Exceptional Fossil Research Articles

Mammalian body size evolution was shaped by habitat transitions as an indirect effect of climate change

AbstractAimBody size evolution has long been hypothesized to have been driven by factors linked to climate change, but the specific mechanisms are difficult to disentangle due to the wide range of functional traits that covary with body size. In this study, we investigated the impact of regional habitat changes as a potential indirect effect of climate change on body size evolution.LocationEurope and North America.Time periodThe Neogene (~23–2 million years ago).Major taxaFive orders of terrestrial mammals: Artiodactyla, Carnivora, Perissodactyla, Proboscidea and Primates.MethodsWe compared the two continental faunas, which have exceptional fossil records of terrestrial mammals and underwent different processes of habitat transition during the Neogene. Using Bayesian multilevel regression models, we assessed the variation in the temporal dynamics of body size diversity among ecographic groups, defined by their continent of occurrence and dietary preference.ResultsModel comparisons unanimously supported a combined effect of diet and continent on all metrics of body size frequency distributions, rejecting the shared energetic advantage of larger bodies in colder climates as a dominant mechanism of body size evolution. Rather, the diet‐specific dynamics on each continent pinpointed an indirect effect of climate change – change in habitat availability, and thus the resource landscape as a key driver of mammalian evolution.Main conclusionsOur study highlights dietary preference as a mechanistic link between mammalian evolution and habitat transition mediating an indirect climate‐change effect and demonstrates the complexity of climatic influence on biodiversity. Our findings suggest that the intensified habitat modification today likely poses a bigger threat than climate change in itself to living mammals, and perhaps all endotherms.

The Middle Triassic vertebrate deposits of Kupferzell (Germany): Palaeoenvironmental evolution of complex ecosystems

In 1977, within 3 months of excavation, a 500 m spanning road-cut near Kupferzell (southern Germany) produced a total of ~30,000 vertebrate remains from the Middle Triassic Lower Keuper. The bulk of the material stems from two temnospondyl amphibians, Gerrothorax pulcherrimus (~70%) and Mastodonsaurus giganteus (~30%), with the pseudosuchian archosaur Batrachotomus kupferzellensis ranging first among the other remains. Analyses of data collected during excavation, supplemented by new fieldwork, provide rich information on the sedimentary setting as well as the development of the fauna and their ecosystems. The sequence consists of: basal coaly mudstones (K1), massive siltstones (K2), green siliciclastic mudstones (K3), yellow to pale brown marlstones (K4), and yellow massive dolostones (K5). The deposits comprise a succession of similar water bodies that were emplaced on a lacustrine to floodplain setting in which carbonate muds dominated. Two main lake systems, with intermittent/periodical marine influence, as well as relatively stark periods of drought, harboured complex vertebrate ecosystems. These were dominated by a relatively high diversity of fishes and temnospondyl amphibians with a lesser, but notable, presence of archosaurs, forming the top predators of the trophic web. The sequence records alternating periods of flooding and desiccation, shaping a relatively complex environmental setting that was likely prone to the presence of life, eventually becoming an exceptional fossil lagerstätte. Kupferzell, together with nearby contemporaneous localities, represent relatively diverse and complex ecosystems (including several top predators) that allow understanding the evolution and palaeoecology of Middle Triassic vertebrate communities, including the groups that diversified during the Mesozoic era.

The earliest known brood care in insects.

Brood care enhances offspring fitness and survival by providing protection or feeding through parents (commonly by females). It has evolved independently multiple times in animals, e.g. mammals, birds, dinosaurs and arthropods, especially various lineages of insects, and has significant implications for understanding the emergence of sociality of insects. However, few fossil insects document such an ephemeral behaviour directly. New exceptional fossils of the water boatman Karataviella popovi from the Middle-Late Jurassic Daohugou biota (ca 163.5 Ma, northeastern China), with adult females bearing clutches of eggs on their left mesotibia, provide a unique brooding strategy (asymmetric egg-carrying behaviour) unknown in all extinct and extant insects. Our discovery represents the earliest direct evidence of brood care among insects, pushing back by more than 38 million years, indicating that relevant adaptations associated with maternal investment of insects can be traced back to at least the Middle-Late Jurassic, and highlighting the existence of diverse brooding strategies in Mesozoic insects. In addition, our discovery reveals that a specialized trawl-like filter-capture apparatus of K. popovi probably represents pre-adaptions originally used for trapping coeval anostracan (fairy shrimp) eggs for food.

