Rodrigo A. Otero

Aristonectes quiriquinensis, sp. nov., A New Highly Derived Elasmosaurid from the Upper Maastrichtian of Central Chile

ABSTRACT This paper describes a new species of elasmosaurid plesiosaur, Aristonectes quiriquinensis, sp. nov., based on a partial skeleton recovered from upper Maastrichtian beds of the Quiriquina Formation of central Chile. The material described here consists of two skeletons, one collected near the village of Cocholgue, and a second juvenile specimen from Quiriquina Island. Prior to these finds, Aristonectes was viewed as a monospecific genus, including only the enigmatic Aristonectes parvidens, the holotype of which consists of an incomplete skull and incomplete postcranium. Other material referred to the genus includes an incomplete juvenile skull and other postcranial material from the upper Maastrichtian of Antarctica, as well as a partial skull from the Quiriquina Formation of central Chile. The relationships of Aristonectes have been controversial, with competing theories assigning the genus to Cryptoclididae, Elasmosauridae, and Aristonectidae; however, there is a developing consensus that Aristonectes is a derived elasmosaurid, and this paper gives strong evidence for this view. Comparison of the specimen here studied with the holotype of A. parvidens demonstrates that A. quiriquinensis is a distinct species. The completeness of the adult skeleton allows the first confident size estimates for adult Aristonectes. It is a large plesiosaurian with a relatively large skull with numerous homodont teeth, a moderately long and laterally compressed neck, and relatively narrow trunk, with slender and elongate forelimbs. The two specimens are restricted to the upper Maastrichtian of central Chile, posing questions concerning the austral circumpolar distribution of different elasmosaurids towards the end of the Cretaceous.

Eocene Birds from the Western Margin of Southernmost South America

Abstract This study presents the first record of Eocene birds from the western margin of southernmost South America. Three localities in Magallanes, southern Chile, have yielded a total of eleven bird remains, including Sphenisciformes (penguins) and one record tentatively assigned to cf. Ardeidae (egrets). Two different groups of penguins have been recognized from these localities. The first group is similar in size to the smallest taxa previously described from Seymour Island, Marambiornis Myrcha et al., 2002, Mesetaornis Myrcha et al., 2002, and Delphinornis Wiman, 1905. The second recognized group is similar in size to the biggest taxa from Seymour Island; based on the available remains, we recognize the genus Palaeeudyptes Huxley, 1859, one of the most widespread penguin genera in the Southern Hemisphere during the Eocene. The stratigraphic context of the localities indicates a certain level of correlation with the geological units described on Seymour Island. The newly studied materials cast more light on the paleobiogeography of the group, extending the known ranges to the South American continent. In addition to the newly discovered birds, the presence of several taxa of elasmobranchs previously recovered exclusively from Eocene beds in the Southern Hemisphere help to clarify the age of the studied localities, widely discussed during the last decades. This paper verifies the presence of extensive Eocene sedimentary successions with fossil vertebrates along the western margin of southern South America, contrary to the previous assumption that such a record is lacking in Chile.

Taxonomic reassessment of Hydralmosaurus as Styxosaurus: new insights on the elasmosaurid neck evolution throughout the Cretaceous

Two extremely-long necked elasmosaurids, AMNH 1495, holotype of Hydralmosaurus serpentinus, and AMNH 5835, previously referred to H. serpentinus, are here reviewed in detail. Unique features of the cervical vertebrae, which are only present on elasmosaurids from the Western Interior Seaway, are recognized based on these specimens and by comparison with penecontemporaneous taxa with biogeographic affinities. Phylogenetic analysis, bivariate graphic analysis of cervical vertebrae proportions, comparisons of different cervical vertebral types, paleobiogeographic distribution and study of the elasmosaurid axial evolution throughout the Cretaceous are here integrated. As a result, at least two separate lineages within the Elasmosauridae are identified by independently acquired extremely-long necks (over 60 cervical vertebrae). First, a still scarcely known lineage is so far represented by the lower Cenomanian Thalassomedon haningtoni, the Turonian Libonectes morgani and close relatives. A second lineage is here defined as a new clade, the Styxosaurinae, which groups the Campanian genera Terminonatator, Styxosaurus (=‘Hydralmosaurus’), Albertonectes and Elasmosaurus, the two latter forming a derived branch that includes the most extreme amniote necks known to date (more than 70 cervical vertebrae). Phylogenetic analysis supports AMNH 1495 and AMNH 5835 as being closely related to Styxosaurus snowii. Therefore, the species Styxosaurus browni is re-validated, while AMNH 1495 is here referred to Styxosaurus sp. This research also recognizes the ‘Cimoliasauridae’ (nomen dubium) as a paraphyletic group but informative of a plesiomorphic cervical vertebral morphology of elasmosaurids which was persistent throughout the whole Cretaceous and from whom aristonectines, styxosaurines and Thalassomedon and close relatives are derived. The genus Hydralmosaurus is recommended for being abandoned.

