Andean Geology 42 (2): 268-283. May, 2015 Andean Geology doi: 10.5027/andgeoV42n2-a06


New chondrichthyans from - levels of Río de Las Minas and Sierra Dorotea, , Chilean Patagonia

*Rodrigo A. Otero1, Sergio Soto-Acuña1, 2

1 Red Paleontológica Universidad de , Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile. [email protected] 2 Área de Paleontología, Museo Nacional de Historia Natural, Casilla 787, Santiago, Chile. [email protected]

* Corresponding author: [email protected]

ABSTRACT. Here we studied new chondrichthyans from two localities, Río de Las Minas, and Sierra Dorotea, both in the , southernmost Chile. In Río de Las Minas, the upper section of the Priabonian have yielded material referable to the taxa Megascyliorhinus sp., Pristiophorus sp., Rhinoptera sp., and Callorhinchus sp. In Sierra Dorotea, middle-to-late levels of the Río Turbio Formation have provided teeth referable to the taxa macrota (Agassiz), Palaeohypotodus rutoti (Winkler), Squalus aff. weltoni Long, Carcharias sp., Paraorthacodus sp., Rhinoptera sp., and indeterminate Myliobatids. These new records show the presence of common chondrichtyan diversity along most of the Magallanes Basin. The new record of Paraorthacodus sp. and P. rutoti, support the extension of their respective biochrons in the Magallanes Basin and likely in the southeastern Pacific.

Keywords: Cartilaginous fishes, Weddellian Province, Southernmost Chile.

RESUMEN. Nuevos condrictios de niveles Bartoniano-priabonianos de Río de Las Minas y Sierra Dorotea, Cuenca de Magallanes, Patagonia Chilena. Se estudiaron nuevos condrictios fósiles provenientes de dos localidades, Río de Las Minas y Sierra Dorotea, ambas en la Región de Magallanes, sur de Chile. En Río de Las Minas, la sección superior de la Formación Loreto (Priaboniano) ha proporcionado material referible a los taxa Megascyliorhinus sp., Pristiophorus sp., Rhinoptera sp., y Callorhinchus sp. En Sierra Dorotea, niveles del Eoceno medio a tardío de la Formación Río Turbio han proporcionado dientes atribuibles a los taxa Striatolamia macrota (Agassiz), Palaeohypotodus rutoti (Winkler), Squalus aff. weltoni Long, Carcharias sp., Paraorthacodus sp., Rhinoptera sp., y Myliobátidos indeterminados. Estos nuevos registros muestran la presencia de una diversidad común de condrictios a lo largo de la mayor parte de la cuenca de Magallanes. Los nuevos registros de Paraorthacodus sp. y P. rutoti apoyan la extensión de sus respectivos biocrones en la Cuenca de Magallanes y probablemente en el Pacífico suroriental.

Palabras clave: Peces cartilaginosos, Provincia Weddelliana, Extremo sur de Chile. Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 269

1. Introduction U-Pb shrimp radioisotopic dates (Hervé et al., 2004). The eastern part of the Sierra have unequivocally The research of fossil carried out in the levels, these being distinguished by the last along the Magallanes Region and supported presence of Glycimeris cf. ibari (Philippi, 1887), by two Antarctic Ring projects (Anillos de Ciencia Panopea cf. clausa (Wilckens, 1910) and Veneri- Antártica, Conicyt-Chile; ARTG-04 2007-2009; cardia (Venericor) carrerensis Griffin, 1991. This ACT-105 2010-2013) have recovered a diversity fauna was recognized by Griffin (1991) in outcrops of chondrichthyans ranging a time span between of the Río Turbio Formation (Feruglio, 1938) exposed the Maastrichtian and the late Eocene. Two main in Argentina. The unit extends beyond the northern localities have yielded abundant remains of the . margin of the international border, and follows a The upper section of the Loreto Formation exposed general N-S strike as it happens with most of the at Río de Las Minas near Punta Arenas includes so sedimentary units in the studied area. It is easily far at least 13 different taxa from a single level of observed that the levels of the Río Turbio Formation Priabonian (Otero et al., 2012). The second and are continous over the Chilean side. Following the richest locality is in the northern scheme of Hünicken (1955), the studied levels are part of the Magallanes Region, which has provided part of the upper section originally assigned to the remains of five typically Maastrichtian taxa and at -Eocene, based on stratigraphic correla- least eighteen taxa (Otero et al., 2013a). tions and fossil marine invertebrates. The age of We present new finds of fossil (Chondrich- this section was later constrained to the middle-late thyes, Elasmobranchi, Neoselachii) and chimaeroid Eocene by Malumián and Caramés (1997) based on fishes (Holocephali, Chimaeriformes) recovered stratigraphic correlations and microfossils. from two localities of the Magallanes Region in The chondrichthyan-bearing level studied here southernmost Chile. The first is Río de Las Minas, comprises brown-to-greenish sandstones with west of Punta Arenas. From the upper section of the coarse-to-fine grain. are abundant and mostly Loreto Formation the first local records of Mega- represented by marine invertebrates of the genera scyliorhinus cooperi Cappetta and Ward, 1977, Pris- Cucullaea, Glycimeris, Pholadomya, Panopea, as tiophorus sp., Callorhinchus sp., and Rhinoptera sp. well as ostreids. Vertebrates include the presence are here described. The second studied locality is of the Palaeeudyptes (Sallaberry et Sierra Dorotea, northeast of Puerto Natales. In the al., 2010). This genus has a widespread distribution latter, upper levels of the Río Turbio Formation along the Weddellian Biogeographic Province, WBP (Bartonian-Priabonian) have yielded specimens hereafter (Zinsmeister, 1979), and it is regarded as referable to the taxa Striatolamia macrota (Agassiz), typical form in the Eocene- of Antarctica, Carcharias ‘hopei’ (Agassiz), Palaeohypotodus rutoti but being particularly abundant in Priabonian levels (Winkler), Paraorthacodus sp., Rhinoptera sp., as (Reguero et al., 2013), thus, providing additional well as indeterminate miliobatoids and indeterminate support for a middle-to-late Eocene age for the callorhynchids. fossil bearing levels of Sierra Dorotea studied here.

