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The inner ear of the two higher clades of modern cetaceans (Neoceti) is highly adapted for hearing infrasonic (mysticetes) or ultrasonic (odontocetes) frequencies. Within odontocetes, Platanistoidea comprises a single extant riverine representative, Platanista gangetica, and a diversity of mainly extinct marine species from the late Oligocene onward. Recent studies drawing on features including the disparate tympanoperiotic have not yet provided a consensus phylogenetic hypothesis for platanistoids. Further, cochlear morphology and evolutionary patterns have never been reported. Here, we describe for the first time the inner ear morphology of late Oligocene–early Miocene extinct marine platanistoids and their evolutionary patterns. We initially hypothesized that extinct marine platanistoids lacked a specialized inner ear like P. gangetica and thus, their morphology and inferred hearing abilities were more similar to those of pelagic odontocetes. Our results reveal there is no “typical” platanistoid cochlear type, as the group displays a disparate range of cochlear anatomies, but all are consistent with high-frequency hearing. Stem odontocete Prosqualodon australis and platanistoid Otekaikea huata present a tympanal recess in their cochlea, of yet uncertain function in the hearing mechanism in cetaceans. The more basal morphology of Aondelphis talen indicates it had lower high-frequency hearing than other platanistoids. Finally, Platanista has the most derived cochlear morphology, adding to evidence that it is an outlier within the group and consistent with a >9-Myr-long separation from its sister genus Zarhachis. The evolution of a singular sound production morphology within Platanistidae may have facilitated the survival of Platanista to the present day.

The giant sperm whale (Physeter macrocephalus) and the dwarf (Kogia sima) and pygmy (Kogia breviceps) sperm whales represent the only three extant species of physeteroids. This group has diversified during the Miocene, and the Miocene marine sediments of Patagonia (Argentina) hold one of the most important fossil records of physeteroids. In particular, ‘Aulophyseter’ rionegrensis (Gran Bajo del Gualicho Formation, Miocene), described based on two subcomplete skulls nearly a century ago, has been a problematic taxon because its generic assignation has been questioned in different works. Besides, recent phylogenetic analyses have also failed to recover the putative congeneric sister-group relationship between ‘A.’ rionegrensis and A. morricei (the type species). In this contribution, we re-describe ‘A.’ rionegrensis, evaluate its phylogenetic position and provide a taxonomic review of Aulophyseter. A detailed morphological comparison between ‘A.’ rionegrensis and A. morricei reveals several anatomical differences between them. Phylogenetic analyses recover ‘A.’ rionegrensis as a crown physeteroid, nested within Physeteridae, but not closely related to A. morricei. We provide the new generic name Cozzuoliphyseter gen. nov. for its reception. A preliminary re-assessment of material previously referred to Aulophyseter indicates that A. mediatlanticus, and also historical material of A. morricei, need to be reviewed.

Lower Miocene outcrops from Patagonia (Gaiman Formation, Burdigalian) may reveal more clues for the yet unknown aspects for this period in the evolution of odontocetes. Here, we present the first toothless platanistoid dolphin from the lower Miocene of Patagonia, Dolgopolis kinchikafiforo, gen. et sp. nov. The specimen includes an incomplete skull, with no mandibles or earbones, but sufficiently different from other named odontocetes to propose a new genus and species. Phylogenetic analyses indicated it is a platanistoid of uncertain position within the group, and that it shares some homoplastic characters with physeteroids and ziphioids. Given the absence of defined alveoli and teeth and an inferred moderately short and wide rostrum, we interpreted this new species as most likely a capture suction feeder. Based on our phylogenetic hypothesis, the optimization of feeding strategies recovered raptorial feeding as the plesiomorphic method, and convergent evolution of capture suction feeders in at least four lineages. Platanistoids recorded all feeding strategies during the late Oligocene-early Miocene, although raptorial is the predominant method. This suggests a partitioning of the ecological niches in the early phases of platanistoid evolution, as well as a high diversification of feeding methods previously underestimated for this period. Thus, ecological adaptations have a strong evolutionary pressure in odontocetes communities and should be further explored Fil: Viglino, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Gaetán, Carlos Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina

