PALEONTOLOGY IN MAY, 2024

ABSTRACT

Placerias hesternus, a Late Triassic dicynodont, is one of the last megafaunal synapsids of the Mesozoic. The species has a tusk-like projection on its maxillary bone, known as the caniniform process. This process has been hypothesized to be sexually dimorphic since the 1950s, however this claim has not been thoroughly investigated quantitatively. Here, we examined maxillae, premaxillae, quadrates, and fibulae from a single population from the Placerias Quarry in the Blue Mesa Member of the Chinle Formation, near St. Johns, Arizona, USA to determine if the caniniform process is dimorphic. We made a total of 25 measurements from the four bones and used a maximum likelihood framework to compare the fit of unimodal versus bimodal distributions for each set of measurements. Our results from complete maxillae reveal that the caniniform process has two distinct morphs, with a shorter and longer form. This interpretation is substantiated both by strong statistical support for bimodal distribution of caniniform lengths, and by clustering analysis that clearly distinguishes two morphs for the maxillae. Clustering analysis also shows support for potential dimorphism in the shape of the quadrate. However, no measurements from elements other than the maxilla have a strong likelihood of bimodal distribution. These results support the long-standing hypothesis that the caniniform in Placerias was dimorphic. Alternative explanations to sexual dimorphism that could account for the dimorphism among these fossils include the presence of juveniles in the sample or time-averaged sampling of a chronospecies, but both have been previously rejected for the Placerias Quarry population. The lack of strong dimorphism in non-maxilla elements and increased variation in caniniform length of the large-caniniform morph suggest that the caniniform is a secondary sexual trait, possibly used in intraspecific competition.

LINK(S)

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0297894

ABSTRACT

Belemnite rostra are very abundant in Mesozoic marine deposits in many regions. Despite this abundance, soft-tissue specimens of belemnites informing about anatomy and proportions of these coleoid cephalopods are extremely rare and limited to a few moderately large genera like Passaloteuthis and Hibolithes. For all other genera, we can make inferences on their body proportions and body as well as mantle length by extrapolating from complete material. We collected data of the proportions of the hard parts of some Jurassic belemnites in order to learn about shared characteristics in their gross anatomy. This knowledge is then applied to the Bajocian genus Megateuthis, which is the largest known belemnite genus worldwide. Our results provide simple ratios that can be used to estimate belemnite body size, where only the rostrum is known.

LINK(S)

https://sjpp.springeropen.com/articles/10.1186/s13358-024-00320-x
https://sjpp.springeropen.com/counter/pdf/10.1186/s13358-024-00320-x.pdf

ABSTRACT

Hypercanines are here defined as hypertrophied caniniform teeth, that is, canine teeth that are elongated to serve specific functions in different clades of mammals and their synapsid ancestors. This article presents an overview of the occurrence of hypercanines, their growth, and their function across a broad range of clades. Sabertooth felids and felid-like taxa are found to be unique in having determinate growth (although some Dinocerata may also have this). The most common function of hypercanines among herbivores is found to be sexual display and male–male competition. Three clades of small ruminants have evolved hypercanines that can move within their sockets, although the evolutionary details behind this convergent adaptation have not been worked out.

LINK(S)

https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25510
https://anatomypubs.onlinelibrary.wiley.com/doi/epdf/10.1002/ar.25510

ABSTRACT

An articulated partial hind limb collected from the Pebbly Arkose Formation (Norian, Upper Triassic) of the Upper Karoo Group of Zimbabwe is described as a new taxon of sauropodomorph dinosaur. Musankwa sanyatiensis gen. et sp. nov. was discovered on the shoreline of Lake Kariba, on Spurwing Island in the Mid-Zambezi Basin. The holotype consists of a right femur, tibia, and astragalus, and can be distinguished from all other Late Triassic massopodan sauropodomorphs on the basis of numerous features, which form a unique character combination. Phylogenetic analysis recovers the new taxon as the earliest-branching lineage within Massopoda. Musankwa is only the fourth dinosaur to be named from the Karoo-aged basins of Zimbabwe and further demonstrates the high potential of this region for discoveries of new early dinosaur material.

LINK(S)

https://www.app.pan.pl/article/item/app011002023.html
https://www.app.pan.pl/archive/published/app69/app011002023.pdf

ABSTRACT

Ankylosaurs are a characteristic group of dinosaurs recognised by their extensive coverings of dermal bony armour, known as osteoderms, across their bodies. The Oxford Clay Formation (Callovian–Oxfordian, Middle Jurassic) in the UK is important for understanding early ankylosaur evolution as it contains some of the earliest known ankylosaur material, including a cranial osteoderm from the basal-most ankylosaur Sarcolestes (and probable postcranial osteoderms). Here, we describe an isolated osteoderm from the Oxford Clay of Peterborough that exhibits a different morphology to other osteoderms from this formation. The specimen, although incomplete along its transverse axis, measures 52.7 mm by 41 mm. The osteoderm is subrectangular with a concave ventral surface and a low, rounded keel on its dorsal surface that protrudes beyond the posterior margin of the specimen base. This morphology is superficially more similar to the thoracic osteoderms of more derived Cretaceous ankylosaurs from North America (e.g. Borealopelta), than to Sarcolestes and other Jurassic ankylosaurs (e.g. Dracopelta, Mymoorapelta, Tianchisaurus), but could represent a currently unknown Sarcolestes morphology. Although its isolated nature prevents reliable identification of the taxon and the body part to which it belonged, the osteoderm nevertheless indicates a larger morphological diversity in the body armour of the earliest ankylosaurs than currently appreciated.

LINK(S)

https://www.lyellcollection.org/doi/abs/10.1144/pygs2023-011

ABSTRACT

The extinction of the massive apex predator †Otodus megalodon during the Pliocene is a subject of debate, with climate change and emergence of competitors as potential factors, such as Carcharodon carcharias. We explore trophic interactions of †O. megalodon and the C. carcharias by the analysis of dental microwear. For this purpose, high-resolution casts were made from ten megalodon teeth and six white shark teeth. Then, replicas were produced for examination using a Scanning Electron Microscope. Following a previous work on non-occlusal teeth of bony fishes, density and scratch length as well as mean vector were taken into account for the analysis. Our findings revealed that †O. megalodon shows a slight preference for less abrasive diets compared to C. carcharias. However, no significant differences were found in the dental microwear patterns of both species. These results provide additional evidence of a similar trophic spectrum between C. carchariasand †O. megalodon in the Mediterranean Sea basin, contrasting with previous data obtained through texture analysis. However, due to the inability to estimate sizes, we cannot rule out possible ontogenetic dietary differences. Therefore, future studies estimating sizes and incorporating data from other basins could provide more information.

LINK(S)

https://ojs.uv.es/index.php/sjpalaeontology/article/view/28830

ABSTRACT

Six species of monotremes, three newly described here, occur in the Cenomanian fossil fauna from Lightning Ridge in northeastern New South Wales, Australia, making it the most diverse monotreme assemblage on record. Four species are known from a single specimen, suggesting that diversity remains underrepresented. No other mammal lineages are known from the deposit, although the absence of smaller taxa is likely due to sampling biases introduced by the opal mining process. Early-Late Cretaceous monotremes thus clearly diversified in Australia during the absence of other large-bodied mammalian competitors; and subsequently occupied a wider range of ecological niches than at any other time in their evolutionary history. One new taxon described herein represents a previously unknown monotreme family that combines marked elongation and torsion of the dentary with teinolophid character states, including the retention of five molars. Another shares dental features with ornithorhynchids, while the third is a possible diminutive steropodontid and simultaneously represents the smallest-bodied post-Barremian monotreme. Additional material of Steropodon galmani is also documented, confirming that a Meckelian groove is rudimentary or absent in this taxon, thus adding to the morphological understanding of this unusual monotreme. Lastly, we posit that the loss of teeth in ornithorhynchids may have occurred during the Pleistocene as a result of competition with aquatic hydromyin rodents dispersing to Australia from New Guinea.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/03115518.2024.2348753
https://www.tandfonline.com/doi/pdf/10.1080/03115518.2024.2348753?needAccess=true

ABSTRACT

The endemic Hupehsuchia from the Early Triassic of South China is generally accepted as the sister group of ichthyosauriforms and represents the only ichthyosauromorph that lived mainly in the shallow aquatic environment. Therefore, the detailed morphological study of basal hupehsuchians is important to elucidate the relationships of Ichthyosauromorpha with other reptiles. However, Nanchangosaurus, the most basal hupehsuchian taxon, is represented by only two skeletons, and the morphology of its palate and most of the appendicular skeleton remains unknown, limiting its role in resolving the phylogenetic relationships of Ichthyosauromorpha. Here we report a new hupehsuchian specimen from the Early Triassic of South China, which we have identified as a new morphotype of Nanchangosaurus. The new skeleton shows for the first time the morphology of the palate, zeugopodium and autopodium in Nanchangosaurus. Phylogenetic analyses including new morphological information from this skeleton support the recent recovery of an aquatic clade that includes the three major Triassic marine reptile groups. A clade comprising Helveticosaurus and Sauropterygomorpha forms the sister group to Ichthyosauromorpha, and Thalattosauria occupies the most basal position in this large aquatic clade. Archosauromorpha is recovered as a sister group to this aquatic clade, and together they form part of a monophyletic Archelosauria.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2354791

ABSTRACT

The fossil remains of a pterodactyloid pterosaur from the Kimmeridge Clay Formation (Jurassic: Tithonian) of Abingdon, Oxfordshire, central England are identified as a partial left first wing finger phalanx. The elongation of the phalanx and distinctive morphology of the proximal articular region, in particular the square outline of the extensor tendon process, permit the specimen to be assigned to Ctenochasmatoidea. Although fragmentary, it is sufficiently well preserved to determine accurately its dimensions when complete. Morphometric analysis reveals the specimen to represent one of the largest known examples of a Jurassic pterosaur, with an estimated wingspan of at least 3 m, and is one of the first pterodactyloids to be reported from the Jurassic of the United Kingdom.

