Sand Dollar Research Articles

Shared regulatory function of non-genomic thyroid hormone signaling in echinoderm skeletogenesis

Thyroid hormones are crucial regulators of metamorphosis and development in bilaterians, particularly in chordate deuterostomes. Recent evidence suggests a role for thyroid hormone signaling, principally via 3,5,3′,5′-Tetraiodo-L-thyronine (T4), in the regulation of metamorphosis, programmed cell death and skeletogenesis in echinoids (sea urchins and sand dollars) and sea stars. Here, we test whether TH signaling in skeletogenesis is a shared trait of Echinozoa (Echinoida and Holothouroida) and Asterozoa (Ophiourida and Asteroida). We demonstrate dramatic acceleration of skeletogenesis after TH treatment in three classes of echinoderms: sea urchins, sea stars, and brittle stars (echinoids, asteroids, and ophiuroids). Fluorescently labeled thyroid hormone analogues reveal thyroid hormone binding to cells proximal to regions of skeletogenesis in the gut and juvenile rudiment. We also identify, for the first time, a potential source of thyroxine during gastrulation in sea urchin embryos. Thyroxine-positive cells are present in tip of the archenteron. In addition, we detect thyroid hormone binding to the cell membrane and nucleus during metamorphic development in echinoderms. Immunohistochemistry of phosphorylated MAPK in the presence and absence of TH-binding inhibitors suggests that THs may act via phosphorylation of MAPK (ERK1/2) to accelerate initiation of skeletogenesis in the three echinoderm groups. Together, these results indicate that TH regulation of mesenchyme cell activity via integrin-mediated MAPK signaling may be a conserved mechanism for the regulation of skeletogenesis in echinoderm development. In addition, TH action via a nuclear thyroid hormone receptor may regulate metamorphic development. Our findings shed light on potentially ancient pathways of thyroid hormone activity in echinoids, ophiuroids, and asteroids, or on a signaling system that has been repeatedly co-opted to coordinate metamorphic development in bilaterians.

CENTRAL BANK DIGITAL CURRENCY: LESSONS LEARNT FROM THE SAND DOLLAR

This research examines the implemention of the Sand Dollar in the Bahamas and draws several suggestions for policy makers when considering this new type of money in order to achieve the objectives. Besides, this study also provides basic insight into the background of development and motivations for this currency around the world. The study points out that the authorities need to promote more educational programs to introduce and bring more knowledge of the benefits of this currency and re-consider the non-interest bearing feature as it might be less appealing for holders.

Selective concentration of iron, titanium, and zirconium substrate minerals within Gregory's diverticulum, an organ unique to derived sand dollars (Echinoidea: Scutelliformes).

Gregory's diverticulum, a digestive tract structure unique to a derived group of sand dollars (Echinoidea: Scutelliformes), is filled with sand grains obtained from the substrate the animals inhabit. The simple methods of shining a bright light through a specimen or testing response to a magnet can reveal the presence of a mineral-filled diverticulum. Heavy minerals with a specific gravity of >2.9 g/cm3 are selectively concentrated inside the organ, usually at concentrations one order of magnitude, or more, greater than found in the substrate. Analyses of diverticulum content for thirteen species from nine genera, using optical mineralogy, powder X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy, as well as micro-computed tomography shows the preference for selection of five major heavy minerals: magnetite (Fe3O4), hematite (Fe2O3), ilmenite (FeTiO3), rutile (TiO2), and zircon (ZrSiO4). Minor amounts of heavy or marginally heavy amphibole, pyroxene and garnet mineral grains may also be incorporated. In general, the animals exhibit a preference for mineral grains with a specific gravity of >4.0 g/cm3, although the choice is opportunistic and the actual mix of mineral species depends on the mineral composition of the substrate. The animals also select for grain size, with mineral grains generally in the range of 50 to 150 μm, and do not appear to alter this preference during ontogeny. A comparison of analytical methods demonstrates that X-ray attenuation measured using micro-computed tomography is a reliable non-destructive method for heavy mineral quantification when supported by associated analyses of mineral grains extracted destructively from specimens or from substrate collected together with the specimens. Commonalities in the electro-chemical surface properties of the ingested minerals suggest that such characteristics play an important role in the selection process.

