Late Miocene Research Articles

Transition From Late‐Miocene Syn‐Orogenic Extension to Plio‐Pleistocene Corinth Rifting in the Southern Hellenides, Northern Peloponnese, Greece

AbstractThis study investigates the Late Miocene to Pliocene transition from contractional to extensional tectonics in the upper plate of the Western Aegean retreating subduction system focusing on the Northern Peloponnese area, Greece. A new 3D tectonic model based on field data and cross‐sections clarifies the relationship between Corinth Rift (CR) normal faulting and inherited structures of the Hellenides belt. The tectonic history is divided into five stages: (a) Late Oligocene to Early Miocene ductile high‐pressure, low‐temperature metamorphism of the Phyllite‐Quartzite (PQ) Unit in the Hellenic subduction channel, synchronous with emplacement of overlying Hellenides nappes, (b) syn‐orogenic ductile exhumation of the PQ Unit at the subduction interface below the Cretan detachment (24–14 Ma), (c) Late Miocene underplating and vertical exhumation of the PQ Unit accommodated by thinning of the Hellenides nappe stack on low‐angle normal faults (LANFs) rooting into the Cretan detachment, followed by (d) NW‐SE‐trending high‐angle normal faulting, and (e) initiation of Corinth rifting by N‐S extension at 4–3.5 Ma. New results show that the LANFs all pre‐date Corinth rifting, forming above and around the NNW‐SSE‐trending, N‐plunging PQ dome, so that their strike varies from E‐W in the north to NE‐SW further south. Alluvial sediments deposited above E‐W‐striking LANFs are crosscut by early high‐angle CR faults. The northern termination of the PQ dome partially controls the location and segmentation of the CR. The transition from regional contraction to extension is attributed to changes in subduction dynamics at 8–5 Ma and to the SW propagation of the North Anatolian fault.

Phalacrocorax bakonyiensis n. sp., a new species of cormorant from the Late Miocene of Hungary

Abstract We describe Phalacrocorax bakonyiensis n. sp. an extinct member of the cormorants (Phalacrocoracidae). The fossil was found in 2021 by geologist János Futó in the sediments of a small cave cavity on the side of Várhegy in Sümeg, a part of the Bakony Mountains of West Hungary, where Late Miocene (MN11–12) vertebrate fossils have been found in the past decades. The total number of bone fragments collected was 14, of which only three can be identified. Two of these belong to adults and one, due to its poor preservation and size, to a very young specimen.

Evolutionary change of crystallographic orientation and coccolith morphology: Neogene-Quaternary Umbilicosphaera (Prymnesiophyceae) lineage

The crystallographic orientation and its relationship to the morphology of coccoliths were investigated for the Neogene-Quaternary calcareous nannoplankton Umbilicosphaera lineage using scanning electron microscopy (SEM) and electron back-scattered diffraction (EBSD). The c-axis of the calcite forming the distal shield elements was inclined upward at 66–68° (U. sibogae), 65–68° (U. foliosa), 57–58° (U. rotula), and 55–57° (U. patera) from the coccolith plane. Accordingly, the outward dip angle of one of the {101¯4} faces forming the surface of the distal shield of U. patera coccolith was shallower than those of U. sibogae and U. foliosa, explaining the nearly flat distal shield and the steep inner slope, formed by another equivalent {101¯4} face, around the central opening of U. patera. Our results showed that the evolution from U. rotula to U. patera during the Late Miocene was not accompanied by a change in crystallographic orientation. In contrast, the evolution from U. patera to U. sibogae and U. foliosa during the Pliocene was accompanied by a rotation of the orientation. The crystallographic orientation of calcite nuclei on the baseplate with a combination of other factors would have resulted in species-specific differences in shield shape and suture lines within the same phylogeny, consequently producing morphological diversity in the coccolith throughout geological time.

New fossil anhingids from the upper Acre River (Late Miocene of southwestern Amazon).

