Patagonia Research Articles

Flora vascular de alta montaña en la Patagonia argentina

Knowledge of the local biodiversity is extremely important to design conservation strategies. The goals of the present work are to provide a list of native species recorded in the high mountains of Argentine Patagonia, with comments about their distribution, habitat and habit, and to identify the most vulnerable species for inhabiting small geographical areas and/or have populations with few individuals, for inhabit specific habitats, for not being included in protected areas and/or inhabiting territories subject to human activities. This annotated list, resulting from the field survey of 111 mountains between 1992 and 2022, includes 550 native species belonging to 185 genera and 69 families. Of these, 124 species have restricted geographic distributions, 69 are exclusive to high mountains, and 13 species and 10 populations are in a vulnerable situation. The data in this contribution are important for future decisions when preparing management plans for existing protected areas, to evaluate the creation of new reserves, and as a database for future comparisons.

Species composition and assemblage analysis of fishes caught as bycatch by the Patagonian shrimp fishery in the southwest Atlantic.

Bottom trawl fishing is the most used worldwide gear generating large amounts of discards due to bycatch of a variety of species. Shrimp fisheries are recognized for their high incidence in global discards. In waters of Patagonia Argentina (43°S - 47°S) an industrial shrimp fishery of high economic value is developed whose target species is the Patagonian shrimp Pleoticus muelleri. The information presented in this study comprises a period of 12 years (2003-2014) and it was gathered by the On-board Observer Program. The Program collects information of all species captured in the fishing fleets. The data analyzed corresponds to the double-rigged otter trawler fleet and the coastal fleet. The fish bycatch composition was characterized in both fleets and the frequencies of occurrence of species and the assemblage areas were analyzed. A total of 101 fish species were identified (59 families) of which 69 were bony fishes, 29 cartilaginous fishes and three species of jawless fishes. The assemblages described correspond to coastal and deep waters, and they are integrated by temperate and subtropical species pointing out the area as an ecotonal zone.

Tectonically Controlled Felsic Tuff Ring Volcanism Link to Small-Scale Pull-Apart Basin: An Example from a Jurassic Backarc Basin of Western Patagonia Argentina

Tectonically Controlled Felsic Tuff Ring Volcanism Link to Small-Scale Pull-Apart Basin: An Example from a Jurassic Backarc Basin of Western Patagonia Argentina

Time of immersion of bodies found in water in Northern Patagonia Argentina

IntroductionThe estimation of the immersion time of bodies recovered from the water, through the evaluation of the cadaveric changes, allows inferring the time that they have remained in the water regardless of the cause of death. In the present study, the Daily Accumulation of Degrees (ADG) method is analyzed for the calculation of the immersion interval in bodies recovered from the water in 36 bodies with a known interval of permanence in the water. Material and methodsA total of 161 bodies were recovered from the water between 2007 and 2022, in 41 cases there was data to be analyzed by the ADG method and 36 were suitable for analysis of the method when confronted with the known intervals of immersion of the bodies. ResultsThe comparison of calculation by Daily Accumulation of Degrees versus Known Immersion Interval, of the sample of 36 cases, showed that the difference in days obtained is statistically significant (p 0.48 > 0.005). In 16 cases (44.4%) there was an underestimation by the Daily Accumulation of Degrees method with respect to the time spent in the known water that differed by an average of 40%, and in 18 cases (50%) an overestimation of 41%. Based on the observation of the cadaveric changes, the month of the year and the water temperature, a table was made to estimate the Postmortal Interval of Immersion for watercourses in Northern Patagonia. ConclusionThe method of Daily Accumulation of Degrees in bodies recovered from the water to estimate the immersion interval may give a false perception of accuracy due to the complexity of integrating all the changing factors that affect human decomposition in aquatic environments.