Central Bank Digital Currency Adoption Challenges, Solutions, and a Sentiment Analysis

Abstract We identify some factors limiting CBDC adoption and some of the possible solutions. We also assess the media sentiment about central bank digital currencies in general as well as about locally issued CBDCs. We find that there is a high correlation between the negative media sentiment about CBDCs in general and locally issued CBDCs. We also find that the negative media sentiment about the eNaira, DCash and Sand Dollar was caused by the existing negative media sentiment about CBDCs in general. However, a positive media sentiment about the eNaira, DCash and Sand Dollar was not caused by the existing positive media sentiment about CBDC in general.

Determinants of global interest in central bank digital currency: The role of sustainable development and cryptocurrency

PurposeThis paper aims to investigate the determinants of global interest in central bank digital currency (CBDC). It assessed whether global interest in sustainable development and cryptocurrency are determinants of global interest in CBDC.Design/methodology/approachGoogle Trends data were analyzed using two-stage least square regression estimation.FindingsThere is a significant positive relationship between global interest in sustainable development and global interest in CBDC. There is a significant positive relationship between global interest in cryptocurrency and global interest in the Nigeria eNaira CBDC. There is a significant negative relationship between global interest in CBDC and global interest in the eNaira CBDC. There is a significant positive relationship between global interest in CBDC and global interest in the China eCNY. There is a significant negative relationship between global interest in cryptocurrency and global interest in the Sand Dollar and DCash.Originality/valueThe literature has not empirically examined whether global interest in sustainable development and cryptocurrency are factors motivating global interest in CBDC. This study fills a gap in the literature by investigating whether global interest in sustainable development and cryptocurrency are factors motivating global interest in CBDC.

Short Communication: The biodiversity of aquatic organisms in Anak Laut Lake, Aceh Singkil District, Indonesia

Abstract. Muhtadi A, Leidonald R, Yolanda O, Harahap R, Matondang NP, Putri K, Simamora LFM, Sitompul G. 2023. Short Communication: The biodiversity of aquatic organisms in Anak Laut Lake, Aceh Singkil District, Indonesia. Biodiversitas 24: 4837-4844. Anak Laut Lake is a unique and strategic coastal lake, significantly recognized for its diverse marine biota and the potential to be a spawning, nursery, and feeding ground. Therefore, this research aimed to determine the types of aquatic organisms, including plankton, fish, crustaceans, benthos, seagrasses, and mangroves in Anak Laut Lake. The experiment was conducted in October 2022 in the Anak Laut Lake ecosystem, North Singkil Sub-district, Aceh Singkil District, Aceh Province, Indonesia. The plankton was taken using a plankton net tool, extracted vertically from a depth of 2 m, and pulled to the surface. Fish and crustaceans were observed and caught with purse seines, ring nets, and gill nets. Benthic organisms were directly observed on the edge of the lake, along with the identification of mangroves, while at the bottom, the fishermen dove into the water. The data obtained were analyzed descriptively and compared with similar research. The results showed a rich biodiversity in Anak Laut Lake, with at least 165 species/genera of aquatic biota, 9 species of mangroves, and 2 Seagrass species. The marine nekton found consisted of fish (55 species), shrimp (3 species), and crabs (10 species). The macrozoobenthos found in Anak Laut Lake consisted of 13 species of clams, 12 gastropods, 3 sea cucumbers, 2 sand dollars, 2 horseshoe crabs, and 1 sea urchin. Various species of aquatic biota whose existence was threatened in nature and found in this lake included golden sea cucumber (Stichopus herrmanni), seahorse (Hippocampus comes and Hippocampus kuda) with Vulnerable status (VU), tap ray (Maculabatis gerrardi), and sand cucumber (Holothuria scabra) with Endangered species status (EN). This shows that this coastal lake is an important and crucial habitat for several species that are vulnerable to extinction. For this reason, in the future, further studies are needed regarding the habitat characteristics and spatial and temporal distribution of aquatic organisms in Lake Laut, so that more appropriate management can be implemented for the sustainability of the lake.

