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1.
PLoS Biol ; 19(8): e3001108, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34375335

RESUMO

Sharks (Selachimorpha) are iconic marine predators that have survived multiple mass extinctions over geologic time. Their prolific fossil record is represented mainly by isolated shed teeth, which provide the basis for reconstructing deep time diversity changes affecting different selachimorph clades. By contrast, corresponding shifts in shark ecology, as measured through morphological disparity, have received comparatively limited analytical attention. Here, we use a geometric morphometric approach to comprehensively examine tooth morphologies in multiple shark lineages traversing the catastrophic end-Cretaceous mass extinction-this event terminated the Mesozoic Era 66 million years ago. Our results show that selachimorphs maintained virtually static levels of dental disparity in most of their constituent clades across the Cretaceous-Paleogene interval. Nevertheless, selective extinctions did impact apex predator species characterized by triangular blade-like teeth. This is particularly evident among lamniforms, which included the dominant Cretaceous anacoracids. Conversely, other groups, such as carcharhiniforms and orectolobiforms, experienced disparity modifications, while heterodontiforms, hexanchiforms, squaliforms, squatiniforms, and †synechodontiforms were not overtly affected. Finally, while some lamniform lineages disappeared, others underwent postextinction disparity increases, especially odontaspidids, which are typified by narrow-cusped teeth adapted for feeding on fishes. Notably, this increase coincides with the early Paleogene radiation of teleosts as a possible prey source, and the geographic relocation of disparity sampling "hotspots," perhaps indicating a regionally disjunct extinction recovery. Ultimately, our study reveals a complex morphological response to the end-Cretaceous mass extinction and highlights an event that influenced the evolution of modern sharks.


Assuntos
Evolução Biológica , Extinção Biológica , Fósseis/anatomia & histologia , Tubarões/anatomia & histologia , Dente/anatomia & histologia , Animais , Ecossistema
3.
J Hum Evol ; 158: 103046, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34332420

RESUMO

Accentuated lines in dental microstructure are hypothesized to correlate with potentially stressful life history events, but our understanding of when, how and why such accentuated lines form in relation to stressful events is limited. We examined accentuated line formation and life history events in the teeth of three naturally deceased mandrills (Mandrillus sphinx, Cercopithecidae), for whom we had detailed life history information. We determined the ages at formation of accentuated lines in histological tooth sections and used dates of birth and death to calibrate dental histology to calendar time and individual age. We found accentuated lines that matched their mother's resumption of sexual cycles in two individuals, and possibly in the third individual. The subjects also formed lines when their mothers were mate-guarded by males or wounded. Accentuated lines matched the birth of the next sibling in one of two cases. Both females formed accentuated lines when they experienced their own sexual swelling cycles, but lines did not match all sexual swelling cycles. Mate-guarding matched an accentuated line in one case, but not in another. Lines matched all three parturitions in the two females. Changes in alpha male and captures did not consistently coincide with accentuated line formation, but repeated captures were associated with lines. Using simulated data, we show that the observed number of matches between lines and events would be very unlikely under a null hypothesis of random line formation. Our results support the hypothesis that some life history events are physiologically stressful enough to cause accentuated line formation in teeth. They contribute to our understanding of how primate life histories are recorded during dental development and enhance our ability to use teeth to reconstruct life history in the absence of direct observation.


Assuntos
Mandrillus , Dente/anatomia & histologia , Animais , Feminino , Gabão , Masculino , Mandrillus/fisiologia , Paleodontologia , Reprodução
4.
Am J Phys Anthropol ; 176(2): 262-282, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34190335