2. Localities and Geologic Setting 2.2. Río de Las Minas, Punta Arenas

2.1. Sierra Dorotea, Puerto Natales This is located about 10 km west of Punta Arenas (53º08’S; 71º03’W), in the Brunswick Peninsula The first locality studied is Sierra Dorotea (Fig. 1). A canyon is conformed by a well-stratified (51°35”S; 72°21”W), settled 20 km NE from Puerto section of the Loreto Formation (Hoffstetter et al., Natales, near the international border with Argentina 1957). This unit is about 800 m thick, composed of (Fig. 1). In this locality, the base of the section is well-sorted sandstones and including glauconitic and better exposed on the cliffs facing to Puerto Natales. concretionary horizons with frequent intercalated The latter are part of the (Katz, beds containing fossil flora and several coal seams 1963) originally assigned to the Maastrichtian- of variable thickness. Fasola (1969) studied paly- based on biostratigraphic correlations, and nomorphs from several points along the Río de Las later constrained to the late Maastrichtian based on Minas canyon, assigning an Oligocene age for the 270 New chondrichthyans from Bartonian-Priabonian levels of Río de Las Minas and Sierra Dorotea...

FIG. 1. Map indicating the two localities where the studied material was recovered. A. Río de Las Minas, Punta Arenas; B. Sierra Dorotea, Puerto Natales. unit based on this record. The upper section (Otero with the chondrichthyan assemblage which indicate et al., 2012: fig. 2) includes a single level with chon- a Priabonian age (Otero et al., 2012 and references drichthyan teeth, which was dated on 36.48±0.47 Ma therein); in consequence, most of the section of the based on U-Pb Shrimp radioisotopic date. This age Loreto Formation exposed at Río de Las Minas is is consistent with the paleobotanic record as well as older than the Priabonian. Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 271

FIG. 2. Stratigraphic section of the upper part of Sierra Dorotea. Small numbers on each level follows the general description by Hu- nicken (1955, in Hoffstetter et al.,1957: p. 316-319), and complemented with the observations made during this current study.