Four extant species of anhingids are found worldwide, all belonging to a single genus (Anhinga). However, the fossil record reveals a much greater diversity of this group in the past. The oldest known anhingids date back to the upper Oligocene period in Australia, but during the Miocene epoch in South America, they achieved their most remarkable diversity. This study describes newly discovered anhingid fossils from the Late Miocene period in South America. These fossils were extracted from the Acre conglomerate member, part of the Upper Miocene deposits in the southwestern Amazon region. The described fossils consist of two fragments of pelvic girdles, two femora, and two vertebrae belonging to a giant anhingid (Macranhinga sp.), as well as a vertebra from Anhinga minuta, the smallest of all darters. The examination of these fossils suggests the presence of potentially three distinct anhingid taxa within the same locality. The environment in which the conglomerate deposits were formed was ecologically complex. It is likely that these three species coexisted within the same ecosystem but avoided direct competition for food and reproductive sites by not fully exploiting their fundamental niche.

New reports, updates, and additional comments about Neobrachytherium ullumense Soria, 2001 (Litopterna, Proterotheriidae) in the Late Miocene of Uruguay and Argentina

New reports, updates, and additional comments about Neobrachytherium ullumense Soria, 2001 (Litopterna, Proterotheriidae) in the Late Miocene of Uruguay and Argentina

The stratigraphy of seep-impacted sediment in the “Verghereto marls” (Santa Sofia, Italy): insights into the Late Miocene evolution of the Romagna foredeep

The stratigraphy of seep-impacted sediment in the “Verghereto marls” (Santa Sofia, Italy): insights into the Late Miocene evolution of the Romagna foredeep

Fig leaf from the Middle Siwalik sediments of eastern Nepal with implication on biogeography and palaeoclimate

The Siwalik flora is important in understanding the orogeny of the Himalayas and the resulting climate change. Though the fossil records from the eastern Himalayan Siwalik of Nepal are sparse, we report a fossil leaf impression/ compression of Ficus precunea Lakhanpal from the Middle Siwalik (upper Miocene–lower Pliocene) sediments of eastern Nepal. The characteristic leaf venation pattern and morphological details suggest its strong affinity with the extant species of F. semicordata Buch.-Ham. ex Sm. The fossil assemblage indicates the presence of seasonal forests during the depositional period in the region.

New insights on the ecology and behavior of Machairodus aphanistus (Carnivora, Felidae, Machairodontinae) through the paleopathological study of the fossil sample from the Late Miocene (Vallesian, MN 10) of Cerro de los Batallones (Torrejón de Velasco, Madrid, Spain)

The Late Miocene natural traps of Cerro de los Batallones (Madrid, Spain) have yielded thousands of fossils of vertebrates, mostly carnivoran mammals such as hyaenids, amphicyonids, ailurids, mustelids, ursids, and felids, especially Batallones-1 and Batallones-3. Among these carnivorans, the tiger-sized saber-toothed felid Machairodus aphanistus was the top predator of the association, and one of the most abundant taxa, represented by thousands of fossils, including several examples of bone pathologies that have never been studied. In this work, we carry out a paleopathological analysis of some of these pathologies from the Batallones sample of this large early machairodontine, with a description of the pathological changes that occurred in the affected bones, a possible diagnosis, and the ethological and ecological consequences of the presence of these diseases in the living animal. The pathological sample of M. aphanistus studied here included a calcaneus and a Mc III from Batallones-1, and a mandible from Batallones-3. The fossils were X-rayed, and their pathologies were described and compared to non-pathological bones. The calcaneus showed a bone callus indicative of osteitis/osteomyelitis or a tumor; the mandible had evidence of the development of an abscess located in the left mandibular body; and the Mc III shows a marked osteosclerosis. These injuries affected the hunting ability of these individuals and gradually weakened them, very likely contributing to their final entrapment in the Batallones cavities, where they were attracted by the presence of previously trapped animals.

