A 60-million-year Cenozoic history of western Amazonian ecosystems in Contamana, eastern Peru

Weprovide a synopsis of ~60million years of life history in Neotropical lowlands, based on a comprehensive survey of the Cenozoic deposits along the Quebrada Cachiyacu near Contamana in PeruvianAmazonia. The 34 fossilbearing localities identified have yielded a diversity of fossil remains, including vertebrates,mollusks, arthropods, plant fossils, and microorganisms, ranging from the early Paleocene to the lateMiocene–?Pliocene (N20 successive levels). This Cenozoic series includes the base of the Huchpayacu Formation (Fm.; early Paleocene; lacustrine/ fluvial environments; charophyte-dominated assemblage), the Pozo Fm. (middle + ?late Eocene; marine then freshwater environments; most diversified biomes), and complete sections for the Chambira Fm. (late Oligocene–late early Miocene; freshwater environments; vertebrate-dominated faunas), the Pebas Fm. (late early to early late Miocene; freshwater environments with an increasing marine influence; excellent fossil record), and Ipururo Fm. (late Miocene–?Pliocene; fully fluvial environments; virtually no fossils preserved). At least 485 fossil species are recognized in the Contamana area (~250 ‘plants’, ~212 animals, and 23 foraminifera). Based on taxonomic lists from each stratigraphic interval, high-level taxonomic diversity remained fairly constant throughout themiddle Eocene–Miocene interval (8-12 classes), ordinal diversity fluctuated to a greater degree, and family/species diversity generally declined, with a drastic drop in the early Miocene. The Paleocene–?Pliocene fossil assemblages from Contamana attest at least to four biogeographic histories inherited from (i) Mesozoic Gondwanan times, (ii) the Panamerican realm prior to (iii) the time of South America’s Cenozoic “splendid isolation”, and (iv) Neotropical ecosystems in the Americas. No direct evidence of any North American terrestrial immigrant has yet been recognized in the Miocene record at Contamana.Facultad de Ciencias Naturales y Muse

Fósiles de Dugongidae (Mammalia, Sirenia) de la formación Parana (Mioceno tardío) de la provincia de Entre Ríos, Argentina

Los sirenios fósiles son bien conocidos en la región del Atlántico occidental y el Caribe (WAC). Los registros neógenos de la costa atlántica de América del Sur, aunque escasos, parecen reflejar una composición taxonómica similar a la de sus contemporáneos del norte. Los sirenios fósiles de Argentina son conocidos desde el Mioceno tardío en las formaciones Paraná e Ituzaingó en la provincia de Entre Ríos. Un tercer molar superior depositado en el Museo de Paleontología de la Universidad Nacional de Córdoba (CORD-PZ 4301), de la Formación Paraná, fue descrito y asignado originalmente al dugongo del género Metaxytherium Christol. En trabajos posteriores se sugirió que podría pertenecer al dugongo del género Dioplotherium Cope, una designación que se confirma tras el examen del material. Además, se describen nuevos restos de sirenios de la Formación Paraná, correspondientes a dos maxilares superiores incompletos con dientes, pertenecientes a un mismo individuo, depositados en el Museo de Ciencias Naturales de Paraná (MASP 373). Este espécimen muestra similitudes con especies de Metaxytherium del norte del WAC. Los sirenios de la Formación Paraná representan los registros más australes de estos dos géneros y la aparición geológicamente más joven de dugongos en el sur del WAC. Dioplotherium y Metaxytherium también se encuentran en el Mioceno temprano del norte de Brasil. La presencia de estos taxones hasta latitudes tan australes como Entre Ríos sugiere dos posibles rutas de dispersión: (1) a través de una conexión marginal entre un brazo sur del Mar de la Amazonía y el “Mar Paranense”; (2) a lo largo de la costa brasileña. Por último, la aparición de dugongos, que se alimentan principalmente de pastos marinos, indica que estas angiospermas marinas estuvieron presentes en la región.Fossil sirenians are well known from the Western Atlantic and Caribbean (WAC) region. Neogene records from the Atlantic coast of South America, although scarce, seem to reflect a similar taxonomic composition to its northern contemporaries. Fossil sirenians from Argentina are known from the late Miocene Paraná and Ituzaingó formations in Entre Ríos Province. An upper third molar housed in the Museo de Paleontología de la Universidad Nacional de Córdoba (CORD-PZ 4301), from the Paraná Formation, was originally described and assigned to the dugongid genus Metaxytherium Christol. Subsequent workers suggested it could instead belong to the dugongid genus Dioplotherium Cope, a designation that we confirm upon examination of the material. Additionally, we describe new sirenian remains from the Paraná Formation, consisting of two incomplete maxillae with teeth, belonging to one individual, deposited at the Museo de Ciencias Naturales de Paraná (MASP 373). This specimen shows similarities with species of Metaxytherium from the northern WAC. The Paraná Formation sirenians represent the southernmost occurrences of these two genera, and the geologically youngest occurrence of dugongids in the southern WAC. Dioplotherium and Metaxytherium also occur in the early Miocene of northern Brazil. The presence of these taxa as far south as Entre Ríos latitude suggests two possible dispersal routes: (1) across a marginal connection between a southern arm of the Amazonian Sea and the Paranense Sea; (2) along the Brazilian coast. Lastly, the occurrence of dugongids, which feed mainly on seagrasses, indicates that these marine angiosperms were present in the region as well.Fil: Vélez Juarbe, Jorge. Howard University; Estados UnidosFil: Noriega, Jorge Ignacio. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; ArgentinaFil: Ferrero, Brenda Soledad. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentin

