PALEONTOLOGY IN JULY, 2024

ABSTRACT

As part of a larger project identifying and directly radiocarbon dating Late Pleistocene megafaunal remains in British Columbia (B.C.), Canada, we have confirmed the identity of many newly identified mammoth (Mammuthus sp.) specimens (n = 32) from Vancouver Island in Southwestern B.C. We undertook radiocarbon dating on all specimens and were able to obtain dates (due to preservation) on 16 of these remains, including redating a previously dated mammoth using newer radiocarbon extraction methods. The mammoth dates span a wide range, from >47 500 to 18 000 radiocarbon years B.P. (uncalibrated). These later new dates support other lines of evidence for portions of Vancouver Island remaining ice-free until well into the Fraser Glaciation.

LINK(S)

https://cdnsciencepub.com/doi/abs/10.1139/cjes-2023-0102

ABSTRACT

The timing of the emergence of marine reptiles following the Permian–Triassic mass extinction is crucial for studying the recovery of marine ecosystems in the Triassic. Conodonts, key index fossils in the Triassic, are widely used to date the marine reptiles, especially in the Early Triassic. Triassospathodus anhuinensis is a conodont species originally discovered in the upper Spathian of South China, but lacked a comprehensive description, leading to misidentifications and confusion in previous research. Here, we reevaluated Tr. anhuinensis and summarized its morphological characteristics and spatial and temporal distribution based on a review of the literature. We then critically evaluated the age of the primitive ichthyosaur Thaisaurus chonglakmanii from Thailand based on the updated knowledge of Tr. anhuinensis. We sampled the Khao Thong section where T. chonglakmanii was found for conodont study. Tr. anhuinensis elements were obtained from the bed where T. chonglakmanii was collected and also in the bed five metres above the T. chonglakmanii fossil horizon, suggesting a late Spathian age for T. chonglakmanii. A late Spathian age for T. chonglakmanii questions the hypothesis of Thailand as the place of origin of ichthyosaurs in the late Induan or early Spathain.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S1871174X24000945?via%3Dihub

ABSTRACT

Tyrannosaurids were the most derived group of Tyrannosauroidea and are characterized by having two body plans: gracile, long-snouted and robust, deep-snouted skulls. Both groups lived sympatrically in central Asia. Here, we report a new deep-snouted tyrannosaurid, Asiatyrannus xui gen. et sp. nov., from the Upper Cretaceous of Ganzhou City, southeastern China, which has produced the large-bodied and long-snouted Qianzhousaurus. Based on histological analysis, the holotype of Asiatyrannus xui is not a somatically mature adult, but it already passed through the most rapid growth stages. Asiatyrannus is a small to medium-sized tyrannosaurine, with a skull length of 47.5 cm and an estimated total body length of 3.5–4 m; or around half the size of Qianzhousaurus and other large-bodied tyrannosaurines in similar growth stages. Asiatyrannus and Qianzhousaurus are sympatric tyrannosaurid genera in the Maastrichtian of southeastern China. Asiatyrannus differs from Qianzhousaurus in that it has a proportionally deeper snout, longer premaxilla, deeper maxilla, and deeper dentary, and the cornual process of the lacrimal is inflated without developing a discrete horn. The different skull proportions and body sizes suggest that Asiatyrannus and Qianzhousaurus likely had different feeding strategies and occupied different ecological niches.

LINK(S)

https://www.nature.com/articles/s41598-024-66278-5

https://www.nature.com/articles/s41598-024-66278-5.pdf

ABSTRACT

A new troodontid dinosaur, Hypnovenator matsubaraetoheorum gen. et sp. nov., is described based on an articulated postcranial skeleton recovered from the fluvial deposits of the Albian Ohyamashimo Formation of the Sasayama Group in Tambasasayama City, Hyogo Prefecture, Japan. Hypnovenator is distinguished from other troodontids by four autapomorphies and a combination of additional features. Our phylogenetic analysis positions Hypnovenator as the oldest and one of the most basal troodontines, forming a clade with Gobivenator mongoliensis. The discovery of Hypnovenator suggests that small-bodied maniraptorans with a sleeping posture were common not only in environments with volcanic and eolian events or alluvial systems but also in fluvial systems. Geometric morphometric analysis of manual ungual phalanges shows that manual ungual phalanges I and III of Hypnovenator exhibit considerable morphological variation but are functionally similar, which differs from those of non-troodontine troodontids, reflecting the transition of manual motion within Troodontinae. Hypnovenator also has mosaic features in the pes related to cursoriality. This study reveals that asymmetrical arctometatarsus occurred by the Albian, and some morphological changes, such as shorter digit IV than digit III and non-ungual phalanges of digits III with roller joints and digit IV with weakly ginglymoid articulation, arose during the early Late Cretaceous.

LINK(S)

https://www.nature.com/articles/s41598-024-66815-2

https://www.nature.com/articles/s41598-024-66815-2.pdf

ABSTRACT

Living mammal groups exhibit rapid juvenile growth with a cessation of growth in adulthood. Understanding the emergence of this pattern in the earliest mammaliaforms (mammals and their closest extinct relatives) is hindered by a paucity of fossils representing juvenile individuals. We report exceptionally complete juvenile and adult specimens of the Middle Jurassic docodontan Krusatodon, providing anatomical data and insights into the life history of early diverging mammaliaforms. We used synchrotron X-ray micro-computed tomography imaging of cementum growth increments in the teeth to provide evidence of pace of life in a Mesozoic mammaliaform. The adult was about 7 years and the juvenile 7 to 24 months of age at death and in the process of replacing its deciduous dentition with its final, adult generation. When analysed against a dataset of life history parameters for extant mammals, the relative sequence of adult tooth eruption was already established in Krusatodon and in the range observed in extant mammals but this development was prolonged, taking place during a longer period as part of a significantly longer maximum lifespan than extant mammals of comparable adult body mass (156 g or less). Our findings suggest that early diverging mammaliaforms did not experience the same life histories as extant small-bodied mammals and the fundamental shift to faster growth over a shorter lifespan may not have taken place in mammaliaforms until during or after the Middle Jurassic.

LINK(S)

https://www.nature.com/articles/s41586-024-07733-1

ABSTRACT

The fossil record suggests that chordates might have been minor components of marine ecosystems during the first major diversification of animal life in the Cambrian. Vertebrates are represented by a handful of rare soft-bodied stem-lineage taxa known from Konservat-Lagerstätten, including Myllokunmingia and Yunnanozoon from the Stage 3 of South China, and Emmonsaspis and Metaspriggina from Stage 4-Drumian deposits of northeast USA and British Columbia. Here, we describe the first soft-bodied vertebrate from the American Great Basin, a region home to a dozen Cambrian Konservat-Lagerstätten. Found in the Drumian Marjum Formation of Utah, Nuucichthys rhynchocephalus gen. et sp. nov. is characterized by a finless torpedo-shaped body that includes a snout-like anterior head bearing anterolateral eyes, approximately 25 thick myomeres, a large branchial chamber with a keel and approximately seven putative dorsal bars and a spiniform caudal process. Using Bayesian inference, our analysis recovers Nuucichthys within the vertebrate stem, closer to the crown than Pikaia, Yunnanozoon and Myllokunmingia, where it forms a polytomy with its Laurentian relatives, Emmonsaspis and Metaspriggina, and a scion consisting of conodonts and crown-group vertebrates. Based on the eye orientation and absence of fins, we tentatively reconstruct Nuucichthys as a pelagic organism with limited swimming abilities (planktonektic).

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsos.240350

https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.240350

ABSTRACT

Among extant species, the ability to sample the extremes of body size—one of the most useful predictors of an individual's ecology—is highly unlikely. This improbability is further exaggerated when sampling the already incomplete fossil record. We quantify the likelihood of sampling the uppermost limits of body size in the fossil record using Tyrannosaurus rex Osborn, 1905 as a model, selected for its comparatively well-understood life history parameters. We computationally generate a population of 140 million T. rex (based on prior estimates), modelling variation about the growth curve both with and without sexual dimorphism (the former modelled after Alligator mississippiensis), and building in sampling limitations related to species survivorship and taphonomic bias, derived from fossil data. The 99th percentile of body mass in T. rex has likely already been sampled, but it will probably be millennia before much larger giants (99.99th percentile) are sampled at present collecting rates. Biomechanical and ecological limitations notwithstanding, we estimate that the absolute largest T. rex may have been 70% more massive than the currently largest known specimen (~15,000 vs. ~8800 kg). Body size comparisons of fossil species should be based on ontogenetically controlled statistical parameters, rather than simply comparing the largest known individuals whose recovery is highly subject to sampling intensity.

