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1.
Anat Rec (Hoboken) ; 2024 Feb 29.
Artigo em Inglês | MEDLINE | ID: mdl-38421128

RESUMO

The osteology, neuroanatomy, and musculature are known for most primary clades of turtles (i.e., "families"), but knowledge is still lacking for one particular clade, the Carettochelyidae. Carettochelyids are represented by only one living taxon, the pig-nosed turtle Carettochelys insculpta. Here, we use micro-computed tomography of osteological and contrast-enhanced stained specimens to describe the cranial osteology, neuroanatomy, circulatory system, and jaw musculature of Carettochelys insculpta. The jaw-related myology is described in detail for the first time for this taxon, including m. zygomaticomandibularis, a muscular unit only found in trionychians. We also document a unique arterial pattern for the internal carotid artery and its subordinate branches and provide an extensive list of osteological ontogenetic differences. The present work provides new insights into the craniomandibular anatomy of turtles and will allow a better understanding of the evolutionary history of the circulatory system of trionychians and intraspecific variation among turtles.

2.
Swiss J Palaeontol ; 143(1): 4, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38328031

RESUMO

Placodonts were durophagous reptiles of the Triassic seas with robust skulls, jaws, and enlarged, flat, pebble-like teeth. During their evolution, they underwent gradual craniodental changes from the Early Anisian to the Rhaetian, such as a reduction in the number of teeth, an increase in the size of the posterior palatal teeth, an elongation of the premaxilla/rostrum, and a widening of the temporal region. These changes are presumably related to changes in dietary habits, which, we hypothesise, are due to changes in the type and quality of food they consumed. In the present study, the dental wear pattern of a total of nine European Middle to Late Triassic placodont species were investigated using 2D and 3D microwear analyses to demonstrate whether there could have been a dietary shift or grouping among the different species and, whether the possible changes could be correlated with environmental changes affecting their habitats. The 3D analysis shows overlap between species with high variance between values and there is no distinct separation. The 2D analysis has distinguished two main groups. The first is characterised by low number of wear features and high percentage of large pits. The other group have a high feature number, but low percentage of small pits. The 2D analysis showed a correlation between the wear data and the size of the enlarged posterior crushing teeth. Teeth with larger sizes showed less wear feature (with higher pit ratio) but larger individual features. In contrast, the dental wear facet of smaller crushing teeth shows more but smaller wear features (with higher scratch number). This observation may be related to the size of the food consumed, i.e., the wider the crown, the larger food it could crush, producing larger features. Comparison with marine mammals suggests that the dietary preference of Placochelys, Psephoderma and Paraplacodus was not exclusively hard, thick-shelled food. They may have had a more mixed diet, similar to that of modern sea otters. The diet of Henodus may have included plant food, similar to the modern herbivore marine mammals and lizards. Supplementary Information: The online version contains supplementary material available at 10.1186/s13358-024-00304-x.

3.
Nat Ecol Evol ; 8(3): 536-551, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38200368

RESUMO

The arrangement and morphology of the vertebrate skull reflect functional and ecological demands, making it a highly adaptable structure. However, the fundamental developmental and macroevolutionary mechanisms leading to different vertebrate skull phenotypes remain unclear. Here we exploit the morphological diversity of squamate reptiles to assess the developmental and evolutionary patterns of skull variation and covariation in the whole head. Our geometric morphometric analysis of a complex squamate ontogenetic dataset (209 specimens, 169 embryos, 44 species), covering stages from craniofacial primordia to fully ossified bones, reveals that morphological differences between snake and lizard skulls arose gradually through changes in spatial relationships (heterotopy) followed by alterations in developmental timing or rate (heterochrony). Along with dynamic spatiotemporal changes in the integration pattern of skull bone shape and topology with surrounding brain tissues and sensory organs, we identify a relatively higher phenotypic integration of the developing snake head compared with lizards. The eye, nasal cavity and Jacobson's organ are pivotal in skull morphogenesis, highlighting the importance of sensory rearrangements in snake evolution. Furthermore, our findings demonstrate the importance of early embryonic, ontogenetic and tissue interactions in shaping craniofacial evolution and ecological diversification in squamates, with implications for the nature of cranio-cerebral relations across vertebrates.


