Eocene Research Articles

Functional and phylogenetic signals in the pectoral girdle of Thalattosuchia and Dyrosauridae (Crocodylomorpha).

Crocodylomorphs have colonized various environments from fully terrestrial to fully aquatic, making it an important clade among archosaurs. A remarkable example of the rich past diversity of Crocodylomorpha Hay, 1930 is the marine colonization undergone by several crocodylomorph lineages, particularly Thalattosuchia Fraas, 1901 during the Early Jurassic-Early Cretaceous, and Dyrosauridae de Stefano, 1903 during the Late Cretaceous-Early Eocene. Thalattosuchia represents the most impressive and singular marine radiation among Crocodylomorpha, occupying various ecological niches, before enigmatically disappearing in the Cretaceous. Dyrosauridae, on the other hand, is known for surviving the end-Cretaceous mass extinction in abundance but subsequently vanished. The evolutionary path undertaken by crocodylomorphs into the aquatic environments and the reasons for their disappearance outside marine extinction events during the Mesozoic remains a mystery. Despite a well-preserved fossil record, attention has primarily centered on craniodental adaptations, overlooking the swimming-related adaptations recorded in the postcranial skeleton. This research primarily involves a comprehensive examination of the pectoral girdle of the most representative members of Thalattosuchia and Dyrosauridae, highlighting their evolutionary trajectories over time. Additionally, this work aims to test the phylogenetic signal residing in the postcranial anatomy of Crocodylomorpha. As such, the most recent and complete Crocodylomorpha phylogenetic dataset has been repurposed: 42 new postcranial characters have been added and several others have been revised to address our phylogenetic question. We stress that postcranial anatomy constitutes an important tool supply to better understand the relations of extinct crocodyliforms, but also offers insights on their development, ecology, and biomechanics.

Physical and chemical properties of soils from different geological formations affecting Tuber melanosporum plantations: a case study in Acqualagna area (central Italy)

Soil properties play a pivotal role in the fructification of the Périgord black truffle (Tuber melanosporum Vittad.). However, the precise manner in which soil composition influences truffle production remains unclear. This study considered three plantation sites located in Acqualagna (central Italy), an important area for the cultivation of black truffles. The sites differed in terms of productivity and geological terrains. Site 1, which produced 4 kg yr−1, was on Schlier sediments (marls and clayey marls; Miocene age), site 2, which yielded 12 kg yr−1, was on alluvial deposits (heterogeneous, mainly sandy gravels and gravels; Holocene age), and site 3 produced 40 kg yr−1 was on Scaglia variegata (alternating marly limestones, calcareous marls, and marls; Eocene age). A total of 62 soil samples were collected and analyzed for their physical, chemical, organic, and mineralogical composition. Among the samples a control area without the presence of truffle was included. The soils composition differed for the content in phyllosilicates and calcite which ranged from 124 to 398 g kg−1 and 98 to 450 g kg−1, respectively. Principal component analysis extracted three factors, accounting for 82% of the total variance. Factor 1 (46.2% of the variance) was strongly and positively correlated with sheet silicates, smectite, clay and negatively with skeleton (fraction > 2 mm). The soils from Scaglia variegata and Schlier clustered around the active carbonate content which was 266 g kg−1 in Scaglia and 250 g kg−1 in Schlier. These soils clustered also for the clay fraction (389 g kg−1 and 428 g kg−1, respectively) as well as for the smectite (268 g kg−1 and 307 g kg−1, respectively). In spite, the soils from alluvial deposits clustered per skeleton (638 g kg−1). In terms of soil productivity, it can be posited that the contribution of the skeleton was always dominant. The carbonate contents allow for the differentiation between intermediate soils (alluvial deposits) and low-productivity soils (Schlier). Additionally, the clay component was found to be high in both low (428 g kg−1) and high productivity soils (389 g kg−1). Conversely, it was low in medium productivity soils (125 g kg−1). The automatic linear modelling (ALM) indicated that among all of the variables considered in this study, six of them were included in the equation and explained 94.3% of the variation in soil classified as suitable for black truffle production. In particular, calcite was identified as the most important predictor variable, followed by available P and K. Regarding the influence of functional groups of humic substances, amide I (1641 cm−1) exerted a positive effect while lignin residues (1510 cm−1) had a negative one. The findings of this study may assist in the selection of optimal soils for black truffle cultivation.

