The site first came to scientific attention in January 2004, when a palaeontologist from the local municipality reported bones weathering out of the ground near the fishing village of Cauca, about 14.6 kilometres northwest of the town of Urumaco. Systematic work had to wait until 2021, when researchers secured permits and launched three excavation seasons across five work areas. The fossiliferous zone covers roughly 1,600 square metres, with eight distinct groupings of bones identified on the surface. Because the bone-bearing layer is only about 40 centimetres thick, excavations were shallow but productive, recovering 41 cranial and postcranial elements now housed in the palaeontological collection of the Urumaco municipality.

The geology of the site tells a story of environmental change. Today the region is semi-arid, buffeted by trade winds and receiving as little as 200 millimetres of rain per year. Yet the oxidation patterns and fine silt-clayey sands that hold the fossils suggest Cauca was deposited in a low-energy, more humid environment, possibly a swampy patch or intermittent body of water. During the Late Pleistocene, the coastal plains of Falcón suffered a negative water balance, and nearby sites such as Muaco and Taima-Taima are interpreted as resurgent springs that formed oases attracting animals during dry spells. Cauca may have offered a similar lifeline, explaining why so many different species died and were buried in one small area.

The star of the assemblage is a giant megatheriine ground sloth assigned to cf. Eremotherium laurillardi, a species that ranged from the southeastern United States to Brazil and could weigh several tonnes. Excavation Cauca B yielded fourteen disarticulated elements, including a partial skull 580 millimetres long, a right hemi-mandible with all four molariform teeth, a complete right radius of 700 millimetres, a clavicle, vertebrae, a metatarsal and part of a pelvis. The researchers believe these bones belong to a single adult individual. A key measurement supported the identification: the ratio of mandible depth below the third tooth to the length of the tooth row came out at 0.77, squarely within the 0.73 to 0.83 range characteristic of Eremotherium.

Other South American natives round out the megaherbivore roster. A thick, short right radius recovered in the same excavation differs markedly from the sloth’s slender radius and is attributed to an indeterminate mylodontid, another family of ground sloths. Two eroded shell osteoderms represent glyptodonts, the tank-like armoured relatives of armadillos, probably related to the genus Glyptotherium, which is well known from other Falcón sites. These finds extend the known geographic distribution of several taxa and reinforce the picture of Falcón as a Pleistocene hotspot where xenarthrans thrived from sea level to mountain areas above 1,200 metres.

The Nearctic contingent of the fauna is equally significant. A mandible with well-preserved molars, a tusk measuring about 1.7 metres long and scattered dental fragments document the gomphothere Notiomastodon platensis, the elephant-like proboscidean that was South America’s last native megaherbivore of this lineage. Wear patterns on the molars and the robust, uncurved, enamel-free tusk distinguish it from the only other South American gomphothere genus, Cuvieronius. An unworn upper second molar found a few metres from one excavation hints at the presence of a juvenile animal. Extinct horses add to the picture: a nearly complete lower third molar shows the occlusal features of Equus, though the researchers conservatively label it Equus sp. because the taxonomy of South American fossil horses remains contested.

Perhaps the most unexpected specimen is a small right ankle bone, an astragalus just over 23 millimetres long, identified as Felidae cf. Leopardus pardalis, the ocelot or cunaguaro. Fossil records of medium-sized cats in the northern neotropics are exceedingly scarce, and this is the first report of the species from northwestern Venezuela. The researchers compared the astragalus with modern specimens of ocelots and bobcats, noting that the bone’s proportions align more closely with Leopardus pardalis than with Lynx rufus, which has never been recorded in South America. An earlier claim of a Pleistocene bobcat-like cat at the nearby Muaco site was never illustrated and cannot be confirmed, making the Cauca astragalus a rare and valuable data point for understanding felid biogeography.

Dating the site required careful laboratory work. Because no bone collagen survived, the team isolated tooth enamel from a gomphothere mandible and a horse tooth, grinding the samples to fine powder and pre-treating them with acetic acid to remove contaminating diagenetic carbonates. Accelerator mass spectrometry produced ages of 33,750 plus or minus 350 years for the gomphothere and 37,050 plus or minus 500 years for the horse, which calibrate to roughly 37,500 to 39,500 and 41,300 to 42,300 calendar years before present respectively. These are among the oldest dates ever produced on bioapatite and sit near the practical limit of radiocarbon dating. Because enamel can exchange carbon with soil carbonates and appear artificially young, the researchers emphasise that the true age of the deposit is likely greater than 40,000 years.

Lithic artefacts found near the excavations add an archaeological dimension, though with important caveats. A chopper, a planoconvex scraper and flakes were recovered on the surface adjacent to the dig areas, and between 100 and 150 metres northeast of the site, prospecting has revealed El Jobo, Clovis and Fish Tail projectile points, technologies associated with the region’s early hunter-gatherers. However, none of these artefacts was found in direct stratigraphic association with the fossils, and decades of laminar erosion have stripped away the upper layers, possibly mixing materials of different ages. The team therefore treats any link between humans and the Cauca megafauna as speculative, in contrast to nearby sites such as Taima-Taima and El Vano, where stone points have been found genuinely associated with butchered gomphothere and sloth remains.

Taphonomic analysis explains both what was found and what was lost. Surface bones had reached the most advanced stage of weathering, fragile and crumbling, while excavated specimens preserved in the second layer retained enough integrity for recovery and plaster-jacketing. The spatial arrangement of the sloth remains, scattered across three excavation areas over roughly a dozen metres, breaks with the anatomical pattern expected in high-energy transport, suggesting the carcass disarticulated in place under low-energy conditions. The scarcity of large, dense limb bones such as humeri and femurs may reflect decades of destruction before the site was documented. Despite these limitations, Cauca joins a growing network of Venezuelan Pleistocene localities along the Coro coastal plain, interpreted as a natural corridor that channelled faunal and human movements during the Great American Biotic Interchange, and it underscores how much of the continent’s Late Pleistocene story, from giant sloths to elusive ocelots, still lies waiting in thin layers of tropical sand.

Subject of Research: Late Pleistocene megafaunal and felid fossils from the new Cauca site in northwest Venezuela

Article Title: Cauca: megafaunal and felid fossils ( Mammalia ) from a Pleistocene site in northwest Venezuela

Article References: Carrillo-Briceño, J. D., Ruiz-Ramoni, D., Sánchez, R., Jaimes, A., Chávez-Aponte, E., Prevosti, F. J., Segura, V., Carlini, A. A., Garbé, L., Tombret, O., Zazzo, A., & Sánchez-Villagra, M. R. (2024). Cauca: megafaunal and felid fossils (Mammalia) from a Pleistocene site in northwest Venezuela. Fossil Record, 27(1), 187-207. https://doi.org/10.3897/fr.27.119967

Image Credits: AI Generated

DOI: 10.3897/fr.27.119967

Keywords: Pleistocene, megafauna, Venezuela, Falcón State, Eremotherium, Notiomastodon, Equus, Leopardus pardalis, glyptodont, radiocarbon dating, paleontology, Gulf of Venezuela

The Yumidong Cave sits at about 1100 meters above sea level in the Miaoyu Basin at the northern foot of the Wushan Mountains, roughly four kilometers from the famous Longgupo Cave, a site central to Quaternary paleontology in China. The cave is a horizontal karst feature developed in limestone, and its stratigraphic sections interbed sandy clay with limestone breccia, recording alternating warm and cool phases that researchers have correlated with marine isotope stages from MIS 8 down to MIS 1. Dating results and faunal comparisons place the fossil-bearing layers in the Mid-Late Pleistocene. Flying squirrels rank among the most abundant groups in the mammalian fauna collected there, giving paleontologists excellent material for detailed morphological comparison of a group that has often suffered from misidentification in earlier studies.

The largest and most abundant species in the assemblage is Pteromys volans, the Siberian flying squirrel, a Palaearctic cold-adapted glider that today ranges from northeast Europe to the Korean Peninsula and Hokkaido. Specimens are plentiful in the cave, making up 9 percent of small mammalian fossils in layer ②-2 and a striking 46 percent in layer ④. The mandibles are very short, with length close to height, and carry a particularly marked angular process wider than the ascending ramus. The cheek teeth are brachyodont, with P3 small but bearing differentiated cusps, P4 fully molarised, and M3 lacking a metaloph and metaconule. On lower teeth, the mesoconid and entoconid are permanent, the trigonid basin remains open, and m3 is conspicuously elongated. These features distinguish the Yumidong material from other small Pleistocene flying squirrels of south China, such as Hylopetes electilis with its pitted cheek tooth enamel, and from the Early Pleistocene Pteromys huananensis known only from Longgupo Cave.