Assuntos
Cabeça , Crânio , Animais , Crânio/anatomia & histologia , Osteogênese
4.
Anat Rec (Hoboken) ; 307(4): 1559-1593, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38197580

RESUMO

The complex constructions of land vertebrate skulls have inspired a number of functional analyses. In the present study, we provide a basic view on skull biomechanics and offer a framework for more general observations using advanced modeling approaches in the future. We concentrate our discussion on the cranial openings in the temporal skull region and work out two major, feeding-related factors that largely influence the shape of the skull. We argue that (1) the place where the most forceful biting is conducted and (2) the handling of resisting food (sideward movements) constitute the formation and shaping of either one or two temporal arcades surrounding these openings. Diversity in temporal skull anatomy among amniotes can be explained by specific modulations of these factors with different amounts of acting forces which inevitably lead to deposition or reduction of bone material. For example, forceful anterior bite favors an infratemporal bar, whereas forceful posterior bite favors formation of an upper temporal arcade. Transverse forces (inertia and resistance of seized objects) as well as neck posture also influence the shaping of the temporal region. Considering their individual skull morphotypes, we finally provide hypotheses on the feeding adaptation in a variety of major tetrapod groups. We did not consider ligaments, internal bone structure, or cranial kinesis in our considerations. Involving those in quantitative tests of our hypotheses, such as finite element system synthesis, will provide a comprehensive picture on cranial mechanics and evolution in the future.


Assuntos
Dinossauros , Crânio , Animais , Fenômenos Biomecânicos , Crânio/anatomia & histologia , Cabeça/anatomia & histologia , Dinossauros/anatomia & histologia , Força de Mordida , Fósseis
5.
Dev Dyn ; 2023 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-37837337

RESUMO

A previously unknown reference to the Russian ethnologist, biologist, and traveler Nikolai N. Miklucho-Maclay (1846-1888) was discovered in correspondence between Charles Darwin (1809-1882) and Ernst Haeckel (1834-1919). This reference has remained unknown to science, even to Miklucho-Maclay's biographers, probably because Darwin used the Russian nickname "Mikluska" when alluding to this young scientist. Here, we briefly outline the story behind the short discussion between Darwin and his German counterpart Haeckel, and highlight its importance for the history of science. Miklucho-Maclay's discovery of a putative swim bladder anlage in sharks, published in 1867, was discussed in four letters between the great biologists. Whereas, Haeckel showed enthusiasm for the finding because it supported (his view on) evolutionary theory, Darwin was less interested, which highlights the conceptual differences between the two authorities. We discuss the scientific treatment of Miklucho-Maclay's observation in the literature and discuss the homology, origin, and destiny of gas organs-swim bladders and lungs-in vertebrate evolution, from an ontogenetic point of view. We show that the conclusions reached by Miklucho-Maclay and Haeckel were rather exaggerated, although they gave rise to fundamental insights, and we illustrate how tree-thinking may lead to differences in the conceptualization of evolutionary change.

6.
Anat Rec (Hoboken) ; 2023 Apr 12.
Artigo em Inglês | MEDLINE | ID: mdl-37042473

RESUMO

Based on histological cross-sections, the chondrocranium of the common musk turtle (Sternotherus odoratus) was reconstructed, described, and compared with other turtles. It differs from that of other turtle chondrocrania by possessing elongated, slightly dorsally orientated nasal capsules with three dorsolateral foramina, which might be homologous to the foramen epiphaniale, and by having an enlarged crista parotica. Additionally, the posterior part of the palatoquadrate is more elongated and more slender than in other turtles, while its ascending process is connected to the otic capsule by appositional bone. The proportions of the chondrocranium were also compared with those of "mature" chondrocrania of other turtle species in a Principal Component Analysis (PCA). Other than expected, the S. odoratus chondrocranium is not similar in proportions to those of chelydrids, the closest related species in the sample. The results indicate to differences in the proportions among larger turtle clades (e.g., Durocryptodira, Pleurodira, and Trionychia). S. odoratus is an exception to this pattern since it shows elongated nasal capsules similar to the trionychid Pelodiscus sinensis. A second PCA comparing the chondrocranial proportions of multiple developmental "stages" mostly shows differences between trionychids and all other turtles. S. odoratus is again similar to trionychids along PC1, but its proportions are the most similar along PC2 and PC3 to older "stages" of americhelydians, including the chelydrid Chelydra serpentina, which is related to chondrocranium height and quadrate width. We discuss potential ecological correlations of our findings mirrored in late embryonic stages.