LINK(S)

https://www.sciencedirect.com/science/article/pii/S0016787824000191?via%3Dihub

ABSTRACT

Plateosaurus von Meyer, Citation1837, from the Norian of central Europe, was one of the first named dinosaurs. With close to 200 referred specimens found all over central Europe, it is one of the best-known dinosaurs from Europe. Over the past 200 years it has become one of the most important sauropodomorph dinosaurs and is used in many comparative studies in almost all fields of dinosaur palaeontology. Here we present a full osteological redescription of the holotype of Plateosaurus trossingensis, the almost entirely complete, historic specimen SMNS 13200. We use it as a basis for a revised diagnosis of P. trossingensis that consists of autapomorphies in a unique combination of features. An updated phylogeny of basal sauropodomorph taxa, with P. trossingensis restricted to the holotype, recovers P. trossingensis within Plateosauridae together with Sellosaurus and Unaysaurus. The revised anatomy and cladistic scoring can be used in many future studies involving comparative anatomy, phylogenetics, biostratigraphy and early dinosaur evolution.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/14772019.2024.2335387
https://www.tandfonline.com/doi/pdf/10.1080/14772019.2024.2335387?needAccess=true

ABSTRACT

Neanderthals’ lives were historically portrayed as highly stressful, shaped by constant pressures to survive in harsh ecological conditions, thus potentially contributing to their extinction. Recent work has challenged this interpretation, leaving the issue of stress among Paleolithic populations highly contested and warranting in-depth examination. Here, we analyze the frequency of dental enamel hypoplasia, a growth disruption indicator of early life stress, in the largest sample of Neanderthal and Upper Paleolithic dentitions investigated to date for these features. To track potential species-specific patterns in the ontogenetic distribution of childhood stress, we present the first comprehensive Bayesian modelling of the likelihood of occurrence of individual and matched enamel growth disruptions throughout ontogeny. Our findings support similar overall stress levels in both groups but reveal species-specific patterns in its ontogenetic distribution. While Neanderthal children faced increasing likelihoods of growth disruptions starting with the weaning process and culminating in intensity post-weaning, growth disruptions in Upper Paleolithic children were found to be limited around the period of weaning and substantially dropping after its expected completion. These results might, at least in part, reflect differences in childcare or other behavioral strategies between the two taxa, including those that were advantageous for modern humans’ long-term survival.

LINK(S)

https://www.nature.com/articles/s41598-024-61321-x
https://www.nature.com/articles/s41598-024-61321-x.pdf

ABSTRACT

The water-living reptile genus Hyphalosaurus was previously discovered in the Lower Cretaceous Yixian Formation bearing the middle Jehol Biota in western Liaoning, China. Two complete skeletons of Hyphalosaurus are reported for the first time from the Jiufotang Formation bearing the late Jehol Biota at two sites in western Liaoning. They show the typical characteristics of H. baitaigouensis in terms of the contact between some cranial bones and the number of cervical and dorsal vertebrae, and therefore are assigned to H. baitaigouensis. This discovery extends the stratigraphic range of this species from the Yixian Formation to the overlying Jiufotang Formation. This paper further briefly compares the main characteristics of the two skeletons, summarizes the temporal and spatial distribution of Hyphalosaurus, and discusses the palaeogeographic evolution of western Liaoning at the middle and late Jehol Biota stages based on the aquatic habits of Hyphalosaurus and the geological background of western Liaoning. The analytical results show that the volcanic downwarped lakes, with distinct geographical divisions in western Liaoning during the deposition of the Yixian Formation, had not completely disappeared till the deposition of the Jiufotang Formation. The palaeo-lake in the Fuxin-Yixian Basin underwent the process of generation, expansion and shrinkage during the depositional period of the Yixian Formation and finally merged into a large lake. The palaeo-Dalinghe River, which connected the main basins in western Liaoning during the depositional period of the Jiufotang Formation, was formed simultaneously.

LINK(S)

https://www.sciencedirect.com/science/article/pii/S2095383624000373

ABSTRACT

The Indo-West Pacific is home to a diverse array of modern fish species, and the study of their fossils can provide valuable insights into the origins and evolution of this biodiversity. This report presents rare remains of five individuals of acropomatiform fish, including a semi-articulated skeleton, recovered from the Upper Kueichulin Formation (Lower Pliocene) in northern Taiwan. The fossils are preserved in the form of nodules discovered at the locality known for abundant marine crustaceans and echinoderms. These specimens can be assigned to the family Stereolepididae, based on morphology of the opercle with the presence of two spines, a preopercle characterized by serrations on the posterior margin and denticulations on the ventral margin, and a distinctive skull architecture. Differences in skull morphology distinguish these specimens from other species within the genus and thus are described as Stereolepis arcanum n. sp. Significantly, the species represents the oldest known record of the family globally and stands as the second known fossil representative. This discovery not only enhances our understanding of the palaeobiodiversity of fish fauna in the Indo-West Pacific during the Neogene, but also highlights the importance of further research efforts in this area.

LINK(S)

https://riviste.unimi.it/index.php/RIPS/article/view/22639

ABSTRACT

Corneous skin appendages are not only common and diverse in crown-group amniotes but also present in some modern amphibians. This raises the still unresolved question of whether the ability to form corneous skin appendages is an apomorphy of a common ancestor of amphibians and amniotes or evolved independently in both groups. So far, there is no palaeontological contribution to the issue owing to the lack of keratin soft tissue preservation in Palaeozoic anamniotes. New data are provided by a recently discovered ichnofossil specimen from the early Permian of Poland that shows monospecific tetrapod footprints associated with a partial scaly body impression. The traces can be unambiguously attributed to diadectids and are interpreted as the globally first evidence of horned scales in tetrapods close to the origin of amniotes. Taking hitherto little-noticed scaly skin impressions of lepospondyl stem amniotes from the early Permian of Germany into account, the possibility has to be considered that the evolutionary origin of epidermal scales deeply roots among anamniotes.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsbl.2024.0041

ABSTRACT

The accurate identification of dinosaur egg accumulations as nests or clutches is crucial for understanding the reproductive behaviour of these extinct species. However, existing methods often rely on the presence of complete eggs and embryo remains, and sedimentological criteria that are only applicable to well-structured sediments. In this study, we introduce an innovative approach to characterize egg accumulations in structureless sediments, where traditional nest structures may not be preserved. Our methodology employs a unique combination of sedimentological, taphonomic, geochemical, and geophysical proxies for the study of egg accumulations. We applied this approach to the egg accumulation from Paimogo (Jurassic, Portugal), traditionally interpreted as a nest. Our findings reveal that the Paimogo egg assemblage is a secondary deposit, resulting from a flooding event in a fluvial plain that dismantled several allosauroid and crocodylomorph clutches. The eggshell vapor conductance results, coupled with sedimentological evidence, suggest that allosauroid dinosaurs buried their eggs in the dry terrain of overbank areas close to a main channel during the breeding season, likely during the dry season to prevent the embryos from drowning. This research underscores the necessity of multidisciplinary approaches in interpreting egg accumulations and offers a novel methodology for studying these accumulations in structureless sediments. Our findings provide new insights into the breeding behaviour and nesting preferences of these extinct organisms, contributing to our understanding of dinosaur ecology.