Dataset accompanying "Exceptional fossil preservation and evolution of the ray-finned fish brain"

Dataset accompanying "Exceptional fossil preservation and evolution of the ray-finned fish brain"

Vertebrate ichnofauna from Sierra de las Cabras tracksite (Late Miocene, Jumilla, SE Spain). Mammalian ichnofauna

Upper Miocene sedimentary deposits of Sierra de las Cabras in the Prebetic Ranges (Jumilla, Región de Murcia, Spain) yield a exceptional fossil site of diverse vertebrate ichnofauna, including mammals and birds. This paper presents a detailed study of those ichnites of that site which correspond to mammals. The footprints are located in stratigraphic surfaces found in a thin marly limestone succession that can be assigned to the latest Tortonian to earliest Messinian. The mammalian record consists of 324 footprints (included in trackways, pairs, groups and isolated ichnites) of diverse vertebrates, including: Hippipeda, Rhynoceripeda, Canipeda, Felipeda, Ursipeda, Rodentipeda, as well possible Suipeda. The ichnites were imprinted on wet and cohesive marly carbonate mud, deposited in a semi-arid wetland with relevant freshwater influx. The fossil site, cleaned and protected some years ago but herein studied by the first time, add together the nearby Hoya de la Sima site (Hippipeda, Pecoripeda, Bestiopeda and Paracamelichnium, and probably proboscidean ichnites) to conform an exceptional record of Late Miocene ichnofauna in southern Iberia.

†Dicentrarchus oligocenicus, sp. nov. (Perciformes, Moronidae): the first record of an Oligocene Sea Bass skeleton from Romania, with a revision of †Morone major (Agassiz) from Piatra-Neamţ (Eastern Carpathians)

ABSTRACT The Oligocene fish fauna of the Romanian Eastern Carpathians is of great interest for the study of the extinct European perciform fish assemblages because their diversity and fine preservation. Amongst these deposits, some exceptional fossil localities such as the recently discovered outcrop from the Coza Valley and the well-known historical locations (sites) from Piatra-Neamț and Suslănești, often offer new insights about the Paratethys fish faunas. Herein, we report for the first time the discovery of a fish skeleton originating from the Bituminous Marls Formation exposed in the Coza Valley (Vrancea Half-Window, Marginal Folds Nappe) that we refer to †Dicentrarchus oligocenicus, sp. nov.. Also, we review an existing specimen previously misidentified as †Morone major (Agassiz) found in the Lower Dysodilic Shales Formation of Piatra-Neamț (Bistrița-Râșca Half-Window, Marginal Folds Nappe) that will be referred henceforth to the Percoidei incertae sedis. While the new species described herein has been classified as belonging to the family Moronidae because of obvious meristic, morphometric and osteological features, the other species has been removed from this family due to the lack of diagnostic characters. Remarks on how †Dicentrarchus oligocenicus, sp. nov. differs from all extant and extinct representatives of moronid fishes are given.

Complex axial growth patterns in an early Cambrian trilobite from South Australia.

