The Macaronesian archipelagos host exceptionally well-preserved coastal sedimentary deposits formed during the warmest period of the Last Interglacial episode, the Marine Isotope Substage 5e (MIS 5e). Numerous MIS 5e fossiliferous outcrops occur, scattered across several islands of the Canary Archipelago. Among these is San Juanito, a small outcrop located in the eastern sector of Punta del Hidalgo (northeast Tenerife Island), where MIS 5e sediments are distributed over an area of approximately 480 m2. A multidisciplinary study was conducted, aiming to: (i) determine the age of the fossiliferous sediments; (ii) define the stratigraphic relationships between the sedimentary deposit and the underlying/overlying volcanic sequences; (iii) assess the taxonomic richness and the functional palaeobiodiversity of this palaeosite; and (iv) provide a comprehensive palaeoecological reconstruction of the MIS 5e environment. Based on two key ecostratigraphic indicator species for the Canarian MIS 5e, the San Juanito sequence is here assigned to the Last Interglacial. Qualitative sampling yielded forty mollusc taxa, including three gastropods that represent new records—Alvania johannae Moolenbeek & Hoenselaar, 1998, Krachia tiara (Monterosato, 1874), and Barleeia unifasciata (Montagu, 1803)—bringing the current MIS 5e checklist for the Canary Islands to 202 gastropods and 80 bivalves. The highly cemented matrix of the San Juanito deposits prevented the collection of standardized 1 kg bulk sediment samples. Nevertheless, we strongly recommend adopting this quantitative approach in future studies of suitable MIS 5e outcrops across the archipelago. The faunal assemblage indicates that the San Juanito region was dominated by rocky shores during the MIS 5e, much like today. This paleoenvironmental reconstruction is based on the high frequency of species associated with hard substrates—including echinoids, vermetids, fissurellids, and patellids—and the overwhelming dominance (95%) of epifaunal gastropods.

Linkages between modern environments that host a panoply of complex ecosystems and their ancient counterparts preserved in the rock record are indispensable to our understanding and appreciation of the world we occupy [...]

Rhodoliths (from Greek etymology meaning red + stone) are spheroidal accretions composed of various types of crustose coralline red algae that dwell in relatively shallow waters where sunlight allows for photosynthesis. Unlike most other kinds of algae that are attached to the seabed by a holdfast, rhodoliths are free to roll about by circumrotary movements stimulated mainly by gentle wave action and bottom currents, as well as by disruptions by associated fauna. Frequent movement exposes every part of the algal surface to an equitable amount of sunlight, which generally results in an evenly concentric pattern of growth over time. Individual structures may attain a diameter of 10 to 20 cm, representing 100 years of growth or more. Initiation typically involves encrustation by founder cells on a rock pebble or shell fragment. In life, the functional outer surface is red or pink in complexion, whereas the structure’s inner core amounts to dead weight. Chemically, rhodoliths are composed of high magnesium calcite [(Ca,Mg)CO3], with examples known around many oceanic islands and virtually all continental shelves in the present world. The oldest fossil rhodoliths appeared during the early Cretaceous, 113 million years ago. Geologically, rhodoliths may occur in massive limestone beds composed of densely packed accumulations. Living rhodoliths commonly occur in waters as shallow as −2 to −10 m, as well as seaward in mesophotic waters up to −100 m under exceptional conditions of water clarity. Especially in shallower waters, rhodoliths are vulnerable to transfer by storm waves to supratidal settings, which result in bleaching under direct sunlight and death. Increasingly, marine biologists recognize that rhodolith beds represent a habitat that offers shelter to a community of other algae and diverse marine invertebrates.