3D models related to the publication: Early Oligocene chinchilloid caviomorphs from Puerto Rico and the initial rodent colonization of the West Indies: 3D models of Oligocene Puerto Rican chinchilloids

International audienceThis contribution contains the 3D models of the fossil teeth of two chinchilloid caviomorph rodents (Borikenomys praecursor and Chinchilloidea gen. et sp. indet.) discovered from lower Oligocene deposits of Puerto Rico, San Sebastian Formation (locality LACM Loc. 8060). These fossils were described and figured in the following publication: Marivaux et al. (2020), Early Oligocene chinchilloid caviomorphs from Puerto Rico and the initial rodent colonization of the West Indies. Proceedings of the Royal Society B. http://dx.doi.org/10.1098/rspb.2019.280

3D models related to the publication: An unpredicted ancient colonization of the West Indies by North American rodents: dental evidence of a geomorph from the early Oligocene of Puerto Rico

International audienceThis contribution provides the raw files for the µCT-scan data and renderings of the three-dimensional digital models of two fossil teeth of a geomyin geomorph rodent (Caribeomys merzeraudi), discovered from lower Oligocene deposits of Puerto Rico, San Sebastian Formation (locality LACM Loc. 8060). These fossils were described, figured and discussed in the following publication: Marivaux et al. (2021), An unpredicted ancient colonization of the West Indies by North American rodents: dental evidence of a geomorph from the early Oligocene of Puerto Rico. Papers in Palaeontology. https://doi.org/10.1002/spp2.138

Fossil Sirenia of the West Atlantic and Caribbean region. Ix. <i>Metaxytherium albifontanum</i>, sp. nov.

<div><p>ABSTRACT</p><p>We describe a new species of the halitheriine dugongid genus <i>Metaxytherium</i> from the late Oligocene of Florida and South Carolina. The new species is represented by cranial and postcranial material, including parts of the axial and appendicular skeleton. <i>Metaxytherium albifontanum</i>, sp. nov., differs from other species of <i>Metaxytherium</i> by the following unique combination of plesiomorphic and derived characters: posterior end of nasal process of premaxilla broad and flat relative to what is observed in most other members of the genus (somewhat resembling <i>M. subapenninum</i>); ventral extremity of jugal under posterior edge of orbit (character 85[1]) (shared with <i>M. krahuletzi</i>); exoccipitals separated in dorsal midline (character 66[1]) (shared with all other species in the genus, except some <i>M. krahuletzi</i>); and innominate with acetabulum (nearly lost or lost in <i>M. crataegense</i>, <i>M. floridanum</i>, <i>M. serresii</i>). This new species was sympatric with two dugongines, <i>Crenatosiren olseni</i> and <i>Dioplotherium manigaulti</i>. The small tusks and cranial morphology of <i>M. albifontanum</i>, sp. nov., indicate that it was likely a consumer of small seagrasses. Our phylogenetic analysis is consistent with previous ones in placing Hydrodamalinae within a paraphyletic <i>Metaxytherium</i> spp. and placing the <i>Metaxytherium</i> spp. + Hydrodamalinae clade as the sister group to Dugonginae. <i>Metaxytherium albifontanum</i>, sp. nov., is the oldest known member of its genus; this might indicate that the group originated in the West Atlantic and Caribbean region and later dispersed to the Old World Tethys region.</p> <p>SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at <a href="http://www.tandfonline.com/UJVP" target="_blank">www.tandfonline.com/UJVP</a>.</p> </div