The exceptional fossil record of trilobites provides our best window on developmental processes in early euarthropods, but data on growth dynamics are limited. Here, we analyse post-embryonic axial growth in the Cambrian trilobite Estaingia bilobata from the Emu Bay Shale, South Australia. Using threshold models, we show that abrupt changes in growth trajectories of different body sections occurred in two phases, closely associated with the anamorphic/epimorphic and meraspid/holaspid transitions. These changes are similar to the progression to sexual maturity seen in certain extant euarthropods and suggest that the onset of maturity coincided with the commencement of the holaspid period. We also conduct hypothesis testing to reveal the likely controls of observed axial growth gradients and suggest that size may better explain growth patterns than moult stage. The two phases of allometric change in E. bilobata, as well as probable differing growth regulation in the earliest post-embryonic stages, suggest that observed body segmentation patterns in this trilobite were the result of a complex series of changing growth controls that characterized different ontogenetic intervals. This indicates that trilobite development is more complex than previously thought, even in early members of the clade.

Iron from continental weathering dictated soft‐part preservation during the Early Ordovician

AbstractThe Fezouata Shale in Morocco is the most diverse Lower Ordovician unit yielding soft‐tissue preservation. Iron played a crucial role in the preservation of soft parts in this formation through the damage of bacterial membranes under oxic conditions and the pyritization of soft parts under the activity of bacterial sulphate reduction. However, the origin of Fe in this formation remains largely speculative. Herein, trace and rare earth elements were investigated in drilled‐core sediments from the Fezouata Shale. It is shown that a correlation exists between Fe and Al suggesting that most Fe has a detrital source. Elemental concentrations in the Fezouata Shale are most comparable to rivers and are the least similar to loess and sediments deposited near active island arcs. In this sense, continental weathering and its related Fe in river fluxes dictated occurrences of exceptional fossil preservation in the Fezouata Shale.

Ultrastructure and in-situ chemical characterization of intracellular granules of embryo-like fossils from the early Ediacaran Weng’an biota

Embryo-like fossils from the early Ediacaran Weng’an biota provide a window of exceptional fossil preservation onto the period of life history in which molecular clocks estimate the fundamental animal lineages to have diverged. However, their diversity and biological affinities have proven controversial, because they are morphologically simple and, consequently, their interpretation lacks phylogenetic constraint. The subcellular structures preserved in these embryo-like fossils might help to understand their cytology, biology, and diversity, but the potential of these structures has not been fully realized, because detailed microscale physical and chemical investigations are lacking. Here, to remedy this deficiency, we performed a comprehensive study to characterize their micro- and ultra-structures as well as in-situ chemical components. Our results reveal three types of subcellular structure that differ in size, shape, and mineral components: (1) relatively small and spheroidal granules in embryo-like fossils with equal cell division pattern; (2) relatively large, spheroidal, or polygonal granules in embryo-like fossils with unequal and asynchronous cell division pattern; and (3) irregular multi-layered rim-bounded granules in embryo-like fossils with unequal and asynchronous cell division pattern. We propose that the three types may be rationalized to a single taphonomic pathway of preferential mineralization of the cell cytoplasm, preserving an external mould of subcellular granules. We followed the previous interpretation that the spheroidal and polygonal granules should be fossilized lipid droplets or yolk platelets. The distinction between these subcellular structures are largely the result of postmortem degradation processes such as autolysis. The widely preserved lipid droplets or yolk platelets within these Ediacaran embryo-like fossils are compatible with the interpretion of large yolky embryos with maternal nourishment and direct development.

Earliest evidence of herd-living and age segregation amongst dinosaurs

Sauropodomorph dinosaurs dominated the herbivorous niches during the first 40 million years of dinosaur history (Late Triassic–Early Jurassic), yet palaeobiological factors that influenced their evolutionary success are not fully understood. For instance, knowledge on their behaviour is limited, although herding in sauropodomorphs has been well documented in derived sauropods from the Late Jurassic and Cretaceous. Here we report an exceptional fossil occurrence from Patagonia that includes over 100 eggs and skeletal specimens of 80 individuals of the early sauropodomorph Mussaurus patagonicus, ranging from embryos to fully-grown adults, with an Early Jurassic age as determined by high-precision U–Pb zircon geochronology. Most specimens were found in a restricted area and stratigraphic interval, with some articulated skeletons grouped in clusters of individuals of approximately the same age. Our new discoveries indicate the presence of social cohesion throughout life and age-segregation within a herd structure, in addition to colonial nesting behaviour. These findings provide the earliest evidence of complex social behaviour in Dinosauria, predating previous records by at least 40 My. The presence of sociality in different sauropodomorph lineages suggests a possible Triassic origin of this behaviour, which may have influenced their early success as large terrestrial herbivores.

