Hasil untuk "Fossil man. Human paleontology"

Ethan D. Mooney, Tea Maho, Dylan C. T. Rowe et al.

Abstract Ontogeny and patterns of growth provide crucial insights into the evolution of dinosaurs and their biology, however, ontogenetic changes of the postcranial skeleton are generally poorly known and restricted to few species. Here, we report on the discovery of embryonic, eggshell, and hatchling material of the Early Jurassic sauropodomorph Massospondylus and provide new insights into the early life stages of early-diverging sauropodomorphs. The embryos described here represent a more advanced developmental stage than previously known embryonic materials and together show eggshells with progressive degrees of resorption correlating to embryonic development. The prominent “thumb” typical of early-diverging sauropodomorph dinosaurs also appears to be precociously ossified and ontogenetically variable. Together, these new Massospondylus embryos and hatchling indicate a quadrupedal posture and the resulting growth trajectory points to an important ontogenetically influenced ecological shift predicated on a continuum of locomotory dependent postural change, from obligate quadrupeds to obligate bipeds. Other Late Triassic and Early Jurassic sauropodomorph dinosaurs known from few ontogenetic stages also fit well on the extensive growth trajectory of Massospondylus with only modest variations in skull, neck, and limb proportions. This generally conservative body plan of early-diverging sauropodomorphs likely suggests a similar postural change for the early members of this large clade that preceded the obligate quadruped sauropods.

Alexander Nützel, Simon Schneider, Sofia Bakayeva et al.

Cowries, the family Cypraeidae, form a diverse and conspicuous group of gastropods living in tropical to subtropical seas. Their shell is convolute (last whorl covers all previous ones) with a narrow, slit-like siphonate aperture bearing denticles (“teeth”). When extended, a large part of their shell surface is covered by a soft fleshy mantle. The earliest cowries were reported from the Upper Jurassic of Sicily: Cypraea tithonica and Cypraea gemmellaroi. Subsequently, these species had been assigned to various cypraeid genera. Examination of the type material of Cypraea tithonica reveals that this species represents a new genus: Coffeacypraea Nützel & Schneider. Cypraea gemmellaroi also belongs to this new genus and is potentially synonymous with Coffeacypraea tithonica. The Upper Jurassic caenogastropod genera Colombellina and Zittelia (family Colombellinidae) also have narrowly elongated siphonate apertures and are closely related to Cypraeidae but their shells are not convolute. The origination of Cypraeidae and Colombellinidae contributed considerably to the Mesozoic–Cenozoic caenogastropod radiation.

Gaël E. Spicher, Tyler R. Lyson, Serjoscha W. Evers

Abstract Saxochelys gilberti is a baenid turtle from the Late Cretaceous Hell Creek Formation of the United States of America known from cranial, shell, and other postcranial material. Baenid turtles are taxonomically diverse and common fossil elements within Late Cretaceous through Eocene faunas. Detailed anatomical knowledge is critical to understanding the systematics and morphological evolution of the group. This is particularly important as baenids represent an important group of continental vertebrates that survived the mass extinction event associated with the Cretaceous/Paleogene boundary. High-resolution micro-computed tomography scanning of the holotype skull reveals additional anatomical details for the already well-known Saxochelys gilberti. This includes the revision of some anatomical statements from the original description, but also detailed knowledge on internal anatomical features of the braincase and the description of a well-preserved axis (cervical vertebra 2). Our new detailed description and previous work on the shell and postcrania make Saxochelys one of the best-described, nearly complete baenid turtles, which are often only known from either isolated shell or cranial material. A revised phylogenetic analysis confirms the position of Saxochelys gilberti as a derived baenid (Eubaeninae) more closely related to Baena arenosa than to Eubaena cephalica.

Soledad Gouiric-Cavalli, Ari Iglesias, Bárbara Cariglino et al.

