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1.
J Evol Biol ; 33(2): 178-188, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31622509

RESUMO

Oviraptorosaurs are bird-like theropod dinosaurs that thrived in the final pre-extinction ecosystems during the latest Cretaceous, and the beaked, toothless skulls of derived species are regarded as some of the most peculiar among dinosaurs. Their aberrant morphologies are hypothesized to have been caused by rapid evolution triggered by an ecological/biological driver, but little is known about how their skull shapes and functional abilities diversified. Here, we use quantitative techniques to study oviraptorosaur skull form and mandibular function. We demonstrate that the snout is particularly variable, that mandibular form and upper/lower beak form are significantly correlated with phylogeny, and that there is a strong and significant correlation between mandibular function and mandible/lower beak shape, suggesting a form-function association. The form-function relationship and phylogenetic signals, along with a moderate allometric signal in lower beak form, indicate that similar mechanisms governed beak shape in oviraptorosaurs and extant birds. The two derived oviraptorosaur clades, oviraptorids and caenagnathids, are significantly separated in morphospace and functional space, indicating that they partitioned niches. Oviraptorids coexisting in the same ecosystem are also widely spread in morphological and functional space, suggesting that they finely partitioned feeding niches, whereas caenagnathids exhibit extreme disparity in beak size. The diversity of skull form and function was likely key to the diversification and evolutionary success of oviraptorosaurs in the latest Cretaceous.


Assuntos
Dinossauros/anatomia & histologia , Dinossauros/classificação , Ecossistema , Filogenia , Crânio/anatomia & histologia , Animais , Especiação Genética
2.
Sci Rep ; 12(1): 3010, 2022 02 22.
Artigo em Inglês | MEDLINE | ID: mdl-35194096

RESUMO

Oviraptorosaurians are an unusual and probably herbivorous group of theropod dinosaurs that evolved pneumatised crania with robust, toothless jaws, apparently adapted for producing a strong bite. Using 3D retrodeformed skull models of oviraptorid oviraptorosaurians Citipati, Khaan, and Conchoraptor, along with the earliest diverging oviraptorosaurian, Incisivosaurus, we digitally reconstruct jaw adductor musculature and estimate bite force to investigate cranial function in each species. We model muscle length change during jaw opening to constrain optimal and maximum gape angles. Results demonstrate oviraptorids were capable of much stronger bite forces than herbivorous theropods among Ornithomimosauria and Therizinosauria, relative to body mass and absolutely. Increased bite forces in oviraptorid oviraptorosaurians compared to the earliest diverging oviraptorosaurian result from expanded muscular space and different cranial geometry, not changes in muscular arrangement. Estimated optimal and maximum possible gapes are much smaller than published estimates for carnivorous theropods, being more similar to the herbivorous therizinosaurian theropod Erlikosaurus and modern birds. Restrictive gape and high bite force may represent adaptation towards exploiting tough vegetation, suggesting cranial function and dietary habits differed between oviraptorids and other herbivorous theropods. Differences in the relative strength of jaw adductor muscles between co-occurring oviraptorids may be a factor in niche partitioning, alongside body size.

