Anatomía craneana y posición filogenética de un nuevo cachalote enano (Odontoceti: Kogiidae) del mioceno tardío de la formación Pisco, Arequipa, Perú

Los cachalotes enanos de la familia Kogiidae son un grupo muy poco conocido de mamíferos marinos. El ejemplar MUSM 973 es un nuevo taxón de kógido proveniente del Mioceno tardío de la Formación Pisco, Montemar, Arequipa. Este animal es reconocido como Kogiidae debido a poseer una cuenca supracraneal reducida, ausencia del contacto entre escamoso y lacrimojugal, y la presencia de una cresta sagital. Se realizaron dos análisis filogenéticos principales a fin de contrastar las afinidades filogenéticas de este animal, junto a otros taxones fósiles de physeteroideos. Los resultados del análisis filogenético indican que MUSM 973 se encuentra cercanamente relacionado con Scaphokogia cochlearis, diferenciándose de éste por poseer un rostro más corto, mayor desarrollo de las crestas maxilares, un pterigoides mucho más prominente y el rostro ligeramente afinado anteriormente. La inclusión de MUSM 973 junto a Scaphokogia permite replantear el clado Scaphokogiinae como el grupo de kógidos que incluyen a animales con rostro mediano a largo, canal mesorostral muy desarrollado y cresta sagital desviada hacia el lado izquierdo del cráneo. El desarrollo hipertrofiado del canal mesorostral sugiere que dicha estructura pudo usarse a manera de sensor béntico, evidenciado también en la proyección ventral del rostro. Esta presumible adaptación, junto al desarrollo notorio del órgano espermaceti, pueden haber creado un nuevo nicho ecológico en el cual estos cachalotes prosperaron, antes de la llegada de los delfines. Finalmente, la inclusión de este nuevo taxón junto a Koristocetus pescei, Acrophyseter deinodon y Scaphokogia cochlearis demuestra que la diversificación del grupo fue mucho mayor a lo reportado para el Mioceno tardío. Además, se evidencia que las condiciones existentes en el antiguo mar peruano debieron ser excepcionalmente ricas para poder mantener a esta gran diversidad de animales.Tesi

La hiperdiversificación de Physeteroidea (Cetacea: Mammalia) del Mioceno tardío en el Pacifico Sur, nuevos fósiles del área de Sacaco, Arequipa, Perú

Sperm whales (Physeteroidea) are a group of cetaceans with a restricted modern ecology. The three extant species are a remnant of a group that reached its diversity peak during the Miocene, including five already-described species from the Pisco Formation, Ica-Arequipa, Peru. We report two isolated teeth from the upper Miocene localities of Sacaco and Sud-Sacaco, which correspond with the typical morphology of Physeteridae. This morphology is similar to the one present in northern hemisphere taxa as Orycterocetus or Aulophyseter. Because of this the remains could be related to physeterids with piscivorous habits, so there would not be a niche overlap with other coeval sperm whales. This new registry expands the fossil cetacean community of Sacaco, which was favored by the great diversity of shallow environments that dominated the Peruvian coast until the final establishment of the Humboldt System.Los cachalotes (Physeteroidea) son un grupo de cetáceos con una ecología restringida en la actualidad. Las tres especies actuales son el remanente de un grupo que alcanzó su máxima diversificacion durante el Mioceno, incluyendo cinco especies simpátricas descritas en la Formación Pisco, Ica-Arequipa, Perú. Entre estas se incluyen formas piscívoras, bénticas, así como carnívoros de tamaño medio e hipercarnívoros. Se reportan dos dientes aislados provenientes del Mioceno superior de las localidades de Sacaco y Sacaco sur, que corresponden con la morfología típica de Physeteridae. Esta morfología dentaria es similar a la de taxones presentes en el hemisferio norte como Orycterocetus o Aulophyseter del Mioceno medio. Debido a esto se presume que los restos corresponderían a physetéridos con hábitos piscívoros, que quizás poseyeron un desarrollo incipiente de la capacidad de succión. La presencia de este linaje indicaría que a fines del Mioceno los parientes de los modernos Physeter y Kogia compartieron el mar peruano con formas extintas, sin solapamiento de nichos debido a la morfología altamente derivada de cada grupo. Este nuevo registro expande la comunidad de cetáceos fósiles de Sacaco, que se vio favorecida por la gran diversidad de ambientes poco profundos que dominaron el litoral peruano hasta el establecimiento final del Sistema Humboldt

A historical vertebrate collection from the Middle Miocene of the Peruvian Amazon