LINK(S)

https://onlinelibrary.wiley.com/doi/10.1002/ece3.11658
https://onlinelibrary.wiley.com/doi/pdf/10.1002/ece3.11658

ABSTRACT

Nearly all dinosaur egg or oospecies occurrences from the Upper Cretaceous of France have been attributed to titanosaur dinosaurs. Here, we describe the first occurrence of probable hadrosauroid eggshells from France, which we assign to a new oospecies, Paraspheroolithus porcarboris oosp. nov. (oofamily: Spheroolithidae), from the upper ‘Argiles et Grès à Reptiles’ Formation (upper Maastrichtian) of Aix-en-Provence. Paraspheroolithus porcarboris differs from all other spheroolithid oospecies in the following combination of characteristics: prolatospherulitic morphotype, prolatocanaliculate pore system, prominent anastomosing ornamentation, medium eggshell thickness, less defined horizontal accretion lines and high pore density. The spheroolithid affinity places the new ootaxon outside oofamilies ascribed to titanosaurs (i.e. Megaloolithidae and Fusioolithidae), and thus its discovery expands the parataxonomic diversity of this region and formation. We suggest the taxonomic affinity of Spheroolithidae is somewhat broader than Hadrosauroidea, potentially encompassing all Ornithopoda. However, a hadrosauroid affinity remains the most plausible for Paraspheroolithus porcarboris based on the absence of other ornithopod remains from late Maastrichtian deposits of the Ibero-Armorican Island.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2380808

ABSTRACT

Based on a unique and extraordinarily preserved complete skeleton, the “Painten pro-pterodactyloid” is formally described and named as Propterodactylus frankerlae, gen. nov., spec. nov. As previously shown, it has a nearly perfect mix of plesiomorphic rhamphorhynchoid-grade, wukongopterid, and derived pterodactyloid traits. Due to its lack of autapomorphies, Propterodactylus is a sufficient intermediate taxon that closes the greatest knowledge gap regarding the evolution of pterosaur morphology. Non-pterodactyloid features include interlocking caudal vertebrae and a functional fifth pedal toe. Derived features such as the nasoantorbital fenestra, a short tail, or initially elongated cervicals and metacarpals appear ancient within the spectrum of Pterodactyloidea. Other early Monofenestrata appear more autapomorphic. However, the late juvenile or subadult status of the described specimen suggests that the rostrum, neck, and extremities might have been even more elongated when fully grown. Despite the otherwise intermediate, transitional osteology, details of dentition types appear mosaic-like in early Monofenestrata. While the remainder of the skeleton of Propterodactylus fits into known evolutionary trends, its dentition implies a significant role of varying dietary adaptation throughout the pterodactyl transition.

LINK(S)

https://palaeo-electronica.org/content/2024/5213-pterosaurian-connecting-link
https://palaeo-electronica.org/content/pdfs/1366.pdf

ABSTRACT

Thyreophora is a taxon of dinosaurs composed of Stegosauria and Ankylosauria, whose members have been known to utilise their tails as powerful defensive weapons. Remains of these dinosaurs are scarce; the Portuguese taxon, Miragaia longicollum, known from three individuals, provides precious pieces of information on the anatomy of these rare animals. This study estimates the stress resistance of a stegosaurian tail and uses Multi-Body Dynamics Analysis (MBDA) to properly simulate the movements of the tail of M. longicollum. The results show that the tail of M. longicollum can achieve high speeds and generate significant pressures, akin to those observed in other tyreophoran dinosaurs. Such high speeds would potentially generate powerful strikes and would inflict injuries on predators. However, the caudal spines of M. longicollum, despite being larger than those of Stegosaurus stenops, have worse stress-bearing performances than those of S. stenops, due to their different morphology. Investigating the complex biomechanics governing the tail of a dinosaur, such as M. longicollum, can have significant implications across various disciplines. Investigating biomechanics in extinct species offers valuable insights into comparative anatomy and physiology, facilitating connections between ancient and contemporary life forms. Palaeontologists and evolutionary biologists might use this information to better comprehend the dinosaur movement, which would advance our understanding of ancient ecosystems and have an impact on how we interpret the behaviour of contemporary animals. The knowledge obtained from such study might provide useful biomimicry lessons for robotics engineers, serving as inspiration for the creation of more adaptable and agile robotic systems.

LINK(S)

https://riviste.unimi.it/index.php/RIPS/article/view/21688
https://riviste.unimi.it/index.php/RIPS/article/view/21688/21488

ABSTRACT

Of the four main Japanese islands, Late Cretaceous dinosaur fossils have been discovered in Hokkaido, Honshu, and Kyushu. Here, we report the first Late Cretaceous dinosaur from the remaining main island Shikoku, an isolated dorsal vertebra from the upper Campanian Hiketa Formation (Izumi Group) in Sanuki, Kagawa Prefecture. The vertebra is incomplete, comprising a robust centrum with a subrectangular profile that is generally characteristic of dinosaurs. Histological examination of the centrum reveals moderately packed trabecular bone and the complete absence of pneumatic structures, which precludes referral of the specimen to Saurischia or Pterosauria. Instead, we interpret it as a hadrosauriform ornithischian based on the slightly expanded anterior articular surface of the centrum; heart-shaped outline of the intervertebral surface, resulting from its dorsally wide and ventrally narrow shape; ventral keel; and neural canal partially embedded into the centrum. As the ventral positioning of the neural canal is common to Bactrosaurus and higher taxa within Hadrosauriformes, we tentatively refer the specimen to Hadrosauroidea. This discovery provides additional evidence that hadrosauriforms had dispersed into present-day Japan by the Campanian and highlights the potential of the Hiketa Formation to provide additional evidence to improve our understanding of the dinosaur diversity at the extreme eastern continental margin of Eurasia.

LINK(S)

https://bioone.org/journals/paleontological-research/volume-28/issue-4/PR230027/A-Hadrosauroid-Vertebra-from-the-Upper-Cretaceous-Izumi-Group-Kagawa/10.2517/PR230027.short?tab=ArticleLink

ABSTRACT

Late Jurassic rhynchocephalians from the Solnhofen Archipelago have been known for almost two centuries. The number of specimens and taxa is constantly increasing, but little is known about the ontogeny of these animals. The well-documented marine taxon Pleurosaurus is one of such cases. With over 15 described (and many more undescribed) specimens, there were no unambiguous juveniles so far. Some authors have argued that Acrosaurus, another common component of the Solnhofen Archipelago herpetofauna, might represent an early ontogenetic stage of Pleurosaurus, but the lack of proper descriptions for this taxon makes this assignment tentative, at best. Here, we describe the first unambiguous post-hatchling juvenile of Pleurosaurus and tentatively attribute it to Pleurosaurus cf. P. ginsburgi. The new specimen comes from the Lower Tithonian of the Mörnsheim Formation, Germany. This specimen is small, disarticulated, and incomplete, but preserves several of its craniomandibular bones and presacral vertebrae. It shares with Pleurosaurus a set of diagnostic features, such as an elongated and triangular skull, a low anterior flange in its dentition, and an elongated axial skeleton. It can be identified as a juvenile due to the presence of an unworn dentition, well-spaced posteriormost dentary teeth, a large gap between the last teeth and the coronoid process of the dentary, and poorly ossified vertebrae with unfused neural arches. Acrosaurus shares many anatomical features with both this specimen and Pleurosaurus, which could indicate that the two genera are indeed synonyms. The early ontogenetic stage inferred for the new Pleurosaurus specimen argues for an even earlier ontogenetic placement for specimens referred to Acrosaurus, the latter possibly pertaining to hatchlings.

LINK(S)

https://anatomypubs.onlinelibrary.wiley.com/doi/abs/10.1002/ar.25545
https://www.researchgate.net/publication/382461814_A_juvenile_pleurosaurid_Lepidosauria_Rhynchocephalia_from_the_Tithonian_of_the_Mornsheim_Formation_Germany

ABSTRACT

Very few remains of elapid snakes are known from the Iberian Peninsula, but these include a probable endemic extinct species of cobra, Naja iberica from the Late Miocene. We here describe isolated cobra vertebrae from several Middle–Late Miocene localities in the Vallès-Penedès Basin (Catalonia, Spain). All of these fossils are herein referred to an indeterminate species of the genus Naja. These remains are the first conclusive evidence that cobras were present in Iberia before the Messinian Salinity Crisis, and that they persisted there throughout the Miocene (and ultimately until the Pliocene). Recently, a phylogeny of extinct Naja based on cranial and vertebral morphology recognized N. iberica as a distinct lineage separate from the Central European one, represented mainly by Naja romani. However, due to taxonomic uncertainties, it is still unclear whether Iberian cobras were all part of a single lineage or whether several Naja lineages inhabited the Iberian Peninsula. They went extinct in Iberia before the end of the Pliocene. In the Vallès-Penedès Basin, cobras were living in a mosaic environment, surviving through different phases characterized by different environmental features.

LINK(S)

https://onlinelibrary.wiley.com/doi/abs/10.1002/spp2.1575

ABSTRACT

The earliest crocodylomorphs, known as non-crocodyliform crocodylomorphs, first appeared during the Late Triassic. In contrast to extant crocodylians, which are all semi-aquatic, early crocodylomorphs represent terrestrial taxa with a fully erect posture and in most cases a small body size. Their gracile skeletons suggest an active mode of life, possibly similar to contemporaneous, bipedal theropod dinosaurs. Despite this remarkable body plan, the postcranial morphology of early crocodylomorphs has rarely been documented in detail, restricting our ability to infer aspects of their functional morphology and evolution. Here, we provide a detailed description of the postcranium of Terrestrisuchus gracilis, a small-bodied crocodylomorph from the Late Triassic of Pant-y-Ffynnon Quarry (southern Wales, UK), including a description of long bone tissues based on histological thin sections. Almost all elements of the postcranial skeleton have been preserved. The skeleton of Terrestrisuchus gracilis is highly gracile, even for a non-crocodyliform crocodylomorph. Osteological correlates of the appendicular skeleton suggest that Terrestrisuchus gracilis had a digitigrade, quadrupedal posture. A quantitative analysis of limb robustness corroborates that Terrestrisuchus gracilis was a quadruped. Histological analysis suggests that all sampled specimens were skeletally immature and had fast growth at the time of death, as indicated by the lack of an external fundamental system and the predominance of fibrolamellar bone. The bone tissue is similar to that recently described for Saltoposuchus connectens and certain non-crocodylomorph pseudosuchians, but differs from Hesperosuchus agilis and crocodyliforms, in which parallel-fibred bone is more prevalent.