Spatiotemporal changes in riverine input into the Eocene North Sea revealed by strontium isotope and barium analysis of bivalve shells

Reconstructing hydrological conditions of past warm periods, such as the Eocene ‘hot house’ provides empirical data to compare to state of the art climate models. However, reconstructing these changes in deep time is challenging, for example, given the complex interplay between evapotranspiration, precipitation and runoff. As a proxy for past changes in these hydrological systems, the dynamics of fresh water input into marginal seas can be used to identify the spatiotemporal distribution of riverine runoff. Elemental barium (Ba) and radiogenic strontium (87Sr) are, depending on the amount of runoff and the background geology of the catchment area, typically enriched in river waters in comparison to seawater and can thus be utilized to determine changes in riverine fresh water discharge. Here, we use barium to calcium ratios (Ba/Ca) and radiogenic strontium isotopes (87Sr/86Sr) measured in fossil bivalve shells to reconstruct patterns of fresh water input into the paleo North Sea during the early to middle Eocene. Our reconstruction shows the potential of Ba/Ca and 87Sr/86Sr to serve as proxies for riverine runoff and highlights the spatiotemporal complexity of Eocene hydrological conditions in western Europe. In particular, our results enable changes in riverine input along geological to perennial time scales for different coastal regions to be determined, revealing a steady influx of fresh water, but with distinct spatiotemporal differences.

A new species of Hemerobiidae (Neuroptera) from the late Eocene Rovno amber

Proneuronema damzeni sp. nov. (Neuroptera: Hemerobiidae) is described from late Eocene Ukrainian Rovno amber. It differs from the two other species of this Eocene genus by a combination of the following character states: forewing larger (7.3 mm long in the new species; 6.3–6.9 mm in P. minor Makarkin et al., 2016; 5.9 mm in P. sydorchukae Makarkin & Perkovsky, 2020) and broader (length to width ratio is 2.14 in the new species; 2.46 in P. sydorchukae; 2.17–2.30 in P. minor), and different forewing maculation (one spot at the third (‘inner’) gradate series in the new species; two in P. sydorchukae; none in P. minor). The Fur Formation Megalomus densistriatus Henriksen, 1922 and the Baltic amber Proneuronema gradatum Makarkin et al., 2016 are preliminary assigned to Archibaldia Makarkin, 2023 as Archibaldia densistriata, comb. nov. and A. gradata, comb. nov., respectively. The species composition and distribution of Proneuronema and Archibaldia are briefly discussed.

Phylogenomic insights into species relationships, reticulate evolution, and biogeographic diversification of the ginseng genus Panax (Araliaceae), with an emphasis on the diversification in the Himalayan‐Hengduan Mountains

AbstractPanax (Araliaceae) is a small genus containing several well known medicinally important species. It has a disjunct distribution between Eastern Asia and Eastern North America, with most species from eastern Asia, especially the Himalayan‐Hengduan Mountains (HHM). This study used the genomic target enrichment method to obtain 358 nuclear ortholog loci and complete plastome sequences from 59 accessions representing all 18 species of the genus. Divergence time estimation and biogeographic analyses suggest that Panax was probably widely distributed from North America to Asia during the middle Eocene. During the late Eocene to Oligocene Panax may have experienced extensive extinctions during global climate cooling. It survived and diverged early in the mountains of Southwest China and tropical Indochina, where some taxa migrated northwestward to the HHM, eastward to central and eastern China, and then onward toward Japan and North America. Gene flow is identified as the main contributor to phylogenetic discordance (33.46%) within Panax. We hypothesize that the common ancestors of the medicinally important P. ginseng + P. japonicus + P. quinquefolius clade had experienced allopolyploidization, which increased adaptability to cooler and drier environments. During the middle to late Miocene, several dispersals occurred from the region of the HHM to contiguous areas, suggesting that HHM acted as a refugium and also served as a secondary diversification center for Panax. Our findings highlight that the interplay of orographic uplift and climatic changes in the HHM greatly contributed to the species diversity of Panax.

