Fossil Sites Research Articles

CSI (Crime Scene Investigation) Beagle: Darwin's contribution to taphonomy

In the last decades, the impact of Darwin's legacy has been emphasized in many scientific fields. Nevertheless, there are still lesser-explored aspects of his life as researcher that deserve attention, such as his role as taphonomist. In this context, we highlight here this relevant facet of Darwin's investigations. During his voyage on the H.M.S. Beagle, Darwin collected numerous vertebrate fossils from South America. Particularly, in the Argentine Pampas he recorded information on the paleontology, stratigraphy, and sedimentology of different late Cenozoic fossiliferous sites. He also made observations on the preservation features of bone remains and the mechanisms that favored their fossilization, aspects currently included in the taphonomy field. In this frame, the information published in Geological Observations on South America regarding the fossils from Monte Hermoso and Punta Alta sites and his comments about the “imperfection of the geological record” on the Origin of the Species, are particularly noteworthy as an indicator of his interest in the relationship between the environmental context of preservation and the taphonomic features of bone remains. After 150 years, his scientific work continues to fascinate us. Darwin's keen eye for detail and his curiosity about the history of each fossil, about a century before taphonomy was born as a discipline, can indeed be likened to that of a Crime Scene Investigator (CSI) in some regards, reconstructing the taphonomic histories of both single remains and whole assemblages.

A new foliicolous fossil-species of Asterina Lév. (Asterinaceae; Asterinales) associated with Calophyllum L. from the Siwalik of Eastern Himalaya and its implications

The present study reports and describes a new foliicolous fossil-species of Asterina Lév. (Asterinaceae: Asterinales: Dothideomycetes) namely, A. siwalika sp. nov., on a compressed leaf assigned to modern Calophyllum L. (Calophyllaceae) recovered from the Siwalik sediments (early Miocene to Pliocene: Chunabati Formation) of Darjeeling, Eastern Himalaya. This epifoliar Siwalik fungal species is characterized by a dark brown, sub-dense mycelial mat; septate, branched, superficial, oppositely arranged hyphae with one to two-celled, alternate to oppositely arranged appressoria; flattened, circular, non-ostiolate thyriothecia, scutellum with radially arranged isodiametric to cylindrical cells; and bi-celled, one-septate, conglobate to ellipsoidal, striated ascospores. Here, we reconstruct for the first time a possible sexual life cycle of A. siwalika. The in-situ occurrence of Asterina on Calophyllum leaf cuticles suggests a warm and humid tropical climate and a possible host-parasitic relationship that might have existed in the ancient forest of the Darjeeling sub-Himalaya region during the time of deposition. The conclusion is supported by published qualitative and quantitative climatic data using plant megafossils recovered from the same fossil locality.

Origin and significance of macroscopic organic aggregates from the lacustrine Aptian Crato Konservat-Lagerstätte

The Crato Konservat-Lagerstätte is one of the main Mesozoic fossil sites from Gondwana, recording a wide diversity of terrestrial and non-marine aquatic fossils of great paleobiological and evolutionary significance. This conservation deposit is recorded in a 9 m-thick interval of laminite, microbialite, and grainstone deposited in a lake system with variable water level, alternating moments of hypersaline and freshwater conditions. Despite numerous studies describing new species of plants, arthropods, fish, pterosaurs, birds, and many others, there remains a significant gap in our understanding of the most common and archetypal fossils, which are the rod-shaped macrofossils found on bedding surfaces in distinct stratigraphic intervals of the Crato Konservat-Lagerstätte. The rod-shaped macrofossils are up to 1.6 cm-long and 0.1 cm-wide, straight to curved compressions that preserve pyritized microfossils. Here we interpret the rod-shaped macrofossils as macroscopic organic aggregates that sank into the lakebed in a process called lake snow. During high organic productivity periods in the epilimnion, planktonic organisms thrived and produced exopolymers responsible for aggregation. Their concentrations in the limestone bedding planes reflect intensity of lake snow and environmental seasonality. Aggregates are prolate particles that are commonly oriented, suggesting their transport as bedload for short distances, which was facilitated by biostabilization by microbes and their exopolymers. Finally, pyritization was mediated by microbial communities living in the lakebed.

