Southeastern Pacific Ocean Research Articles

Deep Eastern Boundary Currents: Realistic Simulations and Vorticity Budgets

AbstractConcentrated poleward flows near the eastern boundaries between 2- and 4-km depth have been observed repeatedly, particularly in the Southern Hemisphere. These deep eastern boundary currents (DEBCs) play an important role in setting the large-scale tracer distribution and have nonnegligible contribution to global transports of mass, heat, and tracers, but their dynamics are not well understood. In this paper, we first demonstrate the significant role of DEBCs in the southeastern Atlantic, Indian, and Pacific Oceans, using the Southern Ocean State Estimate (SOSE) data assimilating product, and using high-resolution regional general circulation model configurations. The vorticity balances of these DEBCs reveal that, over most of the width of such currents, they are in an interior-like vorticity budget, with the meridional advection of planetary vorticity βυ and vortex stretching fwz being the largest two terms, and with contributions of nonlinearity and friction that are of smaller spatial scale. The stretching is shown, using a temperature budget, to be largely forced by resolved or parameterized eddy temperature transport. Strongly decaying signals from the eastern boundary in friction and stretching form the dominant balance in a sublayer close to the eastern boundary. The temporal variability of DEBCs is then examined, to help to interpret observations that tend to be sporadic in both time and space. The probability distribution functions of northward velocity in DEBC regions are broad, implying that flow reversals are common. Although the regions of the simulated DEBCs are generally local minima of eddy kinetic energy, they are still constantly releasing westward-propagating Rossby waves.

Effects of <sup>238</sup>U variability and physical transport on water column <sup>234</sup>Th downward fluxes in the coastal upwelling system off Peru

Abstract. The eastern boundary region of the southeastern Pacific Ocean hosts one of the world's most dynamic and productive upwelling systems with an associated oxygen minimum zone (OMZ). The variability in downward export fluxes in this region, with strongly varying surface productivity, upwelling intensities and water column oxygen content, is however poorly understood. Thorium-234 (234Th) is a powerful tracer to study the dynamics of export fluxes of carbon and other elements, yet intense advection and diffusion in nearshore environments impact the assessment of depth-integrated 234Th fluxes when not properly evaluated. Here we use vessel-mounted acoustic Doppler current profiler (VmADCP) current velocities, satellite wind speed and in situ microstructure measurements to determine the magnitude of advective and diffusive fluxes over the entire 234Th flux budget at 25 stations from 11 to 16∘ S in the Peruvian OMZ. Contrary to findings along the GEOTRACES P16 eastern section, our results showed that weak surface wind speed during our cruises induced low upwelling rates and minimal upwelled 234Th fluxes, whereas vertical diffusive 234Th fluxes were important only at a few shallow shelf stations. Horizontal advective and diffusive 234Th fluxes were negligible because of small alongshore 234Th gradients. Our data indicated a poor correlation between seawater 238U activity and salinity. Assuming a linear relationship between the two would lead to significant underestimations of the total 234Th flux by up to 40 % in our study. Proper evaluation of both physical transport and variability in 238U activity is thus crucial in coastal 234Th flux studies. Finally, we showed large temporal variations on 234Th residence times across the Peruvian upwelling zone and cautioned future carbon export studies to take these temporal variabilities into consideration while evaluating carbon export efficiency.

A new species of Eunice Cuvier, 1817 (Polychaeta: Eunicidae) from the slope of the Desventuradas Islands and seamounts of the Nazca Ridge, southeastern Pacific Ocean.

A new species of Eunicidae, Eunice decolorhami sp. n., from the southeastern Pacific Ocean, is described. The species was collected at the slope of the Desventuradas Islands (San Félix and San Ambrosio) and in three nearby seamounts of the Nazca Ridge, in dead coral rubble bottoms from 180 to 340 m depth and inhabiting inside parchment-like branched tubes. Eunice decolorhami sp. n. can be distinguished from other species of the genus, mainly by the coloration pattern of the subacicular hooded hooks along the body segments, the beginning of the subacicular hooded hooks, the beginning of the branchiae, the maximum number of branchial filaments, and the maxillary formula. A key for the seven Eunice species recorded off the coast of Chile and Peru, including the new species described herein, is provided.