Carbon, iron and sulfur records of lacustrine paleo-environments during the middle Eocene in eastern China

It is widely recognized that anoxic conditions facilitate the preservation of organic carbon in marine sediments. However, the specific geological factors that lead to the development of such conditions in paleo-lakes are less well understood. Owing to their smaller size, paleolakes could experience more frequent and stronger changes in geochemical conditions than oceans. Such changes, such as volcanism, hydrothermal fluids, or ocean transgressions, can also strongly affect the lacustrine organic carbon burial thereby complicating sediment diagenesis record. Here, we used total organic carbon content (TOC), organic carbon isotope (δ13Corg), iron speciation, and pyrite sulfur isotope (δ34Spy) data to establish relationships between organic carbon preservation and anoxic conditions in fine-grained sediments from the middle Eocene lacustrine depositional environments from the Shahejie Formation of the Jiyang Depression, Bohai Bay Basin, eastern China. The results reveal TOC between 1 % and 10 %, highly-reactive iron to total iron ratios >0.38, and most TOC to total sulfur ratios exceeding 2. These data indicate that the organic-rich shales of the Shahejie Formation were formed as a result of high primary productivity during the warm and humid middle Eocene period, coupled with the efficient preservation of organic matter in anoxic bottom waters. Negative δ13Corg and δ34Spy excursions recorded in the Shahejie Formation indicate water column conditions to have been influenced by transient volcanic eruptions. Positive δ13Corg and negative δ34Spy excursions may have been caused by hydrothermal fluids input whereas δ34Spy values approaching 20 ‰ suggest frequent marine transgressions. In particular, despite potential inputs of S into the paleolake by volcanism, hydrothermal fluids, or marine transgressions, bacterial sulfate reduction efficiently depleted the sulfate pool to have created ferruginous geochemistry water conditions for the effective preservation of organic carbon in sediments. Our results establish a direct link between lacustrine shale geochemical signatures and geological phenomena that impact its sedimentation.

Cenozoic surface Earth system evolution and dynamic paleogeomorphic reconstruction from the Tibet Plateau to the Western Pacific linked by the Yangtze River

The formation of the modern east-flowing Yangtze River is marked by the incision of the Three Gorges (TG) between the Sichuan and Jianghan basins. However, it is still controversial on the timing of the TG incision, due to diverse tectonic, sedimentological and geochemical records. These records, together with other geological data, i.e. curves of paleo-climate and sea level fluctuation, are critical parameters in the software Badlands , a tool to simulate large-scale and long-term geomorphic evolution. Using Badlands , we modeled the geomorphology and drainage evolutionary process of the Yangtze River since the Late Cretaceous (80 Ma). It revealed that the drainage system in the Sichuan Basin was gradually reversed from southward flowing to northward flowing during the Late Eocene and the Oligocene, due to the periodic uplift of the eastern Tibet Plateau and the southwestern Yangtze Block. Coevally, the Jianghan Basin experienced a base level drop, controlled by the collapse of a paleo-coastal mountain range and the subsequent continental rifting along the Southeast China continental margin. The tectono-geomorphic interplay eventually led to the incision of the TG at the Late Oligocene (about 24Ma), when the drainage system of the Upper Yangtze River was captured by the Middle-Lower Yangtze River.