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

Flying squirrels are important forest environment indicators. There have been many reports on them from fossil localities of the Late Cenozoic in southwest China, but relatively few detailed studies have been carried out on them. Numerous flying squirrel fossils of the Mid-Late Pleistocene were unearthed from the Yumidong Cave in Wushan County, Chongqing Municipality, China, providing excellent materials for morphological comparison and further research on this group. Four species have been recognised from this locality, including Pteromys volans, Trogopterus xanthipes, Belomys pearsonii and Aeretes melanopterus. P. volans and A. melanopterus are Palearctic species, which adapted to the cold environment and had been completely extinct in the study area since the Holocene Megathermal period. Based on the analyses of paleozoogeography and paleoecology of these four species, it could be concluded that the Yumidong Cave area was dominated by subalpine evergreen coniferous forest or coniferous and broad-leaved mixed forest during MIS 2 and MIS 4 periods, which were colder and had more coniferous forest than now, while the vegetation landscape of MIS 3 and MIS 5 periods were similar to that of nowadays.

High-resolution UAV maps of the Gobi Desert provide new insights into the Upper Cretaceous of Mongolia

The Gobi Desert of southern Mongolia is home to an incredibly rich record of dinosaurs and other vertebrate fossils from the latest Cretaceous Period. Together, more than a dozen sites in several basins have produced one of the richest palaeofaunas known from this interval anywhere in the world. Most of this diversity has been recovered from the fluvial deposits of the Nemegt Formation. Despite historic and ongoing research in southern Mongolia, accurate maps and geological data for the main fossil sites are still lacking, limiting our ability to investigate how local palaeoecological dynamics influenced Nemegt taxa, their geographic distribution, and their evolutionary patterns. One of these sites, Guriliin Tsav, has produced more than a hundred significant fossil specimens to date, but still remains one of the lesser known Nemegt localities. In part this is because many expeditions have instead focused on the nearby Bügiin Tsav, one of the largest and richest localities for the Nemegt Formation. To address this gap, a project was initiated in 2018 to produce a high-resolution topographic map of Guriliin Tsav using Unmanned Aerial Vehicles (UAV), and consequently, to plot the geographic and stratigraphic distributions of palaeontological resources on this map. In so doing, we also collected stratigraphic and taphonomic data from the area, allowing for the first detailed palaeoecological interpretation of Guriliin Tsav and a comparison with other localities of southern Mongolia. Here we present the results of this project, and also discuss new topographic and stratigraphic data from Bügiin Tsav. This sheds new light into the temporal and geographic distribution of vertebrate taxa in the latest Cretaceous of Mongolia.

A new species of a snapping turtle (Pan-Chelydridae/Chelydropsis) from the Upper Miocene (MN9, early Vallesian) of Southwest Germany

ABSTRACT Chelydropsis is a genus of the clade Pan-Chelydridae, which existed and was distributed in Eurasia from the Eocene to the end of the Pliocene. The Chelydropsis fossil record of North of the Alps is particularly rich throughout the Miocene. In this study, we describe a new Chelydropsis species from the Late Miocene (Vallesian, MN9) fossiliferous site of Höwenegg in southwestern Germany. The new species is based on a nearly complete Chelydropsis skeleton, which stands out among the best preserved and most complete specimens ever found until now. The new species, Chelydropsis heweneggensis sp. nov. is of particular importance. It differs from the coeval Chelydropsis murchisoni, which recent studies suggest is the only Chelydropsis species known to have existed in Europe from the Middle Miocene to the Pliocene. The species described herein thus adds to the diversity of the European Neogene Chelydropsis record.