RESUMO

OBJECTIVES: Size-corrected tooth crown measurements were used to estimate phenetic affinities among Homo naledi (~335-236 ka) and 11 other Plio-Pleistocene and recent species. To assess further their efficacy, and identify dental evolutionary trends, the data were then quantitatively coded for phylogenetic analyses. Results from both methods contribute additional characterization of H. naledi relative to other hominins. MATERIALS AND METHODS: After division by their geometric mean, scaled mesiodistal and buccolingual dimensions were used in tooth size apportionment analysis to compare H. naledi with Australopithecus africanus, A. afarensis, Paranthropus robustus, P. boisei, H. habilis, H. ergaster, H. erectus, H. heidelbergensis, H. neanderthalensis, H. sapiens, and Pan troglodytes. These data produce equivalently scaled samples unaffected by interspecific size differences. The data were then gap-weighted for Bayesian inference. RESULTS: Congruence in interspecific relationships is evident between methods, and with many inferred from earlier systematic studies. However, the present results place H. naledi as a sister taxon to H. habilis, based on a symplesiomorphic pattern of relative tooth size. In the preferred Bayesian phylogram, H. naledi is nested within a clade comprising all Homo species, but it shares some characteristics with australopiths and, particularly, early Homo. DISCUSSION: Phylogenetic analyses of relative tooth size yield information about evolutionary dental trends not previously reported in H. naledi and the other hominins. Moreover, with an appropriate model these data recovered plausible evolutionary relationships. Together, the findings support recent study suggesting H. naledi originated long before the geological date of the Dinaledi Chamber, from which the specimens under study were recovered.


Assuntos
Hominidae/anatomia & histologia , Hominidae/classificação , Dente/anatomia & histologia , Animais , Antropologia Física , Teorema de Bayes , Evolução Biológica , Fósseis , Humanos , Filogenia , Coroa do Dente/anatomia & histologia
5.
Science ; 372(6546): 1105-1107, 2021 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-34083491

RESUMO

Shark populations have been decimated in recent decades because of overfishing and other anthropogenic stressors; however, the long-term impacts of such changes in marine predator abundance and diversity are poorly constrained. We present evidence for a previously unknown major extinction event in sharks that occurred in the early Miocene, ~19 million years ago. During this interval, sharks virtually disappeared from open-ocean sediments, declining in abundance by >90% and morphological diversity by >70%, an event from which they never recovered. This abrupt extinction occurred independently from any known global climate event and ~2 million to 5 million years before diversifications in the highly migratory, large-bodied predators that dominate pelagic ecosystems today, indicating that the early Miocene was a period of rapid, transformative change for open-ocean ecosystems.


Assuntos
Ecossistema , Extinção Biológica , Tubarões , Animais , Peixes , Fósseis , Sedimentos Geológicos , Oceanos e Mares , Paleodontologia , Dente/anatomia & histologia
6.
Am J Phys Anthropol ; 176(2): 192-207, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34115384

RESUMO

OBJECTIVE: The Southeast and South Coast of Brazil was inhabited during most of the Holocene by shellmound builders. Although there are cultural differences in the archaeological record between regions, it is still debatable how these differences may relate to different population histories. Here, we contribute to this discussion by exploring dental morphological affinities between several regional series. MATERIALS AND METHODS: Dental morphology of 385 individuals from 14 archaeological sites was analyzed using the Arizona State University Dental Anthropology System. Fifteen traits were used to explore morphological affinities among series through Euclidean distance, Mean Measure of Divergence, and Principal Component Analysis. Mantel matrix correlation and partial correlation tests were used to examine the association between biological, geographic, and chronological distances. RESULTS: Morphological affinities show that ceramic and nonceramic South Coast groups cluster and differ from most Southeast series. In contrast, Southeast coastal and riverine groups display high morphological variance, showing less biological coherence among them. These biological distances between regions are partially explained by geography, but not by chronology. CONCLUSIONS: The results support that these coastal populations were low-mobility groups. Although interactions between individuals of different regions likely existed, gene flow occurred mostly among individuals from local or adjacent areas. The introduction of ceramic in the South Coast is not associated with changes in dental morphology patterns, suggesting its adoption is not exclusively associated with the arrival of different biological groups. Southeast coastal and riverine groups show high phenotypic diversity, suggesting a different history of human occupation and cultural development than observed in the South Coast.