A reappraisal of Mesozoic-Cenozoic sequence stratigraphy in Offshore Indus Basin, Pakistan

The Offshore Indus Basin is a passive continental margin and a frontier zone for hydrocarbon exploration based on structural and stratigraphic features observed on seismic data. In this study, the seismic and biostratigraphic framework is established using seismic data, geophysical well logs, along with biostratigraphic information to define the depositional sequences in the study region. A re-examination of the seismic data exhibits normal faults and a total of six seismic sequences ranging from Cretaceous to Quaternary. Nummulites atacicus, Nummulites globulus, Discocyclina sp., Miscellanea miscella, and Ranikothalia sp. are the major identified fauna in the Karachi South A1 well (2030–2724 m). The Miscellanea miscella, Ranikothalia, and Discocyclina sp. ages range from 55 to 56.5, 55–59, and 55–59 Ma respectively. Employing biostratigraphy, Ranikothalia/Miscellanea miscella/Discocyclina biozone (55–59 Ma), a single sequence, a third order cycle of deposition and transgressive and highstand system tracts have been recognized in the Karachi South A1 well. Linking biostratigraphic results to seismic stratigraphy indicates that the strata located in the range of 2030–2724 m is of the Ranikot (Paleocene) Formation and has been previously given Eocene age rather than the Paleocene using vintage seismic data. The environment of deposition of the Ranikot Formation in the Karachi South A1 well is the subtidal environment of the middle-shelf (30–45m depth) setting.

The Phylogeography and Diversification of an Endemic Trapdoor Spider Genus, Stasimopus Simon 1892 (Araneae, Mygalomorphae, Stasimopidae) in the Karoo, South Africa.

The genus Stasimopus is endemic to South Africa but has never undergone a phylogeographic review. This study aims to unravel the phylogeographic patterns and history of the many Stasimopus species which occur in the greater Karoo region. A fossil-calibrated phylogeny was produced based on three gene regions (CO1, 16S and EF-1ɣ) for Stasimopus (Cor-k-lid trapdoor spiders) specimens collected in the Karoo region, to infer dates of origin and diversification. Demographic analyses were performed on species with sufficient sample sizes (> 4). Haplotype networks were constructed for each gene region and plotted on a map to infer phylogeographic patterns. Lastly, Mantel tests were performed to test for isolation by distance. It was found that 15 species occur in the Karoo and that the genus radiation in the area is in the early Palaeocene. Most diversification occurred between the late Eocene and the Miocene, coinciding with significant changes in climate. Several species show signals of demographic expansions. Isolation by distance was detected, but only with a slight correlation. It is apparent that aridification has played a vital role in the diversification of the genus in the Karoo region. This is a shared biogeographic influence between the mygalomorph fauna of the Karoo and arid region of western Australia. Stasimopus has radiated from the late Eocene and through the Miocene resulting in 15 extant species in the region. The Tankwa Karoo has been identified as a possible Pleistocene glacial cycle refugia for the species S. leipoldti. Many of the species in the Karoo are short-range endemics, making them of high conservation concern. This study provided vital information as the Karoo is undergoing further desertification due to factors such as climate change, which may affect the future of short-range endemic spiders.

Species Diversity, Host Association, and Evolutionary History of Cronartium: An Important Global Fungal Pathogen to Trees.