3. Material and Methods previous to their final deposit. Isolated teeth were recovered from the recent soil formed by weathering Several tens of fragmentary remains of the fossiliferous sandstone, while in situ material were recovered by the authors from Río de Las was still included in well-consolidated matrix, being Minas and Sierra Dorotea, during January, 2013 and obtained by usage of chisels and direct hammering. January, 2014. Among these, the most abundant are Largest fragments observed (mostly birds) did chondrichthyan teeth, followed by less frequent bone not exceed 5 cm, while teeth belonging large taxa remains. Most of the collected specimens from Sierra were not found. Dorotea were scattered on surface and obtained by Morphologic criteria for identifying taxa were sieving, while few of them were directly recovered mostly based on Cappetta (1987, 2012). Comparisons from their respective hosting levels. The absence were carried out with previous specimens collected of any articulated specimens as well as the broken from Sierra Baguales (Otero et al., 2013a). cusplets in most teeth (even in those recovered in situ) The chronostratigraphic nomenclature and indicate that the vertebrate remains were reworked formal divisions used here follows the scheme of 272 New chondrichthyans from Bartonian-Priabonian levels of Río de Las Minas and Sierra Dorotea... the International Stratigraphic Chart of Cohen et Carcharias sp. al. (2013). Fig. 3G Institutional Abbreviation: SGO.PV: Paleontología de Vertebrados, Museo Nacional de Historia Natural, Material: SGO.PV.6548a-c: Three anterolateral Santiago, Chile. teeth. Eastern Sierra Dorotea, Magallanes Region, southernmost Chile. Upper levels of the Río Turbio 4. Systematic Paleontology Formation, Bartonian-Priabonian. Description: Anterior tooth with high and slender Class Huxley, 1880 crown, with sigmoidal profile; crown with complete Subclass Bonaparte, 1838 cutting edges; one sharp and medially recurved lateral Subcohort Neoselachii Compagno, 1977 cusplet on each side of the crown; root with separate Order Berg, 1958 branches and lingual bulk. Family Jordan, 1898 Remarks: The studied teeth are similar to those Genus Striatolamia Glikman, 1964 referred to C. ‘hopei’ by Ward (1988) and Cappetta and Nolf (2005), although a specific determination Type species: ‘ macrotus’ Agassiz, 1843; is here precluded since the latter species has unre- Eocene. Paris Basin, France. solved taxonomical status. Despite of this, teeth of Carcharias sp. are common in Bartonian-Priabonian Striatolamia macrota (Agassiz, 1843) strata along the Magallanes Basin, with previous Fig. 3A-F records in Río de Las Minas and Sierra Baguales (Otero et al., 2012, 2013a). The genus was also Material: SGO.PV.6549a, b: two isolated anterolateral recovered from Maastrichtian beds of the Dorotea teeth. Eastern Sierra Dorotea, Magallanes Region, Formation in Sierra Baguales (Otero et al., 2013a). southernmost Chile. Upper levels of the Río Turbio Although teeth of Carcharias spp.are abundant Formation, Bartonian-Priabonian. in southernmost South America since the Upper Description: Teeth with slender and sharp crown and through the rest of the Cenozoic having sigmoidal profile, with non-serrated cutting (Cione et al., 2007), this genus seems to be absent edges that fade near the base. The enameloid bear in higher latitudes. To date, no contemporary records profuse striations over its lingual surface but they are are known in Antarctica, suggesting that the austral absent on the labial surface. The labial enameloid distribution of the genus could be restricted to the overhangs the root. The root has two well-separated Magallanes Basin. branches and a lingual bulk. Remarks: Teeth of the species Striatolamia macrota Genus Palaeohypotodus Glickman, 1964 were previously recovered in southernmost Chile, Palaeohypotodus rutoti (Winkler, 1874) particularly in the localities of Sierra Baguales, Fig. 3H-I from beds of Bartonian-Priabonian age of the Río Baguales (=Man Aike) Formation, and in the upper Type species: ‘Odontaspis’ (=Palaeohypotodus) section of the Loreto Formation exposed at Río rutoti Winkler, 1874. Late Paleocene of Belgium. de Las Minas near Punta Arenas, from levels of Material: SGO.PV.6556a: One anterior tooth. SGO. Priabonian age (Otero et al., 2012, 2013a). This PV.6556b: one lateral tooth, both isolated. Eastern species is also abundant in Bartonian-Priabonian Sierra Dorotea, Magallanes Region, southernmost strata of the La Meseta Formation in Seymour Chile. Upper levels of the Río Turbio Formation, Island, Antarctica (Reguero et al., 2013 and refer- Bartonian-Priabonian. ences therein). Description: Anterior tooth with high and slender crown that becomes distally broader than its base Family Odontaspididae Müller and Henle, 1838 and labially convex; sigmoidal profile of the crown Genus Carcharias Rafinesque, 1810 and soft enamel in both labial and lingual surfaces; crown with cutting edges fading near the base; roots Type species: Carcharias taurus Rafinesque, 1810. with well-separated branches leaving a deep notch Recent. between them. Lateral teeth having two to three Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 273 sp. lingual view; lingual E. L. Paraorthacodus labial view; view; labial D. sp. SGO.PV.6553a. Lateral tooth; tooth; Lateral sp. SGO.PV.6553a. SGO.PV.6556a, anterior tooth in labial view; tooth in labial view; anterior SGO.PV.6556a, H. Megasyliorhinus Megasyliorhinus SGO.PV.6557b, lateral tooth in labial