LINK(S)

https://onlinelibrary.wiley.com/doi/full/10.1002/spp2.1577
https://onlinelibrary.wiley.com/doi/pdf/10.1002/spp2.1577

ABSTRACT

A new ichnotaxon, Ambulopisces voigti (ichnogen. et ichnosp. nov.), from the early Permian (Wolfcampian) Robledo Mountains Formation (Hueco Group) of south-central New Mexico, is described and shown to represent a fish walking on a muddy substrate. A. voigti is a compound ichnotaxon comprising alternating left and right pectoral fin impressions that show the walking behaviour plus a superimposed sinusoidal caudal fin drag that can be assigned to Undichna. The pectoral fin impressions are surrounded by expulsion rims, which show that the fins were weight-bearing; these are larger posteriorly where sediment was pushed up by the propulsive motion of the fin. The shape of the expulsion rims thus indicates the direction of travel. Propulsion was accomplished by alternately pressing the pectoral fins into the substrate and flexing the body to bring the opposing pectoral fin and the body forward. The identity of the tracemaker is uncertain, but it was a small, low-profile fish whose pectoral fins spanned only ~ 60 mm. The proximity of the pectoral fin bases to the centerline of the trace does not support a lobe-finned fish as the tracemaker.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2371958

ABSTRACT

A pervasive maxim in herpetology is that alligators (Alligatoridae) are poor salinity regulators relative to their taxonomic kin, crocodiles (Crocodylidae), evidenced by the purported lack of osmoregulatory abilities of modern Alligator and caimans, which has led to the assumption that freshwater obligation is synapomorphic across the clade, to include extinct members of Alligatoridae, or even Alligatoroidea. Presented here is a brief review of osmoregulation and the fossil record of alligatoroids and a suggestion that salt-tolerance may have been more widespread in the group than is widely assumed, based upon the observations that 1) modern alligatorids are increasingly reported from brackish and marine environs and possess osmoregulatory abilities attained through different regulatory pathways than their crocodile counterparts, and 2) fossil members of the group are routinely (or exclusively) found in or near marine depositional settings, suggesting plausibility that earlier members of the clade were more ocean-going than their extant descendants. Starting with fewer assumptions about the osmoregulatory abilities of extinct taxa may help solve continuing problems in eusuchian biogeography, namely, the dispersals of alligatoroids into Europe and Asia, and multiple dispersal events to and from pre-Interchange South America. Secondary loss of salinity tolerance in Alligator may be adaptive in continental habitats.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/08912963.2024.2379029

ABSTRACT

This study provides the first overview of dental pathologies in pycnodonts, a diverse group of fossil actinopterygians that existed from the end of the Middle Triassic to the end of the Eocene. We considered 100 pathological pycnodont specimens, 71 of which were studied by first-hand examination and 29 by consulting published descriptions. Diagnoses were performed based on macroscopic and microscopic observation and, where necessary, also with the help of radiographic and tomographic examinations. The 100 pathological specimens belong to 27 genera and 57 species, which represent 26.5% of all known genera and 10.2% of all known species. The most frequent anomalies are (i) tooth malpositions, (ii) supernumerary teeth and (iii) shape anomalies of single teeth, including microdotia and exceptional cases of macrodontia. Dental pathologies in pycnodonts are unevenly distributed over geological time: they were much more common in the Late Triassic and Jurassic, while they had become much rarer during the Cretaceous. In a single pycnodont population from the Eocene of Mali, 54.5% of the specimens are affected by dental anomalies, probably as the result of pathogenic drift in an isolated population. The uneven distribution of tooth anomalies over the long period of pycnodont evolution suggests that their dentition was initially not ordered into distinct dental rows; this order was acquired only in the most derived forms. To consolidate these hypotheses it will be necessary to expand the paleopathological statistics with more specimens.

LINK(S)

https://www.schweizerbart.de/papers/njgpa/detail/311/105466/Dental_paleopathologies_in_Pycnodontiformes_Osteichthyes_Actinopterygii

ABSTRACT

The thalattosaur genus Xinpusaurus Yin in Yin et al. 2000 from the Upper Triassic (Carnian, Tuvalian) Xiaowa Formation of Guizhou, People’s Republic of China, is represented by several well-preserved skulls and skeletons. Although its osteology is relatively well known, the taxonomy of the genus is complicated by a lack of a full description of the holotype of the type species, Xinpusaurus suni Yin, 2000, and an inadequate description of X. bamaolinensis Cheng, 2003. In this paper, additional data are presented on several referred specimen of Xinpusaurus suni and on X. kohi. Previous attempts to differentiate species of Xinpusaurus from the Xiaowa Formation are discussed. A new phylogenetic analysis of the Thalattosauria is performed to evaluate the observable morphological differences, including all relevant specimens of Xinpusaurus as separate OTU’s. It demonstrates that specimens hitherto referred to X. suni are conspecific. X. bamaolinensis shows no differences to X. suni, and is regarded as a junior subjective synonym. X. kohi differs from X. suni in the completely straight rostrum, a contact between frontal and supratemporal, a well-developed deltopectoral crest of the humerus, a hatchet-shaped instead of reniform radius and ossification of the distal carpals and tarsals. It is a diagnosable taxon and the second valid species of Xinpusaurus. Xinpusaurus xingyiensis is the sister-taxon of Concavispina biseridens. It is referred to that genus as Concavispina xingyiensis n. comb. There is thus no Middle Triassic record of the genus Xinpusaurus. Specimen HFUT GL-17-006, referred to X. suni as a juvenile specimen, is also different from Xinpusaurus and possibly represents a new genus and species. The genus Xinpusaurus as redefined is monophyletic. A close phylogenetic relationship of Xinpusaurus and Nectosaurus is re-confirmed. The Askeptosauroidea is monophyletic, with Askeptosaurus holding the most basal position, but otherwise askeptosauroid interrelationships remain unresolved, including the three named species of Anshunsaurus, which is not found to be monophyletic. Thalattosauroidea and Thalattosauridae, but not Claraziidae, are confirmed as monophyletic groups. Thalattosauridae includes Thalattosaurus and Nectosaurus, as originally envisaged by Merriam, as well as Concavispina, Xinpusaurus, Gunakadeit, and the currently unnamed HFUT GL-17-00. Concavispina is the most basal thalattosaurid. Within Thalattosauridae, the recently described Gunakadeit is the sister-taxon of Nectosaurus. Gunakadeit and Nectosaurus are highly derived thalattosaurids, which form the sister-group of Xinpusaurus.

LINK(S)

https://www.schweizerbart.de/papers/njgpa/detail/311/105464/Notes_on_thalattosaurs_Reptilia_Triassic_with_spec?af=crossref

ABSTRACT

Here we describe a new genus and species of metriorhynchid crocodylomorph, Enalioetes schroederi gen. et sp. nov., from the lower Valanginian Stadthagen Formation (Lower Cretaceous) of north-western Germany. Enalioetes schroederi is the most complete and well-preserved Cretaceous metriorhynchid skull known to date, preserving most of the cranium and mandible, the atlas-axis complex and the first postaxial cervical vertebra. The specimen was previously attributed to the coeval enigmatic metriorhynchid Enaliosuchus (a nomen dubium) and, more recently, to Cricosaurus. Although the specific epithet schroederi has been used frequently in the literature, it has never been formally established. Herein, we demonstrate that the new taxon is distinct from all known metriorhynchids by a unique combination of characters including several autapomorphies such as: the lack of bulbous dorsolateral expansion in the posterior nasal cavity; mediolateral distance between the orbital canals being approximately 1.5 times the diameter of the orbital canals; lacrimal with dorsoventrally deep anterior process ventral to the preorbital fossa being equal to or greater than the depth of the jugal anterior process and the anterodorsal process of the lacrimal; and ascending processes at atlas intercentrum extending far dorsally to level of neural canal. Enalioetes schroederi contributes to the sparse global record of Cretaceous metriorhynchids and represents one of the stratigraphically youngest occurrences of the group. It can thus help to enhance our understanding of the metriorhynchid diversity during the Cretaceous Period.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/14772019.2024.2359946

ABSTRACT

Pterosaurs were the first powered flying vertebrates, with a fossil record that stretches back to about 230 million years before present. Most species are only known from one to three specimens, which are most often fragmentary. However, Rhamphorhynchus muensteri is known from numerous excellent specimens, including multiple specimens with soft tissue preservation. As such, Rhamphorhynchus muensteri is one of the only pterosaurs amenable to analysis for intraspecific variation. It has been previously predicted that elements directly involved in the flight apparatus, such as those of the forelimb, will be more highly constrained in their proportions than other parts of the skeleton. We investigated the degree of variation seen in elements and body parts of Rhamphorhynchus, which represents the best model system among pterosaurs for testing these expectations of intraspecific variation. We recover evidence for high levels of constraint throughout the appendicular and axial elements (head, neck, torso, tail, forelimbs, hindlimbs), suggesting that all were important for flight. We further find that tail variation increases among the largest specimens, suggesting reduced constraint and/or stronger sexual selection on the tail in more mature individuals.