Johnson, M.E.; Martín-González, E.; Uchman, A.; Baarli, B.G.; Madeira, P.; Ávila, G.C., and Ávila, S.P., 2026. Overlapping modern rocky shore and Pleistocene Beach with seismic fractures at El Médano (Tenerife Island, Canary Archipelago, NE Atlantic Ocean). Journal of Coastal Research, 42(5), 797–809. Charlotte (North Carolina), ISSN 0749-0208. The eastern shore of Tenerife in the Canaries Archipelago is affected by wave swell generated by persistent NE trade winds and episodic storms over the NE Atlantic Ocean. Several aspects of coastal geomorphology are well preserved in a protected area designated as the Montaña Roja Special Nature Reserve covering 166 ha near the village of El Médano. The reserve is dominated by a volcanic cinder cone that rises 171 m above sea level undergirded by basaltic sea cliffs. A surface covering approximately 20,000 m2 features Pleistocene strata deposited as a pocket beach between the sea cliffs. A 3.8-m measured section includes a succession starting from beach facies, including the upper foreshore, through berm and back-shore to dune deposits. Dune facies climb an additional 75 m against the steep face of the Montaña Roja cinder cone. Seismic fractures parallel to shore incise sedimentary facies at regular intervals more than 20 m inland. An elongated, 10-cm wide fracture exposed in the tidal zone is filled with cemented basalt pebbles and cobbles. A slip-face with slickensides appears on the face of a rock pedestal in the tidal zone. Potholes eroded in beach strata are typically 25 to 35 cm in diameter and include cemented and loose basalt cobbles submerged during high tide. Unusual features along the modern shore include a basalt boulder beach that undercuts the seaward edge of Pleistocene beach strata. A dozen narrow surge channels partially filled with loose cobbles and gravel penetrate as much as 2 m across the strata. Pebbles shot by storm waves into channels are ejected to collect in loose aggregates on the indurated Pleistocene surface as much as 3 m beyond the landward termination of those passages. Angular pyroclasts are embedded in dune rocks at the base of Montaña Roja, derived from above as minor rock falls.

Over geological time, glacial-interglacial cycles affected the geographical range of marine species. Typically, this has been documented by tracking the long-distance dispersal of tropical, shallow-water mollusc species in archipelagos during the last phase of glacial terminations or the early phase of an interglacial episode. Many studies conducted in the Macaronesian archipelagos (i.e., the Azores, Madeira, Selvagens, Canaries and Cabo Verde) support this view. To date, however, such studies exclude data from full glacial periods, owing to difficulties in accessing the geological record of lower sea-level glacial episodes. Here we demonstrate, for the first time, the range expansion into the tropics of cold-water/temperate species during two glacial episodes (MIS 4 and MIS 6), using the Macaronesian region as a case study. For that, we innovate by using megatsunami deposits to unveil biogeographic processes and patterns noticed in the conglomerates of Tarrafal (Santiago Island, Cabo Verde) and of Teno Bajo (Tenerife, Canary Islands), which are interpreted to have been emplaced by megatsunamis triggered by volcanic flank collapses occurred at ~68 ka (MIS 4) and ~170 ka (MIS 6), respectively. Our results detect that not only latitudinal, long-distance dispersal of marine molluscs occurred toward the tropics (mainly between archipelagos, and between European and African shores towards the Macaronesian archipelagos), but also longitudinal range expansion. Moreover, both MIS 4 and MIS 6 megatsunami deposits yielded a high biodiversity (expressed both by species richness and diversity indices) when compared with raised beach sediments. This new finding must be added to the distinctive sedimentological and textural characteristics of tsunami deposits. Finally, we demonstrate that four mollusc species reported from the Teno glacial MIS 6 tsunami deposits, and several temperate and sub-tropical bivalve and gastropod species reported from the Tarrafal glacial MIS 4 tsunami deposits spread to the Canaries and Cabo Verde, respectively, establishing viable populations in those archipelagos. Thus, these species provide evidence of geographical range expansion of marine species from mid-latitudes to low latitudes by means of long-distance, equatorward dispersal of benthic, shallow-, cold-water/temperate marine molluscs between archipelagos and from continental shores to oceanic islands during glacial periods. Megatsunami deposits are used to unveil biogeographic patterns and processes in the Macaronesian archipelagos. Megatsunami deposits record the geographical range expansion of cold-water/temperate species towards the tropics during glacial times. Our data demonstrates both latitudinal and longitudinal range shifts of marine molluscs, by means of long-distance dispersal. Both MIS 4 and MIS 6 megatsunami deposits analysed yielded a high biodiversity when compared with MIS 5e raised beach sediments. A high biodiversity (expressed both by species richness and diversity indices) is a new finding to characterize the distinctive sedimentological and textural characteristics of tsunami deposits.