Factors affecting cetacean preservation and distribution in ancient sedimentary successions are not well understood. Actualistic studies have focused on coastal and deep marine examples, and little is known about taphonomic processes occurring within shelf environments. In this paper, we integrate sedimentological, taphonomic and palaeontological data for the cetacean-bearing lower Miocene Gaiman Formation from Patagonia, Argentina, to analyse which factors affected the distribution and preservation of cetaceans in several localities of the Southwestern Atlantic. Facies analysis shows that the formation represents a transgressive-regressive stratigraphic cycle, with palaeoenvironments including coastal, storm-dominated shoreface, inner shelf embayment and open inner shelf. Cetacean remains show preservation styles varying from isolated elements to articulated specimens, with nearly all remains restricted to both embayment and open marine inner shelf settings. Two fossil cetacean assemblages are recognized: Assemblage A comprises small-sized odontocetes dominated by Platanistoidea, preserved mostly in inner shelf embayment deposits; and Assemblage B comprises large-sized odontocetes and mysticetes, dominated by Physeteroidea and Balaenopteroidea, preserved mostly in open inner shelf deposits. Cetacean preservation style is controlled by a combination of palaeoenvironmental conditions, such as energy and sedimentation rate, and by biological factors, such as cetacean body plan and its impact on carcass buoyancy. Ecological factors may also explain the stratigraphic distribution of cetaceans between coastal and oceanic assemblages. This novel integrative and multidisciplinary analyses improves our knowledge of cetacean taphonomy in shelf environments. Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Viglino, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Farroni, Nicolás D.. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina Fil: Bessone, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina

Modern baleen whales have no adult teeth, whereas dolphins and porpoises have a homodont and polydont dentition, with simplified enamel microstructure. However, archaic cetaceans (archaeocetes and early mysticetes and odontocetes) had a complex and ornamented dentition, with complex enamel microstructure as in terrestrial mammals. This study describes the morphology of teeth and enamel microstructure in two fossil cetaceans from Antarctica: a basilosaurid archaeocete from the La Meseta Formation (middle Eocene); and Llanocetus sp. from the Submeseta Formation (late Eocene), one of the oldest mysticetes known. The two teeth analyzed were lower premolars, with transversely compressed triangular crowns composed of a main cusp and accessory denticles. The enamel microstructure of the basilosaurid and Llanocetus sp. is prismatic with Hunter-Schreger bands (HSB) and an outer zone of radial enamel. In the basilosaurid, the enamel is relatively thin and measures 150–180 μm, whereas in Llanocetus sp. it is considerably thicker, measuring 830–890 μm in the cusp area and 350–380 μm near the crown base. This is one of the thickest enamel layers among cetaceans, extinct and living. Structures resembling enamel tufts and lamellae were observed in both fossils at the enamel-dentine junction (EDJ) and extending along the thickness of the enamel layer, respectively. The presence of HSB and biomechanical reinforcing structures such as tufts and lamellae suggests prominent occlusal loads during feeding, consistent with raptorial feeding habits. Despite the simplification or absence of teeth in modern cetaceans, their ancestors had complex posterior teeth typical of most mammals, with a moderately thick enamel layer with prominent HSB. Fil: Loch, Carolina. University of Otago; Nueva Zelanda Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Kalthoff, Daniela C.. Swedish Museum of Natural History; Suecia Fil: Mörs, Thomas. Swedish Museum of Natural History; Suecia Fil: Fernández, Marta Susana. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina

The application of network methodology in anatomical structures offers new insights on the connectivity pattern of skull bones, skeletal elements and their muscles. Anatomical networks helped to improve our understanding of the water-to-land transition and how the pectoral fins were transformed into limbs via their modular disintegration. Here, we apply the same methodology to tetrapods secondarily adapted to the marine environment. We find that these animals achieved their return to the sea with four types of morphological changes, which can be grouped into two different main strategies. In all marine mammals and the majority of the reptiles, the fin is formed by the persistence of superficial and interdigital connective tissues, like a 'baby mitten', whereas the underlying connectivity pattern of the bones does not influence the formation of the forefin. On the contrary, ichthyosaurs 'zipped up' their fingers and transformed their digits into carpal-like elements, forming a homogeneous and better-integrated forefin. These strategies led these vertebrates into three different macroevolutionary paths exploring the possible spectrum of morphological adaptations., Facultad de Ciencias Naturales y Museo