Exceptional fossil assemblages confirm the existence of complex Early Triassic ecosystems during the early Spathian

The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a major faunal shift between the Palaeozoic and the Modern evolutionary fauna. The temporal, spatial, environmental, and ecological dynamics of the associated biotic recovery remain highly debated, partly due to the scarce, or poorly-known, Early Triassic fossil record. Recently, an exceptionally complex ecosystem dated from immediately after the Smithian/Spathian boundary (~ 3 myr after the PTB) was reported: the Paris Biota (Idaho, USA). However, the spatiotemporal representativeness of this unique assemblage remained questionable as it was hitherto only reported from a single site. Here we describe three new exceptionally diverse assemblages of the same age as the Paris Biota, and a fourth younger one. They are located in Idaho and Nevada, and are taxonomic subsets of the Paris Biota. We show that the latter covered a region-wide area and persisted at least partially throughout the Spathian. The presence of a well-established marine fauna such as the Paris Biota, as soon as the early Spathian, indicates that the post-PTB biotic recovery and the installation of complex ecosystems probably took place earlier than often assumed, at least at a regional scale.

A new bauriamorph therocephalian adds a novel component to the Lower Triassic tetrapod assemblage of the Fremouw Formation (Transantarctic Basin) of Antarctica

ABSTRACT The Fremouw Formation (Transantarctic Basin) of Antarctica preserves an exceptional fossil record of tetrapods from the beginning of the Mesozoic at high paleolatitude. Many of these fossils can be identified to species that also occur in the much richer Lystrosaurus declivis Assemblage Zone of South Africa’s Karoo Basin, but endemic species also occur. A third category of Antarctic fossils includes those that can only be broadly classified or lack sufficient diagnostic features for a synapomorphy-based identification. Therocephalians are a prime example of the last category, with Akidognathidae indet., Baurioidea indet., and cf. Ericiolacerta parva, currently recognized from the lower Fremouw Formation. Here we describe the most complete skull for an Antarctic therocephalian discovered to date. Notictoides absens, gen. et sp. nov., preserves a unique dental formula, a large intranarial portion of the septomaxilla, two bony excrescences along the rostral margin of the lacrimal, and a complete secondary palate formed by the maxilla. These features, in combination with a sagittal crest with a slit-like parietal foramen, a long, low dentary, and reduced upper and lower antecanine tooth count, suggest a relatively derived position for N. absens within baurioids. Indeed, the results of an updated cladistic analysis unite N. absens with the clade including Nothogomphodon, Ordosiodon, and Bauriidae. More broadly, the discovery of a third endemic species in the Lower Triassic rocks of the Fremouw Formation suggests that diversification in the wake of the Permian–Triassic mass extinction was likely more geographically complex than currently appreciated.

New fossil discoveries illustrate the diversity of past terrestrial ecosystems in New Caledonia

New Caledonia was, until recently, considered an old continental island harbouring a rich biota with outstanding Gondwanan relicts. However, deep marine sedimentation and tectonic evidence suggest complete submergence of the island during the latest Cretaceous to the Paleocene. Molecular phylogenies provide evidence for some deeply-diverging clades that may predate the Eocene and abundant post-Oligocene colonisation events. Extinction and colonization biases, as well as survival of some groups in refuges on neighbouring paleo-islands, may have obscured biogeographic trends over long time scales. Fossil data are therefore crucial for understanding the history of the New Caledonian biota, but occurrences are sparse and have received only limited attention. Here we describe five exceptional fossil assemblages that provide important new insights into New Caledonia’s terrestrial paleobiota from three key time intervals: prior to the submersion of the island, following re-emergence, and prior to Pleistocene climatic shifts. These will be of major importance for elucidating changes in New Caledonia’s floristic composition over time.

