Additions to the Diversity of Elasmosaurid Plesiosaurs from the Upper Cretaceous of Antarctica

GR-01107; No of Pages 13 Gondwana Research xxx (2013) xxx–xxx

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Additions to the diversity of elasmosaurid plesiosaurs from the Upper Cretaceous of Antarctica

Rodrigo A. Otero a,⁎, Sergio Soto-Acuña a,b, Alexander O. Vargas a, David Rubilar-Rogers b, Roberto E. Yury-Yáñez c,CarolinaS.Gutsteind a Red Paleontológica U-Chile, Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile b Área Paleontología, Museo Nacional de Historia Natural, Casilla 787, Santiago, Chile c Laboratorio de Zoología de Vertebrados, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile d Laboratorio de Ecoﬁsiología, Departamento de Ciencias Ecológicas, Facultad de Ciencias, Universidad de Chile, Las Palmeras 3425, Santiago, Chile article info abstract

Article history: Three specimens of elasmosaurid plesiosaurs (Sauropterygia, Plesiosauria) from Upper Cretaceous beds of Received 16 April 2013 Antarctica are described here. These include postcranial remains of a single adult individual recovered from Received in revised form 4 July 2013 late Maastrichtian beds of Marambio (=Seymour) Island, possessing a distinctive combination of features: cer- Accepted 18 July 2013 vical vertebrae having centra with a triangular outline in transverse section, a vertical groove on the rostral and Available online xxxx caudal edge of the neural spines, and a deep articulation over the neural arch for the following postzygapophysis, Handling Editor: P. Eriksson while the scapula shows an unusually large and anteriorly recurved dorsal process. This combination of features is unknown in any adult, postcranial elasmosaurid genus recovered to date in the Upper Cretaceous of the Keywords: Weddellian Biogeographic Province and could represent a new form. Additional specimens from James Ross New plesiosaurs Island comprise the first record of an Aristonectinae (Plesiosauria, Elasmosauridae) in late Campanian beds, Diversity being the oldest known record of this sub-family. Finally, a third specimen from the same age and locality reveals Uppermost Cretaceous the presence of very-long necked elasmosaurids with affinities to typical representatives from the Upper Antarctica Cretaceous of the Northern Hemisphere. These findings add to the known diversity of Upper Cretaceous elasmosaurids in high latitudes of the Southern Hemisphere. © 2013 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

1. Introduction remains of a probable single specimen, recovered from Marambio Island. Based on histological sections and the morphology of the recov- Plesiosauria (Reptilia, Sauropterygia) from Antarctica are known ered portions, these authors indicated that the specimen was small since the seventies. The firstreportisduetoDel Valle et al. (1977) (about 2 m in length) and probably a sub-adult individual, while several who mentioned the presence of indeterminate plesiosaurs on James morphologic characters, especially the tibia and the femoral head, Ross and Vega Islands, east of the Antarctic Peninsula. Later, Chatterjee where considered similar to those of the species Mauisaurus haasti and Zinsmeister (1982) mentioned the first remains of these reptiles Hector (1874), from the Campanian of New Zealand. Thereafter, in Marambio (=Seymour) Island, also east of the Antarctic Peninsula. Gasparini et al. (2003) re-described the holotype of Aristonectes Gasparini et al. (1984) described associated postcranial remains of a parvidens Cabrera (1941), a very strange plesiosaur with uncertain single individual recovered from the latter island, this they regarded affinities at that time, recovered from Maastrichtian beds of Chubut, as a different morphotype from previously known elasmosaurids, Argentina. Besides the inclusion of A. parvidens among the although no genus or species was proposed. These records were elasmosaurids, additional materials referred to by Gasparini et al. discussed by Gasparini and Goñi (1985) in a regional context together (2003) to this species included finds in the late Maastrichtian of Chile with previous Upper Cretaceous records from Argentina and Chile. (Casamiquela, 1969), while the holotype of ‘Morturneria seymourensis’ The first Antarctic species described was ‘Turneria seymourensis’ from Antarctica (comprised by a juvenile specimen) was considered Chatterjee and Small (1989) from late Maastrichtian beds of Marambio as a junior synonym of A. parvidens. Additional material of Island, based on a partial skull and associated cervicals. This was later elasmosaurids from Seymour Island was described by Martin and re-named as ‘Morturneria seymourensis’ by Chatterjee and Creisler Crame (2006) including associated vertebrae with ribs and fragments (1994) due to duplication of the genus name in another taxon. of propodials of a single individual, a second specimen comprising a Fostowicz–Frelik and Gaździcki (2001) described new plesiosaur partial postcranial skeleton and one last specimen comprising a partial propodial. The latter authors also mentioned an additional specimen ⁎ Corresponding author. Tel.: +56 9 8 2981487. referred to cf. Elasmosauridae as well as seven specimens referred to E-mail address: [email protected] (R.A. Otero). Plesiosauria indet., from James Ross and Seymour Islands. A pelvic girdle

Fig. 1. Map of the Antarctic Peninsula, indicating the location of the fossil sites on Marambio and James Ross Islands, as well as a geological sketch map of the study area (based on Olivero, (2012)).

