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1.
Proc Biol Sci ; 291(2023): 20240537, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38747705

RESUMO

The noasaurid ceratosaur Kiyacursor longipes gen. et sp. nov. is described based on a fragmentary skeleton including cervical vertebra, pectoral girdle, humerus and hind limbs from the Lower Cretaceous (Aptian) Ilek Formation at Shestakovo 1 locality in Western Siberia, Russia. This is the first ceratosaur from the Early Cretaceous of Asia, extending the stratigraphic range of Ceratosauria by 40 Myr on that continent. Kiyacursor shares unique hind limb proportions with Elaphrosaurus and Limusaurus, suggesting improved cursorial ability. These taxa show an ostrich-like specialization of the pes, with a large third metatarsal and greatly reduced second metatarsal. By contrast, all other fast running non-avian theropod dinosaurs have an arctometatarsalian pes, with the third metatarsal strongly reduced proximally. The new taxon lived in the Early Cretaceous ecosystem containing a number of other Jurassic relics, such as stem salamanders, protosuchian and shartegosuchid crocodyliforms, tritylodontid synapsids and docodontan mammaliaforms.


Assuntos
Dinossauros , Fósseis , Animais , Dinossauros/anatomia & histologia , Dinossauros/classificação , Fósseis/anatomia & histologia , Sibéria , Evolução Biológica
2.
Nat Ecol Evol ; 8(5): 1048, 2024 May.
Artigo em Inglês | MEDLINE | ID: mdl-38741008
3.
PeerJ ; 12: e16541, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38774542

RESUMO

In the Western Scheldt Estuary near the Belgian-Dutch border, middle to late Eocene strata crop out at the current seafloor. Most vertebrae of large Eocene basilosaurid taxa from this area were previously described in several papers. They represent three morphotypes: elongated vertebrae of a large species of Pachycetus (Morphotype 1b), a not-elongated vertebra of a large 'dorudontid' basilosaurid (Morphotype 2) and 'shortened' vertebrae of a new, unnamed taxon (Morphotype 3). This article deals with a still undescribed, smaller vertebra, NMR-16642, from this site. Our first aim was to date it by dinoflagellate cysts in adhering sediments. Yielding an age of about 38 Ma, it is one of the very few remains of basilosaurids from Europe, of which the age could be assessed with reasonable certainty. The vertebra, Morphotype 1a, is assigned to a small species of Pachycetus. High-quality CT scans are used to differentiate between NMR-16642, Morphotype 1a, and the large species of Pachycetus, Morphotype 1b. Another aim of this paper is to investigate the inner structure and vascularity of the study vertebra and that of the other morphotypes (1b, 2, 3) from this area by using high-quality CT scans. Notwithstanding differences in size, shape and compactness, the vertebral inner structure with a multi-layered cortex of periosteal bone, surrounding two cones of endosteal bone appears to be basically similar in all morphotypes. Apparently, this inner structure reflects the ontogenetic vertebral growth. An attempt to reconstruct the vascularity of the vertebrae reveals a remarkable pattern of interconnected vascular systems. From the dorsal and, if present, ventral foramina, vascular canals are running to a central vascular node. From this node a system of vascular canals goes to the epiphyseal ends, giving rise to separate systems for cortex and cones. It is the first time that the vascularity of vertebrae of archaeocetes is investigated.


Assuntos
Fósseis , Coluna Vertebral , Animais , Coluna Vertebral/anatomia & histologia , Coluna Vertebral/irrigação sanguínea , Mar do Norte , Dinossauros/anatomia & histologia , Dinossauros/classificação , Tomografia Computadorizada por Raios X
4.
Naturwissenschaften ; 111(3): 29, 2024 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-38713269

RESUMO

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.


Assuntos
Cabeça , Crânio , Animais , Fenômenos Biomecânicos/fisiologia , Crânio/anatomia & histologia , Crânio/fisiologia , Cabeça/anatomia & histologia , Cabeça/fisiologia , Voo Animal/fisiologia , Dinossauros/fisiologia , Dinossauros/anatomia & histologia , Fósseis
5.
Nat Commun ; 15(1): 4063, 2024 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-38773066

RESUMO

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.


