Monte Hermoso Research Articles

CSI (Crime Scene Investigation) Beagle: Darwin's contribution to taphonomy

In the last decades, the impact of Darwin's legacy has been emphasized in many scientific fields. Nevertheless, there are still lesser-explored aspects of his life as researcher that deserve attention, such as his role as taphonomist. In this context, we highlight here this relevant facet of Darwin's investigations. During his voyage on the H.M.S. Beagle, Darwin collected numerous vertebrate fossils from South America. Particularly, in the Argentine Pampas he recorded information on the paleontology, stratigraphy, and sedimentology of different late Cenozoic fossiliferous sites. He also made observations on the preservation features of bone remains and the mechanisms that favored their fossilization, aspects currently included in the taphonomy field. In this frame, the information published in Geological Observations on South America regarding the fossils from Monte Hermoso and Punta Alta sites and his comments about the “imperfection of the geological record” on the Origin of the Species, are particularly noteworthy as an indicator of his interest in the relationship between the environmental context of preservation and the taphonomic features of bone remains. After 150 years, his scientific work continues to fascinate us. Darwin's keen eye for detail and his curiosity about the history of each fossil, about a century before taphonomy was born as a discipline, can indeed be likened to that of a Crime Scene Investigator (CSI) in some regards, reconstructing the taphonomic histories of both single remains and whole assemblages.

Holoplankton and meroplankton communities in surf zone waters of a temperate SW Atlantic sandy beach: Seasonal patterns

AbstractSandy beaches and their associated surf zones are the most common type of open shoreline, with significant ecological and socio‐economic importance. In this study, we explored the seasonal fluctuations of the surf zone holo‐ and meroplankton communities to understand the underlying environmental variables driving the temporal dynamics of each community. We also defined a surf‐zooplankton community on a temperate sandy beach (Monte Hermoso, Argentina) and related the organisms to those reported in a nearby estuary for a better understanding of the connection between adjacent coastal ecosystems. Holoplankton was very abundant (13.52–11070.4 ind m−3) and showed a strong seasonality, mainly related to the specific pattern of the two most abundant species: Acartia tonsa (>autumn) and Paracalanus parvus (>winter). This community was affected by seasonal changes in water temperature and salinity and variations in the velocity of currents, which showed that hydrodynamic forces were more significant on a short‐term time scale than seasonal ones. Meroplankton abundances (1.3–48.05 ind m−3) were significantly lower than those recorded for the holoplankton and were mainly dominated by Medusae and larvae of Bivalvia and Decapoda. This fraction also showed a clear seasonal pattern (>abundances in summer), primarily related to the seasonal changes in temperature. The abundances of the main surf‐zooplanktonic taxa were high and constant, emphasizing the importance of these waters as habitats for well‐established communities rather than being used as a transient area. Consequently, we proposed a “specific” surf‐zooplankton community for a temperate sandy beach, considering resident and non‐resident taxa. Finally, the comparison of the surf and estuarine communities indicated a faunal relationship between seascapes, highlighting the ecological role of coastal waters in planktonic life.

Microplastic levels on sandy beaches: Are the effects of tourism and coastal recreation really important?

This study assessed the effect of tourism and other recreational activities on microplastic (MP) levels and their characteristics in the sand and surf zone of the seawater. Six sites were chosen belonging to three sandy beaches with similar geomorphologic and morphodynamic characteristics but with different tourism activities. On average, a concentration of 1133.3 ± 811.3 items/kg dry weight (d.w.) and 12.7 ± 14.9 items/m3 were found in the sand and seawater samples, respectively. Fibers and films predominated and were less than 1 mm in length. In the sand, the films mainly matched the PE polymer spectra and the fibers matched PET polymer, cotton, and indigo blue dye; in the seawater samples, PP films and PET fibers prevailed. At the Pehuén-Co – Monte Hermoso Coastal Marine MPA where the flow of tourists is low, the MP levels were the lowest and the largest particles were found, mainly blue or black fibers, with less polymer diversity, cotton and PET being the most prevalent suggesting a recent input of textile fibers to this site. Moreover, the highest concentration of MPs was found on the southern site of a beach considered to be more pristine due to negligible human activity, including the smallest size pattern, mostly composed of white films or fibers with a greater diversity of polymers, predominantly PE > PET > PP. A great occurrence of PVC white films was also found in the surf zone at this site. Proximity to the mouth of a river, littoral drift, and other point sources were identified as the main sources, indicating that, apart from the local tourism and recreational activities, other sources might play a major role in the input of MPs to sandy beaches, such as extensive/intensive agricultural land use and irrigation areas.