Beyond Eocene and Oligocene Epochs: The Causses du Quercy Geopark and the Grande Coupure

The phosphatieres du Quercy are karstic fillings exploited for phosphate at the end of the 19th century. They yield countless continental fossils through some 30 million years, ranging from late early Eocene to early Miocene. This exceptional paleontological series documents the ‘Grande Coupure’, a major biogeographical event involving a profound renewal of vertebrate faunas, recorded in Eurasia during the Eocene–Oligocene transition. This exceptional fossil record is key to understanding the impact of biotic and abiotic factors during this turbulent time of global change. The presence of natural mummies and the 3D preservation of numerous vertebrate skulls, as well as remains of arthropods and plants, are all attractive means to raise public awareness and promote an internationally unique geoheritage.

A novel tool to untangle the ecology and fossil preservation knot in exceptionally preserved biotas

Understanding the functioning of extinct ecosystems is a complicated knot of ecological, evolutionary, and preservational strands that must be untangled. For instance, anatomical and behavioral differences can profoundly alter fossilization pathways. This is particularly true in exceptionally preserved soft-bodied biotas that record the earliest phases of animal evolution during the Cambrian Explosion and the Ordovician Radiation. Herein, a novel method of data partitioning based on probabilistic modelling is developed to examine these processes for the Walcott Quarry, Burgess Shale, Canada (510Ma), and the Fezouata Shale, Morocco (c. 475Ma). The modelling shows that the mechanism for soft-tissue preservation in the Walcott Quarry is ecologically selective, favoring the endobenthos. This is not found in the Fezouata Shale. Taken in concert with bioturbation data, a new model of comparative preservation is developed based on sedimentary flow dynamics. This suggests that during the Cambrian Explosion and Ordovician Radiation the most exceptional fossils sites must still be calibrated against each other to understand the unfolding evolutionary events and the ecological structuring of ancient animal communities.

Evolutionary drivers, morphological evolution and diversity dynamics of a surviving mammal clade: cainotherioids at the Eocene-Oligocene transition.

The Eocene-Oligocene transition (EOT) represents a period of global environmental changes particularly marked in Europe and coincides with a dramatic biotic turnover. Here, using an exceptional fossil preservation, we document and analyse the diversity dynamics of a mammal clade, Cainotherioidea (Artiodactyla), that survived the EOT and radiated rapidly immediately after. We infer their diversification history from Quercy Konzentrat-Lagerstätte (south-west France) at the species level using Bayesian birth-death models. We show that cainotherioid diversity fluctuated through time, with extinction events at the EOT and in the late Oligocene, and a major speciation burst in the early Oligocene. The latter is in line with our finding that cainotherioids had a high morphological adaptability following environmental changes throughout the EOT, which probably played a key role in the survival and evolutionary success of this clade in the aftermath. Speciation is positively associated with temperature and continental fragmentation in a time-continuous way, while extinction seems to synchronize with environmental change in a punctuated way. Within-clade interactions negatively affected the cainotherioid diversification, while inter-clade competition might explain their final decline during the late Oligocene. Our results provide a detailed dynamic picture of the evolutionary history of a mammal clade in a context of global change.

Priapulid worms from the Cambrian of China shed light on reproduction in early animals

In the recent years, exceptional fossil sites have revealed astonishing details on the anatomy, lifestyles and behaviour of Cambrian animals but surprisingly, very little is known about one of their most vital features, reproduction. We describe here in situ eggs (clusters of 3 to 30 oocytes) in the tube-dwelling priapulid worm Paraselkirkia sinica from the Cambrian Stage 3 Xiaoshiba Lagerstätte (ca. 514 Ma, South China). These oocytes were accommodated within paired tubular ovaries located in the posterior half of the primary body cavity as in modern meiobenthic priapulid worms, thus indicating that the general organization of female tubular gonads in priapulid worms has remained virtually unchanged for half a billion years. Our findings provide for the first time, key information on the reproductive organs and strategies of early ecdysozoans, a huge animal clade that dominated Cambrian marine ecosystems and accounts for a large part of today's biodiversity (e.g. arthropods). Moreover, we also emphasize the critical role of ecology on the reproductive strategies and lifestyles of both modern and Cambrian worms.