Please cite this article as: Otero, R.A., et al., Additions to the diversity of elasmosaurid plesiosaurs from the Upper Cretaceous of Antarctica, Gond- wana Research (2013), http://dx.doi.org/10.1016/j.gr.2013.07.016 R.A. Otero et al. / Gondwana Research xxx (2013) xxx–xxx 3 beds are present in its basal half. Ammonoids and palynomorphs (Suárez and Fritis, 2002; Otero et al., 2012), both recovered from late indicate a late Campanian–early Maastrichtian age for this unit. The Maastrichtian beds of the Quiriquina Formation in central Chile. Haslum Crag Member of the Snow Hill Island Formation (Pirrie et al., Anatomical abbreviations. af, anterior articular facet of the vertebra; ag, 1997) was elevated to formation status and differentiated as the Haslum anterior portion of the neural spine groove; aps, anterior process of the Crag Sandstone by Olivero et al. (2008). scapula; c2, cervical vertebra 2; c3, cervical vertebra 3; c5, cervical vertebra 5; cr, caudal rib; dfp, deep heart-shaped facet for postzygapophyses; 2.4. López de Bertodano Formation (Rinaldi et al., 1978) dps, dorsal process of the scapula; fha, facets for the haemal arches; g, gastralium; nc, neural canal; ns, neural spine; pc2; fragment of vertebra This unit crops out in the southwestern half of the Marambio Island, posterior to c2; pc3, fragment of vertebra posterior to c3; pg, posterior comprising mainly friable sandy siltstones with a yellow to gray color, portion of the neural spine groove; pna, facets for pedicels of the neural variable in hardness, but relatively constant in grain size and mud arch; poz, postzygapophysis; prz, prezygapophysis; r, rib; rf, rib facet; vf, percentage (Macellari, 1988). The age of this formation was assigned by ventral foramina; vn, ventral notch. the latter author to the Maastrichtian–Paleocene, based on mollusks Institutional abbreviations.SGO.PV.,ColeccióndePaleontologíade (Zinsmeister, 1979, 1982), microfossils (Huber, 1988) and palynomorphs Vertebrados, Área de Paleontología, Museo Nacional de Historia Natural, (Askin, 1989), and thereafter constrained to the latest Maastrichtian Santiago, Chile; MLP, Museo de La Plata, Argentina; MCS, Colección del based on different stratigraphic criteria (Crame et al., 2004). The López Museo de Cinco Saltos, Río Negro, Argentina; CM Zfr, Canterbury de Bertodano Formation was divided into 10 informal units (Macellari, Museum, Christchurch, New Zealand; ZPAL R., Institute of Paleobiology, 1984, 1988), named from base to roof as Klb1 to Klb9 which are late Polish Academy of Sciences, Warsaw, Poland. Maastrichtian in age, while the uppermost KTplb10 includes strata of Paleocene age. Specimen SGO.PV.6523 was recovered from the upper 4. Systematic paleontology portion of the Klb9 unit, and was collected during January of 2011 by one of the authors (RAO). DIAPSIDA Osborn, 1903. SAUROPTERYGIA Owen, 1860. 3. Materials and methods PLESIOSAURIA de Blainville, 1835. ELASMOSAURIDAE Cope, 1869 (sensu Ketchum and Benson, 2010). Two of the studied specimens (SGO.PV.6523 and SGO.PV.6508) in- Elasmosauridae gen. et sp. indet. clude cervical centra. Their proportions were evaluated using a bivariate (Figs. 2–4). graphic analysis following O'Gorman et al. (2013). The indices here considered are those proposed by Welles (1952), particularly the 4.1. Material height/length ratio (HI = 100 ∗ H/L), the breadth/length ratio (BI = 100 ∗ B/L), as well as the rate of vertebral elongation (VLI = 100 ∗ L/ SGO.PV.6523: Postcranial remains of a single adult individual, (0.5 ∗ (H + B))). Since SGO.PV.6523 belongs to an adult individual, including remains of 9 mid-to-posterior cervical vertebrae (6 of them comparisons were carried out considering adult representatives from preserving parts of their centra), the right scapula, several fragments the Upper Cretaceous of North America, particularly Hydrotherosaurus of ribs and gastralia, and one phalanx. alexandrae,andElasmosaurus platyurus,aswellasCallawayasaurus colombiensis, from the Upper Cretaceous of Colombia (measurements 4.2. Locality, geologic unit and age of these specimens were taken from Welles, 1943, 1952, 1962). Also, adult elasmosaurids from the WBP were included, particularly the holo- Central part of Marambio Island, Antarctica, about 1550 m south of type of Tuarangisaurus keyesi (measurements from Wiffen and Moisley López de Bertodano Bay. Klb9 unit, López de Bertodano Formation (1986)) and the holotype of Kaiwhekea katiki Cruickshank and Fordyce, (Macellari, 1984), latest Maastrichtian. 2002 (measurements taken directly from the specimen), both from the Maastrichtian of New Zealand. Futabasaurus suzukii,fromtheSantonian 4.3. Ontogenetic observations of Japan, was also included (measurements taken from Sato et al. (2006)). Phylogenetic analysis was not carried out since specimen The studied specimen has cervical centra with tightly fused neural SGO.PV.6523 is very fragmentary, thus, making it only scorable for a arches, without traces of sutures between them. This is considered as in- few characters. dicative of an adult stage (Brown, 1981). On the other hand, the unique For comparison of the SGO.PV.6508 belonging to a young individual recovered phalanx shows a poor ossiﬁcation with a weak periosteal from late Campanian beds of James Ross Island, juvenile representatives surface. Such a condition was described by Caldwell (1997) as a feature from the Upper Cretaceous of North America were selected including of adult limb morphology, because ossiﬁcation is generally delayed. the type materials of ‘Cimoliasaurus maccoyi’, ‘Leurospondylus ultimus’, Based on these observations, we consider specimen SGO.PV.6523 as a and ‘Aphrosaurus furlongi’ (measurements from Brown, (1913); near-adult individual. This allows direct comparisons with the species Welles, (1943); Kear, (2005)) currently considered as indeterminate Aristonectes parvidens Cabrera (1941), K. katiki Cruickshank and elasmosaurids due to their ontogenetic stage, which allows assignations Fordyce (2002), Mauisaurus haasti Hector (1874) (referred specimen to be questioned (Kear, 2002; O'Keefe and Hiller, 2006; Sato and Wu, CM Zfr 115), and T. keyesi Wiffen and Moisley (1986), all of them from 2006). In addition, young individuals from the WBP include: 1) the the Upper Cretaceous of the WBP and described as adult or near-adult type material of ‘Morturneria seymourensis’ (measurements from specimens. SGO.PV.6523 can be also compared with other Upper Chatterjee and Small, (1989)) from the late Maastrichtian of Antarctica, Cretaceous adult elasmosaurids from Argentina and New Zealand 2) a young indeterminate elasmosaurid from the late Campanian (Beta where the scapula is preserved. Member) of James Ross Island (measurements from O'Gorman, (2012)), 3) the young specimen SGO.PV.260 from the late Maastrichtian 4.4. Cervical vertebrae of central Chile, referred to Aristonectes sp. by Otero and O'Gorman (2013), and 4) the juvenile specimen CM Zfr 115 referred to Mauisaurus Nine incomplete vertebrae are preserved, with six of them preserv- haasti from the late Campanian of New Zealand (measurements from ing the centrum or at least part of it, while two additional centra are Hiller et al. (2005)). represented by fragments of prezygapophyses that do not match any Finally, SGO.PV.6579 was directly compared with specimens of the other vertebra. A fragment of a posterior cervical centrum is preserved genus Aristonectes (SGO.PV.957, adult, and SGO.PV.260, juvenile) in the block that hosts the scapula, followed by a last preserved centrum