view; K. SGO.PV.6557b, basal view. Río de Las Minas, Punta Arenas, southernmost Chile. Upper Chile. Arenas, southernmost Río de Las Minas, Punta S. basal view. profile view. SGO.PV.6549b, anterolateral tooth; tooth; anterolateral profile SGO.PV.6549b, view. Palaeohypotodus rutoti Winkler; R. profileview; C. view; lingual B. labial view; Q. labial SGO.PV.6557a, lateral tooth in labial view; SGO.PV.6557a, J. Long; weltoni aff. aff. SGO.PV.6548a, anterolateral tooth in labial view. tooth in labial view. anterolateral G. SGO.PV.6548a, Squalus lingual view. Upper levels of the Río Turbio Formation, Middle to Late Eocene. Late to Middle Formation, Turbio Río the of levels Upper view. lingual M. SGO.PV.6549a, anterolateral tooth in labial view; view; labial in tooth anterolateral SGO.PV.6549a, basal view. SGO.PV.6553b. Lateral tooth; Lateral SGO.PV.6553b. view. basal A. P. ’ (Agassiz); ‘ hopei ’ (Agassiz). (Agassiz). Carcharias Carcharias O. profileview; SGO.PV.6556b, lateral tooth in labial view. lateral tooth in labial view. SGO.PV.6556b, riatolamia macrota macrota riatolamia profile view. labial view; N. labial levels of the Loreto Formation, Late Eocene (Priabonian). Scale bar equals 10 mm. F. I. view; labial in tooth lateral SGO.PV.6547, 3. St 3. FIG. 274 New chondrichthyans from Bartonian-Priabonian levels of Río de Las Minas and Sierra Dorotea... sharp and medially recurved lateral cusplets on each Order Duffin and Ward, 1993 side of the crown; base of the crown overhanging Family Palaeospinacidae Regan, 1906 the root and having profuse vertical folds; root with Genus Paraorthacodus Glikman, 1958 well-separated branches and lingual bulk. Remarks: This is the first record of the species in Type species: ‘Sphenodus’ recurvus Trautschold, the Magallanes Basin. Previous austral records on 1877. Cenomanian of Russia. the WBP are known from early Eocene () levels of the La Meseta Formation in Seymour Island, Paraorthacodus sp. Antarctica (Long, 1992; Kriwet, 2005; Reguero et Fig. 3L-M al., 2013). This age differs from the records along the Northern Hemisphere, where this species is restricted Material: SGO.PV.6547: One isolated tooth. Eastern to the Paleocene (Cappetta, 1987). Sierra Dorotea, Magallanes Region, southernmost Chile. Upper levels of the Río Turbio Formation, Order Squaliformes Goodrich, 1909 Bartonian-Priabonian. Family Squalidae Bonaparte, 1834 Description: Teeth axially broader than dorsoven- Genus Squalus Linnaeus, 1758 trally high, with short, triangular but slender crown having two or three triangular lateral cusplets; both Squalus aff. weltoni Long, 1992 lingual and labial surfaces of the crown bear stria- Fig. 3J-K tions extended between from tip to base; the root is distinctive, with a flat base having several parallel Type species: Squalus weltoni Long, 1992. Seymour nutritious grooves that extend over the lingual face; Island, Antarctica. La Meseta Formation, late Eocene. presence of a lingual bulk on the root. Material: SGO.PV.6557a-c: Three lateral teeth. Eastern Remarks: The genus Paraorthacodus have been Sierra Dorotea, Magallanes Region, southernmost recorded in the Upper Cretaceous of Argentina Chile. Upper levels of the Río Turbio Formation, (Ameghino, 1893), central Chile (Suárez et al., Bartonian-Priabonian. 2003) and Antarctica (Klug et al., 2008). Its pro- Description: Teeth small, larger than high; crown vincial distribution on Paleogene units is also docu- triangular and distally recurved, with complete mented in central Chile from likely Paleocene strata cutting edge and having serrations in the anterior (Muñoz-Ramírez et al., 2007; González et al., 2010; margin; Labial face with an apron that extends Groz and Palma 2013). Although its worldwide record ventrally to the root, while in the lingual face there seems to be restricted to the Paleocene (Cappetta, is a projection of the crown (uvula, sensu Cappetta, 1987), the genus was found in Ypresian levels of the 1987). The root has rhomboidal basal outline, being La Meseta Formation (Cucullaea I Allomember) narrower than the crown and with several nutritious (A. Cione, personal communication in Reguero et foramina. al., 2013). Considering this, the presence of a single Remarks: Squalid sharks have been reported in tooth in Sierra Dorotea suggests the re-working the WBP. Records from Eocene levels of the La from older strata that could reach even Ypresian Meseta Formation in Antarctica firstly included levels. This is also supported by a similar situa- indeterminate squalids (Welton and Zinsmeister, tion detected on Sierra Baguales, with a reworking 1980). These were later precised as the species that could reach to Paleocene levels based on S. woodbrunei Long, 1992 and S. weltoni Long, the presence of teeth of the genera Otodus obli- 1992. In addition, the genus Centrophorus was also quus and Megascyliorhinus cooperi (Otero et al., described from the same unit. Previous records in 2013a). southern South America only include the genus Centrophoroides found in Maastrichtian levels of Order Compagno, 1973 the Dorotea Formation in Sierra Baguales (Otero et Family Scyliorhinidae Gill, 1862 al., 2013a). The new specimens here studied confirm Genus Megascyliorhinus Cappetta and Ward, 1977 the persistence of squalids in the Magallanes Basin throughout the K/P boundary, while it verifies the Type species: Megascyliorhinus cooperi Cappetta widespread distribution of the family along the WBP. and Ward, 1977. Ypresian of England. Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 275