7.
Proc Biol Sci ; 290(1990): 20221928, 2023 01 11.
Artigo em Inglês | MEDLINE | ID: mdl-36629110

RESUMO

Bats have undergone one of the most drastic limb innovations in vertebrate history, associated with the evolution of powered flight. Knowledge of the genetic basis of limb organogenesis in bats has increased but little has been documented regarding the differences between limb organogenesis in bats and that of other vertebrates. We conducted embryological comparisons of the timelines of limb organogenesis in 24 bat species and 72 non-bat amniotes. In bats, the time invested for forelimb organogenesis has been considerably extended and the appearance timing of the forelimb ridge has been significantly accelerated, whereas the timing of the finger and first appearance of the claw development has been delayed, facilitating the enlargement of the manus. Furthermore, we discovered that bats initiate the development of their hindlimbs earlier than their forelimbs compared with other placentals. Bat neonates are known to be able to cling continuously with their well-developed foot to the maternal bodies or habitat substrates soon after birth. We suggest that this unique life history of neonates, which possibly coevolved with powered flight, has driven the accelerated development of the hindlimb and precocious foot.


Assuntos
Quirópteros , Animais , Recém-Nascido , Humanos , Vertebrados , Membro Anterior , Organogênese/genética , Membro Posterior , Eutérios , Voo Animal
8.
Anat Rec (Hoboken) ; 306(6): 1323-1355, 2023 06.
Artigo em Inglês | MEDLINE | ID: mdl-36458511

RESUMO

The diapsid plesiosaurs were pelagic and inhabited the oceans from the Triassic to the Cretaceous. A key evolutionary character of plesiosaurs is the four wing-like flippers. While it is mostly accepted that plesiosaurs were underwater fliers like marine turtles, penguins, and maybe whales, other swimming styles have been suggested in the past. These are rowing and a combination of rowing and underwater flight (e.g., pig-nosed turtle, sea lion). Underwater fliers use lift in contrast to rowers that employ drag. For efficiently profiting of lift during underwater flying, it is necessary that plesiosaurs twisted their flippers by muscular activity. To research the evolution of flipper twisting in plesiosaurs and functionally analogous taxa, including turtles, we used anatomical network analysis (AnNA) and reassessed distal flipper muscle functions. We coded bone-to-bone and additionally muscle-to-bone contacts in N × N matrices for foreflippers of the plesiosaur, the loggerhead sea turtle, the pig-nosed turtle, the African penguin, the California sea lion, and the humpback whale based on literature data. In "R," "igraph" was run by using a walktrap algorithm to obtain morphofunctional modules. AnNA revealed that muscle-to-bone contacts are needed to detect contributions of modules to flipper motions, whereas only-bone matrices are not informative for that. Furthermore, the plesiosaur, the marine turtles, the seal, and the penguin flipper twisting mechanisms, but the penguin cannot actively twist the flipper trailing edge. Finally, the foreflipper of the pig-nosed turtle and of the whale is not actively twisted during swimming.


Assuntos
Caniformia , Jubarte , Tartarugas , Animais , Suínos , Hidrodinâmica , Invenções , Tartarugas/fisiologia , Natação/fisiologia , Cetáceos
9.
Nat Commun ; 13(1): 5807, 2022 10 11.
Artigo em Inglês | MEDLINE | ID: mdl-36220806

RESUMO

The labyrinth of the vertebrate inner ear is a sensory system that governs the perception of head rotations. Central hypotheses predict that labyrinth shape and size are related to ecological adaptations, but this is under debate and has rarely been tested outside of mammals. We analyze the evolution of labyrinth morphology and its ecological drivers in living and fossil turtles, an understudied group that underwent multiple locomotory transitions during 230 million years of evolution. We show that turtles have unexpectedly large labyrinths that evolved during the origin of aquatic habits. Turtle labyrinths are relatively larger than those of mammals, and comparable to many birds, undermining the hypothesis that labyrinth size correlates directly with agility across vertebrates. We also find that labyrinth shape variation does not correlate with ecology in turtles, undermining the widespread expectation that reptilian labyrinth shapes convey behavioral signal, and demonstrating the importance of understudied groups, like turtles.