LINK(S)

https://www.sciencedirect.com/science/article/pii/S1674987124000963

ABSTRACT

We here report an anterior trunk vertebra of a large snake that we tentatively refer to Palaeophis africanus. The vertebra comes from lower middle Eocene deposits of the El Breij Depression, in the Sahara Desert of southern Morocco. It is principally characterised by weak lateral compression; horizontality of the cotyle-condyle axis; dorsoventrally thick zygosphene; lower pterapophyses with an upper edge that remains lower than that of the zygosphene in lateral view; a rather reduced neural canal; very distinct and prominent interzygapophyseal crests; low position of the diapophyses; and the presence of two hypapophyses. This occurrence adds to the geographic distribution of Palaeophis africanus, which has been formerly identified from Nigeria, Togo, Angola, and South America, and represents an additional Palaeophis species for the Moroccan fossil record.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2352863

ABSTRACT

Based on high-resolution computed tomography scanning, we provide new insights into the inner ear and stapedial morphology of Morganucodon from the Early Jurassic of St Brides. At the base of mammaliaforms, Morganucodon plays a pivotal role in understanding the sequence of character acquisition from basal cynodonts to mammals, including the detachment of the middle ear and the evolution of high-frequency hearing. Advancements in imaging technology enabled us to revise or newly describe crucial anatomy that was not accessible for the original description of Morganucodon. Based on 37 petrosals, we can confirm that the apex of the cochlear canal is expanded in Morganucodon, suggestive of a lagena macula. A gently raised crest along the abneural margin is reminiscent of (although much shallower than) the secondary lamina base of other Mesozoic mammaliaforms. The venous circum-promontorial plexus, which surrounded the inner ear in several basal mammaliaforms, was connected to the cochlear labyrinth in Morganucodon through numerous openings along the secondary lamina base. Two petrosals contain fragmentary stapes, which differ substantially from previously described isolated stapes attributed to Morganucodon in having peripherally placed crura and an oval and bullate footplate. Based on the revised stapedial morphology, we question the traditional view of an asymmetrical bicrural stapes as the plesiomorphic condition for Mammaliaformes.

LINK(S)

https://academic.oup.com/zoolinnean/advance-article-abstract/doi/10.1093/zoolinnean/zlae062/7678887?redirectedFrom=fulltext

ABSTRACT

Fossil feathers have transformed our understanding of integumentary evolution in vertebrates. The evolution of feathers is associated with novel skin ultrastructures, but the fossil record of these changes is poor and thus the critical transition from scaled to feathered skin is poorly understood. Here we shed light on this issue using preserved skin in the non-avian feathered dinosaur Psittacosaurus. Skin in the non-feathered, scaled torso is three-dimensionally replicated in silica and preserves epidermal layers, corneocytes and melanosomes. The morphology of the preserved stratum corneum is consistent with an original composition rich in corneous beta proteins, rather than (alpha-) keratins as in the feathered skin of birds. The stratum corneum is relatively thin in the ventral torso compared to extant quadrupedal reptiles, reflecting a reduced demand for mechanical protection in an elevated bipedal stance. The distribution of the melanosomes in the fossil skin is consistent with melanin-based colouration in extant crocodilians. Collectively, the fossil evidence supports partitioning of skin development in Psittacosaurus: a reptile-type condition in non-feathered regions and an avian-like condition in feathered regions. Retention of reptile-type skin in non-feathered regions would have ensured essential skin functions during the early, experimental stages of feather evolution.

LINK(S)

https://www.nature.com/articles/s41467-024-48400-3
https://www.nature.com/articles/s41467-024-48400-3.pdf

ABSTRACT

Gondwanan dinosaur faunae during the 20 Myr preceding the Cretaceous–Palaeogene (K/Pg) extinction included several lineages that were absent or poorly represented in Laurasian landmasses. Among these, the South American fossil record contains diverse abelisaurids, arguably the most successful groups of carnivorous dinosaurs from Gondwana in the Cretaceous, reaching their highest diversity towards the end of this period. Here we describe Koleken inakayali gen. et sp. n., a new abelisaurid from the La Colonia Formation (Maastrichtian, Upper Cretaceous) of Patagonia. Koleken inakayali is known from several skull bones, an almost complete dorsal series, complete sacrum, several caudal vertebrae, pelvic girdle and almost complete hind limbs. The new abelisaurid shows a unique set of features in the skull and several anatomical differences from Carnotaurus sastrei (the only other abelisaurid known from the La Colonia Formation). Koleken inakayali is retrieved as a brachyrostran abelisaurid, clustered with other South American abelisaurids from the latest Cretaceous (Campanian–Maastrichtian), such as Aucasaurus, Niebla and Carnotaurus. Leveraging our phylogeny estimates, we explore rates of morphological evolution across ceratosaurian lineages, finding them to be particularly high for elaphrosaurine noasaurids and around the base of Abelisauridae, before the Early Cretaceous radiation of the latter clade. The Noasauridae and their sister clade show contrasting patterns of morphological evolution, with noasaurids undergoing an early phase of accelerated evolution of the axial and hind limb skeleton in the Jurassic, and the abelisaurids exhibiting sustained high rates of cranial evolution during the Early Cretaceous. These results provide much needed context for the evolutionary dynamics of ceratosaurian theropods, contributing to broader understanding of macroevolutionary patterns across dinosaurs.

LINK(S)

https://onlinelibrary.wiley.com/doi/10.1111/cla.12583
https://onlinelibrary.wiley.com/doi/pdf/10.1111/cla.12583

ABSTRACT

We live in a time of accelerated biological extinctions that has the potential to mirror past mass extinction events. However, the rarity of mass extinctions and the restructuring of diversity they cause complicate direct comparisons between the current extinction crisis and earlier events. Among animals, turtles (Testudinata) are one of few groups that have both a rich fossil record and sufficiently stable ecological and functional roles to enable meaningful comparisons between the end-Cretaceous mass extinction (∼66 Ma) and the ongoing wave of extinctions. Here we analyze the fossil record of the entire turtle clade and identify two peaks in extinction rates over their evolutionary history. The first coincides with the Cretaceous-Paleogene transition, reflecting patterns previously reported for other taxa. The second major extinction event started in the Pliocene and continues until now. This peak is detectable only for terrestrial turtles and started much earlier in Africa and Eurasia than elsewhere. On the basis of the timing, geography, and functional group of this extinction event, we postulate a link to co-occurring hominins rather than climate change as the cause. These results lend further support to the view that negative biodiversity impacts were already incurred by our ancestors and related lineages and demonstrate the severity of this continued impact through human activities.

LINK(S)

https://www.journals.uchicago.edu/doi/10.1086/729604

ABSTRACT

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

LINK(S)

https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlae056/7676115

https://watermark.silverchair.com/zlae056.pdf?token=AQECAHi208BE49Ooan9kkhW_Ercy7Dm3ZL_9Cf3qfKAc485ysgAAA3owggN2BgkqhkiG9w0BBwagggNnMIIDYwIBADCCA1wGCSqGSIb3DQEHATAeBglghkgBZQMEAS4wEQQMjlp8g2qKWkTzpl0UAgEQgIIDLY-xYZtofzAWfT_r8i90EQpZpPSI7y10gsKBs2JSqi6apuMG1AdfpSatD-e2q3G7Yi6lRD3TDXCJxpSJWDurdksKIfTmD2tCZMJwL0E3PLHrqqqggdvLWFB4AIwJwZEm2wlfdV0M7-euX8fpmoXB0JMTFGgft9BfHgt-hL4XpAtSSlJ_KrnWppI0DkOUUitUH23jTsPkWPZMGF3M6pGyIyJ9MaRH2mMNAPHtc4htgDKF0Mvk_atkf50qs-ZSE32Q3nh4kP_GDQ8XSqcuyS880fgdGppmUBsvDCcSzujke8ReUrce6_YRFSrwRnYajFKdbULbrsVPy-46aMcMmrik1XbwxnD59JKeKxI_s74Mumh3xgK09mXOOYSIuHjiR4UlhI5O1CvLrdHGp7SsVTaw4JpHRn-5f0xa3cuu0l1_Wl3Zg4Q4qUOnpPCxgqM3EwX0vzuJfPA3E_3OIQLSaXvIFHIOXBYEiMIJcQQF3HoKuACZUcSAeeJjkDZPf9hacflc-WZeNh-AdVho51T3t_iTZyIy_ADsvinvRyjUCzgXTmTaQv6a9bc2A4y6jfUc7pWJCQ2Te8au-PFIQlXZKZc6pSCaQy1WYeF6sCiYz79OWJ8m_YV2PU51Z3DccmY29YmPDFFnOpxnT32heKenDwaCGsxSXxNqFFlm6MJUKFT8gK-AY-K7FP6VqW6OG0Y9fOyHGsrRCnNL-8KtZFTapb-HgX3akVulXxuZ7e-iAUPlrewMWhYshOn3P5xF2TFDsgqPVHf5zT-HGQVNvOPTIHGUWRXr30h6finhr9sROsh5r4uzCFUTSe3h4azKpXAU1l7shoSZrT_ARKG44N3oTAeHCjNZBrdXvzqTYvse3Qfdt7-1gd5GGZqixuTV0t19wHg2uQ1WU0Bu8KCywdPwZ2wsoMbA6Z0WpHZr9QYKWeX1kZko_-Jtmk8vNacBtWOGVJJgdOkuPqtHucX-RcBa8bt54WLlz2H9TtYPKzSm3sV3abLUb9C2GQCD020HbUxxmSRDF8fuDosct8rL-x6EOVNMtSXFafNSsUQD1NDmETpKZ-mFfYYvDo9lmZjxI56MwQ