Megascyliorhinus sp. with smooth enameloid; complete cutting edge in Fig. 3N-S the anterior margin; cutting edge of the posterior margin fading near the half of the crown. Material: SGO.PV.6553a, b: Two isolated teeth. Río Remarks: Rostral teeth of Pristiophorus are de Las Minas, Punta Arenas, southernmost Chile. known in high latitudes of the Southern Hemi- Upper levels of the Loreto Formation, Priabonian. sphere since the Upper Cretaceous. The genus Description: Teeth with high, slender, and triangular was recovered from upper Maastrichtian levels crown, basally swollen and lingually recurved; one of the López de Bertodano Formation (Klb9) in medially recurved lateral cusplet on each side; soft Seymour Island, Antarctica (Otero et al., 2014), enameloid; root comparatively small with respect while the species P. lanceolatus have been de- to the crown, with two short but massive branches scribed from Eocene levels of the La Meseta separated by a deep groove, and a prominent lin- Formation, in the same locality. The genus was gual bulk. also reported in Bartonian-Priabonian levels of the Remarks: Regionally, identical teeth have been Man Aike Formation exposed at Sierra Baguales recovered from lower levels of the Man Aike (=Río (Otero et al., 2013a). Baguales) Formation in Sierra Baguales, north of Magallanes Region, being firstly referred to Superorder Batomorphii Capetta, 1980 M. cooperi by Otero et al. (2013a) due its narrow Order Myliobatiformes Compagno, 1973 morphologic affinities. Since this species was Family Rhinopteridae Jordan and Evermann, 1896 originally recovered from Ypresian beds of England Genus Rhinoptera Cuvier, 1829 (Cappetta and Ward, 1977) and due the evidence of re-working in lower levels of the Man Aike Forma- Type species: ‘Myliobatis’ marginata Saint-Hilaire, tion, Otero et al. (2013a) considered the possibility 1809. Recent. that the studied specimens could be hosted in levels older than the Bartonian. Otherwise, the known Rhinoptera sp. record of the genus Megascyliorhinus extends from Fig. 4C-F the Eocene onwards the . The current find in Priabonian levels of the Loreto Formation Material: SGO.PV.6551: One lateral tooth. Río proves the occurrence of this taxon in younger beds de Las Minas, Punta Arenas, southernmost Chile. along the Magallanes Basin. Regionally, the genus Upper levels of the Loreto Formation, Priabonian. (represented by a probable different species with SGO.PV.6552: One complete central plate. Eastern higher crowns) was recovered from Oligocene beds of Sierra Dorotea, Magallanes Region, southernmost New Zealand (Keyes, 1984) proving its widespread Chile. Upper levels of the Río Turbio Formation, distribution during the Eocene-Oligocene boundary Bartonian-Priabonian. along the WBP (Zinsmeister, 1979). Diagnosis: For diagnosis, see Cappetta (1987). Description: Isolated and complete median tooth Order Pristiophoriformes Berg, 1958 plate with flat occlusal surface of the crown, having Family Pristiophoridae Bleeker, 1859 profuse punctuations over the latter, and wrinkles Genus Pristiophorus Müller and Henle, 1837 around the lateral margins of the crown; holoau- lacorhize vascularization of the root, with parallel Type species: Pristis cirratus Latham, 1794. Recent. nutritious grooves comparatively deeper than those of Myliobatis and having high and recurved septa Pristiophorus sp. between each basal groove. Fig. 4A-B Remarks: The materials here described are the first teeth referable to this genus found in Eocene Material: SGO.PV.6554. One isolated rostral spine. beds of the Magallanes Basin. Teeth of Rhinop- Río de Las Minas, Punta Arenas, southernmost Chile. tera were reported from likely Paleocene strata of Upper levels of the Loreto Formation, Priabonian. central Chile (Muñoz-Ramírez et al., 2007). The Description: Isolated crown of a rostral tooth; long genus remains unreported yet in higher latitudes of and slender crown, dorso-ventrally compressed, Antarctica. 276 New chondrichthyans from Bartonian-Priabonian levels of Río de Las Minas and Sierra Dorotea... - I . Occlusal view; sp. SGO.PV.6555, left mandibular; sp. SGO.PV.6555, . SGO.PV.6550, fragment of a median tooth plate in pro tooth plate of a median fragment G . SGO.PV.6550, Callorhinchus Callorhinchus axial view. Myliobatidae indet; Myliobatidae view. axial