Fig. 2. Elasmosauridae gen. et sp. indet. (SGO.PV.6523). Marambio Island, Antarctica. López de Bertodano Formation, Klb9, late Maastrichtian. Left view of the preserved centra. A, posterior cervical centra hosted in the block of the scapula (c5, left). B, posterior cervical vertebra (c4). C, D, fragmentary, mid-cervical vertebrae (c2 and c3 from right to left, respectively). E, anteriormost cervical vertebra preserved (c1). Scale bar represents 50 mm. in the same block. An isolated portion of a centrum lacking the neural on their respective lengths (Table 1), being also named c1 to c5 from arches and cervical ribs was also collected but not ﬁgured here since it the anteriormost to the posterior element. Neural spines have a vertical is not informative. The pedicels for the neural arches are thin in all groove along their anterior, and dorsal posterior borders, with a cases, indicating that no rib attachment is present in the neural arch, conserved depth along each groove (Fig. 3). In the anterior groove two thus, discarding them as pectoral or dorsal centra. Vertebrae including lateral keels are developed on each side, with the anterior left one both neural spines and part of the centrum have been arranged based being slightly more prominent than the right one. The anteriormost

Fig. 3. Elasmosauridae gen. et sp. indet. (SGO.PV.6523). Anteriormost cervical vertebra c1. A, anterior view. B, dorsal view. C, posterior view showing its transverse section. D, cervical vertebra c2 in anterior view. E, posterior view of c2 and a fragment of the immediately posterior neural arch in anatomical position. F, cervical vertebra c3 in anterior view. G, posterior view of c3 and a fragment of the immediately posterior neural arch in anatomical position. H, cervical vertebra c4 in posterior view showing its transverse section. I, detail of the neural arch of c1. Scale bars represent 50 mm, and 10 mm in I.

Fig. 4. Elasmosauridae gen. et sp. indet. (SGO.PV.6523). A, detail of the posterior cervical c4 in left dorsoposterior view, for observation of the cervical rib facet. B, right lateral view of the posterior cervical centrum c5. C, dorsal view of c5. D, right lateral view of the right scapula. E, right lateral outline of the right scapula based on the preserved portions and the cast in the sandstone matrix. F, posterior view of the right scapula. G, cross section view of rib and gastralium hosted in the block of the scapula. H, ventral view of the previous grastralium. I, isolated phalanx in dorsal view. J, distal view. K, lateral view. Scale bars equal 50 mm.

vertebra (c1) is the best preserved cervical (Fig. 3A–C), although the centrum. The latter is unusually large and reaches 157°, conferring a neural spine lacks its dorsal end (Fig. 3B). This centrum has the left slightly triangular outline to the transverse section of the centrum. part of its posterior articular facet absent, allowing a view of its The anterior and posterior articular facets are larger than the rest of transverse outline in posterior view (Fig. 3C), which has an obtuse the centrum, and they have bilobed outlines with a ventral notch, angle between the vertical neural spine and the medial surface of the which is typical of the Elasmosauridae (Gasparini et al., 2003). The

Table 1 Measurements of vertebral centra in the studied specimens. Absence of measurements is denoted with a line, while non-applicable indexes are denoted by ‘NA’. Vertebral Length Index (VLI) = L / (0.5 ∗ (H + B)) from Brown (1981); index of ratio between height and length (HI) = (100 ∗ H/L) and index of ratio between breadth and length (BI) = (100 ∗ B/L) from Welles (1952).