Assuntos
Evolução Biológica , Índios Sul-Americanos/história , Dente/anatomia & histologia , Antropologia Física , Arqueologia , Brasil , História Antiga , Humanos
7.
Am J Phys Anthropol ; 176(1): 144-151, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34117635

RESUMO

OBJECTIVES: The statistical analysis of fossil remains is essential to understand the evolution of the genus Homo. Unfortunately, the human fossil record is straight away scarce and plagued with severe loss of information caused by taphonomic processes. The recently developed field of Virtual Anthropology helps to ameliorate this situation by using digital techniques to restore damaged and incomplete fossils. MATERIALS AND METHODS: We present the package Arothron, an R software suite meant to process and analyze digital models of skeletal elements. Arothron includes tools to digitally extract virtual cavities such as cranial endocasts, to statistically align disarticulated or broken bony elements, and to visualize local variations between surface meshes and landmark configurations. RESULTS: We describe the main functionalities of Arothron and illustrate their usage through reproducible case studies. We describe a tool for segmentation of skeletal cavities by showing its application on a malleus bone, a Neanderthal tooth, and a modern human cranium, reproducing their shape and calculating their volume. We illustrate how to digitally align a disarticulated model of a modern human cranium, and how to combine piecemeal shape information on individual specimens into one. In addition, we present useful visualization tools by comparing the morphological differences between the right hemisphere of the Neanderthal and the modern human brain. CONCLUSIONS: The Arothron R package is designed to study digital models of fossil specimens. By using Arothron, scientists can handle digital models with ease, investigate the inner morphology of 3D skeletal models, gain a full representation of the original shapes of damaged specimens, and compare shapes across specimens.


Assuntos
Antropometria/métodos , Osso e Ossos/anatomia & histologia , Fósseis/anatomia & histologia , Imageamento Tridimensional/métodos , Software , Animais , Antropologia Física , Osso e Ossos/diagnóstico por imagem , Feminino , Fósseis/diagnóstico por imagem , Humanos , Masculino , Homem de Neandertal , Dente/anatomia & histologia , Dente/diagnóstico por imagem
8.
Elife ; 102021 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-34060471

RESUMO

Teeth are present in most clades of vertebrates but have been lost completely several times in actinopterygian fishes and amniotes. Using phenotypic data collected from over 500 genera via micro-computed tomography, we provide the first rigorous assessment of the evolutionary history of dentition across all major lineages of amphibians. We demonstrate that dentition is invariably present in caecilians and salamanders, but teeth have been lost completely more than 20 times in frogs, a much higher occurrence of edentulism than in any other vertebrate group. The repeated loss of teeth in anurans is associated with a specialized diet of small invertebrate prey as well as shortening of the lower jaw, but it is not correlated with a reduction in body size. Frogs provide an unparalleled opportunity for investigating the molecular and developmental mechanisms of convergent tooth loss on a large phylogenetic scale.


Assuntos
Anuros/fisiologia , Evolução Biológica , Arcada Osseodentária/fisiologia , Dente/fisiologia , Adaptação Fisiológica , Animais , Anuros/anatomia & histologia , Dieta , Arcada Osseodentária/anatomia & histologia , Arcada Osseodentária/diagnóstico por imagem , Filogenia , Fatores de Tempo , Dente/anatomia & histologia , Dente/diagnóstico por imagem , Microtomografia por Raio-X
9.
Sci Rep ; 11(1): 12877, 2021 06 18.
Artigo em Inglês | MEDLINE | ID: mdl-34145353

RESUMO

Corrosion patterns induced by gastric fluids on the skeleton of prey animals may depend on the nature of the corrosive agents (acid, enzymes) as well as on the composition of the hard parts and the soft tissues that surround them. We propose a framework for predicting and interpreting corrosion patterns on lizard teeth, our model system, drawing on the different digestive pathways of avian and non-avian vertebrate predators. We propose that high-acid, low-enzyme systems (embodied by mammalian carnivores) will lead to corrosion of the tooth crowns, whereas low-acid, high-enzyme systems (embodied by owls) will lead to corrosion of the tooth shafts. We test our model experimentally using artificial gastric fluids (with HCl and pepsin) and feeding experiments, and phenomenologically using wild-collected owl pellets with lizard remains. Finding an association between the predictions and the experimental results, we then examine corrosion patterns on nearly 900 fossil lizard jaws. Given an appropriate phylogenetic background, our focus on physiological rather than taxonomic classes of predators allows the extension of the approach into Deep Time.