Evolution of Arc‐Continent Collision in the Southeastern Margin of the South China Sea: Insight From the Isugod Basin in Central‐Southern Palawan

AbstractThe evolution of arc‐continent collision between the Palawan microcontinental block and the Cagayan Ridge in the southeastern margin of the South China Sea (SCS) is vital to understand how this collision correlated with seafloor spreading of the SCS. To address the evolution of arc‐continent collision, we studied the biostratigraphy and provenance of syn‐collisional sediments in the Isugod Basin in central‐southern Palawan. Microfossil analysis indicates a Late Miocene age (11.5–5.6 Ma) for the Isugod and Alfonso XIII Formations and rapid subsidence during initiation of the basin which may have been triggered by local extensional collapse of the wedge in response to forearc uplift. Multidisciplinary provenance analysis reveals that the Isugod and Alfonso XIII Formations were derived from the Middle Eocene–lower Oligocene Panas‐Pandian Formation on the Palawan wedge and the Late Eocene Central Palawan Ophiolite. These results suggest the emergence of both the orogenic wedge and obducted forearc ophiolite at ∼11.5 Ma, implying collision onset before ∼11.5 Ma. The collision initiation in Palawan could be better constrained to ∼18 Ma, based on the drowning of the Nido carbonate platform in the foreland. Therefore, the gravitational collapse of the Palawan wedge and the subsidence/formation of the Isugod Basin might reflect a significant uplift pulse in the hinterland of the wedge beginning within 13.4–11.5 Ma in the late stage of collision. It indicates that although compression originated from spreading of the SCS had ceased at 16–15 Ma, arc‐continent collision in Palawan did not stop and was sustained by compression from the upper plate afterward.

Stable isotope evidence for resource partitioning in extinct marine carnivores

Living pinnipeds play essential roles in marine ecosystems and display divergent lineage-specific foraging and habitat preferences. The origin of these ecological strategies remains unclear. We analyzed original (n = 22) and published (n = 93) stable carbon (δ13C) and oxygen (δ18O) isotope compositions of tooth enamel from fossil pinnipeds and coeval marine and terrestrial mammals from the late Early Miocene to early Middle Miocene Temblor Formation, the early Middle Miocene Round Mountain Silt Formation at Sharktooth Hill Bonebed, the Middle Miocene of lower levels of the Monterey Formation, and the late Middle Miocene Santa Margarita Formation from the eastern North Pacific Ocean; and original (n = 43) δ13C and δ18O values from the Early Pliocene Yorktown Formation in the western North Atlantic. As expected for aquatic mammals, pinnipeds and control marine mammals had low δ18O variability relative to coeval terrestrial mammals, indicating minimal diagenetic alteration. Among late Early Miocene and Middle Miocene pinnipeds, Allodesmus had lower δ13C values than coeval taxa indicating offshore foraging, in agreement with predictions based on skeletal morphology. However, Allodesmus from the late Middle Miocene Santa Margarita Formation had overlapping δ13C values with co-occurring cetaceans and pinnipeds suggesting preferential nearshore habitat. The stem otariid Pithanotaria had higher enamel δ13C values than co-occurring pinnipeds, indicating nearshore foraging. The stem odobenid Neotherium had intermediate δ13C values supporting foraging between nearshore and offshore predators. Conversely, the stem odobenid cf. Imagotaria had lower enamel δ18O but comparable δ13C values to coexisting pinnipeds, suggesting the exploitation of estuarine resources. At least two ecologically distinct pinniped groups also occurred in the Yorktown Formation. In this unit, the odobenid Ontocetus and some monachinae phocids were predominantly nearshore foragers, with higher enamel δ13C and δ18O values than simultaneously occurring marine mammals. The second group was exclusively composed of phocids, which had comparatively low δ13C and δ18O values, compatible with northward foraging movements along the western North Atlantic coast. The paleoecological profiles of fossils bear strong similarities to the life modes of extant pinniped communities, implying that extant foraging modes appeared early in pinniped evolution and that resource partitioning contributed to their community structure over time.