ABSTRACT

Plesiadapiforms (putative stem primates) appear in the fossil record shortly after the Cretaceous/Paleogene boundary and subsequently radiated throughout the Paleocene into a taxonomically and ecomorphologically diverse group. The oldest known plesiadapiforms come from early Puercan (the oldest North American Land Mammal ‘age’ [NALMA] of the Cenozoic) deposits in northeastern Montana, and all records of Puercan plesiadapiforms are taxonomically restricted to members of the Purgatoriidae and the enigmatic genus Pandemonium. Plesiadapiform diversity substantially increased in the following Torrejonian NALMA, but the sparse record of faunas between the Puercan and the well-known middle and late Torrejonian has hampered our understanding of this important interval in early primate evolution. Here we report new plesiadapiform dental fossils from early Torrejonian (To1) deposits from the Tullock Member of the Fort Union Formation in northeastern Montana that record several poorly known taxa including members of the Purgatoriidae, Paromomyidae and Pandemonium, and that document the largest and most diverse assemblage of To1 plesiadapiforms known. We describe a new species of the purgatoriid Ursolestes (Ursolestes blissorum, sp. nov.) that represents the largest plesiadapiform known from the early Paleocene and, among other taxa, provides additional evidence that the temporal range of purgatoriids extended into the Torrejonian. Large sample sizes of the oldest known paromomyid, Paromomys farrandi, allowed us to document intraspecific variability and one undescribed tooth locus. Our observations illuminate changes in dental morphology of some taxa that occurred in To1 and may inform the acquisition of certain diagnostic plesiadapiform dental characters. We evaluate plesiadapiform species richness, mean body mass and body-mass disparity through the Paleocene and reveal unrecognized levels of richness in To1 and a general trend of stable body mass and body-mass disparity. Our findings contribute to documented patterns of plesiadapiform provincialism in the early Paleocene and shed light on the early stages of their Torrejonian radiation.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0047248424000083?via%3Dihub

ABSTRACT

The rise of animals across the Ediacaran–Cambrian transition marked a step-change in the history of life, from a microbially dominated world to the complex macroscopic biosphere we see today.1,2,3 While the importance of bioturbation and swimming in altering the structure and function of Earth systems is well established,4,5,6 the influence of epifaunal animals on the hydrodynamics of marine environments is not well understood. Of particular interest are the oldest “marine animal forests,”7 which comprise a diversity of sessile soft-bodied organisms dominated by the fractally branching rangeomorphs.8,9 Typified by fossil assemblages from the Ediacaran of Mistaken Point, Newfoundland,8,10,11 these ancient communities might have played a pivotal role in structuring marine environments, similar to modern ecosystems,7,12,13 but our understanding of how they impacted fluid flow in the water column is limited. Here, we use ecological modeling and computational flow simulations to explore how Ediacaran marine animal forests influenced their surrounding environment. Our results reveal how organism morphology and community structure and composition combined to impact vertical mixing of the surrounding water. We find that Mistaken Point communities were capable of generating high-mixing conditions, thereby likely promoting gas and nutrient transport within the “canopy.” This mixing could have served to enhance local-scale oxygen concentrations and redistribute resources like dissolved organic carbon. Our work suggests that Ediacaran marine animal forests may have contributed to the ventilation of the oceans over 560 million years ago, well before the Cambrian explosion of animals.

LINK(S)

https://www.cell.com/current-biology/fulltext/S0960-9822(24)00533-5
https://www.cell.com/current-biology/pdf/S0960-9822(24)00533-5.pdf

ABSTRACT

The Great American Biotic Interchange (GABI) was a remarkable biogeographic event of biodiversity exchange between North and South America. Climate change has been pointed to as one of the main factors driving species dispersal across the continent, although this hypothesis has not been tested thus far. Here, we use paleontological ecological niche models (PaleoENMs) throughout the last five million years to test if climate change triggered the dispersal of mammalian species and/or caused the extinction of dispersing species during the GABI. We used extant and fossil occurrences for 189 mammalian species related to the GABI along with paleoclimate data to obtain species distributions from PaleoENMs. We calculated dispersal and extinction rates between North, Central, and South America and applied quantile regression models to test the effect of climatic anomalies in these rates. Our results indicate that temperature change, particularly cooling, triggered mammal dispersals during the GABI. On the other hand, we found the extinction rate in South America to be caused by warming. We recognize that the GABI is a complex event and that several factors likely affected it. Nonetheless, our results indicate that climate was one of these factors.

LINK(S)

https://link.springer.com/article/10.1007/s10914-024-09717-4

ABSTRACT

Mawsonia constitutes one of the most conspicuous fossil coelacanth taxa, due to its unique anatomy and possible maximum body size. It typifies Mesozoic coelacanth morphology, before the putative disappearance of the group in the fossil record. In this work, the three-dimensional cranial anatomy and body size estimations of this genus are re-evaluated from a recently described specimen from Upper Jurassic deposits of Uruguay. The 3D restoration was performed directly on the material based on anatomical information provided by the living coelacanth Latimeria and previous two-dimensional restorations of the head of Mawsonia. The montage was then scanned with computed tomography and virtually adjusted to generate an interactive online resource for future anatomical, taxonomic and biomechanical research. In general terms, the model constitutes a tool to improve both the anatomical knowledge of this genus and its comparison with other coelacanths. It also facilitates the evaluation of possible evolutionary trends and the discussion of particular features with potential palaeobiological implications, such as the anterior position of the eye and the development of the pseudomaxillary fold. Regarding the body size, a previous model for body size estimation based on the gular plate was submitted to OLS, RMA, segmented linear and PGLS regressions (including the evaluation of regression statistics, variance analysis, t-tests and residual analysis). The results point to a power relationship between gular and total lengths showing a better support than a simple linear relationship. The new resulting equations were applied to the studied individual and are provided for future estimates. Although an isometric evolutionary growth cannot be rejected with the available evidence, additional models developed with other bones will be necessary to evaluate possible hidden evolutionary allometric trends in this group of fishes, thus avoiding overestimates.

LINK(S)

https://onlinelibrary.wiley.com/doi/abs/10.1111/joa.14054

ABSTRACT

A fundamental question in dinosaur evolution is how they adapted to long-term climatic shifts during the Mesozoic and when they developed environmentally independent, avian-style acclimatization, becoming endothermic.1,2 The ability of warm-blooded dinosaurs to flourish in harsher environments, including cold, high-latitude regions,3,4 raises intriguing questions about the origins of key innovations shared with modern birds,5,6 indicating that the development of homeothermy (keeping constant body temperature) and endothermy (generating body heat) played a crucial role in their ecological diversification.7 Despite substantial evidence across scientific disciplines (anatomy,8 reproduction,9 energetics,10 biomechanics,10 osteohistology,11 palaeobiogeography,12 geochemistry,13,14 and soft tissues15,16,17), a consensus on dinosaur thermophysiology remains elusive.1,12,15,17,18,19 Differential thermophysiological strategies among terrestrial tetrapods allow endotherms (birds and mammals) to expand their latitudinal range (from the tropics to polar regions), owing to their reduced reliance on environmental temperature.20 By contrast, most reptilian lineages (squamates, turtles, and crocodilians) and amphibians are predominantly constrained by temperature in regions closer to the tropics.21 Determining when this macroecological pattern emerged in the avian lineage relies heavily on identifying the origin of these key physiological traits. Combining fossils with macroevolutionary and palaeoclimatic models, we unveil distinct evolutionary pathways in the main dinosaur lineages: ornithischians and theropods diversified across broader climatic landscapes, trending toward cooler niches. An Early Jurassic shift to colder climates in Theropoda suggests an early adoption of endothermy. Conversely, sauropodomorphs exhibited prolonged climatic conservatism associated with higher thermal conditions, emphasizing temperature, rather than plant productivity, as the primary driver of this pattern, suggesting poikilothermy with a stronger dependence on higher temperatures in sauropods.