Alexandronectes zealandiensis gen. et sp. nov., a new aristonectine plesiosaur from the lower Maastrichtian of New Zealand

ABSTRACT A fragmentary plesiosaur skull from lower Maastrichtian levels of the Conway Formation, New Zealand, is redescribed. Originally regarded as pertaining to two separate individuals, we argue that they represent a single individual belonging to a new aristonectine elasmosaurid, Alexandronectes zealandiensis gen. et sp. nov. This new taxon has common morphologies with other aristonectines such as expansion of the pterygoids extending posteriorly beyond the occipital condyle (as observed in Ar. quiriquinensis and probably in Kaiwhekea katiki) and the presence of an ‘A’-shaped squamosal arch in dorsal view. Otherwise, it is distinguished from these latter species by having different paraoccipital processes, a different mandibular glenoid, and an adult skull comparatively smaller than K. katiki and Aristonectes spp. The new taxon is a morphologically intermediate form between the dorsoventrally high skull of K. katiki and the mediolaterally expanded skulls of Aristonectes spp. The studied specimen is the second genus and species and the third report of an aristonectine recovered from lower Maastrichtian beds of New Zealand, emphasizing the diversity of this group in New Zealand and also indicating that aristonectines could include smaller species than those already known.

A new record of an aristonectine elasmosaurid (Sauropterygia, Plesiosauria) from the Upper Cretaceous of New Zealand: implications for the Mauisaurus haasti Hector, 1874 hypodigm

O’Gorman, J.P., Otero, R.A. & Hiller, N., 2014. A new record of an aristonectine elasmosaurid (Sauropterygia, Plesiosauria) from the Upper Cretaceous of New Zealand: implications for the Mauisaurus haasti Hector, 1874 hypodigm. Alcheringa 38, 504–512. ISSN 0311-5518 An indeterminate aristonectine elasmosaurid is recorded from a lower Maastrichtian bed of the Conway Formation, Waipara River, South Island, New Zealand. The described specimen (CM Zfr 104), previously considered part of the hypodigm of Mauisaurus haasti, came from the upper part of the Alterbidinium acutulum biozone, the same zone from which the only well-known aristonectine from New Zealand, Kaiwhekea katiki, is recorded. The cervical vertebrae of CM Zfr 104 have the same distinctive features (i.e., with extremely broad rather than long centra) as those from previously recorded juvenile aristonectines from Argentina, Chile and Antarctica. This new record is congruent with the biogeographic relationships of Cretaceous marine amniotes from the Weddellian Palaeobiogeographic Province (i.e., Patagonia, western Antarctica, New Zealand and southeastern Australia). Therefore, this type of vertebra is regarded as a distinctive feature of the Weddellian aristonectine elasmosaurids. José P. O’Gorman [joseogorman@fcnym.unlp.edu.ar], División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata, Paseo del Bosque s/n., B1900FWA, La Plata, Argentina; [CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas)]; Rodrigo A. Otero [paracrioceras@gmail.com], Red Paleontológica U-Chile. Laboratorio de Ontogenia y Filogenia, Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Av. Las Palmeras 3425, Santiago, Chile; Norton Hiller, [norton.hiller@canterbury.ac.nz], Department of Geological Sciences, University of Canterbury, PB 4800, Christchurch, 8001, New Zealand and Canterbury Museum, Rolleston Avenue, Christchurch, New Zealand, 8013.

A new species of chimaeriform (Chondrichthyes, Holocephali) from the uppermost Cretaceous of the Lopez de Bertodano Formation, Isla Marambio (Seymour Island), Antarctica

Abstract We describe a new chimaeriform fish, Callorhinchus torresi sp. nov., from the uppermost Cretaceous (late Maastrichtian) of the López de Bertodano Formation, Isla Marambio (Seymour Island), Antarctica. The material shows it is distinct from currently known fossil and extant species of the genus, whereas the outline of the tritors (abrasive surfaces of each dental plate) shows an intermediate morphology between earlier records from the Cenomanian of New Zealand and those from the Eocene of Isla Marambio. This suggests an evolutionary trend in tritor morphology in the lineage leading to modern callorhynchids, during the Late Cretaceous-Palaeogene interval.