Assuntos
Evolução Biológica , Dinossauros , Plumas , Fósseis , Melanossomas , Répteis , Pele , Animais , Plumas/anatomia & histologia , Dinossauros/anatomia & histologia , Pele/anatomia & histologia , Pele/metabolismo , Répteis/anatomia & histologia , Melanossomas/metabolismo , Melanossomas/ultraestrutura , Escamas de Animais/anatomia & histologia , Epiderme/anatomia & histologia , Epiderme/metabolismo , Epiderme/ultraestrutura , beta-Queratinas/metabolismo
6.
Commun Biol ; 7(1): 436, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38600295

RESUMO

Oviraptorosaurians were a theropod dinosaur group that reached high diversity in the Late Cretaceous. Within oviraptorosaurians, the later diverging oviraptorids evolved distinctive crania which were extensively pneumatised, short and tall, and had a robust toothless beak, interpreted as providing a powerful bite for their herbivorous to omnivorous diet. The present study explores the ability of oviraptorid crania to resist large mechanical stresses compared with other theropods and where this adaptation originated within oviraptorosaurians. Digital 3D cranial models were constructed for the earliest diverging oviraptorosaurian, Incisivosaurus gauthieri, and three oviraptorids, Citipati osmolskae, Conchoraptor gracilis, and Khaan mckennai. Finite element analyses indicate oviraptorosaurian crania were stronger than those of other herbivorous theropods (Erlikosaurus and Ornithomimus) and were more comparable to the large, carnivorous Allosaurus. The cranial biomechanics of Incisivosaurus align with oviraptorids, indicating an early establishment of distinctive strengthened cranial biomechanics in Oviraptorosauria, even before the highly modified oviraptorid cranial morphology. Bite modelling, using estimated muscle forces, suggests oviraptorid crania may have functioned closer to structural safety limits. Low mechanical stresses around the beaks of oviraptorids suggest a convergently evolved, functionally distinct rhamphotheca, serving as a cropping/feeding tool rather than for stress reduction, when compared with other herbivorous theropods.


Assuntos
Dinossauros , Fósseis , Animais , Crânio/anatomia & histologia , Dinossauros/anatomia & histologia , Herbivoria , Dieta
7.
PLoS One ; 19(4): e0298242, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38568908

RESUMO

Dinosauria debuted on Earth's stage in the aftermath of the Permo-Triassic Mass Extinction Event, and survived two other Triassic extinction intervals to eventually dominate terrestrial ecosystems. More than 231 million years ago, in the Upper Triassic Ischigualasto Formation of west-central Argentina, dinosaurs were just getting warmed up. At this time, dinosaurs represented a minor fraction of ecosystem diversity. Members of other tetrapod clades, including synapsids and pseudosuchians, shared convergently evolved features related to locomotion, feeding, respiration, and metabolism and could have risen to later dominance. However, it was Dinosauria that radiated in the later Mesozoic most significantly in terms of body size, diversity, and global distribution. Elevated growth rates are one of the adaptations that set later Mesozoic dinosaurs apart, particularly from their contemporary crocodilian and mammalian compatriots. When did the elevated growth rates of dinosaurs first evolve? How did the growth strategies of the earliest known dinosaurs compare with those of other tetrapods in their ecosystems? We studied femoral bone histology of an array of early dinosaurs alongside that of non-dinosaurian contemporaries from the Ischigualasto Formation in order to test whether the oldest known dinosaurs exhibited novel growth strategies. Our results indicate that the Ischigualasto vertebrate fauna collectively exhibits relatively high growth rates. Dinosaurs are among the fastest growing taxa in the sample, but they occupied this niche alongside crocodylomorphs, archosauriformes, and large-bodied pseudosuchians. Interestingly, these dinosaurs grew at least as quickly, but more continuously than sauropodomorph and theropod dinosaurs of the later Mesozoic. These data suggest that, while elevated growth rates were ancestral for Dinosauria and likely played a significant role in dinosaurs' ascent within Mesozoic ecosystems, they did not set them apart from their contemporaries.


Assuntos
Dinossauros , Animais , Dinossauros/anatomia & histologia , Evolução Biológica , Ecossistema , Fósseis , Osso e Ossos , Filogenia , Mamíferos
8.
BMC Ecol Evol ; 24(1): 46, 2024 Apr 16.
Artigo em Inglês | MEDLINE | ID: mdl-38627692