LINK(S)

https://peerj.com/articles/17524/
https://peerj.com/articles/17524.pdf

ABSTRACT

The fossils of the Lebanese Upper Cretaceous Lagerstätten, especially the articulated fish, are world renowned. Famous for their soft tissue preservation and highly sought after by fossil collectors, Lebanese fossils provide key information concerning the evolution of several major extant and extinct groups of Mesozoic organisms including cephalopods, crustaceans, hagfish, sharks, marine reptiles and pterosaurs. In fact, fossils from Lebanon are so exceptional that historical documentation describing them extends back to the Roman Empire. However, despite over 1600 years of knowledge of these fossils, a thorough understanding of the depositional environments, taphonomy and palaeoecology of the four main sites, Haqel, Hjoula, Nammoura (each Cenomanian in age) and Sahel Aalma (Santonian), is lacking. Here we compile a review of the palaeoenvironments, fauna and flora of these four Lebanese Lagerstätten. Our synthesis outlines the history of fossil discovery, and describes the current understanding of the geology, ages, mode of preservation and organisms found at these four sites. We also undertake a bibliometric and holotype analysis to investigate the impact that scientific colonialism has had on Lebanon. Our data confirm that local Lebanese researchers are typically not included in publications pertaining to Lebanese fossils and that the majority of Lebanese type material is stored in large historical collections outside Lebanon, predominantly in institutions within the northern hemisphere. Here, we recommend some basic practices for researchers utilizing historical collections that can help develop local Lebanese fossil collections and establish more research opportunities for local palaeontologists.

LINK(S)

https://www.lyellcollection.org/doi/full/10.1144/jgs2023-210

ABSTRACT

Tooth attachment and replacement play significant roles in the feeding ecology of polyphyodont vertebrates, yet these aspects have remained largely unexplored in non-avialan paravians including troodontids. Here, we describe a new troodontid species, Urbacodon norelli sp.n., recovered from the Upper Cretaceous Iren Dabasu Formation of Inner Mongolia, China, based on an incomplete right dentary and 12 associated replacement teeth. Urbacodon norelli is distinguished from all other known troodontids, including its relative U. itemirensis from Uzbekistan, by several features: the presence of paired dentary symphyseal foramina, the presence of a relatively steep anterior margin of the dentary, the absence of a dentary chin, the presence of a common groove hosting the anterior 12 dentary teeth, and the presence of relatively larger dentary teeth. Phylogenetic analysis places both species of Urbacodon as sister taxa to Zanabazar junior, confirming their status as later-diverging troodontids. Radiographs revealed an alternating tooth replacement pattern in U. norelli, with a maximum Zahnreihen-spacing estimated to be 3. During tooth replacement, the anteriorly inclined interdental septa, which wedge between anterior dentary teeth, underwent frequent remodelling as the developing tooth moved upwards, particularly anterolabially. This rapid turnover left insufficient time for an interdental plate to form, resulting in the absence of such structures in this specimen. The frequent remodelling of periodontal tissues accompanying tooth replacement is likely to account for the absence of interdental plates. The discovery of this new troodontid expands our understanding of paravian theropods from the Upper Cretaceous Iren Dabasu Formation and provides valuable insights into troodontid tooth biology.

LINK(S)

https://onlinelibrary.wiley.com/doi/10.1111/cla.12592

ABSTRACT

Trigonosaurus pricei is a small to medium-sized sauropod dinosaur (Sauropoda: Titanosauria) from the Late Cretaceous Bauru Group of Brazil that is known from a significant amount of recovered axial elements [four cervical vertebrae, 10 dorsal vertebrae, sacrum (MCT 1488-R), and 10 caudal vertebrae (MCT 1719-R)]. In this biomechanical work, we approach the hypothesis of the cartilaginous neutral pose and the range of motion of the axial series of Trigonosaurus. The results show that this sauropod could be capable of high elevation of the neck resulting from morphological adaptations of the cervicodorsal region on dorsal (D) vertebrae D2 and D3 (e.g. postzygapophyses of D2 positioned over the vertebral centrum and prezygapophyses of D3 over the anterior vertebral centrum). This implies that D2 articulates (cartilaginous neutral posture) with D3 only at a strong dorsally directed angle, resulting in a shift in the direction of the neck to a more elevated posture. Furthermore, the tail attributed to Trigonosaurus as a paratype could be oriented in the horizontal ‘direction’ and presented a sigmoidal ‘shape’. This work contributes generally to the understanding of variation in the body plan of sauropods and, more specifically, to the feeding strategy of small and medium-sized titanosaurs from semi-arid regions of Gondwana.

LINK(S)

https://academic.oup.com/zoolinnean/article-abstract/201/3/zlae087/7714428?redirectedFrom=fulltext

ABSTRACT

The Tyrannosauridae, which is characterized by specialized pachydont dentition and putative bone-cracking predatory strategies, is one of the most extensively studied theropod lineages. Although tooth replacement patterns, crucial for understanding feeding behaviors, have been thoroughly studied in this group, studies on non-tyrannosaurid tyrannosauroids are relatively scarce. This study utilizes high-resolution CT data to investigate the tooth replacement pattern in two specimens of Guanlong wucaii, a Late Jurassic tyrannosauroid, and provides insights into the evolution of tooth replacement across Tyrannosauroidea. Second-generation replacement teeth, a rarity observed mainly in giant predatory theropods (e.g. some tyrannosaurids), were detected in the dentary dentition of the juvenile Guanlong. Zahnreihen reconstructions display a consistent cephalad alternating tooth replacement pattern in the maxilla and the dentary of both of the examined individuals, with Z-spacing values exceeding 2.0. As Guanlong grows, the Z-spacing value in the maxillary dentition increases, resembling the ontogenetic changes documented in the Tyrannosauridae. Additionally, like Tarbosaurus, Guanlong also displays a discontinuity between the tooth replacement waves at the premaxilla-maxilla boundary. This study thus demonstrates that some tyrannosaurid-like tooth replacement patterns were acquired before the origin of the Tyrannosauridae.

LINK(S)

https://www.vertpala.ac.cn/EN/10.19615/j.cnki.2096-9899.240715

ABSTRACT

Among non-avian dinosaurs, troodontids are relatively rare but diverse. The Nemegt Basin in the Mongolian Gobi Desert, which incorporates three of the most fossiliferous beds in the world, is one such region with high troodontid diversity and has also produced eight troodontid taxa until now. The diversity of troodontids is biased towards the two formations, Nemegt and Djadochta. Despite its rich vertebrate fossil record, no troodontids have been described from the Baruungoyot Formation. This faunal absence is perplexing as the Baruungoyot Formation has often been considered intermediate between the other two units in stratigraphy and paleoenvironment, but there are no definite troodontid materials that could fill this ‘gap.’ Here, we report a new troodontid, Harenadraco prima gen. et sp. nov., from the Baruungoyot Formation in Hermiin Tsav, Mongolia. It is represented by an incomplete skeleton that mainly consists of partially articulated left hind limb elements. Harenadraco is small and lightly built like other troodontids, but its tarsometatarsus exhibits extreme slenderness comparable only to Philovenator among cursorial non-avian maniraptorans. It also implies high cursoriality that could be an adaptation of Harenadraco to its environment where potential prey animals like mammals and predators such as eudromaeosaurs were likely to be agile. The discovery of Harenadraco confirms the presence of troodontids in all three formations in the Nemegt Basin.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2364746
https://www.tandfonline.com/doi/epdf/10.1080/02724634.2024.2364746?needAccess=true

ABSTRACT

Some new tridactyl footprints have been recorded in the Malhada Vermelha farm locality, municipality of Fortaleza dos Nogueiras, state of Maranhão, northern Brazil, from the Sambaíba Formation, Parnaíba Sedimentary Basin. The specimens are fifteen isolated, in situ, mesaxonic tridactyl tracks preserved in six sandstone slabs as concave epireliefs. Abundant MISS evidence is preserved on the track-bearing blocks. The footprints are referred to as Grallator isp., linking them with an theropodian origin. The footprint-bearing levels were accumulated in shallow environments influenced by a tidal flat. The occurrence and interpretation of these findings bring a new approach to sedimentary subenvironments in the Sambaíba Formation.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0895981124002554

ABSTRACT

Thalattosuchian crocodylomorphs were a ubiquitous component of shallow marine ecosystems during the Jurassic and Early Cretaceous. Alas, their origins remain a mystery. Here we describe three specimens from the Sinemurian (and possibly Early Pliensbachian) of the UK: a partial cranial rostrum, a series of cervical vertebrae, and two dorsal vertebrae adhered with matrix. These specimens are amongst the oldest known thalattosuchian fossils, with the partial cranial rostrum being the oldest known non-neothalattosuchian thalattosuchian. This partial cranial rostrum has a unique combination of rostral characters never seen before in any crocodylomorph, and helps to elucidate early thalattosuchian internal rostrum evolution, suggesting that the reduction in thalattosuchian paranasal sinuses was not related to either the reorganization of rostral neurovasculature seen in later diverging taxa or the increased cancellous bone microstructure. Based on our CT sample, a shift in cranial bone microstructure occurred in the Eoneustes + Metriorhynchidae subclade, one that coincided with the enlargement of the salt glands and decoupling of the external antorbital fenestra from the paranasal sinuses. Without extensive histological sampling we cannot determine whether the shift to an obligate aquatic lifestyle occurred prior to the evolution of Metriorhynchidae.