Phylogeny and historical biogeography of the swallow family (Hirundinidae) inferred from comparisons of thousands of UCE loci

Swallows (Hirundinidae) are a globally distributed family of passerine birds that exhibit remarkable similarity in body shape but tremendous variation in plumage, sociality, nesting behavior, and migratory strategies. As a result, swallow species have become models for empirical behavioral ecology and evolutionary studies, and variation across the Hirundinidae presents an excellent opportunity for comparative analyses of trait evolution. Exploiting this potential requires a comprehensive and well-resolved phylogenetic tree of the family. To address this need, we estimated swallow phylogeny using genetic data from thousands of ultraconserved element (UCE) loci sampled from nearly all recognized swallow species. Maximum likelihood, coalescent-based, and Bayesian approaches yielded a well-resolved phylogenetic tree to the generic level, with minor disagreement among inferences at the species level, which likely reflect ongoing population genetic processes. The UCE data were particularly useful in helping to resolve deep nodes, which previously confounded phylogenetic reconstruction efforts. Divergence time estimates from the improved swallow tree support a Miocene origin of the family, roughly 13 million years ago, with subsequent diversification of major groups in the late Miocene and Pliocene. Our estimates of historical biogeography support the hypothesis that swallows originated in the Afrotropics and have subsequently expanded across the globe, with major in situ diversification in Africa and a secondary major radiation following colonization of the Neotropics. Initial examination of nesting and sociality indicates that the origin of mud nesting – a relatively rare nest construction phenotype in birds – was a major innovation coincident with the origin of a clade giving rise to over 40% of extant swallow diversity. In contrast, transitions between social and solitary nesting appear less important for explaining patterns of diversification among swallows.

How Was the Late Neogene Red Clay Formed in the Ordos Plateau (Northwest China)?

Eolian sediments are extensively distributed across the Earth’s surface, and their formation is intricately linked to climate change, tectonic activity, and topographic features. Consequently, the investigation of eolian sediments bears great geological significance. The northwest region of China is renowned for hosting the most extensive and thickest Late Miocene–Pliocene red clay deposits globally. Nonetheless, scholars have yet to reach a consensus regarding the precise formation processes of these red clays. The identification of the source region of the red clays is crucial for comprehending their formation mechanism. The correlation of zircon U-Pb age spectra is a frequently utilized method for determining the provenance of eolian sediments. In this study, we compared the previously published zircon U-Pb ages (n = 12,918) of the Late Miocene–Pliocene red clays in the Ordos Plateau with those from the potential provenance regions (n = 24,280). The analysis, supported by the tectonic and climatic background of the region, revealed that the Late Miocene–Pliocene red clay in the Ordos Plateau originates predominantly from the Yellow and Wei rivers, with a minor contribution from the weathering of bedrock in the western North China Craton. The transport of these detrital materials by the East Asian winter monsoon is impeded by the presence of the Qinling and Taihang Shan, resulting in their deposition on the flat surface of the Ordos Plateau. This development of red clay is consistent with the proximal accumulation model, illustrating how the hydrosphere, atmosphere, and lithosphere interacted to shape the red clay deposits during the Late Miocene and Pliocene periods in the Ordos Plateau.

Late Oligocene–Miocene evolution of deep-water circulation in the abyssal South China Sea: Insights from Nd isotopes of fossil fish teeth

Abstract A long-term neodymium isotope (εNd) record of fossil fish teeth was investigated to constrain the evolution of deep-water circulation in the abyssal South China Sea (SCS) during the late Oligocene–Miocene (27–10 Ma). Fish teeth samples were collected from the oceanic red beds at International Ocean Discovery Program Expedition 367 Site U1499 (water depth 3758 m). Seawater εNd values (from –7.1 to –4.8, average –6.1) prior to 15 Ma indicate that water masses in the abyssal SCS resulted from the mixing of more radiogenic Upper Circumpolar Deep Water (UCDW, average –4.5) and less radiogenic Lower Circumpolar Deep Water (LCDW, average –6.4). The general decrease in εNd values was attributed to an increasing influence of the unradiogenic LCDW at the studied site, consistent with the subsidence and the associated deepening of the SCS plain. After 15 Ma, seawater εNd dropped significantly to a range of –8.9 to –6.1 (average –7.5), indicating a slowdown in the hydrological connection between the deep-water masses in the SCS and the western Pacific Ocean. We argue that the formation of the Luzon Strait due to the uplift of the Luzon arc in the late Miocene led to the shallowing and narrowing of the SCS-Pacific channels. Consequently, penetration of LCDW was reduced and water masses in the abyssal SCS would have been less ventilated and strongly influenced by lithogenic input from the unradiogenic sediments of large Asian rivers draining the peri-Himalayan region.