F . Same in . same in basal view. Río de Las Minas, Punta Arenas, southernmost Chile. Upper levels of the Loreto of the levels Upper Chile. Arenas, southernmost Minas, Punta Las de Río view. basal in D . same . axial view. Río de Las Minas, Punta Arenas, southernmost Chile. Upper levels of the Loreto Formation, Late Eocene Late Formation, of the Loreto Upper levels Arenas, southernmost Chile. Río de Las Minas, Punta view. B . axial . SGO.PV. 6551, median tooth plate; 6551, median E . SGO.PV. . SGO.PV.6552 lateral tooth in lateral view; lateral in tooth lateral C . SGO.PV.6552 sp.; sp. SGO.PV.6554. Rostral spine. A . dorsal view; sp. SGO.PV.6554. Rhinoptera . Same in axial view. Eastern slopes of the Sierra Dorotea, Magallanes Region, southernmost Chile. slopes of the Sierra Dorotea, Magallanes Eastern view. H . Same in axial . Basal view. Río de Las Minas, Punta Arenas, southernmost Chile. Upper levels of the Loreto Formation, Late Eocene (Priabonian). Scale bar equals 10 mm. Río de Las Minas, Punta J . Basal view. file view; (Priabonian). Eocene (Priabonian); Late Formation, 4. P ristiophorus FIG. Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 277