Fan-delta systems are geomorphological structures and sedimentary records seldom preserved on oceanic volcanic islands. The generally coarse-grained deposits belonging to the Las Palmas Detritic Formation (Mio-Pliocene) at the Las Rehoyas section, NE part of Gran Canaria Island (Canary Islands, Spain), contain abundant but relatively small rhodoliths, non-nucleated, in partly bioturbated (Skolithos ichnofacies) sand-dominated strata. This section consists of four sedimentary units deposited in a fan-delta system that developed on a marine platform in the northeastern part of the island. The system was flooded during the late Miocene to early Pliocene, a non-eruptive phase on Gran Canaria Island. Stabilization of the fan delta due to a relative rise in sea level enabled colonization by burrowing organisms and the development of rhodoliths, which were redeposited by storms from the lower shoreface-offshore to the foreshore-middle shoreface environment.

This study extends the Sea-Level Sensitive dynamic model of marine island biogeography by integrating the dynamics of fusion-fission islands during glacial-interglacial cycles with marine island biogeography theory. We discuss the variations in littoral area dueto Pleistocene sea-level changes and their effect on the evolutionary rates of splitting, extinction, and merging of populations, as well as on the speciation rates of marine shallow-water organisms. Here, we introduce three different types of fusion-fission islands: Solum islands, i.e., islands that have never been merged with neighbouring islands (at depths shallower than 50 m) during sea-level low stands associated with glacial episodes; Soror islands, i.e., islands that are subjected to fusion-fission cycles due to sea-level changes and thus may be functionally connected or separated depending on the amplitude of sea level changes; and Moliones islands, where two or more islands are functionally connected from a marine point of view, as the seafloor depth separating them is always shallower than 50 m, regardless of sea level. For this study, we selected 324 islands located in temperate and tropical climates, and representative of a broad geographic distribution, which were classified accordingly: 50 Solum islands, 77 islands making up 20 groups of Soror islands, and 197 islands from 34 groups of Moliones islands. Sea-level variation during glacial-interglacial cycles induced changes in the insular littoral area (ILA), resulting in five general types of curves of ILA change herein described. These ILA curves depend on the depth distribution across the shelves, which, in turn, depends on several variables, including the age of the island, the tectonic setting, the presence of submarine and subaerial terraces, and also on the presence/absence of coral reefs. Finally, we provide several predictions on the frequencies of marine population splitting, extinction, and merging events, as well as on the speciation rates of shallow-water marine organisms, according to the respective island types.

Taxonomic impediment and taxonomic gap are two major problems that challenge the advancement of bi ological and palaeontological sciences such as (palaeo)ecology and (palaeo)biogeography. In an effort to overcome these difficulties, the Last Interglacial fossiliferous deposits from the Island of Santa Maria (Azores Archipelago, Portugal) have been intensively studied during the last two decades. The epitoniid gastropod Epitonium jani Segers, Swinnen and De Prins, 2009 is an example, herein, of a new addition to the fossil re cord worldwide. This finding increases the number of fossil molluscs reported from the warmest period of the Last Interglacial deposits of the Azores (Marine Isotopic Substage 5e; MIS 5e) to 138 taxa (114 Gastropoda and 24 Bivalvia). As in other insular settings, the Phylum Mollusca is the best represented marine group in the Pliocene and Pleistocene (MIS 5e) fossiliferous outcrops and an update on the palaeobiodiversity of the Azores Archipelago is provided, herein.