Migration and controls of Shenhu submarine canyons in the upper continental slope of northern South China Sea: Insights from three‐dimensional seismic data mapping

AbstractSubmarine canyons, prominent features on continental margins, hold significant scientific and engineering implications. Despite extensive research on various types of submarine canyons, current understanding of those canyons developed on the upper continental slope, recognized as the most common type globally, remains limited. The Shenhu Canyons on the upper continental slope of the northern South China Sea, comprising over 19 subparallel features persistently developed from the Late Miocene to Quaternary, offer an excellent opportunity for in‐depth study. Previous assumptions suggested a unidirectional eastward migration of these canyons parallel to the host margin, primarily based on observations from two‐dimensional transverse seismic profiles. However, this study's analysis using three‐dimensional seismic data mapping reveals that not all canyons have migrated eastward; 28% display an opposite or a zigzag patterned migration, challenging previous assumptions. The eastward migration of the Shenhu Canyons on the eastern slope of the palaeo‐Pearl River shelf‐edge delta can be linked to the south‐east–southward progradation of the host margin and the palaeo‐shelf‐edge delta. However, the overall eastward migration pattern is complicated by submarine landslides and turbidity current processes. Landslides can influence the direction and magnitude of canyon migration through four mechanisms: turbidity current diversion; retrogressive development of canyon‐wall landslides; retrogressive landslides on surrounding open slopes; and emplacement of landslides in canyon thalwegs. These mechanisms may result in widening, bifurcation, confluence or obstruction of canyons, contributing to canyon migration. Erosion by turbidity currents can trigger canyon‐wall failures, which in turn promote the lateral migration of the canyons. If overspilled turbidity currents lead to the growth of levées in the lower reaches, canyon confinement increases, suppressing lateral migration. The inherited high‐gradient Palaeogene syn‐rift tectonic slope, combined with the depositional delta‐front slope of the palaeo‐shelf‐edge delta, creates favourable conditions for the initiation and persistent development of the straight Shenhu Canyons. This comprehensive analysis provides valuable insights into the complex dynamics and factors influencing the migration of upper continental slope submarine canyons.

Radiating diversification and niche conservatism jointly shape the inverse latitudinal diversity gradient of Potentilla L. (Rosaceae)

BackgroundThe latitudinal diversity gradient (LDG), characterized by an increase in species richness from the poles to the equator, is one of the most pervasive biological patterns. However, inverse LDGs, in which species richness peaks in extratropical regions, are also found in some lineages and their causes remain unclear. Here, we test the roles of evolutionary time, diversification rates, and niche conservatism in explaining the inverse LDG of Potentilla (ca. 500 species). We compiled the global distributions of ~ 90% of Potentilla species, and reconstructed a robust phylogenetic framework based on whole-plastome sequences. Next, we analyzed the divergence time, ancestral area, diversification rate, and ancestral niche to investigate the macroevolutionary history of Potentilla.ResultsThe genus originated in the Qinghai-Tibet Plateau during the late Eocene and gradually spread to other regions of the Northern Hemisphere posterior to the late Miocene. Rapid cooling after the late Pliocene promoted the radiating diversification of Potentilla. The polyploidization, as well as some cold-adaptive morphological innovations, enhanced the adaptation of Potentilla species to the cold environment. Ancestral niche reconstruction suggests that Potentilla likely originated in a relatively cool environment. The species richness peaks at approximately 45 °N, a region characterized by high diversification rates, and the environmental conditions are similar to the ancestral climate niche. Evolutionary time was not significantly correlated with species richness in the latitudinal gradient.ConclusionsOur results suggest that the elevated diversification rates in middle latitude regions and the conservatism in thermal niches jointly determined the inverse LDG in Potentilla. This study highlights the importance of integrating evolutionary and ecological approaches to explain the diversity pattern of biological groups on a global scale.