The contents of the superfamily Platanistoidea, an early-diverging lineage comprising extinct species and a single extant representative of South Asian river dolphin (Platanista gangetica), remain controversial. We describe here a partial skull and associated tympano-periotic bones identified as a new genus and species, Aondelphis talen gen. et sp. nov., collected in the lower levels of the Gaiman Formation (early Miocene), in Patagonia (Chubut Province, Argentina). Aondelphis is the first Patagonian platanistoid species named in almost a century. Phylogenetic analyses suggest Aondelphis talen gen. et sp. nov. and a taxon from New Zealand (cf. Papahu ZMT-73) are basal Platanistoidea sensu lato. Unambiguous synapomorphies related to the ear bones allowed us to determine its phylogenetic position. Aondelphis talen markedly differs from the other well-known early Miocene Patagonian platanistoid Notocetus, suggesting the coexistence of at least two different morphotypes that may have occupied different ecological niches at that time. The putative close relationship with a species from New Zealand indicates there was a rapid diversification and widespread distribution of the group in the Southern Hemisphere during the early Miocene. The description of new species and revision of historical records of Patagonian platanistoids can help shedding light on cetacean assemblages of the Patagonian sea during this epoch. Fil: Viglino, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Gutstein, Carolina. Universidad de Chile; Chile. Consejo de Monumentos Nacionales. Área Patrimonio Natural; Chile Fil: Cozzuol, Mario Alberto. Universidade Federal de Minas Gerais; Brasil Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina

Sperm whales (Physeteroidea) are the basal-most surviving lineage of odontocetes, represented today by just three highly specialized, deep-diving suction feeders. By contrast, extinct sperm whales were relatively diverse, reflecting a major Miocene diversification into various suction feeding and macroraptorial forms. The beginnings of this diversification, however, remain poorly understood. The Atlantic coast of South America provides a crucial window into early physeteroid evolution and has yielded some of the oldest species known from cranial material, Idiorophus patagonicus and Diaphorocetus poucheti – both of which are in need of re-description and phylogenetic reappraisal. Here, we re-examine Diaphorocetus in detail and, in light of its complex taxonomic history, declare it a nomen protectum. Phylogenetically, the species forms part of a polytomy including ‘Aulophyseter’ rionegresis and the two crown lineages (Physeteridae and Kogiidae) and demonstrates that facial asymmetry and a clearly defined supracranial basin have characterized this lineage for at least 20 Ma. With a total body length of 3.5–4 m, Diaphorocetus is one of the smallest physeteroids yet known. Its cranial morphology hints at an intermediate raptorial/suction feeding strategy and it has a moderately developed spermaceti organ and junk. Fil: Paolucci, Florencia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Fernández, Marta Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Université de Liège; Bélgica Fil: Marx, Felix G.. Université de Liège; Bélgica. Monash University; Australia Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina

Modern baleen whales (Mysticeti), the largest animals on Earth, arose from small ancestors around 36.4 million years ago (Ma). True gigantism is thought to have arisen late in mysticete history, with species exceeding 10 m unknown prior to 8 Ma. This view is challenged by new fossils from Seymour Island (Isla Marambio), Antarctica, which suggest that enormous whales once roamed the Southern Ocean during the Late Eocene (c. 34 Ma). The new material hints at an unknown species of the archaic mysticete Llanocetus with a total body length of up to 12 m. The latter is comparable to that of extant Omura´s whales (Balaenoptera omurai Wada et al. 2003), and suggests that gigantism has been a re-occurring feature of mysticetes since their very origin. Functional analysis including sharpness and dental wear implies an at least partly raptorial feeding strategy, starkly contrasting with the filtering habit of living whales. The new material markedly expands the size range of archaic mysticetes, and demonstrates that whales achieved considerable disparity shortly after their origin. Fil: Marx, Felix G.. Royal Belgian Institute of Natural Sciences. Directorate Earth and History of Life; Bélgica. Monash University; Australia. Museums Victoria. Geosciences; Australia Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Evans, Alistair R.. Monash University; Australia. Museums Victoria. Geosciences; Australia Fil: Fordyce, Robert Ewan. University of Otago; Nueva Zelanda. National Museum of Natural History; Estados Unidos Fil: Reguero, Marcelo Alfredo. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Hocking, David P.. Monash University; Australia. Museums Victoria. Geosciences; Australia