During the last two decades, the Macaronesian archipelagos have been the focus of multiple studies targeting the abundant and diversified fossil record from late Neogene and Quaternary deposits. This record of past biota, ecosystems and climates is crucial for understanding the impact of glacial–interglacial cycles on Atlantic littoral marine organisms. Coupled with ongoing studies on the factors responsible for global climate change and associated sea-level variations, they contributed decisively towards the development of the modern marine island biogeography theory. Our current knowledge of the evolutionary and biogeographic history of the past and extant, shallow-water marine organisms from the Macaronesian geographic region relies on detailed analysis of many individual fossiliferous outcrops by means of quantitative and qualitative methodologies. Here, we focus on the fossil record of a newly studied MIS 5e outcrop at Pedra-que-pica (PQP), on Santa Maria Island (Azores Archipelago, Portugal). This multidisciplinary work integrates geology, paleontology and biology, providing the first detailed description of the sedimentary facies and stratigraphic framework of the PQP MIS 5e sequence that, coupled with the documentation of the biodiversity and ecological composition of PQP molluscan assemblages, allows us to produce a paleoecological reconstruction and to compare PQP with other last interglacial outcrops from Santa Maria Island. Our results increase the number of the Azorean MIS 5e marine molluscs to 140 taxa (116 Gastropoda and 24 Bivalvia). Ervilia castanea (Montagu, 1803) is the most abundant bivalve, while Bittium nanum (Mayer, 1864) and Melarhaphe neritoides (Linnaeus, 1758) are the most abundant gastropod species. In addition, this work emphasizes the crucial importance of complementing quantitative collecting with qualitative surveys of the fossiliferous outcrops, because nearly 42% of the bivalve species and 28% of the gastropod taxa would be missed if only quantitative samples were used. Derivation of Hill numbers and rarefaction curves both indicate that the sampling effort should be increased at PQP. Thus, although Santa Maria Island is recognized by the scientific community as one of the best-studied islands regarding the last interglacial fossil record, this study emphasizes the need to continue with similar efforts in less known outcrops on the island.

Compared to the extensive research carried out on the Neogene deposits of the Lower Chelif Basin, the Pleistocene series is still poorly studied, with no detailed lithological succession published to date. This study focuses on the Glycymeris-rich Unit (GRU) along the coastal area of the Hachacha Plateau in Northwestern Algeria. This unit unconformably overlies Miocene, Pliocene, and Pleistocene basements. The latter was identified for the first time in this work using a biostratigraphic approach based on calcareous nannofossils and planktonic foraminifera. The GRU is interpreted as a tsunami-related deposit, formed in a coastal environment (foreshore/backshore) during the upper Pleistocene, corresponding to the Last Interglacial period, i.e., Marine Isotopic Substage 5e (MIS 5e). This interpretation provides a first multidisciplinary description of a tsunami deposit in Algeria that is supported by distinctive biotic, taphonomic, and sedimentological features. The deposits contain a mixture of marine organisms from different ecological zones (supralittoral to shallow circalittoral biocenoses), including molluscan assemblages such as the so-called Senegalese fauna (bivalves and gastropods), sponges, serpulids, coralline algae and corals. Occasionally, rare terrestrial snails are also found mixed with the marine fauna. Taphonomic analysis reveals low percentages of boring, absence of encrustation, and excellent shell preservation, suggesting that powerful waves eroded sediment masses and transported them inland from deeper areas beneath the taphonomic active zone. The predominance of sharp-edged fragmented shells, chaotic arrangements with oblique to vertical shell orientations and the good shell sorting, indicates transport by mass flows and rapid deposition during an extreme event-a tsunami-, distinguishing these deposits from those associated with gradual and oscillatory flows, such as storm events. Sedimentological characteristics, including irregular erosive base, lateral facies variations, wide grain size ranges (clay to boulders), normal and inverse grading, and diagnostic structures (both fragile and hard-rock rip-up clasts, high-energy flow features such as horizontal and oblique laminations, and hummocky cross-stratification, injection of sediment into the substrate, imbrication of large angular boulders and soft sediment deformation structures), combined with the active tectonic context of Northwestern Algeria support the interpretation as a seismically triggered tsunami and enhances the under-standing of this type of deposits in similar coastal settings.