Latest Maastrichtian middle- and high-latitude mosasaurs and fish isotopic composition: carbon source, thermoregulation strategy, and thermal latitudinal gradient

AbstractHere we report high-latitude stable isotope compositions of Maastrichtian fossil fish and marine reptiles (mainly mosasaurs) from Antarctica (64°S paleolatitude) and compare them with mid-paleolatitude samples from Argentine Patagonia (45°S). Disparities between the δ13C values of bony fish and marine reptiles correspond to differences in the foraging ground (distance from the shore and depth), while dramatically higher δ13C values (by 18‰) in shark enameloid cannot be explained through ecology and are here imputed to biomineralization. Comparison with extant vertebrates suggests that the diet alone can explain the offset observed between bony fish and mosasaurs; however, breath holding due to a diving behavior in mosasaurs may have had some impact on their δ13C values, as previously suggested. The δ18OPO4 values of the remains confirm a relatively stable, elevated body temperature for marine reptiles, meaning that they were thermoregulators. We calculated a water temperature of ~8°C for Antarctica from the fish δ18OPO4 values, warmer than present-day temperatures and consistent with the absence of polar ice sheets during the latest Maastrichtian. Our fish data greatly extend the latitudinal range of Late Cretaceous fish δ18OPO4 values and result in a thermal gradient of 0.4°C/1° of latitude when combined with literature data.

δ13C and δ15N of plants in a longitudinal transect from the Andes to the Atlantic coast: Terrestrial baseline for paleodietary and paleocological studies

The application of stable isotopes in ecology, archeology or paleocology highlight the need to understand the variability of the isotopic baselines, as a fundamental step to know the spatio-temporal variability of consumers. The aim of this research is to study the δ13C and δ15N variability in modern plants along a longitudinal transect − 400 km - in southern Patagonia in order to establish the terrestrial vegetation baseline of the food chains in relation to the climatic and environmental variability of the region. The study area, between 47° and 49° south latitude Patagonia Argentina, covered different altitudes, temperatures, vegetation types, and precipitation gradients.δ13C and δ15N values were obtained for 211 samples from 13 different sampling loci. Vegetation surveys indicated a sharp change from temperate forests in the most humid west of the transect - trees and lichens were only present in the forests -, to steppe, dominated by shrubs and grasses. Stable isotopes of vegetation follow the climate gradient, with higher δ15N and δ13C values in the more arid steppe than in the forest sites. The lineal best model for each stable isotope, included mean annual precipitation and biological types as explanatory variable, and explained 58.7 % of the variability for δ15N, and 45.5 % for δ13C. On the broad scale, from the Atlantic coast to the Andes, we can assess the degree of agreement between the isotopic variations recorded in plants and herbivores. In this way, the isotopic variability recorded in both, plants and herbivores, provides unique opportunities to investigate the differential use of space and mobility, both among hunter-gatherer societies and among Patagonian herbivores.

Polyphosphate accumulation and cell-surface properties by autochthonous bacteria from Argentinian Patagonia

Bacteria persisting in environments contaminated with polycyclic aromatic hydrocarbons (PAHs) have developed physiological mechanisms to counteract environmental stress. Inorganic polyphosphate accumulation represents one of these possible mechanisms. Likewise, properties such as cell-surface hydrophobicity, auto-aggregation, biofilm formation and bioemulsifying activity could facilitate interaction of microorganisms with hydrophobic organic compounds. In this work, these physiological properties were compared in indigenous bacteria from polluted sediments from Argentinian Patagonia, which were cultivated in two culture media (LBm and JPP) as a way to improve in the next future the PAHs removal. The highest hydrophobicity values were obtained in Rhodococcus strains, while Bacillus sp. B18 showed the highest auto-aggregation percentage and emulsion index. The highest numerical values of biofilm formation were determined in Rhodococcus sp. F27, Pseudomonas sp. P26, and Gordonia sp. H19 either on hydrophilic or on hydrophobic support. The qualitative and quantitative polyP determinations confirmed the presence of this biopolymer in the strains evaluated. The highest intracellular phosphate mean values were obtained in Bacillus sp. B18 in LBm and Rhodococcus erythropolis 20 in JPP. The bacteria evaluated belonging to different genera showed significant differences in their cell-surface characteristics, bioemulsifying activity and polyP accumulation. The low-cost JPP culture medium was selected for future contaminant removal studies.