LINK(S)

https://www.cell.com/current-biology/fulltext/S0960-9822(24)00525-6

ABSTRACT

The Triassic radiation of vertebrates saw the emergence of the modern vertebrate groups, as well as numerous extinct animals exhibiting conspicuous, unique anatomical characteristics. Among these, members of Tanystropheidae (Reptilia: Archosauromorpha) displayed cervical vertebral elongation to an extent unparalleled in any other vertebrate. Tanystropheids were exceptionally ecologically diverse and had a wide spatial and temporal distribution. This may have been related to their neck anatomy, yet its evolution and functional properties remain poorly understood. We used geometric morphometrics to capture the intraspecific variation between the vertebrae comprising the cervical column among early archosauromorphs, to trace the evolutionary history of neck elongation in these animals. Our results show that the cervical series of these reptiles can be divided into modules corresponding to those of extant animals. Tanystropheids achieved neck elongation through somite elongation and a shift between cervical and thoracic regions, without presacral vertebrae count increase—contrary to crown archosaurs. This suggests a peculiar developmental constraint that strongly affected the evolution of tanystropheids. The data obtained just at the base of the archosauromorph phylogenetic tree are crucial for further studies on the modularity of vertebral columns of not only Triassic reptile groups but extant and other extinct animals as well.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsos.240233?fbclid=IwZXh0bgNhZW0CMTAAAR3DUmOea9NPau7CxrnwFEmy6gwhfkdTDmwqFIxRycVQLvJ1yHswg6tDkk0_aem_AaksQRyCOhOdn5D8pvbQ81OdtRlyms9dzIm7cY4GIouulMGKJ9HKdbJpboLE433SR_Z_pu9eDy7cw4O3VFxNJVkK

ABSTRACT

This work describes and interprets fossil lagomorphs from seven sites in the Maghreb the ages of which range from the Miocene/Pliocene boundary to the Upper Pleistocene. Some of these sites, such as the Thomas Quarries in Morocco and Tighennif (=Ternifine) in Algeria, are well known for the discovery of fossil humans and their artefacts. The lagomorphs studied herein belong to two families, Prolagidae and Leporidae. The genus Prolagus has been recorded in the Maghreb since the latest Miocene, c. 6.2-6.5 Ma, and its last known representatives in Africa occur at Tighennif and Djebel Ressas 5 and 6 (Tunisia) the ages of which are estimated to be between 1.0 and 1.4 Ma. In other words, this genus, which is well known in Europe since the Early Miocene, crossed the Rifian Corridor during the Messinian crisis, and became extinct in the Maghreb earlier than in southwestern Europe where it survived until historical times. Its oldest representatives in the Maghreb known from the sites of Afoud and Lissasfa (latest Miocene-Early Pliocene) are related to P. michauxi, a species that is well represented in the latest Miocene and Early Pliocene localities in southern Europe. In the Early Pleistocene of Djebel Ressas 1 (Tunisia), it is represented by a new small species, Prolagus ressasensis n. sp. Prolagus is known in Europe as an inhabitant of wooded and humid environments. But in the terminal Miocene and Plio-Pleistocene this genus was confined more particularly to the Mediterranean rim, probably as an inhabitant of open woodland, temperate regions and certainly more open than the humid and wooded environments of the Early and Middle Miocene of Europe. The Leporidae appear in the Maghreb sites around the same time as Prolagus, but in the earlier sites (Afoud and Lissasfa), they are rare and therefore their identification is imprecise (Leporidae indet. at Afoud, Trischizolagus sp. at Lissasfa). In contrast, they are abundant in terminal Pliocene and Pleistocene sites. The genus Trischizolagus, that is well documented at Ahl al Oughlam (c. 2.5-3.0 Ma) by T. meridionalis Sen and Geraads, 2023, is even more abundant in the deposits of the Casablanca region (Grotte des Rhinocéros, Thomas IL, Thomas I-GH) and in Tighennif in Algeria where it is represented by T. raynali (Geraads, 1994). The last known representatives of this genus, collected from Grotte des Rhinocéros, occur alongside the first known representatives of the genus Lepus, described here as Lepus berbericus n. sp. In the Late Pleistocene site of Thomas I, a form of Lepus similar to L. capensis is represented by numerous mandible fragments. But the systematics of this species are the subject of debate, with no consensus as to whether it is a species occurring over a wide range from South Africa to the Middle East and North Africa or whether it comprises several species of which the morphological and / or genetic features are poorly defined. The genus Trischizolagus is well known in Europe and Anatolia with several species described between 6.5 and 3.5 Ma, while it survived in the Maghreb until the Middle Pleistocene, c. 0.5 Ma. It was probably replaced by the first hares of the Maghreb, described here as L. berbericus n. sp. The extant species Lepus capensis inhabits territories with open grassland and bushland habitats. The introduction of the rabbit Oryctolagus cuniculus to the Maghreb occurred later, probably in the Late Pleistocene by prehistoric men for food.

LINK(S)

https://link.springer.com/article/10.1007/s12549-024-00605-6

ABSTRACT

At present, early-branching sauropodomorph dinosaurs from China are mainly discovered in the Lower Jurassic in Lufeng, Yunnan Province. A new specimen of the early-branching sauropodomorph from the Lufeng Formation of the Chuanjie Basin, Lufeng, including relatively complete cervical and dorsal vertebrae as well as a broken scapula, pubes and pedal elements, is described here. The osteological morphology of the new specimen is described in detail and compared with other early-branching sauropodomorphs. The specimen is more similar to that of Lufengosaurus than to other early-branching sauropodomorphs from the Lufeng Formation. Phylogenetic analysis recovers this specimen as a part of a polytomy with Coloradisaurus and Glacialisaurus, and they are referred to Massospondylidae along with Lufengosaurus. The unfused centrum and neural arch of the cervical and dorsal vertebrae of the new specimen indicate that the ontogenetic stage of this individual is juvenile–subadult. This discovery increases the diversity of Massospondylidae from Asia, and expands our knowledge of the Lufeng dinosaur fauna.

LINK(S)

http://gswxb.cnjournals.cn/gswxben/article/abstract/20240108

ABSTRACT

Titanosaurs were the most diverse sauropod group during the Cretaceous period, with most of its diversity being found during the Late Cretaceous. In this work, Tiamat valdecii, gen. et sp. nov. is described, a new species of basal titanosaur prospected from the Açu Formation (Albian–Cenomanian), Potiguar Basin, Ceará state, north-east Brazil. The new taxon is composed by an associated sequence of anterior to middle caudal vertebrae, being diagnosed by four diagnostic features: a marked accessory tuberosity dorsoventrally developed, located on the prezygapophyses; deeply medioventral excavated articulation facets of prezygapophysis and post-zygapophyses articular facets; presence of developed hypantrum–hyposphene articulations; and short middle centra with a well-marked articular facet for the haemal arch. The phylogenetic analysis reveals that Tiamat valdecii was a basal member of Titanosauria. Tiamat is the first species of Early Cretaceous titanosaur known for the Açu Formation. Biomechanical analysis shows that the tuberosity and excavation of the zygapophyses of the middle caudal vertebrae of Tiamat provide greater stability against shear loads in the amphicoelous vertebrae presented; in addition, they allow greater range of lateral movements without affecting the integrity of the joints. These features may have been an evolutionary alternative for the stability of the middle of the caudal vertebral column. The discovery of T. valdecii in the Açu Formation not only increases the known dinosaur diversity for this unit, but also helps us elucidate part of the first titanosaur radiation.

LINK(S)

https://academic.oup.com/zoolinnean/advance-article-abstract/doi/10.1093/zoolinnean/zlae054/7670994

ABSTRACT

For centuries, fossils from the Maastrichtian type locality and adjacent quarries have provided key evidence of vertebrate diversity during the latest Cretaceous, yet until recently the Maastrichtian type area had revealed no important insights into the evolutionary history of birds, one of the world’s most conspicuous groups of extant tetrapods. With the benefit of high-resolution micro-CT scanning, two important avian fossils from the Maastrichtian type area have now been examined in detail, offering profound, complementary insights into the evolutionary history of birds. The holotype specimens of these new taxa, Janavis finalidens Benito, Kuo, Widrig, Jagt and Field, 2022, and Asteriornis maastrichtensis Field, Benito, Chen, Jagt and Ksepka, 2020, were originally collected in the late 1990s, but were only investigated in detail more than twenty years later. Collectively, Janavis and Asteriornis provide some of the best evidence worldwide regarding the factors that influenced stem bird extinction and crown bird survivorship through the Cretaceous-Palaeogene transition, as well as insights into the origins of key anatomical features of birds such as an extensively pneumatised postcranial skeleton, a kinetic palate, and a toothless beak. Asteriornis also provides scarce evidence of a Cretaceous-aged divergence time calibration within the avian crown group, while together, Janavis and Asteriornis constitute the only documented co-occurrence of crown birds and non-neornithine avialans. Here, we review key insights into avian evolutionary history provided by these discoveries from the Maastrichtian stratotype, document undescribed and newly discovered Maastrichtian fossils potentially attributable to Avialae and provide the first histological data for the holotype of Asteriornis, illustrating its skeletal maturity at the time of its death.

LINK(S)

https://www.cambridge.org/core/journals/netherlands-journal-of-geosciences/article/remarkable-insights-into-modern-bird-origins-from-the-maastrichtian-type-area-northeast-belgium-southeast-netherlands/4DB9BBFF5FCE8275CD6190E4DF5FB2B3

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/4DB9BBFF5FCE8275CD6190E4DF5FB2B3/S0016774624000118a.pdf/div-class-title-remarkable-insights-into-modern-bird-origins-from-the-maastrichtian-type-area-north-east-belgium-south-east-netherlands-div.pdf

ABSTRACT

Our knowledge of marine reptiles of the Callovian age (Middle Jurassic) is majorly based on the collections from the Oxford Clay Formation of England, which yielded a diverse marine reptile fauna of plesiosaurians, ichthyosaurians, and thalattosuchians. However, outside of Western Europe, marine reptile remains of this age are poorly known. Here, we survey marine reptiles from the Callovian stage of European Russia. The fossils collected over more than a century from 28 localities are largely represented by isolated bones and teeth, although partial skeletons are also known. In addition to the previously described rhomaleosaurid and metriorhynchids, we identify pliosaurids of the genera Liopleurodon and Simolestes; cryptoclidid plesiosaurians, including Cryptoclidus eurymerus, Muraenosaurus sp., and cf. Tricleidus, and ophthalmosaurid ichthyosaurians, including the iconic Ophthalmosaurus icenicus. These findings expand the ranges of several Callovian marine reptile taxa far to the Eastern Europe, and support the exchange of marine reptile faunas between Western and Eastern European seas in the middle to late Callovian. However, some specimens from the lower Callovian of European Russia show differences from typical representatives of the middle Callovian Oxford Clay fauna, possibly representing the earlier stages of evolution of some of these marine reptiles not yet recorded in Western Europe or elsewhere.