Use of Small Cetaceans as Bait in Small-Scale Fisheries in Peru

The use of small cetaceans as bait is a practice that has been reported worldwide, affecting the conservation status of vulnerable species. In Peru specifically, it has been documented since at least the late 1990s. Here we document the various contemporary uses of small cetaceans, including targeted capture for subsequent use as fishing bait. We designed a survey addressing fishery characteristics, bycatch and the use as bait of small cetaceans, and the history of these practice. We surveyed 147 fishers based in the four Peruvian ports of Paita, Salaverry, Pucusana and Ilo and held in-depth interviews with 12 fishers from Salaverry and Pucusana. Results from our surveys show that the majority of fishers have had small cetacean bycatch while fishing and that bycaught individuals in gillnets are commonly found dead (Salaverry: 100% of fishers, Pucusana: 58%) whereas in longlines small cetaceans are found alive (Paita: 74%, Ilo: 53%). We found that the use of dolphins as bait is still common in both gillnet and longline shark fisheries along the coast of Peru and that it is more frequent in northern ports. Gillnet fishers reported using one to four dolphins as bait per trip (10-15 sets) from bycatch events and discarding the rest if they have excessive bycatch, while longline fishers reported using 10 to 20 dolphins per fishing trip from either direct take by harpooning or the exchange of carcasses from gillnet vessels. Bycatch and use as bait mainly affects four species, the dusky, bottlenose and common dolphins and the Burmeister's porpoise. We identified three drivers of the use of dolphins as bait: effectiveness, availability and cost. These factors will have to be addressed in parallel if this practice is to be reduced. We recommend combining legislative and community-led strategies to reduce bait use and thus further the conservation of small cetacean populations in the southeastern Pacific Ocean.

Spatiotemporal Distribution of Key Pelagic Microbes in a Seasonal Oxygen-Deficient Coastal Upwelling System of the Eastern South Pacific Ocean

The strong seasonal variability in physical-chemical conditions of the Eastern South Pacific Ocean creates an ideal setting to study spatiotemporal distribution of key marine microbial communities.. We herein report a nearly 4-year-long time series of the variability in amoA gene counts of ammonia oxidizing archaea (AOA) and bacteria (betaproteobacteria, bAOB) by quantitative PCR, GI.1a Thaumarchaeota and MG-II Euryarchaeota by CARD-FISH, and the picoplanktonic community by flow cytometry for this area. During spring-summer, non-photosynthetic picoplankton such as MG-II Euryarchaeota and GI.1a Thaumarchaeota peaked at the surface and deeper waters, respectively. General AOA and bAOB achieved higher abundances at the oxycline mainly in summer (up to 105-104 amoA copies mL-1). Generalized additive models for location, scale, and shape (GAMLSS) indicated that season and depth account for 19-46% of variations in the abundance of the groups studied, particularly GI.1a Thaumarchaeota and AOA. The oxygen and nitrite concentration were statistically meaningful predictors for the studied groups. GAMLSS models indicate that ammonia oxidizing assemblage’s variability is coupled with ammonia, nitrite, and nitrate variations. Our results indicate that microbial abundances fluctuation is associated with upwelling variability and oxygen-deficient water conditions that shape the substrates availability and metabolic response of marine microbes, including keystone ammonia oxidizing assemblages and their ecological interactions. Overall, our results support planktonic nitrification activity and its contribution to nitrous oxide excess production in the time series off Concepción and the ecological dynamics regarding AOA -bAOB in coastal waters.

Transient Climate Response to Arctic Sea Ice Loss with Two Ice-Constraining Methods

AbstractThe impact of Arctic sea ice loss on the ocean and atmosphere is investigated focusing on a gradual reduction of Arctic sea ice by 20% of the annual mean, occurring within 30 years, starting from present-day conditions. Two ice-constraining methods are explored to melt Arctic sea ice in a coupled climate model, while keeping present-day conditions for external forcing. The first method uses a reduction of sea ice albedo, which modifies the incoming surface shortwave radiation. The second method uses a reduction of thermal conductivity, which changes the heat conduction flux inside ice. Reduced thermal conductivity inhibits oceanic cooling in winter and sea ice basal growth, reducing the seasonality of sea ice thickness. For similar Arctic sea ice area loss, decreasing the albedo induces larger Arctic warming than reducing the conductivity, especially in spring. Both ice-constraining methods produce similar climate impacts, but with smaller anomalies when reducing the conductivity. In the Arctic, the sea ice loss leads to an increase of the North Atlantic water inflow in the Barents Sea and eastern Arctic, while the salinity decreases and the gyre intensifies in the Beaufort Sea. In the North Atlantic, the subtropical gyre shifts southward and the Atlantic meridional overturning circulation weakens. A dipole of sea level pressure anomalies sets up in winter over northern Siberia and the North Atlantic, which resembles the negative phase of the North Atlantic Oscillation. In the tropics, the Atlantic intertropical convergence zone shifts southward as the South Atlantic Ocean warms. In addition, Walker circulation reorganizes and the southeastern Pacific Ocean cools.