Trogopterus xanthipes, the complex-toothed flying squirrel endemic to China, is the second species identified. It still survives in the region today, living from temperate subalpine coniferous forest to subtropical broad-leaved forest at altitudes of 1360 to 2750 meters. The Yumidong mandibles are high and strong, with a deep pterygoid muscle fossa and a vascular notch that is extensive. The upper cheek teeth carry a well-developed mesostyle connecting paracone and metacone, an enlarged metaconule, and numerous cristae dividing the anterior and posterior valleys into several enamel loops. Lower molars develop metalophids and folds in the talonid basin, making the occlusal surface more complex than that of p4. The genus is diagnosed by this complex dentition and by size: Trogopterus is significantly larger than its closest relative Belomys, with almost no overlap in cheek tooth measurements.

Belomys pearsonii, the hairy-footed flying squirrel, is the third species. It is widely distributed today in south China, northeastern South Asia and Southeast Asia, but has completely disappeared from the Wushan area, although subfossils were reported from the Neolithic Dahekou site in Chongqing. The mandible and teeth closely resemble Trogopterus xanthipes, but the species is much smaller and more lower-crowned. Several dental differences separate the two: P3 of Belomys sits closer to the protocone of P4; the protocone of P4-M2 is more developed while the hypocone is weaker; and the hypocone and metaloph of M3 are absent, whereas in Trogopterus the hypocone is permanent and connects with the metaconule by a straight metaloph. Within the genus, the Early Pleistocene Belomys parapearsoni is smaller with a lower crown, and the Thai Late Pleistocene Belomys thamkaewi falls within the size range of Chinese fossil B. pearsonii, so the Yumidong material is confidently assigned to B. pearsonii.

The fourth species, Aeretes melanopterus, is the largest flying squirrel in the assemblage and one of the rarest mammals in China today, confined to the northeastern Qinghai-Tibet Plateau, the Hengduan Mountains, the Qinling Mountains and a small population near Beijing. It inhabits coniferous and broad-leaved mixed forest at 2500 to 3000 meters and nests on high trees. The Yumidong mandible is robust with a short diastemal portion, and the cheek teeth are subhypsodont with slightly rugose enamel, the lingual wall of upper teeth higher than the buccal wall. P4 is molariformed and triangular in outline, with a small protocone separated from the developed hypocone by a vertical anterolingual flexus extending to the crown base. The genus differs from Petaurista, whose M1/2 lacks a hypocone, and the Yumidong specimens fall within the size and morphological variation of the living species, though they are smaller than Pleistocene specimens from the Tianyuan Cave in Beijing.

Reading these four species together as environmental indicators produces a clear paleoecological signal. All four can adapt to coniferous and broad-leaved mixed forest and alpine coniferous forest, but Pteromys volans and Aeretes melanopterus are cold-adapted Palaearctic species that have completely vanished from the study area and its vicinity. Both were excavated mainly from layer ②-2 and layer ④, the cool phases correlated with MIS 2 and MIS 4, and neither appears in layers ③ and ⑤, the warm phases of MIS 3 and MIS 5. The conclusion is that during MIS 2 and MIS 4 the area around Yumidong Cave was dominated by subalpine evergreen coniferous forest or coniferous and broad-leaved mixed forest, colder and richer in conifers than today, resembling the vegetation now found on Wushan peaks above 2000 meters. During MIS 3 and MIS 5 the landscape was similar to the present subtropical environment.

The regional extinction of the cold-adapted species follows a pattern the authors trace through the glacial-interglacial cycle. Cold-adapted flying squirrels spread southwards during glacial periods and disappeared from the area during interglacials. They likely occupied the middle zone of the Wushan Mountains during the latest Pleistocene or the Last Glacial Maximum, but when the Holocene Megathermal arrived, their habitats contracted to higher peaks. Those limited ecological spaces could not sustain viable populations, and the squirrels died out regionally. Nearby caves reinforce the picture of vertical zonation controlling faunal divergence: Baotansi Cave at about 820 meters shares the same species combination, while Migong Cave at only 160 to 200 meters records a cool but sparser forest with no flying squirrel fossils at all, showing that altitude differences within the same period produced different habitats across the Three Gorges area.

The study also corrects earlier records that seemed to show cold-adapted flying squirrels surviving into the Holocene. Re-examination of material from the Dahekou Neolithic site in Fuling District shows that specimens originally identified as Trogopterus xanthipes should be Belomys pearsonii, that the records of Petaurista petaurista and Aeretes melanopterus appear to be an undetermined Petaurista species, and that the material called Hylopetes alboniger actually belongs to the subfamily Sciurinae and resembles Tamiops swinhoei. Current evidence therefore cannot demonstrate that Pteromys volans, Trogopterus xanthipes or Aeretes melanopterus persisted from the Last Glacial through the Holocene in the Three Gorges area, sharpening the extinction timeline for the cold-adapted fauna.

With four species of four genera identified from abundant maxillae, mandibles and isolated teeth, Yumidong Cave now stands as one of the richest flying squirrel localities of the Chinese Quaternary, and the detailed morphological descriptions set a new standard for a group long neglected in Pleistocene faunal lists. The assemblage demonstrates how a single cave sequence can track the interplay between climate oscillation, vertical mountain zonation and regional extinction. As ice ages deepened, coniferous forest climbed down the slopes and cold-adapted gliders followed; as warmth returned, the forest retreated upward and the squirrels with it, until the Holocene Megathermal pushed their refugia beyond the limits of survival. The fossil teeth of Yumidong thus preserve not just species but the rhythm of forests rising and falling across the mountains of the Three Gorges.

Subject of Research: Pleistocene flying squirrel fossils from Yumidong Cave, China

Article Title: Fossil flying squirrels ( Petauristinae , Sciuridae , Rodentia ) from the Yumidong Cave in Wushan County, Chongqing, China

Article References: Pang, L.-B., Chen, S.-K., Hu, X., Wu, Y., & Wei, G.-B. (2024). Fossil flying squirrels (Petauristinae, Sciuridae, Rodentia) from the Yumidong Cave in Wushan County, Chongqing, China. Fossil Record, 27(1), 209-219. https://doi.org/10.3897/fr.27.115693

Image Credits: AI Generated

DOI: 10.3897/fr.27.115693

Keywords: flying squirrels, Yumidong Cave, Pleistocene, paleoenvironment, China, Fossil Record, extinction, Petauristinae, Fossil, flying, squirrels, Sciuridae

The genus Erebia, whose members are among the most intensively studied alpine insects in the Holarctic, most likely originated in Asia and colonised Europe roughly 17 to 23 million years ago. It diversified into dozens of species during the Miocene and Pliocene, and then underwent a rapid burst of intraspecific differentiation driven by the Pleistocene glacial cycles. The large ringlet is one of the most variable species in the genus, with sixteen morphological subspecies described, five of which are endemic to the Alps. Their territories are separated by intergradation zones so narrow that gene flow between neighbouring forms is evidently extremely restricted, a hallmark of long isolation.

Previous molecular work had painted a confusing picture. Allozyme studies identified two lineages in the Alps, matching the subspecies adyte and isarica, plus one lineage in the Pyrenees and another in the Carpathians and Balkans. But a mitochondrial study suggested that the subspecies ocellaris and isarica were closer to the Carpathian syrmia than to each other, and two poorly known southern Alpine subspecies, pseudoadyte and kunzi, had never been sampled at all. The number of genetic lineages in the Alps therefore ranged anywhere from two to five depending on which data one trusted. To resolve the confusion, the team sequenced 1,496 base pairs of the mitochondrial COI gene, covering both the standard DNA barcode region and the less commonly used 3-prime section of the gene, in sixteen Alpine and Jurassian populations, and combined the new sequences with published data from the Pyrenees, Cantabria, the Carpathians and the Sudetes.

The resulting dataset of 158 individuals contained fifty-three haplotypes defined by fifty-one variable sites. The haplotype network resolved into five clusters, labelled A through E, and these clusters turned out to be largely congruent with the morphological delineation of subspecies. Remarkably, ninety-eight percent of the haplotypes were private to a single subspecies and eighty-eight percent to a single population, evidence of profound genetic isolation despite the proximity of some ranges. The 3-prime section of COI proved far more discriminating than the barcode region alone, revealing three clades that the standard barcode fragment had left hidden. The analysis confirmed that pseudoadyte and kunzi are genuine, distinct lineages rather than mere look-alikes of adyte and ocellaris, and that the morphologically intermediate western form of kunzi is genetically inseparable from the eastern one, vindicating its original assignment.