Phylogeny, ancestral ranges and reclassification of sand dollars

Classification of the Class Echinoidea is under significant revision in light of emerging molecular phylogenetic evidence. In particular, the sister-group relationships within the superorder Luminacea (Echinoidea: Irregularia) have been considerably updated. However, the placement of many families remains largely unresolved due to a series of incongruent evidence obtained from morphological, paleontological, and genetic data for the majority of extant representatives. In this study, we investigated the phylogenetic relationships of 25 taxa, belonging to eleven luminacean families. We proposed three new superfamilies: Astriclypeoidea, Mellitoidea, and Taiwanasteroidea (including Dendrasteridae, Taiwanasteridae, Scutellidae, and Echinarachniidae), instead of the currently recognized superfamily Scutelloidea Gray, 1825. In light of the new data obtained from ten additional species, the historical biogeography reconstructed shows that the tropical western Pacific and eastern Indian Oceans are the cradle for early sand dollar diversification. Hothouse conditions during the late Cretaceous and early Paleogene were coupled with diversification events of major clades of sand dollars. We also demonstrate that Taiwan fauna can play a key role in terms of understanding the major Cenozoic migration and dispersal events in the evolutionary history of Luminacea.

Predators Induce Phenotypic Plasticity in Echinoderms across Life History Stages.

AbstractMarine invertebrates with biphasic life cycles feature life history transitions that coincide with habitat changes from benthic adults to planktonic embryos and larvae, then a return to the benthos as a juvenile at metamorphosis. The metamorphic transition exposes animals to a new suite of benthic predators, and high mortality often occurs in the hours and days following settlement. Juvenile invertebrates may produce phenotypically plastic morphological defenses when predator cues are detected. However, time lags inherent to phenotypic plasticity may delay the production of defenses until after the period of highest vulnerability. It should, therefore, be beneficial for planktonic larvae approaching settlement to detect waterborne cues from benthic predators and produce juvenile phenotypes appropriate for postmetamorphic survival. Echinoderms are useful models for testing transhabitat and trans-life history stage phenotypic plasticity because many species have larvae that construct their juvenile phenotype while still in the water column. In this study, we tested whether planktonic echinoderm larvae exposed to cues from benthic predators modified their juvenile phenotypes at settlement. Green urchin (Strongylocentrotus droebachiensis) and Pacific sand dollar (Dendraster excentricus) larvae were exposed to predatory green crab (Carcinus maenus) or red rock crab (Cancer productus) cues, respectively, from their early-stage juvenile rudiment formation through settlement. Green urchin larvae exposed to predator cues settled with significantly more juvenile spines compared to unexposed controls. Sand dollars exhibited earlier settlement, larger disk area, fewer spines, and shorter spines when exposed to benthic predator cues. Sand dollar larvae were also exposed to cues from planktonic crab larvae and in response settled sooner and larger, with even fewer and shorter spines than those exposed to benthic predator cues. These results suggest that echinoderm larvae alter their juvenile phenotype in response to predator cues, but the response varies between species, and responses to planktonic threats may be prioritized over benthic ones.

Biomass of Ophiuroidea и Echinarachnius parma on a plot of the West Kamchatka shelf in 2013–2017

According to the results of bottom grab surveys carried out in 2013–2016, data on the biomass (g/m2) of the dominant sea urchin species Echinarachnius parma and the complex of brittle stars on a plot of the West Kamchatka shelf are given. The average biomass of Echinarachnius parma for the surveyed plot varied over the years and in 2013 was 45.298 ± 25.582 g/m2, in 2014 – 48.784 ± 26.561 g/m2, in 2015 – 19.557 ± 11.678 g/m2, in 2016 – 18.957 ± 13.192 g/m2. In terms of biomass on the surveyed plot (g/m2) the main role among the echinoderms belongs to fl at sand dollars, and in terms of population density (ind./m2) – to brittle stars. 11 species of brittle stars from 4 families were noted. In terms of population density the most common species among the brittle stars are Amphiodia craterodmeta and Ophiura quadrispina.

Distribution and Diversity of Sediment-Dwelling Echinoids of the Central Florida Keys

Sediment-dwelling echinoids, such as clypeasteroids (sand dollars and sea biscuits) and spatangoids (heart urchins), are important ecosystem engineers found in many soft-bottom habitats around the Florida Keys. Several studies, conducted over the last five decades, have documented their spatial distribution and diversity in various areas of the Florida Keys. This study focuses on the central part of the Florida Keys, an area that has been subject to diverse human impacts including tourism, fishing, boating, and diving leading to pollution, eutrophication, and intrusion of non-native species. All these stressors can potentially undermine the ecosystem’s composition and health, including sediment-dwelling echinoids. To assess the current state of echinoid populations, 27 sites located along the central part of the Florida Keys have been surveyed by SCUBA (2020-2021) for presence of live specimens and dead skeletal remains of clypeasteroid and spatangoid echinoids. A total of 17 out of 27 sites were inhabited by sediment-dwelling echinoids of the species Clypeaster rosaceus, Clypeaster subdepressus, Encope michelini, Leodia sexiesperforata, Meoma ventricosa, and Plagiobrissus grandis. Up to five species co-occurred at single sites, although most sites harbored only one or two species, and at all sites a single species was dominant in terms of relative abundance. The most widespread and abundant species in the surveyed area were Clypeaster rosaceus, Leodia sexiesperforata, and Meoma ventricosa. A comparison of live specimens with skeletal echinoid remains indicates that dead tests are typically much rarer than live specimens. However, the spatial distribution and abundance of dead remains tracks live occurrences: when dead remains are found, live specimens are always observed. The comparison of the new survey reported here with past studies and database records suggests that the faunal composition of sediment-dwelling echinoid assemblages has not changed notably over the past 50 years.