Mesozoic deep-bodied actinopterygians are of interest given, among others, the various modes of feeding exhibited by these fishes. Regrettably, most of their fossil record is restricted to a limited number of localities in Europe. During the Late Jurassic fragmentation of Pangaea, the exchange of fauna between the European Tethys and the paleo-Pacific (southwestern of the South American region) was possible via the marine pathways connecting these areas. This exchange led to the speciation of fish taxa, particularly in the Southern Hemisphere. Although new species are continuously being discovered, our understanding of the Late Jurassic marine ichthyofaunas of the Southern Hemisphere remains limited. The Mesozoic ichthyofaunas of the Antarctic seas are rich but relatively poorly known presenting a significant opportunity for further research. Noteworthy, previous reports have documented the presence of actinopterygians in the Late Jurassic of the Antarctic Peninsula. Since 2016, a team of researchers from Argentina has been exploring the Upper Jurassic–Lower Cretaceous Ameghino (= Nordenskjöld) Formation outcrops, resulting in the discovery of a large collection of actinopterygian fishes. Nevertheless, most of the material remains undescribed. In this article, we report the discovery of a deep-bodied actinopterygian found at the Longing Gap, the type locality of the Ameghino Formation in the Antarctic Peninsula. The study of these newly collected materials allows for their taxonomic assignment to Ameghinichthys antarcticus, a taxon previously described for the locality but based on isolated and fragmentary material. Additionally, this study confirms that A. antarcticus belongs to Dapediiformes. Ameghinichthys antarcticus is among the youngest records of Dapediiformes and represents the southernmost record of the group worldwide.

Buyantegsh Batsaikhan, Chinzorig Tsogtbaatar, Ruiji Takasaki et al.

In this study, we redescribe the geology of fossil-bearing rocks, exposed in the Lower Cretaceous Khuren Dukh locality. This study is based on new data collected during the Mongolian Expedition (ME) in 2019. Previously, the Khuren Dukh Formation at the Khuren Dukh locality had been subdivided into three members (lower, middle, and upper) based on textural features and sedimentary structure of dominant lithofacies assemblages. This study shows that the lower member can be further subdivided into two major lithofacies associations (lithofacies association-1 and 2). Association-1 is characterized by a combination of the interbedded crossbedding of small-grained pebbles and coarse-grain-size sandstones. Association-2 consists of a medium to coarse grained, white-grayish sandstone, which is characterized as thick and structureless. A precise contact boundary between these two associations is ambiguous, however, it is distinguishable depending on the granular types and the color of the sediments regarding the studied areas. A horizontally oriented thin layer of dolomite and a carbonate black-grayish mud is exposed at the north of the study area and has been interpreted as the middle member of the Khuren Dukh Formation. We interpret this member as a lakebed (Figure-6A) and suggest additional geochemical work would contribute greatly to understanding the nature of the lake. Хүрэн Дух (Чойрын Хотгор) олдворт газрын хурдас хуримтлалын литофацийн ангилал

Daniel Varajão de Latorre

The baculum of mammals offers the opportunity to study the reproductive biology of extinct species given that it is a fossilizable part of the male genitalia and that its size and shape correlate with several aspects of the reproductive biology of extant mammals. Fossil bacula, however, are rare. Currently, bacula have been described from only two extinct species of canids, one from the subfamily Caninae and the other from the extinct subfamily Hesperocyoninae. Here, I describe the bacula of five extinct species of Borophaginae, each of which was found with other skeletal elements that have enabled identification to the species level. Two specimens (Aelurodon feroxandAelurodon stirtoni) are largely complete, while the baculum fromCarpocyon compressusis complete but still embedded in matrix that obscures some of its features. The bacula ofParatomarctus euthosandDesmocyon thomsoniare incomplete, but they provide useful information nonetheless. These borophagine bacula are similar to extant canines in being robust, having a urethral groove, and a simple distal end. These features suggest that the Borophaginae had long-lasting copulation and possibly spontaneous ovulation, similar to the extant canines. However, unlike the straight baculum of extant canines, borophagine bacula are ventrally curved (arched), which is also observed in the hesperocyonine baculum. The implication of this curvature for the reproductive biology of these animals remains unknown.

Alexandra Viertler, Karin Urfer, Georg Schulz et al.