Length Height Breadth VLI HI BI

SGO.PV.6523 Cervicals 64.3 62.4 95.8 81.289507 97.0451011 148.989114 66 –– – – – 68.5 82 75.5 86.984127 119.708029 110.218978 74.2 –– – – – Pectoral 68.5 73.3 – NA NA NA SGO.PV.6508 Cervical 52.2 39.5 54.6 110.945802 75.6704981 104.597701

4.7. Phalanx SGO.PV.6579: Fragmentary postcranial skeleton preserving eight fragmentary caudal centra, two articular propodial heads (likely A single phalanx was recovered directly associated with the other femora), an epipodial (likely a ﬁbula), ventral portion of the right remains. This is elongated and massive, with a polygonal articular ilium, partial left pubis, and several rib portions.

4.13. Caudal centra

Eight incomplete portions of caudal centra were recovered. The most complete centra (Fig. 6A–H) show that these are broader than high and higher than long. In lateral view the rib facets occupy almost the whole length of the centrum, leaving a small gap before the posterior articular face. Rib facets are oval and excavated into the centra. In ventral view, one central foramen can be observed. The posteroventral margin of the centra has two well-marked, semicircular facets for the haemal arches, confirming its caudal position. In dorsal view, these centra have large facets for the pedicels of each neural arch. These are massive, anteriorly broader and reaching the margin of the anterior articular face, while its posterior end is reduced in breadth giving a triangular outline to the pedicelar facet, and does not reach the posterior articular margin of the centrum. The anterior articular face has a distinctive octagonal outline defined by the surface of the neural canal, the surface between the neural arch pedicels and the rib facets, the rib facet itself, and the flat ventral surface of the centrum between the keels that rise from the facets for the haemal arches (Fig. 6A, E). This octagonal articular outline has been found to be diagnostic of the genus Aristonectes (Otero et al., 2012; O'Gorman et al., 2013), although the caudal vertebrae in the latter genus are notoriously broader than high, while the vertebrae of the SGO.PV.6579 are slightly broader than high. Additional materials belong to fragments of caudal centra with similar features (Fig. 6I, J).

4.14. Propodials

Two different proximal portions were recovered (Fig. 6K, L). These are fragmentary, although they do show the longitudinal section of the articular head which has a circular outline, thus indicating that the articular head was hemispherical. Each articular head has a distal constriction, indicating that the latter was prominent with respect to the diaphysis, as occurs in the lectotype of Mauisaurus haasti (Hector, 1874; Welles, 1962), in the propodials of Aristonectes sp. (Otero et al., 2012), as well as in another Antarctic specimen (ZPAL R.8/11) previously described by Fostowicz–Frelik and Gaździcki (2001). Considering the associated pelvic portions and caudal vertebrae preserved in SGO.PV.6579, these articular heads are likely part of each femur.

4.15. Epipodial

A single fragmentary epipodial was recovered (Fig. 6M), which is bro- ken in sagittal section and also missing its lateral half. The preserved portion (medial half) is as broad as it is long, thus indicating that the complete epipodial was broader than long. The proximal articular facet is recognized by being comparatively thicker than the distal facet. The ﬁrst has a rounded border that articulates with the lateral facet of the propodial, while the internal margins have a medial concavity that sepa- rates the proximal facet from the distal one. Such a concavity is typically

Fig. 5. Elasmosauridae indet. (SGO.PV.6508). James Ross Island, Antarctica. Santa Marta placed in the axial margin of the epipodials. Also, the straight distal facet Formation, Gamma member, late Campanian. Cervical vertebra of a verylong-necked indi- is large enough for articulation with a centrale element, while in the case vidual. A, anterior view. B, dorsal view. C, ventral view. D, right lateral view. Scale bar of radius/tibia, the facet for the centrale is more reduced (Broili, 1930; equals 50 mm. Welles, 1952). Based on this, the epipodial likely belongs to an element placed in the posterior half of the limb. Since the associated postcranial elements of the SGO.PV.6579 are caudal and pelvic portions, it is likely that the epipodial belongs to a ﬁbula rather than an ulna. 4.12. Ontogenetic observations 4.16. Ilium The specimen has caudal centra bearing ribs unfused to the centra. Additionally, the preserved portions of the ilium and pubis are smaller The ventral portion of the right ilium is preserved (Fig. 6N). This is than other known juvenile specimens of Aristonectes (particularly the very massive and recurved. Its ventral articular face is incomplete, but SGO.PV.260, described by Otero et al. (2012)). Based on these facts, allows evaluating the ventral length of the bone. The dorsal portion is we consider this specimen to be a juvenile individual following the lost, but it is possible to see a medial reduction of the shaft section in criteria of Brown (1981). thepartwheretheboneisrecurved.