3.
Curr Biol ; 32(3): 677-686.e3, 2022 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-34919807

RESUMO

Theropod dinosaurs underwent some of the most remarkable dietary changes in vertebrate evolutionary history, shifting from ancestral carnivory1-3 to hypercarnivory4,5 and omnivory/herbivory,6-9 with some taxa eventually reverting to carnivory.10-12 The mandible is an important tool for food acquisition in vertebrates and reflects adaptations to feeding modes and diets.13,14 The morphofunctional modifications accompanying the dietary changes in theropod dinosaurs are not well understood because most of the previous studies focused solely on the cranium and/or were phylogenetically limited in scope,12,15-21 while studies that include multiple clades are usually based on linear measurements and/or discrete osteological characters.8,22 Given the potential relationship between macroevolutionary change and ontogenetic pattern,23 we explore whether functional morphological patterns observed in theropod mandibular evolution show similarities to the ontogenetic trajectory. Here, we use finite element analysis to study the mandibles of non-avialan coelurosaurian theropods and demonstrate how feeding mechanics vary between dietary groups and major clades. We reveal an overall reduction in feeding-induced stresses along all theropod lineages through time. This is facilitated by a post-dentary expansion and the development of a downturned dentary in herbivores and an upturned dentary in carnivores likely via the "curved bone effect." We also observed the same reduction in feeding-induced stress in an ontogenetic series of jaws of the tyrannosaurids Tarbosaurus and Tyrannosaurus, which is best attributed to bone functional adaptation. This suggests that this common tendency for structural strengthening of the theropod mandible through time, irrespective of diet, is linked to "functional peramorphosis" of bone functional adaptations acquired during ontogeny.


Assuntos
Dinossauros , Animais , Evolução Biológica , Carnivoridade , Dinossauros/anatomia & histologia , Fósseis , Filogenia , Crânio/anatomia & histologia
4.
PeerJ ; 9: e12361, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34760377

RESUMO

Tooth replacement rate is an important feature related to feeding mechanics and food choices for dinosaurs. However, only a few data points are available for sauropod dinosaurs, partially due to rarity of relevant fossil material. Four somphospondylan sauropod species have been recovered from the Lower Cretaceous Aptian-Albian Haoling Formation in the Ruyang Basin, Henan Province of central China, but no cranial material has been reported except for a single crown. Here we report the discovery of the rostral portion of a left dentary with replacement teeth in its first five alveoli. Comparative anatomical study shows the partial dentary can be assigned to a member of early diverging somphospondylans. The non-destructive tooth length-based approach to estimating tooth formation time and replacement rate is adopted here. The estimated tooth replacement rate is 76 days, faster than that of Brachiosaurus (83 days) and much lower than typical late diverging lithostrotian titanosaurians (20 days). Thus, this discovery adds an intermediate tooth replacement rate in the evolution of titanosauriform sauropods and supports the idea that evolution of tooth replacement rate is clade-specific. This discovery also provides more information to understand the Ruyang sauropod assemblage, which includes one of the most giant dinosaurs to have walked our Earth (Ruyangosaurus giganteus).

5.
Sci Rep ; 7(1): 16247, 2017 11 24.
Artigo em Inglês | MEDLINE | ID: mdl-29176627

RESUMO

The Oviraptorosauria are a group of theropod dinosaurs that diverged from the typical carnivorous theropod diet. It includes two main lineages - Caenagnathidae and Oviraptoridae - that display a number of differences in mandibular morphology, but little is known about their functional consequences, hampering our understanding of oviraptorosaurian dietary evolution. This study presents the first in-depth description of the giant toothless mandible of Gigantoraptor, the only well-preserved stemward caenagnathid mandible. This mandible shows the greatest relative beak depth among caenagnathids, which is an adaptation seen in some modern birds for processing harder seeds. The presence of a lingual triturating shelf in caenagnathids more crownward than Gigantoraptor suggests a possible increased specialization towards shearing along this lineage. Like other oviraptorosaurs, the possession of a dorsally convex articular glenoid in Gigantoraptor indicates that propalinal jaw movement was probably an important mechanism for food processing, as in Sphenodon and dicynodonts. Oviraptorid mandibles were more suited for producing powerful bites (e.g. crushing-related) compared to caenagnathids: oviraptorids generally possess a deeper, more downturned beak, a taller coronoid process prominence and a larger medial mandibular fossa. This disparity in caenagnathid and oviraptorid mandible morphology potentially suggests specialization towards two different feeding styles - shearing and crushing-related mechanisms respectively.


Assuntos
Evolução Biológica , Dinossauros/anatomia & histologia , Mandíbula/anatomia & histologia , Animais , Fósseis/anatomia & histologia
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