Abstract The correct interpretation of fossils and their reliable taxonomic placements are fundamental for understanding the evolutionary history of biodiversity. Amber inclusions often preserve more morphological information than compression fossils, but are often partially hidden or distorted, which can impede taxonomic identification. Here, we studied four new fossil species of Darwin wasps from Baltic and Dominican amber, using micro computed tomography (micro-CT) scans and 3D reconstructions to accurately interpret and increase the availability of morphological information. We then infer their taxonomic placement in a Bayesian phylogenetic analysis by combining morphological and molecular data of extant and fossil Darwin wasps and evaluate the impact and usefulness of the additional information from micro-CT scanning. The results show that although we gained significant morphological information from micro-CT scanning, especially concerning measurements and hidden dorsal and ventral structures, this did not impact subfamily-level placement for any of the four fossils. However, micro-CT scanning improved the precision of fossil placements at the genus level, which might be key in future dating and diversification analyses. Finally, we describe the four new fossil species as Rhyssa gulliveri sp. nov. in Rhyssinae, Triclistus levii sp. nov. in Metopiinae, Firkantus freddykruegeri gen. et. sp. nov. in Pimplinae and Magnocula sarcophaga gen. et sp. nov. in Phygadeuontinae. The first two species are the first known representatives of the subfamilies Rhyssinae and Metopiinae in amber.

José Patricio O'Gorman, Carolina Acosta Hospitaleche, Marcelo Alfredo Reguero et al.

Se resumen los antecedentes históricos de la paleoherpetología argentina en Antártida y los principales descubrimientos (anuros, testudines, plesiosaurios, ictiosaurios, mosasaurios, dinosaurios no avianos y avianos) realizados por equipos de investigación en los que participaron científicos argentinos. Dado que nos resultaría demasiado extenso detallar cada uno de los hallazgos y estudios realizados, se incluye un detalle de la bibliografía que permitirá al lector ahondar en cualquiera de los campos de acuerdo con sus intereses.

Laura Codorniú, David Rivarola, Gabriela Castillo-Elías et al.

El presente trabajo resume la historia de la paleontología en los sedimentos mesozoicos de la provincia de San Luis, como así también, reseñas históricas de cómo surgieron las primeras actividades relacionadas a la creación de un museo. Los primeros hallazgos en esta provincia se dieron a conocer, aproximadamente, en la década de 1940 con el descubrimiento de pisadas de dinosaurios y luego de huesos frágiles en 1963. Cuando el reconocido paleontólogo José Bonaparte logró identificar estos huesos como pertenecientes a pterosaurios, se desencadenaron una serie de exploraciones en la región que dieron a conocer el primer reptil volador para Argentina. Fue a partir de 1990 que Luis M. Chiappe comenzó a dirigir trabajos de campo en la Formación Lagarcito y colectar cientos de especímenes de pterosaurios. De dichas  investigaciones surgió un patrimonio que constituiría a futuro la base de una importante colección de piezas fósiles, llegando a contar posiblemente con la mejor colección a nivel mundial de una única especie de reptil volador, incluyendo sus distintos estados ontogenéticos. Aquí, se resumen los hallazgos más importantes para este pterosaurio de San Luis, como así también los primeros restos de arcosauriformes de sedimentos triásicos. A lo largo de este relato, se aprecia que la historia de la paleoherpetología en San Luis es muy reciente.

Comité Organizor del VI SMPCNA

Libro de Resúmenes del VI Simposio del Mioceno-Pleistoceno del Centro y Norte de Argentina, organizado durante 30 de noviembre al 3 de diciembre 2021 en la Ciudad Autónoma de Buenos Aires, Argentina.