The early Miocene of Patagonia (Argentina) provides one of the best-known records of odontocetes for an age interval with scarce fossils. Most of these taxa are historically old and briefly described, which has contributed, in part, to their controversial taxonomic position. The shark-toothed dolphin Phoberodon arctirostris was described almost 100 years ago and suggested as a member of Platanistoidea and Squalodontidae. However, it has not been analysed recently and has never been included in a phylogenetic analysis. Recent fieldwork in the early Miocene sediments in Patagonia yielded a new specimen referred to this species, allowing for its modern and detailed description and the first phylogenetic analyses. Analyses recovered P. arctirostris as a stem Odontoceti or an early-diverging platanistoid, more closely related to an unnamed Oligocene specimen from New Zealand and not in a clade with Squalodon calvertensis (i.e. Squalodontidae). The reconstructed body length of P. arctirostris indicates that it is one of the largest stem Odontoceti. Our results suggest that during the early Miocene of Patagonia, archaic odontocete forms (i.e. P. arctirostris) cohabited with archaic and more crownward platanistoids (i.e. Aondelphis talen and Notocetus vanbenedeni), helping to characterize the early Miocene cetacean communities of Patagonia. Fil: Viglino, Mariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Fordyce, Robert Ewan. University Of Otago; Canadá Fil: Cuitiño, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Fitzgerald, Erich M.G.. Museums Victoria; Australia

Two major marine transgressions covered part of Patagonia during the Miocene and both are recorded in the Peninsula Valdes region. The older (early Miocene) is represented by the volumetrically scarce outcrops of the Gaiman Formation, composed by shelf mudstones and fine sandstones. The late Miocene transgression is represented by the Puerto Madryn Formation, widely distributed in Peninsula Valdes and composed of mudstones, sandstones and shell beds, being the focus of this work. Sediments of this unit were deposited in inner shelf, nearshore, tidal channel and tidal flat environments. Fossil content is abundant and diverse, including palynomorphs, foraminifers, marine invertebrates (dominated by molluscs), cetaceans, pinnipeds, marine fishes and birds, as well as continental mammals, birds, and fishes. Isotopic and biostratigraphical data suggest a late Miocene age for the Puerto Madryn Formation, although some middle Miocene biostratigraphical indicators are present. Paleoenvironmental information suggests oceanic and continental temperatures warmer than present day, evidenced by the Caribbean molluscan association and the continental vertebrate and palinological associations, respectively. Instead, cetaceans, dinoflagellates, and some marine fishes, suggest colder oceanic temperatures. Precipitations were also higher than present, evidenced by the presence of freshwater mammals, birds, fishes, and plants. This work highlighted some gaps in the geological and paleontological knowledge including geochronology, stratigraphic control of paleontological studies and the knowledge of poorly known fossil groups, which should be the focus of future investigations.

We re-describe the holotype and referred specimen of Prosqualodon australis, from the early Miocene of Gaiman Formation (Chubut Province, Argentina), and analyse its phylogenetic position. Our study shows that this taxon is presently represented by an adult and a juvenile individuals and we provide the first diagnosis of the species based on the morphology of the anterior projection of the antorbital process along with plesiomorphic dental features (such as well-marked heterodont teeth, with posterior double rooted teeth in the maxilla, large, lateromedially compressed teeth with long crowns and denticulated enamel). The total body length of P. australis is estimated to be 2 m in the juvenile and 3 m in the adult specimen. We included for the first time this species in a phylogenetic analysis as an operational taxonomic unit itself, recovering P. australis as a stem-odontocete and Prosqualodon as a paraphyletic genus. Fil: Gaetán, Carlos Maximiliano. No especifica; Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Gaetano, Leandro Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentina

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a devastating autosomal recessive disorder due to mutations in TYMP, which cause loss of function of thymidine phosphorylase (TP), nucleoside accumulation in plasma and tissues and mitochondrial dysfunction. The clinical picture includes progressive gastrointestinal dysmotility, cachexia, ptosis and ophthalmoparesis, peripheral neuropathy and diffuse leukoencephalopathy, which usually lead to death in early adulthood. Therapeutic options are currently available in clinical practice (allogeneic hematopoietic stem cell transplantation and carrier erythrocyte entrapped TP therapy) and newer, promising therapies are expected in the near future. However, successful treatment is strictly related to early diagnosis. We report on an incomplete MNGIE phenotype in a young man harboring the novel heterozygote c.199 C>T (Q67X) mutation in exon 2, and the previously reported c.866 A>C (E289A) mutation in exon 7 in TYMP. The correct diagnosis was achieved many years after the onset of symptoms and unfortunately, the patient died soon after diagnosis because of multiorgan failure due to severe malnutrition and cachexia before any therapeutic option could be tried. To date, early diagnosis is essential to ensure that patients have the opportunity to be treated. MNGIE should be suspected in all patients who present with both gastrointestinal and nervous system involvement, even if the classical complete phenotype is lacking.