Intraspecific craniomandibular and dental analysis of Pseudotypotherium exiguum (Mesotheriidae, Notoungulata) from Monte Hermoso, late Neogene, Buenos Aires Province, Argentina

ABSTRACT Mesotheriid taxonomy for Monte Hermoso, Buenos Aires province, Argentina is extremely complex, with much of the controversy centered on the Late Miocene–Pliocene mesotheriine notoungulate type species Pseudotypotherium pulchrum, which is a subjective junior synonym of P. exiguum. Confusion around P. exiguum intraspecific variation is exacerbated by specimens of the Pleistocene taxon Mesotherium cristatum originally defined in Toscas del Río de La Plata. As a result, remains of Monte Hermoso mesotheres have been referred to six species and four genera (Typotherium, Pseudotypotherium, Xenotherium, and Typotheriodon) during the past 100 + years. The current consensus is that Pseudotypotherium is the correct genus for Monte Hermoso mesotheres, but detailed analyses of variation, especially ontogenetic, have been lacking. We rectify that deficiency in this work through bibliographic and firsthand study of type materials and comparison of molar size (PCA of linear dimensions) and i1 ontogenetic variation (via CT) using a broad ontogenetic series. We conclude that the variation observed in Monte Hermoso mesotheres is consistent with ontogenetic and individual variation within a single species. As previously suggested, Pseudotypotherium (=Typotherium) exiguum is the valid senior synonym for Monte Hermoso mesotheres. We provide a detailed diagnosis and description of P. exiguum, including a rather complete ontogenetic series, the first for any species of Pseudotypotherium.

Resolution of the long-standing controversy over the type species of the genus Pseudotypotherium (Notoungulata, Typotheria, Mesotheriidae)

Mesotheres (Notoungulata: Typotheria) are among the most common mammals found in upper Miocene to Pliocene deposits of central Argentina, including the classic type Monte Hermoso locality, which defines the Montehermosan South American Land Mammal “Age”. Nevertheless, the correct name for the mesothere species from this site has been shrouded in uncertainty for well over a century due to questions of taxonomic priority, specimen provenance, and ontogenetic changes in dental formula. Since the mesotheres from Monte Hermoso were named, three distinct species have been formally considered as the type species of the genus: (1) Pseudotypotherium bravardi; (2) “Pseudotypotherium” maendrum; and (3) Pseudotypotherium exiguum. However, none of these species is a nominal species of the Pseudotypotherium genus; all three were originally referred to Typotherium. Article 67.2 of the International Code of Zoological Nomenclature (ICZN, 1999) indicates that only species considered as nominal species are eligible to set the type; in the case of Pseudotypotherium, these include: P. pulchrum, P. carlesi, P. hystatum, and P. carhuense. We conclude that Pseudotypotherium pulchrumF. Ameghino, 1904 (holotype MACN A 10299, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Ameghino Collection), is the type species of the mesotheriid notoungulate genus from Monte Hermoso. According to Article 68.2, F. Ameghino fixed the type by original designation in 1904 when he described P. pulchrum and included “n. g., n. sp.”. Two of the other species previously considered species P. (= T.) bravardi and P. (= T.) exiguum are invalid as type species according to Article 70.2, since their designations overlooked the previous type fixation. The third species (M. (= T.) maendrum) represents a different mesothere genus (Mesotherium) that only occurs in younger (Pleistocene) deposits. Our analysis puts an end to a historical debate that has been ongoing for more than a century regarding the identity of this well-represented late Miocene–Pliocene mesotheriine genus (Pseudotypotherium). This study provides a solid taxonomic foundation for future studies on intraspecific and ontogenetic variation of Pseudotypotherium pulchrum.