A new pelomedusoid turtle, Sahonachelys mailakavava, from the Late Cretaceous of Madagascar provides evidence for convergent evolution of specialized suction feeding among pleurodires.

The Maevarano Formation in northwestern Madagascar has yielded a series of exceptional fossils over the course of the last three decades that provide important insights into the evolution of insular ecosystems during the latest Cretaceous (Maastrichtian). We here describe a new genus and species of pelomedusoid turtle from this formation, Sahonachelys mailakavava, based on a nearly complete skeleton. A phylogenetic analysis suggests close affinities of Sahonachelys mailakavava with the coeval Madagascan Sokatra antitra. These two taxa are the only known representatives of the newly recognized clade Sahonachelyidae, which is sister to the speciose clade formed by Bothremydidae and Podocnemidoidae. A close relationship with coeval Indian turtles of the clade Kurmademydini is notably absent. A functional assessment suggests that Sahonachelys mailakavava was a specialized suction feeder that preyed upon small-bodied invertebrates and vertebrates. This is a unique feeding strategy among crown pelomedusoids that is convergent upon that documented in numerous other clades of turtles and that highlights the distinct evolutionary pathways taken by Madagascan vertebrates.

Age, microfacies and sedimentary environments of the Sirenia-bearing deposits of the Qom Formation in Central Iran

Sea cows are exceptional fossil vertebrates recently discovered in the deposits of the Qom Formation. Yet, the Sirenia-bearing limestones are still poorly understood in terms of detail paleoenvironmental and micropaleontological investigations. In order to distinguish the temporal and paleoenvironmental context of the Sirenia (sea cow) bearing deposits of the Qom Formation in central Iran, three stratigraphic sections were studied in Hamedan (Ivak and Shirinsu) and Isfahan (Chahriseh) provinces. A total number of 47 thin sections were studied for micropaleontology, biozonation and carbonate microfacies analysis, as well as sedimentary environment recounstruction. Biostratigraphical investigations suggest that the Sirenia-bearing deposits are Aquitanian/Burdigalian in age, which implies restriction of sea cows remains to the Lower Miocene. We recognized nine microfacies (n=8 correspond to carbonate; n=1 correspond to siliciclastic) in the study areas. They are systematically grouped into two microfacies settings, representing inner and middle ramp environments. This is based on the facies associations and the distribution of skeletal components and rock textures. The Sirenia-bearing limestone consists of peloid/algae bearing wackstone/packstone/floatstone. A carbonate (inner) ramp system under shallow water conditions is interpreted as the habitats of the Sirenian mammals during the Aquitanian/Burdigalian in Central Iran. This paleoenvironmental setting could be utilized for further exploration of Qom Formation deposits for discovering sea cows.

Distraction sinking and fossilized coleoid predatory behaviour from the German Early Jurassic

Exceptional fossil preservation is required to conserve soft-bodied fossils and even more so to conserve their behaviour. Here, we describe a fossil of a co-occurrence of representatives of two different octobrachian coleoid species. The fossils are from the Toarcian Posidonienschiefer of Ohmden near Holzmaden, Germany. The two animals died in the act of predation, i.e. one had caught the other and had begun to nibble on it, when they possibly sank into hypoxic waters and suffocated (distraction sinking). This supports the idea that primitive vampyromorphs pursued diverse feeding strategies and were not yet adapted to being opportunistic feeders in oxygen minimum zones like their modern relative Vampyroteuthis.