A Technique for Estimating Liquid Droplet Diameter and Liquid Water Content in Stratocumulus Clouds Using Radar and Lidar Measurements

AbstractThis paper describes a technique for estimating the liquid water content (LWC) and a characteristic particle diameter in stratocumulus clouds using radar and lidar observations. The uncertainty in LWC estimate from radar and lidar measurements is significantly reduced once the characteristic particle diameter is known. The technique is independent of the drop size distribution. It is applicable for a broad range of W-band reflectivityZbetween −30 and 0 dBZand all values of lidar backscatterβobservations. No partitioning of cloud or drizzle is required on the basis of an arbitrary threshold ofZas in prior studies. A method for estimating droplet diameter and LWC was derived from the electromagnetic simulations of radar and lidar observations. In situ stratocumulus cloud and drizzle probe spectra were input to the electromagnetic simulation. The retrieved droplet diameter and LWC were validated using in situ measurements from the southeastern Pacific Ocean. The retrieval method was applied to radar and lidar measurements from the northeastern Pacific. Uncertainty in the retrieved droplet diameter and LWC that are due to the measurement errors in radar and lidar backscatter measurements are 7% and 14%, respectively. The retrieved LWC was validated using the concurrent G-band radiometer estimates of the liquid water path.

Observed Triple Mode of Salinity Variability in the Thermocline of Tropical Pacific Ocean

AbstractA well‐defined Triple MOde of Salinity (TMOS) variability in the tropical Pacific thermocline layer (24–25.5 σθ isopycnal surfaces) is revealed from the Argo observations during 2004–2018. Thermocline salinity in the tropical northern and southwestern Pacific Ocean varies out of phase on interannual to near‐decadal time scales with that in the tropical southeastern Pacific Ocean. The TMOS is attributed to anomalous advection of mean salinity as well as advection of anomalous salinity by the mean oceanic current on isopycnal surfaces. While the TMOS pattern is quite different from the thermal patterns associated with the El Niño‐Southern Oscillation (ENSO) or the Pacific Decadal Oscillation (PDO), it is significantly associated with the ENSO and PDO indices with a time lag of 10 months. Isopycnal propagation of salinity anomalies and anomalous freshwater input in the outcropping region, also both associated with ENSO and PDO, are important in the formation of TMOS. The propagation speed of isopycnal salinity anomalies is close to documented phase speeds of baroclinic Rossby waves and velocities of zonal currents. The TMOS acts to shape the basin‐scale Pacific water masses and potentially plays an important role in climate.

Phylogenetic position and morphological descriptions ofChitonspecies from the south-eastern Pacific

AbstractIn the south-eastern Pacific Ocean (SEP), six species of the genus Chiton have been recorded. However, the taxonomic status and geographic distribution of some of these species is controversial. In this study, we compare and describe Chiton species in the SEP. More than 3000 specimens of six species from 49 localities were analysed for morphological features. Among these, 27 specimens of the six species from the SEP were sequenced for the mitochondrial barcode region (COI) and ribosomal 16S and 18S to infer phylogenetic relationships. Phylogenetic reconstruction indicates that the genus Chiton in the SEP represents a polyphyletic group and confirms the placement of C. barnesii in Chiton and not in Radsia, as previously suggested. Among Chiton s.s., C. cumingsii is the sister-species of C. magnificus, while C. granosus is a sister-species of C. barnesii. This analysis also indicates that C. bowenii is a junior synonym of C. magnificus. Our results improved the knowledge of systematics and distribution of Chiton species in the SEP, suggesting the presence of five valid species of the genus. In this study, we designate a lectotype for C. cumingsii and a neotype for C. granosus.