JOHN P. WILSON, JOHN B. SCANNELLA

The eucentrosauran centrosaurines Einiosaurus procurvicornis and Achelousaurus horneri are the two most commonly recovered ceratopsids from the Campanian Two Medicine Formation of northwestern Montana, USA. Einiosaurus procurvicornis is known from at least 15 individuals recovered from two monospecific bonebeds, while Achelousaurus horneri is primarily known from one articulated adult cranium as well as two isolated subadult individuals previously referred to the taxon. Previous assessments of ontogeny in these taxa, alongside closely related centrosaurines, focused primarily on crania of mature individuals and disarticulated elements of immature individuals. Here we describe an articulated subadult Einiosaurus procurvicornis skull (MOR 456 8-8-87-1) from the Einiosaurus procurvicornis type locality bonebed and compare its cranial ornamental development with the only identically sized articulated subadult eucentrosauran skull from the Two Medicine Formation, MOR 591. These individuals represent the only known articulated subadult skulls from the hypothesized eucentrosauran lineage in the Two Medicine Formation, thereby enabling comparison of early ontogenetic developmental sequence and timing of all three primary cranial ornaments (nasal, supraorbital, and parietosquamosal frill). Comparison indicates that parietosquamosal frill and supraorbital ornamentation development may have preceded nasal horncore development in these taxa. MOR 456 8-8-87-1 fills a gap between the plesiomorphic morphology of juvenile Einiosaurus procurvicornis supraorbital horncores and the rounded, spheroid mass of bone which characterizes adults. The complete left squamosal of MOR 456 8-8-87-1 is of adult size, in contrast to its shorter face and immature facial ornamentation, which suggests that in Einiosaurus procurvicornis, the face and facial ornamentation development occurred after the parietosquamosal frill had reached adult size.

Alexandre V. Demers-Potvin, Jacek Szwedo, Cassia P. Paragnani et al.

We report the discovery of Maculaferrum blaisi gen. et sp. nov, the first occurrence of the family Tettigarctidae, informally known as hairy cicadas, in North America. Maculaferrum blaisi is part of a new collection assembled during recent fieldwork in the Redmond Formation, Labrador, Canada, near Schefferville. It consists in a single isolated forewing whose venational characters allow a classification to Tettigarctinae at the subfamily level. Classification at a higher level remains uncertain since it displays a combination of characters supposedly unique to tribes Protabanini, Meunierini, and Tettigarctini. Thus, this discovery adds credence to suggestions of a revision of the definitions of these tribes since they seem to be based on many convergent or plesiomorphic characters. Remnants of a spotted pattern on the wing membrane and probable setae along some veins are also preserved. Observations of the holotype’s fine anatomical characters have been facilitated by the use of Reflectance Transformation Imaging (RTI), an emerging method for the visualization of compression and impression fossils. Considering that the estimated age of the Redmond Formation is the Cenomanian (Late Cretaceous), the discovery of M. blaisi contributes to a very recent expansion of the tettigarctid fossil record that fills a gap between Early Cretaceous and Cenozoic genera. It suggests that hairy cicadas maintained a global distribution and thrived in a variety of climate regimes well into the Late Cretaceous, and that their competitive exclusion by singing cicadas occurred definitely closer to the end of the Cretaceous, or even during the Cenozoic. This discovery is only the start of a thorough description of the recently expanded entomofauna in the Cretaceous of Labrador.

R. Schumann, J. Pigati

Arlington Canyon, in the northwest part of Santa Rosa Island, Channel Islands National Park, California, has been the setting for important scientific discoveries over the past half century, including the oldest human remains in North America, several vertebrate fossil sites, and purported evidence of a catastrophic extinction event at the end of the Pleistocene. The canyon is filled with alluvial sediments that date to between 16.4 and 1.1 ka (thousands of calibrated years before present), representing accumulation that occurred primarily in response to rising sea levels during the late Pleistocene and Holocene. The deposits are laterally discontinuous, exhibit a high degree of sedimentary complexity, and contain evidence of past climates and environments, including fossil bones, burned plant macrofossils, and invertebrate microfossils. Here, we show that it is critical to view the observations, data, and conclusions of scientific studies conducted in the canyon within this larger context so that localized facets of the spatially and temporally extensive alluvial deposits are not misinterpreted or misrepresented. By improving the baseline understanding of processes and drivers of sediment accumulation in Arlington Canyon, we hope to offer a solid foundation and better underpinning for future archeological, paleontological, and geochemical studies here and throughout the northern Channel Islands. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.

Sven Sachs, Michela M. Johnson, Mark T. Young et al.