LINK(S)

https://www.mdpi.com/1424-2818/16/5/290

ABSTRACT

The first record of well-preserved chondrocranial elements in mosasaurids is here described. These elements are preserved in situ in a Coniacian skull found in north-central Colombia, inside a calcareous concretion. Based on a 3D model generated from computed tomography scans, we identified elements of the nasal and orbitotemporal regions. Our descriptions show that in this specimen, the chondrocranium was reduced, more so than in most lacertilians (including their closest recent relatives, the varanids), but not as severely as in snakes or amphisbaenians (which have an extremely reduced chondrocranium and limbs). The new evidence suggests that the reduction in the chondrocranium in mosasaurids could be related to modification of their limbs when adapting to aquatic environments, but also that in mosasaurids, the olfactory tract was reduced, and the optic muscle insertions occurred mainly in the interorbital septum. The exceptional preservation of the chondrocranial elements in the specimen is facilitated by a gray mineralization covering them. XRD analysis and thin section observations indicated that this mineralization is composed of microcrystalline quartz and calcite. We infer that this material was produced by a partial silicification process promoted by lower pH microenvironments associated with bacterial breakdown of non-biomineralized tissues during early diagenesis.

LINK(S)

https://www.mdpi.com/1424-2818/16/5/285

ABSTRACT

Derived ornithopods, such as hadrosaurids, show a high occurrence of fossilized lesions and diseases. However, paleopathologies in iguanodontians seem to be less common, considering the rich fossil record of these taxa in Europe, in particular in Belgium, Britain and Spain. Here, we describe an iguanodontian femur discovered in England that exhibits a large overgrowth of its lateral aspect, not previously recognized in any other similar remains. The specimen was scanned with micro-computed tomography (microCT) and later sectioned in three sites of the overgrowth for histological analysis. The femur belongs to an early adult Iguanodontia indet., based on the presence of a woven parallel fibered complex in the outer cortex and three to four lines of arrested growth. Internal analysis of the dome-like overgrowth suggests it can be diagnosed as a fracture callus. The injury might have negatively impacted upon the animal's locomotion as the trauma had occurred in the region above the knee, a crucial spot for hindlimb musculature. Finally, a cancellous medullary bone-like tissue was recognized in the medullary cavity next to the pathological overgrowth. An attempt was made to determine the precise nature of this tissue, as medullary bone is linked with the ovulation period in (avian) dinosaurs, whereas other types of endosteal, medullary bone-like tissue have previously been recognized in pathological bones.

LINK(S)

https://onlinelibrary.wiley.com/doi/10.1111/joa.14053

ABSTRACT

The study of thirty-two shed crowns from the Portezuelo Formation (middle Turonian-late Coniacian) at the Sierra del Portezuelo locality, reveals six distinct tooth morphotypes identified through cladistic, discriminant, and cluster analyses. Two morphotypes were identified as belonging to Megaraptoridae, three to Abelisauridae, one to Abelisauroidea, and one to Alvarezsauridae. Additionally, two of the morphotypes exhibit a combination of dental features typically found in megaraptorid and abelisauridtheropods. These results suggest a greater diversity of theropods in the original ecosystem than previously thought, including the presence of a second morphotype of megaraptorid and alvarezsaurid previously undocumented in this formation. Furthermore, the existence of Morphotype 6 indicates the potential coexistence of medium-sized abelisauroids alongside larger abelisaurids in the same ecosystem. These findings underscore the importance of future expeditions to the Sierra del Portezuelo locality to further our understanding of these previously unknown theropod species.

LINK(S)

https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-024-02249-8
https://bmcecolevol.biomedcentral.com/counter/pdf/10.1186/s12862-024-02249-8.pdf

ABSTRACT

Eocene penguins from Seymour Island play an important role in studies related to the taxonomy and evolution of the Sphenisciformes stem group. Among these penguins, the Palaeeudyptes species are particularly noteworthy for their unusually large size and the contentious nature of their classification criteria. In this study, we describe a new penguin skeleton with a well-preserved tarsometatarsus discovered in the Upper Eocene of Seymour Island, Antarctica. The new fossil exhibits tarsometatarsal characteristics of Palaeeudyptes but differs from two species of Palaeeudyptes previously found on Seymour Island, providing insights on the morphological diversity and evolutionary history of early penguins. We conduct normality and unimodality tests on Palaeeudyptes taxa from Seymour Island to reassess the hypothesis that size differences between the two species of this genus could be attributed to sexual dimorphism in a single species. The results revealed that size differences are unlikely due to sexual dimorphism. We also use the linear discriminant analysis to evaluate the taxonomic criteria for the two Palaeeudyptes species discovered in the Antarctic region. The data showed an overlap in the size distribution, indicating weakness in the classification criteria. Reassessing previous samples and establishing an additional diagnosis based on critical anatomical features could potentially resolve this issue.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S1871174X24000465

ABSTRACT

The previously scarce fossil record of Ziphiidae (beaked whales) has greatly increased recently thanks to the serendipitous discovery of high specimen concentrations along deep seafloors as well as to abundant inland finds from the Upper Miocene of the Pisco Formation (East Pisco Basin, Peru). In the latter unit, ziphiid remains are indeed among the most prevalent of the whole cetacean assemblage, being represented by four distinct genera and species plus at least two as-yet unnamed taxa. Here, we describe a fifth ziphiid genus and species from the Pisco strata, Mamaziphius reyesi n. gen. n. sp., based on a partial cranium from mid-Tortonian (lower Upper Miocene, 9.1-9.0 Ma) strata exposed at the locality of Cerros la Mama y la Hija. Though reminiscent of the extant genus Berardius, the holotype skull lacks two diagnostic characters of Berardiinae, namely, an isolated rounded protuberance formed by the interparietal or frontals on the posterior part of the vertex, and a posterior transverse narrowing of the nasals and frontals at the vertex. Our phylogenetic analysis reveals that Mamaziphius n. gen. is nested within the crown ziphiids, as sister group of the berardiines. In addition, we introduce two new clade names within Ziphiidae, namely, Messapicetiformes (for the so-called “Messapicetus clade”) and Vomeroziphii (for Ziphiinae + Hyperoodontinae and closely related forms). Another fragmentary specimen from the Pisco Formation is also briefly described herein. Furthermore, a comprehensive reappraisal of the geological age of the fossil beaked whales of Peru is provided based on new age calibrations, thus restricting the whole rich Peruvian record of this family (including the earliest-branching ziphiid, Ninoziphius platyrostris, which comes from Pisco-equivalent strata of the Sacaco area) to a Tortonian-Messinian interval younger than 9.10 Ma. No other inland unit worldwide preserves a record of fossil ziphiids as abundant, diverse and chronostratigraphically well-constrained as the Pisco Formation. In view of this, the absence of Vomeroziphii from the fossil content of the Pisco strata remains quite enigmatic.

LINK(S)

https://www.paleoitalia.it/wp-content/uploads/2024/05/02_Bianucci-et-al_2024_BSPI_631.pdf

ABSTRACT

To date, the presence of pulmonary organs in the fossil record is extremely rare. Among extant vertebrates, lungs are described in actinopterygian polypterids and in all sarcopterygians, including coelacanths and lungfish. However, vasculature of pulmonary arteries has never been accurately identified neither in fossil nor extant coelacanths due to the paucity of fossil preservation of pulmonary organs and limitations of invasive studies in extant specimens. Here we present the first description of the pulmonary vasculature in both fossil and extant actinistian, a non-tetrapod sarcopterygian clade, contributing to a more in-depth discussion on the morphology of these structures and on the possible homology between vertebrate air-filled organs (lungs of sarcopterygians, lungs of actinopterygians, and gas bladders of actinopterygians).

LINK(S)

https://www.nature.com/articles/s41598-024-61065-8
https://www.nature.com/articles/s41598-024-61065-8.pdf

ABSTRACT

A small-bodied ornithomimosaur, Kinnareemimus khonkaenensis Buffetaut, Suteethorn, and Tong 2009, from the Lower Cretaceous Sao Khua Formation of northeastern Thailand was first reported in 1995, then named in 2009. It is the only report of this group in Southeast Asia and was concluded to be a member of Ornithomimosauria, more derived than Harpymimus and Garudimimus but more basal than Archaeornithomimus. Since then, a few published studies have analyzed the phylogenetic position of Kinnareemimus but failed to find it within the clade Ornithomimosauria. Here, the phylogenetic analyses for assessing the relationships of Kinnareemimus within Ornithomimosauria were performed. The results suggested it might be a basal ornithomimosaur or belongs to the subclade Deinocheiridae. Kinnareemimus shares with deinocheirids the proximally projected cnemial crest and the shape of the fibula in proximal view. Its metatarsal III shows subarctometatarsalian condition with metatarsal III pinched between II and IV but visible in anterior view proximally, which might have evolved independently from other ornithomimids. However, the basal position of Kinnareemimus could also be due to the immaturity and the incomplete nature of this animal.

