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PTEROPODA

PTEROPODA. GEOL 3213. Pteropoda – What are they?. Opisthobranch gastropods Nudibranchs =“Sea slugs” Heteropoda = some small shells Pteropods: Wing or paddle-like modification of foot Small shells : Aragonitic Cartilages

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PTEROPODA

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  1. PTEROPODA GEOL 3213

  2. Pteropoda – What are they? • Opisthobranch gastropods • Nudibranchs =“Sea slugs” • Heteropoda = some small shells • Pteropods: • Wing or paddle-like modification of foot • Small shells : • Aragonitic • Cartilages • Paleozoic Forms = other types of molluscs? Tentaculites, Hyalitha

  3. Classification of the Pteropoda • Phylum Mollusca • Class Gastropoda • Subclass Opisthobranchiata (secondarily untorted visceral mass) • Order Gymnosomata • Order Thecosomata • Suborder Pseudothecosomata • Family Peraclididae (shells not common in sediments) • Family Cymbulidae (no shell) • Suborder Euthecosomata • Family Limacinidae (shell common in sediments) • Family Cavoliniidae ( “ “ “ “ )

  4. Pteropod Soft Anatomy • Creseis • Limacinid • Cavoliniid

  5. Range Chart • Chart made for opisthobranch gastropods • We are considering pteropods & similar fossils: • Pteropods (K – Recent) • Heteropods (K – Recent) • Problematica resembling pteropods: • Cricoconarids (Ord. – Dev.) • Tentaculites • Styliolina • Other genera • Hyolithids (Camb. – Perm.) • Hyolitha

  6. Peraclididae • Shell: • Aragonite • Spiral • Extended columella • Reticulated surface sculpture is common • >100 m • Seldom found in sediments

  7. Cavioliniidae – Conical Genera • Styliola – circular aperture, dorsal longitudinal ridge • Hyalocylix – oval aperture, slight curve, transverse striations • Cuvierina – bottle-shaped, bulging middle, bean-shaped aperture • Creseis – circular cross section, long narrow cone Styliolasubula (Rec) Creseisacicula (Rec) Hyalocylixstriata (Rec) Cuvierinacolumnella (Rec) Creseisclava (Rec)

  8. Cavioliniidae - Clio • Cliocuspidata, 1st quarter of shell • C. pyramidata forma convexa • C. pyramidata forma pyramidata • Note bulbous molluscan protoconchs • Triangular shape • Maximum width at aperture

  9. Cavioliniidae – Cavolinia • Cavolinia (Miocene to Recent) • Uncoiled • Variable aperture • No thickened dorsal aperture Cavolinia

  10. Cavioliniidae – Diacria • Diacria • Uncoiled • Thickened dorsal aperture (This distinguishes it from Cavolinia.) Diacria (Rec)

  11. Cavioliniids - Vaginella • Vaginella (Late Cretaceous to Recent) • Compressed • Mid-region expanded • Lip-like compressed aperture

  12. Limacinidae - Limacina • Coiled shells • Limacina (Tertiary-Recent)

  13. Latitudinal Zonation? 1. Polar = Limacinahelicina Arctic & Antarctic 2. Subpolar = Limacinaretroversa 3. Subtropical = Styliolasubula 4. Cosmopolitan, warm waters = Diacriatrispinosa 5. Tropical = Limacinatrochiformis

  14. Limited Worldwide Pteropod Distribution Pattern • Note the concentration of pteropods in deep-sea calcareous oozes in tropical to subtropical belts • Note the concentration in Med., Red Sea, & E of Arab.P. • Why? • Aragonite CCD <2 000 m • Warm waters favour carbonate saturation

  15. Latitutinal Distribution of Recent Pteropoda • Is there a trend here? • What species have you found in your samples? • Are your samples from the tropics and/or subtropics?

  16. Evolution • Debate over evolutionary lineages, etc. • Ancestry is yet unknown • Pylogenetic relationships are not known with certainty • Possibly evolved from benthic, littoral gastropods & adapted to a pelagic mode of life • Thin, light shell = pelagic adaptation? • Coiled shells = primitive? • Uncoiling = advanced forms? • Bathypelagic (great depths) species of Limacina, Peraclis, & Clio = specialized (evolved?) characters in common

  17. End of File

  18. Limacina, Vaginella, & Cavolina

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