A former sea stack formed by basalt occurs at Ponta Manuel Lopes on the north coast of Sal Island in the Cabo Verde Archipelago. Reduced by wave erosion prior to coastal uplift, the dimensions may be partially reconstructed as a rectangular-shaped block 45 m long, by 20 m wide and 7 m high. The long axis sits parallel to a Mid-Pleistocene terrace elevated as much as 15 m above present sea level. Contrasting facies are preserved on two flanks. The smaller western face is joined laterally by a massive limestone deposit dominated by the coral Siderastrea radians with hundreds of dome-shaped to pillar-shaped colonies preserved largely in growth position. Other corals within the same fringing facies include Porites porites, Madracis cf. pharensis, and Favia cf. gravida. The carbonate matrix in the coral beds also includes abundant sea urchin spines. A separate lithofacies that extends across the inner, long axis of the block consists of calcarenites and calcirudite with angular basalt fragments that decrease in size and abundance from the wall. These deposits dip 35º to the south to merge with the adjacent Pleistocene terrace. The eastern half of the basalt block was truncated by marine erosion, which allows access to steeply dipping beds banked against the former surface. That deposit includes rare oyster debris. Other mollusks are common in flat-lying limestone on the adjacent marine terrace. Although fossil corals are abundant throughout the Cabo Verde, Canary and Madeira archipelagos, in situ fossil coral-reef structures are uncommon and the island shelves around those groups historically lack the protection of fringing or barrier reefs.

Organo-sedimentary deposits that result from fine-grained sediment trapping, binding, and likely precipitation (of carbonate) by microbes in flat-mat, branching, and dome-shaped constructions are termed microbialites. They were first identified as stromatolites by paleontologists well before the discovery of cyanobacteria that build the same kinds of structures in contemporary settings around the world. Earth’s earliest life forms were prokaryotes (bacteria and bacteria-like forms) that reproduced under anaerobic conditions and later produced increasingly aerobic conditions. Stromatolites persisted through later Archean and Proterozoic times through the subsequent Phanerozoic to the present. At the start of the Cambrian Period 538 million years ago, stromatolites continued alongside rapidly diversifying plant and animal phyla during the Cambrian explosion of eukaryotic life, which have complex cells with internal structures and tissue-grade organization in multicellular taxa. The type locality exhibiting clear examples of stromatolite structures is conserved at Lester Park near Saratoga Springs in northeastern New York State. Paleontologist James Hall (1811–1898) was the first in 1884 to assign a Latin binomen (Cryptozoon proliferum) to stromatolite fossils from Lester Park. Thereafter, reports on formally named stromatolites proliferated, as did examples from virtually all subsequent geological time intervals including the Pleistocene Epoch. However, recognition that living cyanobacteria formed stromatolites identified as Cryptozoon took place much later in 1961 with the announcement by geologist Brian W. Logan (1933–2008) who described modern constructions in Hamlin Pool, Shark Bay, Western Australia. Initially, Shark Bay was regarded as a one-of-a-kind sanctuary for stromatolites living under restricted conditions with elevated levels of salinity that prohibited competition or grazing by eukaryotes. Most notably, among other settings with living stromatolites discovered and described since then are the Bahamas, East African rift lakes, Mexico’s Baja California, and saline lakes in Argentina. This report reviews the history of discoveries of modern-day stromatolites, more commonly called microbialites by biologists. All are predicated on the ground-breaking efforts of geologists and paleontologists who first described fossil stromatolites but were unaware of their living counterparts. The Lester Park locality is highlighted together with a master list of other North American localities that feature purported Cryptozoons.