LINK(S)

https://academic.oup.com/zoolinnean/article-abstract/201/3/zlae079/7713265?redirectedFrom=fulltext

ABSTRACT

Until the late 20th century, the idea of identifying wildfires in deep time was not generally accepted. One of the basic problems was the fact that charcoal-like wood fragments, so often found in sedimentary rocks and in coals, were termed fusain and, in addition, many researchers could not envision wildfires in peat-forming systems. The advent of Scanning Electron Microscopy and studies on modern charcoals and fossil fusains demonstrated beyond doubt that wildfire residues may be recognized in rocks dating back to at least 350 million years. Increasing numbers of studies on modern and fossil charcoal assemblages from the 1970s through the 1990s established the potential importance of wildfires in the fossil record, using Carboniferous examples in particular. Since the 1990s, extensive progress has been made in understanding modern wildfires and their byproducts. New techniques to study ancient charcoals have allowed considerable progress to be made to integrate modern and ancient fire studies, both before and after the evolution of mankind. Four important developments have made a reassessment of Carboniferous wildfires necessary: the recognition of the role of atmospheric oxygen in controlling the occurrence of wildfire; the development of new microscopical techniques allowing more detailed anatomical data to be obtained from charcoal; the integration of molecular studies with the evolution of fire traits; and new developments in or understanding of post-fire erosion/deposition systems.

LINK(S)

https://www.mdpi.com/2571-6255/7/7/248

ABSTRACT

The exceptionally preserved soft-bodied fossils from the Chengjiang Biota of southwest China have proved to be critical for our understanding of the biodiversity and ecology of the Cambrian explosion of animals. Almost all previously reported soft-bodied Chengjiang fossils are from the event mudstone beds (EB) of the Yu’anshan Formation. Here, we present the first comprehensive investigation of the soft-bodied fossils from the interbedded background mudstone beds (BGB), based on collections made across the past decade, and characterize their preservation. Soft internal cellular organs/tissues, such as digestive tracts and glands, cardiovascular systems, nervous systems, and musculature, are predominantly preserved as carbonaceous compressions, in contrast to their iron oxide−rich preservation in the EB. Our work highlights two distinct preservation modes within a single Burgess Shale−type Lagerstätte, possibly due to the complex interplay of decay, kerogenization, and pyritization.

LINK(S)

https://pubs.geoscienceworld.org/gsa/geology/article-abstract/doi/10.1130/G52215.1/645501/Unveiling-an-ignored-taphonomic-window-in-the

ABSTRACT

Fossiliferous carbonate concretions are commonly found in sediments deposited in the Late Cretaceous Western Interior Seaway. Although concretions are diagenetic features, well-preserved fossils from within them have been instrumental in reconstructing the temperature and δ18O value of Western Interior Seaway seawater, which is essential for accurate reconstruction of Late Cretaceous climate. Here, we constrain formation conditions of Late Campanian and early Maastrichtian carbonate concretions by combining triple oxygen isotope measurements with carbonate clumped isotope paleothermometry on different carbonate phases within the concretions. We measured both fossil skeletal aragonite and sparry calcite infill from cracks and within macrofossil voids to evaluate differences between “primary” and “altered” geochemical signals. Based on the two temperature-sensitive isotope systems of the primary fossil shell aragonite, the temperature of the Western Interior Seaway was between 20 °C and 40 °C and was likely thermally stratified during the Campanian. The reconstructed δ18Oseawater values of ∼−1‰ for Campanian Western Interior Seaway waters are similar to those expected for the open ocean during greenhouse climates, while the Maastrichtian Western Interior Seaway may have been more restricted, with a δ18Oseawater value of ∼2‰, which reflects more evaporative conditions. We reconstructed the diagenetic history of the sparry infill and altered fossils using a fluid-rock mixing model. Alteration temperature, alteration fluid δ18O value, and the initial formation temperature were calculated by applying the fluid-rock mixing model to a particle swarm optimization algorithm. We found a different range of initial formation temperatures between the Campanian (25−38 °C) and Maastrichtian (9−28 °C). We also found that alteration in the presence of light meteoric fluids (δ18O ≈ −10‰) is required to explain both the sparry infill and the altered fossil isotopic values. Based on our results, both lithification and alteration of the carbonates occurred soon after burial, and light meteoric fluids support prior findings that high-topographic relief existed on the western margin of the Western Interior Seaway during the Late Cretaceous. As one of the first studies to apply these techniques in concert and across multiple mineralogical phases within samples, our results provide important constraints on paleoenvironmental conditions in an enigmatic ocean system and will improve interpretations of the overall health of ecosystems leading into the end-Cretaceous mass extinction.

LINK(S)

https://pubs.geoscienceworld.org/gsa/gsabulletin/article-abstract/doi/10.1130/B37543.1/645498/Reconstructing-paleoenvironments-of-the-Late

ABSTRACT

In the Baltic States and Belarus, the Middle Devonian period is characterised by an abundant fossil record of invertebrates such as scolecodonts, brachiopods, ostracods, trilobites, bivalves, crinoids, gastropods, and tentaculites. On the other hand, there was limited diversity in the conodont and other vertebrate fauna. In this study, we introduce a newly refined ichthyofaunal assemblage from the Eifelian and Givetian epochs from the present-day regions of Belarus and Lithuania. The isolated scales of Cheirolepis are identified as C. gaugeri, C. cf. gaugeri, C. aleshkai, C. cf. aleshkai, and Cheirolepis sp., while Orvikuina is represented by the isolated scales of O. vardiaensis and Orvikuina sp. The histological analyses for the scales of Orvikuina are provided here. Moreover, Orvikuina and Cheirolepis taxa are now recognised to be widely distributed throughout the Baltic States, especially Lithuania and Belarus, as a result of these findings. Thus, this ichthyofaunal data markedly improved the biostratigraphic correlation within the study region and expanded the paleogeographic distribution of these taxa during the Eifelian and Givetian time in Laurasia.

LINK(S)

https://www.mdpi.com/2813-6284/2/3/7

ABSTRACT

The early evolution of Pan-Chelonioidea (sea turtles) is poorly understood. This is in part due to the rarity of undeformed skulls of definitive early stem chelonioids. In this work, we redescribe the holotype of Nichollsemys baieri using µCT scans and segmentations of the skull. This fossil is the best 3D preserved skull of any Campanian sea turtle, and includes partial “soft tissue” preservation. Nichollsemys is morphologically similar but clearly distinct from Toxochelys spp., and both show a mosaic of plesiomorphic and derived chelonioid features. The internal cranial anatomy documents the presence of derived characters in Nichollsemys baieri that are absent in Toxochelys spp., such as the loss of the epipterygoids and the rod-like shape of the rostrum basisphenoidale. Among the numerous plesiomorphic characters is the presence of a splenial bone, which was unnoticed before. An updated phylogenetic analysis retrieves Nichollsemys baieri as a non-protostegid early stem chelonioid in a slightly more crownward position than Toxochelys latiremis. Our phylogeny includes macrobaenids and protostegids as pan-chelonioids, and we find unorthodox results for dermochelyids. Thus, although Nichollsemys baieri provides important new insights into the early morphological evolution of sea turtles, much work remains to be done. As a completely 3D preserved specimen, we included Nichollsemys baieri into a recent landmark-based skull shape dataset of turtles. Morphospace analysis reveals an intermediate position between cryptodires and crown chelonioids. Based on these data, we also predict that Nichollsemys baieri was still capable of neck retraction, constraining the loss of this trait to more crownward pan-chelonioids.

LINK(S)

https://sjpp.springeropen.com/articles/10.1186/s13358-024-00323-8
https://sjpp.springeropen.com/counter/pdf/10.1186/s13358-024-00323-8.pdf

ABSTRACT

We present the pelvic and hindlimb musculature of the abelisaurid Skorpiovenator bustingorryi, constituting the most comprehensive muscle reconstruction to date in ceratosaur theropods. Using extant phylogenetic bracket method, we reconstructed 39 muscles that can commonly found in extant archosaurs. Through the identification of bone correlates, we recognized thigh and hindlimb muscles including knee extensors, m. iliofibularis, m. flexor tibialis externus, mm. caudofemorales, mm. puboischiofemorales, and crus muscles important in foot extension and flexion (e.g., m. tibialis anterior, mm. gastrocnemii). Also, autopodial intrinsic muscles were reconstructed whose function involve extension (m. extensor digiti 2–4), flexion (mm. flexor digitorum brevis superficialis), interdigital adduction (m. interosseus dorsalis) and abduction (m. interosseous plantaris, m. abductor 4). Abelisaurids like Skorpiovenator show a deep pre- and postacetabular blade of the ilia and enlarged cnemial crests, which would have helped increasing the moment arm of muscles related to hip flexion and hindlimb extension. Also, pedal muscles related to pronation were probably present but reduced (e.g., m. pronator profundus). Despite some gross differences in the autopodial morphology in extant outgroups (e.g., crocodilian metatarsus and avian tarsometatarsus), the present study allows us to hypothesize several pedal muscles in Skorpiovenator. These muscles would not be arranged in tendinous bundles as in Neornithes, but rather the condition would be similar to that of crocodilians with several layers formed by fleshy bellies on the plantar and dorsal aspects of the metatarsus. The musculature of Skorpiovenator is key for future studies concerning abelisaurid biomechanics, including the integration of functional morphology and ichnological data.