An expanded phylogeny of the genus Pseudamnicola (Gastropoda; Truncatelloidea; Hydrobiidae) across the Mediterranean Basin.

The genus Pseudamnicola Paulucci, 1878, is commonly found throughout the Mediterranean region. The genus displays considerable levels of endemism, accompanied by notable systematic and taxonomic ambiguity. However, the application of molecular data has proven highly effective in clarifying taxonomy and unveiling the diversity of cryptic species within the genus. Therefore, we employed all cytochrome c oxidase subunit I sequence data available and generated new ones from Greece to infer the phylogeny of the genus throughout its Mediterranean range and estimate the divergence times as well as the ancestral area of diversification. Our phylogenetic and time-estimate analyses demonstrate that with 36 to 38 extant Pseudamnicola species and genetic divergences across species ranging from 0.5% to 11.9% on average, the genus underwent relatively recent diversification during late Miocene (6.53 Ma), and the primary speciation events occurred during Plio-Pleistocene. The Italian Peninsula and Islands and the Ionian Drainages as defined by the Freshwater Ecoregions of the World are the ancestral regions of the genus following two different dispersal routes. Our study contributes to deepening our understanding of Pseudamnicola phylogeny by using data from throughout its range for the first time. This phylogeny provides evidence and confirms previous studies that relatively recent habitat isolation, followed by founder and dispersal events, has been one of the primary reasons for the evolution of the genus Pseudamnicola in the Mediterranean basin.

On the last European giraffe,Palaeotragus inexspectatus(Mammalia: Giraffidae); new remains from the Early Pleistocene of Greece and a review of the species

AbstractEurasian Giraffidae went through a drastic biodiversity decline after the Miocene–Pliocene boundary; scanty palaeotragine populations are likely to have survived in Central Asia, providing the necessary stock for a Late Pliocene–Early Pleistocene expansion from Central Asia to Spain and from the Mediterranean to southern Russia. Here, we describe new giraffid findings from the Greek middle Villafranchian faunas of Dafnero-3 and Volax and from the late Villafranchian faunas of Tsiotra Vryssi and Krimni-3, and we revise previous material from Dafnero-1. Our results support the synonymy of almost all the Villafranchian Eurasian giraffids under a single species of Palaeotragus, i.e. Palaeotragus inexspectatus, and allow us to improve its diagnosis. The orientation of the ossicones and the relative shortening of the lower premolar row might indicate affinities to some Late Miocene–Pliocene Palaeotragus from China. Our study suggests that P. inexspectatus was equally abundant at MNQ17 and MNQ18 in the Eastern Mediterranean and that its extinction after MNQ19 was probably attributable to the combination of the climatic and environmental turnover at the Villafranchian–Epivillafranchian boundary, along with the competition with emerging ruminant groups, such as giant cervids. A preliminary analysis of its palaeoecology suggests a giraffid more involved in grazing than its Late Miocene relatives.