Recently, there has been a growing interest in the anatomy and optics of the visual system of cetaceans. However, much of the new information has been focused on odontocetes, and relatively little is known about the visual anatomy of baleen whales. The aim of this study was describe the eye anatomy of the southern right whale (Eubalaena australis). Eye samples were collected from 26 calves, four adults with known body length, as well as two specimens of unknown body length that had stranded near their nursery ground at Peninsula Valdes, Argentina, over 6 years. We provide anatomical descriptions of the eyeball and extraocular structures, as well as quantitative data in the form of eyeball, corneal, scleral, and lens measurements. To explore the sensitivity of the eye to light, the f-number was estimated in one specimen. We found that the eyes of the calves differed from those of the adults in having less periorbital fat surrounding the eyeball. We also observed variations in the abundance of periorbital fat among the adult specimens. The regression analysis revealed a correlation between body length and eyeball size. By contrast, the dimensions of the cornea were only weakly correlated with body length. The estimated f-number suggests that the optical sensitivity of the Eubalaena australis eye is relatively low. However, caution had to be taken in interpreting f-number as a proxy of eye sensitivity because it depends on the lens size, which can be affected by the fixation methods used. Anat Rec, 2012. © 2011 Wiley Periodicals, Inc.

Balaenidae (right and bowhead whales) are a key group in understanding baleen whale evolution, because they are the oldest surviving lineage of crown Mysticeti, with a fossil record that dates back ~20 million years. However, this record is mostly Pliocene and younger, with most of the Miocene history of the clade remaining practically unknown. The earliest recognized balaenid is the early Miocene Morenocetus parvus Cabrera, 1926 from Argentina. M. parvus was originally briefly described from two incomplete crania, a mandible and some cervical vertebrae collected from the lower Miocene Gaiman Formation of Patagonia. Since then it has not been revised, thus remaining a frequently cited yet enigmatic fossil cetacean with great potential for shedding light on the early history of crown Mysticeti. Here we provide a detailed morphological description of this taxon and revisit its phylogenetic position. The phylogenetic analysis recovered the middle Miocene Peripolocetus as the earliest diverging balaenid, and Morenocetus as the sister taxon of all other balaenids. The analysis of cranial and periotic morphology of Morenocetus suggest that some of the specialized morphological traits of modern balaenids were acquired by the early Miocene and have remained essentially unchanged up to the present. Throughout balaenid evolution, morphological changes in skull arching and ventral displacement of the orbits appear to be coupled and functionally linked to mitigating a reduction of the field of vision. The body length ofMorenocetus and other extinct balaenids was estimated and the evolution of body size in Balaenidae was reconstructed. Optimization of body length on our phylogeny of Balaenidae suggests that the primitive condition was a relatively small body length represented by Morenocetus, and that gigantism has been acquired independently at least twice (in Balaena mysticetus and Eubalaena spp.), with the earliest occurrence of this trait in the late Miocene-early Pliocene as represented by Eubalaena shinshuensis., Facultad de Ciencias Naturales y Museo