RESUMO

BACKGROUND: Tooth replacement patterns of early-diverging ornithischians, which are important for understanding the evolution of the highly specialized dental systems in hadrosaurid and ceratopsid dinosaurs, are poorly known. The early-diverging neornithischian Jeholosaurus, a small, bipedal herbivorous dinosaur from the Early Cretaceous Jehol Biota, is an important taxon for understanding ornithischian dental evolution, but its dental morphology was only briefly described previously and its tooth replacement is poorly known. RESULTS: CT scanning of six specimens representing different ontogenetic stages of Jeholosaurus reveals significant new information regarding the dental system of Jeholosaurus, including one or two replacement teeth in nearly all alveoli, relatively complete tooth resorption, and an increase in the numbers of alveoli and replacement teeth during ontogeny. Reconstructions of Zahnreihen indicate that the replacement pattern of the maxillary dentition is similar to that of the dentary dentition but with a cyclical difference. The maxillary tooth replacement rate in Jeholosaurus is probably 46 days, which is faster than that of most other early-diverging ornithischians. During the ontogeny of Jeholosaurus, the premaxillary tooth replacement rate slows from 25 days to 33 days with similar daily dentine formation. CONCLUSIONS: The tooth replacement rate exhibits a decreasing trend with ontogeny, as in Alligator. In a phylogenetic context, fast tooth replacement and multi-generation replacement teeth have evolved at least twice independently in Ornithopoda, and our analyses suggest that the early-diverging members of the major ornithischian clades exhibit different tooth replacement patterns as an adaption to herbivory.


Assuntos
Dinossauros , Dente , Animais , Filogenia , Dinossauros/anatomia & histologia , Herbivoria , Fósseis , Dente/diagnóstico por imagem , Dente/cirurgia , Dente/anatomia & histologia
9.
Sci Rep ; 14(1): 6528, 2024 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-38499621

RESUMO

The Serrote do Letreiro Site, found on the northwest periphery of the Sousa Basin, Brazil, presents a remarkable convergence of paleontological and archaeological elements. It is constituted of sub-horizontal "lajeiros", or rock outcrops, intermingled with endemic Caatinga vegetation. The three prominent outcrops feature fossilized footprints of theropod, sauropod, and iguanodontian dinosaurs from the Early Cretaceous Period. Adjacent to these dinosaur tracks, indigenous petroglyphs adorn the surface. The petroglyphs, mainly characterized by circular motifs, maintain a striking resemblance to other petroglyphs found in the states of Paraíba and Rio Grande do Norte. This study primarily endeavors to delineate the site's major characteristics while concentrating on the relationship between the dinosaur footprints and the petroglyphs. It concurrently assesses the preservation status of this invaluable record, shedding light on its implications for the realms of paleontology, archaeology, and cultural heritage studies.


Assuntos
Dinossauros , Golfinhos , Animais , Dinossauros/anatomia & histologia , Brasil , Paleontologia , Arqueologia , Fósseis
10.
Sci Rep ; 14(1): 3665, 2024 02 13.
Artigo em Inglês | MEDLINE | ID: mdl-38351204

RESUMO

In the Late Cretaceous, northern and southern hemispheres evolved distinct dinosaurian faunas. Titanosaurians and abelisaurids dominated the Gondwanan continents; hadrosaurids, ceratopsians and tyrannosaurs dominated North America and Asia. Recently, a lambeosaurine hadrosaurid, Ajnabia odysseus, was reported from the late Maastrichtian phosphates of the Oulad Abdoun Basin Morocco, suggesting dispersal between Laurasia and Gondwana. Here we report new fossils from the phosphates of Morocco showing lambeosaurines achieved high diversity in the late Maastrichtian of North Africa. A skull represents a new dwarf lambeosaurine, Minqaria bata. Minqaria resembles Ajnabia odysseus in size, but differs in the ventrally positioned jugal facet and sinusoidal toothrow. The animal is small, ~ 3.5 m long, but the fused braincase shows it was mature. A humerus and a femur belong to larger hadrosaurids, ~ 6 m long, implying at least three species coexisted. The diversity of hadrosaurids in Europe and Africa suggests a dispersal-driven radiation, with lambeosaurines diversifying to take advantage of low ornithischian diversity. African lambeosaurines are small compared to North American and Asia hadrosaurids however, perhaps due to competition with titanosaurians. Hadrosaurids are unknown from eastern Africa, suggesting Moroccan hadrosaurids may be part of a distinct insular fauna, and represent an island radiation.