Disparate occurrences of a chalicotheriine and a schizotheriine chalicothere (Mammalia, Chalicotheriidae) at the Late Miocene hominid locality Hammerschmiede (Germany)

Chalicotheres are enigmatic perissodactyls that had large claws instead of hooves. The present study concerns the material of Chalicotheriidae from the Late Miocene hominid locality of Hammerschmiede in Germany. The HAM 5 fossil site (11.62 Ma) consists of six isolated dental and postcranial chalicothere elements. Based on the morphology and dimensions of the dentition, the material can be assigned to the chalicotheriine Anisodon sp. This genus is the most common representative of Chalicotheriidae in Central Europe during the Middle Miocene but becomes much rarer during the Late Miocene. The HAM 4 fossil site (11.44 Ma) has yielded a patella belonging to a schizotheriine and a skull fragment that could possibly also belong to a schizotheriine. Thus, the schizotheriine and the chalicotheriine occur in different horizons in Hammerschmiede. Both taxa probably had a rather similar diet but different locomotion, and their disparate occurrences are most plausibly associated with environmental differences among the two fossiliferous levels.

Palms of the past: can morphometric phytolith analysis inform deep time evolution and palaeoecology of Arecaceae?

Palm fossils are often used as evidence for warm and wet palaeoenvironments, reflecting the affinities of most modern palms. However, several extant palm lineages tolerate cool and/or arid climates, making a clear understanding of the taxonomic composition of ancient palm communities important for reliable palaeoenvironmental inference. However, taxonomically identifiable palm fossils are rare and often confined to specific facies. Although the resolution of taxonomic information they provide remains unclear, phytoliths (microscopic silica bodies) provide a possible solution because of their high preservation potential under conditions where other plant fossils are scarce. We thus evaluate the taxonomic and palaeoenvironmental utility of palm phytoliths. We quantified phytolith morphology of 97 modern palm and other monocot species. Using this dataset, we tested the ability of five common discriminant methods to identify nine major palm clades. We then compiled a dataset of species' climate preferences and tested if they were correlated with phytolith morphology using a phylogenetic comparative approach. Finally, we reconstructed palm communities and palaeoenvironmental conditions at six fossil sites. Best-performing models correctly identified phytoliths to their clade of origin only 59 % of the time. Although palms were generally distinguished from non-palms, few palm clades were highly distinct, and phytolith morphology was weakly correlated with species' environmental preferences. Reconstructions at all fossil sites suggested that palm communities were dominated by Trachycarpeae and Areceae, with warm, equable climates and high, potentially seasonal rainfall. However, fossil site reconstructions had high uncertainty and often conflicted with other climate proxies. While phytolith morphology provides some distinction among palm clades, caution is warranted. Unlike prior spatially restricted studies, our geographically and phylogenetically broad study indicates phytolith morphology may not reliably differentiate most palm taxa in deep time. Nevertheless, it reveals distinct clades, including some likely to be palaeoenvironmentally informative.

First record of well-preserved canid coprolites from Eurasia: New insights into the unique ecological niche of Yuanmou Basin

This study reconstructs the Early Pleistocene paleoenvironment of the Yuanmou Basin through coproecology of the third member of the Yuanmou Formation. We examined 38 exceptionally well-preserved coprolites from a new fossil locality, and attributed the putative defecating agent to the hypercarnivorous diet canid, Sinocuon yuanmouensis through geochemical and quantitative analyses. A new ichnogenus and ichnospecies, Cuocopros yuanmouensis igen. et. isp. nov., was established based on distinctive characteristics. Multi-disciplinary analysis, including sediment palynology and lithostratigraphy, helped primarily reconstruct a significant climatic event during the early Pleistocene, coinciding with the emergence of Yuanmou Man during the fourth member of the Yuanmou Formation's deposition. The findings provide insights into coexistence between canids, hyaenas, hominoids, and other fauna, revealing a rich paleoecosystem and food chain in the region's history. This study contributes to understanding the complex ecological dynamics during this period in the Yuanmou Basin.

