Ben Creisler
New and recent non-dino papers:
Avian heads are characterized as having two extensive airâfilled systems lined with epithelia; the paranasal and paratympanic sinuses. Many diverticula derived from the paratympanic sinus system are known to reticulate with each other to form a single merged pneumatic space within the adult braincase. However, the development of these complex branching and reticulating epithelia has not been examined in detail. In this study, we describe the comprehensive developmental pattern of the paratympanic sinus and its associated soft tissues in a model bird, Japanese quail (Coturnix japonica). The data are derived from threeâdimensional reconstructions based on histological sections and soft tissue enhanced microâCT data. Those data provide the foundation of the complex hierarchical developmental pattern of the paratympanic sinus system. Moreover, associations with other tissues help establish key morphologies that identify each pneumatic entity. This study clarifies the developmental relationships of the ventral portions of the paratympanic sinus system, the siphoneal diverticulum and marginal sinus, based on the ligaments associated with the Eustachian tube. In addition, detailed histological pneumatic morphologies reveal hitherto unknown epithelial diversity, which may be indicative of equally complex developmental processes. We use the pneumatization of the quadrate as an example to support a close relationship with vascular growth and pneumatic epithelia invasion into ossified bone. We confirm pneumatic diverticula never enter into cartilages, possibly due to the absence of vasculature in these tissues. Lastly, we use the concept of a morphogenetic tree as a tool to help present the complex developmental pattern of the paratympanic sinus system and apply it toward inferring pneumatic morphologies in a nonavian theropod braincase.
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Jordan Bestwick, David M. Unwin & Mark A. Purnell (2019)
Dietary differences in archosaur and lepidosaur reptiles revealed by dental microwear textural analysis.
Scientific Reports 9, Article number: 11691
DOI:
https://doi.org/10.1038/s41598-019-48154-9https://www.nature.com/articles/s41598-019-48154-9Free pdf:
https://www.nature.com/articles/s41598-019-48154-9.pdfReptiles are key components of modern ecosystems, yet for many species detailed characterisations of their diets are lacking. Data currently used in dietary reconstructions are limited either to the last few meals or to proxy records of average diet over temporal scales of months to years, providing only coarse indications of trophic level(s). Proxies that record information over weeks to months would allow more accurate reconstructions of reptile diets and better predictions of how ecosystems might respond to global change drivers. Here, we apply dental microwear textural analysis (DMTA) to dietary guilds encompassing both archosaurian and lepidosaurian reptiles, demonstrating its value as a tool for characterising diets over temporal scales of weeks to months. DMTA, involving analysis of the three-dimensional, sub-micrometre scale textures created on tooth surfaces by interactions with food, reveals that the teeth of reptiles with diets dominated by invertebrates, particularly invertebrates with hard exoskeletons (e.g. beetles and snails), exhibit rougher microwear textures than reptiles with vertebrate-dominated diets. Teeth of fish-feeding reptiles exhibit the smoothest textures of all guilds. These results demonstrate the efficacy of DMTA as a dietary proxy in taxa from across the phylogenetic range of extant reptiles. This method is applicable to extant taxa (living or museum specimens) and extinct reptiles, providing new insights into past, present and future ecosystems.
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The amniote jaw complex is a remarkable amalgamation of derivatives from distinct embryonic cell lineages. During development, the cells in these lineages experience concerted movements, migrations, and signaling interactions that take them from their initial origins to their final destinations and imbue their derivatives with aspects of form including their axial orientation, anatomical identity, size, and shape. Perturbations along the way can produce defects and disease, but also generate the variation necessary for jaw evolution and adaptation. We focus on molecular and cellular mechanisms that regulate form in the amniote jaw complex, and that enable structural and functional integration. Special emphasis is placed on the role of cranial neural crest mesenchyme (NCM) during the species-specific patterning of bone, cartilage, tendon, muscle, and other jaw tissues. We also address the effects of biomechanical forces during jaw development and discuss ways in which certain molecular and cellular responses add adaptive and evolutionary plasticity to jaw morphology. Overall, we highlight how variation in molecular and cellular programs can promote the phenomenal diversity and functional morphology achieved during amniote jaw evolution or lead to the range of jaw defects and disease that affect the human condition.