Assuntos
Dinossauros , Animais , Marrocos , Dinossauros/anatomia & histologia , Fósseis , Crânio/anatomia & histologia , África do Norte , Fosfatos , Filogenia
11.
Nat Commun ; 15(1): 854, 2024 Feb 16.
Artigo em Inglês | MEDLINE | ID: mdl-38365765

RESUMO

Our knowledge of vertebrate functional evolution depends on inferences about joint function in extinct taxa. Without rigorous criteria for evaluating joint articulation, however, such analyses risk misleading reconstructions of vertebrate animal motion. Here we propose an approach for synthesizing raycast-based measurements of 3-D articular overlap, symmetry, and congruence into a quantitative "articulation score" for any non-interpenetrating six-degree-of-freedom joint configuration. We apply our methodology to bicondylar hindlimb joints of two extant dinosaurs (guineafowl, emu) and, through comparison with in vivo kinematics, find that locomotor joint poses consistently have high articulation scores. We then exploit this relationship to constrain reconstruction of a pedal walking stride cycle for the extinct dinosaur Deinonychus antirrhopus, demonstrating the utility of our approach. As joint articulation is investigated in more living animals, the framework we establish here can be expanded to accommodate additional joints and clades, facilitating improved understanding of vertebrate animal motion and its evolution.


Assuntos
Dinossauros , Caminhada , Animais , Articulações , Membro Posterior , Dinossauros/anatomia & histologia , Fenômenos Biomecânicos
12.
PLoS One ; 19(2): e0297637, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38354167

RESUMO

Fossil deposits with exceptional preservation ("lagerstätten") provide important details not typically preserved in the fossil record, such that they hold an outsized influence on our understanding of biodiversity and evolution. In particular, the potential bias imparted by this so-called "lagerstätten effect" remains a critical, but underexplored aspect of reconstructing evolutionary relationships. Here, we quantify the amount of phylogenetic information available in the global fossil records of 1,327 species of non-avian theropod dinosaurs, Mesozoic birds, and fossil squamates (e.g., lizards, snakes, mosasaurs), and then compare the influence of lagerstätten deposits on phylogenetic information content and taxon selection in phylogenetic analyses to other fossil-bearing deposits. We find that groups that preserve a high amount of phylogenetic information in their global fossil record (e.g., non-avian theropods) are less vulnerable to a "lagerstätten effect" that leads to disproportionate representation of fossil taxa from one geologic unit in an evolutionary tree. Additionally, for each taxonomic group, we find comparable amounts of phylogenetic information in lagerstätten deposits, even though corresponding morphological character datasets vary greatly. Finally, we unexpectedly find that ancient sand dune deposits of the Late Cretaceous Gobi Desert of Mongolia and China exert an anomalously large influence on the phylogenetic information available in the squamate fossil record, suggesting a "lagerstätten effect" can be present in units not traditionally considered lagerstätten. These results offer a phylogenetics-based lens through which to examine the effects of exceptional fossil preservation on biological patterns through time and space, and invites further quantification of evolutionary information in the rock record.


Assuntos
Dinossauros , Lagartos , Animais , Filogenia , Fósseis , Evolução Biológica , Lagartos/genética , Lagartos/anatomia & histologia , Dinossauros/genética , Dinossauros/anatomia & histologia , Aves
13.
Commun Biol ; 7(1): 168, 2024 Feb 10.
Artigo em Inglês | MEDLINE | ID: mdl-38341492

RESUMO

Many modifications to the skull and brain anatomy occurred along the lineage encompassing non-avialan theropod dinosaurs and modern birds. Anatomical changes to the endocranium include an enlarged endocranial cavity, relatively larger optic lobes that imply elevated visual acuity, and proportionately smaller olfactory bulbs that suggest reduced olfactory capacity. Here, we use micro-computed tomographic (µCT) imaging to reconstruct the endocranium and its neuroanatomical features from an exceptionally well-preserved skull of Sinovenator changii (Troodontidae, Theropoda). While its overall morphology resembles the typical endocranium of other troodontids, Sinovenator also exhibits unique endocranial features that are similar to other paravian taxa and non-maniraptoran theropods. Landmark-based geometric morphometric analysis on endocranial shape of non-avialan and avialan dinosaurs points to the overall brain morphology of Sinovenator most closely resembling that of Archaeopteryx, thus indicating acquisition of avialan-grade brain morphology in troodontids and wide existence of such architecture in Maniraptora.