LINK(S)

https://www.mapress.com/zt/article/view/zootaxa.5448.1.4

ABSTRACT

We describe new macro- and microfossils recovered on a field expedition to the North Quarry of Poponguine, a locality in western Senegal that spans the Late Cretaceous through the Early Paleogene, albeit with a likely unconformity at the base of the Danian. Newly discovered macrovertebrates from the Maastrichtian Cap de Naze Formation include pycnodonts, dyrosaurids, and chelonians, the latter two the oldest and first Cretaceous representatives of these clades from Senegal. Screenwashing of this deposit revealed that the matrix also consists of abundant microscopic biological clasts comprising osteichthyan vertebrae, spines, and cranial fragments, shark dermal denticles, invertebrates, and numerous ovoid coprolites among other fragments. These microfossils document a much less conspicuous portion of the paleobiodiversity. We describe the stratigraphy of this new locality and incorporate it into a new correlated section that ties together three other Late Cretaceous--Early Paleogene fossiliferous localities of the Senegalese-Mauritanian Basin. The presence of fossiliferous Danian rocks, which are notably rare in West Africa, is elucidated in our section, which synthesizes prior geological and paleontological work around Poponguine and in the nearby coastal region of Ndayane. Primarily dated using the biostratigraphy of ostracods and foraminiferans, the correlated rock units include the Paki and the Cap de Naze Formations of the Late Cretaceous Diass Group and the Ndayane and the Poponguine Formations of the Paleocene Cap-Vert Group, deposits that capture ancient near shore marine environments. The localities described, although separated by only a few kilometers, exhibit dramatic differences in thickness across faulted blocks of the Diass Horst. Dyrosaurids, which are common fossils in nearshore marine outcrops of West Africa, have been hypothesized to be of African origin and to have dispersed to South America in the Late Cretaceous. This dyrosaurid specimen, although fragmentary, documents a western extreme in the geographic range of African dyrosaurids where the clade would have been well situated for broader trans-Atlantic dispersal.

LINK(S)

https://digitallibrary.amnh.org/items/6220f4c4-7ab5-4cc4-aa3a-f2cff94c7264

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.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2339898

ABSTRACT

Allodaposuchids were among the most common crocodyliforms in the Upper Cretaceous of Europe. The clade, recently erected to include a large number of species described in the last decade, seems to hold a remarkable diversity that has generated systematic controversies. Here we describe an interorbital fragment of an eusuchian crocodyliform, collected in the late 1950s in the locality of Suterranya-Mina de lignit (Lleida, Spain), from the lower Maastrichtian deposits of the Tremp Group, in the southern Pyrenees. The specimen is here identified as an allodaposuchid; some already described teeth, probably found together with the cranial remains and therefore here assigned to the same individual, reinforce this interpretation. The interorbital region of the specimen shows some important similarities with Allodaposuchus subjuniperus, reported only from the upper Maastrichtian levels of the Tremp Group, while it clearly differs from Allodaposuchus palustris, which is already reported in the lower Maastrichtian transitional deposits close to Suterranya-Mina de lignit locality. This study shows that at least three different species of allodaposuchids can be found in the lower Maastrichtian deposits of the Tremp Group.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2350551

ABSTRACT

The vast majority of pterosaurs are characterized by relatively large, elongate heads that are often adorned with large, elaborate crests. Projecting out in front of the body, these large heads and any crests must have had an aerodynamic effect. The working hypothesis of the present study is that these oversized heads were used to control the left–right motions of the body during flight. Using digital models of eight non-pterodactyloids (“rhamphorhyncoids”) and ten pterodactyloids, the turning moments associated with the head + neck show a close and consistent correspondence with the rotational inertia of the whole body about a vertical axis in both groups, supporting the idea of a functional relationship. Turning moments come from calculating the lateral area of the head (plus any crests) and determining the associated lift (aerodynamic force) as a function of flight speed, with flight speeds being based on body mass. Rotational inertias were calculated from the three-dimensional mass distribution of the axial body, the limbs, and the flight membranes. The close correlation between turning moment and rotational inertia was used to revise the life restorations of two pterosaurs and to infer relatively lower flight speeds in another two.

LINK(S)

https://link.springer.com/article/10.1007/s00114-024-01915-7

ABSTRACT

A series of 12 contiguous caudal vertebrae of an ichthyodectiform fish from the Smoky Hill Chalk Member of the Niobrara Formation is described. The vertebral centra exhibit extensive overgrowth of pathological bone and there is additional pathological bone within the centra and intervertebral spaces, which together resulted in the coossification of most centra. The extent of the pathology is greatest on preural vertebrae 1-3 and decreases anteriorly, which suggests that the pathology began posteriorly and progressed anteriorly. In addition to the pathological overgrowth on bones, the specimen preserves features interpreted as calcified and/or ossified soft tissues associated with the neural and haemal canals. The pathologies are unlike previously described examples of bony pathologies in fish, and it is suggested that they resulted from combined bacterial and fungal infections. As the pathologies developed, they would have adversely impacted the fish’s swimming and feeding abilities, and presumably eventually led to the fish’s death.

LINK(S)

https://peerj.com/articles/17353/
https://peerj.com/articles/17353.pdf

ABSTRACT

Bonebeds occurring in exposures of the Burlington and Keokuk Limestones (Mississippian/Osagean) along the Iowa and Illinois border (USA) contain an abundant and diverse collection of chondrichthyan remains that includes teeth, spines, denticles, and coprolites. These remains represent cochliodont, hybodont, petalodont, ctenacanthid, symmoriid, and acanthodian (stem chondrichthyan) taxa. The thickest of these beds, herein referred to as the Burlington–Keokuk bonebed, occurs at the top of the Burlington Limestone and presents a remarkable opportunity to study the assemblage of mid-continent, Middle Mississippian chondrichthyans. Bulk matrix samples of this bonebed were collected from two quarries (Biggsville Quarry, Biggsville, IL, USA, and Nelson Quarry, Mediapolis, IA, USA) and disaggregated. Among the multitude of previously known taxa, several teeth represented a new genus and species of hybodont shark. Herein, we describe these teeth as Columnaodus witzkei (gen. et sp. nov.), a hybodontiform with dental features comparable to unnamed specimens reported from elsewhere.

LINK(S)

https://www.mdpi.com/1424-2818/16/5/276

ABSTRACT

Semi-articulated remains of a large chelonioid turtle from the Turonian strata (Upper Cretaceous; ca. 93.9–89.8 Myr) near Sant’Anna d’Alfaedo (Verona province, northeastern Italy) are described for the first time. Together with the skeletal elements, the specimen also preserves pebbles inside the thoracic area which are lithologically distinct from the surrounding matrix. These allochthonous clasts are here interpreted as geo-gastroliths, in-life ingested stones that resided in the digestive tract of the animal. This interpretation marks the first reported evidence of geophagy in a fossil marine turtle. SEM-EDS analysis, together with macroscopic petrological characterization, confirm the presence of both siliceous and carbonatic pebbles. These putative geo-gastroliths have morphometries and size ranges more similar to those of gastroliths in different taxa (fossils and extant) than allochthonous “dropstone” clasts from the same deposit that were carried by floating vegetation A dense pitted pattern of superficial erosion is microscopically recognizable on the carbonatic gastroliths, consistent with surface etching due to gastric acids. The occurrence of a similar pattern was demonstrated by the experimental etching of carbonatic pebbles with synthetic gastric juice. Gut contents of modern green sea turtles (Chelonia mydas) were surveyed for substrate ingestion, providing direct evidence of geophagic behavior in extant chelonioids. Comparison with modern turtle dietary habits may suggests that the pebbles were ingested as a way to supplement calcium after or in preparation for egg deposition, implying that the studied specimen was possibly a gravid female.