Pine stem rust, the most damaging and widespread forest disease occurring in pine trees in the Northern Hemisphere, is primarily caused by Cronartium species (Pucciniales, Melampsorineae). While the phylogenetic relationships of major Cronartium species have been largely elucidated, there is limited understanding of their species diversity and the evolutionary processes shaping their distribution patterns. In this work, we performed broad sampling and sequencing of Cronartium taxa in China together with additional sequence data and other accessions in NCBI to investigate the diversification and to estimate the divergence time of major evolutionary events in this genus. Molecular dating analysis suggested that the divergence of the genus Cronartium probably was around 91.78 Ma during the Upper Cretaceous. It is believed that Cronartium species may have originated in Asia and North America, with intercontinental dispersals occurring primarily during the Middle Eocene, Middle Miocene, and Pliocene. These dispersal events likely took place through the North Atlantic Land Bridge, the De Geer Route, and the Bering Land Bridge, and subsequently diverged through sporadic dispersal and vicariance events. Furthermore, our analysis of host associations revealed that the diversification of Cronartium species was correlated with their telial-hosts, and some species may have experienced host jump events, indicating a complex interplay between host specificity and pathogen-host interaction during Cronartium evolution.

Rhodolith Beds in a Shifting World: A Palaeontological Perspective

ABSTRACTThe occurrence of rhodolith beds in the stratigraphic record from the Cretaceous to the Pleistocene was analysed from published papers. Most data refer to low–mid latitude records of rhodolith beds described in the Tethyan–Paratethyan–Mediterranean domain. The first putative rhodolith beds are from Albian (uppermost Lower Cretaceous) deposits. These rhodolith beds are made up mostly of unattached loose branching corallines as well as of nodular structures. From the Coniacian (Upper Cretaceous) to the Langhian (Middle Miocene), abundance of rhodolith beds shows a generally increasing fluctuating trend with two significant expansions in the Priabonian (late Eocene) and during the Aquitanian–Langhian (Early‐Middle Miocene). After the Langhian maximum, rhodolith beds sharply declined to a minimum in the Zanclean (Early Pliocene). During the Pleistocene, they recovered to values similar to those reached in the Langhian. The general increase in rhodolith beds up the Langhian maximum correlates well with global temperature and pCO2 declines and with an ocean pH increase. The tectonic activity leading to important palaeogeographic changes in the Tethyan–Parathetyan–Mediterranean realm might account for the Serravallian–Zanclean downfall of rhodolith‐dominated deposits. The Cretaceous–Pleistocene record of rhodolith beds shows that these ecosystems withstood successfully a highly changing world. The rapid acclimation of particular taxa to environmental changes and the variable reaction of taxa distributed at different water depths can be crucial to understand their success. In this regard, it would be interesting to analyse how different taxa in modern deep rhodolith beds respond to changing oceanic conditions.

The Segmented Multi‐Source Sediment Routing System on the Hangingwall Dipslope of the Xihu Depression, East China Sea Shelf Basin: Insights From Palaeogeomorphology, U–Pb Ages and Heavy Minerals

ABSTRACTCoeval input systems in rift basins may interact with each other to form a segmented multi‐source sediment routing system. Importantly, its division into proximal zones, where a single source dominates, and interaction zones, where multiple sources mix, enables the interactions between input systems to be characterised. Here, we exploit this conceptual framework to revisit the middle Eocene–early Oligocene hangingwall dipslope of the Xihu depression in the East China Sea Shelf Basin, where extensive 3D seismic data, detrital zircon U–Pb ages and heavy mineral compositions are available. We first combined palaeogeomorphological and sedimentological features with age signatures to distinguish three areas: the northwestern area was identified for its proximity to the Haijiao uplift and invariably high proportions of Palaeoproterozoic ages (41%–54%); the southwestern area adjacent to the Yushan uplift was distinct for enriched Cretaceous‐aged zircons (36%) and the transition area in between was characterised by its remoteness to both uplifts, an embayed geometry and mixed age signatures that are not identical to any individual input. These spatial variations support the segmented framework for the multi‐source system, with the northwestern and southwestern areas representing two palaeo‐input systems and the transition area as their interaction zone. In this context, we then used mixture models to determine spatio‐temporal variations in the mixing proportions of the two palaeo‐input systems. The zircon‐based results indicate that the mixing proportion sustained from the middle to the late Eocene, during which the basin was in the late syn‐rift stage and marine environments. This is corroborated by heavy mineral composition that shows only minor changes. We interpret the roughly sustained mixing proportions as reflecting both the spatially uniform nature of broad subsidence and the strong tidal processes that ‘erased’ the effects of avulsions. In contrast, a clear provenance shift in both zircon ages and heavy minerals occurred from the late Eocene to the early Oligocene, coinciding with a transition to the tectonic inversion stage and a shift towards non‐marine environments. The provenance shift, together with the southward expansion of the axial drainage, likely represents the sedimentary response to the southward decreasing inversion magnitude of the Yuquan Event. In addition, we hypothesize that in the absence of strong tides, avulsions might have controlled the mixing proportion, particularly over short timescales. Ultimately, this study demonstrates the segmented multi‐source framework, if properly incorporated, can provide key insights into dipslope sedimentation.