New remains of Eleutherocercus (Xenarthra, Cingulata, Glyptodontidae) from the Pampean and Northwestern regions of Argentina: morphology and phylogeny of late Neogene Doedicurinae

ABSTRACT The subfamily Doedicurinae is a monophyletic group of glyptodonts with their own anatomical features and is mostly known on the basis of the Pleistocene genus Doedicurus, one of the largest recorded taxa. The most distinctive character of the subfamily, unique within Cingulata, include the absence of ornamentation with large foramina, on the exposed surface of the carapace osteoderms. In terminal forms of the late Pleistocene, osteoderms have large foramina which tend to cross the entire thickness. The knowledge of the late Neogene diversity of the clade, as well as its evolutionary and geographical history, has increased in recent years, with important records in Argentina, where two late Miocene-Pliocene species are recognised: Eleutherocercus solidus from Catamarca and Tucumán provinces, and Eleutherocercus antiquus from Buenos Aires province. The most complete skull of E. antiquus from the early Pliocene Monte Hermoso Formation (ca. 5–4.2 Ma) is reported here. The specimen studied shows a conspicuous pathology on the parietal bones, first reported for fossil cingulates. In addition, the carapace of E. solidus is first described, on the basis of a partially complete specimen from the late Miocene-Pliocene (unknown stratigraphic level) from Tucumán province. Previous phylogenetic hypotheses of the relationships within the Doedicurinae, as well as their relationship with the remaining clades of Glyptodontidae, is tested in this study, adding new synapomorphies to the subfamily. The comparative study suggests that a third species previously proposed (E. paranaensis) from the ‘Mesopotamiense’ (late Miocene, Northeastern region of Argentina), must be considered as Eleutherocercus sp. Since their oldest record in the late Miocene, the latitudinal distribution of the Doedicurinae seems to have expanded rapidly reaching middle latitudes, particularly during the Pliocene, but during the Pleistocene (particularly the final lapse of this period), they began to retract latitudinally.

Taxonomic history and intraspecific analysis of Mesotherium cristatum (Mammalia, Notoungulata, Mesotheriidae) from the Early-Middle Pleistocene of Buenos Aires Province, Argentina

ABSTRACT We report systematic conclusions based on critical analyses of previous taxon diagnoses and systematic revisions of the Early-Middle Pleistocene mesotheriine notoungulate Mesotherium cristatum, from Buenos Aires province, Argentina. Mesotherium cristatum is a key taxon, as it is the guide species of the Ensenadan Age (Early-Middle Pleistocene), it typifies the ‘Mesotherium cristatum Biozone’, and it is the last member of the Typotheria lineage. The taxonomic history and its successive revisions are especially complex due to the lack of recognition of the ontogenetic variation for this taxon, often considered as intergeneric variations (Typotherium, Typotheridion) or also as inter-specific variations (a total of seven different species have been named). In fact, the taxonomic complexity was increased due to misidentification with specimens or taxa originally defined in the late Pliocene (i.e. Monte Hermoso, Montehermosan SALMA). We conclude that the variation among the numerous purported Early-Middle Pleistocene mesotheriine taxa is consistent with intraspecific and ontogenetic variation in a single species, here recognised as M. cristatum. This puts an end to the supposed sympatry of two other species (Mesotherium maendrum and Typotherium pachygnatum) with M. cristatum and other species that have scarcely been considered (Typotherium angustirostrum and Bravardia pampaea). Accordingly, Mesotherium is a monotypic genus.

Determinants of The Expenditure of Tourist Demand in Coastal Destinations

The aim of this work is to analyze the determinants of tourist expenditure in Monte Hermoso, a destination located in the southwest of the province of Buenos Aires, Argentina. Tourist surveys were administered during the austral summer (January-February) and considered as primary information. Socioeconomic and trip-related variables were selected to explain the determinants of the average total expenditure of tourists in this destination. The Ordinary Least Squares (OLS) method was applied. From the results obtained, it was determined that the level of income, origin, group size, and type of accommodation are the regressors that best demonstrate the spending behavior of the destination's domestic demand. Therefore, it is possible to identify the most attractive demand segments that contribute to improving competitiveness and increasing the rate of return of the destination.