The Miocene aquatic and terrestrial fossil record from western Amazonia constitute a clear evidence of the palaeoenvironmental diversity that prevailed in the area, prior to the establishment of the Amazon River drainage. During the Miocene, the region was characterized by a freshwater megawetland basin, influenced by episodic shallow-marine incursions. A fossil vertebrate collection from the middle Miocene strata of the Pebas Formation is here studied and described. This historical collection was recovered in 1912 along the banks of the Itaya River (Iquitos, Peru), during a scientific expedition led by two scientists of the University of Zurich, Hans Bluntschli and Bernhard Peyer. Our findings include a total of 34 taxa, including stingrays, bony fishes, turtles, snakes, crocodylians, and lizards. Fishes are the most abundant group in the assemblage (~ 23 taxa), including the first fossil record of the freshwater serrasalmids Serrasalmus, and Mylossoma, and the hemiodontid Hemiodus for the Pebas system, with the latter representing the first fossil be discovered for the entire Hemiodontidae. The presence of a representative of Colubroidea in the middle Miocene of Iquitos supports the hypothesis of arrival and dispersal of these snakes into South America earlier than previously expected. This fossil assemblage sheds light on the palaeoenvironments, and the geographical/temporal range of several aquatic/terrestrial lineages inhabiting the Amazonian region

Aquatic mammal fossils in Latin America – a review of records, advances and challenges in research in the last 30 years

Records of aquatic mammal fossils (e.g. cetaceans, pinnipeds, sirenians, mustelids, and desmostylians) from Latin America (Mexico to Tierra del Fuego, including Antartica) span since the mid-1800s. Aquatic mammal fossils received little attention from the scientific community, with most of the first studies conducted by Northern Hemisphere researchers. Over the last 30 years, paleontological research in Latin America has increased considerably, with descriptions of several new species and revisions of published original records. The Latin American fossil record of marine mammals spans from the Eocene to the Pleistocene, with formations and specimens of global significance. All three main groups of cetaceans are represented in the continent (Archaeoceti, Mysticeti, and Odontoceti). Pinnipedia are represented by the families Otariidae and Phocidae, with records starting in the Middle Miocene. Both living families of Sirenia (Trichechidae and Dugongidae) are recorded. While less common, but still relevant, records of desmostylians and mustelids are known from Oligocene and Miocene deposits. This review provides a summary of the aquatic mammals known to date, with a special focus on the advances and developments of the last 30 years, since Cozzuol’s (1996) review of the South American fossil record. An up-to-date complete list of species based on the literature and unpublished data is also provided. The study also provides future directions for paleontological research in Latin America, and discusses the challenges and opportunities in the field, including the emergence of a strong new generation of Latin American researchers, many of whom are women. Keywords: Cetacea, Pinnipedia, Sirenia, Southern Hemispher

A new physeteroid from the late Miocene of Peru expands the diversity of extinct dwarf and pygmy sperm whales (Cetacea: Odontoceti: Kogiidae)