The genus Mystriosaurus, established by Kaup in 1834, was one of the first thalattosuchian genera to be named. The holotype, an incomplete skull from the lower Toarcian Posidonienschiefer Formation of Altdorf (Bavaria, southern Germany), is poorly known with a convoluted taxonomic history. For the past 60 years, Mystriosaurus has been considered a subjective junior synonym of Steneosaurus. However, our reassessment of the Mystriosaurus laurillardi holotype demonstrates that it is a distinct and valid taxon. Moreover, we find the holotype of “Steneosaurus” brevior, an almost complete skull from the lower Toarcian Whitby Mudstone Formation of Whitby (Yorkshire, UK), to be a subjective junior synonym of M. laurillardi. Mystriosaurus is diagnosed in having: a heavily and extensively ornamented skull; large and numerous neurovascular foramina on the premaxillae, maxillae and dentaries; anteriorly oriented external nares; and four teeth per premaxilla. Our phylogenetic analyses reveal M. laurillardi to be distantly related to Steneosaurus bollensis, supporting our contention that they are different taxa. Interestingly, our analyses hint that Mystriosaurus may be more closely related to the Chinese teleosauroid (previously known as Peipehsuchus) than any European form.

Михаил Васильевич Шуньков, M. Shun'kov, А. П. Деревянко et al.

Today, Altai has the most insightful archaeological sites reflecting the ancient history of the vast space spanning from the Ural Mountains to the Pacific Ocean and from Mongolia to the Arctic Ocean. The most engaging findings in the study of the primitive period were obtained in the North-Western part of Altai based on the materials of a crosscutting study of multilayer Paleolithic sites in the valley upstream of the River Anuy. The longest cultural timeline was stu­died in Denisova Cave. Analysing the Pleistocene cave deposits, the researchers applied a number of modern methods in archeology, stratigraphy, lithology, paleontology, geochronology, and other related sciences. Besides cave deposits with numerous artefacts, they discovered extensive paleontological materials, which helped to trace the evolution of cultural traditions from the primitive period to the end of the Paleolithic era and reconstruct the living conditions of the primitive human beings across the paleogeographic stages of the Pleistocene. The latest anthropological discoveries in the cave are associated with the core issues in the development of Homo genus and the formation of modern man.

Dominique Mourelle, Renato B. Macedo, Aldo R. Prieto

Resumen. Los campos constituyen una de las regiones de los pastizales del Río de la Plata que se extiende en Uruguay y en la porción meridional de Rio Grande do Sul (Brasil), cuya potencialidad para realizar estudios palinológicos aún está escasamente explorada. En este trabajo se revisa y analiza el estado actual de las investigaciones palinológicas actuales y fósiles en la región de los campos. Se discuten los modelos de la relación polen-vegetación actual como análogo moderno y se sintetiza la información proveniente de los registros polínicos fósiles. La integración de estos resultados y la utilización de los modelos actuales para interpretar las secuencias fósiles permitieron realizar una reconstrucción preliminar de la historia de la vegetación de la región de los campos durante el  Pleistoceno Tardío y Holoceno. Los cambios de la vegetación fueron relacionados con forzantes abióticos (cambios en el nivel relativo del mar o en las condiciones climáticas) y bióticos (antrópicos), y se postulan posibles rutas de migración de distintos taxones y vinculaciones de los campos con otras regiones fitogeográficas. Finalmente se discuten las potencialidades de la región de los campos para los estudios palinológicos, las dificultades que frecuentemente se presentan para la integración de la información y se puntualizan aquellos aspectos que podrían considerarse en futuros trabajos para realizar interpretaciones más ajustadas de la información paleoecológica  disponible. Palabras clave. Análisis polínico. Pastizales del Río de la Plata. Bosques. Pleistoceno. Holoceno. Abstract. MODERN AND LATE QUATERNARY PALYNOLOGICAL ANALYSIS IN THE CAMPOS REGION (URUGUAY AND SOUTHERN BRAZIL): STATUS OF INVESTIGATIONS, DIFFICULTIES AND POTENTIALITIES. The campos constitute one of the regions of the Río de la Plata grasslands which extends in Uruguay and southern Rio Grande do Sul (Brazil), whose potentiality for carrying out palynological studies is still scarcely explored. This paper reviews and analyzes the current state of modern and fossil palynological research in the campos region. The potential use of modern pollen-vegetation relationship models as modern analogues is discussed and the information obtained from fossil pollen records is synthesized. The integration of these results and the use of modern pollen-vegetation relationship models to interpret fossil sequences allowed the preliminarily reconstruction of the vegetation history of the campos region during the late Pleistocene and Holocene. Vegetation changes were related to abiotic (relative sea level changes or climatic conditions) and biotic (anthropogenic) forcing factors, and possible taxa migration routes and links between the campos and other phytogeographic regions were postulated. Finally, the potentialities of the campos region for palynological studies are discussed, as well as the difficulties that frequently arise for the integration of the information and also those aspects that could be considered in future works to make more accurate interpretations of the available paleoecological information. Key words. Pollen analysis. Río de la Plata grasslands. Forests. Pleistocene. Holocene.