How do understory trees deal with small canopy openings? The case of release in growth following drought-induced tree mortality

Hotter droughts have become important drivers of change in the structure of forest canopy, and the role of structural loss of overstory trees is gaining attention as an important factor that would trigger changes in understory behavior. The projection of understory individuals, allows us to analyze the potential future of the forests. Through a dendroecological approach, we evaluated growth responses in understory Austrocedrus chilensis trees growing underneath canopy that experienced tree mortality as a consequence of severe droughts occurred in Patagonia Argentina. We analyze the climatic response, tree growth patterns and drought resilience of understory components in three A. chilensis mixed forests. Tree growth was significantly reduced by drought, highlighting the climatic sensitivity of understory individuals; but indirectly, tree growth also showed releases associated with the openings due to canopy mortality. Thus, we found that understory tree growth increased over time. Our results demonstrated that growth performance of understory A. chilensis trees become largely modeled by a combination of the releases associated with changes of the canopy and their ability to withstand adverse weather conditions. We were able to show a clear capacity of understory A. chilensis to cope with drought events by increasing its growth, taking advantage of the disturbance in the upper layers of the canopy, while resisting successive dry years. However, the shadier environment underneath canopy did not buffered drought conditions, and understory A. chilensis trees suffers the effects of droughts. Considering an increase in drought frequency and intensity in climate predictions, with the consequent openings due to overstory tree mortality, understory species behavior will result as a complex interaction among a potential increase in understory vulnerability to more severe droughts, and the opportunity of canopy ascension.

Linear and ponderal growth changes in boys and girls from Puerto Madryn (Patagonia, Argentina) between 2001 and 2016

Background: The phenotypic plasticity in growth pattern that takes place over time is described as “secular trend”. The presence of secular changes evidences shifts in the environmental conditions under which a population lives. In this regard, the study of the population residing in the northeast of Argentine Patagonia is interesting because it underwent a rapid demographic growth and urban sprawl in the last 50 years.
 Objective: To compare height and body weight of two groups of boys and girls between 6 and 14 years old from Puerto Madryn (northeast of Argentine Patagonia) and estimate secular trend changes during the first decades of 21st century.
 Sample and Methods: Height and body weight of two groups of schoolchildren were compared. Data of the first group (G1) was collected in the 2001–2006 period, and of the second (G2) during 2014–2016.
 To analyze the comparison between groups, the Friedman and Wilcoxon test (p < 0.05) were used. Centile values (3rd, 50th and 97th) of the variables by sex and age in both groups were also calculated. Then, they were compared using the Wilcoxon test.
 Results: Both sexes showed statistically significant differences for height in all centiles and for body weight in the 50th and 97th centiles. G2 values were above G1 for most ages.
 Conclusion: Boys and girls from Puerto Madryn show a positive secular trend in linear and ponderal growth patterns. These changes, registered during the first decades of the 21st century, are possibly related to the urban sprawl of the city and the variations in the associated socio-environmental and demographic conditions.

Paleoenvironmental Changes for the Last 3000 Cal Years BP in the Pueyrredón Lake Basin, Southern Patagonia, Argentina

