found only in the Thecosomata. The order Thecosomata is subdivided into two suborders, Euthecosomata and Pseudothecosomata. The Euthecosomata all have shells, whereas in the Pseudothecosomata some groups have shells, some are naked, and some have developed cartilaginous so-called 'pseudo-conchs'. Shells are either sinistral or bilaterally symmetrical. Basic information on systematics, anatomy and biogeography is brought together in van der Spoel (1967) and van der Spoel (1976).

In the Gymnosomata embryonic shells are only present during the first days after hatching after which they are shed. They can be found in fossil and recent bottom sediments. The oldest specimens known to me (still unpublished) are of Miocene age. They belong to various genera but are difficult to identify as even the embryonic shells of the recent species are barely known. Their study is only possible by means of Stereo Electroscan because of their very small size of 200 microns and less. Info on systematics and anatomy is found e.g. in van der Spoel (1976).

Some typical representatives of the various groups are illustrated here (drawings by the present author, SEM micrographs by Jeroen Goud of the National Museum of Natural History, Leiden, The Netherlands) to give an idea of the morphologies involved:

Thecosomata, Euthecosomata, Limacinoidea

Family Limacinidae

Heliconoides mercinensis (Watelet & Lefèvre, 1880)

Fur (Denmark, Jylland), beach at Knuden Cliff (calcitic internal moulds)
Palaeocene, Thanetian, Mo-Clay Formation, 'Cement-stone, C-Block'
Coll. Fur Museum, reg. nr 1091 FUM (not published)

Magnification c. 4 x

Heliconoides tertiaria (Tate, 1887)

Miocene (Langhian ?), of Sannicola Varano
(Italy, Gargano) (phosphatic internal mould)

2 specimens in the RGM collection (unregistered, not published)

bar length is 1/10 mm
upper = apical view, lower = frontal view

Cavolinioidea

Family Creseidae

Creseis sp.

Miocene (Langhian), Upper Globigerina Limestone Formation)
from Mdina (Malta), phosphatic internal mould

RGM collection (unregistered, not published)

bar length is 1/10 mm

Praehyalocylis laxeannulatus (Ludwig, 1864)

Westeregeln near Magdeburg (Germany, Sachsen-Anhalt), pyritic internal mould with shell preserved
Oligocene (Rupelian), Fischschiefer
Museum für Naturkunde der Humboldt Universität (Berlin, Germany),
unregistered (not published)

bar length = 1 mm

Styliola subula (Quoy & Gaimard, 1827), neotype

Tydeman Selvagens-Canary Islands Expedition, 1980. CANCAP-IV Sta. 4.117, Canary Islands, S of Palma, 28°26' N, 17°51' W, depth 503 m, gravel, sand and shells, van Veen grab, 28 May 1980.

Frontal view and protoconch, height of specimen = 7,5 mm

National Museum of Natural History (Leiden, The Netherlands, NNM 57267
Published in Janssen (1999a, p. 19, text-fig. 3)

Tibiella annulata Garvie, in Hodgkinson, Garvie & Bé, 1992, paratype (apertural flange missing)

McBrides Place, Texas (U.S.A.) (= locality 10 in Hodgkinson et al., 1992)

Eocene, Lutetian, Weches Formation, Viesca Member

Coll. C. Garvie, reg, nr 3937
Bar length = 1 mm (frontal, lateral and apertural views)

Family Cuvierinidae

Cuvierina (Urceolaria) inflata (Bellardi, 1873)

Poggio Musenna (Italy, Sicily, Ragusa) , limonitic internal mould

Miocene (Tortonian), Tellaro Formation
Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 397.507 (right hand figure, ventral view), RGM 397.508 (three figures on the left, apertural, ventral and lateral views), bar-length = 1 mm
Published in Janssen (1999a, figs. 8a-c, 9)

Cuvierina (Cuvierina) jagti A.W. Janssen, 1995

Poggio Musenna (Italy, Sicily, Ragusa) , limonitic internal mould

Miocene (Tortonian), Tellaro Formation

Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 397.510 (apertural, ventral and lateral views), bar-length = 1 mm

Published in Janssen (1999a, fig. 10a-c)

Cuvierina (Cuvierina) paronai Checchia-Rispoli, 1921

Poggio Musenna (Italy, Sicily, Ragusa) , limonitic internal mould

Miocene (Tortonian), Tellaro Formation

Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 397.509 (apertural, ventral and lateral views), bar-length = 1 mm

Published in Janssen (1999a, fig. 11a-c)

Family Clioidae

Clio (Bellardiclio) carinata (Audenino, 1897)