Nowadays, the odontocete family Kogiidae is monotypic and only includes two species of diminutive relatives of the great sperm whale Physeter Linnaeus, 1758. Conversely, a growing body of extinct species indicates that kogiids were diverse and disparate during the late Neogene. The fossil record of Kogiidae is, to date, represented by several cranial specimens from Mio-Pliocene localities of the Northern Hemisphere, with the significant Southern Hemisphere exception of the Pisco Formation of Peru, from which two genera were known so far, including Scaphokogia Muizon, 1988, a highly idiosyncratic form characterised by a distinctly spoon-shaped dorsal surface of the neurocranium and a downturned semicylindrical rostrum, which is even placed in its own subfamily Scaphokogiinae. Here, we report on two skulls of Kogiidae from the Messinian (upper Miocene) portion of the Pisco Formation exposed in the East Pisco Basin. These two skulls are referred to the new taxon Platyscaphokogia landinii n. gen., n. sp., which our phylogenetic analysis recovers as sister group of Scaphokogia, within the subfamily Scaphokogiinae. Although Platyscaphokogia n. gen. shares with Scaphokogia a remarkably spoon-like dorsal aspect of the neurocranium, it retains a non-pachyostotic, dorsoventrally thin rostrum that distinctly points anteriorly; as such, Platyscaphokogia n. gen. might be regarded as testifying an early stage in the evolution of the scaphokogiine cranial anatomy. Morphofunctional and palaeoecological considerations allow for hypothesising that Platyscaphokogia n. gen. was a raptorial physeteroid that foraged along the water column in relatively open-sea palaeoenvironments. In conclusion, our finds expand the palaeodiversity of Kogiidae, as well as our knowledge on the late Miocene sperm whales of the southeastern Pacific, and further suggest that the fossil content of the East Pisco Basin is crucial for reconstructing the Neogene evolutionary history of physeteroids. La famille d’odontocètes Kogiidae est de nos jours monotypique et ne comprend que deux espèces, parents de petite taille du grand cachalot Physeter Linnaeus, 1758. Inversement, un nombre croissant d’espèces éteintes décrites indique que les kogiidés montraient une diversité et une disparité élevées pendant le Néogène tardif. Le registre fossile des Kogiidae est à ce jour représenté par plusieurs spécimens crâniens de localités mio-pliocènes de l’hémisphère nord, à l’exception australe de la Formation Pisco, au Pérou, de laquelle deux genres étaient connus à ce jour, incluant Scaphokogia Muizon, 1988, une forme hautement idiosyncratique caractérisée par une surface dorsale du neurocrâne distinctement en forme de cuillère et un rostre en semi-cylindre renversé, qui est placé dans sa propre sous-famille Scaphokogiinae. Nous rapportons ici deux crânes de Kogiidae de la portion messinienne (Miocène supérieur) de la Formation Pisco exposée dans la partie orientale du Bassin Pisco. Ces deux crânes sont référés au nouveau taxon Platyscaphokogia landinii n. gen., n. sp., que notre analyse phylogénétique place comme groupe-frère de Scaphokogia au sein de la sous-famille Scaphokogiinae. Bien que Platyscaphokogia n. gen. partage avec Scaphokogia un aspect dorsal du neurocrâne remarquablement en forme de cuillère, ce nouveau genre conserve un rostre non-pachyostotique, dorso-ventralement aplati, et pointu; Platyscaphokogia n. gen. pourrait donc être considéré comme témoignant d’un stade précoce de l’évolution de l’anatomie crânienne des scaphokogiinés. Des considérations morphofonctionnelles et paléoécologiques permettent de supposer que Platyscaphokogia n. gen. était un physétéroïdé raptorial qui se nourrissait dans la colonne d’eau, dans des paléoenvironnements relativement ouverts. En conclusion, nos découvertes augmentent la paléodiversité des Kogiidae, ainsi que nos connaissances sur les cachalots du Miocène tardif du Pacifique sud-est, et suggèrent en outre que les fossiles de la partie orientale du Bassin Pisco sont cruciaux pour la reconstruction de l’histoire évolutive des physétéroïdés du Néogène

Bridging two oceans: small toothed cetaceans (Odontoceti) from the Late Miocene Chagres Formation, eastern Caribbean (Colon, Panama)

Fossil cetaceans are often found in Miocene marine outcrops across the globe. However, because this record is not homogeneous, the dissimilar increase in occurrences, along with the sampling bias has created regions with extensive records and others with great scarcity. Among these, the Caribbean has remained enigmatic due to the lack of well-preserved cetacean fossils. Here, we report new Caribbean fossil cetaceans from the Upper Miocene Chagres Formation exposed along Piña beach, Eastern Panama, including a scaphokogiine kogiid, an Acrophyseter-like physeteroid and the phocoenid Piscolithax. Along with previous records of the iniid Isthminia panamensis and the kogiine Nanokogia isthmia, the Chagres cetacean fauna shows some similarities with other Late Miocene cetacean communities such as the Californias in the North Pacific, although their closest affinities lie with the eastern South Pacific Pisco Formation, Peru. Such findings indicate that though deep and intermediate Caribbean-Pacific water interchange was reduced by the Middle Miocene due to the shallowing of the Central American Seaway, shallow waters marine connection that persisted until the Pliocene might have facilitated the dispersal of coastal species across both sides of the Isthmus

Scaphokogia totajpe, sp. nov., a new bulky-faced pygmy sperm whale (Kogiidae) from the late Miocene of Peru

The modern pygmy and dwarf sperm whales (Physeteroidea, Kogiidae) are remnants of a highly diverse group, which flourished in the Miocene oceans. Unlike their modern suction-feeding, deep-diving relatives, the past diversity of this family includes animals with disparate ecological habits. Here, we describe Scaphokogia totajpe, sp. nov., a new species of kogiid based on a well-preserved skull from the upper Miocene strata of the Pisco Formation, Peru. A phylogenetic analysis places S. totajpe as sister taxon of S. cochlearis and divides Kogiidae into two clades: the first including both species of Scaphokogia and the second including Kogia, Koristocetus, Praekogia, and Nanokogia. Similar to S. cochlearis, S. totajpe has a tubular rostrum with a hypertrophied mesorostral canal, a large supracranial basin, and a leftward deviated facial sagittal crest, but it differs by possessing a proportionately shorter rostrum, a reduced projection of the lacrimojugal between the frontal and the maxilla, and a flat occipital shield. The cranial morphology of Scaphokogia indicates that the extent of the nasal complex was greater than in modern kogiids. Furthermore, the overall rostrum shape and the reconstructed muscle insertion sites indicate that Scaphokogia retained some plesiomorphic features related to a more generalist ecology. Inclusion of S. totajpe into the context of the Pisco Formation indicates that during the late Miocene, the Peruvian coastal system was a hot spot for the diversification of physeteroids, with at least four species coexisting. Finally, Scaphokogia totajpe highlights a late Miocene diversity peak for sperm whales in the global oceans, before the Pliocene odontocete turnover