Assuntos
Orelha Interna , Tartarugas , Animais , Aves , Fósseis , Mamíferos , Filogenia , Tartarugas/anatomia & histologia
10.
J Exp Zool B Mol Dev Evol ; 338(8): 495-504, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35915572

RESUMO

We compared embryogenesis of five species of domesticated even-toed and one odd-toed ungulate and used a phylogenetic framework to contextualize such comparison. Organ systems that occur relatively earlier in embryogenesis generally have more time to develop and therefore are found to be more mature at birth when compared to structures that appear later in development. We hypothesized that the less mature the animals' organs are at birth, the more they are susceptible to artificial selection. The horse had the most mature organs at birth, followed by cattle, reindeer, sheep/goat, and pig. This pattern of maturity could be observed almost during the entire development. Heterochronic shifts among species were observed only after fur starts to develop. Changes in the fur coloration are one of the first observable signs of domestication and the heterochrony of this trait may be related to the effects on neural crest-derived pigment cells by artificial selection. The six ungulate species also differ in the relative duration of their weaning period and the potential extent of its artificial shortening. We put all these traits in the context of their inherited evolutionary characteristics and artificial domestication process. Related to their altriciality, carnivoran domesticates, which also belong to Scrotifera, are less mature at birth than all domesticated ungulates. Although we detected clear character correlations to life history traits, it is impossible based on the present data, to trace specific exaptations to the domestication process. We hypothesize a deep time developmental penetration of adult characters into embryogenesis.


Assuntos
Domesticação , Seleção Genética , Bovinos , Animais , Ovinos , Suínos , Cavalos , Filogenia , Mamíferos , Desenvolvimento Embrionário
11.
J Exp Zool B Mol Dev Evol ; 338(8): 447-459, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35604321

RESUMO

Studies of domesticated animals have greatly contributed to our understanding of avian embryology. Foundational questions in developmental biology were motivated by Aristotle's observations of chicken embryos. By the 19th century, the chicken embryo was at the center stage of developmental biology, but how closely does this model species mirror the ample taxonomic diversity that characterizes the avian tree of life? Here, we provide a brief overview of the taxonomic breadth of comparative embryological studies in birds. We particularly focused on staging tables and papers that attempted to document the timing of developmental transformations. We show that most of the current knowledge of avian embryology is based on Galliformes (chicken and quail) and Anseriformes (duck and goose). Nonetheless, data are available for some ecologically diverse avian subclades, including Struthioniformes (e.g., ostrich, emu) and Sphenisciformes (penguins). Thus far, there has only been a handful of descriptive embryological studies in the most speciose subclade of Aves, that is, the songbirds (Passeriniformes). Furthermore, we found that temporal variances for developmental events are generally uniform across a consensus chronological sequence for birds. Based on the available data, developmental trajectories for chicken and other model species appear to be highly similar. We discuss future avenues of research in comparative avian embryology in light of the currently available wealth of data on domesticated species and beyond.


Assuntos
Galinhas , Domesticação , Animais , Embrião de Galinha , Gansos
12.
J Morphol ; 283(7): 908-931, 2022 07.
Artigo em Inglês | MEDLINE | ID: mdl-35373381

RESUMO

During development, the embryonic cartilaginous skull in most vertebrates is partially replaced by bones with endochondral and perichondral ossifications. Muscle attachments are thought to influence the patterns of ossification and, hence, the differentiation of the skull. To investigate the association between muscle attachments and early ossifications of reptilian embryos, we conducted digital 3D reconstructions of the cranium, the head, and the neck musculature from a histological section series of a late term embryonic tuatara, Sphenodon punctatus, with a total body length of 52 mm. As the sole living rhynchocephalian species, it is an important outgroup in comparative studies of squamate evolution. We found that head and neck muscles are largely associated with early ossification of the basal plate and the palatoquadrate, and with three other ossifications in an older specimen with a total body length of 72 mm. These results suggest that tensile forces resulting from embryonic muscle contraction are largely, but not exclusively, correlated with the area of endochondral ossification in the chondrocranium and palatoquadrate in tuatara. Beyond little-known genetic factors, the complexity of chondrocranial architecture, the progress of its development, and the effect of multiple muscle transmitting forces in the chondrocranium must be considered to provide a more comprehensive discussion of the mechanical properties of the embryonic skull.