Patagonian shrub and ecotonal communities were sensitive to past environmental changes and thus may also be affected by future ones. Therefore, their paleoecological study constitutes a valuable tool to understand the way in which these plant communities respond to the forcings responsible for environmental variability. The aim of this paper is to reconstruct the vegetation dynamics of the Pueyrredón Lake area (47°25′55′′ S; 72°0.7′7′′ W) for the last 3000 cal yr BP and to contextualize these changes in a regional paleoclimatic framework. The results indicate that at the beginning of the 2900 cal yr BP, the vegetation in the northwest of Santa Cruz, Argentinian Patagonia, was represented by a grass-shrub steppe associated with forest–shrub steppe ecotonal elements. This information correlates with the larger-scale environmental inferences described for the period, which indicate an increase in moisture availability due to the weakening of the westerly winds. A marked change to arid conditions is indicated in the last 1050 cal yr BP, with the establishment and development of different shrub steppe communities and the lack of ecotonal elements. Although vegetation was sensitive to changes in moisture conditions related to the variability of the westerly winds, there is evidence of differences in the composition of shrub vegetation regarding the sequences analyzed. Variations in pollen proportions of the shrub steppes in the Pueyrredón Lake area suggest that changes in vegetation are not only due to climate variability but also local factors in the areas where shrub communities grow. The integration of the information with other Patagonian sequences allowed to frame these changes in a regional context. The results obtained provide useful information to understand the way vegetation changed in the past and the manner in which it may respond to future changes.

A new species of Hannemania (Trombidiformes: Leeuwenhoekiidae) parasitizing the endemic and endangered frog, Atelognathus reverberii (Anura: Batrachylidae) from Argentinian Patagonia

Chigger mites of the genus Hannemania Oudemans 1911 (Acari: Leeuwenhoekiidae) are subcutaneous parasites of amphibians. To date, 28 species have been reported from the Americas and Oceania. In Argentina, only six species have been recorded: H. achalai Alzuet & Mauri 1987, H. argentina Lahille 1927, H. edwardsi Sambon 1928, H. hobdayi Sambon 1928, H. minor Alzuet & Mauri 1987 and, H. samboni Ewing 1931. Those species were recorded parasitizing frogs of the genera Bufo Garsault (Bufonidae), Hypsiboas Wagler (Hylidae), Leptodactylus Fitzinger (Leptodactylidae), Nannophryne Günther (Bufonidae), Odontophrynus Reinhardt & Lütken (Odontophrynidae) and, Pleurodema Tschudi (Leptodactylidae). Most of these records are from the northern, northeastern and Andean regions in Argentina. In Argentinean Patagonia, the Meseta de Somuncurá is a protected natural area of great biological interest due to the strong endemism of fauna and flora (at least 14 endemic species). Only, H. hobdayi and H. samboni have been described from Argentinean Patagonia. The endemic Laguna Raimunda frog, Atelognathus reverberii (Cei) (Anura: Batrachylidae), is an endangered species with a distribution in the semi-permanent volcanic clay lagoons of Meseta de Somuncurá. The ecological characteristics of A. reverberii populations make it vulnerable to habitat degradation and parasitic diseases. This study aimed to describe a potentially new species of Hannemania collected as a parasite of A. reverberii in Meseta de Somuncurá, Río Negro, Argentina. A sample of 11 mites was cleared in lactophenol solution, slide-mounted in Hoyer’s medium, and observed using an optical microscope with Phase contrast and DIC. The mites have a palpal formula that differs from those of the previously described Hannemania species from Argentina and the rest of South America. They also differ from the related species in the number of eupathidia on the genu of leg I (σ) and the number and arrangement of dorsal opisthosomal setae. We consider that the species morphological differences and geographic isolation are sufficient to propose a novel species of the genus Hannemania. Herein, we present the first record of Hannemania parasitizing A. reverberii. As this amphibian is considered endangered, this novel species of Hannemania is probably threatened. This study contributes to the knowledge of this parasitic mite. In future studies, it will be necessary to consider molecular data of Argentinian Hannemania species to achieve a better understanding of the systematics of the genus.