REEVALUANDO EL REGISTRO FÓSIL DE LAGOSTOMUS INCISUS AMEGHINO, 1888 (RODENTIA, CAVIOMORPHA) DEL NEÓGENO TARDÍO DEL SUR DE AMÉRICA DEL SUR

The extinct vizcacha Lagostomus incisus is a particular rodent recorded in Pliocene sediments of Buenos Aires Province (Argentina), including the montehermosan “Irenean” Fauna and Monte Hermoso Formation, and the chapadmalalan Chapadmalal Formation. Its characteristic skull and cheek teeth anatomy permit to easily identify it even with fragmentary material. In this work, the fossil record of L. incisus is reassessed, being recognized in several units where it had not been reported before: the Unit B of the Saldungaray Formation, the Quequén Grande Local Fauna, and the Barker Formation in Buenos Aires Province (Argentina), and the San José Member of the Raigón Formation in Maldonado Department (Uruguay). These new records extend the distribution of L. incisus to most of central Buenos Aires Province in Argentina and southern Uruguay. Additionally, the recent radiometric dates of some of the units with records of L. incisus permit to confidently limit the temporal range of this species to the late early–early late Pliocene.

Oldest Record of the Pit-Viper Bothrops (Squamata, Viperidae), from the Lower Pliocene of Buenos Aires Province, Argentina

The fossil record of the genus Bothrops is still sparse in South America. Most records belong to extant species recovered in strata not older than the late Pleistocene. The genus was also tentatively reported from the early Pliocene and early–middle Pleistocene of Buenos Aires province, Argentina, based on fragmentary specimens. The aim of the present contribution is to report the partial vertebral column of a viperid snake discovered in the lower Pliocene layers of Farola de Monte Hermoso locality, southern Buenos Aires province. The specimen can be referred to the extant genus Bothrops, representing the oldest occurrence for this taxon. This finding supports the hypothesis sustained by previous authors that indicate a “stasis” in the evolution of the South American herpetofauna since the late Neogene, at least.

REASSESSING THE FOSSIL RECORD OF LAGOSTOMUS INCISUS AMEGHINO, 1888 (RODENTIA, CAVIOMORPHA) FROM THE LATE NEOGENE OF SOUTHERN SOUTH AMERICA

The extinct vizcacha Lagostomus incisus is a particular rodent recorded in Pliocene sediments of Buenos Aires Province (Argentina), including the montehermosan “Irenean” Fauna and Monte Hermoso Formation, and the chapadmalalan Chapadmalal Formation. Its characteristic skull and cheek teeth anatomy permit to easily identify it even with fragmentary material. In this work, the fossil record of L. incisus is reassessed, being recognized in several units where it had not been reported before: the Unit B of the Saldungaray Formation, the Quequen Grande Local Fauna, and the Barker Formation in Buenos Aires Province (Argentina), and the San Jose Member of the Raigon Formation in Maldonado Department (Uruguay). These new records extend the distribution of L. incisus to most of central Buenos Aires Province in Argentina and southern Uruguay. Additionally, the recent radiometric dates of some of the units with records of L. incisus permit to confidently limit the temporal range of this species to the late early–early late Pliocene.

Wetlands in the coastal dunes between Monte Hermoso and Pehuen Có, Buenos Aires province, Argentina. Hydrological typification

This research, which is part of a larger research project, aims to recognize and typify the wetland sectors which are identified in the dunes line between the Monte Hermoso city and Pehuen Có village, in the southwest coast of Buenos Aires province, Argentina. A well-known hydrological characterization methodology is applied, which takes into account factors such as water origin, emptying mode, hydroperiod, renewal rate, and hydrochemical composition. The study is based on field and laboratory information, scientific background works and interpretation of satellite images. The presence and hydrological functioning of these wetlands are essentially linked to the aquifer`s hydrodynamics and, in particular, to the discharge zones. The presence of superficial water between the dunes constitutes a singularity of these natural spaces. This contribution allows knowing some wetlands in the coastal dunes, locate them and define their level of integrity. It is necessary to investigate the spatial variability and temporal hydrochemical evolution. It warns about the environmental importance of these environments and their need for proper management and conservation.