Assuntos
Osteogênese , Répteis , Animais , Cartilagem/anatomia & histologia , Músculos/anatomia & histologia , Répteis/anatomia & histologia , Crânio/anatomia & histologia , Crânio/diagnóstico por imagem
13.
Dev Growth Differ ; 64(3): 178-191, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-35297501

RESUMO

Embryogenesis is the first step in the ontogenetic life journey of any individual, and is thus a starting point for natural selection to cause evolutionary change. There are slight variations in the timing of embryonic development, known as heterochrony, which may eventually lead to major differences in adult anatomy. To test this hypothesis, the embryonic development of three closely related lizard species, Darevskia armeniaca, Lacerta agilis, and L. viridis, which are adapted to different habitats, was compared by analyzing discrete timing characters. Both intra- and interspecific variation was detected. The latter may be interpreted as embryonic pre-adaptions to later adult lifestyles, demonstrating that developmental penetrance manifests within a few million years. Traits with large intraspecific temporal variation, such as limb-related features, were susceptible to natural selection. In particular, the mountain-dwelling, climbing species D. armeniaca showed embryonic preadaptions by an early developing limb anlagen. This observation demonstrated interspecific variation, which was elusive in a previous comparative study based on purely metric data of developing limb lengths, and highlighted the importance of multiple data sources to draw robust conclusions about evolutionary change. Timing differences indicated unexplored ecological adaptations of the poorly understood lifestyle of these lizards. Thus, embryonic research provides a platform to explore superficially hidden evolutionary adaptations of all organisms on Earth.


Assuntos
Lagartos , Adaptação Fisiológica , Animais , Evolução Biológica , Desenvolvimento Embrionário , Extremidades , Lagartos/anatomia & histologia
14.
Proc Natl Acad Sci U S A ; 118(44)2021 11 02.
Artigo em Inglês | MEDLINE | ID: mdl-34716275

RESUMO

The anterior end of the mammalian face is characteristically composed of a semimotile nose, not the upper jaw as in other tetrapods. Thus, the therian nose is covered ventrolaterally by the "premaxilla," and the osteocranium possesses only a single nasal aperture because of the absence of medial bony elements. This stands in contrast to those in other tetrapods in whom the premaxilla covers the rostral terminus of the snout, providing a key to understanding the evolution of the mammalian face. Here, we show that the premaxilla in therian mammals (placentals and marsupials) is not entirely homologous to those in other amniotes; the therian premaxilla is a composite of the septomaxilla and the palatine remnant of the premaxilla of nontherian amniotes (including monotremes). By comparing topographical relationships of craniofacial primordia and nerve supplies in various tetrapod embryos, we found that the therian premaxilla is predominantly of the maxillary prominence origin and associated with mandibular arch. The rostral-most part of the upper jaw in nonmammalian tetrapods corresponds to the motile nose in therian mammals. During development, experimental inhibition of primordial growth demonstrated that the entire mammalian upper jaw mostly originates from the maxillary prominence, unlike other amniotes. Consistently, cell lineage tracing in transgenic mice revealed a mammalian-specific rostral growth of the maxillary prominence. We conclude that the mammalian-specific face, the muzzle, is an evolutionary novelty obtained by overriding ancestral developmental constraints to establish a novel topographical framework in craniofacial mesenchyme.


Assuntos
Evolução Biológica , Face/anatomia & histologia , Ossos Faciais/anatomia & histologia , Animais , Anuros/anatomia & histologia , Embrião de Galinha , Cabeça/anatomia & histologia , Arcada Osseodentária/anatomia & histologia , Lagartos/anatomia & histologia , Mamíferos , Mandíbula/anatomia & histologia , Maxila/anatomia & histologia , Camundongos , Camundongos Endogâmicos C57BL
15.
BMC Ecol Evol ; 21(1): 136, 2021 07 05.
Artigo em Inglês | MEDLINE | ID: mdl-34225664