Abundance and active patch selection modulate reproductive connectivity and fitness of pea crabs living on sand dollars

Connectivity is paramount for population stability, but the mechanisms underlying the distribution of populated patches and how they affect reproductive connectivity and individual fitness remain elusive. Here, we mapped the distribution of sand dollars Encope emarginata as habitat patches for obligate-commensal pea crabs Dissodactylus crinitichelis, at several sites in Brazil. At occupied patches, we assessed whole-crab population structure and the fitness of ovigerous females. By doing so, we obtained population snapshots under varying environmental conditions that portrayed the natural variation of connectivity and fitness in the region. While sand dollar supply did not limit the size of crab populations, overall crab abundance limited reproductive connectivity and the potential for offspring production. However, except for cases where connectivity was extremely low and high, active crab aggregations enhanced reproductive potential despite the overall random distribution of sand dollars. Crab interactions within hosts, likely controlled by larger females, added to reproductive connectivity by increasing the frequency of mating pairs. Differently from the population-level case, effects of crab abundance on individual fitness were dual and only detectable when abundance was lowest (positive) or highest (negative), so that fitness remained high at intermediate crab abundance, decreasing when it became either too low (e.g. Allee effects) or too high (e.g. energetic costs of intraspecific competition).

The effects of temperature and pH on the reproductive ecology of sand dollars and sea urchins: Impacts on sperm swimming and fertilization.

In an era of climate change, impacts on the marine environment include warming and ocean acidification. These effects can be amplified in shallow coastal regions where conditions often fluctuate widely. This type of environmental variation is potentially important for many nearshore species that are broadcast spawners, releasing eggs and sperm into the water column for fertilization. We conducted two experiments to investigate: 1) the impact of water temperature on sperm swimming characteristics and fertilization rate in sand dollars (Dendraster excentricus; temperatures 8-38°C) and sea urchins (Mesocentrotus franciscanus; temperatures 8-28°C) and; 2) the combined effects of multiple stressors (water temperature and pH) on these traits in sand dollars. We quantify thermal performance curves showing that sand dollar fertilization rates, sperm swimming velocities, and sperm motility display remarkably wide thermal breadths relative to red urchins, perhaps reflecting the wider range of water temperatures experienced by sand dollars at our field sites. For sand dollars, both temperature (8, 16, 24°C) and pH (7.1, 7.5, 7.9) affected fertilization but only temperature influenced sperm swimming velocity and motility. Although sperm velocities and fertilization were positively correlated, our fertilization kinetics model dramatically overestimated measured rates and this discrepancy was most pronounced under extreme temperature and pH conditions. Our results suggest that environmental stressors like temperature and pH likely impair aspects of the reproductive process beyond simple sperm swimming behavior.

Retail Central Bank Digital Currencies (CBDC), Disintermediation and Financial Privacy: The Case of the Bahamian Sand Dollar

The fast-growing, market-driven demand for cryptocurrencies worries central banks, as their monetary policy could be completely undermined. Central bank digital currencies (CBDCs) could offer a solution, yet our understanding of their design and consequences is in its infancy. This non-technical paper examines how The Bahamas has designed the Sand Dollar, the first real-world instance of a retail CBDC. It contrasts the Sand Dollar with definition-based specifications. The author then develops a scenario analysis to illustrate commercial bank risks. In this process, the central bank becomes a deposit monopolist, leading to high funding risks, disintermediation risks, and solvency risks for the commercial banking sector. This paper argues that restrictions and caps will be the new specifications of a regulatory framework for CBDCs if disintermediation in the banking sector is to be prevented. The anonymity of CBDCs is identified as a comparative disadvantage that will affect their adoption. These findings provide insight into governance problems facing central banks and coherently lead to the design of the Sand Dollar. This paper concludes by suggesting that combating cryptocurrencies is a task that cannot be solved by a CBDC.