The nasal region of the skull has undergone dramatic changes during the course of cetacean evolution. In particular, mysticetes (baleen whales) conserve the nasal mammalian pattern associated with the secondary function of olfaction, and lack the sound-producing specializations present in odontocetes (toothed whales, dolphins and porpoises). To improve our understanding of the morphology of the nasal region of mysticetes, we investigate the nasal anatomy, osteology and myology of the southern right whale, Eubalaena australis, and make comparisons with other mysticetes. In E. australis external deflection surfaces around the blowholes appear to divert water off the head, and differ in appearance from those observed in balaenopterids, eschrichtiids and cetotherids. In E. australis the blowholes are placed above hypertrophied nasal soft tissues formed by fat and nasal muscles, a pattern also observed in balaenopterids (rorqual mysticetes) and a cetotherid (pygmy right whale, Caperea marginata). Blowhole movements are due to the action of five nasofacial muscles: dilator naris superficialis, dilator naris profundus, depressor alae nasi, constrictor naris, and retractor alae nasi. The dilator naris profundus found in E. australis has not been previously reported in balaenopterids. The other nasofacial muscles have a similar arrangement in balaenopterids, with minor differences. A novel structure, not reported previously in any mysticete, is the presence of a vascular tissue (rete mirabile) covering the lower nasal passage. This vascular tissue could play a role in warming inspired air, or may engorge to accommodate loss of respiratory space volume due to gas compression from increased pressure during diving. Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Fernandez, Marta Susana. Universidad Nacional de la Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Fordyce, Ewan. University Of Otago; Nueva Zelanda Fil: Reidenberg, Joy S.. Icahn School of Medicine at Mount Sinai; Estados Unidos