Magmatic conditions aiding synconvergent extension above the Peruvian flat slab

Abstract The Cordillera Blanca and Cordillera Huayhuash contain some of the highest topography in the Andes and provide insight into tectonomagmatic processes associated with the onset of flat-slab subduction. These adjacent ranges shared a similar history of deformation and exhumation prior to the late Miocene, when synconvergent extension began in the Cordillera Blanca. Magmatism in the Cordillera Huayhuash has been inferred as coeval with magmatism in the Cordillera Blanca. Yet, extension, which has been correlated with magmatic heat flow, is limited to the Cordillera Blanca. New zircon U-Pb dates and trace and rare earth element concentrations from the Cordillera Blanca batholith and the Huayllapa pluton in the Cordillera Huayhuash and reassessment of existing zircon data help to characterize regional magmatic processes prior to the establishment of flat-slab subduction. Two compositionally distinct samples of the Huayllapa pluton yielded mean ages of 24.8 ± 0.4 Ma and 25.4 ± 0.8 Ma. In contrast, the Cordillera Blanca batholith has a protracted crystallization history postdating that of the Cordillera Huayhuash by up to 20 m.y. Miocene magmatism in the Cordillera Blanca began at 19 Ma and ended with injection of large volumes of geochemically distinct, mantle-derived magma from 10 to 5 Ma. We suggest that 6–5 Ma magmatism in the Cordillera Blanca promoted elevated heat flow and reduced shear strength, which facilitated extensional shearing along the western slopes of the range, whereas colder amagmatic crust in the Cordillera Huayhuash inhibited southward propagation of faulting. Our data demonstrate that the linkages between magmatism and elevated heat flow identified in the Cordillera Blanca are important driving processes in initiating extension in cordilleran-style orogenies.

Comparative Mitogenome of Phylogenetic Relationships and Divergence Time Analysis within Potamanthidae (Insecta: Ephemeroptera).

Potamanthidae belongs to the superfamily Ephemeroidea but has no complete mt genome released in the NCBI (except for two unchecked and one partial mt genome). Since the sister clade to Potamanthidae has always been controversial, we sequenced seven mt genomes of Potamanthidae (two species from Rhoenanthus and five species from Potamanthus) in order to rebuild the phylogenetic relationships of Potamanthidae in this study. The divergence time of Potamanthidae was also investigated by utilizing five fossil calibration points because of the indeterminate origin time. In addition, because Rhoenanthus coreanus and Potamanthus luteus are always in low-temperature environments, we aimed to explore whether these two species were under positive selection at the mt genome level. Amongst the 13 PCGs, CGA was used as the start codon in COX1, whereas other genes conformed to initiating with an ATN start codon. From this analysis, UUA (L), AUU (I), and UUU (F) had the highest usage. Furthermore, the DHU arm was absent in the secondary structure of S1 in all species. By combining the 13 PCGs and 2 rRNAs, we reconstructed the phylogenetic relationship of Potamanthidae within Ephemeroptera. The monophyly of Potamanthidae and the monophyly of Rhoenanthus and Potamanthus were supported in the results. The phylogenetic relationship of Potamanthidae + (Ephemeridae + Polymitarcyidae) was also recovered with a high prior probability. The divergence times of Potamanthidae were traced to be 90.44 Mya (95% HPD, 62.80-121.74 Mya), and the divergence times of Rhoenanthus and Potamanthus originated at approximately 64.77 Mya (95% HPD, 43.82-88.68 Mya), thus belonging to the late Pliocene Epoch or early Miocene Epoch. In addition, the data indicated that R. coreanus was under negative selection and that ATP8 and ND2 in Potamanthidae had a high evolutionary rate.

Integrative approach revealing a species complex in the Neotropical freshwater crab Dilocarcinus septemdentatus (Herbst, 1783) (Decapoda: Trichodactylidae) with a description of a new species

The taxonomic status of the freshwater crab Dilocarcinus septemdentatus (Herbst, 1783) is still not well established. Currently, the main issue involves synonymization with D. spinifer H. Milne Edwards, 1853, based on a variation of the angulation of the gonopod apex. These species are distributed along rivers and lakes in northern South America, with disjunct occurrences in central-west Brazil and Argentina. Due to these inconsistencies, an integrative approach was performed to elucidate these questions, with morphological (including NanoCT-Scan) and molecular analysis (Maximum Likelihood Trees, Bayesian Inference, Genetics Distance Matrix, and Haplotype Network), based on mitochondrial markers COI and 16S rRNA. Both analysis revealed and supported the existence of a species complex under the name of D. septemdentatus. Based on the results obtained, we propose the revalidation of D. spinifer, the description of a new species, and the redescription of D. septemdentatus s. str., with a neotype designation for this species. The hypothesis that this species complex originated in the Pebas System, an extensive mega wetland system that existed along the lowlands of Western Amazonia from late Oligocene to late Miocene (c. 23–11 mya) is discussed.