On Some Little-known Melanostomiidae with the Description of a New Species of Eustomias

A new species, Eustomias mikhailini sp. nova, close to E. macrura was described. It is proposed to restore the Urostomias subgenus from the synonymy of the Spilostomias subgenus. An identification key for the subgenera of the genus Eustomias with a high number of rays of the pectoral fin and for the species of the subgenus Urostomias is presented. A specimen of Eustomias gr. melanostigma, which combines the features of different species of this group in its structure of the chin barbel, was described, which raises doubts about the validity of the isolation of E. melanonema and E. melanostigmoides. New occurrences of rare Leptostomias cf. bilobatus and Photonectes xenopogon species, first discovered in the southeastern Pacific Ocean, were reported; detailed morphological descriptions of specimens are given; the limits of variability of diagnostically valuable characters are specified.

Biochemical fingerprints of marine fungi: implications for trophic and biogeochemical studies

Fungi are ubiquitous in the marine environment, but their role in carbon and nitrogen cycling in the ocean, and in particular the quantitative significance of fungal biomass to ocean biogeochemistry, has not yet been assessed. Determination of the biochemical and stable isotope composition of marine fungi can provide a basis for identifying fungal patterns in relation to other microbes and detritus, and thus allow evaluation of their contribution to the transformation of marine organic matter. We characterized the biochemical composition of 13 fungal strains isolated from distinct marine environments in the eastern South Pacific Ocean off Chile. Proteins accounted for 3 to 21% of mycelial dry weight, with notably high levels of the essential amino acids histidine, threonine, valine, lysine and leucine, as well as polyunsaturated fatty acids, ergosterol, and phosphatidylcholine. Elemental composition and energetic content of these marine-derived fungi were within the range reported for bacteria, phytoplankton, zooplankton and other metazoans from aquatic environments, but a distinct pattern of lipids and proteins was identified in marine planktonic fungi. These biochemical signatures, and an elemental composition indicative of a marine planktonic source, have potential applications for the assessment of fungal contribution to marine microbial biomass and organic matter reservoirs, and the cycling of carbon and nutrients.

A new species of Heterocotyle (Monogenea: Monocotylidae), a gill parasite of the diamond stingray Hypanus dipterurus (Myliobatiformes: Dasyatidae) from the Peruvian coastal zone

A new monogenean, Heterocotyle margaritae n. sp. (Monocotylidae: Heterocotylinae), is described based on specimens collected from the gills of the diamond stingray, Hypanus dipterurus (Jordan & Gilbert, 1880) (Myliobatiformes: Dasyatidae) captured off the South Pacific coast, Lima Region, Peru. Monogeneans were fixed in hot 4% formalin, observed and measured as permanent mounts stained with Gomori's trichrome, and mounted in Canada balsam. Drawings were made with the aid of a drawing tube. The new species is distinguished from all congeners mainly by having a funnel-shaped male copulatory organ, spatulate distally with lateral folds and by its club-shaped accessory piece. The most similar congener, H. americana Hargis, 1955, resemble H. margaritae n. sp. regarding the general structure of the male copulatory organ (funnel-shaped with an accessory piece). However, besides other features, the new species differ from H. americana by having an accessory piece without a dorsal button (vs an accessory piece with a dorsal button in H. americana). This is the first report of a member of Heterocotyle Scott, 1904 in the Southeastern Pacific Ocean. The present finding brings to 20 the number of known species of Heterocotyle, and represents the fifth described monogenean species from Hypanus dipterurus.

Environmental Drivers of Seabird At-Sea Distribution in the Eastern South Pacific Ocean: Assemblage Composition Across a Longitudinal Productivity Gradient

Seabird distributions are determined by physical and biological factors operating at variable scales and levels of ecological organization. Accordingly, changes in the composition of the marine avifauna often correspond to large-scale (macro-mega) shifts in water mass properties. Yet, few studies have addressed biogeographical patterns across multiple current systems, spanning from highly-productive to oligotrophic waters. In this study, we characterize the at-sea assemblages of nesting seabirds across the Eastern South Pacific Ocean (ESPO), a vast region spanning from the Humboldt Current to the South Pacific Gyre. Employing multivariate techniques, we first identify four distinct species assemblages and then relate their distributions to the underlying environmental conditions. Our results show that Julian day, depth, sea surface temperature, sea surface salinity, and chlorophyll-α concentration are the most important factors explaining the distribution patterns of these assemblages. Moreover, environmental conditions also explain overall seabird abundance and species richness, two community-level characteristics indicative of ocean productivity. Seabird abundance was best explained by four variables, associated with onshore-offshore gradients (distance to the coast, ocean depth), and the influence of coastal upwelling (mean mixed layer depth, sea surface salinity). Richness was best explained by seasonality (Julian day) and by the presence of water mass boundaries (sea surface temperature coefficient of variation). Our findings underscore the importance of environmental factors structuring the distribution and biogeography of seabirds across gradients of ocean productivity and water mass properties. Understanding the environmental drivers of seabird abundance and richness in the ESPO will inform the prioritization and design of effective marine conservation measures in this poorly studied region.