The last phase of the end-Ordovician extinction event involved substantial sea-level changes. The Oslo/Asker District in Norway is a rare place where the deeper-water early Hirnantian fauna is succeeded by the equivalent deeper-water Edgewood-Cathay Fauna. Both faunas are highly diverse, with the same small-shelled brachiopods, Onniella, Leangella, and Eoplectodonta, dominating. They also share a large number of long-ranging and eurytopic genera. Taxa from contemporary shallower-water environments are rare. Near a third of the brachiopod genera in the Norwegian deeper-water early Hirnantian Fauna went extinct, including seven genera that survived into the Ordovician/Silurian boundary strata. Deeper-water early Hirnatian and Edgewood-Cathay collections are not well-known worldwide. Global quantitative samples from low latitudes, including the Norwegian samples, were compared against each other using NMDS (Non-metric Multidimensional Scaling) with the Bray-Curtis index. Qualitative samples used NMDS with the Raup-Crick index and Network Analysis. The Raup-Crick index sharply differentiated the early Hirnantian and Edgewood-Cathay faunas, possibly due to sensitivity to extinction and origination data. In contrast, the paleogeographic affinity between collections of the two faunas is pronounced using the Bray-Curtis index. Network Analysis also demonstrates regionality; the Edgewood-Cathay Fauna is especially heterogeneous. This contrasts with the shallower-water Hirnantia Fauna, which is more cosmopolitan. Quiet waters below the storm-wave base possibly hindered the spread of larvae, and anoxic plumes of water may have caused further barriers to the lateral spreading of the Edgewood-Cathay Fauna. As in Norway, long-ranging, eurytopic taxa were shared between the two faunas with few typical shallow-water taxa.

The boundary between land and sea is among the most extensive and extreme ecological barriers on planet Earth. Intertidal organisms living at this junction are subject to potentially lethal conditions related to desiccation, temperature fluctuations, and wave shock. Although difficult to quantify at a global level, rocky coasts account for between a third and three-quarters of all shorelines today. Resistant to coastal erosion, rocky coasts also exhibit adaptations by marine invertebrates and marine algae within intertidal zones that are geographically widespread. Biotic composition is variable depending on the tidal range at any given place and on climatic differences between tropical and more temperate latitudes. Contemporary granite shores having low recession rates with well-established biotic zones are reviewed in three regions: Mount Desert Island in Maine, USA (44° N latitude), Mahé and Praslin islands in Seychelles (4°30′ S Latitude), and Lizard Island off the coast of Queensland, Australia (14°40′ S Latitude). The zonal composition and overall biotic diversity at these locations are compared, as well as the fossilization potential of key biota. Over the Phanerozoic time period during the last 538 million years, the ratio between land and ocean varied as a function of plate tectonics depending on the maximum dispersal or coalescence of continents and on relative changes in global sea level. Fossil biotas from a dozen paleoislands with dominant rocky shores that range from 485 million to 125,000 years in age are reviewed to show diversification through time, taking into account episodic mass extinctions. Relationships between storm tracks and volcanic eruptions that factor into physical disruptions are also considered as means of rapid burial and preservation. Themes related to rocky-shore ecology and paleoecology benefit from the cross-fertilization of ideas by marine biologists and marine paleontologists. It is hoped this review may attract a cohort of new students to these allied fields of study, especially in Asia, Africa, and South America.

In order to understand the complex evolutionary processes and patterns that explain current island biodiversity, large datasets and long-term analysis are required. The Last Interglacial (LIG) was one of the warmest interglacials during the last million years. How species mobility changed during this period in the Macaronesia geographical region has long intrigued scientists. It is well established that the northward range expansion of tropical species occurred in the Macaronesian geographical region, but as a marine biogeographic unit, the term "Macaronesia" has not gained a consensus among the scientific community. For the first time, a thoroughly revised and updated checklist is presented for shallow-water marine molluscs from the Atlantic and Mediterranean during the LIG. Based on these wide ranging data, the status of Macaronesia as a marine biogeographic unit during the LIG was examined and our scientific understanding of how this unit evolved is improved. The analysis shows that during the LIG, the molluscan faunas of the Canary and Cabo Verde archipelagos were part of the same tropical Late Pleistocene Mediterranean West-African Province, whereas those in the Azores, Madeira and Selvagens archipelagos would be included in the subtropical Late Pleistocene French-Iberian Province. This contrasts with the present-day scenario, where the subtropical/warm temperate Azores and "Webbnesia" marine ecoregions (Lusitanian province) are biogeographically distinct from the Cabo Verde biogeographic subprovince, which in turn belongs to the West African Tropical biogeographic province. A further analysis of the coherence of "Macaronesia" as a marine biogeographical unit was accomplished by coupling Pliocene, LIG, and present-day data, showing that the term "Macaronesia", and for the marine realm, should only be used in a geographical connotation.