Assuntos
Cárie Dentária/patologia , Fósseis , Lagartos , Dente/patologia , Ração Animal , Animais , Digestão , Modelos Animais de Doenças , Furões , Paleontologia , Dente/anatomia & histologia
10.
Sci Rep ; 11(1): 10209, 2021 05 13.
Artigo em Inglês | MEDLINE | ID: mdl-33986378

RESUMO

Competition for resources is a key question in the study of our early human evolution. From the first hominin groups, carnivores have played a fundamental role in the ecosystem. From this perspective, understanding the trophic pressure between hominins and carnivores can provide valuable insights into the context in which humans survived, interacted with their surroundings, and consequently evolved. While numerous techniques already exist for the detection of carnivore activity in archaeological and palaeontological sites, many of these techniques present important limitations. The present study builds on a number of advanced data science techniques to confront these issues, defining methods for the identification of the precise agents involved in carcass consumption and manipulation. For the purpose of this study, a large sample of 620 carnivore tooth pits is presented, including samples from bears, hyenas, jaguars, leopards, lions, wolves, foxes and African wild dogs. Using 3D modelling, geometric morphometrics, robust data modelling, and artificial intelligence algorithms, the present study obtains between 88 and 98% accuracy, with balanced overall evaluation metrics across all datasets. From this perspective, and when combined with other sources of taphonomic evidence, these results show that advanced data science techniques can be considered a valuable addition to the taphonomist's toolkit for the identification of precise carnivore agents via tooth pit morphology.


Assuntos
Ciência de Dados/métodos , Paleontologia/métodos , Dente/anatomia & histologia , Animais , Arqueologia/métodos , Inteligência Artificial , Osso e Ossos/anatomia & histologia , Carnívoros , Biologia Computacional/métodos , Fósseis , Hominidae , Humanos , Modelos Estatísticos
11.
J Anat ; 239(3): 704-719, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-33895988

RESUMO

Among the cartilaginous fishes (Chondrichthyes), the Holocephali are unique in that teeth are absent both in ontogeny and adult regenerative growth. Instead, the holocephalan dentition of ever-growing nonshedding dental plates is composed of dentine, trabecular in arrangement, forming spaces into which a novel hypermineralized dentine (whitlockin) is deposited. These tissue features form a variety of specific morphologies as the defining characters of dental plates in the three families of extant holocephalans. We demonstrate how this morphology changes through ontogenetic development with continuity between morphologies, through successive growth stages of the dentition represented by the dental plate. For example, rod-shaped whitlockin appears early, later transformed into the tritoral pad, including a regular arrangement of vascular canals and whitlockin forming with increasing mineralization (95%-98%). While the tritoral pads develop lingually, stacks of individual ovoids of whitlockin replace the rods in the more labial parts of the plate, again shaped by the forming trabecular dentine. The ability to make dentine into new, distinctive patterns is retained in the evolution of the Holocephali, despite the lack of teeth forming in development of the dentition. We propose that developmentally, odontogenic stem cells, retained through evolution, control the trabecular dentine formation within the dental plate, and transition to form whitlockin, throughout lifetime growth. Our model of cellular activity proposes a tight membrane of odontoblasts, having transformed to whitloblasts, that can control active influx of minerals to the rapidly mineralizing dentine, forming whitlockin. After the reduced whitloblast cells transition back to odontoblasts, they continue to monitor the levels of minerals (calcium, phosphate and magnesium) and at a slower rate of growth in the peritubate 'softer' dentine. This model explains the unique features of transitions within the holocephalan dental plate morphology.


Assuntos
Dentina/anatomia & histologia , Peixes/anatomia & histologia , Dente/anatomia & histologia , Animais , Dentina/fisiologia , Dentição , Peixes/fisiologia , Odontogênese/fisiologia
12.
J Hum Evol ; 154: 102942, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33838563