Phylogenomic analyses of echinoid diversification prompt a re-evaluation of their fossil record

Echinoids are key components of modern marine ecosystems. Despite a remarkable fossil record, the emergence of their crown group is documented by few specimens of unclear affinities, rendering their early history uncertain. The origin of sand dollars, one of its most distinctive clades, is also unclear due to an unstable phylogenetic context. We employ 18 novel genomes and transcriptomes to build a phylogenomic dataset with a near-complete sampling of major lineages. With it, we revise the phylogeny and divergence times of echinoids, and place their history within the broader context of echinoderm evolution. We also introduce the concept of a chronospace - a multidimensional representation of node ages - and use it to explore methodological decisions involved in time calibrating phylogenies. We find the choice of clock model to have the strongest impact on divergence times, while the use of site-heterogeneous models and alternative node prior distributions show minimal effects. The choice of loci has an intermediate impact, affecting mostly deep Paleozoic nodes, for which clock-like genes recover dates more congruent with fossil evidence. Our results reveal that crown group echinoids originated in the Permian and diversified rapidly in the Triassic, despite the relative lack of fossil evidence for this early diversification. We also clarify the relationships between sand dollars and their close relatives and confidently date their origins to the Cretaceous, implying ghost ranges spanning approximately 50 million years, a remarkable discrepancy with their rich fossil record.

Exposure of adult sand dollars (Scaphechinus mirabilis) (Agassiz, 1864) to copper oxide nanoparticles induces gamete DNA damage.

The increase in the number of products containing nanoparticles (NPs) poses a real threat to the environment. Recently, more evidence has been added to predictive models about the presence of NPs in various natural and anthropogenic systems. The acute toxicity of most aquatic NPs has now been well documented. However, data such as the ecotoxicological significance of the long-lasting effects of NPs on the reproductive system and gamete quality of aquatic organisms are still relatively scarce. Therefore, a 10-day experiment was carried out on the sand dollar Scaphechinus mirabilis (Agassiz, 1864) exposed to low (20 and 40μg/L) concentrations of copper oxide nanoparticles (CuO NPs). An accumulation of copper in tissues and a significant increase in lipid peroxidation product concentrations after exposure to NP were observed. A significant decrease in the fertilization rate was shown at 40μg/L. No significant changes in embryonic or larval development were found. However, comet analysis results showed a significant increase in DNA damage in spermatozoa exposed to CuO NPs, which may further manifest as negative effects at later developmental stages or in subsequent generations.

Issues of integrating central bank digital currency into the fiat money system

Since 2020, a digital equivalent of legal tender became one of the most discussed topics among the international community of central banks. Moreover, the Bahamas’ “Sand Dollar” – the world's first actually operating platform has been launched. With the onset of the pandemic, the acceleration of events is influenced by a non-economic factor – the demand for all methods of remote socio-economic interaction. In 2021, based on previous public consultations, the Bank of Russia published the Digital Ruble Concept. The article discusses the background, goals and side effects of creating central bank digital money. The idea of digital transformation of banknotes meets the public demand for a payment instrument that is practical in modern realities, but its implementation is associated with uncertain consequences for the banking sector and the future development of technologies and security standards for settlements using digital solutions. In this context, the rationale for placing on a reimbursable basis the services of private financial agents on the digital money platform is given.

The Motives for Issuing Central Bank Digital Currency and the Challenges of Introduction Thereof

The idea of a central bank digital currency arose ten years ago for the first time, but by now it has become one of the most frequently discussed topics in the field of finances. Currently, some 100 central banks are researching and investigating the concept of a central bank digital currency (CBDC) and its implementation options.1 Over half of these central banks have reached the development stage, and some are already conducting on-site experiments. However, the intense interest and the efforts made have not yet led to an increasing number of implementations, since so far only the Bahamas (Sand Dollar), the Member Countries of the Eastern Caribbean Currency Union (DCash) and Nigeria (eNaira) have introduced a CBDC. The other countries are currently still in one of the preparatory stages. The article briefly reviews the history of money digitalisation, and describes the various motives for issuing a CBDC, as well as the variety of challenges faced in the process of introducing a CBDC. It also presents the preparations taken so far for the introduction of the digital Euro, as well as Sweden’s e-krona. Finally, it summarises the authors’ views on the strategy Hungary should follow regarding a CBDC.