This project follows a tradition of survey work undertaken to appraise physical and biological damage in the aftermath of hurricane-strength winds and waves at a given locality where conditions were well documented prior to the arrival of a particular storm. The locality is the 12 m limestone terrace at Arroyo Blanco on the eastern shores of Isla del Carmen in Baja California Sur, Mexico. A study undertaken in February 2018 established that the surface of the terrace is covered by a coastal boulder deposit that features large slabs of limestone pealed from the outer edge by strong surf attributed to storms of hurricane intensity but unknown date. The largest slabs tend to be rectilinear in shape vulnerable to dislodgement along horizonal bedding planes and weaknesses in vertical joints. These blocks are sufficiently large and weigh enough that movement by humans without necessary mechanical equipment would be impossible. Hurricane Kay, rated as a Category 2 storm, struck the island on 8 September 2022 and an effort was made to visit the area for reconnaissance and detailed survey work soon afterwards. Although a Category 2 storm lacked the energy to remobilize the largest limestone slabs on the terrace, it was found that the storm was sufficient to disturb the adjacent seabed and redeposit as many as 44 sea fans onto the terrace by overwash; the sea fans belonged to the species Pacifigorgia adamsi. Moreover, a species of land plant common to the limestone terrace is the Gulf Star Violet (Stenotis mucronate); it suffered significant desiccation and death due to saltwater exposure. The occurrence of large potholes on the limestone terrace represents a style of physical erosion previously undocumented at the locality and rarely seen elsewhere on rocky shores.

A population of large-shell brachiopods belonging to Stricklandia lens lens from the lower Silurian Solvik Formation is exposed in a capstone layer covering approximately 300 m 2 on steeply dipping strata along the shores of Engervannet at Sandvika in the Oslo Region of southern Norway.Based on sample counts, a density estimated at 250 to 350 articulated shells per square meter resulted from crowding during growth.Given that the former sea bed on which the brachiopods settled can be traced over a lateral distance of 60 m with an average width of 5 m, it is calculated that a monospecific population exceeding 90,000 brachiopods matured from a single, extensive spat fall.Related large-shell brachiopods from the lower Silurian of North America, including Virgiana decussata, Pentamerus oblongus, P. palaformis, and Pentameroides subrectus are commonly preserved in growth position, but observed pavements rarely exceed more than 0.25 m 2 in size.Articulated shells within those populations are almost always truncated midway above the beak and hinge area due to post-mortem erosion by submarine scour.In contrast, the horizon with Stricklandia shells from Sandvika is enormous in scope and features many whole individuals pushed into a more recumbent position in the same direction by a marine current.Re-orientation of the steeply inclined limestone layer to a horizontal position suggests that such a current flowed from the present-day southwest to the northeast as it swept over the Silurian sea bed.

Rhodoliths occur extensively around the shores of Fuerteventura Island in the Canary Archipelago, with Lithothamnion cf. corallioides being the most prominent species. A large number of rhodoliths end up washed onshore, the debris from which contributes to the formation of sediments constituting modern beaches. In a previous study by one of the co-authors (MEJ), the northern coast of Fuerteventura was shown to comprise various types of rhodolith deposits such as beach, platform overwash, tidal pools, coastal dunes, and others. An extraordinary example of stranded rhodoliths is located near Caleta del Bajo de Mejillones, approximately 3 km west of Corralejo, on the north coast of the island. The deposit forms a supratidal beach 120 m long and 10 m wide that sits above the landward termination of an extensive wave-cut platform eroded in basalt and exposed at low tide to a width of 130 m perpendicular to shore. Here, rhodoliths are very small (<3 cm) resembling popcorn, and the locality is known as the "Popcorn Beach". Other examples are berms up to 150 m long and 9 m wide at Caleta del Bajo de Mejillones, or an exposed beach at Playa del Hierro with an area of more than 1500 m(2) covered entirely of very coarse rhodolith sand. Extensive living rhodolith beds were found at a water depth of 22 m.