A new record of a giant neoepiblemid rodent from Peruvian Amazonia and an overview of lower tooth dental homologies among chinchilloids

International audienceWe report here a new record of the giant caviomorph Phoberomys corresponding to a fragmentary mandible from the Monte Salvado area, Peruvian Amazonia (Madre de Dios Department). We describe this specimen and compare it with the material previously attributed to Phoberomys. The mandibular fragment is referred to as Phoberomys sp. Found as float on a bank of the Río Las Piedras, it has been hypothetically assigned a late Miocene age, due to the local/regional stratigraphic and lithologic context. This specimen constitutes the second record of Phoberomys in Peru. For the first time, the pattern of p4s and lower molars in Phoberomys was analyzed and compared to a large taxonomic sample (in-cluding Paleogene-Recent chinchilloids and other caviomorphs) in order to progress the understanding of the homology of dental structures in this genus. For p4s and lower molars, the position of the protoconid in Phoberomys and other chinchilloids (Drytomomys sp., Potamarchus, Eumegamys, Gyriabrus, Isostylomys, and Tetrastylus) is ambiguous, and as a result we propose two alternative homology hypotheses for these taxa: protoconid within the first and second laminae or within the third lamina on juvenile specimens. The knowledge of a comprehensive ontogenetic sequence in extinct and extant chinchilloids, associated with more complete palaeontological records, would likely allow for a clarification of these homology ambiguities

A stem delphinidan from the Caribbean region of Venezuela

The dense Miocene record of cetaceans is known from localities along the coasts of all continents, mostly in the northern Atlantic or the eastern Pacific regions, but Antarctica. Fossils from the Caribbean region are few and include of a couple of findings from Panama and Venezuela. Here, we report a partly complete skull from the Caujarao Formation (middle Miocene), Falcon State, Caribbean region of Venezuela. Our phylogenetic analyses indicate that the Caujarao specimen is a ‘stem delphinidan’, a group that includes several taxa of early diverging odontocetes whose phylogenetic affinities remain a matter of debate. The fossil record has shown that this group of stem delphinidans was taxonomically diverse, but displayed a somewhat homogeneous cranial patterning, with most of the variations being found within the mandible or tympanoperiotic characters. As other stem delphinidans the Caujarao odontocete displays an enlarged temporal fossa and a fairly symmetrical cranium. Because the skull is missing several key diagnostic characters due to the preservation state of the specimen, a more precise taxonomic identification is not possible. Despite this, the finding of this specimen highlights the importance of the fossil record from the Neogene of Venezuela, and the importance of the area to understand cetacean evolution in the proto-Caribbean

Miocene Freshwater Dolphins from La Venta, Huila, Colombia Suggest Independent Invasions of Riverine Environments in Tropical South America

The two extant genera of strictly freshwater dolphins Inia and Platanista are the result of convergent evolution to freshwater environments with reduced visibility. Characterized by their long snout and small melon, these extant taxa are clustered into two clades, Iniidae in South America and Platanistidae in Southern Asia. Their evolutionary history leading to freshwater environments remains mostly unknown, because many of their related fossil species have been found in marine environments. Here, we report riverine dolphin remains (two rostral fragments and a periotic) from two stratigraphic levels of the late middle Miocene (ca. 12.5 Ma) from La Venta, Colombia. The periotic has a reduced cochlear aqueduct mediodorsally oriented, the anterior process is relatively thin, and the dorsal opening of the facial canal is located lateral to the spiral cribriform tract. The rostral fragments are dorsoventrally flattened; the mandible features two longitudinal ventral grooves, and the premaxilla-maxilla suture of the rostrum is located in a deep lateral groove. These characteristics indicate that the specimens belong to Platanistidae, the lineage of the Ganges river dolphin Platanista. Platanistids had also been recorded on coeval strata from the Fitzcarrald arch, Peru. The occurrence of middle Miocene platanistids in both the La Venta and Fiztcarrald localities suggests that members of this lineage moved into freshwater environments in South America earlier than the ancestors of the modern Amazon river dolphin Inia. The subsequent collapse of the Pebas ecosystem could have played a role in the extinction of non-marine Platanistoidea in South America