A new genus and three new species of dactylogyrids (Monogenea), gill parasites of the threadfin bass, Pronotogrammus multifasciatus Gill (Perciformes: Serranidae) in the Southeastern Pacific Ocean off Peru.

Pronotogrammella n. g. is erected to accommodate Pronotogrammella boegeri n. sp. (type-species), Pr. scholzi n. sp. and Pr. multifasciatus n. sp. (Monogenea: Dactylogyridae). The new species are gill parasites of the threadfin bass Pronotogrammus multifasciatus Gill (Perciformes: Serranidae), a demersal teleost collected from off the coastal zone of Puerto Pizarro, Tumbes, Peru. Pronotogrammella n. g. is mainly characterised by having broadly fork-shaped dorsal anchors, which have an accessory anchor sclerite articulated to the tip of the superficial roots. Pronotogrammella n. g. is also characterised by having: (i) a tubular tapered-shaped male copulatory organ (MCO), filamentous distally, with a clockwise coil at distal end or not, lacking accessory piece; (ii) a dorsal bar with an anteromedial delicate umbelliform membrane supported by two processes; (iii) hooks with upright blunt thumb and uniform shank; (iv) a vaginal aperture dextrolateral; (v) a subquadrangular haptor, with inconspicuous lateral flaps and lacking haptoral reservoirs; and (vi) eye-spot or chromatic granules absent. Pronotogrammella boegeri n. sp. is characterised by its crosier-shaped MCO having a clockwise coil at distal end and by its dorsal bar with a straight anteromedial processes. Pronotogrammella scholzi n. sp. is typified by possessing of a dorsal bar with the anteromedial processes like cow horns, hoof-shaped deep roots of the dorsal anchors and a broader shaft of the MCO. Pronotogrammella multifasciatus n. sp. differs from all congeners by having a tubular MCO with twisted shaft and a base with a short and broad arm and by having an almost dumbbell-shaped ventral bar.

Wind and wave height climate from two decades of altimeter records on the Chilean Coast (15°–56.5° S)

In order to look for climatological changes on significant wave height and wind magnitude distributions, two decades of altimeter data were analyzed in a monthly 1° × 1° grid at the Southeastern Pacific Ocean, offshore of Chile. Both wind magnitude and significant wave height shown significant growing medians, at a rate of up to 0.2 m dec−1 and 1 m s−1 dec−1, respectively. Nevertheless, the shape of both statistical distributions shows regional differences from North to South. We conclude that both significant wave height and wind magnitude distributions experienced significant changes during the last two decades and also that their behavior is not uniform along the Southeastern Pacific Ocean.

Calicotyle hydrolagi n. sp. (Monogenea: Monocotylidae) infecting the deep-sea Eastern Pacific black ghost shark Hydrolagus melanophasma from the Atacama Trench, with comments on host specificity of Calicotyle spp.

We describe Calicotyle hydrolagi n. sp. (Monogenea: Monocotylidae) infecting the cloaca of deep-water Eastern Pacific black ghost sharks, Hydrolagus melanophasma captured as bycatch at a local fishery for Patagonian toothfish Dissostichus eleginoides, (Nototheniidae) in the Atacama Trench using morphological and nucleotide (LSU rRNA and SSU rRNA) data. This new species is differentiated from its congeners by a number of characters, including the absence of a cecal diverticula, the size and shape of the male copulatory organ and the shape of the vagina, as well as by differences in molecular data (SSU rRNA and LSU rRNA). The suitability of some sclerotized structures such as the male copulatory organ (MCO) as a taxonomic character is discussed; specifically, we found that the relationship between MCO and total length exhibit different trends in members of Calicotyle isolated from sharks, skates and chimaeras. Additional efforts to obtain sample of Calicotyle species and further molecular studies based on ribosomal and mitochondrial genes are necessary to clarify the degree of host specificity in this genus. Additionally, this is the first report of a member of Calicotyle to be reported in the Southeastern Pacific Ocean.