LINK(S)

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0302889

ABSTRACT

The jaws of cephalopods, ammonites and especially coleoids, are rarely met in fossil state. The localities with diversified jaws, belonging to various groups of fossil cephalopods are even less common. We describe a diversified complex of cephalopod jaws from the upper Cenomanian–middle Turonian of Northern Siberia, which include the upper and lower jaws of Placenticeras ammonites (the oldest placenticeratid jaws known to date) and large-sized jaws of octobrachian coleoids. Although the lower jaws of Placenticeras belong to the aptychus type of ammonoid jaw apparatuses, they are characterized by the thickening of an inner organic layer in their anterior part, with a shape resembling a calcified conchorhynch known in the anterior portion of the lower jaws of Mesozoic nautilids and lytoceratid and phylloceratid ammonoids. The presence a conchorhynch-like structure supports the assumption that the feeding function in placenticeratid lower jaws most likely prevailed over the protective one. The upper jaws of Placenticeras show structure, typical for the jaws of aptychophoran ammonites: an inner lamella, divided into two wings, and a pointed outer lamella. Large-sized upper jaws of octobrachian coleoids demonstrate close affinities with the jaws of Octopoda suggesting that they could have belonged to representatives of this order, probably to large-sized gladius-bearing teudopseins. Judging by the jaws’ size, both ammonites and octobrachians, which inhabited the marine basin in the Northern Siberia, were characterized by large body size. The cephalopod assemblage remained unchanged throughout the end of the Cenomanian and the first half of the Turonian.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0195667124000910

ABSTRACT

Lizards are poorly known from the Mesozoic of South America, including several specimens from the Lower and Upper Cretaceous of Brazil, and only a few from the Upper Cretaceous of Patagonia. Here, we describe a new lizard assemblage from a single bone-bearing level in the Allen Formation (upper Campanian – lower Maastrichtian), cropping out at the Cerro Tortuga locality, Río Negro Province, northern Patagonia, Argentina. We recognise the presence of three different taxa, all of them represented by partially isolated maxillae, belonging to different lizard lineages: pleurodontan Iguania; Teiioidea; and possibly Scincoidea. These specimens support the presence of a quite diverse lizard assemblage during the Late Cretaceous in southern South America, suggesting that their absence in other Cretaceous deposits from Patagonia represents preservational and/or sampling bias. The taxonomic diversity also points to a broad ecological diversity, because the three taxa strongly differ in their dental morphology and inferred dietary habits. The assemblage from Cerro Tortuga indicates that lizards, along with snakes and sphenodontians, were an important component of the Late Cretaceous lepidosaurian fauna of South America and, likely, Gondwana.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2344789

ABSTRACT

Sharks, rays, and chimeras have a limited fossil record compared to other taxa due to their predominantly cartilaginous skeletal structure. Fossilization tends to preserve anatomic structures such as teeth, scales, cephalic and caudal fins, and other fins. The Myliobatiformes order, derived from rays, is characterized by viviparity and distinctive serrated stings, with some species exhibiting hexagonal dental plates. These marine organisms inhabit coastal zones globally. This study aims to enhance understanding of Quaternary biodiversity and paleoecology in southern Brazil, focusing on fossils from the Myliobatiformes order, specifically dental plates and stings. Material from biodetrital deposits at Concheiros and Hermenegildo beaches in Santa Vitória do Palmar, Rio Grande do Sul, Brazil, were analyzed. Six taxa were identified from fossil teeth, including Myliobatis ridens, Myliobatis freminvillei, Myliobatis goodei, and Myliobatis sp. (Morphotypes 1 and 2), marking their first Pleistocene fossil record in Brazil. Most teeth couldn't be classified at the species level, but genera were discerned. Fossil stings were described, possibly associated with Myliobatiformes. Results revealed notable differences between identified fossil taxa and their modern counterparts in the western Atlantic Ocean, currently considered common. M. ridens was the most frequent species in the fossil samples, followed by M. freminvillei, with fewer records for M. goodei. Conversely, the current scenario shows M. goodei as the most abundant, followed by M. freminvillei, while M. ridens is Critically Endangered. This investigation expands knowledge of fossil species on the southern Brazilian coast, confirming the presence of M. ridens, M. freminvillei, and M. goodei during the Quaternary.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0895981124001512

ABSTRACT

The sauropodiform sauropodomorph dinosaur Melanorosaurus readi Haughton, 1924, from the lower Elliot Formation (Norian) of South Africa, has had a checkered taxonomic history. This is due to the lack of published information on the original syntype material and the use of referred specimens as the primary source of anatomical information on the taxon. Here, we present a revised osteology of Melanorosaurus based solely on the syntype series and argue that the latter includes the remains of a single, associated individual that we designate the lectotype. The species can be diagnosed on the basis of features of the caudal vertebrae and ilium but we restrict the hypodigm to the lectotype pending detailed reassessment of all referred specimens. Melanorosaurus has been used as an external specifier in the definition of Sauropoda, but given the fragmentary nature of the material, its lack of clear ‘sauropod-like’ features, and its phylogenetic lability we suggest that this is no longer appropriate.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2337802

ABSTRACT

The aim of the present contribution is to describe new materials of lepidosaur reptiles coming from the late Cretaceous (Maastrichtian) Chorrillo Formation, at Santa Cruz province, Argentina. The lepidosaur assemblage is composed by four different snakes (belonging to basal snakes, madtsoiids, and ‘anilioids’) and a tuatara sphenodont. The latter is a new genus and species represented by an incomplete maxilla that shows strong ties to extant Sphenodon. The snakes are represented by isolated vertebrae that indicate they belong to basal forms. Both are very apomorphic and in all probability are the representatives of poorly known lineages. In contrast with recent claims, the fact that most members of this lepidosaur assemblage are highly apomorphic may be indicative of some biogeographical isolation from other Cretaceous lepidosaur associations reported from northern Patagonia.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2341850

ABSTRACT

Crocodyliformes Hay, 1930 represents an important group of archosaurs that is currently restricted to twenty-eight species of semi-aquatic ambush predators. However, the extensive fossil record of Crocodyliformes indicates this group was much more diverse in the past and had a complex evolutionary history, rhythmed by a series of extinction events. An iconic expression of this past diversity is the colonization of the marine realm by several crocodyliform lineages, most notably by Thalattosuchia Fraas, 1901 during the Early Jurassic-Early Cretaceous and by Dyrosauridae de Stefano, 1903 during the Late Cretaceous-Early Eocene. Thalattosuchia constitutes by far the most spectacular and speciose marine radiation of Crocodyliformes, colonizing several ecological niches, before mysteriously going extinct during the Early Cretaceous. Dyrosauridae is well known for massively surviving the end-Cretaceous mass extinction, but disappearing soon afterwards. How crocodyliformes evolved to occupy marine niches and why they went extinct outside the marine extinction events of the Mesozoic is a mystery. Indeed, despite a good fossil record, postcranial elements of thalattosuchians and dyrosaurids have long been disregarded, withal several modern works during the past century. Attention has been focused, for years, on craniodental adaptations and feeding styles only, overlooking the swimming-related adaptations recorded in the postcranial skeleton that permitted these radiations. This work consists of a new thorough comparative description of the pelvic girdle of the most representative members of two extinct clades of aquatic crocodyliforms: Thalattosuchia and Dyrosauridae. This work also provides a standardize terminology and orientated of pelvic elements in those clades. This works does not aim at refining the taxonomy or cladistics of Thalattosuchia and Dyrosauridae, but will certainly clear the way for such future more specific endeavors. This work focuses on the postcranial morphology of Thalattosuchia and Dyrosauridae and aspires to shed light on pelvic evolution throughout their histories. Lastly, this work intends to highlight the relations between form and function within the postcranium of Thalattosuchia and Dyrosauridae, in order to better understand the locomotor habits or limitations present among the members of those extinct groups.

LINK(S)

https://sciencepress.mnhn.fr/en/periodiques/geodiversitas/46/6

https://sciencepress.mnhn.fr/sites/default/files/articles/pdf/g2024v46a6.pdf

ABSTRACT

Theropods are obligate bipedal dinosaurs that appeared 230 Ma and are still extant as birds. Their history is characterized by extreme variations in body mass, with gigantism evolving convergently between many lineages. However, no quantification of hindlimb functional morphology has shown whether these body mass increases led to similar specializations between distinct lineages. Here we studied femoral shape variation across 41 species of theropods (n = 68 specimens) using a high-density 3D geometric morphometric approach. We demonstrated that the heaviest theropods evolved wider epiphyses and a more distally located fourth trochanter, as previously demonstrated in early archosaurs, along with an upturned femoral head and a mediodistal crest that extended proximally along the shaft. Phylogenetically informed analyses highlighted that these traits evolved convergently within six major theropod lineages, regardless of their maximum body mass. Conversely, the most gracile femora were distinct from the rest of the dataset, which we interpret as a femoral specialization to “miniaturization” evolving close to Avialae (bird lineage). Our results support a gradual evolution of known “avian” features, such as the fusion between lesser and greater trochanters and a reduction of the epiphyseal offset, independent from body mass variations, which may relate to a more “avian” type of locomotion (more knee than hip driven). The distinction between body mass variations and a more “avian” locomotion is represented by a decoupling in the mediodistal crest morphology, whose biomechanical nature should be studied to better understand the importance of its functional role in gigantism, miniaturization, and higher parasagittal abilities.

LINK(S)

https://www.cambridge.org/core/journals/paleobiology/article/evolution-of-femoral-morphology-in-giant-nonavian-theropod-dinosaurs/2C41BA499BC30AE01060ACF71D2F6263

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/2C41BA499BC30AE01060ACF71D2F6263/S009483732400006Xa.pdf/div-class-title-the-evolution-of-femoral-morphology-in-giant-non-avian-theropod-dinosaurs-div.pdf