The study also settled the contested status of isarica and ocellaris. Earlier work had declared them genetically identical, but the new data showed that these two subspecies share only a single common haplotype, from which each has evolved its own private mutations. The shared haplotype becomes more frequent as one approaches the wide hybrid zone where the two forms meet, a pattern consistent with secondary contact after independent differentiation. Intriguingly, isarica itself split into two genetically distinct sub-lineages, one corresponding to western and northern Alpine populations and the other to eastern Alpine ones, meaning the Alps actually harbour six mitochondrial lineages, four of which had gone unrecognised until now.

To reconstruct where these lineages survived the last ice age, the researchers overlaid the current distributions onto the six broadly recognised categories of potential refugia during the Würm glaciation. When the great glaciers filled the main valleys, habitable conditions persisted in unglaciated lower mountains at the western and eastern edges of the Alps, on the sun-exposed, wind-sheltered slopes along the southern Alpine border, and in pockets along the lobed northern ice front. Each subspecies mapped neatly onto one of these compartments. Pseudoadyte, for example, occupies a territory sharply bounded by the Adda and Adige valleys, exactly matching a single refugial compartment, while kunzi clings to the relict foothills between Val d’Adige and Valcellina. The valleys that dissect the southern Alpine fringe, carved ever deeper by repeated glacial erosion, acted as barriers that fragmented the butterfly into the three lineages adyte, pseudoadyte and kunzi, which now show pairwise genetic divergences of up to 1.15 percent, consistent with long-term isolation within their current borders.

The deepest story, however, lies in the broader geography of the lineages. The clusters sort into three groups: a southern Alpine group, a circum-Pannonian group uniting Carpathian butterflies with those of the northern and eastern Alps, and a western extra-Alpine group. This structure implies an ancient Alpine-Carpathian disjunction, with the common ancestor most plausibly resident in the Carpathians, a hint reinforced by the close genetic affinity between the Carpathian samples and the outgroup species Erebia ligea. During severe cold phases the ancestors retreated to the Pannonian plain, where pollen evidence indicates taiga-like forests and even patches of temperate woodland persisted even at the glacial maximum. When the climate ameliorated, they colonised both the Alps and the Carpathians. A second such retreat and re-expansion then split the circum-Pannonian group into the Carpathian subspecies euryale and syrmia on one side and the Alpine ocellaris, eastern isarica and western isarica on the other.

Dating these events proved subtle. Bayesian molecular dating, calibrated against the roughly 3.5-million-year split between E. euryale and its nearest relative, placed the diversification of the present subspecies between about 0.75 and 2 million years ago. But the geological constraints tell a tighter story: only the most severe glacial phases, beginning with marine isotope stage 22 around 870,000 to 880,000 years ago, drove eastern Alpine glaciers down into the main valleys and expelled subalpine organisms into refugial isolation. The first Alpine-Carpathian split therefore cannot be much older than a million years, and the southern Alpine differentiation of adyte, pseudoadyte and kunzi must predate the Alpine-Pyrenean disjunction, placing it at least as far back as marine isotope stage 10. The star-like haplotype network of the Pyrenean and Jurassian butterflies, typical of a recent expansion after a bottleneck, marks them as a comparatively young divergence, separated from their Alpine relatives no later than the Riss glaciation.

Not every question is closed. Allozyme data place the Pyrenean lineage closer to the northern than to the southern Alps, conflicting with the mitochondrial signal that ties it to the southern Alpine adyte group, a mismatch that only genome-wide nuclear data will be able to arbitrate. The authors also note that Wolbachia infections, known to occur in E. euryale, could in principle have influenced the mitochondrial patterns, and that nuclear genomic data would address this possibility directly. A striking morphological detail offers independent support for the deep splits: the three southern Alpine subspecies share white-pupilled eyespots on the forewing upperside, a trait that appears to be a shared derived character marking the basal division of the species’ history. For a butterfly that most hikers barely notice, Erebia euryale has turned out to be a remarkable archive of Quaternary climate history, one whose pages were written by advancing and retreating ice.

Subject of Research: Phylogeography and Pleistocene diversification of the large ringlet butterfly Erebia euryale based on mitochondrial COI sequences

Article Title: Mitochondrial DNA-based phylogeography of the large ringlet Erebia euryale (Esper, 1805) suggests recurrent Alpine-Carpathian disjunctions during Pleistocene ( Nymphalidae , Satyrinae )

Article References: Cupedo, F., & Doorenweerd, C. (2022). Mitochondrial DNA-based phylogeography of the large ringlet Erebia euryale (Esper, 1805) suggests recurrent Alpine-Carpathian disjunctions during Pleistocene (Nymphalidae, Satyrinae). Nota Lepidopterologica, 45, 65-86. https://doi.org/10.3897/nl.45.68138

Image Credits: AI Generated

DOI: 10.3897/nl.45.68138

Keywords: Erebia euryale, phylogeography, mitochondrial DNA, COI, Alps, Carpathians, Pleistocene, glacial refugia, butterflies, Nymphalidae, subspecies, haplotype network

The review defines rainforest refugia as regions of climatic stability where rainforests and their associated biota persisted through cold and arid periods, and from which species could later expand once conditions improved. These areas act as evolutionary lifeboats: they buffer populations against extinction, preserve deep lineages, and can seed the recolonization of landscapes after the climate relents. Understanding where refugia were located and how they functioned is not merely an academic exercise. Because refugia can mitigate the adverse impacts of contemporary climate change, they are increasingly recognized as priority targets for conservation planning.

The evidence for dramatic vegetation swings in West Africa comes most directly from fossil pollen cores extracted from marine and lake sediments. Deep-sea cores from the Gulf of Guinea, including one near the Nigerian coastline that traces vegetation change over the last ten million years, reveal repeated shifts from closed rainforest to more open vegetation as aridity intensified. Lake cores offer finer, more localized records; the longest continuous archive, from Lake Bosumtwi in southern Ghana, spans roughly 1.08 million years and documents the repeated local disappearance of rainforests during Pleistocene glaciations. Notably, no pollen records yet exist from West African highland regions, leaving a conspicuous gap in the palaeoecological record precisely where some hypothesized refugia may have sheltered forests that captured moisture from stratiform clouds and orographic rainfall.

When pollen data are combined with comparative biogeographic analyses of plants, mammals and birds, a consistent set of large-scale refugia emerges. Regions such as Mount Nimba, Cape Palmas, Cape Three Points and the Niger Delta have been repeatedly identified as areas of long-term climatic stability, and independent diversity surveys confirm elevated species richness and endemism in exactly these places. By contrast, the Dahomey Gap, a dry corridor receiving only around 700 millimetres of annual rainfall between southern-central Ghana and Benin, and the V-Baoulé savannah intrusion in central Côte d’Ivoire were never proposed as refugia, marking them as historically unstable zones that species likely abandoned during arid phases.

Phylogeography, which examines the spatial arrangement of genetic lineages within species, has largely corroborated these large-scale refugia while simultaneously revealing a hidden layer of structure. Across plants, reptiles, amphibians, mammals, birds and fish, recurrent phylogeographic breaks align with major rivers such as the Bandama, Volta, Niger and Cross, as well as with climatically unstable regions. These breaks partition West African rainforests into four well-established sub-regions: Western Upper Guinea, Eastern Upper Guinea, the Dahomey Gap and Western Lower Guinea. Crucially, fine-scale comparative studies of leaf-litter frogs and forest-dwelling rodents uncovered smaller isolated pockets, termed microrefugia, nested within and beyond the classic macrorefugia. Some of these microrefugia, notably in the Fouta Djallon highlands of Guinea and in Ghana, harbour lineages stretching back to the Miocene, suggesting stability over millions of years, while others appear to have persisted only through the more recent Pleistocene aridification cycles.

The timing of these evolutionary splits presents an intriguing puzzle. While phylogeographic patterns are broadly congruent across species, the divergence dates themselves are frequently asynchronous, even among co-distributed species analysed with the same genetic markers. Splits fall predominantly within the Pleistocene but vary widely, and the use of different markers with varying confidence intervals complicates direct comparison. This asynchrony implies that identical spatial patterns may arise from distinct underlying causes, whether climate-driven fragmentation, river barriers or ecological gradients, and underscores the need for standardized analytical frameworks before broad generalizations can be drawn.

To move beyond mapping refugia toward quantifying their evolutionary role, researchers have turned to demographic modelling and species distribution modelling. Demographic approaches compare observed genetic data against simulations run under competing models of diversification: the refugia model, in which populations diverge in isolation and later expand and meet again; the landscape barrier model, in which populations split in strict isolation on opposite sides of a physical obstacle; and the ecotone model, in which divergence occurs alongside continuous gene flow. Studies on West and Central African reptiles and amphibians predominantly support the refugia model, though it has been rejected in favour of barrier or ecotone scenarios for species with broader ecological tolerances, such as arboreal snakes that also inhabit dry forest-savannah mosaics.