New Pterosaur Tracks from the Hwasun Seoyuri Tracksite (Turonian) of South Korea: Implications for their Ecological Niche and Habitat

Pterosaurs are powered flight vertebrates that first emerged in the Late Triassic and persisted until the end of the Cretaceous. Recent studies on the ecological niches and habitats of pterosaurs, based on discoveries of Cretaceous bone beds in China, Brazil, Morocco, and other locations, suggest a decline in pterosaur diversity during the mid-Cretaceous. Various hypotheses have been proposed to interpret this phenomenon. This study focuses on newly discovered pterosaur tracks at the Upper Cretaceous (Truonian) Hwasun Seoyuri tracksite in Korea. The analysis is based on pterosaur tracks from in situ and ex situ specimens that originate from a variety of stratigraphic levels. The evidence found suggests that the Hwasun Seoyuri tracksite was occupied by small pterosaurs over an extended period, with indications of recurrent activity across at least six levels. Furthermore, the footprint sizes observed across these multiple layers follow a non-skewed normal distribution. Considering the known logarithmic growth characteristics of pterosaurs, this result suggests a predominantly immature population at this site. The prevalence of mid-Cretaceous non-marine pterosaur tracksites on the Korean Peninsula may reflect broader ecological shifts for pterosaurs during this period. This evidence is considered alongside the habitat shifts suggested by other non-marine pterosaur fossil sites in China and Brazil, as well as with indications of the decline in Late Cretaceous non-marine basins.

New fossiliferous sites from the mid-Cretaceous Tendrara dome (High Plateaus, Morocco): biostratigraphical, paleoenvironmental and paleogeographical implications

Sedimentological and stratigraphical studies in the Cretaceous series of the Tendrara dome led to the discovery of fossiliferous levels in the pre-Cenomanian and Cenomanian deposits, providing significant biostratigraphic, paleoenvironmental, and paleogeographic results. In the SW part of the Tendrara dome, the predominantly terrigenous deposits at the base of the pre-Cenomanian (Dekkar 1 Formation) yielded dinosaur eggshell fragments and charophytes, in particular Clavatoraceans, pointing to the Barremian-Aptian. Above this unit, two beds with fish remains were discovered in the Dekkar 2 Formation and at the base of the Dekkar 3 Formation, respectively. To the NE of the Tendrara dome, a fossiliferous site with diversified benthic fauna and abundant fish remains was discovered in a thin marly unit unconformably overlying the Middle Jurassic basement. Elasmobranch micro-remains indicate a Cenomanian age for this unit. The SW-NE correlations indicate a marked thickness reduction and lateral facies variations, implying a strong asymmetry in the Cretaceous paleogeography of the dome. The first continental and lagoonal basins of the Barremian-Aptian and Albian?-Cenomanian are located in the southern part of the Tendrara dome. The Cenomanian transgression, initiated from the south, gradually covered the dome, depositing reduced coastal plain elasmobranch-rich facies in its northern part. The Tendrara dome constituted a paleogeographic barrier, limiting the first transgressions of the Cenomanian sea. This paleostructure is part of an emerged area (Idrissides High) located between the Tethyan Ocean and the Saharan epicontinental sea.

The Picocoraciades (hoopoes, rollers, woodpeckers, and allies) from the early Eocene London Clay of Walton-on-the-Naze

We describe upupiform, coraciiform, and possible piciform birds from the early Eocene London Clay of Walton-on-the-Naze (Essex, UK). The material includes partial skeletons of a new species of a small upupiform bird, Waltonirrisor tendringensis, gen. et sp. nov., which is the earliest known representative of the Upupiformes. Three very similar species of stem group rollers are assigned to Laputavis robusta, Septencoracias morsensis, and S. simillimus, sp. nov. These species only differ in minor features, which raises the possibility that the taxon Sepencoracias Bourdon, 2016 is a junior synonym of Laputavis Dyke, 2001. A smaller stem group roller from Walton-on-the-Naze resembles the North American primobucconid species Primobucco mcgrewi. We also describe two species of a new genus-level taxon, Pristineanis, gen. nov., which shows close affinities to the North American “Neanis” kistneri and may be a stem group representative of the Piciformes. In many aspects of their postcranial osteology, the stem group Coracii from Walton-on-the-Naze, as well as the new taxon Pristineanis, resemble coeval Trogoniformes from this fossil site. Because trogons are the extant sister taxon of the Picocoraciades – the clade including the Upupiformes, Coraciiformes, and Piciformes –, the shared similarities are likely to be plesiomorphic for this latter clade. Early Cenozoic representatives of the Upupiformes and Coraciiformes were much smaller than their extant relatives, which suggests that the Picocoraciades are an avian example of Cope’s Rule that postulates a tendency for size increase in evolutionary lineages over time.