RESUMO

The early hominin record is characterized by numerous shifts in dental proportions (e.g., canine reduction and megadontia) linked to changes in diet and social behavior. Recent studies suggest that hominins exhibit a reduction in the magnitude of covariation between the anterior and posterior dental components compared with other extant great apes. They point toward, but do not directly test, the relative independence of canine morphology within the hominin alveolar arch. This study focuses specifically on the how the canine region covaries with other regions of the dental arch because the canine region has drastically reduced in size and changed in shape across human evolution. We examine extant primate species most commonly used as a comparative framework for fossil hominin morphology: Gorilla gorilla (n = 27), Pan troglodytes (n = 27), and Homo sapiens (n = 30). We used geometric morphometric methods to test for size and shape covariation between the canine region with other dental regions. We also examined the influence of sexual dimorphism and allometry on intraspecific and interspecific patterns of covariation. The analysis of size and shape covariation between the mandibular canine and other individual tooth regions elucidated complex, species-specific, and sex-specific morphological relationships in the mandibular alveolar arch. There was little evidence to support different patterns of morphological integration between humans on the one hand and nonhuman apes on the other. Canine region morphology was relatively independent from other dental regions across species based on shape and did not significantly covary more with either the incisor or postcanine region in any species. The size correlations between the canine and other dental regions were moderate to high. The species-specific results of this study question the ability to make a priori assumptions about morphological integration in the extant hominin mandibular alveolar arch and its application to the fossil record.


Assuntos
Processo Alveolar/anatomia & histologia , Evolução Biológica , Fósseis , Hominidae/anatomia & histologia , Dente/anatomia & histologia , Animais , Feminino , Gorilla gorilla/anatomia & histologia , Masculino , Mandíbula/anatomia & histologia , Pan troglodytes/anatomia & histologia , Caracteres Sexuais , Especificidade da Espécie
13.
Sci Rep ; 11(1): 7594, 2021 04 07.
Artigo em Inglês | MEDLINE | ID: mdl-33828193

RESUMO

In the last decades, several discoveries have uncovered the complexity of mammalian evolution during the Mesozoic Era, including important Gondwanan lineages: the australosphenidans, gondwanatherians, and meridiolestidans (Dryolestoidea). Most often, their presence and diversity is documented by isolated teeth and jaws. Here, we describe a new meridiolestidan mammal, Orretherium tzen gen. et sp. nov., from the Late Cretaceous of southern Chile, based on a partial jaw with five cheek teeth in locis and an isolated upper premolar. Phylogenetic analysis places Orretherium as the earliest divergence within Mesungulatidae, before other forms such as the Late Cretaceous Mesungulatum and Coloniatherium, and the early Paleocene Peligrotherium. The in loco tooth sequence (last two premolars and three molars) is the first recovered for a Cretaceous taxon in this family and suggests that reconstructed tooth sequences for other Mesozoic mesungulatids may include more than one species. Tooth eruption and replacement show that molar eruption in mesungulatids is heterochronically delayed with regard to basal dryolestoids, with therian-like simultaneous eruption of the last premolar and last molar. Meridiolestidans seem endemic to Patagonia, but given their diversity and abundance, and the similarity of vertebrate faunas in other regions of Gondwana, they may yet be discovered in other continents.


Assuntos
Arcada Osseodentária/anatomia & histologia , Mamíferos/classificação , Dente/anatomia & histologia , Animais , Dente Pré-Molar/anatomia & histologia , Evolução Biológica , Osso e Ossos/anatomia & histologia , Chile , Fósseis/história , História Antiga , Dente Molar/anatomia & histologia , Filogenia , Crânio/anatomia & histologia , Anormalidades Dentárias/classificação , Erupção Dentária/fisiologia
14.
Evolution ; 75(6): 1377-1394, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33904594

RESUMO

Venomous snakes are among the world's most specialized predators. During feeding, they use fangs to penetrate the body tissues of their prey, but the success of this penetration depends on the shape of these highly specialized teeth. Here, we examined the evolution of fang shape in a wide range of snakes using 3D geometric morphometrics (3DGM) and cross-sectional tooth sharpness measurements. We investigated the relationship of these variables with six diet categories based on the prey's biomechanical properties, and tested for evolutionary convergence using two methods. Our results show that slender elongate fangs with sharp tips are used by snakes that target soft-skinned prey (e.g., mammals), whereas fangs become more robust and blunter as the target's skin becomes scaly (e.g., fish and reptiles) and eventually hard-shelled (e.g., crustaceans), both with and without correction for evolutionary allometry. Convergence in fang shape is present, indicating that fangs of snakes with the same diet are more similar than those of closely related species with different diets. Establishing the relationship between fang morphology and diet helps to explain how snakes became adapted to different lifestyles, while also providing a proxy to infer diet in lesser known species or extinct snakes from the fossil record.