Phylogenetic affinities and morphology of the Pliocene cathartiform Dryornis pampeanus Moreno & Mercerat

AbstractThe fossil bird Dryornis pampeanus Moreno & Mercerat, is reinterpreted after examination of new referred material (humerus, coracoid, fragments of ulna, radius, scapula, sternum and tibiotarsus) from the Pliocene Chapadmalal Formation of Argentina. The current diagnosis is emended in the light of important considerations that cast doubt on the previous attribution of the taxon to condors. The phylogenetic position of D. pampeanus was tested in a series of maximum parsimony analyses that included all seven living Cathartiformes and 207 osteological characters. The phylogenetic analyses placed D. pampeanus as the sister taxon of extant vultures. An estimation of 26 kg for the mass, positions D. pampeanus as the largest cathartiform to have ever lived. The presence of this taxon in both the Monte Hermoso and Chapadmalal Formations not only extends the stratigraphic range of the species, but also supports the idea that they were partially contemporaneous during the early Pliocene. The dependence of the vultures on ephemeral carrion suggests that they have especially large ranges. The sites from which the lectotype and new material were recovered (Monte Hermoso and Chapadmalal, respectively) are only 400 km apart, suggesting that the two sites were at least partly contemporaneous.

Fossil record of a Characiform in the Monte Hermoso Formation (lower Pliocene), Buenos Aires, Argentina. Palaeobiogeographical implications

The fossil record of fishes from the Farola de Monte Hermoso locality (lower Pliocene) in the southern Buenos Aires province, Argentina, shows an unusual composition. The locality at the southern boundary of the Brazilian Ichthyogeographic Realm. However, its fossil record is composed of fossil fishes that are not necessarily related to Brazilian lineages, namely indeterminate siluriforms, trichomycterid catfishes, and percomorphaceans. The aim of the present contribution is to describe and report for the first time isolated specimens belonging to Characidae fishes. In the Pampean region the fossil record of characids is restricted to Oligosarcus Günther, 1864 sp. from the late-middle Pleistocene. The present finding fills a temporal gap between the Paleogene and Quaternary reports and indicates that Brazilian fish lineages were present in the area by early Pliocene times, and may constitute an indirect evidence of the evolution of the basins in the southern Pampean Area.

The Phreatic Aquifer In The Coastal Dunes Of Southwestern Buenos Aires Province, Argentina. Factors Conditioning Groundwater Quality

In the southwest of the province of Buenos Aires, a chain of coastal dunes contains a phreatic aquifer, which is the only source of drinking water in most of the seaside cities. The objective of this study is to analyze the geological, hydrogeological and anthropic activities that affect the quality of groundwater for human consumption, between the cities of Monte Hermoso and Punta Alta. Methodologically, the research is developed based on the study of antecedent information, field recognition, well census, cutting analysis, interpretation of electrical tomography and hydrochemical data. The results relate the quality of the groundwater with the lithological and stratigraphic characteristics of the area, recognizing the natural presence of trace elements such as F, As, Fe and Mn as well as undesirable organoleptic characteristics (smell, color and taste). In addition, the occupation of the land with potentially contaminating anthropic actions (cesspool or absorbent wells, farmyards, open-air dumps, etc.) is observed. This research aims to contribute to hydrogeological knowledge, providing the conceptual basis for the exploitation and management of the aquifer, in an area where water supply is entirely based on the groundwater resource.

LA BAHÍA QUE ILUMINÓ A DARWIN

Los últimos estudios sobre los hallazgos y observaciones que Darwin hiciera durante su viaje a bordo del Beagle señalan al área de Bahía Blanca, en el sudoeste de la región pampeana como una de las escalas más inspiradoras para la elaboración de su teoría de la evolución. Los sitios de Punta Alta y Monte Hermoso con sus restos fósiles de mamíferos cenozoicos fueron una de las mayores motivaciones del joven naturalista. Las exploraciones paleontológicas junto a las observaciones que realizara sobre la fauna y la flora de la región constituyen la evidencia de que esta zona fue un componente crucial para su pensamiento transmutacional aunque los historiadores lo hayan pasado por alto o minimizado.

