• Article • Advances in Polar Science doi: 10.13679/j.advps.2020.0013 September 2020 Vol. 31 No. 3: 205-214 First description of scleractinian corals from the Santa Marta and Snow Hill Island (Gamma Member) formations, Upper Cretaceous, James Ross Island, Antarctica Roberto VIDEIRA-SANTOS1,2*, Sandro Marcelo SCHEFFLER1, Luiza Corral Martins de Oliveira PONCIANO3, Luiz Carlos WEINSCHÜTZ4, Rodrigo Giesta FIGUEIREDO5, Taissa RODRIGUES6, Juliana Manso SAYÃO7,8, Douglas Santos RIFF9 & Alexander Wilhelm Armin KELLNER8 1 Laboratório de Paleoinvertebrados, Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro, Quinta da Boa Vista, s/n, 20940-040, Rio de Janeiro, RJ, Brazil; 2 Universidade Federal Rural do Rio de Janeiro, BR-465, Km 07, s/n, 23890-000, Seropédica, RJ, Brazil; 3 Laboratório de Tafonomia e Paleoecologia Aplicadas – LABTAPHO, Departamento de Ciências Naturais – DCN, Universidade Federal do Estado do Rio de Janeiro – UNIRIO, Av. Pasteur, 458, 22290-250, Rio de Janeiro, RJ, Brasil; 4 Centro Paleontológico de Mafra – CENPALEO, Universidade do Contestado, Av. Pres. Nereu Ramos,1071, 89300-000, Mafra, SC, Brazil; 5 Departamento de Biologia, Universidade Federal do Espírito Santo – UFES, Alto Universitário s/n, Guararema, Alegre, ES, Brazil; 6 Laboratório de Paleontologia, Departamento de Ciências Biológicas, Centro de Ciências Humanas e Naturais, Universidade Federal do Espírito Santo – UFES, Avenida Fernando Ferrari, 514, Goiabeiras, 29075-910, Vitória, ES, Brazil; 7 Laboratório de Paleobiologia e Microestruturas, Núcleo de Biologia, Centro Acadêmico de Vitória, Universidade Federal de Pernambuco – UFPE, Rua do Alto do Reservatório, s/n, 52050-480, Vitória de Santo Antão, PE, Brazil; 8 Laboratory of Systematics and Taphonomy of Fossil Vertebrates, Departamento de Geologia e Paleontologia, Museu Nacional/Universidade Federal do Rio de Janeiro, Quinta da Boa Vista s/n, São Cristóvão, 20940-040 Rio de Janeiro, RJ, Brazil; 9 Laboratório de Paleontologia, Instituto de Biologia, Universidade Federal de Uberlândia, campus Umuarama, 38400-902, Uberlândia, MG, Brazil Received 21 April 2020; accepted 12 June 2020; published online 20 September 2020 Abstract Antarctic corals are known from the Upper Cretaceous Santa Marta Formation (Santonian–early Campanian) and Gamma Member (late Campanian) of Snow Hill Island Formation (late Campanian–early Maastrichtian) but they have not so far been taxonomically described. We describe three corals taxa based on 29 specimens collected in 2007 and 2016 on James Ross Island (northeast of the Antarctic Peninsula). They represent the first formal record of scleractinian corals from the Santa Marta Formation, identified as Caryophylliidae indet. and Gamma Member of Snow Hill Island Formation, identified as ?Astreopora sp. and Fungiacyathus deltoidophorus. The family Caryophylliidae and the genus Astreopora were not restricted to the Weddellian Biogeographic Province but the species Fungiacyathus deltoidophorus was endemic to Antarctica during the Cretaceous. The genus Fungiacyathus and the family Caryophylliidae thrive in Antarctica until the present day. Fungiacyathus occurred in shallower environments during the late Campanian than today. No specimens related to Astreopora have yet to be found in Antarctica after the late Campanian. This can be explained by the capacity of Fungiacyathus and Caryophyllidae to endure cold waters, since they are asymbiotic corals. The symbiotic ?Astreopora sp., due to its sensitivity to low temperatures, became extinct in this continent as soon as the Antarctic waters began to cool, around the Campanian/Maastrichtian. The presence of ?Astreopora sp. in Gamma Member of Snow Hill Island Formation may represents the first occurrence of this genus in Antarctica and the oldest record of this genus in the Southern Hemisphere. Corresponding author, ORCID: 0000-0002-6221-1693, E-mail: [email protected] www.aps-polar.org 206 Videira-Santos R, et al. Adv Polar Sci September (2020) Vol. 31 No. 3 Keywords scleractinia, taxonomy, Campanian, James Ross Sub-Basin, Antarctica Citation: Videira-Santos R, Scheffler S M, Ponciano L C M O, et al. First description of scleractinian corals from the Santa Marta and Snow Hill Island (Gamma Member) formations, Upper Cretaceous, James Ross Island, Antarctica. Adv Polar Sci, 2020, 31(3): 205-214, doi: 10.13679/j.advps.2020.0013 1 Introduction 2 Geological setting Scleractinians are solitary or colonial corals bearing a The James Ross Sub-Basin, part of the Larsen Basin, is skeleton of aragonite, including all true post-Paleozoic located in the northeast of the Antarctic Peninsula and fossil corals. These corals can be divided into two contains a significant Meso-Cenozoic sedimentary ecological groups: the