Fig. 6. Aristonectinae gen. et sp. indet. (SGO.PV.6579) James Ross Island, Antarctica. Santa Marta Formation, Gamma member, late Campanian. A, E, caudal centra in anterior view. B, F, left lateral view. C, G, ventral view. D, H, dorsal view. I, fragmentary caudal centrum in right lateral view. J, fragment of a caudal centrum in ventral view. K, L, articular heads of two different propodials, likely the femora. Estimated diaphysis outline based on the Antarctic specimen ZPAL R.8/6 described by Fostowicz–Frelik and Gaździcki (2001). M, pre-axial portion of epipodial (likely a ﬁbula). N, sagittal section view of the epipodial. O, ventral portion of the right ilium in posterior view. P, ventral portion of the right ilium of Aristonectes sp. (SGO.PV.260, juvenile specimen) in posterior view. Q, articular portion of the left pubis of SGO.PV.6579 in dorsolateral view. R, left pubis of Aristonectes sp. (SGO.PV.260, juvenile specimen) in dorsolateral view. Scale bars equal 50 mm.

4.17. Pubis 5. Discussion

A large amount of scattered bone fragments were collected and later 5.1. Comparison of SGO.PV.6523 with other elasmosaurids from the WBP re-assembled (Fig. 6M). These include a very fragmentary articular face of a probable right pubis, as well as the acetabular portion of the left Morphological characters of SGO.PV.6523 include the presence of an pubis. This latter bears an oval articular face for the femoral head. The anterior and posterior groove on the edge of the neural spines at least on rest of the bone is poorly preserved, lacking most of its perimeter, mid-to-posterior cervical vertebrae (its presence on anterior cervicals although it is possible to see the distinctive dorsal (internal) view of cannot be veriﬁed since the latter are not preserved). A similar condi- the pubis surface which is slightly concave. tion is observed in posterior cervicals of specimen SGO.PV.260 referred

Fig. 7. Comparison between scapulae of adult elasmosaurids from the Upper Cretaceous of the WBP. A, Aristonectes sp. (SGO.PV.957, late Maastrichtian of central Chile), right scapula in lateral view. B, Elasmosauridae gen. et sp. indet. (SGO.PV.6523, late Maastrichtian of Marambio Island, Antarctica), right scapula in lateral view. C, Elasmosauridae indet. (MCS-4, late Campanian–early Maastrichtian of Argentina), right scapula in lateral view (modified from Gasparini and Salgado (2000)). D, aff. Mauisaurus sp. (ZPAL R.8/11, early Maastrichtian of Marambio Island, Antarctica), left scapula in medial view (modified from Fostowicz–Frelik and Gaździcki, 2001). E, Mauisaurus haasti Hector (CM Zfr 115, late Campanian of New Zealand), left scapula in medial view (modified from Hiller et al. (2005)). F, Elasmosauridae indet. (CM Zfr 145, late Maastrichtian of New Zealand), left scapula in medial view (modified from Hiller and Mannering (2005)). Scale bar equals 50 mm.