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

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

Nasal compartmentalization in Kogiidae (Cetacea, Physeteroidea): Insights from a new late Miocene dwarf sperm whale from the Pisco Formation

Facial compartmentalization in the skull of extant pygmy whales (Kogiidae) is a unique feature among cetaceans that allows for the housing of a wide array of organs responsible for echolocation. Recent fossil findings indicate a remarkable disparity of the facial bone organization in Miocene kogiids, but the significance of such a rearrangement for the evolution of the clade has been barely explored. Here we describe Kogia danomurai sp. nov., a late Miocene (c. 5.8 Ma) taxon from the Pisco Formation (Peru), based on a partially preserved skull with a new facial bone pattern. Phylogenetic analysis recovers K. danomurai as the most basal representative of the extant genus Kogia, displaying a combination of derived (incipiently developed and excavated sagittal facial crest) and plesiomorphic features (high position of the temporal fossa, and antorbital notch not transformed into a narrow slit). Furthermore, when compared with the extant Kogia, the facial patterning found in K. danomurai indicates differential development among the facial organs, implying different capabilities of sound production relative to extant Kogia spp. Different facial bone patterns are particularly notable within the multi‐species kogiid assemblage of the Pisco Formation, which suggests causal connections between different patterns and feeding ecologies (e.g. nekton piscivory and benthic foraging). At c. 5.8 Ma, K. danomurai was part of a cetacean community composed of clades typical of the late Miocene, and of other early representatives of extant taxa, a mixture probably representing an initial shift of the coastal faunas toward the ecosystem dynamics of the present‐day south‐eastern Pacific

Isthminia panamensis, a new fossil inioid (Mammalia, Cetacea) from the Chagres Formation of Panama and the evolution of ‘river dolphins’ in the Americas

In contrast to dominant mode of ecological transition in the evolution of marine mammals, different lineages of toothed whales (Odontoceti) have repeatedly invaded freshwater ecosystems during the Cenozoic era. The so-called ‘river dolphins’ are now recognized as independent lineages that converged on similar morphological specializations (e.g., longirostry). In South America, the two endemic ‘river dolphin’ lineages form a clade (Inioidea), with closely related fossil inioids from marine rock units in the South Pacific and North Atlantic oceans. Here we describe a new genus and species of fossil inioid, Isthminia panamensis, gen. et sp. nov. from the late Miocene of Panama. The type and only known specimen consists of a partial skull, mandibles, isolated teeth, a right scapula, and carpal elements recovered from the Piña Facies of the Chagres Formation, along the Caribbean coast of Panama. Sedimentological and associated fauna from the Piña Facies point to fully marine conditions with high planktonic productivity about 6.1–5.8 million years ago (Messinian), pre-dating the final closure of the Isthmus of Panama. Along with ecomorphological data, we propose that Isthminia was primarily a marine inhabitant, similar to modern oceanic delphinoids. Phylogenetic analysis of fossil and living inioids, including new codings for Ischyrorhynchus, an enigmatic taxon from the late Miocene of Argentina, places Isthminia as the sister taxon to Inia, in a broader clade that includes Ischyrorhynchus and Meherrinia, a North American fossil inioid. This phylogenetic hypothesis complicates the possible scenarios for the freshwater invasion of the Amazon River system by stem relatives of Inia, but it remains consistent with a broader marine ancestry for Inioidea. Based on the fossil record of this group, along with Isthminia, we propose that a marine ancestor of Inia invaded Amazonia during late Miocene eustatic sea-level highs