The dinosaurs that weren't: osteohistology supports giant ichthyosaur affinity of enigmatic large bone segments from the European Rhaetian.

Very large unidentified elongate and rounded fossil bone segments of uncertain origin recovered from different Rhaetian (Late Triassic) fossil localities across Europe have been puzzling the paleontological community since the second half of the 19th century. Different hypotheses have been proposed regarding the nature of these fossils: (1) giant amphibian bones, (2) dinosaurian or other archosaurian long bone shafts, and (3) giant ichthyosaurian jaw bone segments. We call the latter proposal the 'Giant Ichthyosaur Hypothesis' and test it using bone histology. In presumable ichthyosaur specimens from SW England (Lilstock), France (Autun), and indeterminate cortical fragments from Germany (Bonenburg), we found a combination of shared histological features in the periosteal cortex: an unusual woven-parallel complex of strictly longitudinal primary osteons set in a novel woven-fibered matrix type with intrinsic coarse collagen fibers (IFM), and a distinctive pattern of Haversian substitution in which secondary osteons often form within primary ones. The splenial and surangular of the holotype of the giant ichthyosaur Shastasaurus sikanniensis from Canada were sampled for comparison. The results of the sampling indicate a common osteohistology with the European specimens. A broad histological comparison is provided to reject alternative taxonomic affinities aside from ichthyosaurs of the very large bone segment. Most importantly, we highlight the occurrence of shared peculiar osteogenic processes in Late Triassic giant ichthyosaurs, reflecting special ossification strategies enabling fast growth and achievement of giant size and/or related to biomechanical properties akin to ossified tendons.

Ecometric models of small mammal hypsodonty can estimate paleoprecipitation across eastern Africa

Ecometric analyses use the relationships between functional traits and the environment at the community level to quantitatively estimate past climatic and environmental variables at fossil sites. Hypsodonty (tooth crown height) in North American rodent and lagomorph (Glires) communities is correlated with mean annual temperature and annual precipitation. Here, we examine the community hypsodonty of African Glires to test if this relationship translates to a continent with more extreme climates and to quantify paleoprecipitation at important fossil sites. Categorical hypsodonty values were gathered from the literature and museum collections for 94 modern African taxa (88%). We used maximum likelihood to model the ecometric relationship between hypsodonty and annual precipitation. We then produced trait-based estimates of paleoprecipitation for 26 well-sampled fossil localities from eastern Africa over the last 5.7 Ma. We confirmed other regional studies by identifying increasing aridity and decreasing annual precipitation (824 mm to 480 mm) in the Late Miocene of Kenya. From the Ethiopian Shungura Formation, we estimated temporal fluctuations in precipitation that correspond with the presence or absence of paleolakes and rivers. Small mammal community hypsodonty illustrates that east African communities have converged towards mesodont means and high standard deviations in response to climate change.

A newly discovered Hystrix primigenia specimen from the Kemiklitepe collection at Ege University Natural History Museum: insights into paleobiogeography in Eurasia.

Porcupines, members of the Hystricidae family, represent a unique group of herbivorous mammals. This study details the identification of a newly discovered mandible fragment of Hystrix primigenia, along with a right cheek tooth series from the middle Turolian Kemiklitepe-A fossil locality. While Hystrix fossils are found in numerous localities, the materials are often limited to a few dental fragments or isolated teeth, posing challenges to systematic investigations. The examination of this lower tooth series prompted a comprehensive review of all H. primigenia findings across Eurasia, shedding light on its adaptive characteristics over time and space. Our paleobiogeographical analysis indicates the absence of H. depereti in Late Miocene Türkiye, while the dispersal range of H. primigenia is broader than that of H. depereti in Eurasia. Additionally, the study delves into the discussion of H. primigenia and H. depereti findings in Eurasia, ultimately refining the categorization of Late Miocene Hystrix discoveries in Türkiye to two species: H. primigenia and H. kayae. Our review suggests the possibility of an additional H. kayae finding from Samos, Greece.