symbiotic, characterized by the succession (Figure 1) related to the Gondwanan break-up presence of vast numbers of unicellular symbiotic, and subsequent development of a back-arc basin (Hathway, dinoflagellates or zooxanthellae in their endodermal tissues, 2000). and the asymbiotic, which lack of zooxanthellae (Wells, The James Ross Archipelago (James Ross, Snow Hill, 1956). Humps, Seymour, Vega, Cockburn, Persson and Lockyer Symbiotic corals are restricted to shallow tropical islands) presents the best exposure of volcano-sedimentary waters, generally with depths less than 20 m and rocks of its homonymous sub-basin. Two thick sedimentary temperatures between 25 ℃℃ and 29 , due to the successions are recognized on James Ross Island: Gustav photosynthetic needs of the zooxanthellae algae. Some Group (Aptian–Coniacian) and Marambio Group (Santonian– recent taxa can be found in depths up to 90 m, supporting Danian) (Olivero, 2012a). The Gustav Group consists of the temperatures as cold as 16 ℃ (Fernandes, 2011). Even Pedersen, Lagrelius Point, Kotick Point, Whisky Bay and though asymbiotic corals can occur associated with coral Hidden Lake formations (Riding and Crame, 2002), which reefs, they are not subjected to the same environmental represent a deep marine depositional environment with restrictions as the symbiotic, surviving in depths up to submarine fan and slope deposits. This group is not very 6000 m and temperatures ranging between 1.1 ℃ and 28 ℃. fossiliferous, being composed mainly of conglomerates and Their geographic distribution includes all the seas and sandstones (Ineson, 1989; Medina et al., 1992; Whitham et oceans of normal salinity (Fernandes, 2011). al., 2006). The Antarctic sedimentary rocks, from Mesozoic and The Marambio Group is rich in fossils, consisting of Cenozoic, are quite fossiliferous (e.g., Scasso et al., 1991; siltstones, argillites and fine-grained sandstones, interpreted Luther, 1999; Olivero, 2012a). At least 16 species of as being deposited in a shallow inner to outer continental scleractinian corals have been identified in the Late shelf environment with the presence of a prograding delta Cretaceous (Lopez de Bertodano Formation) and (Crame et al., 1991; Pirrie et al., 1997; Olivero, 2012a). Paleocene (Sobral Formation) strata from the Seymour and Although there are several proposed subdivisions for the Snow Hill islands (e.g. del Valle et al., 1982; Filkorn, Marambio Group (e.g., Pirrie et al., 1997; Olivero and 1994). So far, scleractinian corals in the Santa Marta Medina, 2000; Olivero, 2012a), in this contribution we Formation (Santonian–early Campanian) and Gamma follow the stratigraphy of Olivero (2012a), which divides Member (late Campanian) of Snow Hill Island Formation this group into: Santa Marta Formation, Rabot Formation, (late Campanian–early Maastrichtian) at James Ross Snow Hill Island Formation, Hamilton Point Member, Island have been recorded (e.g. Scasso et al., 1991; Karlsen Cliffs Member, Sanctuary Cliff Member, Haslum Olivero, 2012a) but were not studied in detail. Darrel and Crags Sandstone, Lopéz de Bertodano Formation and Taylor (1993) illustrated some coral specimens from Santa Sobral Formation (Figure 2). Marta Formation referring them to Deltocyathus? complanatus but did not provide any further taxonomic 2.1 Santa Marta and Snow Hill Island (Gamma description. Member) formations Here we provide the first taxonomic description of scleractinian corals from the Santa Marta Formation (Alpha The Santa Marta Formation (Santonian–early Campanian) Member) and Gamma Member of Snow Hill Island is composed of an intercalation of sandstones, siltstones, Formation, including the first record of asymbiotic and argillites with volcanic tuffs and rare coquinas (Olivero, Fungiacyathus deltoidophorus and Caryophylliidae indet., 2012a). It was originally defined to the northwest of James and the symbiotic symbiotic ?Astreopora sp. Ross Island and subdivided into Alpha, Beta and Gamma Corals from Santa Marta and Snow Hill Island formations, Antarctica 207 Figure 1 a, Sedimentary deposits of the Cretaceous/Paleogene outcrops of the James Ross Sub-Basin. In detail, the region where the PALEOANTAR I and II expeditions were concentrated. b, Simplified geological map of the Ulu Peninsula, showing outcrops of the Santa Marta (Alpha and Beta members) and Snow Hill Island (Gamma Member) formations, as well as the collection areas of the studied fossils. A—represents point AK 042 (Caryophylliidae indet.); B—represents points 22, 24, 26, AK 281 and AK 292 (Fungiacyathus deltoidophorus and ?Astreopora sp.) (adapted from Castro and Carvalho, 2015; Reguero et al., 2016). Figure 2 Several proposals of subdivisions of the Marambio Group, highlighting the proposal