LINK(S)

https://anatomypubs.onlinelibrary.wiley.com/doi/abs/10.1002/ar.25532

ABSTRACT

A new specimen of the pliosaurid Liopleurodon ferox from the Callovian strata (Middle Jurassic) of France is described. This new specimen represents one of the most-complete post-cranial skeletons known for this species. Remains of Liopleurodon ferox were previously reported from central and southern England, Germany, the North of France, and possibly from Poland and Russia. The specimen examined here therefore extends the biogeographical area of the species into central France and represents the southernmost occurrence of this taxon. Based on osteological evidence, the specimen is here identified as an “adult” individual, confirming that the lack of fusion between the cervical neural arches and associated centra is not a reliable indicator of a juvenile condition in pliosaurids. Instead, such a lack of fusion in cervical vertebrae is more likely to be paedomorphic in adult pliosaurids, as noted in previous works. However, this statement does not hold true for dorsal and caudal vertebrae, or cervical ribs, in which the pattern of suture closure may vary according to taxa. Overall, our results indicate that the open or closed conditions of the neurocentral sutures of all the vertebrae of the vertebral column, as well as the suture between ribs and centra, is a poor indicator of ontogenetic stages in pliosaurids.

LINK(S)

https://palaeo-electronica.org/content/2024/5257-jurassic-liopleurodon-of-france
https://palaeo-electronica.org/content/pdfs/1280.pdf

ABSTRACT

Recent studies suggest that both stem- and crown-group Archosauria encompassed high ecological diversity during their initial Triassic radiation. We describe a new pseudosuchian archosaur, Benggwigwishingasuchus eremicarminis gen. et sp. nov., from the Anisian (Middle Triassic) Fossil Hill Member of the Favret Formation (Nevada, USA), a pelagic setting in the eastern Panthalassan Ocean characterized by the presence of abundant ammonoids and large-bodied ichthyosaurs. Coupled with archosauriforms from the eastern and western Tethys Ocean, Benggwigwishingasuchus reveals that pseudosuchians were also components of Panthalassan ocean coastal settings, establishing that the group occupied these habitats globally during the Middle Triassic. However, Benggwigwishingasuchus, Qianosuchus, and Ticinosuchus (two other pseudosuchians known from marine sediments) are not recovered in a monophyletic group, demonstrating that a nearshore marine lifestyle occurred widely across Archosauriformes during this time. Benggwigwishingasuchus is recovered as part of an expanded Poposauroidea, including several taxa (e.g. Mandasuchus, Mambawakalae) from the Middle Triassic Manda Beds of Tanzania among its basally branching members. This implies a greater undiscovered diversity of poposauroids during the Early Triassic, and supports that the group, and pseudosuchians more broadly, diversified rapidly following the End-Permian mass extinction.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsbl.2024.0136

ABSTRACT

The wrist of extant birds is highly specialized which permits folding of the forelimb in order to protect the pennaceous feathers when they are relaxed. This mechanism is absent in most non-avian theropods and is unknown in oviraptorosaurs because of the rarity of the specimens with well-preserved wrist. Here we give a detailed description of the wrist of two three-dimensionally preserved oviraptorosaurian Heyuannia huangi specimens from the Upper Cretaceous in Southern China. Heyuannia huangi possesses a highly specialized wrist with a strongly dorsoventrally compressed distal ulna, a larger radiale angle and a strongly convex semilunate carpal. The morphology of its wrist suggests that the distal ulna would not hinder the rotation of the manus, resulting in the smallest angle between the manus and the ulna being less than 90 degrees. The combination of the morphology of the wrist of oviraptorosaurs and the phylogenetic result indicates functional convergence in the wrist of oviraptorids and extant birds.

LINK(S)

https://peerj.com/articles/17669/
https://peerj.com/articles/17669.pdf

ABSTRACT

The Lower Jurassic (lower Toarcian) Grimmen Formation (formerly known as "Green Series") of Mecklenburg and Western Pomerania (Northeast Germany) yielded two articulated anterior skeletons of fossil fish, which represent a new lepisosteiform genus and species: Mengius acutidens gen. et sp. nov. The new taxon is described. Osteology of the species is most similar to the contemporaneous species of Lepidotes Agassiz. It differs from Lepidotes in having a non-tritoral dentition and a differently shaped operculum. A cladistic analysis shows Mengius acutidens gen. et sp. nov. to be the sister taxon of Lepidotes, accordingly, the new species is assigned to the family Lepidotidae Agassiz. The occurrence of M. acutidens emphasises the endemic character of the lower Toarcian Grimmen Formation fish fauna of Northeast Germany.

LINK(S)

https://link.springer.com/article/10.1007/s12542-023-00683-5
https://link.springer.com/content/pdf/10.1007/s12542-023-00683-5.pdf

ABSTRACT

A new iguanodontian dinosaur, Comptonatus chasei gen. et sp. nov., is described from the Lower Cretaceous Wessex Formation of the Isle of Wight. These strata provide an important record of a critical time in the development of iguanodontian diversity. The specimen, which is described here for the first time, was found and excavated in 2013 and represents the most complete iguanodontian skeleton discovered in the Wealden Group for a century. A new taxon is diagnosed by several autapomorphies found in the neurocranium, teeth, coracoid and other parts of the body, together with a unique suite of characters. These include a dentary with a straight ventral border, and a markedly expanded prepubic blade. These features set it apart from the sympatric Mantellisaurus atherfieldensis, Brighstoneus simmondsi and Iguanodon cf. bernissartensis, increasing the known diversity of this clade in the Barremian–early Aptian of England.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/14772019.2024.2346573

ABSTRACT

The Portezuelo Formation preserves an outstanding record of the upper Turonian – lower Coniacian. Despite the discovery of a significant quantity of sauropod fossil material from the formation, only two species have been formally described to date: Malarguesaurus florenciae and Futalognkosaurus dukei. Here we present new sauropod material mostly composed of non-articulated caudal vertebrae (MCF-PVPH 916 and 917) that belong to two titanosauriforms on the basis of the following features: anterior caudal vertebrae with procoelous-opisthoplatyan articulations, transverse processes that reach the posterior articular face of the centrum and neural spines with a transverse width of around 50% of their anteroposterior length; anterior and middle caudal vertebrae with the neural arch restricted to the anterior half of the centrum; middle caudal centra with circular cross-section. Phylogenetic analysis recovers the new material in close relation to Malarguesaurus within a monophyletic clade at the base of Somphospondyli. This clade shares large pedicel height with a vertical anterior border on the middle caudal vertebrae, a vertical orientation of the neural spines on the distalmost middle caudal vertebrae and proximalmost posterior caudal vertebrae, and subequal relative lengths of the proximal ulnar condylar processes. The specimens presented here are distinct not only from Futalognkosaurus, but also from other indeterminate titanosaurian remains from the same formation. However, there are no significant differences between the specimen MCF-PVPH 917 and Malarguesaurus, but there are differences between the posterior caudal vertebrae of MCF-PVPH 916 and Malarguesaurus, so they could be considered different species. Whilst we err on the side of caution in not naming new taxa here, the two specimens significantly expand what we know about sauropods in the Turonian–Coniacian ecosystems of Patagonia, which will continue to do so as more material is discovered.

LINK(S)

https://bmcecolevol.biomedcentral.com/articles/10.1186/s12862-024-02280-9
https://bmcecolevol.biomedcentral.com/counter/pdf/10.1186/s12862-024-02280-9.pdf

ABSTRACT

Thescelosaurines are a group of early diverging, ornithischian dinosaurs notable for their conservative bauplans and mosaic of primitive features. Although abundant within the latest Cretaceous ecosystems of North America, their record is poor to absent in earlier assemblages, leaving a large gap in our understanding of their evolution, origins, and ecological roles. Here we report a new small bodied thescelosaurine—Fona herzogae gen. et sp. nov.—from the Mussentuchit Member of the Cedar Mountain Formation, Utah, USA. Fona herzogae is represented by multiple individuals, representing one of the most comprehensive skeletal assemblages of a small bodied, early diverging ornithischian described from North America to date. Phylogenetic analysis recovers Fona as the earliest member of Thescelosaurinae, minimally containing Oryctodromeus, and all three species of Thescelosaurus, revealing the clade was well-established in North America by as early as the Cenomanian, and distinct from, yet continental cohabitants with, their sister clade, Orodrominae. To date, orodromines and thescelosaurines have not been found together within a single North American ecosystem, suggesting different habitat preferences or competitive exclusion. Osteological observations reveal extensive intraspecific variation across cranial and postcranial elements, and a number of anatomical similarities with Oryctodromeus, suggesting a shared semi-fossorial lifestyle.