Çörten (Turkey, Adana)
Miocene, 'Vindobonian', brownish-grey clays

Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 393.111 (leg. A.W. Janssen, 11 May 1990)

Published Janssen (1995, pl. 6, fig. 1)

bar length = 1 mm

Clio (Balantium) collina Janssen & Zorn, 2001

Colli Torinese (? Termo-Fourà) (Italy, Piemonte)
Miocene, ? Burdigalian/Early Langhian (? Termô-Fôrà 'conglomerati')
Coll. Dipartimento di Scienze della Terra, Torino, reg. nr BS 007.05.001 (Bellardi & Sacco collection).
Published in Bellardi (1873, pl.3, fig. 10, as Balantium pedemontanum non Mayer), Janssen (1995, pl. 6, fig. 2a-d, as Clio sp. ? an C. lavayssei non Rutsch) and Janssen & Zorn (2001, fig. 1a-d)
Bar length = 1 mm (apertural, dorsal, ventral and lateral views)

Clio (Balantium) lavayssei Rutsch, 1934, holotype

Basin Hill Reserve (Trinidad, Central Range)
Miocene (St. Croix Beds)
Coll. Naturhistorisches Museum, Basel (Switzerland), reg. nr NMB H 11358 (6/4599), leg. H. Rohr, 2 May 1931.
Published in Rutsch (1934, fig. 4) and Janssen & Zorn (2001, fig. 2a-b).
Bar length = 1 mm (schematic transverse section and internal mould in external mould of ventral side)

Family Cavoliniidae

Cavolinia bituminata (Beets, 1953), holotype

Waisioe, Buton (Indonesia, Sulawesi)
Miocene (Tortonian-Messinian)
Coll. Naturhistorisches Museum, Basel (Switzerland), reg. nr NMB H 17876 (leg. F. Weber)
Published in Janssen (1999b, pl. 1, figs.2a-d), dorsal, lateral and ventral view (upper row) respectively; lower figures: details of closing mechanism
Bar length upper three figures = 1 mm; lower two figures c. x 75

Cavolinia grandis (Bellardi, 1873)

McKay Creek, Kaniere Valley (New Zealand, South Island, Westcoast)
Pliocene, Waipipian, Bluebottom Formation
Coll. Otago University, Geology Department, Dunedin, New Zealand, reg. OU11913 (leg. C.S. Almond, 1976)
Published in Janssen (2000: 46, figs 10a-b)
bar-length = 1 mm

Cavolinia mexicana (Collins, 1934)

Waisioe, Buton (Indonesia, Sulawesi)
Miocene (Tortonian-Messinian)
Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nrs RGM 42.513 (upper specimen), RGM 231.432 (K. Martin collection). Holotype (upper) and paratype (lower) of Cavolina cranioides Beets, 1943
Bar-length = 1 mm
Published in Janssen (1999b, pl. 1, figs.3a-c, 4a-c)

Diacria mbaensis Ladd, 1934
Holotype (right) and paratype (left)
2 1/4 miles S of Na Rarawai, Ladd Sta. 306, Viti Levu, Fiji. Miocene (Tortonian-Messinian). Coll. Bernice P. Bishop Museum, Honolulu (Hawaii, USA), reg. nrs BPBM 208244-5).

Published in Ladd (1934, figs. 6, 7) and Janssen (1999b, pl. 2, figs. 13a-b, 14a-b).

Diacria sangiorgii Scarsella, 1934

Poggio Musenna (Italy, Sicily, Ragusa) , limonitic internal mould
Miocene (Tortonian), Tellaro Formation
Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 397.511 (dorsal, left lateral and ventral views), bar-length = 1 mm
Published in Janssen (1999a, fig. 6a-c)

Edithinella caribbeana (Collins, 1934)

Poggio Musenna (Italy, Sicily, Ragusa), limonitic internal mould
Miocene (Tortonian), Tellaro Formation

Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 397.512 (ventral, left lateral and dorsal views), bar-length = 1 mm

Published in Janssen (1999a, fig. 12a-c)

Vaginella austriaca Kittl, 1886

Gram, Enderupskov (Denmark, Jylland), gravelpit, numerous specimens in aragonite decalcified, reddish-brown sandstone
Miocene, Hemmoorian (reworked from Arnum Formation in fluvio-glacial deposits)
Coll. National Museum of Natural History, Leiden (The Netherlands), reg. nr RGM 429.485 (leg. M.S. Nielsen, don. K.I. Schnetler) (not published), magnification c. 1,5 x.

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Thecosomata, Pseudothecosomata, Peraclidoidea

Family Peraclidae

Peraclis lata (Krach, 1979), lectotype