María J. Aris, Jose A. Corronca, Sebastián Quinteros et al.

Marrellomorphs (class Marrellomorpha) are a group of Paleozoic arthropods with a very poor fossil record. Here we describe a new marrellomorph arthropod Mimetaster florestaensis sp. nov. from the Tremadocian (earliest Ordovician) of Argentina. The new species is characterized by the shape and direction of the three pairs of principal spines, and the existence of strong secondary spines only in the proximal two-thirds of the anterolateral spines. As a result of phylogenetic analysis the new species integrates a trichotomy with Mimetaster hexagonalis and a Moroccan unnamed marrellid as sister groups. This discovery increases the known diversity of Marrellomorpha and represents the first occurrence of this group in South America, expanding the spatial distribution of the clade.

Manja Voss, Silvia Sorbi, Daryl P. Domning

“Halitherium” bellunense is exclusively known from a single individual from upper Oligocene glauconitic sandstone near Belluno, northern Italy. According to a review of its morphological basis, which consists of associated cranial elements, some vertebrae and ribs, this specimen is identified as a juvenile, because the first upper incisor (I1) and supposedly second upper molar (M2) are not fully erupted. However, its juvenile status allowed only cautious conclusions on its taxonomy and systematic affinity. The presence of a nasal process of the premaxilla with a broadened and bulbous posterior end, and a lens-shaped I1, corroborate an evolutionarily-derived status of this species that places it well within the sirenian crown group Dugonginae. Considering these new data and in order to avoid continued misuse of the inappropriate generic name of Halitherium, a new generic name, Italosiren gen. nov., and emended species diagnosis are supplied for this taxon.

L. Horwitz, M. Chazan

Kimberly G. Beck, Rodrigo Soler-Gijón, Jesse R. Carlucci et al.

Detailed studies on Carboniferous species of the xenacanth Orthacanthus have shown that the xenacanth dorsal fin spine can be used for skeletochronological analyses and provides valuable information about development, growth and environmental life conditions of those extinct sharks. We report here for the first time the histology and skeletochronology of Permian specimens, dorsal spines of Orthacanthus platypternus from the Craddock Bone Bed (lower Clear Fork Formation; Early Permian, Leonardian age) of northern Baylor County (north-central Texas, USA). Twelve dorsal spines of O. platypternus preserve a highly vascularized wall mainly composed of centrifugally growing dentine in a succession of dentine layers, probably deposited with an annual periodicity. As expected, spines of individuals with 1–2 dentine layers, presumably juveniles, present the smallest sizes. However, spines of individuals showing at least 3–4 dentine layers and interpreted to be subadults/young adults, are distributed in two spine-size clusters corresponding to females (probably the largest spines) and males, in agreement with the hypothesis of sexual size dimorphism proposed in a previous biometric analysis. Our comparative study of O. platypternus and the Stephanian species O. meridionalis further suggests that spine denticulation can be useful for distinguishing between species of Orthacanthus and sexually dimorphic forms (juvenile to adults) in each species. Total body length estimations of O. platypternus from the Craddock Bone Bed point to relatively large juveniles and small subadults/young adults (less than 2 m in total length), living as opportunistic predators in the pond-channel coastal plain environments represented by the bone bed deposits. The com-parative analyses of the ontogenetic stages of the recorded specimens of O. platypternus and their distribution along different facies and localities indicate that this species was euryhaline, diadromous with a catadromous life-cycle which was strongly regulated by the semi-arid, seasonally dry tropical climate affecting western Pangaea during the Early Permian