Neuroecology beyond the brain: learning in Echinodermata.

We propose an expansion of neuroecological comparisons to include the capabilities of brainless and non-neural organisms. We begin this enterprise by conducting a systematic search for studies on learning in echinoderms. Echinodermata are marine invertebrates comprising starfish, brittle stars, sea cucumbers, sea urchins, and sea lilies. Animals in this phylum lack any centralized brain and instead possess diffuse neural networks known as nerve nets. The learning abilities of these animals are of particular interest as, within the bilaterian clade, they are close evolutionary neighbors to chordates, a phylum whose members exhibit complex feats in learning and contain highly specialized brains. The learning capacities and limitations of echinoderms can inform the evolution of nervous systems and learning in Bilateria. We find evidence of both non-associative and associative learning (in the form of classical conditioning) in echinoderms, which was primarily focused on starfish. Additional evidence of learning is documented in brittle stars, sand dollars, and sea urchins. We then discuss the evolutionary significance of learning capabilities without a brain, the presence of embodied cognition across multiple groups, and compare the learning present in echinoderms with the impressive cognitive abilities documented in the oldest linage group within vertebrates (the major group within the phylum of chordates), fish.

Blockchain Implementation Method for Interoperability between CBDCs

Central Bank Digital Currency (CBDC) is a digital currency issued by a central bank. Motivated by the financial crisis and prospect of a cashless society, countries are researching CBDC. Recently, global consideration has been given to paying basic income to avoid consumer sentiment shrinkage and recession due to epidemics. CBDC is coming into the spotlight as the way to manage the public finance policy of nations comprehensively. CBDC is studied by many countries. The bank of the Bahamas released Sand Dollar. Each country’s central bank should consider the situation in which CBDCs are exchanged. The transaction of the CDDB is open data. Transaction registers CBDC exchange information of the central bank in the blockchain. Open data on currency exchange between countries will provide information on the flow of money between countries. This paper proposes a blockchain system and management method based on the ISO/IEC 11179 metadata registry for exchange between CBDCs that records transactions between registered CBDCs. Each country’s CBDC will have a different implementation and time of publication. We implement the blockchain system and experiment with the operation method, measuring the block generation time of blockchains using the proposed method.

Diversity and biostratigraphy of the late Oligocene-late Miocene sand dollars (Echinoidea: Scutelliformes) of Argentina and Uruguay

Introduction: Scutelliforms were diverse and widespread in shallow marine environments during Neogene times in South America. Nevertheless, they have almost never been used as biostratigraphic tools. Objective: To provide a refined stratigraphic frame useful for calibrating temporal dimensions of scutelliform diversity from Argentina and Uruguay and its correlation with the molluscan assemblages previously proposed. Methods: A detailed survey of their geographic and stratigraphic provenance was carried out. We revised both the bibliography and collections (institutional and from our own field work). Results: The group is represented by 14 species belonging to six genera, and four assemblages were identified. Numerical dates of the Neogene marine rocks obtained recently allowed their placement in a chronological scheme: “Iheringiella” sp. A is restricted to the late Oligocene, the genera Camachoaster and “Eoscutella” and the species Monophoraster telfordi to the early Miocene, Abertella gualichensis and Abertella miskellyi to the middle Miocene, and Monophoraster duboisi, Amplaster coloniensis and Amplaster ellipticus to the late Miocene. Non-lunulate scutelliforms are not restricted to the late Oligocene as previously supposed. The oldest occurrence of the genus Monophoraster corresponds to the early Miocene, and along with Iheringiella are long-living taxa that embrace the 25.3 Ma-18.1 Ma (Iheringiella patagonensis) and approximately 15 Ma-6.48 Ma (Monophoraster darwini) intervals. The presence of Iheringiella in the early Miocene of northeastern Patagonia is corroborated, reaching there its northernmost distribution. Monophoraster darwini has a temporal range from the late Miocene (where it was previously thought to be restricted) back to the middle Miocene, since this is the species yielded in the well-known and discussed “Monophoraster and Venericor Beds”. Conclusions: The Paleogene-Neogene scutelliforms of Argentina and Uruguay range from the late Oligocene to the late Miocene. There is a good correspondence among the numerical ages, molluscan biozones and scutelliform assemblages.