Species distribution modelling offers an independent, mechanistic lens on the same question. By correlating species occurrences with environmental variables and projecting those niches back to the Last Interglacial period roughly 125,000 years ago, researchers have reconstructed how suitable habitat expanded and contracted across glacial cycles. The models consistently reveal significant range fluctuations for nearly all examined taxa, from frogs and chimpanzees to forest trees, with the notable exception of the ecologically flexible arboreal snakes. Climatic stability maps derived from these projections tend to incorporate the known refugia of Cape Palmas, Cape Three Points, Mount Nimba and the Niger Delta, while Western Upper Guinea and Western Lower Guinea emerge as extensively stable regions, in contrast to the more fragmented stability hotspots of Eastern Upper Guinea.

The review’s authors emphasize that refugia are not the sole engine of diversification in West Africa, but they played a key role in driving the evolution of rainforest-dependent species in combination with other factors such as river barriers. Ecological traits matter enormously: closely related tree species in the Dahomey Gap responded to the same aridification cycles with different timing of population splits and colonization events, depending on subtle differences in habitat preference and dispersal biology. This species-specific variability means that predicting how rainforest biota will respond to ongoing climate change requires understanding not just where refugia were, but how individual species interacted with them across time.

Looking forward, the authors call for research that spans a broader range of taxa, explores lesser-known regions such as the Fouta Djallon highlands and the Niger Delta, and adopts landscape demography approaches that account for the diverse forest habitats of West Africa, from evergreen lowland to montane forest. Advances in high-throughput sequencing, long-read technologies and integrative bioinformatic tools that combine genomic data with distribution models promise to sharpen the resolution of refugia dynamics across both space and time. As West African rainforests, which have already lost more than 80 percent of their former cover, face intensifying drought and rising temperatures, the lessons encoded in their refugial past may prove the most valuable guide to securing their future.

Subject of Research: Evolutionary refugia in West African rainforests and their role in biodiversity

Article Title: Towards a comprehensive view on evolutionary refugia in West African rainforests

Article References: Ernst, M., Rödel, M.-O., & Blom, M. P. K. (2025). Towards a comprehensive view on evolutionary refugia in West African rainforests. Frontiers of Biogeography, 18, Article e139537. https://doi.org/10.21425/fob.18.139537

Image Credits: AI Generated

DOI: 10.21425/fob.18.139537

Keywords: West Africa, rainforests, refugia, phylogeography, climate change, biodiversity, palaeoecology, species distribution modelling, demographic modelling, Guinean Forests, microrefugia, Pleistocene

The fossils come from the Chochen–Tsailiao locality in Tainan, part of the Chiting Formation dated to the Middle Pleistocene, roughly 800,000 to 400,000 years ago. The collection includes a well-preserved upper molar, a lower last premolar, a fragmentary lower molar and three fragmentary incisors. These teeth were pulled from reworked deposits along the riverbed, mixed from both marine and terrestrial layers, which is why researchers adopt a conservative age range for the material.

Identifying porcupine species from teeth alone is notoriously tricky. The team relied on four key dental characters: overall size, occlusal outline, occlusal pattern and degree of hypsodonty, or enamel height. But as previous studies have shown, the occlusal morphology of Hystrix has remained remarkably conservative from the Miocene through to the present, and crown height barely differs between Pleistocene and living species. That leaves size as the most diagnostic criterion, and here the Taiwanese specimens tell a clear story.

Biometric analysis shows the Chochen–Tsailiao teeth are smaller than those of Hystrix refossa, a very large Plio–Pleistocene porcupine whose lower fourth premolar ranges from 10 to 13 millimetres in length, considerably bigger than the Taiwanese specimen at 9.2 millimetres. The fossils are also larger than Hystrix lagrelii, the smallest known Pleistocene porcupine, and Hystrix vinogradovi, a small European and West-Central Asian species. Instead, the measurements fall squarely within the range of Hystrix subcristata from Middle Pleistocene sites across China.

Morphological features back up the size evidence. The upper molar shows an anteriorly oval and posteriorly square outline with seven enamel islands and no enamel folds, indicating an adult individual. The lower fourth premolar, with its pyriform shape and four lingual synclines, belongs to a subadult. The heavily worn lower molar, with six enamel islands and connected lophids, comes from an old individual. Together, these details match the evolutionary state of H. subcristata populations and distinguish the material from smaller forms like H. lagrelii.

The taxonomic picture is complicated by ongoing debate. Some researchers have treated H. subcristata as a subspecies of the living Malayan porcupine Hystrix brachyura, while others regard it as a distinct species based on skull differences. A more recent proposal even suggested uniting all large Pleistocene porcupines from East and Southeast Asia under a single species, H. kiangsenensis. The team behind the new study follows the classification of H. subcristata as a distinct species, grounded in extensive comparative analyses of both fossil and living skulls. Genetic studies have added further layers of complexity, showing clear distinctions between ancient Tianyuan Cave porcupines and living species while simultaneously highlighting similarities with H. brachyura.

Geography helps rule out some alternatives. Hystrix cristata, the crested porcupine, overlaps in dental size with H. subcristata but is restricted to Africa and westernmost Eurasia, specifically Italy and France, making it palaeobiogeographically improbable that the Taiwanese fossils belong to this species. Hystrix vinogradovi, distributed across Europe and West-Central Asia, is likewise geographically distant. The closest comparable species, H. kiangsenensis from Lang Trang Cave in Vietnam, is similar in size but displays greater hypsodonty and a squarer lateral morphology in the Taiwanese specimen.

The discovery significantly broadens the palaeobiogeographical range of Hystrix. According to the NOW database, the fossil record of H. subcristata stretches from Zhoukoudian in northern China to Tham Wiman Nakin in Thailand, with the easternmost limit previously at Fenghuangshan, China. The geographically most proximal localities to Taiwan are in Fujian Province, China, including Yongan, Jiandaodun and Hulidong from the Middle Pleistocene. The faunal assemblages of Hulidong and Jiandaodun show notable taxonomic similarities to the Chochen–Tsailiao locality, hinting at Middle Pleistocene biogeographic connections between Taiwan and the mainland.

How porcupines reached Taiwan remains an open question. The Chiting Formation has yielded a rich vertebrate assemblage including primates, proboscideans, suids, cervids, rhinoceroses, crocodiles, snakes, a toad, a bird and fishes, suggesting a diverse ecosystem where terrestrial mammals thrived. Many fossils were reworked from mixed marine and terrestrial deposits, complicating precise dating but confirming a Middle Pleistocene age. Whether porcupines crossed land bridges during sea-level lowstands or arrived by other means, the new fossils provide the first concrete evidence for Quaternary mammal dispersal between continental East Asia and adjacent islands.

Future research will focus on quantitative faunal similarity analyses between the Taiwanese locality and mainland sites to clarify these ancient connections. For now, the Chochen–Tsailiao porcupine stands as a testament to the reach of Pleistocene mammals, extending the known distribution of H. subcristata eastwards and marking the first island record for a genus that has roamed Eurasia since the Late Neogene.

Subject of Research: Palaeontology

Article Title: First island colonisation by Hystrix subcristata ( Mammalia , Rodentia ): fossil evidence from Pleistocene, southern Taiwan

Article References: Halaçlar, K., & Lin, C.-H. (2026). First island colonisation by Hystrix subcristata (Mammalia, Rodentia): fossil evidence from Pleistocene, southern Taiwan. Swiss Journal of Palaeontology, 145, 293-302. https://doi.org/10.3897/sjp.145.175168

Image Credits: AI Generated

DOI: 10.3897/sjp.145.175168

Keywords: Hystrix subcristata, porcupine, Taiwan, Pleistocene, island biogeography, palaeontology, First, island, colonisation, Hystrix, subcristata, Mammalia

The Anoa comprise two currently recognized species: the Mountain Anoa (Bubalus quarlesi) and the Lowland Anoa (Bubalus depressicornis), grouped together in their own subgenus, Anoa, within the buffalo genus Bubalus. Both are endemic to Sulawesi, an Indonesian island famous for its extraordinary endemism. Their small stature is a textbook example of insular dwarfism, the phenomenon in which large mammals isolated on islands evolve smaller bodies under limited resources, reduced predation pressure, and ecological niches that favor compact forms. Sulawesi’s prehistoric elephants and stegodons underwent the same transformation, making the Anoa part of a broader evolutionary pattern on the island.

For decades, researchers have proposed two competing hypotheses to explain how large mammals colonized Southeast Asia’s islands. The land-bridge hypothesis holds that during Pleistocene glacial phases, when sea levels dropped by 40 to 120 meters, dry corridors emerged connecting mainland Asia to Borneo, Java, and eventually Sulawesi. The insular route hypothesis, championed by paleontologist von Koenigswald in the 1930s, instead proposes that mammals migrated through the Philippines, hopping from island to island. The new study set out to test these routes directly using molecular phylogeny, reconstructing the ancestral geographic ranges of the Anoa and their relatives.