Although SGO.PV.6523 bears apparently unique morphologic 5.5. Specimen SGO.PV.6579 characters, its fragmentary condition prevents accurate comparisons, particularly with other records from Marambio Island comprising The presence of anterior caudal centra much broader than high and different anatomical portions, such as the skull and anterior neck of higher than large, with an octagonal articular outline, has been regarded ‘Morturneria seymourensis’ (Chatterjee and Small, 1989). as a diagnostic feature of the genus Aristonectes (Gasparini et al., 2003: fig 3I, J; O'Gorman et al., 2010; Otero et al., 2012:fig. 5). The studied 5.2. Functional aspects on the neck of SGO.PV.6523 material SGO.PV.6579 has different proportions with respect to the diagnostic anterior caudals of Aristonectes, with a breadth slightly larger The presence of a groove along the anterior and posterior edge of the than the height. Since SGO.PV.6579 has ventral facets for the haemal cervical neural spines is a feature poorly described in known plesio- arches, this verifies their anatomical position in a posterior position saurs. Anterior grooves in neural spines are present in posterior caudal with respect to the diagnostic anterior caudals (which are comparative- and dorsal vertebrae of the Jurassic cryptoclidid Muraenosaurus ly broader), although the material still retains the distinctive octagonal (Andrews, 1910:figs. 51, 52 and 54), but the grooves fade into the dorsal articular outline. Sub-triangular, pedicelar facets for the neural arches portion of the spines. Other elasmosaurids have distinctive morphol- such as those present in the caudal vertebrae of SGO.PV.6579 have ogies on the edges of neural spines. Dorsal pits are present in posterior been previously described in middle to posterior dorsal vertebrae of a cervicals of H. alexandrae (Welles, 1943: plate 27). Similar morphologies specimen from late Maastrichtian beds of Marambio Island referred to are also present in F. suzukii, which has an anterior pit and a posterior Aristonectes cf. parvidens by O'Gorman et al. (2013). On the other swelling in the dorsal portion of the posterior cervical neural spines hand, such features on the caudal vertebrae are also present in specimen (Sato et al., 2006:fig. 5C, D). This evidence suggests that the neural CM Zfr 115 from the late Campanian of New Zealand (Hiller et al., 2005), spines of posterior vertebrae in elasmosaurids are highly distinctive which surely represents a different taxon that possess a very long neck and can be taxonomically informative. Also, these portions allow infer- with more than 60 vertebrae, placing it among the non-aristonectine ences to be made about the rigidity of the posterior neck. Analog mus- elasmosaurids. Also, the posterior epipodial (likely a fibula) with a cular attachments in birds and sauropods (Wedel and Sanders, 2002: concave pre-axial margin is a feature previously described in other fig. 2) show that neural spines can develop large interspinal muscles specimens of Aristonectes (Otero et al., 2012). In addition, the distinctive related to the ability of curving the neck dorsally as it occurs in the massive, ventral portion of the ilium is a feature shared with the juve- sauropod Apatosaurus. Nevertheless, in the latter, the interspinal space nile specimen SGO.PV.260, referred to the genus Aristonectes (Otero is large, contrary to the very reduced space between neural spines of and O'Gorman, 2013)(Fig. 6K, L), while the partial portion of the SGO.PV.6523, which also has deep grooves in the anterior and posterior pubis of SGO.PV.6579 is also consistent with specimen SGO.PV.260 margin of the neural spines, indicating a strong muscular attachment (Fig. 6M, N). Most of the morphologies described here are very similar but scarce possibilities for dorsoventral movement of the posterior to those present in the genus Aristonectes based on specimens from neck. This is also consistent with the large semi-cylindrical facets for ar- the late Maastrichtian of the southeastern Pacific, while the presence ticulation of the postzygapophyses, which allow interlocking between of caudal vertebrae similar to those of non-aristonectine elasmosaurids successive cervicals. Based on this, it is likely that the elasmosaurid from the late Campanian of New Zealand, such as CM Zfr 115, indicates SGO.PV.6523 possessed a stiff posterior portion of the neck, with that this could be a plesiomorphic feature. Finally, the large gap reduced movement. between this new Antarctic record (SGO.PV.6508) and the records of Aristonectes from central Chile suggests that both taxa can be narrowly 5.3. Associated fauna and environment of the SGO.PV.6523 related, but it cannot be assured that they belong to the same genus, especially considering the widespread distribution of the family in the This specimen was recovered completely isolated from any other ver- Southern Hemisphere during the end of the Cretaceous (Chatterjee tebrate remains. The fossil-bearing unit was traced over a large area while and Small, 1989; Cruickshank and Fordyce, 2002; Gasparini et al., looking for additional remains. These findings include cranial material of a 2003; O'Gorman et al., 2013). Based on these facts, specimen large mosasaurid (presently being studied by the authors), isolated teeth SGO.PV.6579 from late Campanian beds of James Ross Island (Gamma of odontaspidid sharks, scattered but frequent dental plates of indetermi- member) is here referred to an indeterminate aristonectine. In addition, nate callorhynchid fishes and dental plates of Callorhinchus torresi (Otero the material from Marambio Island described by Fostowicz–Frelik and et al., 2013). Additional remains of elasmosaurid plesiosaurs were found Gaździcki (2001) was found in the lower strata of the López de separated by several tens of meters, which allow a possible mixing of el- Bertodano Formation (Klb2 unit), which are assigned by Crame et al. ements from different individuals to be discarded. The common presence (2004) to the early Maastrichtian. Also, the material probably belongs of frequent dental plates of holocephalians and odontaspidid teeth to a single juvenile individual and includes among other remains suggests a shallow shelf environment (Stahl, 1999; Compagno, 2001). articulated caudal vertebrae (ZPAL R.8/1–4), an epipodial, probably a tibia (ZPAL.R8/13), and a femur with hemispherical articular head 5.4. Specimen SGO.PV.6508 (ZPAL R.8/6), all of them coincident in shape and size with the respective anatomical elements preserved in SGO.PV.6579. Also, the late Cam- The presence of very-long necked elasmosaurids (with cervical indi- panian age of the latter and the early Maastrichtian age of ZPAL.R8/1–4, ces in the range of representatives from the Upper Cretaceous of North 6 and 13, strongly suggest that both specimens belong to the same America) in the Campanian–Maastrichtian of the Southern Hemisphere taxon. Finally, the outline of the scapula of ZPAL.R8/13 is indeed coinci- is restricted to finds in New Zealand (Welles and Gregg, 1971; Wiffen dent with that of Aristonectes sp. (Fig. 7A, D), but has a much smaller and Moisley, 1986; Hiller et al., 2005) and Argentina (Gasparini et al., size. Considering the new information, it is possible that the remains 2001:fig. 3), but are very scarce in Chile (RAO, pers. obs.). Also, the re- described by Fostowicz–Frelik and Gaździcki (2001) belong to the cords from Antarctica include long-necked elasmosaurids referred to same taxon of the SGO.PV.6579, but at this moment no generic or specif- the genus Mauisaurus by Martin et al. (2007) from Maastrichtian beds ic determination can be provided. of Vega Island, although the cervicals of the specimen were not recovered. O'Gorman (2012) also described the oldest elasmosaurid from 5.6. Associated fauna and environment of SGO.PV.6523 Coniacian–Campanian beds of James Ross Island, including a juvenile specimen with several cervical vertebrae. The studied specimen verifies Previous records of vertebrates from Santa Marta Cove on James Ross the presence of very-long necked elasmosaurids during the late Island include cartilaginous and bony fishes (Kriwet et al., 2006 and ref- Campanian on the James Ross Island. erences therein), as well as dinosaurs (lithostrotians, ankylosaurs, and

Fig. 8. Plots obtained with the bivariate graphic analysis. The dark ellipse encloses the plots of the indeterminate elasmosaurid SGO.PV.6523. A, HI vs BI in adults. B, VLI vs BI in adults. C, VLI vs HI in adults. Plots of the indeterminate elasmosaurid SGO.PV.6508. D, HI vs BI in juveniles. B, VLI vs BI in juveniles. C, VLI vs HI in juveniles.