Late Triassic floras from Guangdong, South China: Biostratigraphical context and palaeoenvironmental implications

Triassic-Jurassic deposits are well developed in Guangdong Province, South China. In particular, the Upper Triassic coal-bearing strata which alternate between marine and terrestrial deposits yield diverse and abundant fossil plants, ammonites and bivalves. These strata provide a significant reference for the study of palaeoenvironmental variations in the lower latitude regions. In this paper, we review the major progress on Late Triassic floral studies in this area. Specifically, we compare the regional plant assemblages from different fossil sites in central and northern Guangdong which have been dated with marine fauna. 155 species belonging to 56 genera of fossil plants have been reported so far in northern and central Guangdong. The Late Triassic floras in Guangdong are mainly composed of Bennettitales and ferns, followed by horsetails, seed ferns, cycads, ginkgos and conifers. In ascending order, four regional plant fossil assemblages can be recognized in the Late Triassic deposits, namely the Pachypteris-Lindleycladus Assemblage (Julian), the Pterophyllum-Baiera Assemblage (late Julian), the Clathropteris-Otozamites Assemblage (Tuvalian), and the Danaeopsis-Anomozamites Assemblage (Rhaetian). In general, the Late Triassic climate in the Guangdong region was mainly humid and warm and either tropical or subtropical. The fossil plants corroborate palaeomagnetic evidence that the central and northern Guangdong region was located at approximately the same latitude as it is today and formed the southern coastline of the South China Block during the Late Triassic. Palaeogeographically, the transgression started at the end of the Julian and the south coastal terrane consisted of a western bay, a peninsula and an eastern bay. During the regression period, post-Rhaetian, the bays evolved into a gulf coastal plain.

First evidence of Pinaceae and Fagaceae in the fossil wood record of the České středohoří Mts. (Czech Republic): A comprehensive study of fossiliferous sites in pyroclastic rocks surrounding the late Oligocene Milá stratovolcano

A comprehensive anatomical and mineralogical study of fossil wood fragments from fields in the vicinity of Bečov and Břvany villages (NW Bohemia, Czech Republic) indicates that Taxodioxylon gypsaceum (Cupressaceae s.l.) predominates, but also identifies another coniferous wood: Pinuxylon parryoides (Pinaceae) and three angiosperms Quercoxylon böckhianum, Castanoxylon bavaricum and Lithocarpoxylon sp. (all Fagaceae). This paper therefore presents the first occurrence of Pinaceae and Fagaceae fossil wood in the volcanic rocks of the České Středohoří Mts. as well as its youngest palaeobotanical record in general, late Oligocene in age (26.56 ± 0.38 Ma). The samples were buried by alkaline pyroclastic deposits and were mineralized by carbonates. Two distinct depositional processes burying the fossil woods were identified. Closer to the vent, the woods occur in a near-vent pyroclastic fall deposits of the former pyroclastic cone, whereas more distant sites consist of pyroclastic flow deposits. Carbonate mineralization mostly consists of dolomite, but subordinate amounts of magnesite (likely the first time this is documented in fossil wood) as well as calcite and siderite are present. Only one sample collected in the same area, bearing clear signs of riverbed transport (Lithocarpoxylon sp.), was perfectly silicified, but its origin remains unclear.

An overview of Miocene to Pleistocene methane-seep faunas from Taiwan: Paleoecology and paleobiogeographic implications

The invertebrate macrofauna of four methane-seep deposits of Miocene to Pleistocene age from Taiwan is taxonomically evaluated. The Neogene faunas, with one example each from the early and late Miocene and the Pliocene, consist exclusively of one or two large, infaunal lucinid bivalve genera per site, namely Meganodontia and Lucinoma. The former includes the large, charismatic Pliocene ‘Loripes’ goliath, which is here identified as belonging to the widespread, Neogene to Recent genus Meganodontia. The Pleistocene seep fauna is more diverse, includes extant species like the mytilid Gigantidas horikoshii and Meganodontia aff. acetabulum, unidentified species belonging to Lucinoma and the vesicomyid Isorropodon, and specimens resembling the enigmatic bivalve Sisonia frijellanae, described so far only from the late Miocene of the Philippines; the gastropods could not be identified below family level. The two Miocene seep faunules formed on the shelf of the Eurasian plate, the Pliocene faunule in an upper offshore setting in the Tainan foreland basin, whereas the Pleistocene site with its more diverse fauna formed closer to the shelf edge of the Tainan foreland basin. We suggest that water depth is the most likely driver of this difference in species diversity. The very negative δ13C signature of the seep carbonates of all fossil sites indicates the seepage of mostly biogenic rather than thermogenic methane, analogous to the extant seep sites around Taiwan. Biogeographically, the Miocene seep faunas show, with Meganodontia, links to seep faunas from lower to mid-latitudes worldwide (Caribbean Sea, Mediterranean Sea, Philippines, and New Zealand). From the Pliocene onward, biogeographic ties are more restricted to areas in the central Indo-West Pacific Ocean.