Los Balaenidae (Cetacea: Neoceti) son un grupo de misticetos caracterizados por presentar, en el cráneo y de la mandíbula, una serie de especializaciones vinculadas al sistema de alimentación por filtración, tales como un rostro muy arqueado y angosto, huesos rostrales sin interdigitación con los huesos occipitales, mandíbula con un proceso coronoides y angular reducido y barbas largas. El patrón corporal de los balénidos actuales, especialmente su anatomía esqueletaria, es muy conservador y sólo se reconocen cuatro especies distribuidas en dos géneros: Balaena (B. mysticetus) y Eubalaena (E. australis; E. glacialis; E. japonica). El registro fósil de los balénidos es temporalmente extenso (Mioceno temprano-actualidad) y, en algunos casos abundante (i.e. Plioceno, Pleistoceno,) pero está caracterizado por grandes discontinuidades estratigráficas y geográficas. En particular, el registro mioceno es extremadamente escaso y está restringido a la Patagonia argentina, con la presencia de Morenocetus parvus, el balénido más antiguo conocido (Mioceno temprano). Los registros de balénidos pliocenos y pleistocenos son, en cambio, abundantes aunque están restringidos al Hesmiferio Norte. Estos incluyen géneros extintos (Balaenella, Balaenula, Balaenotus) y otros con representantes actuales (Balaena y Eubalaena). Morenocetus parvus fue descripto y nominado por Cabrera (1926), en una monografía sobre cetáceos fósiles del Museo de La Plata, sobre la base de dos cráneos incompletos recuperados de la Formación Gaiman (Mioceno temprano, Chubut). Debido a que este taxón no fue re-estudiado luego de su descripción original, ha permanecido como una especie enigmática. Como resultado de trabajos paleontológicos en el sector de Península Valdés y alrededores, se han recuperado nuevos ejemplares de balénidos provenientes de la Formación Puerto Madryn (Mioceno tardío, Chubut). Estos ejemplares, junto con algunos restos aislados provenientes del Mioceno tardío de Entre Ríos (Formación Paraná) completan, en parte, los extensos hiatos del registro de balénidos Mioceno. La familia Balaenidae es un linaje clave en la evolución de los misticetos ya que, según algunos estudios filogenéticos, es el grupo más basal y más antiguo de misticetos actuales. Este supuesto está basado en la ocurrencia temprana de los balénidos en el registro estratigráfico, y en datos de divergencia antiguos estimados a partir de estudios moleculares. Uno de los puntos más controvertidos sobre las relaciones filogenéticas de los balénidos es la posición de su representante más antiguo, Morenocetus parvus. La importancia de este taxón, así como la de los otros registros miocenos recuperados en de la Formación Puerto Madryn y aún no descriptos, ameritan el estudio en profundidad de los balénidos miocenos de Patagonia. En este contexto, el objetivo general de esta tesis fue adquirir un mejor entendimiento de la historia evolutiva de los balénidos, mediante el análisis de los miembros más tempranos de este grupo. Para ello se aplicó un protocolo general de trabajo basado en la exploración de Eubalaena australis como modelo neontológico de los balénidos. La integración de la información osteológica y blanda obtenida permitió interpretar la anatomía de los taxones extintos, identificar los caracteres útiles para los análisis filogenéticos y la búsqueda de correlatos óseos para la reconstrucción de estructuras blandas en los fósiles. El estudio de individuos en distintos estadios madurativos de Eubalaena australis permitió identificar parámetros, independientes del tamaño y del cierre relativo de las suturas, que diferencian a los neonatos y crías de los adultos. Sobre la base de la información de los balénidos actuales, se procedió al estudio anatómico y posteriormente sistemático de los balénidos miocenos. Los resultados de los estudios sistemáticos indicaron que Morenocetus parvus es una entidad taxonómica válida y que está representado por dos ejemplares subadultos. Asimismo los 3 ejemplares de balénidos del Mioceno tardío de la Fm. Pto Madryn corresponden a un adulto, un subadulto y un juvenil de un mismo taxón que se propone como un nuevo género y especie (=Taxón A). La presencia en el ejemplar adulto del Taxón A de caracteres tales como, un proceso ascendente del maxilar aproximadamente triangular y corto ántero-posteriormente, una bulla timpánica de aspecto globoso sin una marcada compresión dorso-ventral, y superficie dorsal del periótico sin crestas ni surcos, se interpretan como rasgos paedomórficos. Por último, los balénidos de la Fm. Paraná (Mioceno tardío, Entre Ríos) están representados sólo por bullas timpánicas, las cuales no son asignables al Taxón A de la Fm. Puerto Madryn. La condición fragmentaria de los especímenes no permitió su identificación a niveles específicos ni genéricos, por lo cual se designaron como Balaenidae indet. Los análisis filogenéticos, de pesos implicados y pesos iguales, desarrollados en esta tesis dieron resultados consistentes entre sí, tanto en la topología general de los árboles como en las relaciones internas de los grandes clados. Los Balaenidae constituyen un grupo bien soportado y hermano del clado formado por los Balaenopteroidea y Cetotheriidae. Caperea marginata se recuperó, con buenos valores de soporte, profundamente anidado dentro de los Cetotéridos y constituye, de esta forma, el único representante actual de este clado. Los balénidos miocenos (Morenocetus y Taxón A) se recuperaron en un clado basal dentro de los Balaenidae; el soporte de este clado es adecuado y ninguno de los dos taxones fue hallado como inestables. Balaenella y Balaenula se posicionaron como sucesivos taxones hermanos de los balénidos modernos (Balaena y Eubalaena). Las relaciones dentro de los clados modernos (Balaena y Eubalaena) no lograron resolverse. La calibración estratigráfica del cladograma mostró un extenso linaje fantasma entre los balénidos miocenos y los balénidos más derivados (Balaenella, Balaenula, Balaena y Eubalaena). La extensión de este linaje fantasma (~15 Ma) abarca desde el Mioceno temprano-tardío (Burdigaliense) hasta el Plioceno temprano (Zancliense). A esto se suma un extenso hiato temporal en el registro fósil de los balénidos que abarca más de la mitad de la historia evolutiva del grupo. El hallazgo del Taxón A del Mioceno tardío de la Fm. Puerto Madryn interrumpe el hiato temporal entre Morenocetus y los balénidos más derivados, pero no acorta el linaje fantasma previamente mencionado. Los aspectos paleobiológicos de los balénidos miocenos indagados en esta tesis comprendieron los siguientes tópicos: la evolución de la longitud corporal y su relación con la tendencia al gigantismo, la reconstrucción de la morfología de la región nasal y su vinculación con el buceo y la exploración de correlatos óseos vinculados con los órganos de los sentidos (ojo y oído). En relación con el primero de estos tópicos, las estimaciones efectuadas del largo corporal, y su mapeo sobre el árbol filogenético, sugieren que la condición primitiva para los misticetos es un largo corporal pequeño (, Facultad de Ciencias Naturales y Museo

The origins and evolutionary relationships of the pygmy right whale (Caperea marginata),the only living member of the Neobalaeninae, have been the subject of a long-standing debate. This phylogenetic uncertainty is compounded by a limited neobalaenine fossil record. Here, we report a Late Miocene mysticete mandible from Patagonia, Argentina and provisionally refer it to Neobalaeninae, gen. et sp. indet. The new material represents only the third report of a fossil neobalaenine, and the first fossil occurrence of this lineage in the southwestern Atlantic. It is also the oldest specimen so far reported, thus corroborating the idea of an early divergence time for neobalaenines. Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Dozo, Maria Teresa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina Fil: Marx, Felix G.. University Of Otago; Nueva Zelanda. National Museum of Nature and Science; Japón Fil: Fordyce, R. Ewan. University Of Otago; Nueva Zelanda