The research team, working from the Anoa Breeding Center in Manado and the Bontomarannu Education Park, collected 14 fecal samples from Anoa in October 2020, eight from lowland animals and six from mountain animals, along with six water buffalo samples for comparison. Fecal DNA extraction is a non-invasive technique that avoids stressing endangered animals, and the team used the QIAamp Fast DNA Stool Mini Kit to recover genomic DNA. They then amplified two mitochondrial markers: the cytochrome b gene, a 906-base-pair fragment, and the control region, a 696-base-pair fragment, using species-specific primers designed with Primer3 software. Sequencing was performed in both forward and reverse directions to ensure nucleotide integrity.

The phylogenetic analysis drew on a total of 71 mitochondrial sequences, combining the new data with publicly available sequences from GenBank covering other Bubalus species, including the wild water buffalo Bubalus arnee, the tamaraw Bubalus mindorensis from the Philippines, and the extinct Cebu buffalo Bubalus cebuensis. The team constructed Bayesian inference trees using BEAST 2.4 software with the best-fit HKY+G substitution model selected by the Akaike information criterion. Markov Chain Monte Carlo iterations ran for up to 10 million generations, and branches with posterior probability below 0.5 were collapsed. Boselaphus tragocamelus, the nilgai, served as an outgroup to root the tree and clarify relationships within the Bovidae family.

The resulting phylogeny revealed two main clades with strong statistical support. Clade I contained all the Anoa, with mountain and lowland species forming a monophyletic sister group supported by a posterior probability of 0.99 and a bootstrap value of 100. Clade II comprised the water buffalo and the tamaraw. This topology confirms that the Anoa belong within the genus Bubalus as a distinct subgenus, rather than being more closely related to Boselaphus as some earlier studies with very small sample sizes had suggested. The separation of the Anoa clade from other buffalo species highlights their unique evolutionary trajectory compared to mainland relatives.

Divergence time estimation using a Bayesian relaxed molecular clock, calibrated with three fossil-based time constraints, showed that the genus Bubalus diverged during the Early to Middle Pleistocene around 1.6 million years ago. The subgenus Anoa itself split into mountain and lowland species during the Middle Pleistocene, approximately 1.42 million years ago, with a highest posterior density interval of 1.14 to 1.71 million years ago. The subgenus Bubalus, containing the water buffalo and tamaraw, diverged slightly earlier at 1.35 million years ago. These dates align well with the fossil record, which places the earliest water buffalo ancestors in Sundaland during the Pleistocene.

The biogeographic reconstruction, performed with Reconstruct Ancestral State in Phylogenies (RASP) software using statistical Dispersal Vicariance Analysis in a Bayesian framework, produced a decisive answer about colonization routes. Sundaland, comprising Borneo and Java, emerged as the most probable ancestral area for the genus Bubalus in the Indonesian archipelago with a probability exceeding 0.7. For the Anoa ancestor specifically, the analysis assigned the highest probabilities to Sulawesi’s mountain and lowland areas, with only a minor proportion attributed to Sundaland and none to the Philippines. This pattern strongly supports the land-bridge hypothesis over the insular route through the Philippine archipelago.

Geological and fossil evidence reinforces this conclusion. During Pleistocene glacial maxima, sea levels dropped by 40 to 50 meters, connecting the Malay Peninsula to Java and Borneo across the Sunda Shelf. A drop of 120 meters extended dry land further, and the Makassar Strait separating Borneo from South Sulawesi narrowed to roughly 50 kilometers, allowing dispersal corridors. The fossil ancestor Bubalus palaeokerabau has been recovered from Cisaat in Java, and prehistoric rock art in Gua Batti, South Sulawesi, appears to depict Anoa. Other Sulawesi mammals, including babirusa, macaques, and tarsiers, show similar colonization patterns from Sundaland, consistent with the molecular findings.

The implications for conservation are urgent. Anoa populations have declined by 90 percent over the past 16 years, and both species are listed on CITES Appendix I, prohibiting international trade. Habitat fragmentation and deforestation on Sulawesi continue to isolate populations, reducing genetic diversity and gene flow between fragmented habitats. Because Sulawesi is an island with exceptionally high endemism, protecting the two Anoa species will help conserve many other unique species sharing their ecosystem. The study’s authors recommend expanding sample sizes and incorporating genomic approaches alongside fossil evidence to refine the evolutionary framework. For now, the mitochondrial DNA has spoken clearly: the dwarf buffalo of Sulawesi walked across ancient land-bridges from Sundaland, not island-hopped from the Philippines, and their 1.42-million-year isolation on the island has produced one of Asia’s most distinctive and most endangered bovines.

Subject of Research: Biogeographic history and phylogeny of the endangered Anoa dwarf buffalo based on mitochondrial DNA

Article Title: Biogeographic history of the endangered dwarf buffalo, subgenus Anoa ( Bovidae : Bubalus quarlesi and Bubalus depressicornis ): a perspective based on mitochondrial DNA phylogeny

Article References: Priyono, D. S., Solihin, D. D., Farajallah, A., & Purwantara, B. (2024). Biogeographic history of the endangered dwarf buffalo, subgenus Anoa (Bovidae: Bubalus quarlesi and Bubalus depressicornis): a perspective based on mitochondrial DNA phylogeny. Evolutionary Systematics, 8(2), 311-321. https://doi.org/10.3897/evolsyst.8.132970

Image Credits: AI Generated

DOI: 10.3897/evolsyst.8.132970

Keywords: Anoa, Sulawesi, mitochondrial DNA, phylogeny, biogeography, insular dwarfism, Pleistocene, Sundaland, conservation, Bubalus, Biogeographic, history

The Niederweningen site is one of the richest Late Pleistocene localities in Europe. During the summer of 1890, gravel excavation for a new railway embankment exposed more than 100 mammoth bones, tusks and molar teeth belonging to at least seven individuals, embedded in a peat horizon within lacustrine silts. Formal excavations led by the Zürich zoologist Arnold Lang the following year recovered a largely complete perinatal mammoth skeleton, now displayed in the Natural History Museum of the University of Zurich. Radiocarbon and luminescence dating place the Upper Peat Complex, which yielded the remains, between roughly 60,000 and 40,000 years before present, during the early to middle part of Marine Isotope Stage 3. At that time the valley floor was an acid swamp fringed by reeds and mossy pools, in an open tundra-like landscape some four degrees Celsius cooler than today, with mean July temperatures of about ten degrees and winter means below minus ten.

Determining the age at death of a perinatal proboscidean is notoriously difficult, because the skeletons of late foetuses and newborn calves are strikingly similar. The team therefore attacked the problem from four directions: ontogenetic allometry, meaning how proportions change with growth, especially compared with perinatal mammoths from Russia; the microstructure of the long bones; the sequence of tooth eruption; and the timing of cranial suture closure. Measurements were taken with callipers to an accuracy of a hundredth of a millimetre, following established protocols for proboscidean teeth and appendicular bones, and the fossils were scanned with a NIKON XTH 225 ST micro-CT scanner hosted by the University of Zurich. The tibia was scanned at 139 kilovolts and 198 microamperes, yielding a voxel size of about 0.104 millimetres, while higher-resolution scans of the palate and mandible resolved features as small as 0.026 millimetres. Segmentation software then allowed the researchers to trace internal growth layers through the scan stacks and render external bone surfaces semi-transparent.

The most compelling evidence of postnatal life came from the tibial midshaft. In cross-section, the cortical bone remains thin and porous, with extensive trabecular bone throughout the diaphysis, indicating active endochondral ossification. Quantitative analysis revealed a porosity of 76.08 percent, reflecting the enormous proportion of void spaces in the developing bone, together with a woven-parallel fibrolamellar matrix and laminar to plexiform vascularisation, a combination characteristic of very rapid appositional growth. Crucially, a distinct change in tissue microstructure in axial view marks the boundary between prenatal and postnatal periosteal bone deposition, a transition previously documented in full-term stillborn and neonatal African elephants. The postnatal layer in the Niederweningen tibia closely resembles the bone microstructure of neonatal Columbian mammoths, and a similar layer of postnatal deposition was identified in the maxilla. Together these findings strongly indicate that the calf survived birth, even though its dentition shows no obvious wear.