Please cite this article as: Otero, R.A., et al., Additions to the diversity of elasmosaurid plesiosaurs from the Upper Cretaceous of Antarctica, Gond- wana Research (2013), http://dx.doi.org/10.1016/j.gr.2013.07.016 12 R.A. Otero et al. / Gondwana Research xxx (2013) xxx–xxx that of CM Zfr 115 referred to Mauisaurus haasti, nearly 101, although Evolution of the Antarctic Biota. Geological Society (London), special publication, 47, pp. 107–119. the latter is a near-adult specimen. The results of bivariate graphic Broili, F., 1930. Plesiosaurierreste von der Insel Quiriquina. Neues Jahrbuch Mineralogie analysis support SGO.PV.6508 as being a juvenile individual of a very Geologie Paläontologie Beilage-Band (B) 63, 497–514. long-necked elasmosaurid. Brown, B., 1913. A new plesiosaur, Leurospondylus, from the Edmonton Cretaceous of Alberta. Bulletin of the American Museum of Natural History 32, 605–615. Brown, D.S., 1981. The English Upper Jurassic Plesiosauroidea (Reptilia) and a review of 6. Conclusions the phylogeny and classification of the Plesiosauroidea. Bulletin of the British Museum of Natural History (Geology) 35, 253–347. Cabrera, A., 1941. Un Plesiosaurio nuevo de Cretácico del Chubut. Revista del Museo de la The studied material SGO.PV.6523 represents an unusual indetermi- Plata 2, 113–130. nate elasmosaurid from late Maastrichtian strata of the López de Caldwell, M., 1997. Limb osteology and ossification patterns in Cryptoclidus (Reptilia: Bertodano Formation exposed on Marambio Island. Despite this being Plesiosauroidea) with a review of sauropterygian limbs. Journal of Vertebrate – a fragmentary specimen, it represents a novel, relatively small animal Paleontology 17, 295 307. Casamiquela, R., 1969. La presencia en Chile del género Aristonectes Cabrera with a probably rigid neck and a scapula very different from the scapula (Plesiosauria), del Maestrichtiense del Chubut, Argentina. Edad y carácter de la known in any Weddellian elasmosaurid. The fragmentary condition of transgresión ‘Rocaense’.JornadasGeológicasArgentinasNo4(1),199–213 the material prevents direct comparison with other taxa, while the ((Mendoza), Actas). Cerda, I.A., Carabajal, A.P., Salgado, L., Coria, R.A., Reguero, M.A., Tambussi, C.P., Moly, J.J., cervical features and the bivariate graphic analysis suggest that this 2012. The first record of a sauropod dinosaur from Antarctica. Naturwissenschaften can belong to a form within Aristonectinae, based on the cervical 99, 83–87. proportions and the presence of an incipient left anterior flank in the Chatterjee, S., Creisler, B.S., 1994. Alwalkeria (Theropoda) and Morturneria (Plesiosauria), new names for preoccupied Walkeria Chatterjee, 1987 and Turneria Chatterjee and neural spines, a feature that partially matches the cervical morphologies Small, 1989. Journal of Vertebrate Paleontology 14, 142. observed in Aristonectes sp. (SGO.PV.957) from late Maastrichtian strata Chatterjee, S., Small, B.J., 1989. New plesiosaurs from the Upper Cretaceous of Antarctica. of central Chile; Nevertheless, SGO.PV.6523 surely represents a different In: Crame, J.M. (Ed.), Origins and Evolution of the Antarctic biota. Geological Society, London, Special Publication, 47, pp. 197–215. taxon based on the much smaller adult size. Chatterjee, S., Zinsmeister, W., 1982. Late Cretaceous marine vertebrates from Seymour In addition, the studied material from James Ross Island Island. Antarctic Journal of the United States 17, 66. (SGO.PV.6508) shows the presence of very-long necked elasmosaurids Compagno, L.J.V., 2001. FAO species catalogue. Sharks of the world. An annotated and illustrated catalogue of sharks species known to date. Part 1. Hexanchiformes to during the late Campanian, which to date are completely unknown in Lamniformes. FAO Fishery Synopsis, 125 (269 pp.). Upper Cretaceous units of the southeastern Pacific (Chile), but known Cope, E.D., 1869. Synopsis of the extinct Batrachia, Reptilia and Aves of North America. in Argentinean units of the same age. Their common presence in Transactions of the American Philosophical Society (new series) 14, 1–252. Argentina, Antarctica, and New Zealand during the late Campanian– Coria, R.A., Tambussi, C., Moly, J.J., Santillana, S., Reguero, M., 2007. Nuevos restos de Dinosauria del Cretácico de las islas James Ross y Marambio, Peninsula Antártica. VI Maastrichtian and their posterior absence in the southeastern Pacific Simposio Argentino y III Latinoamericano sobre Investigaciones Antárticas (http:// during the late Maastrichtian, raise questions about paleogeographic www.dna.gov.ar/ciencia/santar07/cd/pdf/geore804.pdf). or environmental changes that could have affected their distribution Coria, R.A., Moly, J.J., Reguero, M.A., Santillana, S., Marenssi, S., 