Assuntos
Adaptação Fisiológica , Comportamento Predatório , Serpentes/anatomia & histologia , Dente/anatomia & histologia , Animais , Fenômenos Biomecânicos , Dieta/veterinária , Serpentes/genética
15.
J Anat ; 239(2): 405-423, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33721329

RESUMO

Rodents are the most diverse order of extant mammals, and caviomorph rodents, or New World hystricognaths, have a remarkable morphological disparity and a long fossil record that begins in the Eocene. Chinchilloidea is a poorly understood clade within Caviomorpha, from an evolutionary and phylogenetic perspective. It includes the extant families Chinchillidae and Dinomyidae, the extinct Neoepiblemidae and Cephalomyidae, and several extinct chinchilloids without a clear phylogenetic position, like Eoincamys, Borikenomys, Chambiramys, Ucayalimys, Incamys, Saremmys, Garridomys and Scotamys. The family Chinchillidae includes the extant Chinchilla and Lagidium, grouped in Chinchillinae, and the only living Lagostominae, Lagostomus maximus. Among extinct chinchillids, Eoviscaccia (early Oligocene-early Miocene of Argentina, Bolivia and Chile), Prolagostomus (early-middle Miocene of Argentina, Bolivia and Chile) and Pliolagostomus (early-middle Miocene of Argentina) are the only genera originally described as members of the family. Based on the study of specimens with unworn or little-worn cheek teeth, belonging to extinct and extant taxa, we propose homologies of the cheek teeth structures and perform a combined molecular and morphological phylogenetic analysis including extinct and extant taxa of all families of Chinchilloidea and all genera of Chinchillidae. Our phylogenetic analysis recovered three major lineages in the evolutionary history of Chinchilloidea. The first major lineage is composed of the extant taxa Chinchilla, Lagidium and Lagostomus, and the extinct genera Eoviscaccia, Prolagostomus, Pliolagostomus, Garridomys, Incamys, Loncolicu and Saremmys. Cephalomyid (Banderomys, Cephalomys, Litodontomys, Soriamys) and neoepiblemid (Neoepiblema, Perimys, Phoberomys, Scotamys) genera are part of the second major lineage, while dinomyids such as Dinomys, Drytomomys, Scleromys, 'Scleromys' and Tetrastylus constitute the third major lineage within Chinchilloidea. The phylogenetic position of some taxa previously considered as incertae sedis chinchilloids or without a clear suprageneric group (i.e. Incamys, Saremmys, Garridomys and Loncolicu) show that they belong to pan-Chinchillidae and conform the stem Chinchillidae along with Eoviscaccia. The euhypsodont crown Chinchillidae includes the living subfamilies Chinchillinae and Lagostominae. Dinomyidae and Eoincamys pascuali are recovered as the sisters of a major clade composed by 'Cephalomyidae'+Neopiblemidae and pan-Chinchillidae, and Chambiramys sylvaticus occupies a basal position to the same clade. Four major radiation events are identified in the evolutionary history of Chinchilloidea. The analysis of new morphological characters linked with molecular evidence as well as the addition of taxa of uncertain or unstable phylogenetic position or not considered in previous studies allowed us resolve part of the relationships within Chinchilloidea, particularly that of Chinchillidae, supporting preceding morphological hypotheses.


Assuntos
Evolução Biológica , Chinchila/anatomia & histologia , Filogenia , Dente/anatomia & histologia , Animais , Chinchila/genética
16.
Science ; 371(6535): 1253-1256, 2021 03 19.
Artigo em Inglês | MEDLINE | ID: mdl-33737486

RESUMO

The ecomorphological diversity of extinct elasmobranchs is incompletely known. Here, we describe Aquilolamna milarcae, a bizarre probable planktivorous shark from early Late Cretaceous open marine deposits in Mexico. Aquilolamna, tentatively assigned to Lamniformes, is characterized by hypertrophied, slender pectoral fins. This previously unknown body plan represents an unexpected evolutionary experimentation with underwater flight among sharks, more than 30 million years before the rise of manta and devil rays (Mobulidae), and shows that winglike pectoral fins have evolved independently in two distantly related clades of filter-feeding elasmobranchs. This newly described group of highly specialized long-winged sharks (Aquilolamnidae) displays an aquilopelagic-like ecomorphotype and may have occupied, in late Mesozoic seas, the ecological niche filled by mobulids and other batoids after the Cretaceous-Paleogene boundary.


