Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica
Two species of the heteromorph ammonite genus Diplomoceras Hyatt are described from the Upper Cretaceous of the James Ross–Seymour Islands area, Antarctica. The late Campanian–early Maastrichtian D. lambi Spath has a relatively high rib density, whereas D. maximum n. sp. has a lower rib density and...
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Language: | English |
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Cambridge University Press (CUP)
1989
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Online Access: | http://dx.doi.org/10.1017/s0022336000041251 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000041251 |
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crcambridgeupr:10.1017/s0022336000041251 2024-09-15T17:48:38+00:00 Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica Olivero, Eduardo B. Zinsmeister, William J. 1989 http://dx.doi.org/10.1017/s0022336000041251 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000041251 en eng Cambridge University Press (CUP) https://www.cambridge.org/core/terms Journal of Paleontology volume 63, issue 5, page 626-636 ISSN 0022-3360 1937-2337 journal-article 1989 crcambridgeupr https://doi.org/10.1017/s0022336000041251 2024-07-31T04:04:26Z Two species of the heteromorph ammonite genus Diplomoceras Hyatt are described from the Upper Cretaceous of the James Ross–Seymour Islands area, Antarctica. The late Campanian–early Maastrichtian D. lambi Spath has a relatively high rib density, whereas D. maximum n. sp. has a lower rib density and is known only from the uppermost Maastrichtian of the Lopez de Bertodano Formation on Seymour Island. Both species attain an exceptionally large size with the body chamber of D. maximum n. sp. attaining a length in excess of one meter. The structure of the shell wall in Diplomoceras is characterized by the thickening of the nacreous layer below the ribs. The shell thickening results in an inner flat surface and a smooth phragmocone. Reconstruction of the shell suggests at least four parallel shafts and three U-connectives. Estimates of the total density, center of buoyancy, and center of mass in this reconstructed shell indicate a slightly positive buoyant shell with a relatively unstable floating position. Article in Journal/Newspaper Antarc* Antarctica Seymour Island Cambridge University Press Journal of Paleontology 63 5 626 636 |
institution |
Open Polar |
collection |
Cambridge University Press |
op_collection_id |
crcambridgeupr |
language |
English |
description |
Two species of the heteromorph ammonite genus Diplomoceras Hyatt are described from the Upper Cretaceous of the James Ross–Seymour Islands area, Antarctica. The late Campanian–early Maastrichtian D. lambi Spath has a relatively high rib density, whereas D. maximum n. sp. has a lower rib density and is known only from the uppermost Maastrichtian of the Lopez de Bertodano Formation on Seymour Island. Both species attain an exceptionally large size with the body chamber of D. maximum n. sp. attaining a length in excess of one meter. The structure of the shell wall in Diplomoceras is characterized by the thickening of the nacreous layer below the ribs. The shell thickening results in an inner flat surface and a smooth phragmocone. Reconstruction of the shell suggests at least four parallel shafts and three U-connectives. Estimates of the total density, center of buoyancy, and center of mass in this reconstructed shell indicate a slightly positive buoyant shell with a relatively unstable floating position. |
format |
Article in Journal/Newspaper |
author |
Olivero, Eduardo B. Zinsmeister, William J. |
spellingShingle |
Olivero, Eduardo B. Zinsmeister, William J. Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica |
author_facet |
Olivero, Eduardo B. Zinsmeister, William J. |
author_sort |
Olivero, Eduardo B. |
title |
Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica |
title_short |
Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica |
title_full |
Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica |
title_fullStr |
Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica |
title_full_unstemmed |
Large heteromorph ammonites from the Upper Cretaceous of Seymour Island, Antarctica |
title_sort |
large heteromorph ammonites from the upper cretaceous of seymour island, antarctica |
publisher |
Cambridge University Press (CUP) |
publishDate |
1989 |
url |
http://dx.doi.org/10.1017/s0022336000041251 https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022336000041251 |
genre |
Antarc* Antarctica Seymour Island |
genre_facet |
Antarc* Antarctica Seymour Island |
op_source |
Journal of Paleontology volume 63, issue 5, page 626-636 ISSN 0022-3360 1937-2337 |
op_rights |
https://www.cambridge.org/core/terms |
op_doi |
https://doi.org/10.1017/s0022336000041251 |
container_title |
Journal of Paleontology |
container_volume |
63 |
container_issue |
5 |
container_start_page |
626 |
op_container_end_page |
636 |
_version_ |
1810290085618253824 |