291-2 Jaws in a tropical paradise: first report of Late Cretaceous cephalopod jaws from the Caribbean

Session: Cephalopods Through Time: Insights into Evolution, Ecology, and Environmental Reconstruction

Presenting Author:

Esteban Lopez-Murillo

Authors:

Lopez-Murillo, Esteban David¹, Myers, Corinne², Mackey, Tyler James³, Allmon, Warren D.⁴, Ramirez, Thais D.⁵, Cárdenes-Sandí, Guaria⁶, Sandoval, María Isabel⁷, Landman, Neil H.⁸

(1) University of New Mexico, Earth and Planetary Sciences, Albuquerque, NM, USA, (2) University of New Mexico, Earth and Planetary Sciences, Albuquerque, NM, USA, (3) University of New Mexico, Earth and Planetary Sciences, Albuquerque, NM, USA, (4) Paleontological Research Institution, Ithaca, NY, USA, (5) Universidad de Costa Rica, Escuela Centroamericana de Geología, San José, Costa Rica, (6) Universidad de Costa Rica, Escuela Centroamericana de Geología, San José, Costa Rica, (7) Universidad de Costa Rica, Escuela Centroamericana de Geología, San José, Costa Rica, (8) American Museum of Natl. His.Paleontology, New York, NY, USA,

Abstract:

Recent studies from Late Cretaceous sedimentary rocks from Costa Rica have described abundant late Campanian-early Maastrichtian molluscan faunas (bivalves, gastropods, cephalopods). One unit that has very well-preserved molluscan fauna is the San Buenaventura Formation, consisting of open shelf deposits of latest Campanian-earliest Maastrichtian age (74 – 70 Ma), visible across eight sites in northwestern Costa Rica. The San Buenaventura Formation has abundant ammonite fossils within two beds that equate to the latest Campanian time interval, containing index taxa Pseudokossmaticeras brandti (Redtenbacher, 1873) and Baculites leopoliensis Nowak, 1908, overlain by lowermost Maastrichtian beds marked by Pachydiscus neubergicus (von Hauer, 1858). At the Coyolito locality within the uppermost Campanian level, six cephalopod jaws were found, representing the first cephalopod jaws described from the Upper Cretaceous Caribbean region. The morphology of these jaw samples suggest that some belonged to scaphitids, baculitids, and possibly belemnitids. The jaws are recrystallized to black calcite, but preserve primary structures, including overall shape and ribbing, which allows them to be identified. They occur in pairs. Moreover, these jaws provide information about the paleoecology of Tethyan ammonites (e.g., feeding habits with comparison with North American specimens), which is understudied relative to the jaws of ammonites from the Gulf/Atlantic Coastal Plains and the Western Interior of North America. The possible presence of scaphitids and belemnitids in the Caribbean Tethys is of great paleobiogeographic importance, since these groups are not common in the tropical Mediterranean Tethys, but are common in the temperate regions of North America. Further studies into cephalopod jaws from Cuba, Costa Rica, and Jamaica during the late Campanian-Maastrichtian will improve our understanding of ammonite jaw diversity and paleoecology just before the Cretaceous-Paleogene extinction event, of which the Caribbean region is ground zero.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-6590

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