That absence of wear is itself puzzling. In woolly mammoths, crown wear on the second deciduous premolar supposedly begins at zero to one months of age, and on the third deciduous premolar at roughly 0.3 to 0.4 months. The Niederweningen calf’s palate preserves four teeth in situ: the second deciduous premolars with four plates each and the third deciduous premolars with seven plates, with crown formation complete and no interplate cementum deposition. Odontochronologically, the individual probably belongs to Dental Stage 1, spanning three months to two years. What the teeth do show, on all five remaining teeth, are tiny pits etched into the enamel at the tips of the plate conules, in some cases penetrating through the enamel and into the dentine, visible both to the naked eye and in the micro-CT scans.

The origin of these lamellar pits has long been debated. In the famous Yamal Peninsula calf Lyuba, which died at about one month, virtually identical pits were attributed either to incomplete mineralization or to postmortem dissolution pitting, possibly caused by bacteria producing lactic acid, rather than to mastication. Breast milk is weakly acidic to neutral, with a pH of 6.5 to 7.5, and lactose can be fermented by amelolytic oral bacteria such as Streptococcus mutans, leading to enamel demineralization. Strontium-to-calcium and barium-to-calcium ratios in mammoth juveniles suggest that plant consumption began only between two and three African Elephant Equivalent Years, far later than weaning initiation in extant elephants, although the stomach contents of the month-old Lyuba indicate coprophagy. The delayed introduction of plant food supports the interpretation that the pits formed for reasons other than eating vegetation.

One histological feature the team could not confirm is the neonatal line, a prominent microfeature in dentine and enamel, expressed as enlarged striae of Retzius, that records the physiological stress of birth and separates tissue formed before and after delivery. In Lyuba and the Khroma calf, whose ages at death were estimated at about 30 to 35 days and 52 to 57 days respectively, the line was identified by counting daily or weekly dentine growth increments between the line and the pulp cavity surface. The researchers attribute their inability to detect it in the Niederweningen teeth partly to method: micro-CT is non-destructive and three-dimensional but produces lower-resolution images than histological sectioning under cross-polarized light. They also raise a provocative climatic hypothesis. Both previously documented mammoth neonates came from above 70 degrees north, inside the Arctic Circle, whereas Niederweningen lies at 47 degrees north with a milder climate. In humans, children born in milder climates have thinner neonatal lines, because birth stress is reduced and maternal and foetal metabolism can follow the circadian rhythm, and season of birth also influences line thickness, with spring and summer births producing thinner lines.

Among the most striking anatomical findings is anisomelia of uncertain aetiology, a marked asymmetry in which the right foreleg is stunted relative to the left. The radii and ulnae display the discrepancy clearly. Anisomelia may be congenital, as in hemihypertrophy, when one side of the body grows more than the other, or acquired through trauma or disease. The condition can affect gait, posture and spinal alignment, and the authors speculate that the stunted right foreleg may have contributed to the calf’s death. Juvenile proboscideans seldom stray from their mothers or the herd, but they are not uncommonly entrapped in swamps or watering holes, and the team suggests the animal may have become mired in the quagmire when ground frozen solid in winter thawed during the brief summer months, a scenario also proposed for the articulated adult mammoth excavated at the site in 2003.

The allometric comparisons reveal wide size variation in dental and appendicular dimensions, some of it non-ontogenetic. First-born calves in African elephants are typically 15 percent smaller than subsequent offspring, a pattern that appears to hold in mammoths as well. Spatio-temporal environmental differences, nutritional status and genetic diversity may also play a role. Mammoth populations belonged to regionally structured mitochondrial clades, and the Niederweningen assemblage probably belongs to Clade I, which ranged across trans-Beringian Eurasia and North America, unlike many Russian mammoths. The humerus from Niederweningen is significantly smaller than that of a one-year-old Russian mammoth and almost identical to a neonate, while the radius is significantly larger than the Russian neonate and the tibia overlaps with one-year-olds, all pointing to a postnatal individual of at most a few months.

Beyond the individual calf, the study carries broader implications for mammoth ecology and extinction. Proboscideans sit at the slow end of the fast-slow life-history continuum, with the longest gestation of any land mammal, about 22 months, single offspring and the largest neonates. Yet the bone microstructure of the Niederweningen calf demonstrates remarkably rapid postnatal growth, even as the absence of tooth wear from mastication reinforces evidence of strong maternal dependence and an altricial life-history strategy, likely an adaptation to seasonal fluctuations in resource availability at high latitudes and to increased predation risk. The authors note that this extended period of dependence may have been significant for extinction if mothers were hunted, leaving calves unable to survive alone. The woven bone, the absence of extensive secondary osteons and the lack of significant biomechanical loading all confirm a perinatal stage, and the team argues that microanatomical investigation of long bones provides an effective method for distinguishing prenatal from postnatal mammoths, one that would benefit greatly from a more complete ontogenetic series in future studies.

Subject of Research: Perinatal woolly mammoth from Niederweningen, Switzerland

Article Title: Anatomy of a perinatal woolly mammoth ( Mammuthus primigenius ) from Niederweningen (Late Pleistocene), Switzerland

Article References: Scarborough, M. E., Furrer, H., Scheyer, T. M., Sánchez-Villagra, M. R., & Carrillo-Briceño, J. D. (2026). Anatomy of a perinatal woolly mammoth (Mammuthus primigenius) from Niederweningen (Late Pleistocene), Switzerland. Swiss Journal of Palaeontology, 145, 487-504. https://doi.org/10.3897/sjp.145.183721

Image Credits: AI Generated

DOI: 10.3897/sjp.145.183721

Keywords: Anatomy, perinatal, woolly, mammoth, Mammuthus, primigenius, Niederweningen, Late, Pleistocene, Switzerland, scientific research

The research centers on a sediment core recovered in 1999 by the French research vessel Marion-Dufresne from the bottom of the Norwegian Basin at a depth of 2,800 meters, along the eastern flank of the Jan Mayen Ridge. Within a 7.1-meter segment of this core, scientists identified 15,391 fossil ostracod specimens from 432 individual sediment layers, representing 40 genera and 95 species or species groups. Ostracods are tiny bivalved crustaceans, typically smaller than a poppy seed, whose calcium carbonate shells preserve exceptionally well in ocean sediments. Because different species thrive under different temperature, salinity, and productivity conditions, their fossilized remains serve as sensitive indicators of past environmental change.

What makes this study particularly striking is the sheer dominance of two genera throughout the entire 260,000-year record. Krithe accounted for approximately 60 percent of all specimens, with a single species, Krithe hunti, contributing 9,266 individuals. Cytheropteron made up another 20 percent. Together, these two genera constituted more than 80 percent of the entire fossil assemblage. Yet within this apparent uniformity, the researchers uncovered subtle but ecologically meaningful species-specific responses to glacial and interglacial cycles that reveal the Norwegian Sea as a fundamentally distinct deep-water domain, partly decoupled from the open North Atlantic.

One of the most surprising discoveries involves the genus Argilloecia, a key indicator of climatic transitions. In the deep North Atlantic, Argilloecia is consistently found during deglaciations and warming phases, when melting ice sheets release freshwater and ocean circulation reorganizes. But in the Norwegian Sea core, the genus appeared exclusively during cooling phases, specifically around the transition from interglacial MIS 15 to glacial MIS 14 approximately 563,000 years ago. No specimens were recorded during deglaciations at all. This opposing temporal distribution suggests that the environmental conditions favoring Argilloecia in the Norwegian Sea are fundamentally different from those in the North Atlantic, likely reflecting regional differences in water mass structure, freshwater sensitivity, and deep-water ventilation.

Another intriguing finding concerns Echinocythereis echinata, a species that is entirely absent from modern Nordic seas but was present in the Norwegian Basin during Marine Isotope Stages 12 and 11, approximately 455,000 to 380,000 years ago. Today, E. echinata is restricted to marine environments south of Iceland, influenced by water masses of the North Atlantic proper. Its presence in the Norwegian Sea during the Middle Pleistocene, followed by its complete disappearance from the region, indicates a southward range contraction that occurred sometime between MIS 11 and the present day. This pattern suggests that even species with apparently broad climatic tolerances can undergo significant biogeographic shifts in response to long-term environmental changes, a finding with clear implications for predicting future species redistributions under anthropogenic warming.

Perhaps the most tantalizing discovery involves Rosaliella svalbardensis, a species previously considered endemic to cold-seep environments around Svalbard, where methane bubbles rise from the seafloor through pockmarks on the Vestnesa Ridge. Eight specimens of this species were recovered from full interglacial samples in the Norwegian Sea core, roughly 10 degrees of latitude farther south than its known range. The researchers suggest this could tentatively indicate the presence of a paleo-cold seep near the drilling locality, hinting at past methane release from the seafloor in a region where no such activity has been documented. However, they caution that the inference is based on very limited material and that no independent geochemical evidence has yet been found to confirm seep activity.