Biodiversity and biomass of bentho-demersal megafaunal assemblages of the yellow and red squat lobster fishing grounds in Central Chile (Eastern Pacific Ocean)

Biodiversity and biomass patterns of megafaunal assemblages were assessed from the yellow (Cervimunida johni) and red (Pleuroncodes monodon) squat lobster fishing grounds in the Southeastern Pacific Ocean during four years. Bottom trawls were conducted applying the swept-area method in a stratified sampling design, obtaining global and specific catch per unit area (CPUA). We recorded two target and 47 by-catch species, with a total CPUA of 80.000 t/km2 (cumulative from 2005 to 2008) Fishes and crustaceans dominated over other taxonomic groups. Classes Actinopterygii and Malacostraca attained the highest specific richness; the presence of a few dominant and many rare species in terms of CPUA and frequency, was characteristic of the studied assemblages, hence, the general CPUA pattern parallels that of the most abundant species in the bathymetric and latitudinal gradients. The three most conspicuous non-target species, Heterocarpus reedi, Merluccius gayi gayi and Hippoglossina macrops accounted for 91% of the by-catch CPUA, whereas Class Malacostraca also represented 91% of the total CPUA. The highest average specific richness occurred at intermediate depths (300–400 m) and the lowest in shallow waters (50–100m); the highest overall CPUA occurred at 100–200m and the lowest at both 400–600m and 50–100m. Depth was the most significant factor in the variability of our assemblages. However, particular features of the Humboldt Current System might act as drivers of important effects across the latitudinal gradient on the high productivity and dynamism of the squat lobster fishery, despite the homogeneous composition of the community. This study shows the importance of considering the whole biodiversity within appropriate management actions, in order to achieve ecological benefits (e.g. resilience, functional diversity, water quality, primary productivity) in communities subjected to fishing pressure.

Trophic ecology and ontogenetic shift in the diet of the sicklefin smoothhound (Mustelus lunulatus) in the southeastern Pacific Ocean

Trophic ecology and ontogenetic shift in the diet of the sicklefin smoothhound (Mustelus lunulatus) in the southeastern Pacific Ocean

Vapor transport of silver and gold in basaltic lava flows

Abstract We documented occurrences of native copper (Cu), silver (Ag), and gold (Au) in a pāhoehoe flow from Kīlauea volcano (Hawaii, USA), an a‘ā flow from Mauna Loa volcano (Hawaii), and a mid-oceanic-ridge basalt (MORB) from the Chile Ridge (southeastern Pacific Ocean). Native Ag in Kīlauea and MORB samples consistently contained minor Cl (<1 wt%). Native Ag in Hawaiian basalts can occur at the center of nearly circular patches of relatively evolved minerals, which presumably formed after late-stage silicate liquid infilled pipe vesicles. Sulfur loss and oxidation of a Cu-sulfide phase can explain the native Cu, but not Au and Ag deposition. The rare occurrence of native Cu-Au-Ag alloys and the large native Au and Ag grain size suggest separate metal precipitation mechanisms. A fractional crystallization and degassing model envisions initial Au and Ag enrichment in crystallizing interstitial liquid and further enrichment in a separating vapor phase. From the flow interior, the metals ascend through ephemeral pipe vesicles as bisulfide (Au) or chloride (Ag) vapor complexes and precipitate in the transition zone below the upper vesicular zone, owing to temperature and oxidation state changes. Our results support igneous vapor transport of ore elements in mafic plutonic systems and imply preconcentration of gold during lava solidification before later hydrothermal remobilization.

New Neogene taxa of the tribe Chlamydini Teppner, 1922 (Pectinidae, Bivalvia) of southern South America

AbstractThe Chilean species traditionally assigned to the genera Chlamys Röding, 1798 or Zygochlamys Ihering, 1907 are now placed in two new endemic South American taxa: Dietotenhosen n. gen. (middle Miocene–early middle Pliocene), to include the southeastern Pacific Ocean species D. hupeanus (Philippi, 1887) n. comb. and D. remondi (Philippi, 1887) n. comb., and Ckaraosippur n. gen. (earliest middle Miocene–Pliocene), for C. calderensis (Möricke, 1896) n. comb. (Chile) and C. camachoi n. sp. (Argentina). Both genera are the youngest survivors of the tribe Chlamydini in southern South America. None of them is related to the circumpolar genus Psychrochlamys Jonkers, 2003, and the previous proposal of the dispersal through the Antarctic Circumpolar Current for the species included herein in Dietotenhosen is rejected.UUID: http://zoobank.org/61b4bb50-321f-4b78-9069-609178ef0817