LINK(S)

https://anatomypubs.onlinelibrary.wiley.com/doi/10.1002/ar.25505

ABSTRACT

The Upper Jurassic Morrison Formation sauropods Diplodocus (formerly “Seismosaurus”) hallorum and Supersaurus vivianae are quantifiably the largest dinosaurian taxa from the formation, as well as being among the largest dinosaurs in the world. Their extreme body size (in particular body length, c. 50+ m) has fascinated the paleontological community since their discoveries and has sparked an ongoing discussion on the trends and limits of Morrison Formation sauropod body size. Although not an undeviating proxy, often the largest and skeletally most mature specimens are among the rarest (as exemplified in Triceratops). While their body size has no phylogenetic bearing, the extreme size and potential eco and biological significance of these two sauropod taxa are frequently discussed. Whether these rare and titanically proportioned sauropod specimens are large-bodied, senescent or both is an often-repeating rhetoric. To definitively make maturational inferences about these taxa, we osteohistologically sampled the holotype of D. hallorum (NMMNH P-25079) and the second known specimen of S. vivianae (WDC DMJ-021). Our age-determinant and maturational assessments indicate that both specimens were skeletally mature at their respective age of death. Retrocalculation methods for D. hallorum NMMNH P-25079 produce a maximum age-at-death estimation of 60 years, whereas S. vivianae WDC DMJ-021 lived well past skeletal maturity—so much so that reliable retrocalculated ages cannot be accurately determined at this time. Additionally, the rarity of such large sauropods within the Morrison Formation might be more parsimoniously explained as relating to their maturity as opposed to representing aberrant taxa on the Morrison landscape.

LINK(S)

https://onlinelibrary.wiley.com/doi/abs/10.1111/joa.14108

ABSTRACT

Scincidae is one of the most species-rich and cosmopolitan clades of squamate reptiles. Abundant disarticulated fossil material has also been attributed to this group, however, no complete pre-Cenozoic crown-scincid specimens have been found. A specimen in Burmite (99 MYA) is the first fossil that can be unambiguously referred to this clade. Our analyses place it as nested within extant skinks, supported by the presence of compound osteoderms formed by articulated small ostedermites. The specimen has a combination of dorsal and ventral compound osteoderms and overlapping cycloid scales that is limited to skinks. We propose that this type of osteoderm evolved as a response to an increased overlap of scales, and to reduced stiffness of the dermal armour. Compound osteoderms could be a key innovation that facilitated diversification in this megadiverse family.

LINK(S)

https://www.nature.com/articles/s41598-024-66451-w
https://www.nature.com/articles/s41598-024-66451-w.pdf

ABSTRACT

New remains of a sea turtle from the San Carlos quarry (Upper Cretaceous, Campanian), Austin Formation in the north of Coahuila state, Mexico, are reported. San Carlos quarry is composed of limestones and its Campanian age is based on the presence of the ammonites Scaphites hippocrepis and Delawarella delawarensis. In addition to the presence of turtles, this quarry also contained ammonites, bivalves, crabs, sea urchins, bony fish remains, and shark teeth. The study material is housed at Museo Paleontológico de Múzquiz. The preserved fossil elements correspond to postcranial elements, which present morphological characteristics that allowed them to be identified as belonging to a small-sized turtle related to Protostegidae. These new sea turtle remains expand the knowledge and distribution of Protostegidae along the Western Interior Seaway, where large and medium-sized sea turtles were distributed.

LINK(S)

http://ojs-igl.unam.mx/index.php/Paleontologia/article/view/718
http://ojs-igl.unam.mx/index.php/Paleontologia/article/view/718/774

ABSTRACT

The El Mers I and II formations (Middle Jurassic, Bathonian) are geological units outcropping in the folded Middle Atlas of Morocco rich in body and trace fossils of dinosaurs. The numerous tracksites of these units have been little studied and are severely affected by ongoing erosion (e.g., seasonal flooding) and, to a lesser degree, human activities (e.g., urbanisation). The aim of this project is to fully document and interpret the dinosaur tracks of two historic sites and four new sites discovered in the El Mers area using digital photogrammetry. The ichnofauna comprises abundant tracks and trackways of theropod and sauropod dinosaurs as well as of probable crocodylomorph tracks. The theropod tracks include several footprints of high anatomical fidelity, but the majority of the discovered tracks are identified to be penetrative tracks, with one site preserving abundant swim tracks. The sites preserve both small and enormous sauropod tracks. The enormous sauropod tracks are among the largest known worldwide, with a pes track length of up to 130 cm. The obtained 3D models are compared with site maps created by analogue mapping performed more than 15 years ago of the historical sites, revealing how erosion has both destructed surfaces and exposed new ones. The application of photogrammetry allows for the rapid collection of accurate high-resolution data with sustainable costs. The resulting 3D models can be used in research to digitally conserve threatened sites, and as a basis for knowledge transfer to the public. The present contribution encourages the intellectual, logistical, and social involvement of the local population to collaborate with scientists for the conservation of the rich geological heritage. Furthermore, scientific investigations in this area could shift from academic-only research to research focused on conservation and geotourism initiatives that involve local communities.

LINK(S)

https://www.sciencedirect.com/science/article/abs/pii/S0016787824000373?via%3Dihub

ABSTRACT

Headbutting is a combative behavior most popularly portrayed and exemplified in the extant bighorn sheep (Ovis canadensis). When behaviorally proposed in extinct taxa, these organisms are oft depicted Ovis-like as having used modified cranial structures to combatively slam into one another. The combative behavioral hypothesis of headbutting has a long and rich history in the vertebrate fossil literature (not just within Dinosauria), but the core of this behavioral hypothesis in fossil terrestrial vertebrates is associated with an enlarged osseous cranial dome—an osteological structure with essentially no current counterpart. One confounding issue found in the literature is that while the term “headbutting” sounds simplistic enough, little terminology has been used to describe this hypothesized behavior. And pertinent to this special issue, potential brain trauma and the merits of such proposed pugilism have been assessed largely from the potential deformation of the overlying osseous structure; despite the fact that extant taxa readily show that brain damage can and does occur without osteological compromise. Additionally, the extant taxa serving as the behavioral counterpart for comparison are critical, not only because of the combative behaviors and morphologies they display, but also the way they engage in such behavior. Sheep (Ovis), warthogs (Phacochoerus), and bison (Bison) all engage in various forms of “headbutting”, but the cranial morphologies and the way each engages in combat is markedly different. To hypothesize that an extinct organism engaged in headbutting like an extant counterpart in theory implies specific striking:contacting surfaces, speed, velocity, and overall how that action was executed. This review examines the history and usage of the headbutting behavioral hypothesis in these dome-headed fossil taxa, their respective extant behavioral counterparts, and proposes a protocol for specific behavioral terms relating to headbutting to stem future confusion. We also discuss the disparate morphology of combative cranial structures in the fossil record, and the implications of headbutting-induced brain injury in extinct taxa. Finally, we conclude with some potential implications for artistic reconstructions of fossil taxa regarding this behavioral repertoire.

LINK(S)

https://anatomypubs.onlinelibrary.wiley.com/doi/abs/10.1002/ar.25526

ABSTRACT

The Late Triassic was home to great tetrapod diversity, with a mixture of endemic Triassic groups and others with extant descendants. These two groups are represented in microvertebrate accumulations, but their fossils are mixed and fragmentary, leading to challenges in confidently identifying them. Among the Triassic endemic groups, drepanosauromorphs are among the most unusual and easily recognized, but many details of their anatomy are obscured by the lack of three-dimensional and matrix-free specimens. Here we describe new material, including a new species, using isolated but three-dimensional drepanosauromorph elements from the Homestead Site at Garita Creek, an Upper Triassic microvertebrate locality near Garita Creek, New Mexico. This site has thus far yielded dozens of isolated drepanosauromorph specimens, including manual/pedal unguals of at least three morphotypes, vertebrae, and caudal unguals (= tail claws). At least two drepanosauromorph species are present based on distinct enlarged ungual morphotypes, with one representing a new Skybalonyx-like species, Unguinychus onyx gen. et sp. nov., and a second form similar to Drepanosaurus. Unguinychus onyx may have been fossorial whereas the second morphotype likely represents an arboreal species, possibly indicating that contemporary drepanosauromorphs had different ecologies. For the first time, we report a potential “small” ungual morphotype, and we present a partial caudal ungual exhibiting features distinct from manual and pedal unguals. The identification of isolated and three-dimensional drepanosauromorph fossils expands the diversity of the clade and demonstrates the usefulness of incorporating microvertebrate data into assemblage studies.

LINK(S)

https://www.tandfonline.com/doi/full/10.1080/02724634.2024.2363202

ABSTRACT

Pterosaurs were the first vertebrates to achieve powered flight. Early pterosaurs had long stiff tails with a mobile base that could shift their center of mass, potentially benefiting flight control. These tails ended in a tall, thin soft tissue vane that would compromise aerodynamic control and efficiency if it fluttered during flight like a flag in the wind. Maintaining stiffness in the vane would have been crucial in early pterosaur flight, but how this was achieved has been unclear, especially since vanes were lost in later pterosaurs and are absent in birds and bats. Here we use Laser-Stimulated Fluorescence imaging to reveal a cross-linking lattice within the tail vanes of early pterosaurs. The lattice supported a sophisticated dynamic tensioning system used to maintain vane stiffness, allowing the whole tail to augment flight control and the vane to function as a display structure.