The first fossil chylizine fly (Diptera: Psilidae) with a discussion on the ages of related fossil Acalyptratae

Abstract The first fossil rust fly (Diptera: Psilidae) from the Insect Bed of the Bembridge Marls of the Isle of Wight is also the first known fossil record of the subfamily Chylizinae. It is late Eocene: Priabonian in age, 34.2 Ma. Chyliza colenutti Ross, Zhou, Hoffeins & Crighton, sp. nov. is compared with 30 extant species of Chyliza and differs from them in having a relatively long 2nd basal cell compared to the discal cell. Some other fossil Acalyptratae records are reviewed and their probable ages updated. The phylogenetic position of the Psilidae is currently uncertain so the family may have appeared anytime from 70–40 million years ago.

Phylogeny, Diversification, and Biogeography of Garra (Cypriniformes: Cyprinidae) Reveals Multiple Cross-Drainage Dispersals in Southeast Asia.

Garra, a kind of small- to medium-sized fish, is widely distributed from southern Eurasia to central Africa. As one of the most diverse genera of Cyprinidae, investigating the phylogeny and biogeography of Garra remains challenging. In this study, we combined sequences of Garra samples collected from Myanmar with sequences downloaded from GenBank to investigate the phylogeny, diversification, and biogeography of Garra on a global scale, with an emphasis on Southeast Asia. Species delimitation results indicated that there are at least 22 potential species, including eight undescribed species in Myanmar, suggesting that the diversity of Garra in this region have been largely underestimated. Diversification analysis suggested a relatively high diversification rate in the early branches of Garra. Ancestral distribution reconstruction results revealed that Garra originated from the Irrawaddy River basin in the late Eocene, approximately 34 million years ago, with subsequent dispersals across different drainages influenced by the uplift of the Qinghai-Tibet Plateau. Our study provided a new insight into the evolutionary history of Garra and the basis for further research on this genus.

Eocene Shark Teeth From Peninsular Antarctica: Windows to Habitat Use and Paleoceanography

AbstractEocene climate cooling, driven by the falling pCO2 and tectonic changes in the Southern Ocean, impacted marine ecosystems. Sharks in high‐latitude oceans, sensitive to these changes, offer insights into both environmental shifts and biological responses, yet few paleoecological studies exist. The Middle‐to‐Late Eocene units on Seymour Island, Antarctica, provide a rich, diverse fossil record, including sharks. We analyzed the oxygen isotope composition of phosphate from shark tooth bioapatite (δ18Op) and compared our results to co‐occurring bivalves and predictions from an isotope‐enabled global climate model to investigate habitat use and environmental conditions. Bulk δ18Op values (mean 22.0 ± 1.3‰) show no significant changes through the Eocene. Furthermore, the variation in bulk δ18Op values often exceeds that in simulated seasonal and regional values. Pelagic and benthic sharks exhibit similar δ18Op values across units but are offset relative to bivalve and modeled values. Some taxa suggest movements into warmer or more brackish waters (e.g., Striatolamia, Carcharias) or deeper, colder waters (e.g., Pristiophorus). Taxa like Raja and Squalus display no shift, tracking local conditions in Seymour Island. The lack of difference in δ18Op values between pelagic and benthic sharks in the Late Eocene could suggest a poorly stratified water column, inconsistent with a fully opened Drake Passage. Our findings demonstrate that shark tooth bioapatite tracks the preferred habitat conditions for individual taxa rather than recording environmental conditions where they are found. A lack of secular variation in δ18Op values says more about species ecology than the absence of regional or global environmental changes.

