Abb. 306. Bau und Struktur der Aptychen. A, B: Unterkiefer (Anaptychus) von Psiloceras ( ~ n t . - ~ u ~ ~ ) , X 7,5; C-G: ~ t r u k t u r der A~tychen, C, D: Lamellaptychus fJura- Kreide), X 0,5, X 7.5, E-G: Laevaptycbus (Ob.- Jura), x 0,4, X 5, X 0,8; H-M: Anaptychen (H, I) und Aptychen (K-M) in der Wohnkammer von

Abb. 305. Kiefer und Radula bei Ammonoideen. A: Lage der Kiefer und der Radula im Längsschnitt eines Ammonoideen, H-L: Die Elemente sind so vor die Gehä~sernündun~ gerutscht, daß dies als ,Verschlußstel- Ammoniten der Gattung Eleganticeras (Unt. -Jura), X 1,5; B: Rekonstmktion von Psiloceras (Unt.-Jura, X 0,5) lungU erscheint, M: „NormallageU arn Grund der Wohnkammer; H: Lytoceras uura - Kreide), X 0,25; mit der vermuteten Lage der Kiefer; C-E: Kiefer von Ammoniten, C: Unt.-Jura, X 3, D: Um.-Jura, X 0,751 - 1: Arietites (Um.-Jura), X 0,25; K: Ob.-Devon, X 0,5; L, M: Ob.-Jura, X 0,25, X 0,3. Nach W. J. AR^^^^, E: Ob.-Kreide, X 2,5; F-I: Radula der Ammonoideen, F: Karbon, X 4, G: Unt.-Jura, X 10, H: Unt.-Jura, B. KUMMEL a C. W. WRIGHT, U. LEHMANN und 0. H. SCHINDEWOLF. X 35, I: Unt.-Jura, X 25. Nach U. LEHMANN und K. TANABE et al. xt'~9lel- ~991

z;eglb 499q

I m8.31 Ufe attitudes and buoyancy of the ammonites: (a) supposed life orientaüons of a selection of ammonlte gen era; (b) relatlonshlp of some ammonlte morphotypes to water d e m and the development of anoxla.

algal mat + ostracods, gastropods, etc.

veriical migratlon

--

egg '3 juvenile

adult . .

intemal or extemal brooding

- 1 1 1 1 , r r / / / / / / / / / / , '

FIGURE 16. Three life-cycle scenarios of dimorphic ammonoid species: nektic with benthic eggs, planktic with planktic eggs, and planktic with pseudoplanktic eggs laid in floating algal mats. d c l ~ ~ & ~ & r n 4996

FIGURE 4. Significance of the main types of species structure in Jurassic ammonoids related to dimorphism, with an indication of their diagnostic features (striped bars indicate a level of uncertainty) and illustrations of some selected characteristic examples: 1 M and m, Cardioceras Neumayr and Uhlig. 1881; 2 M and m. Kosmoceras Waagen, 1869; 3 M and m. Hildaites Buckman, 1921; 4 M and m, MacrocephalitesZittel. 1884; 5 M and m. Phricodoceras Hyatt, 1900; 6 Ma and 6 m, Aegoceras Waagen, 1869; 6 Mß, Liparoceras Hyatt, 1867; 6 My. Becheicemsllueman. 1918; Ta, Tarornelliceras Del Campana, 1904; 70, Crenicems Munier-Chalmas, 1892; 8, Cyrnbites Neumayr, 1878; 9. Gemmellaroceras Hyatt, 1900; 10, Prodactylioceras Spath, 1923. The types of species structure (A-D) and the diagnostic features for dimorphism (1-4) are discussed in the texte p a v i s e4 a(. 49 96 ( 9 a ~ c l )

GURE 14. Stylized Panorama of Jurassic-Cretaceous ammonoid habitats (with substantial modifications of Westermann, 1990, Fig. 7). As for the iassic (Fig. 13). present interpretations suggest more pelagic. often shallower habitats and more frequent vertical migration. Ammonitina: 1, F -1toceras; 2, Arietites; 3, Perisphinctes; 4. Harpocems: 5, Sphaeroceros: 6 . Oxycerites; 7, Barremites. Ancyloceratina: 8. Turrilites; 9. Baculites; 10. 2 .aphites: 11. Ancylocems; 12, Nipponites; 13. Didymocems; 14. Criocemtitss: 15. hbeceras; 16, Glyptoxoceras: 17. Hamulina; 18, Anisoceras; 19. 3 eudoxybelocems. Phylloceratina: 20. Holcophyllocems: 2 1, Phyllocems. Ly toceratina: 22, Lyloceras. +

cn d t ? & . - ~ a w w 4996

->,? swimming . o eggs (in gel)

+ + postmodern drift + sinking 3 juvenile

FIGURE 11. Epeiric basin, black-shale facies. Possible Scenario of the Early Jurassic Posidonia ShalelJet Rock of northwest Europe. Surface waters were partly brackish, and deeper waters were dysaerobic to anaerohic. changing cyclically (poikiloaerobic). Arnmonitina: 1, Dactyliocems (planktic drifter); 2 , Harpoceras; 3, Hildoceras (predators). Coleoidea: 4. squid oi. belemnite. Egg masses in gel and juveniles wem also present in lower waters and periodically were killed by rising anoxia: some examples of postmortem sinking and drift are indicated. L&x&ccca„ 4996

Wocklumeria

Clymenia

Goniat ites

Beneckeia

Cerat ites

Ob. Devon I

Ob. Devon V1

Ob. Devon V- V1

Unt. Karbon I

Unt. Karbon

untere - mittlere Trias (Ob. Buntsandstein - Unt. Muschelkalk)

mittlere Trias (Ob. Muschelkalk)

Lias - Ob. Kreide

Psiloceras

Schlotheimia

Arietitis

Amdtheur

Dactylioceras

Lias

Lias

Lias

höherer Lias

Dogger (unteres Callov)

Ob. Kreide (Campan - Maastricht) '

Malm

Unt. Kreide

Unt. Kreide (Alb) - Ob. Kreide (Cenoman)

Unt. Kreide (Alb) - Ob. Kreide (Carnpan)

Ob. Kreide