2013. Anewornithopod (Dinosauria; Ornithischia) from Antarctica. Cretaceous Research 41, 186–193. during this period. Crame, J.A., Francis, J.E., Cantrill, D.J., Pirrie, D., 2004. Maastrichtian stratigraphy of Finally, additional material from James Ross Island allows the identi- Antarctica. Cretaceous Research 25, 411–423. fication of the first remains of an indeterminate aristonectine in late Cruickshank, A.R., Fordyce, R.E., 2002. A new marine reptile (Sauropterygia) from New Zealand: further evidence for a Late Cretaceous austral radiation of cryptocleidid Campanian strata of Antarctica, while suggesting the presence of the plesiosaurs. Palaeontology 45, 557–575. same taxon also in early Maastrichtian strata of the López de Bertodano D'Angelo, J., Novas, F.E., Lirio, J., Isasi, M., 2008. Primer registro de Polycotylidae Formation on Marambio Island. This is the oldest known record of this (Sauropterygia, Plesiosauroidea) del Cretácico Superior de Antártida. In: Calvo, J.O., Juarez Valieri, R., Porfifi, J.D., Dos Santos, D. (Eds.), III Congreso Latinoamericano de sub-family, widely distributed within the WBP, but previously restricted Paleontología de Vertebrados, Libro de Resúmenes, p. 72. Neuquén, Argentina. only to late Maastrichtian beds of Antarctica, Argentina, Chile, and New de Blainville, H.D., 1835. Description de quelques espèces de reptiles de la Californie, Zealand. The three new specimens studied here represent new informa- précédée de l'analyse d'un système général d'Erpetologie et d'Amphibiologie. Nouvelles Annales du Muséum (National) d'Histoire Naturelle, Paris 4, 233–296. tion about the diversity of Upper Cretaceous Antarctic plesiosaurs. Del Valle, R.A., Medina, F., Gasparini, Z., 1977. Nota preliminar sobre el hallazgo de reptiles fósiles marinos del suborden Plesiosauria en las islas James Ross y Vega, Antártida. Acknowledgments Contribución del Instituto Antártico Argentino 212, 1–13. Fostowicz−Frelik, Ł., Gaździcki, A., 2001. Anatomy and histology of plesiosaur bones from the Late Cretaceous of Seymour Island, Antarctic Peninsula. In: Gaździcki, A. (Ed.), This research was supported by the Antarctic Ring Project (Anillos Palaeontological Results of the Polish Antarctic Expeditions. Part III. Palaeontologia de Ciencia Antártica ACT-105, Conicyt-Chile). We express our gratitude Polonica, 60, pp. 7–32. to the Armada de Chile and the crew of the Icebreaker AP Almirante Gasparini, Z., Goñi, R., 1985. Los plesiosaurios cretácicos de América del Sur y del continente antártico. Congresso Brasileiro de Paleontología, No. 8 (Río de Janeiro). Óscar Viel, for the professional logistics and goodwill that made this Coletanea de Trabalhos Paleontológicos, Serie Geologie, 27, pp. 55–63. field campaign possible. R.E. Yury-Yáñez was funded by a master's Gasparini, Z., Salgado, L., 2000. Elasmosáuridos (Plesiosauria) del Cretácico Tardío del – degree CONICYT-Chile scholarship from the Programa de Formación norte de Patagonia. Revista Española de Paleontología 15, 13 21. Gasparini, Z., Del Valle, R.A., Goñi, R., 1984. An Elasmosaurus (Reptilia, Plesiosauria) of the de Capital Humano Avanzado. Our thanks also go to E. Fordyce Upper Cretaceous in the Antarctic. Contribuición del Instituto Antártico Argentino (University of Otago, Dunedin, New Zealand) and P. Scofield 305, 1–24. (Canterbury Museum, Christchurch, New Zealand) for granting access Gasparini, Z., Casadío, S., Fernández, M., Salgado, L., 2001. Marine Reptile from the Late Cre- taceous of Northern Patagonia. Journal of South American Earth Sciences 14, 51–60. during May, 2013 to the holotype of K. katiki and CM Zfr 115, respective- Gasparini, Z., Bardet, N., Martin, J.E., Fernández, M., 2003. The elasmosaurid plesiosaur ly. Andrea Llanos (Departamento de Producción Agrícola, Facultad de Aristonectes Cabrera from the latest Cretaceous of South America and Antarctica. Ciencias Agronómicas, Universidad de Chile) is especially acknowl- Journal of Vertebrate Paleontology 23, 104–115. fi Hector, J., 1874. On the fossil reptiles of New Zealand. Transactions of the New Zealand edged for nding one of the studied specimens. Thanks to J. Le Roux Institute 6, 333–358. (Departamento de Geología, Universidad de Chile) for the stylistic Hiller, N., Mannering, A., 2005. An unusual new elasmosaurid plesiosaur (Sauropterygia) review of the english. RAO, SSA, and CSG are currently supported by from the Upper Haumurian (Maastrichtian) of the South Island, New Zealand. Memoirs of the Queensland Museum 51, 27–37. the Proyecto Domeyko II UR-C12/1 grant of the Universidad de Chile. Hiller, N., Mannering, A., Jones, C., Cruickshank, A., 2005. The nature of Mauisaurus haasti Hector, 1874 (Reptilia: Plesiosauria). 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