Composition and Spatial Variation of Germinable Seed Bank in Burned Nothofagus pumilio Forests in Patagonia Argentina

The availability of soil-stored seed determines initial plant functional types in post-fire landscapes. We evaluated the post-fire regeneration of Nothofagus pumilio forests, in Patagonia, Argentina, analyzing the soil seed bank (SSB) and the above-ground vegetation (AV). At three sites: La Colisión, Río Turbio and Monte Zeballos, burned in 2008, 1980 and 1941, respectively, we sampled the SSB and AV in two transects from the edge of the remaining forest, up to 90 m within the burned area, and recorded the emergence (198 soil samples) and presence of vascular species. To determine the effect of the distance to the remnant forest on the germinable seed bank, we performed simple linear regression analysis through the use of linear mixed-effect models, and we analyzed the similarity between the composition of SSB and AV with PERMANOVA. The emergence of plant growth forms had different patterns in relation to the distance from the forest in the three sites, which might be associated with the time of fire occurrence, and specific characteristics of each site. The emergence of N. pumilio was registered at more than one distance at the recent burning site. Herbs constituted the main source of cover with 69% of the composition, and native/endemic species represented 71%. This study contributes to the understanding of the relationship between the seed bank and standing vegetation and a better understanding of the resilience of post-fire N. pumilio forests. Our findings suggest that from 15–20 m from the edge, the SSB would be insufficient to ensure the spontaneous recovery of the forest, making active restoration necessary in order to tend to a recovery of the structure and functionality of the original community.

Assessment of ground deformation and seismicity in two areas of intense hydrocarbon production in the Argentinian Patagonia

The exploitation of both conventional and unconventional hydrocarbons may lead to still not well-known environmental consequences such as ground deformation and induced/triggered seismicity. Identifying and characterizing these effects is fundamental for prevention or mitigation purposes, especially when they impact populated areas. Two case studies of such effects on hydrocarbon-producing basins in Argentina, the Neuquén and the Golfo de San Jorge, are presented in this work. The intense hydrocarbon production activities in recent years and their potential link with the occurrence of two earthquakes of magnitude 4.9 and 5 near the operating well fields is assessed. A joint analysis of satellite radar interferometry and records of fluid injection and extraction demonstrate that, between 2017 and 2020, vertical ground displacements occurred in both study areas over active well fields that might indicate a correlation to hydrocarbon production activities. Coseismic deformation models of the two earthquakes constrain source depths to less than 2 km. The absence of seismicity before the beginning of the hydrocarbon activities in both areas, and the occurrence of the two largest and shallow earthquakes in the vicinity of the active well fields just after intensive production periods, points towards the potential association between both phenomena.

Borings and coprolites of termites in fossil woods from the Lower Cretaceous (Kachaike Formation) of Argentinean Patagonia

Borings filled with coprolites in silicified conifer woods from the Lower Cretaceous (Albian) of the Kachaike Formation, Santa Cruz Province, Argentina are described for the first time. Coprolites are approximately hexagonal in cross-section, like those produced by extant Kalotermitidae, and occur inside borings in the secondary xylem. The presence of this family in the mid-Cretaceous ecosystems of Patagonia indicates arid climatic conditions consistent with previous geological, palynological and paleoxylological studies for this time interval in the Austral Basin. This also adds to other worldwide records of termites from the Lower Cretaceous, supporting their ecological importance as consumers and recyclers of lignified organic matter in dry forests from this period on to today.