The study also documents the presence of shallow-marine, allochthonous taxa in several sediment layers, indicating that downslope transportation processes along the Jan Mayen Ridge delivered coastal species into the deep basin. These transported taxa appeared primarily during late interglacial intervals, as the climate began cooling toward glacial conditions. The researchers attribute this pattern to a combination of sediment availability and slope instability: during late interglacials, shallow-marine sediments remain abundant and are mobilized by increasing density currents, while during full glacial periods, reduced shelf sediment supply limits such transport. This finding underscores the importance of distinguishing between in-situ deep-sea communities and reworked material when interpreting fossil assemblages.

The timing of the study is particularly significant because the youngest samples fall within the Mid-Brunhes Event, a fundamental shift in climate cyclicity that occurred between approximately 430,000 and 350,000 years ago. During this transition, glacial-interglacial variability shifted from a low-amplitude to a high-amplitude mode, resulting in more intense interglacials and more severe glaciations. In the Arctic, this event triggered what researchers call MBE-enhanced Arctic Amplification, characterized by fundamental changes in sea ice cover, surface productivity, and ocean temperature. The ostracod assemblages in the Norwegian Sea core show clear faunal responses across this interval, including the appearance of Henryhowella asperrima during late MIS 12 and the sustained presence of Eucythere argus throughout MIS 11, where it reached relative abundances of up to 45 percent.

Comparing the Norwegian Sea record to North Atlantic reference sites reveals stark and persistent differences in benthic faunal composition. During the Holocene, the Norwegian Sea assemblage is dominated by Krithe and Cytheropteron, while the North Atlantic is characterized by Henryhowella and Krithe. During the Eemian interglacial (MIS 5e), however, the two basins showed more similar generic compositions, suggesting that the physicochemical characteristics of their deep waters may have been more comparable during that period. These contrasts cannot be explained by bathymetry alone, as the two sites differ by only about 600 meters in water depth. Instead, they point to fundamentally different water mass structures, freshwater influences, and environmental stability between the Nordic seas and the open North Atlantic.

The implications of this research extend far beyond academic curiosity. The Norwegian Sea is a critical node in the global thermohaline circulation, where North Atlantic Deep Water forms and spreads throughout the world’s oceans. Understanding how deep-sea ecosystems in this region responded to past climate transitions provides essential context for predicting their vulnerability to current and future warming. The finding that warming phases were not consistently associated with improved benthic habitat suitability in the Norwegian Sea challenges the assumption that climate amelioration benefits deep-sea life uniformly. Instead, prolonged freshwater influence, enhanced stratification, and reduced deep-water ventilation may have created unfavorable conditions for certain taxa even as surface waters warmed. As the Arctic continues to warm at rates far exceeding the global average, and as meltwater input to the Nordic seas increases, the deep-sea communities documented in this fossil record may face conditions that echo those of past transitions, but at a pace that could exceed their adaptive capacity.

Subject of Research: Deep-sea ostracod palaeoecology in the Norwegian Sea during the Middle Pleistocene

Article Title: Palaeoenvironmental implications of the deepwater ostracod ( Crustacea , Ostracoda ) fauna in the Norwegian Basin during the Middle Pleistocene (MIS 10–15)

Article References: Jöst, A. B., Bauch, H. A., Stepanova, A., Okahashi, H., & Yasuhara, M. (2026). Palaeoenvironmental implications of the deepwater ostracod (Crustacea, Ostracoda) fauna in the Norwegian Basin during the Middle Pleistocene (MIS 10–15). Fossil Record, 29(1), 135-169. https://doi.org/10.3897/fr.29.177205

Image Credits: AI Generated

DOI: 10.3897/fr.29.177205

Keywords: ostracods, Norwegian Sea, Pleistocene, palaeoceanography, Mid-Brunhes Event, deep-sea biodiversity, glacial cycles, Krithe, Cytheropteron, cold seeps, Jan Mayen Ridge, marine microfossils

The dispute is old. Discussions about what killed off the megafauna stretch back to the late eighteenth and early nineteenth centuries, when early naturalists first grappled with the realization that entire suites of enormous animals had disappeared from continents where humans and fossils coexisted. Over more than two centuries, the debate has cycled through hypotheses implicating rapid climate swings at the end of the Pleistocene, the spread of anatomically modern humans and their hunting technologies, disease, comet impacts, and combinations of these forces. What began as an argument among archaeologists and paleontologists has, in recent decades, drawn in ecologists and conservation biologists, who see the late Quaternary extinctions as a natural experiment with direct lessons for how modern ecosystems might be managed, restored, or even rewilded.

That expansion has brought energy and expertise, but it has also brought a problem. Dozens of papers on the topic appear each year, and alongside them a steady stream of review articles. Yet, as the authors of the new study note, these reviews tend to reflect the viewpoints of their authors, filtering the literature through particular disciplinary lenses and, sometimes, particular conclusions. A paleontologist’s synthesis may weigh evidence differently than an archaeologist’s or an ecologist’s, and readers are left without an objective map of the terrain. Recognizing this limitation, the research team set out to build a data-driven overview of the entire debate, treating the published literature itself as the object of study.

The approach was systematic in the strict sense. Rather than selecting studies that support a favored hypothesis, the researchers assembled and analyzed the literature in a structured way designed to minimize bias. Their goals were threefold: first, to trace how the megafauna extinction debate has developed and evolved over time; second, to identify the key thematic and conceptual foci within the body of work; and third, to use that synthesis of historical trends and interdisciplinary variation to propose a forward-looking research agenda. The aim of the agenda is not to declare a winner in the extinction debate but to encourage greater engagement, discussion, integration, and collaboration across the many fields that now touch the question.

The analysis surfaced three major findings. The first is that strong disciplinary divides persist. Researchers trained in different fields frame the problem differently, favor different lines of evidence, and often publish in separate venues, with the result that key arguments circulate within disciplinary silos rather than across them. The second is that research coverage is uneven in both time and space. Some regions and some periods of the late Quaternary have been intensively studied, while others remain comparatively neglected, leaving the global picture built on a patchy foundation. The third is that despite decades of work and major methodological advances, uncertainty over the causes of the extinctions remains persistent. The debate has not converged; it has, in some respects, become more intricate as new data and new techniques have multiplied the possible interactions among climate change, human pressures, and species biology.

The methodological evolution of the field is itself striking. Over the past several decades, researchers have deployed increasingly advanced analytical and statistical methods to the extinction question. Dating techniques have sharpened chronological frameworks, allowing the timing of megafauna losses to be compared against the timing of human arrival and climatic transitions with growing precision. Statistical modeling has been used to test competing extinction hypotheses against empirical patterns, and ancient DNA has opened windows into population histories of extinct species. Yet the systematic review shows that these advances have not dissolved the disagreement. Instead, the field remains fragmented, with methodological sophistication coexisting alongside conceptual division.

Why does the fragmentation matter? The stakes extend well beyond academic scorekeeping. Ecologists and conservation biologists increasingly view the late Quaternary extinctions as a lens through which to inform contemporary conservation and ecosystem management strategies. If the causes of those ancient losses are misread, the lessons drawn for modern conservation may be distorted as well. Understanding whether climate, humans, or their interaction drove past megafauna declines shapes how scientists think about the vulnerability of today’s large mammals, many of which face comparable pressures of habitat loss, hunting, and rapid environmental change. The extinction debate is, in this sense, not merely about the past; it is a live input into decisions about the future of ecosystems worldwide.

The forward-looking research agenda proposed by the study responds directly to the fragmentation it documents. The authors call for greater interdisciplinary collaboration, arguing that the strongest progress will come when archaeologists, paleontologists, ecologists, geologists, and statisticians work from shared datasets and shared frameworks rather than parallel conversations. They also emphasize the need to expand field and legacy studies, which means both new excavations and surveys and the reanalysis of existing museum collections and previously published data with modern methods. Species-specific approaches receive particular attention: rather than treating megafauna as a monolithic category, the agenda urges researchers to examine how individual species with different body sizes, reproductive rates, habitats, and histories responded to the pressures of the late Quaternary.

Integration of cutting-edge scientific and statistical techniques rounds out the proposed agenda. The review suggests that the field’s next phase should combine advanced modeling, improved chronological control, and interdisciplinary data synthesis in ways that explicitly test competing hypotheses rather than accumulating evidence for favored ones. The researchers frame this as a way to foster engagement and discussion across fields, converting the debate’s long history of disagreement into a structured program of collaborative inquiry. The emphasis on discussion and integration reflects the study’s core message: the extinctions are too complex, and the evidence too scattered across disciplines, for any single field to resolve the question alone.