Assuntos
Evolução Biológica , Dinossauros , Animais , Filogenia , Dinossauros/anatomia & histologia , Fósseis , Encéfalo/diagnóstico por imagem , Encéfalo/anatomia & histologia
14.
Proc Natl Acad Sci U S A ; 121(8): e2306639121, 2024 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-38346196

RESUMO

As a fundamental ecological aspect of most organisms, locomotor function significantly constrains morphology. At the same time, the evolution of novel locomotor abilities has produced dramatic morphological transformations, initiating some of the most significant diversifications in life history. Despite significant new fossil evidence, it remains unclear whether volant locomotion had a single or multiple origins in pennaraptoran dinosaurs and the volant abilities of individual taxa are controversial. The evolution of powered flight in modern birds involved exaptation of feathered surfaces extending off the limbs and tail yet most studies concerning flight potential in pennaraptorans do not account for the structure and morphology of the wing feathers themselves. Analysis of the number and shape of remex and rectrix feathers across a large dataset of extant birds indicates that the number of remiges and rectrices and the degree of primary vane asymmetry strongly correlate with locomotor ability revealing important functional constraints. Among these traits, phenotypic flexibility varies reflected by the different rates at which morphological changes evolve, such that some traits reflect the ancestral condition, whereas others reflect current locomotor function. While Mesozoic birds and Microraptor have remex morphologies consistent with extant volant birds, that of anchiornithines deviate significantly providing strong evidence this clade was not volant. The results of these analyses support a single origin of dinosaurian flight and indicate the early stages of feathered wing evolution are not sampled by the currently available fossil record.


Assuntos
Evolução Biológica , Dinossauros , Animais , Filogenia , Voo Animal , Plumas/anatomia & histologia , Locomoção , Dinossauros/anatomia & histologia , Fósseis , Asas de Animais/anatomia & histologia , Aves/anatomia & histologia
15.
BMC Ecol Evol ; 24(1): 20, 2024 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-38336630

RESUMO

BACKGROUND: Living birds comprise the most speciose and anatomically diverse clade of flying vertebrates, but their poor early fossil record and the lack of resolution around the relationships of the major clades have greatly obscured extant avian origins. RESULTS: Here, I describe a Late Cretaceous bird from North America based on a fragmentary skeleton that includes cranial material and portions of the forelimb, hindlimb, and foot and is identified as a juvenile based on bone surface texture. Several features unite this specimen with crown Aves, but its juvenile status precludes the recognition of a distinct taxon. The North American provenance of the specimen supports a cosmopolitan distribution of early crown birds, clashes with the hypothesized southern hemisphere origins of living birds, and demonstrates that crown birds and their closest relatives coexisted with non-avian dinosaurs that independently converged on avian skeletal anatomy, such as the alvarezsaurids and dromaeosaurids. CONCLUSIONS: By revealing the ecological and biogeographic context of Cretaceous birds within or near the crown clade, the Lance Formation specimen provides new insights into the contingent nature of crown avian survival through the Cretaceous-Paleogene mass extinction and the subsequent origins of living bird diversity.


Assuntos
Dinossauros , Animais , Dinossauros/anatomia & histologia , Filogenia , Ecossistema , Aves/anatomia & histologia , América do Norte , Crânio/anatomia & histologia
16.
Nat Ecol Evol ; 8(3): 591, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38378805
17.
J Anat ; 244(6): 959-976, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38284134

RESUMO

Phytosaurs are a group of Upper Triassic semi-aquatic archosauriform reptiles. Their variable skull morphology forms the foundation of our understanding of their relationships and paleoecology, while only a few studies have focused on demonstrating the existence of postcranial variation. The numbers of vertebrae in the sacrum are thought to vary from two, the plesiomorphic condition for archosauriforms, to three, with the addition of a sacralized dorsal (i.e., dorsosacral) vertebra. In this study, we demonstrate the presence of a sacralized first caudal (i.e., caudosacral) vertebra in a sacrum belonging to Machaeroprosopus mccauleyi. We rule out taphonomic distortion or pathology as explanations for the inclusion of this element in the sacrum, suggesting instead that it occurred through modifications of the same developmental processes that likely produced dorsosacral vertebrae in phytosaurs. Additionally, we show that a dorsosacral vertebra is common in phytosaur specimens from the Chinle Formation and Dockum Group of the southwestern United States and suggest that it may be widespread among phytosaurs. The addition of sacral vertebrae potentially aided adaptation to larger body sizes or more terrestrial lifestyles in certain taxa.