European starlings expand into Patagonia. Time for action

European starlings ( Sturnus vulgaris ) were introduced ca. 40 years ago to South America, where they naturalized to central and northern Argentina, now reaching some neighboring countries. While Patagonia (southern Argentina and Chile) has remained free of European starlings (ES) in the past, they are now present along its northern boundary. Our objectives were to 1) investigate the factors explaining this recent invasion, and 2) predict how starlings might expand across southernmost America based on niche modeling using landform, land cover, and climatic variables representing conditions that may limit ES. Based on records from community science, informants, and our own observations, we conclude that two parallel processes generated new population nodes in northern Patagonia: 1) a southwards expansion from their core areas near the Atlantic coast (generating an incipient population node in NE Patagonia), and 2) birds released or escaped from captivity (generating an isolated population node in north-central Patagonia). Community science data was most useful from 2018 onwards, while data from informants was key to understand previous events (e.g., first ES confiscated from illegal trade in 2008; first free ranging ES seen in 2014). The most parsimonious model confirmed our prediction that human transformed lands in several portions within the target area are suitable for ES establishment, both in Chile and Argentina. Null suitability was modeled for the lands in southernmost Patagonia (all cover types). Desert lands (Patagonian steppe, Monte Desert, High Andes) that skirt the Andean temperate forests on the north, and most of the Andean forests, turned out to be unsuitable (especially with increasing latitude). Conversely, most of coastal Argentine Patagonia and the human-transformed lands of south-central Chile emerged as moderately suitable habitat for ES. Because the riverine areas under current ES colonization in northern Patagonia are fovourable for ES (i.e., agricultural and urban lands with abundant nesting sites), without control actions, this species might soon spread over ca. 5000 km2 around the Colorado and Negro rivers, affecting their agricultural industry. These rivers, which run west-east through desert lands unsuitable for ES, now represent corridors into south-Andean ecosystems, as they are surrounded by treed land (willows and poplars introduced from Europe) not originally available, connecting formerly separate ecoregions. In case ES manage to reach the eastern slopes of the Andes, they might cross to Chile through low elevation passes (<1000 masl) available south of ca. 38°S. The valleys of south-central Chile are both suitable habitat for ES and valuable productive lands that may be threatened by the invasion. We present management suggestions, and advocate for the development of a bi-national strategy to retard, prevent and alleviate the far-reaching impacts ES may exert on America’s southernmost ecosystems and resources.

The other sheep, resistant but forgotten: Archetypal characterization of Linca sheep farmers in Argentine Patagonia

Identifying and understanding how resilience is generated in a local socioecological system is essential for the design of future conservation strategies. The Linca sheep represents one of the most important – but least known – biocultural legacies of the Mapuche people in Patagonia. These sheep, which arrived in the region along with the conquistadors more than three centuries ago, have been almost completely displaced by the Merino sheep breed. In this work we analyse the principal components that characterise the relictual producers of Linca sheep. These components are the key for the conservation of this traditional practice and takes a substantial part of local zoological knowledge (LZK). Interviews with artisans (n = 51) who know, require or use Linca wool, either know the breeders, enabled us to contact and interview 13 families who preserve these sheep. Based on an interpretative study we identified 3 biocultural components and 11 analytical variables. Through this analysis of the archetypes, within this universe of producers, we recognized three profiles: Veteran, Tenacious, and Emotionally Attached. The families who have preserved this ancient practice were assigned to one of the three groups based on the shortest Euclidean distance and information obtained from the interviews. Among the main characteristics of these relictual producers the important role played by women stands out, as they preserve and transmit knowledge of the textile language and maintain the diversity of the Linca sheep, transforming their family units into guardians of the biocultural inheritance of this local breed.

Mitochondrial and microsatellite data show close genetic relationships between Dibothriocephalus latus from South America (Argentina) and Europe (the Alpine lakes region).

The most frequent causative agent of diphyllobothriosis, a fish-borne parasitic zoonosis, is the broad fish tapeworm Dibothriocephalus latus distributed mainly throughout the Holarctic region. The larval stages of the tapeworm were also detected in native and introduced freshwater fish in several lakes in South America, particularly in the north-western Patagonia in Argentina. The main objective of the present study was to determine the genetic structure of D. latus from rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and brook trout (Salvelinus fontinalis) from Gutiérrez Lake and Alicura Reservoir in Argentina using the sequences of three mitochondrial genes (cox1, cob, and nad3) and six polymorphic microsatellite loci. The results were compared with the corresponding molecular data of D. latus from Europe (Switzerland and Italy; the Alpine lakes region) and Asia (Siberia, Russia). Only one concatenated haplotype identical with the con-Ha1 specific for D. latus from the Alpine lakes region was detected in all individuals from Argentina. Three different alleles were detected in five out of six analysed microsatellite loci, indicating the presence of three sets of chromosomes. The same structure of microsatellite loci was recently observed in D. latus from Switzerland and Italy, in which triploidy was previously confirmed by cytogenetic study. The data on the mitochondrial genes, the allelic structure of microsatellite loci, and the principal coordinate analysis showed close genetic relationships between D. latus from Argentina and the Alpine lakes region, thus supporting the hypothesis of the European origin of the broad fish tapeworm from South America.