In-situ zircon and cassiterite LA-ICP-MS geochronology and implications for granite-hosted Sn deposit models and exploration: Insights from the Cameroon Line

Abstract Tin mineralization of significant economic importance occurs across the continental portion of the Cameroon Line (CL). Tin deposits therein occur as both primary and secondary (residual and alluvial) ore. Though the temporal and, by inference, the genetic link between Sn mineralization and the host granite had long been modeled and widely accepted worldwide, in the CL, however, the age of the granite hosting cassiterite is poorly constrained, preventing a robust assessment of the temporal and genetic relationship between the Sn mineralization and its host rock. Here, we present in-situ zircon and cassiterite laser ablation inductively coupled mass spectrometry (LA-ICP-MS) U-Pb data in order not only to constrain the age of the granitic rock hosting the primary Sn ore but also to bracket the time frame of Sn mineralization, with respect to the magmatic-hydrothermal evolution of the parental magma of the host granite. Zircon from two greisen-altered, cassiterite-bearing granite samples yield overlapping and concordant ages of 64.21 ± 0.59 Ma and 65.46 ± 0.95 Ma, respectively, which are also overlapping with regional granite magmatism in the CL (ca. 65–30 Ma). On the other hand, cassiterite, which is spatially associated with the Paleocene zircon, yields Lower Eocene ages of 54.99 ± 0.35 Ma and 56.08 ± 0.46 Ma. The ca. 10 Myr time gap between zircon and cassiterite suggests that the granite is a passive host not genetically related to the Sn mineralization, which may be linked to a younger, concealed intrusion of ca. 55 Ma. This finding contrasts with the most widely accepted petrogenetic model of tin granite, according to which Sn mineralization and the host granite are cogenetic.

The Evolution of Powell Basin (Antarctica)

Powell Basin is an ocean basin formed as a result of the Scotia Sea evolution. The existing tectonic models propose a variety of starting and ending ages for the spreading of the basin based on seafloor magnetic anomalies. Here, we use recent magnetic field data obtained from eight magnetic profiles in Powell Basin to provide insights into the oceanic spreading evolution. The differences found between the number of anomalies on both sides of the axis and the asymmetry in the spreading rates suggest different opening models for different parts of the basin. We propose a spreading model starting in the late Eocene (38.08 Ma) and ending in the early Miocene (21.8 Ma) for the northern part of Powell Basin. For the southern part, the opening started in the late Eocene (38.08 Ma) and ended in the middle Paleogene (25.2 Ma). The magnetic data have been combined with gravity and sediment thickness data to better constrain the age models. The gravity and sediment thickness information allow us to more accurately locate the position of the extinct spreading axis. Geothermal heat flow measurements are used to understand the relationship between the low amplitudes of the magnetic anomalies and the heat beneath them. Our proposed oceanic spreading models suggest that the initial incursions of the Pacific mantle outflow into the Powell Basin occurred in the Oligocene, and the initial incursions of oceanic currents from the Weddell Sea occurred in the Eocene.