Family Myliobatidae Bonaparte, 1838 Eocene levels of the La Meseta Formation, in the same locality (Kriwet and Gaździcki, 2003). Myliobatidae indet. Fig. 4G-H 5. Discussion

Material: SGO.PV.6550: One fragment of medial 5.1. Condrichthyan Paleobiogeography along tooth. Eastern Sierra Dorotea, Magallanes Region, the Magallanes Basin and Antarctica during southernmost Chile. Upper levels of the Río Turbio the Eocene Formation, Bartonian-Priabonian. Description: small medial fragment of a median The Antarcto-Pacific Eocene diversity of chon- tooth plate, showing typical holoaulacorhize vas- drichthyans includes elements with global distribution, cularization of the root with parallel nutritious as well as others so far restricted to the Southern grooves. The occlusal surface of the crown is flat Hemisphere. Based on the known record, four groups and in profile view, the latter is axially shifted with can be separated based on their known paleobiogeo- respect to the root. graphic distribution: i. taxa exclusively restricted to Remarks: Dental plates of myliobatids are frequent latitudes near 65°S on the Antarctic Peninsula. This along Eocene units of the WBP (Kriwet, 2005; group includes the genera Bathyraja, , Reguero et al., 2013; Otero et al., 2012, 2013a). The Centrophorus, Cetorhinus, Stegostoma, Dalatias, new find, although fragmentary, provides evidence Deania, Heptranchias, Lamna, Pristis, Pseudogin- on the widespread distribution of Myliobatis along glymostoma, Scoliodon, and Chimaera (Kriwet, the Magallanes Basin. 2005; Reguero et al., 2013). These genera are also known in the Northern Hemisphere (Cappetta, 1987 Subclass Holocephali Bonaparte, 1832 and references therein); ii. a second tentative group Order Chimaeriformes Obruchev, 1953 comprise those taxa restricted to the Antarctic Pen- Family Callorhynchidae Garman, 1901 insula and southernmost South America. So far, only Genus Callorhinchus Lacépède, 1798 the genera Anomotodon and Callorhinchus fall into this condition (Kriwet, 2005; Otero et al., 2013b), Type species: Callorhinchus callorhynchus (Lin- and it is possible that this situation could be a bias of naeus, 1758), Recent. the still incomplete austral record; iii. a third group comprise a larger diversity with widespread taxa Callorhinchus sp. along Antarctica and the Magallanes Basin during Fig. 4I-J the Eocene. These are represented by the genera Carcharocles, Galeorhinus, Hexanchus, Ischyodus, Material: SGO.PV.6555. One isolated mandibular Jaekelotodus, Macrorhizodus, Myliobatis, Odontas- plate. Río de Las Minas, Punta Arenas, southern- pis, Palaeohypotodus (known in the Paleocene of most Chile. Upper levels of the Loreto Formation, the Northern Hemisphere but recovered from upper Priabonian. Ypresian levels of Antarctica; see Reguero et al., Diagnosis: For diagnosis of the genus Callorhinchus, 2013), Paraorthacodus (recovered from latest Ypre- see Kriwet and Gaździcki (2003). sian levels of Antarctica; see Reguero et al., 2013), Description: Mandibular tooth plate with a single Pristiophorus, Squalus, Squatina and Striatolamia, central hypermineralized pad restricted to the distal while the genera , Carcharias, , part of the coronal surface, flanked by narrow tri- Megascyliorhinus, Notorhynchus, and Rhinoptera tors on the symphyseal and/or labial edges (Otero are to date restricted to southern South America et al., 2013b). during this lapse; iv. finally, a fourth group include Remarks: The genus Callorhinchus is a widespread the genera Otodus and Rhizoprionodon which are taxon along the WBP between the Upper Cretaceous- only known in the northern part of the Magallanes Eocene. Its presence is documented from upper Region (lat. 50°48’). The distribution of all these Maastrichtian levels of the López de Bertodano taxa is summarized on Table 1. Formation in Seymour Island, Antarctica (Martin The new records described here allow comple- and Crame, 2006; Otero et al., 2013b) and from menting the distribution of S. macrota, P. rutoti, 278 New chondrichthyans from Bartonian-Priabonian levels of Río de Las Minas and Sierra Dorotea...