El registro fósil de los basilosáuridos está bien documentado durante el Bartoniano—Priaboniano en varias localidades del mundo, lo cual indica que este grupo estaba ampliamente distribuido durante el Eoceno medio tardío. En el Hemisferio Norte, el registro fósil de este grupo es abundante, a diferencia de lo que ocurre en el Hemisferio Sur donde es escaso y, en algunos casos (i.e., Antártida), dudoso. La presencia de basilosáuridos en Antártida es incierta ya que la mayoría de los registros están basados en materiales fragmentarios, lo cual imposibilita su asignación a algún grupo de arqueocetos. En la presente contribución se describen restos de basilosáuridos correspondientes a mandíbulas, dientes aislados y un hueso pélvico, recuperados de la Formación La Meseta (TELM 4 Lutetiano—Bartoniano; TELM 7 Priaboniano), Isla Marambio (Seymour), (Cuenca James Ross, Península Antártica). Este hallazgo confirma la presencia de Basilosauridae en la Antártida, contribuyendo al conocimiento de la distribución paleobiogeográfica de este grupo durante el Eoceno medio—tardío. Finalmente, uno de estos registros se encuentra entre los basilosáuridos más antiguos conocidos, indicando un rápida radiación y dispersión de este grupo al menos desde el Eoceno medio temprano. Basal fully aquatic whales, the basilosaurids are worldwide known from Bartonian—Priabonian localities, indicating that this group was widely distributed during the late middle Eocene. In the Northern Hemisphere, fossils of basilosaurids are abundant, while records in the Southern Hemisphere are scarce and, in some cases (i.e., Antarctica), doubtful. The presence of basilosaurids in Antarctica was, until now, uncertain because most of the records are based on fragmentary materials that preclude an accurate assignment to known archaeocete taxa. Here we report the findings of mandibles, teeth, and innominate bone remains of basilosaurids recovered from the La Meseta Formation (TELM 4 Lutetian—Bartonian and; TELM 7 Priabonian), in Marambio (Seymour) Island (James Ross Basin, Antarctic Peninsula). These findings confirm the presence of Basilosauridae in the marine realm of Antarctica, increasing our knowledge of the paleobiogeographic distribution of basilosaurids during the middle—late Eocene. In addition, one of these records is among the oldest occurrences of basilosaurids worldwide, indicating a rapid radiation and dispersal of this group since at least the early middle Eocene. Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; Argentina Fil: Fernández, Marta Susana. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Reguero, Marcelo Alfredo. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Marenssi, Sergio Alfredo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Santillana, Sergio N.. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; Argentina Fil: Mörs, Thomas. Swedish Museum of Natural History; Suecia

The origin of the pygmy right whale (Caperea marginata) has long been one of the most vexing conundrums of marine mammal evolution. The extremely disparate skeletal structure ofCapereaand a patchy fossil record have left morphology and molecules at odds: whereas most morphological analyses allyCapereawith right whales (Balaenidae), most molecular studies instead suggest a close relationship with rorquals (Balaenopteridae) and grey whales (Eschrichtiidae). The morphological evidence supporting aCaperea-balaenid clade consists of several shared features of the skull and mandible, as traditionally observed in adult individuals. Here, we show that at least two of these features, the ascending process of the maxilla and the coronoid process, arise from substantially different precursors early during ontogeny and therefore likely do not represent genuine synapomorphies. Both of these juvenile morphologies have adult counterparts in the fossil record, thus indicating that the ontogenetic variation in the living species may be a genuine reflection of differing ancestral states. This new evidence contradicts previous morphological hypotheses on the origins ofCapereaand may help to reconcile morphological and molecular evidence. Fil: Marx, Felix. University Of Otago. Department of Geology; Nueva Zelandia; Fil: Buono, Mónica Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagonico; Argentina Fil: Fordyce, R. Ewan. University Of Otago. Department of Geology; Nueva Zelandia; Fil: Boessenecker, Robert W.. University Of Otago. Department of Geology; Nueva Zelandia