Assuntos
Evolução Biológica , Fósseis , Tubarões/anatomia & histologia , Tubarões/fisiologia , Nadadeiras de Animais/anatomia & histologia , Animais , Ecossistema , Elasmobrânquios/anatomia & histologia , Elasmobrânquios/fisiologia , Comportamento Alimentar , México , Oceanos e Mares , Paleodontologia , Plâncton , Tubarões/classificação , Natação , Dente/anatomia & histologia
17.
Proc Biol Sci ; 288(1946): 20203173, 2021 03 10.
Artigo em Inglês | MEDLINE | ID: mdl-33653134

RESUMO

One molluscan autapomorphy is the radula, the organ used for feeding. Here, for the first time, the performance and failure of taenioglossan radular teeth were tested in a biomechanical experiment which in turn allowed building hypotheses about tooth functionalities. Shear load was applied to tooth cusps with a force transducer until structural failure occurred, the broken area was measured, and finally breaking stress was calculated. These experiments were carried out under dry and wet conditions. Our results show that certain tooth types can resist higher stresses and are rather specialised to loosen food items from a surface, whereas other teeth can only gather food particles. The experiments additionally illustrate the high influence of the water content on the resulting breaking stress. When wet teeth were tested, their ductility and ability to avoid being fractured by an obstacle increased. Their flexibility also allowed them support from teeth of adjacent tooth rows, which made the whole system less prone to failure. Our results were compared with the previous data on the mechanical properties and feeding simulations. This study provides a keystone for further comparative studies aiming at connecting diversity of radulae with their possible adaptations to the ingesta.


Assuntos
Gastrópodes , Dente , Animais , Fenômenos Biomecânicos , Comportamento Alimentar , Estresse Mecânico , Dente/anatomia & histologia , Água
18.
Am J Phys Anthropol ; 175(2): 497-505, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33704773

RESUMO

OBJECTIVES: While genetic studies have documented variation in admixture proportions in contemporary African Americans across the US, relatively little is known about the socio-historical roots of this variation. Our goal in this study is to use dental morphology to explore the socio-historical correlates of admixture, localized gene flow, and drift in African Americans. METHODS: Our data are ordinally-graded dental morphological traits scored in 196 Africans, 335 Europeans and European Americans, 291 pre-Spanish-contact Native Americans, and 722 African Americans. The African American data derived from contemporary and historic samples. We eliminated from analysis individuals and traits with greater than 20% missing data. We summarized the major axes of trait variation using principal component analysis (PCA), estimated biological distance, constructed multidimensional scaling (MDS) plots of the distances, and measured the correlation between geographic and biological distance. RESULTS: In the PCA, African American groups clustered between Africans and Europeans on PC 1, reflecting admixture between the groups. PC 2 separated African American samples, possibly reflecting movement, isolation, and drift. MDS analyses confirmed the existence of sizable biological distances between African American samples, especially between contemporary and past African American samples. We found no relationship between biological and geographic distances. DISCUSSION: We demonstrate that admixture and drift can be inferred from multi-variable analyses of patterns of dental morphology in admixed populations. Localized gene flow has not affected patterns of trait variation in African Americans, but long-range movement, isolation, and drift have. We connect patterns of dental trait variation to efforts to flee oppression during the Great Migration, and the repeal of anti-miscegenation laws.