New fossil woods (upper Pleistocene) from the lower-middle Uruguay river basin (South America) reveal the past distribution of Aspidosperma (Apocynaceae)

The present work describes the taxonomic and paleobiogeographic study of two fossil woods related to extant Aspidosperma. The silicified specimens come from the fossil localities of Santa Ana (30°54′S, 57°55′W) and Concordia (31°19′S, 57°59′W), Entre Ríos Province, Argentina, belonging to the El Palmar Formation (Late Pleistocene). This unit represents the sedimentary body of the upper fluvial terrace generated by the Uruguay River in its middle basin in eastern Argentina. The anatomical features that distinguish the woods are growth rings delimited by axial parenchyma and fibers, semi-ring to-diffuse-porous woods; mainly solitary vessels; simple perforation plates; alternate, bordered, and vestured intervessel pits; scarce paratracheal and diffuse apotracheal axial parenchyma; homocellular, and uniseriate to-triseriate rays; non-septate fibers. Climate reconstruction modelled at the regional scale (Ecological Niche Modeling) revealed variations in macroecological diversity patterns of the nearest living relatives (Aspidosperma australe and A. polyneuron) over the last ca. 130,000 years. Optically stimulated luminescence dating of sediments from the upper part of the El Palmar Formation in the type area reveals that the unit spans from the Last Interglacial period (warm substage, MIS marine isotope stage 5a), to the penultimate interglacial (MIS 7). This period was characterized by warmer and wetter conditions than those observed today. The eco-anatomical characteristics of the fossil record reflect this type of environment. The modern analogues of the fossils studied here are now part of the forests that integrate the Atlantic forest and Araucaria forest biogeographic provinces in South America.

Re-investigation of fossil Lemmini specimens from the early and Middle Pleistocene of Western and Central Europe: Evolutionary and paleoenvironmental implications

The current study focuses on the emblematic Myopus/Lemmus species complex (tribe Lemmini) in the European Pleistocene fossil record. The members of the two genera occupy distinct ecological niches and have different external appearances, but they are remarkably similar in their dental morphology, so that they were commonly thought of as undistinguishable in the fossil record. Thus, more or less all European Lemmini fossils have been assigned to the genus Lemmus. In the Early Pleistocene site of Schernfeld (Germany), the species Lemmus kowalskii had been described. It was thought by some authors that all Lemmini from Early to late Middle Pleistocene belong to this species.In the current study, we investigated Lemmini molar morphology from Western and Central European sites including Schernfeld (Early Pleistocene), Sackdillinger Höhle (Sackdilling Cave), and Koněprusy C718 (both early Middle Pleistocene), as well as other fossil localities with fewer specimens, formerly assigned to Lemmus kowalskii. Using an extensive modern referential material of Lemmus and Myopus, this study proposes to re-evaluate taxonomic status of the Middle and Early Pleistocene Lemmini. This modern referential also allows a better understanding of the morphology of Lemmus kowalskii specimens and its variability.Our results highlight the very high variation within fossil populations, as well as significant statistical differences between populations of the Early and Middle Pleistocene localities. A large part of these fossil specimens is firmly identified as Myopus sp., including the L. kowalskii holotype. Our identifications demonstrate that in most Early and Middle Pleistocene sites considered in this study, both genera (Lemmus and Myopus) are present. Possible interpretations and consequences for current view of lemming history are discussed, as well as some of the paleoecological and paleoenvironmental implications.