What emerges from the systematic review is a portrait of a debate that has endured for more than two centuries because the underlying problem is genuinely hard. The late Quaternary extinctions unfolded across multiple continents, under varying climatic regimes, alongside human populations at very different stages of technological development, and among species with widely varying ecologies. Disentangling those threads requires the combined strengths of many disciplines, sustained fieldwork in understudied regions and periods, and analytical methods capable of handling the interactions among multiple potential drivers. The new study does not settle the extinction debate, and it does not claim to. Instead, it offers the field something arguably more valuable: an objective, data-driven account of where the debate stands, where its blind spots lie, and how researchers across disciplines might move forward together. For a question that has resisted resolution since the age of Cuvier, that may be the most important contribution yet.

Subject of Research: Megafauna Extinction Debate Systematic Review

Article Title: The state of the late Quaternary megafauna extinction debate: a systematic review and analysis

Article References: Stewart, M., Peters, C., Ziegler, M. J., Carleton, W. C., Roberts, P., Boivin, N., & Groucutt, H. S. (2025). The state of the late Quaternary megafauna extinction debate: a systematic review and analysis. Frontiers in Mammal Science, 4, Article 1678231. https://doi.org/10.3389/fmamm.2025.1678231

Image Credits: AI Generated

DOI: 10.3389/fmamm.2025.1678231

Keywords: megafauna, extinction, late Quaternary, systematic review, paleontology, archaeology, conservation biology, Pleistocene, mammoths, interdisciplinary research, state, late

The answer matters because the freshwater faunas on either side of the Tibetan Plateau are strikingly different. Central Asia hosts few endemic freshwater snails, and most of its species carry the genetic signatures of post-glacial recolonization from northern and western refugia. South and east of the Tibetan Plateau, by contrast, the faunas are highly endemic and deeply structured, the products of long isolation in a geologically restless landscape. Shared species between the two regions are rare, and when they do appear, the explanations range from modern accidental introductions, increasingly common as aquatic ecosystems are transformed, to relicts of ancient dispersal events during warmer, wetter epochs when Eurasia’s rivers and lakes were far more connected than today.

The new populations were found at two sites in southeastern Kazakhstan about 200 kilometers apart. The first was a small pasture pond on the shore of the Kapchagay Reservoir near the city of Konaev, sampled in November 2024 when air temperatures were below freezing and a thin film of ice covered part of the water. Seventeen specimens were collected from silt, stones, and aquatic vegetation. The second site, near the settlement of Chundzha, was a hydrothermal stream fed by an artificially drilled borehole with a constant outlet temperature of 16 to 21 degrees Celsius, where the snails were abundant both inside the borehole and in the outflow. Sixty-nine specimens were taken there. At both sites, the only other gastropod present was Physella acuta, a globally invasive North American species, and no other snails were recorded.

Morphological examination pointed firmly to Radix plicatula. The shells were small, with the largest reaching 8.8 millimeters in height, and the anatomy of the reproductive system, including a penis sheath about equal in length to the praeputium and a distinctive elongated trapezoidal pyriform body, matched recent descriptions of the species. Genetic analysis sealed the identification. The researchers amplified a 469-nucleotide fragment of the mitochondrial cytochrome c oxidase subunit I gene, the standard DNA barcoding marker, and built phylogenetic trees using maximum likelihood and Bayesian inference on a dataset of 65 sequences with Galba truncatula as an outgroup. The Tien Shan specimens fell squarely within the main Radix plicatula lineage, alongside sequences from eastern China near the species’ type locality.

What came next was the real surprise. Across the species’ full range, 235 analyzed sequences revealed 118 haplotypes, and the nine Tien Shan sequences alone contained six distinct haplotypes, yielding a haplotype diversity of 0.89 and a nucleotide diversity of 0.65 percent for a single geographically restricted population. The Tien Shan haplotypes sat just two to three mutational steps from their closest relatives in China, Japan, and Korea, with one haplotype differing by five steps, and they formed a star-like pattern typical of populations descended from a common ancestor that then expanded. Demographic tests reinforced that impression: Fu’s Fs was strongly negative and highly significant, and the mismatch distribution fit a model of sudden demographic expansion.

That level of diversity is hard to reconcile with a recent introduction. Freshwater snails carried by humans, whether through fisheries stocking, aquarium releases, or ballast, typically show pronounced founder effects, with one or a few haplotypes dominating and genetic diversity drastically reduced. Introduced South American populations of Galba truncatula, for example, retain only four COI haplotypes despite at least two independent colonization events, and most invasive populations of Pseudosuccinea columella worldwide belong to a single mitochondrial haplotype. Even the naturally colonizing Icelandic lineage of Ampullaceana balthica, roughly 5,000 years old, carries clear founder signatures with reduced diversity. The Tien Shan snails show a hint of the same star-like structure, but six haplotypes among nine individuals, several of them relatively divergent, looks far more like a population that has persisted and diversified in place than one founded recently from a handful of stowaways.

Could the genetic invasion paradox explain the pattern, with multiple introductions from different sources admixing to restore diversity? The authors consider this unlikely. In documented cases the introduced populations retain recognizable genetic contributions from geographically distant native lineages, which is not what the data show. The Tien Shan haplotypes form a compact group closely related to East Asian lineages and separated from them by only a few substitutions, consistent with expansion within a single evolutionary lineage. Moreover, Radix plicatula is a comparatively localized species, not a global invader repeatedly shuttled between continents, and the usual introduction routes into Central Asia appear closed to it: it has never been recorded in the large water bodies where fishery-associated introductions occur, such as Lake Balkhash, and it is not commonly kept in aquaria.

Rough age estimates from mitochondrial divergence point in the same direction. Depending on whether one assumes COI divergence rates of 1.0, 1.5, or 2.0 percent per million years, the mean within-lineage divergence of the Tien Shan population corresponds to roughly 0.32 to 0.64 million years, and the maximum observed divergence to 0.65 to 1.27 million years. These are coarse approximations rather than formal molecular dates, but they sit comfortably within the Middle to Late Pleistocene and match divergence times reported for other freshwater mollusks whose East Asian and Central Asian populations split during the same era. A recent introduction measured in decades or even centuries cannot plausibly generate this much mitochondrial diversity.

Species distribution modeling added an ecological twist. The team built 19 model variants using four algorithms, generalized linear models, boosted models, random forests, and maximum entropy, combined into weighted ensembles, and trained on occurrence records from GBIF and earlier studies alongside the new Kazakh finds. A model with pseudo-absences drawn from the entire study area performed best on paper, with an AUC of 0.99, but its projection confined the species’ potential niche to East and Southeast Asia, echoing an earlier study. The authors argue this approach is biologically misleading, because it mainly teaches the model to distinguish the region of current occurrence from everywhere else. A model using a restricted 50-kilometer buffer around occurrence records, plus land-cover variables, predicted dramatically broader suitability, sweeping across northern Central Asia and much of Europe. The current range, in other words, is not simply a map of the climate the snail can tolerate; dispersal limits and possibly competition with close relatives such as Radix euphratica appear to hold it back.

The most evocative result came from projecting the niche models onto paleoclimates spanning the Pliocene warm periods, the Last Interglacial, and the Pleistocene glacial cycles. Nearly every projection showed an almost continuous belt of suitable habitat north of the Tibetan Plateau and the great Asian mountain systems, a corridor absent under present-day conditions. Taking the modeling caveats seriously, paleoclimatic reconstructions carry uncertainty, and the Pleistocene projections used six variables instead of eight, the authors interpret this belt as a plausible, previously overlooked dispersal pathway linking East and Central Asia, likely traversed not as continuous rivers but through lake chains and bird-mediated passive transport of the snails themselves. A Tibetan route is considered less likely, since decades of intensive sampling have never found Radix plicatula on the plateau. If the northern corridor hypothesis holds, Central Asia’s freshwater fauna may owe more to Pleistocene contingency than to present-day climate, and the humble snail of the Tien Shan springs may be a living relict of a world far better connected than our maps suggest.

Subject of Research: Phylogeography and species distribution modeling of the pond snail Radix plicatula in Central Asia

Article Title: Recent introduction or evidence for a northern dispersal corridor between East and Central Asia? The case of Radix plicatula

Article References: Nekhaev, I. O., Omarova, A. M., & Ishayeva, A. A. (2026). Recent introduction or evidence for a northern dispersal corridor between East and Central Asia? The case of Radix plicatula. Frontiers of Biogeography, 19, Article e194218. https://doi.org/10.21425/fob.19.194218

Image Credits: AI Generated

DOI: 10.21425/fob.19.194218

Keywords: Radix plicatula, freshwater snails, biogeography, Kazakhstan, Tien Shan, Pleistocene, dispersal corridor, phylogeography, species distribution modeling, mitochondrial DNA, paleoclimate, Tibetan Plateau