Genus Antarctica Río de Las Minas Sierra Dorotea Sierra Baguales Bathyraja x - - - Carcharhinus x - - - Centrophorus x - - - Cetorhinus x - - - Chimaera x - - - Dalatias x - - - Deania x - - - Heptranchias x - - - Lamna x - - - Pristis x - - - Pseudoginglymostoma x - - - Scoliodon x - - - Stegostoma x - - - Anomotodon x x - - Callorhinchus x x - - Palaeohypotodus x - x - Carcharocles x - - x Galeorhinus - x - - Hexanchus x x - x Ischyodus x x - x Jaekelotodus - - - x Macrorhizodus x x - x Myliobatis x x x x Odontaspis x x x x Paraorthacodus x - x - Pristiophorus x x - x Squalus x - x - Squatina x x - x Striatolamia x x x x Abdounia - x - x Carcharias - x x x Carcharoides - x - x Megascyliorhinus - x - x Notorhynchus - x - x Rhinoptera - x x - Otodus - - - x Rhizoprionodon - - - x

Sources of information from Kriwet (2005), Otero et al. (2012, 2013a, 2014), Reguero et al. (2013) (R), and this study. Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 279

Carcharias sp., as well as myliobatids, which now 2013). Similar is the case of Palaeohypotodus rutoti, can be regarded as common faunal elements along species restricted to the of the Northern the Magallanes Basin. Despite remaining unknown Hemisphere but also recorded in the Ypresian of the in Sierra Dorotea, the records of Megascyliorhinus in Cucullaea I member of La Meseta Formation (Long, Río de Las Minas and Sierra Baguales also indicate 1992; Reguero et al., 2013). This documented exten- a widespread distribution. In addition, Rhinopte- sion of its chronostratigraphic range makes plausible ra sp. is at least restricted to the southern and central their eventual occurrence in Bartonian-Priabonian part of the same basin. levels of the Río Turbio exposed at Sierra Dorotea by extension of biochrons. However, an eventual 5.2. Chronostratigraphic implications of the new reworking of the material from Ypresian levels and records subsequent redepositation on Bartonian-Priabonian horizons of the Río Turbio cannot be ruled, pointing The presence of Megascyliorhinus sp. in out- out the need of radioisotopic dates for support this crops of the Loreto Formation at Río de Las Minas still partial evidence. is interesting. Chondrichthyan records found in the The geologic setting of the marine basins in locality were all recovered from a single level and Magallanes and in the southeastern Pacific shows they represent an assemblage of a well constrained in both cases a general absence of Paleocene beds. age (Priabonian-), while radioisotopic dates Upper Cretaceous (Maastrichtian) marine sediments indicates a very well defined peak at 36.48±0.47 Ma, are commonly contacted with middle-to-late Eocene constraining the age of the fossil-bearing level beds through an erosive unconformity. Such is the exclusively to the Priabonian (Otero et al., 2012). case between the the and the Lower levels of the same section include coal Concepción Group (sensu Charrier et al., 2007) in seams representing stagnant marshes with abundant central Chile (Stinnesbeck, 1986), as well as between vegetation, and the large-scale cross-bedding of the Dorotea Formation and the Man Aike-Río Turbio some sandstone units that is typical of Gilbert-type (and likely Loreto) formations in southernmost Chile bayhead deltas or migrating barrier bars (Le Roux et (Katz, 1963; Charrier and Lahsen, 1969). The only al., 2010), consistent with an estuarine depositional possible Paleocene beds in the Magallanes Basin environment. On the other hand, regional previous are represented as an exception in Cerro Dorotea records of Megascyliorhinus are only known in Formation (Hünicken, 1955), which levels con- the northern part of the Magallanes Basin, being formably overlies the Cerro Cazador (=Dorotea) recovered from Bartonian-Priabonian beds of Sierra Formation in outcrops near to Río Turbio, Argentina. Baguales (Otero et al., 2013a). Since the teeth from Chondrichthyan records from the Quiriquina Basin Río de Las Minas do not differ from those from Sierra include Maastrichtian assemblages (Suárez et al., Baguales, we consider them as probably belonging 2003) and more recently, Paleogene assemblages to the very same species (still indeterminate). Also, including the genera Paraorthacodus and Palaeohy- due the late Eocene age of the material (radioisotopi- potodus (Muñoz-Ramírez et al., 2007; González et cally controlled in Río de Las Minas), the previous al., 2010; Groz and Palma-Heldt, 2013). Considering identification of Megascyliorhinus cooperi in Sierra the Pacific Maastrichtian-Eocene discordance, is Baguales should be kept only to genus level, being likely that these records have an Eocene age. Such possible that these teeth belong to a still poorly known situation adds support to the existence of a biochron species typicallt distributed in the Magallanes basin extension for several classically Paleogene taxa but during the late Eocene. recorded from Eocene levels of the WBP. On the other hand, the presence of Paraortha- The additional specimens here referred to codus sp. in Sierra Dorotea is very interesting. The ge- Callorhinchus sp., and Rhinoptera sp., respectively nus is well-known in the Upper Cretaceous-Paleocene represents their first Eocene occurrence in the with a widespread distribution (Cappetta, 1987). An Magallanes Basin. The new record of Pristiophorus sp. exception to this happens on Ypresian levels of the extends its contemporary occurrence in the southern La Meseta Formation (Cucullaea I Allomember) margin of the basin. The new records of Striatolamia where the genus Paraorthacodus have been recovered macrota (Agassiz), Carcharias sp., Rhinoptera sp., and (A. Cione, personal communication in Reguero et al., indeterminate myliobatids in Bartonian-Priabonian 280 New chondrichthyans from Bartonian-Priabonian levels of Río de Las Minas and Sierra Dorotea... beds of Sierra Dorotea allow complementing the from Sierra Baguales. From the 16 genera recognized distribution of these taxa between the previous in the upper section of the Loreto Formation at Río records from Río de Las Minas and Sierra Baguales, de Las Minas, 13 of them are now recognized to be respectively. also present in Bartonian-Priabonian levels at Sierra Baguales. This faunal correlation supports that the 6. Conclusions deposition on each locality was nearly contemporary and occurred in a very similar environment. These The studied material includes the first record of results also indicate a noticeable degree of corre- Megascyliorhinus sp., Pristiophorus sp., Callorhin- lation between part of the Man Aike Formation at chus sp., and Rhinoptera sp. in late Eocene levels of Sierra Baguales, the upper slopes of the Río Turbio the Loreto Formation exposed at Río de Las Minas, Formation at Sierra Dorotea, and finally, the upper Punta Arenas, southernmost Chile. The radioisotopic section of the Loreto Formation at Río de Las Minas. date and the relative age obtained from the previously recognized chondrichthyan assemblage confirm the Acknowledgments Priabonian age of the fossil-bearing level, while The authors, fieldwork, logistics and research were the depositional environment and the taphonomic supported by the Antarctic Ring Project ACT-105, Conicyt- condition of most of the teeth preserving even their Chile. Especial thanks to J.L. Oyarzún (Puerto Natales) delicate cusplets, allow discarding the reworking for his valuable assistance on the first fieldworks and of the material from older levels. Since M. cooperi logistics. C. Underwood (Birkbeck University of London) have been considered as a typical Ypresian taxon, and C. Pimiento (Florida Museum of Natural History) we propose an extension of its biochron along the are especially thanked for the review and the valuable southeastern Pacific at least until the Priabonian. 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Iconografia della fauna italica per extension of its previous known Biochron (Upper le quattro classi degli animali vertebrati. Tomo III, Cretaceous-Ypresian), although, the re-working of puntata 29-58. Pesci. the recovered specimen from older strata in Sierra Cappetta, H. 1980. Les sélaciens du Crétacé Supérieur Dorotea cannot be discarded. The additional taxa du Liban. 2: Batoides. Palaeontographica Abteilung described from the latter locality complements their A (168): 149-229. contemporary distribution along the Magallanes Cappetta, H. 1987. Handbook of Paleoichthyology. Vo- Basin, proving the existence of a faunal continuity lume 3b: Chondrichthyes II. and Cenozoic along the latter, based on the austral-most records Elasmobranchii (Schultze, H.-P.; editor). Gustav from Río de Las Minas and the northern-most records Fischer Verlag: 193 p. Otero and Soto-Acuña / Andean Geology 42 (2): 268-283, 2015 281

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Manuscript received: March 13, 2014; revised/accepted: March 23, 2015; available online: March 27, 2015.