Assuntos
Fósseis , Sacro , Animais , Sacro/anatomia & histologia , Dinossauros/anatomia & histologia , Evolução Biológica , Répteis/anatomia & histologia , Crânio/anatomia & histologia , Filogenia
18.
Proc Biol Sci ; 291(2015): 20231713, 2024 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-38229513

RESUMO

Teeth evolved early in vertebrate evolution, and their morphology reflects important specializations in diet and ecology among species. The toothless jaws (edentulism) in extant birds likely coevolved with beak keratin, which functionally replaced teeth. However, extinct dinosaurs lost teeth multiple times independently and exhibited great variation in toothrow distribution and rhamphotheca-like keratin structures. Here, we use rostral jawbone surface texture as a proxy for rostral keratin covering and phylogenetic comparative models to test for the influence of rostral keratin on toothrow distribution in Mesozoic dinosaurs. We find that the evolution of rostral keratin covering explains partial toothrow reduction but not jaw toothlessness. Toothrow reduction preceded the evolution of rostral keratin cover in theropods. Non-theropod dinosaurs evolved continuous toothrows despite evolving rostral keratin covers (e.g. some ornithischians and sauropodomorphs). We also show that rostral keratin covers did not significantly increase the evolutionary rate of tooth loss, which further delineates the antagonistic relationship between these structures. Our results suggest that the evolution of rostral keratin had a limited effect on suppressing tooth development. Independent changes in jaw development may have facilitated further tooth loss. Furthermore, the evolution of strong chemical digestion, a gizzard, and a dietary shift to omnivory or herbivory likely alleviated selective pressures for tooth development.


Assuntos
Dinossauros , Perda de Dente , Dente , Animais , Filogenia , Evolução Biológica , Dinossauros/anatomia & histologia , Queratinas , Fósseis , Dente/anatomia & histologia
19.
Sci Rep ; 13(1): 22124, 2024 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-38212342

RESUMO

Tyrannosaurid dinosaurs dominated as predators in the Late Cretaceous of Laurasia, culminating in the evolution of the giant Tyrannosaurus rex, both the last and largest tyrannosaurid. Where and when Tyrannosaurini (T. rex and kin) originated remains unclear. Competing hypotheses place tyrannosaurin origins in Asia, or western North America (Laramidia). We report a new tyrannosaurin, Tyrannosaurus mcraeensis, from the Campanian-Maastrichtian Hall Lake Formation of New Mexico, based on a fossil previously referred to T. rex. T. mcraeensis predates T. rex by ~ 6-7 million years, yet rivaled it in size. Phylogenetic analysis recovers T. mcraeensis as sister to T. rex and suggests Tyrannosaurini originated in southern Laramidia. Evolution of giant tyrannosaurs in southern North America, alongside giant ceratopsians, hadrosaurs, and titanosaurs suggests large-bodied dinosaurs evolved at low latitudes in North America.


Assuntos
Dinossauros , Gigantismo , Animais , Filogenia , Fósseis , América do Norte , New Mexico , Dinossauros/anatomia & histologia , Evolução Biológica
20.
PLoS One ; 19(1): e0292318, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38271406

RESUMO

The Upper Cretaceous (Campanian) Belly River Group (BRG) of southern Alberta has a complex internal stratigraphic architecture derived from differential geometries of its component formations that resulted from regionalized tectonic influences and shifting source areas. A full understanding of BRG architecture has been compromised heretofore by a limited understanding of subsurface data in southwestern- and southeastern-most Alberta. In this study outcrop exposures throughout southern Alberta are tied to reference well logs and subsurface cross-sections allowing a more precise understanding of BRG architecture and how it relates to well-known vertebrate fossil producing areas. Modifications to an existing stratigraphic model of the BRG show that the Oldman and the Dinosaur Park formations have reciprocal north-to-south wedge-shaped geometries and a diachronous contact that become prominently expressed south of Twp 12. The updated model also demonstrates that the Oldman Formation thickens stratigraphically up-section to the south, and that the Foremost-Oldman contact is, essentially, a datum across much of southern Alberta. Identification of the Oldman Formation in the subsurface remains based on its relatively high gamma-ray response in mudstone successions, but it is also recognized that many of its sandstones exhibit relatively low gamma-ray responses like those in underlying and overlying formations. Nomenclature and subdivisions of the Oldman Formation are revised to accommodate this updated understanding, and modifications are also made to the definition of the Judith River-Belly River discontinuity, a newly recognized surface that marks the onset of accommodation and eustatic rise in sea-level in the northern Western Interior Basin at ~76.3 Ma.


Assuntos
Dinossauros , Animais , Alberta , Dinossauros/anatomia & histologia , Rios , Fósseis
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