Reassessment of the upper Maastrichtian material from Chile referred to Mauisaurus Hector, 1874 (Plesiosauroidea: Elasmosauridae) and the taxonomical value of the hemispherical propodial head among austral elasmosaurids

The femoral hemispherical articular head was regarded as autapomorphic of Mauisaurus haasti Hector, 1874 from the upper Campanian of New Zealand. Review of three Maastrichtian taxa, Aristonectes quiriquinensis from Chile, Aristonectes sp. from Antarctica and Kaiwhekea katiki from New Zealand, reveals that the femoral hemispherical head is a common character among aristonectines. This feature can therefore be discarded as an autapomorphy of Mauisaurus haasti. Propodials of A. quiriquinensis are shown to be the same as those in two coeval Chilean specimens previously referred to Mauisaurus sp.; in consequence, these are now referred to A. quiriquinensis. Additionally, specimens referred to A. quiriquinensis allow confirmation that during ontogeny the humerus and the femur change from a flat capitulum in juveniles to hemispherical heads of both the humeri and femora in the adult stage. The evidence shows that the presence of Mauisaurus along the southeastern Pacific margin cannot be verified to date.

A reappraisal of the Late Cretaceous Weddellian plesiosaur genus Mauisaurus Hector, 1874

ABSTRACT Research carried out on austral plesiosaurs from the Weddellian Biogeographic Province in the decade since the last attempt to characterise the New Zealand elasmosaurid, Mauisaurus haasti Hector, 1874 (On the Fossil Reptilia of New Zealand. Transactions and Proceedings of the New Zealand Institute 6: 333–358), has prompted a reappraisal of this taxon and a new consideration of its relationships. The hypodigms used in previous descriptions of the species are shown to include specimens from a number of different taxa, and the defining apomorphy of Mauisaurus, a hemispherical capitulum on the femur, has now been observed in specimens known to belong to different clades. Mauisaurus is now regarded as nomen dubium with possible affinities with the Subfamily Aristonectinae. A re-assessment of the most complete specimen previously assigned to Mauisaurus suggests it is a typical long-necked elasmosaurid closely comparable to Tuarangisaurus keyesi Wiffen and Moisley, 1986 (Late Cretaceous reptiles (Families Elasmosauridae and Pliosauridae) from the Mangahouanga Stream, North Island, New Zealand. New Zealand Journal of Geology and Geophysics 29: 205–252).

Elephant Seal (Mirounga sp.) from The Pleistocene of the Antofagasta Region, Northern Chile

ABSTRACT The genus Mirounga is the largest living member of the Phocidae family (true seals) and includes two species: M. angustirostris and M. leonina. These species exhibit a noticeable antitropical distribution in the Northern and Southern hemispheres, respectively. The evolutionary history of elephant seals, especially in regard to establishing this antitropical pattern, is poorly known. Nearly all fossils of the genus are isolated remains from the Pleistocene of California (M. angustirostris) and South Africa (M. leonina). Here, we describe new fossil material of Mirounga sp. (incomplete maxilla, dentary, and humerus), from the middle to late Pleistocene of Antofagasta Region, northern Chile. This material constitutes the first fossil occurrence of this species in South America and suggests that during part of the Pleistocene, phocids coexisted with otariids along the eastern edge of the South Pacific Ocean, which contrasts with the current biogeographic pattern in this ocean basin, providing new information about the structure of the pinniped community during the Pleistocene of South America.

NEW CHONDRICHTHYANS FROM THE UPPER CRETACEOUS (CAMPANIAN-MAASTRICHTIAN) OF SEYMOUR AND JAMES ROSS ISLANDS, ANTARCTICA

Abstract We present new records of chondrichthyans recovered from strata of Maastrichtian age of the López de Bertodano Formation, Seymour (=Marambio) Island, and from levels of latest Campanian age of the Santa Marta Formation, James Ross Island, both located in the eastern Antarctic Peninsula. The material from Marambio Island comprises an associated assemblage with the first records of an indeterminate odontaspidid different from Odontaspis, as well as the genera Pristiophorus, Squatina, Paraorthacodus, and the species Chlamydoselachus tatere from the López de Bertodano Formation. Also, the studied section provides a well-constrained age for several taxa already recognized in the López de Bertodano Formation only by scattered samples of Maastrichtian age for the first time. The assemblage from Marambio Island is representative of one of the latest environmental conditions during the end of the Cretaceous in the coastal seas of the Larsen Basin before major changes that began after the K/P boundary. In addition, the finds from James Ross Island comprise the southernmost records of the neoselachians Cretalamna sp., Centrophoroides sp., as well as the holocephalans Callorhinchus sp. and an indeterminate rhinochimaerid, extending the occurrence of some of these taxa into the late Campanian, being their oldest record of the Weddellian Biogeographic Province.