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Celeste M. PÃrez-Ben, Ana M. BÃez & Rainer R. Schoch (2019)
Morphological evolution of the skull roof in temnospondyl amphibians mirrors conservative ontogenetic patterns.
Zoological Journal of the Linnean Society: zlz068
doi:
https://doi.org/10.1093/zoolinnean/zlz068https://academic.oup.com/zoolinnean/advance-article-abstract/doi/10.1093/zoolinnean/zlz068/5546051Addressing the patterns of ontogenetic allometry is relevant to understand morphological diversification because allometry might constrain evolution to specific directions of change in shape but also facilitate phenotypic differentiation along lines of least evolutionary resistance. Temnospondyl amphibians are a suitable group to address these issues from a deep-time perspective because different growth stages are known for numerous Palaeozoic and Mesozoic species. Herein we examine the patterns of ontogenetic allometry in the skull roof of 15 temnospondyl species and their relationship with adult morphological evolution. Using geometric morphometrics, we assessed ontogenetic and evolutionary allometries of this cranial part and the distribution of adult shapes in the morphospace to investigate whether these patterns relate to each other and/or to lifestyle and phylogeny. We found conspicuous stereotyped ontogenetic changes of the skull roof which are mirrored at the evolutionary level and consistency of the adult shape with phylogeny rather than lifestyle. These results suggest that the evolution of adult cranial shape was significantly biased by development towards pathways patterned by ontogenetic change in shape. The retrieved conserved patterns agree with a widespread evolutionary craniofacial trend found in amniotes, suggesting that they might have originated early in tetrapod evolutionary history or even earlier.ÂÂ
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The pharyngeal arches are a prominent and significant feature of vertebrate embryos. These are visible as a series of bulges on the lateral surface of the embryonic head. In humans, and other amniotes, there are five pharyngeal arches numbered 1, 2, 3, 4 and 6; note the missing '5'. This is the standard scheme for the numbering of these structures, and it is a feature of modern anatomy textbooks. In this article, we discuss the rationale behind this odd numbering, and consider its origins. One reason given is that there is a transient 5th arch that is never fully realized, while another is that this numbering reflects considerations from comparative anatomy. We show here, however, that neither of these reasons has substance. There is no evidence from embryology for a '5th arch, and the comparative argument does not hold as it does not apply across the vertebrates. We conclude that there is no justification for this strange numbering. We suggest that the pharyngeal arches should simply be numbered 1, 2, 3, 4 and 5 as this would be in keeping with the embryology and with the general numbering of the pharyngeal arches across the vertebrates.
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Also may be of interest:
Lophocion grangeri sp. nov.
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Phenacodontidae are a group of archaic ungulates in the early Paleogene and are considered to play an important role in the origin of some other ungulates, including perissodactyls. The early Eocene Lophocion asiaticus, the only unequivocal phenacodontid from Asia, is most closely related to North American Ectocion and probably closer to perissodactyls than is the latter, as evidenced by its more lophodont teeth. Here we named a new species of Lophocion, L. grangeri sp. nov., from the latest Paleocene (Clarkforkian 3) deposit in the Clarkâs Fork Basin of Wyoming. Although the holotype of the new species is only known by a right maxilla with P4-M2, its degree of lophodonty is similar to that of Lophocion but diverges from Ectocion in having the incipient protoloph and metaloph on upper molars. In dental morphology, Lophocion grangeri is somewhat intermediate between Ectocion and L. asiaticus, and probably gave rise to the latter during the Paleocene-Eocene transition. Both Lophocion and Ectocion are included in Phenacodontinae rather than Meniscotheriinae, but their phylogenetic relationship with other ungulates still remains obscure.