RESUMO

BACKGROUND: Placodontia is a Triassic sauropterygian reptile group characterized by flat and enlarged crushing teeth adapted to a durophagous diet. The enigmatic placodont Henodus chelyops has numerous autapomorphic character states, including extreme tooth count reduction to only a single pair of palatine and dentary crushing teeth. This renders the species unusual among placodonts and challenges identification of its phylogenetic position. RESULTS: The skulls of two Henodus chelyops specimens were visualized with synchrotron tomography to investigate the complete anatomy of their functional and replacement crushing dentition in 3D. All teeth of both specimens were segmented, measured, and statistically compared to reveal that H. chelyops teeth are much smaller than the posterior palatine teeth of other cyamodontoid placodonts with the exception of Parahenodus atancensis from the Iberian Peninsula. The replacement teeth of this species are quite similar in size and morphology to the functional teeth. CONCLUSION: As other placodonts, Henodus chelyops exhibits vertical tooth replacement. This suggests that vertical tooth replacement arose relatively early in placodont phylogeny. Analysis of dental morphology in H. chelyops revealed a concave shape of the occlusal surface and the notable absence of a central cusp. This dental morphology could have reduced dental wear and protected against failure. Hence, the concave teeth of H. chelyops appear to be adapted to process small invertebrate items, such as branchiopod crustaceans. Small gastropods were encountered in the matrix close to both studied skulls.


Assuntos
Dentição , Dente , Animais , Arcada Osseodentária , Odontogênese , Filogenia , Dente/diagnóstico por imagem
16.
Proc Biol Sci ; 288(1953): 20210392, 2021 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-34130497

RESUMO

Domestication provides an outstanding opportunity for biologists to explore the underpinnings of organismal diversification. In domesticated animals, selective breeding for exaggerated traits is expected to override genetic correlations that normally modulate phenotypic variation in nature. Whether this strong directional selection affects the sequence of tightly synchronized events by which organisms arise (ontogeny) is often overlooked. To address this concern, we compared the ontogeny of the red junglefowl (RJF) (Gallus gallus) to four conspecific lineages that underwent selection for traits of economic or ornamental value to humans. Trait differentiation sequences in embryos of these chicken breeds generally resembled the representative ancestral condition in the RJF, thus revealing that early ontogeny remains highly canalized even during evolution under domestication. This key finding substantiates that the genetic cost of domestication does not necessarily compromise early ontogenetic steps that ensure the production of viable offspring. Instead, disproportionate beak and limb growth (allometry) towards the end of ontogeny better explained phenotypes linked to intense selection for industrial-scale production over the last 100 years. Illuminating the spatial and temporal specificity of development is foundational to the enhancement of chicken breeds, as well as to ongoing research on the origins of phenotypic variation in wild avian species.


Assuntos
Galinhas , Domesticação , Animais , Animais Domésticos , Galinhas/genética , Humanos , Fenótipo
17.
Biol Rev Camb Philos Soc ; 96(5): 2229-2257, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34056833

RESUMO

The morphology of the temporal region in the tetrapod skull traditionally has been a widely discussed feature of vertebrate anatomy. The evolution of different temporal openings in Amniota (mammals, birds, and reptiles), Lissamphibia (frogs, salamanders, and caecilians), and several extinct tetrapod groups has sparked debates on the phylogenetic, developmental, and functional background of this region in the tetrapod skull. This led most famously to the erection of different amniote taxa based on the number and position of temporal fenestrae in their skulls. However, most of these taxa are no longer recognised to represent natural groupings and the morphology of the temporal region is not necessarily an adequate trait for use in the reconstruction of amniote phylogenies. Yet, new fossil finds, most notably of parareptiles and stem-turtles, as well as modern embryological and biomechanical studies continue to provide new insights into the morphological diversity of the temporal region. Here, we introduce a novel comprehensive classification scheme for the various temporal morphotypes in all Tetrapoda that is independent of phylogeny and previous terminology and may facilitate morphological comparisons in future studies. We then review the history of research on the temporal region in the tetrapod skull. We document how, from the early 19th century with the first recognition of differences in the temporal region to the first proposals of phylogenetic relationships and their assessment over the centuries, the phylogenetic perspective on the temporal region has developed, and we highlight the controversies that still remain. We also compare the different functional and developmental drivers proposed for the observed morphological diversity and how the effects of internal and external factors on the structure of the tetrapod skull have been interpreted.