Assuntos
Afro-Americanos , Fluxo Gênico/genética , Genética Populacional , Dente/anatomia & histologia , Afro-Americanos/genética , Afro-Americanos/estatística & dados numéricos , Grupo com Ancestrais do Continente Africano/genética , Grupo com Ancestrais do Continente Africano/estatística & dados numéricos , Antropologia Física , Grupo com Ancestrais do Continente Europeu/genética , Grupo com Ancestrais do Continente Europeu/estatística & dados numéricos , Humanos
19.
PLoS One ; 16(3): e0248163, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33730093

RESUMO

Isolated stegosaurian teeth from the Early Cretaceous high-latitude (palaeolatitude estimate of N 62°- 66.5°) Teete locality in Yakutia (Eastern Siberia, Russia) are characterized by a labiolingually compressed, slightly asymmetrical and mesiodistally denticulated (9-14 denticles) crown, a pronounced ring-like cingulum, as well as a "complex network of secondary ridges". The 63 teeth (found during on-site excavation in 2012, 2017-2019 and screen-washing in 2017-2019) most likely belong to one species of a derived (stegosaurine) stegosaur. Most of the teeth exhibit a high degree of wear and up to three wear facets has been observed on a single tooth. The prevalence of worn teeth with up to three wear facets and the presence of different types of facets (including steeply inclined and groove-like) indicate the tooth-tooth contact and precise dental occlusion in the Teete stegosaur. The microwear pattern (mesiodistally or slightly obliquely oriented scratches; differently oriented straight and curved scratches on some wear facets) suggest a complex jaw mechanism with palinal jaw motion. Histological analysis revealed that the Teete stegosaur is characterized by relatively short tooth formation time (95 days) and the presence of a "wavy enamel pattern". Discoveries of a "wavy enamel pattern" in the Teete stegosaur, in a Middle Jurassic stegosaur from Western Siberia, and in the basal ceratopsian Psittacosaurus, suggest that this histological feature is common for different ornithischian clades, including ornithopods, marginocephalians, and thyreophorans. A juvenile tooth in the Teete sample indicates that stegosaurs were year-round residents and reproduced in high latitudes. The combination of high degree of tooth wear with formation of multiple wear facets, complex jaw motions, relatively short tooth formation time and possibly high tooth replacement rates is interpreted as a special adaptation for a life in high-latitude conditions or, alternatively, as a common stegosaurian adaptation making stegosaurs a successful group of herbivorous dinosaurs in the Middle Jurassic-Early Cretaceous and enabeling them to live in both low- and high-latitude ecosystems.


Assuntos
Dentição , Dinossauros/anatomia & histologia , Dente/anatomia & histologia , Animais , Ecossistema , Fósseis , Federação Russa , Desgaste dos Dentes
20.
J Hum Evol ; 153: 102956, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33711722

RESUMO

Fossiliferous deposits at Woranso-Mille span the period when Australopithecus anamensis gave rise to Australopithecus afarensis (3.8-3.6 Ma) and encompass the core of the A. afarensis range (ca. 3.5-3.2 Ma). Within the latter period, fossils described to date include the intriguing but taxonomically unattributed Burtele foot, dentognathic fossils attributed to Australopithecus deyiremeda, and one specimen securely attributed to A. afarensis (the Nefuraytu mandible). These fossils suggest that at least one additional hominin lineage lived alongside A. afarensis in the Afar Depression. Here we describe a collection of hominin fossils from a new locality in the Leado Dido'a area of Woranso-Mille (LDD-VP-1). The strata in this area are correlated to the same chron as those in the Burtele area (C2An.3n; 3.59-3.33 Ma), and similar in age to the Maka Sands and the Basal through lower Sidi Hakoma Members of the Hadar Formation. We attribute all but one of the LDD hominin specimens to A. afarensis, based on diagnostic morphology of the mandible, maxilla, canines, and premolars. The LDD specimens generally fall within the range of variation previously documented for A. afarensis but increase the frequency of some rare morphological variants. However, one isolated M3 is extremely small, and its taxonomic affinity is currently unknown. The new observations support previous work on temporal trends in A. afarensis and demonstrate that the large range of variation accepted for this species is present even within a limited spatiotemporal range. The value added with this sample lies in its contribution to controlling for spatiotemporal differences among site samples in the A. afarensis hypodigm and its contemporaneity with non-A. afarensis specimens at Woranso-Mille.


Assuntos
Fósseis , Hominidae , Animais , Etiópia , Hominidae/anatomia & histologia , Mandíbula/anatomia & histologia , Maxila/anatomia & histologia , Dente/anatomia & histologia
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