The fossil record of female sexual ornamentation in Empididae (Diptera: Empidoidea), with description of four new species

Females of the subfamily Empidinae (Diptera: Empididae s.s.) often exhibit sexual ornamentation, an adaptation that, within the animal world at large, is most often associated with males, especially in vertebrates. Ornaments of female Empidinae include: 1) legs with rows of relatively large pennate scales, 2) enlarged and/or darkly pigmented wings and 3) inflated abdominal sacs. Ornamentation makes the females appear larger, a characteristic that may make them appear, albeit deceptively, more fecund, and therefore more attractive to potential mates. Given the rarity of female sexual ornamentation, these flies, particularly those of the tribe Empidini, have become a model system for study of this phenomenon. The family’s fossil record consists of 111 known occurrences including several genera from the middle Jurassic. This fossil record however is dominated by two genera, Empis and Rhamphomyia, which account for nearly 60% of all fossil occurrences. Unfortunately, there has been no fossil record of empidine sexual ornamentation other than pennate leg scales. Herein, we review this fossil record and describe the first empidine fossils, all from the Middle Eocene Kishenehn Formation, with enlarged and/or darkly pigmented wings, Rhamphomyia kitadai sp. nov. and R. brunnipennis sp. nov., and two new species of Rhamphomyia which display pennate leg scales, R. decens sp. nov. and R. pennipes sp. nov. Rhamphomyia enena Cockerell, 1921, the oldest known fossil that exhibits pennate leg scales, is redescribed.

New species of braconid parasitoid wasps from the subfamilies Doryctinae and Brachistinae from late Eocene Baltic amber

Three new fossil species of braconid wasps are described and illustrated from late Eocene Baltic amber: Palaeorhoptrocentrus tenuicornis sp. nov. (Doryctinae), Taphaeus obscurus sp. nov. (Brachistinae: Diospilini), and Eubazus electrus sp. nov. (Brachistinae: Brachistini). Keys to the known species of Palaeorhoptrocentrus Belokobylskij, 2023 and to species of Eubazus Nees, 1812 described from Baltic amber are provided. An illustrated redescription of Blacus (Electroblacus) facialis Brues, 1933 (Brachistinae: Blacini) is also provided, along with digital photographs for the first time of the female of B. (Electroblacus) facialis, whose type material was lost during the World War II. We also provide morphological notes and digital photographs of a male belonging to an undescribed species of Meteorus (Euphorinae).

Paleomagnetic Data Bearing on the Origin of the Supra‐ Subduction Zone Ophiolites in Southeast Anatolia and the Progressive Closure of the Neotethys Ocean in the Eastern Mediterranean

AbstractThe Late Cretaceous supra‐subduction zone (SSZ) ophiolites in SE Anatolia form two parallel belts: the northern ophiolitic belt, which was emplaced onto the Tauride platform and a second southern belt emplaced on the Arabian platform. There are controversial hypotheses about the geometry and tectonic process of these ophiolites, which are still not well understood. Here, we test three alternative tectonic models for; (a) One single ocean which is defined by the İzmir‐Ankara‐Erzincan Ocean; (b) A southern branch of the Neotethys Ocean; (c) Two separate oceanic basins, which are the Berit Ocean and the South Neotethys Ocean. We present paleomagnetic results from 161 sites focusing on the sheeted dyke complex, cumulate gabbros, extrusive and sedimentary sequences of the Upper Cretaceous ophiolites in the SE Anatolian region. We also sampled the unconformable cover units from Middle Eocene and Miocene sedimentary rocks to distinguish emplacement related tectonic rotations from post‐emplacement tectonic rotations. Our data indicate that the southern ophiolites (Hatay ophiolite, cumulate gabbro + lava) were formed at a paleolatitude of and those of the northern ophiolites (Göksun, İspendere, Guleman ophiolite, cumulate gabbro + lava) were formed at a paleolatitude of . We hypothesize that the northern ophiolites were derived from the Ocean in a NW‐SE directed subduction zone between the Taurides and the Bitlis Pütürge massif, while the southern ophiolites, in contrast, were formed in the South Neotethys Ocean in a NNW‐SSE directed subduction zone farther northeast of the Taurides. Both the ophiolites reached their present position during Late Cretaceous to Middle Miocene, affected by rigid‐block rotations almost in counterclockwise sense.