LINK(S)

https://www.biorxiv.org/content/10.1101/2024.07.01.601487v1
https://www.biorxiv.org/content/biorxiv/early/2024/07/03/2024.07.01.601487.full.pdf

ABSTRACT

Current hypotheses of early tetrapod evolution posit close ecological and biogeographic ties to the extensive coal-producing wetlands of the Carboniferous palaeoequator with rapid replacement of archaic tetrapod groups by relatives of modern amniotes and lissamphibians in the late Carboniferous (about 307 million years ago). These hypotheses draw on a tetrapod fossil record that is almost entirely restricted to palaeoequatorial Pangea (Laurussia)1,2. Here we describe a new giant stem tetrapod, Gaiasia jennyae, from high-palaeolatitude (about 55° S) early Permian-aged (about 280 million years ago) deposits in Namibia that challenges this scenario. Gaiasia is represented by several large, semi-articulated skeletons characterized by a weakly ossified skull with a loosely articulated palate dominated by a broad diamond-shaped parasphenoid, a posteriorly projecting occiput, and enlarged, interlocking dentary and coronoid fangs. Phylogenetic analysis resolves Gaiasia within the tetrapod stem group as the sister taxon of the Carboniferous Colosteidae from Euramerica. Gaiasia is larger than all previously described digited stem tetrapods and provides evidence that continental tetrapods were well established in the cold-temperate latitudes of Gondwana during the final phases of the Carboniferous–Permian deglaciation. This points to a more global distribution of continental tetrapods during the Carboniferous–Permian transition and indicates that previous hypotheses of global tetrapod faunal turnover and dispersal at this time2,3 must be reconsidered.

LINK(S)

https://www.nature.com/articles/s41586-024-07572-0

ABSTRACT

Stegosaur tracks were unknown until the identification of Deltapodus more than 20 years ago. Currently, the Iberian Peninsula, especially Teruel Province, is one of the areas globally with the most occurrences of these tracks. However, their identification, based on the global record, is problematic due to their similarities with sauropod tracks. A review of the largest number of analyzed Deltapodus tracks globally, including the holotype of D. ibericus and a description of new occurrences, has been carried out. Our research shows substantial morphological variations, but all the studied tracks can be considered D. ibericus based on the manus morphology and the morphometric data. These variations are related to substrate differences and/or different dynamic foot postures (possibly ontogenetically related) during locomotion, as evidenced by changes within the same trackway. We provide detailed comparisons via 3D modeling with sauropod tracks, and our data show that they generally have proportionally longer manus and wider pes because of the differences in the metapodial bones. The scarcity of stegosaur trackways in the fossil record has prevented the identification of gregarious behavior in this group of herbivorous dinosaurs. Two of the studied tracksites show evidence of this behavior, being the only examples among stegosaurs described thus far in the fossil record.

LINK(S)

https://www.nature.com/articles/s41598-024-64298-9
https://www.nature.com/articles/s41598-024-64298-9.pdf

ABSTRACT

Dinosaur tracks have a long history of discovery and study in the UK, but track sites for sauropodomorph dinosaurs—the group that included the giant, graviportal herbivorous sauropods—are comparatively rare. Here, we provide a description of a sauropod dinosaur track site at Spyway Quarry in Dorset, southern England. The tracks at Spyway were discovered in the late 1990s and occur in the Stair Hole Member of the Durlston Formation in the Purbeck Limestone Group, of earliest Cretaceous age. More than 130 individual tracks of large sauropod dinosaurs are present at the site, but they are generally poorly preserved and do not form clear trackways, although it is likely that they represent multiple individuals. They provide further evidence for sauropods living in or passing through coastal lagoonal environments. Although poorly preserved, Spyway represents the largest in situ dinosaur track site currently accessible within the Purbeck Group, with considerable potential for further discoveries through ongoing quarrying in the surrounding area.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsos.240583

ABSTRACT

Feather moulting is a crucial process in the avian life cycle, which evolved to maintain plumage functionality. However, moulting involves both energetic and functional costs. During moulting, plumage function temporarily decreases between the shedding of old feathers and the full growth of new ones. In flying taxa, a gradual and sequential replacement of flight feathers evolved to maintain aerodynamic capabilities during the moulting period. Little is known about the moult strategies of non-avian pennaraptoran dinosaurs and stem birds, before the emergence of crown lineage. Here, we report on two Early Cretaceous pygostylian birds from the Yixian Formation (125 mya), probably referable to Confuciusornithiformes, exhibiting morphological characteristics that suggest a gradual and sequential moult of wing flight feathers. Short primary feathers interpreted as immature are symmetrically present on both wings, as is typical among extant flying birds. Our survey of the enormous collection of the Tianyu Museum confirms previous findings that evidence of active moult in non-neornithine pennaraptorans is rare and likely indicates a moult cycle greater than one year. Documenting moult in Mesozoic feathered dinosaurs is critical for understanding their ecology, locomotor ability and the evolution of this important life-history process in birds.

LINK(S)

https://royalsocietypublishing.org/doi/10.1098/rsbl.2024.0106

ABSTRACT

Stegosaurs are a minor but iconic clade of ornithischian dinosaurs, yet due to a poor fossil record, their early evolution is poorly understood. Here, we describe a new stegosaur, Baiyinosaurus baojiensis, gen. et sp. nov. from the Middle Jurassic Wangjiashan Formation of the Pingchuan District, Baiyin City, Gansu Province, China. The frontal of Baiyinosaurus possesses a unique characteristic among Stegosauria: it is wider than long and contributes to both the medial and anterior margins of the supratemporal fenestra. The character combinations of dorsal vertebrae of Baiyinosaurus are also different to other stegosaurs: its neural arches are not greatly elongated, its parapophyses are well developed, and its neural spines are axially expanded in lateral. The features of the frontal and vertebrae of Baiyinosaurus are reminiscent of basally branching thyreophorans, indicating that Baiyinosaurus is transitional in morphology between early thyreophorans and early-diverging stegosaurs. Systematic analysis shows that Baiyinosaurus is an early-diverging stegosaur.

LINK(S)

https://www.nature.com/articles/s41598-024-66280-x
https://www.nature.com/articles/s41598-024-66280-x.pdf

ABSTRACT

Alioramin theropods, a unique lineage within the clade Tyrannosauridae, are characterized by relatively diminutive size and longirostrine skull with increased tooth counts. Based on this unusual morphology, it has been suggested that alioramins had a unique ecological niche for tyrannosaurids, primarily hunting small prey items. However, there has been no quantitative evidence suggested for this claim. In this work, mandibular force profiles of the alioramins Alioramus altai and Qianzhousaurus sinensis are examined. The bending strength of the symphyseal region is found to be stronger than the middentary in both taxa, as in other tyrannosaurids. However, the relative mandibular force at the symphyseal region in alioramins is significantly higher, suggesting this region went through significantly less torsional stresses compared to non-alioramin tyrannosaurids. This may also suggest they used shearing, slashing bites more frequently in hunting and feeding than other tyrannosaurids. Additionally, the bending force at the middentary, which is a valid proxy for a bite force in theropods, of alioramins is found to be both relatively and absolutely lower than other tyrannosaurids, or even non-tyrannosaurid theropods of similar mandibular length. Such results strongly imply alioramins were unsuited for delivering powerful bites and enduring high torsional loads, and are consistent with the previous hypothesis that alioramins mainly fed on small prey that did not require a strong bite force or mandibular symphysis capable of resisting high torsional stresses to capture and manipulating.

LINK(S)

https://www.idunn.no/doi/10.18261/let.57.2.6
https://www.idunn.no/doi/epdf/10.18261/let.57.2.6

ABSTRACT

Ninu (greater bilby, Macrotis lagotis) are desert-dwelling, culturally and ecologically important marsupials. In collaboration with Indigenous rangers and conservation managers, we generated the Ninu chromosome-level genome assembly (3.66 Gbp) and genome sequences for the extinct Yallara (lesser bilby, Macrotis leucura). We developed and tested a scat single-nucleotide polymorphism panel to inform current and future conservation actions, undertake ecological assessments and improve our understanding of Ninu genetic diversity in managed and wild populations. We also assessed the beneficial impact of translocations in the metapopulation (N = 363 Ninu). Resequenced genomes (temperate Ninu, 6; semi-arid Ninu, 6; and Yallara, 4) revealed two major population crashes during global cooling events for both species and differences in Ninu genes involved in anatomical and metabolic pathways. Despite their 45-year captive history, Ninu have fewer long runs of homozygosity than other larger mammals, which may be attributable to their boom–bust life history. Here we investigated the unique Ninu biology using 12 tissue transcriptomes revealing expression of all 115 conserved eutherian chorioallantoic placentation genes in the uterus, an XY1Y2 sex chromosome system and olfactory receptor gene expansions. Together, we demonstrate the holistic value of genomics in improving key conservation actions, understanding unique biological traits and developing tools for Indigenous rangers to monitor remote wild populations.

LINK(S)

https://www.nature.com/articles/s41559-024-02436-2
https://www.nature.com/articles/s41559-024-02436-2.pdf