De La Activación Patrimonial a La Valorización Turística Estudio de Caso: Paleoturismo en la Reserva Geológica, Paleontológica y Arqueológica Pehuen Co, Monte Hermoso, Argentina

De La Activación Patrimonial a La Valorización Turística Estudio de Caso: Paleoturismo en la Reserva Geológica, Paleontológica y Arqueológica Pehuen Co, Monte Hermoso, Argentina

Marcación y recaptura del gatuzo (Mustelus schmitti) en el Ecosistema Costero Bonaerense (Argentina)

El presente trabajo está referido a los primeros resultados obtenidos sobre marcado y recaptura en el gatuzo, Mustelus schmitti, como medio para reconocer sus desplazamientos y migraciones en el Ecosistema Costero Bonaerense (ECB). Este tiburón es relevante no sólo por su gran abundancia a lo largo del ECB sino también por su importancia comercial para la flota pesquera de arrastre argentina. Entre noviembre de 2010 y mayo 2011 se marcaron 2.483 ejemplares cerca de Monte Hermoso, dentro del sector marino conocido como “El Rincón”, utilizando como plataforma una embarcación de la flota artesanal. Se logró recuperar 43 individuos entre 2010 y 2013. A partir del análisis de los individuos recapturados se señalaron los patrones de movimientos, migración, distribución espacial y temporal en el ECB, y además se discutieron y relacionaron dichos patrones con el ciclo de vida. Los resultados pusieron en evidencia la utilización por parte del gatuzo de áreas extensas, mayoritariamente costeras, sin alta afinidad con áreas particulares. Este es el modelo tradicional propuesto para tiburones pequeños como el gatuzo. Sin embargo, la modalidad reproductiva indicaría un ajuste al modelo señalado para grandes tiburones. Por lo tanto, el gatuzo en su comportamiento parece contener aspectos correspondientes a ambas modalidades con fidelidad por los sitios de reproducción pero sin evidencias de filopatría.

New record of the soft-bodied genus Franciscideres (Kinorhyncha) from Argentina, with notes on its movement and morphological variation.

Samples collected from Monte Hermoso, Buenos Aires Province, Argentina revealed the presence of specimens of the genus Franciscideres Dal Zotto et al., 2013, previously known only from Brazil. This morphotype seems to differ from the only known species, Franciscideres kalenesos Dal Zotto et al., 2013, in the following characters: (1) presence of ventrolateral tubes on segment 1, (2) introvert features, (3) each segment composed of a closed cuticular ring, (4) trunk cuticle ornamented by a secondary fringe of knob-like structures, (5) posterior margin of segment 10 ventrally terminating in two lateral and one broad triangular lobes, (6) posterior margin of segment 11 centrally terminating in four lobes (7) lateral terminal spines armed with thorn-like processes, (8) pores/sensory spots/gland cells distribution and (9) sexual dimorphism in segments 10 and 11. Because of the lack of full information about F. kalenesos from Brazil, we consider the new exemplars as Franciscideres cf. kalenesos. Additionally, we provide new information about the movement of this species using light microscopy and we compare these movements with those of other meiofaunal inhabitants.

New vertebrates from the Late Miocene of Entre Ríos Province, Argentina: diversity, age, and paleoenvironment

New remains of fossil vertebrates recovered from two localities in Entre Ríos Province, Argentina, are studied. The specimens were found at Toma Vieja and Arroyo Chapetón localities, where the fossiliferous Lower Member (“Mesopotamiense”, Late Miocene) of Ituzaingó Formation (Late Miocene–Pliocene) crops out. The new findings contribute to the high diversity of fossil vertebrates largely known for this unit. The specimens correspond to Perciformes indet. and Pimelodidae indet. (Pisces), Macranhinga paranensis (Aves), Scirrotherium carinatum, Brachytherium cuspidatum, Proterotheriinae indet., Hydrochoerinae indet., and cf. Prodolichotis (Mammalia). Considering the relationship between the fauna present in this unit and that from other mammal-bearing Neogene units (e.g., Arroyo Chasicó, Andalhuala, Cerro Azul, and Monte Hermoso formations), the “Mesopotamiense” is a faunal combination of Chasicoan and Huayquerian taxa deposited during the end of the Tortonian or the early Messinian. From a paleoenvironmental point of view, the “Mesopotamiense” faunal assemblage is indicative of a mosaic of ecological niches developed under tropical–subtropical conditions.