A new species of Attinopora (Bryozoa, Cinctiporidae) from the early Miocene of Atlantic Patagonia

Cinctiporidae is a family of cyclostome bryozoans that ranged from the Paleocene to Recent; however, they also include a questionable record from the Upper Cretaceous of South Africa. Most cinctiporids occur in the Paleocene to Pleistocene strata of New Zealand and the Chatham Islands, with only two living species now found in New Zealand. This study confirms the presence of cinctiporid bryozoans in South America with the description of a new fossil species, Attinopora atlantica sp. nov., based on specimens found in early Miocene deposits of the Monte León Formation, along the Atlantic margin of Argentine Patagonia. Attinopora atlantica sp. nov. differs from the other known species of Attinopora in having a much higher number of zooids per annular ring. The presence of cinctiporids in the early Miocene of Patagonia supports hypothesized biogeographical links between South America and Australasia during the early Neogene.

Sisal wool skin disease in Merino sheep in the Argentine Patagonia region: Identification and molecular diagnosis of Corynebacterium bovis from skin lesions.

Sisal wool condition is a skin disease affecting Merino sheep in the Argentine Patagonia region. Corynebacterium spp. isolates have previously been isolated from skin swabs from lesions, while specific identification of the bacteria involved has not been reported. The aim of this work was to characterize the bacterial agent isolated from sisal wool lesions and to develop a diagnostic method for field surveillance. Molecular identification of a collection of 72 isolates obtained previously was performed using PCR and 16S rRNA and rpoB sequencing. A field survey was carried out on two farms in the Río Negro province of Argentine Patagonia. Swab samples from sheep with and without skin lesions were collected and analysed by PCR and culture. Isolates analysed were confirmed by sequencing as Corynebacterium bovis. Using a PCR test without culture step, all field samples from affected sheep were positive for C.bovis; samples from the healthy skin from the same animals or clinically healthy sheep all were negative. Sisal wool skin disease was associated with C.bovis infection based on culture and PCR methods; the latter may be useful for helping to pursue a disease control strategy.

Palaeobiological inferences for the South American dicraeosaurid Brachytrachelopan mesai (Dinosauria; Sauropoda) based on bone histology of the holotype

ABSTRACT Brachytrachelopan is a dicraeosaurid sauropod that comes from the Jurassic of Argentine Patagonia. With the purpose to infer different palaeobiological traits (e.g., ontogenetic stage, growth dynamics, temporal correlation between morphological and anatomical parameters of maturation), we perform an osteohistological study on different postcranial elements from the holotype individual, including axial (i.e., cervical hemispinous process, dorsal ribs) and appendicular (i.e., femur) bones. The absence of a distinct external fundamental system indicates that the individual died before full body size achievement (i.e., somatic maturity). Furthermore, although not conclusive, the histological data suggest that despite its body size, which is comparable with fully grown individuals of other dicraeosaurid taxa, the individual also corresponds to a sexually immature specimen. Predominance of highly vascularised fibrolamelar with only a cyclical growth mark (CGM) in the outer cortex of the femur reveals a sustained, accelerated growth, typical feature of neosauropod dinosaurs. The external anatomy (i.e., neurocentral sutures are visible in presacral vertebrae) is consistent with histological data, since both indicate some degree of immaturity. Dorsal ribs are best elements to estimate age. The new evidence reinforces the hypothesis that mechanical forces were higher in the anterior edge of cervical hemispinous processes, although, these findings do not support the presence of horn cores or interspinous ligament system in the neck of Brachytrachelopan.