Assuntos
Répteis , Crânio , Animais , Anuros , Evolução Biológica , Fósseis , Filogenia , Répteis/anatomia & histologia , Crânio/anatomia & histologia , Lobo Temporal
18.
Front Zool ; 18(1): 21, 2021 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-33926502

RESUMO

BACKGROUND: Birds exhibit an enormous diversity in adult skull shape (disparity), while their embryonic chondrocrania are considered to be conserved across species. However, there may be chondrocranial features that are diagnostic for bird clades or for Aves as a whole. We synthesized and analyzed information on the sequence of chondrification of 23 elements in ten bird species and five outgroups. Moreover, we critically considered the developmental morphology of the chondrocrania of 21 bird species and examined whether the diversity in adult skull shape is reflected in the development of the embryonic skull, and whether there are group-specific developmental patterns. RESULTS: We found that chondrocranial morphology is largely uniform in its major features, with some variation in the presence or absence of fenestrae and other parts. In kiwis (Apteryx), the unique morphology of the bony skull in the orbito-nasal region is reflected in its chondrocranial anatomy. Finally, differences in morphology and chondrification sequence may distinguish between different Palaeognathae and Neognathae and between the Galloanserae and Neoaves. The sequence of chondrification is largely conserved in birds, but with some variation in most regions. The peri- and prechordal areas in the base of the chondrocranium are largely conserved. In contrast to the outgroups, chondrification in birds starts in the acrochordal cartilage and the basicranial fenestra is formed secondarily. Further differences concern the orbital region, including early chondrification of the pila antotica and the late formation of the planum supraseptale. CONCLUSION: Synthesizing information on chondrocranial development confronts terminological issues and a lack of comparable methods used (e.g., different staining; whole-mounts versus histology). These issues were taken into consideration when assessing differences across species. The summary of works on avian chondrocranial development, covered more than a century, and a comparison of the chondrification sequence among birds could be conducted. Future studies could test the hypothesis that chondrocranial disparity in Aves, in terms of the shape and proportion of individual elements, could be as large as adult skull disparity, despite conserved developmental patterns and the richness of forms in other (dermal) portions of the skull.

19.
Dev Dyn ; 250(8): 1140-1159, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33683772

RESUMO

BACKGROUND: How bats deviate heterochronically from other mammals remains largely unresolved, reflecting the lack of a quantitative staging framework allowing comparison among species. The standard event system (SES) is an embryonic staging system allowing quantitative detection of interspecific developmental variations. Here, the first SES-based staging system for bats, using Asian parti-colored bat (Vespertilio sinensis) is introduced. General aspects of normal embryonic development and the three-dimensional development of the bat cochlea were described for the first time. Recoding the embryonic staging tables of 18 previously reported bat species and Mus musculus into the SES system, quantitative developmental comparisons were performed. RESULTS: It was found that limb bud development of V. sinensis is relatively late among 19 bat species and late limb development is a shared trait of vespertilionid bats. The inner ear cochlear canal forms before the semicircular canal in V. sinensis while the cochlear canal forms after the semicircular canal in non-volant mammals. CONCLUSIONS: The present approach using the SES system provides a powerful framework to detect the peculiarities of bat development. Incorporating the timing of gene expression patterns into the SES framework will further contribute to the understanding of the evolution of specialized features in bats.


Assuntos
Quirópteros/embriologia , Cóclea/embriologia , Organogênese/fisiologia , Animais , Feminino , Camundongos , Fenótipo , Gravidez
20.
Dev Dyn ; 250(9): 1300-1317, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-33511716

RESUMO

BACKGROUND: In vertebrates, the skull evolves from a complex network of dermal bones and cartilage-the latter forming the pharyngeal apparatus and the chondrocranium. Squamates are particularly important in this regard as they maintain at least part of the chondrocranium throughout their whole ontogeny until adulthood. Anguid lizards represent a unique group of squamates, which contains limbed and limbless forms and show conspicuous variation of the adult skull. RESULTS: Based on several emboadryonic stages of the limbless lizards Pseudopus apodus and Anguis fragilis, and by comparing with other squamates, we identified and interpreted major differences in chondrocranial anatomy. Among others, the most important differences are in the orbitotemporal region. P. apodus shows a strikingly similar development of this region to other squamates. Unexpectedly, however, A. fragilis differs considerably in the composition of the orbitotemporal region. In addition, A. fragilis retains a paedomorphic state of the nasal region. CONCLUSIONS: Taxonomic comparisons indicate that even closely related species with reduced limbs show significant differences in chondrocranial anatomy. The Pearson correlation coefficient suggests strong correlation between chondrocranial reduction and limb reduction. We pose the hypothesis that limb reduction could be associated with the reduction in chondrocrania by means of genetic mechanisms.


Assuntos
Evolução Biológica , Lagartos , Animais , Cartilagem , Extremidades , Crânio/anatomia & histologia
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