PALEOECOLOGY AND TAPHONOMY OF NEOGENE CETACEANS: NEWPERSPECTIVES FROM THE SOUTHWESTERN ATLANTIC OCEAN

BUONO, MÓNICA R.; CUITIÑO, JOSÉ; VIGLINO, MARIANA; FLORENCIA PAOLUCCI; GATEÁN MAXILIMILIANO; FARRONI, NICOLÁS D.; BESSONE, SANTIAGO

SANTIAGO DE CHILE

Encuentro; 9th international meeting on the secondary adaptation of tetrapods to life in water; 2021

SECAD

PALEOECOLOGY AND TAPHONOMY OF NEOGENE CETACEANS: NEWPERSPECTIVES FROM THE SOUTHWESTERN ATLANTIC OCEANMÓNICA BUONO1, JOSÉ CUITIÑO1, MARIANA VIGLINO1, FLORENCIA PAOLUCCI2,MAXIMILIANO GAETÁN1, NICOLAS FARRONI1, SANTIAGO BESSONE11Instituto Patagónico de Geología y Paleontología, CCT CONICET-CENPAT, Bvd. Brown2915, 9120, Puerto Madryn, Argentina2CONICET, División Paleontología Vertebrados, Unidades de Investigación Anexo Museo,Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata, 60 y 122, 1900,La Plata, ArgentinaThe Neogene was a key time for cetaceans diversification and cosmopolitan distribution,mainly driven by important changes in global climate and ocean productivity. Neogenedeposits from the Atlantic and Pacific Oceans and the Mediterranean and North Seas providea rich cetacean fossil record from this critical evolutionary time. In the Southwestern AtlanticOcean, Miocene outcrops in Patagonia (Argentina) hold an important, albeit still poorlyknown, fossil record of modern lineages (= Neoceti) which in the last ten years have beencontinuously and exhaustively explored from a systematic, paleoecological, and taphonomicpoints of view. The most fossiliferous cetacean’s outcrops comprise the lower MioceneGaiman Formation, the upper Miocene Puerto Madryn Formation, and the Bajo del GualichoFormation of uncertain Miocene age. Numerous specimens were collected in the XIXcentury, and many have been recently studied taxonomically and anatomically. Modernfieldwork efforts have resulted in new and more well-preserved specimens, increasing thetaxonomic diversity of the assemblage but also the taphonomic and paleoecologicalinformation. This record has yielded an ecologically and taxonomically diverse cetaceancommunity composed of odontocetes (the dominant group including ziphiids, platanistoids,physeteroids, kentriodontids, eurhinodelphinids, and stem odontocetes) and mysticetes(balaenids, neobalaenids, cetotheriids and balaenopteroids). Odontocetes are composed ofsmall to large size marine forms, displaying a variety of feeding strategies (i.e., raptorial,combination suction, capture suction). Moreover, mysticetes are also represented by small tolarge size forms with ecological specializations ranging from skim to engulfment feeding. Forthe Gaiman Formation, two stratigraphically distinct cetacean assemblages are identified: oneincluding small-sized odontocetes (mainly platanistoids), preserved mostly in inner shelfembayment deposits and dominated by isolated postcranial and cranial elements to associatedcranial-postcranial skeletons. The other comprises large-size odontocetes and mysticetes(mainly physeteroids and balaenopteroids), preserved in open inner shelf deposits withisolated cranial elements as the most common category of preservation. Environmental,ecological, and biological factors have been identified as the main aspects controlling thecetacean assemblages in shelf environments from the Gaiman Formation. Preliminary resultsfor the Puerto Madryn Formation show a variety of preservation styles, ranging from isolatedcranial or postcranial elements to articulated specimens. Ongoing studies will allowdetermining which factors-controlled preservation and distribution of cetaceans in this unit aswell as in the remaining Miocene fossiliferous outcrops in Patagonia. Integrative studies ofthe Patagonian record will be of great value to characterize the evolution of cetacean’scommunities during the Neogene in the Southwestern Atlantic Ocean