Neurovascular anatomy of dwarf dinosaur implies precociality in sauropods
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eLife assessment
This paper describes the anatomy of important fossil remains of the dwarf dinosaur Europasaurus, providing compelling evidence for precociality. Only a handful of papers provide detailed information on sauropod neuroanatomy - as such this paper will be of interest to a relatively wide range of researchers, in particular vertebrate palaeontologists, and comparative anatomists.
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Abstract
Macronaria, a group of mostly colossal sauropod dinosaurs, comprised the largest terrestrial vertebrates of Earth’s history. However, some of the smallest sauropods belong to this group as well. The Late Jurassic macronarian island dwarf Europasaurus holgeri is one of the most peculiar and best-studied sauropods worldwide. So far, the braincase material of this taxon from Germany pended greater attention. With the aid of micro-computed tomography (microCT), we report on the neuroanatomy of the nearly complete braincase of an adult individual, as well as the inner ears (endosseous labyrinths) of one other adult and several juveniles (the latter also containing novel vascular cavities). The presence of large and morphologically adult inner ears in juvenile material suggests precociality. Our findings add to the diversity of neurovascular anatomy in sauropod braincases and buttress the perception of sauropods as fast-growing and autonomous giants with manifold facets of reproductive and social behaviour. This suggests that – apart from sheer size – little separated Europasaurus from its large-bodied relatives.
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eLife assessment
This paper describes the anatomy of important fossil remains of the dwarf dinosaur Europasaurus, providing compelling evidence for precociality. Only a handful of papers provide detailed information on sauropod neuroanatomy - as such this paper will be of interest to a relatively wide range of researchers, in particular vertebrate palaeontologists, and comparative anatomists.
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Reviewer #1 (Public Review):
Shade et al. describe the endocast and semicircular canal of multiple individuals and ontogenetic stages belonging to the taxon Europasaurus. Investigation of these traits lead the authors to suggest that this dwarfed sauropod was precocial and potentially capable to communicate with other individuals of the same species.
Overall, I enjoyed the manuscript, because of the importance of the taxon and the gap in our knowledge that this study fills. The anatomical descriptions of the endocast and semicircular canal are well done and detailed. That being said, the manuscript can be improved in terms of comparative framework: in the current version, the manuscript only covers anatomical comparisons in the discussion. I would suggest the authors include a final figure showing multiple endocasts of other …
Reviewer #1 (Public Review):
Shade et al. describe the endocast and semicircular canal of multiple individuals and ontogenetic stages belonging to the taxon Europasaurus. Investigation of these traits lead the authors to suggest that this dwarfed sauropod was precocial and potentially capable to communicate with other individuals of the same species.
Overall, I enjoyed the manuscript, because of the importance of the taxon and the gap in our knowledge that this study fills. The anatomical descriptions of the endocast and semicircular canal are well done and detailed. That being said, the manuscript can be improved in terms of comparative framework: in the current version, the manuscript only covers anatomical comparisons in the discussion. I would suggest the authors include a final figure showing multiple endocasts of other sauropodomorphs to better show the evolutionary morphological transitions affecting the endocast and semicircular canal in this clade. It would also be useful to have tables with measurements comparing hearing frequencies among non-avian dinosaurs with Europasaurus: is this taxon peculiar in this? Or is it in the range of other taxa? Finally, the fact that vocalization was possible in this taxon does not imply gregarious behavior: this should be specified better in the manuscript.
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Reviewer #2 (Public Review):
The authors aim to analyze and describe the neuroanatomy of the Late Jurassic sauropod Europasaurus holgeri. This is done by scanning with microCT both adult and juvenile specimens.
The authors successfully report in detail the overall anatomy of the Europasaurus braincase, as well as morphological characteristics so far undescribed in this taxon. Precociality in juveniles is suggested and also well-supported. Comparisons made with other sauropods are considered appropriate and clear.
Aspects of reproductive and social behavior in this taxon are deduced from the estimated auditory capabilities. They are not investigated in detail and more details regarding these aspects would be welcomed in the discussion.
Images in the manuscript are well-presented and clear, supporting adequately the description. Slicing …
Reviewer #2 (Public Review):
The authors aim to analyze and describe the neuroanatomy of the Late Jurassic sauropod Europasaurus holgeri. This is done by scanning with microCT both adult and juvenile specimens.
The authors successfully report in detail the overall anatomy of the Europasaurus braincase, as well as morphological characteristics so far undescribed in this taxon. Precociality in juveniles is suggested and also well-supported. Comparisons made with other sauropods are considered appropriate and clear.
Aspects of reproductive and social behavior in this taxon are deduced from the estimated auditory capabilities. They are not investigated in detail and more details regarding these aspects would be welcomed in the discussion.
Images in the manuscript are well-presented and clear, supporting adequately the description. Slicing of the CT data is sufficiently clear although a "polishing" of the final renders in some cases would be appreciated. Again, it is not necessary, since images are clear enough, but only suggested.
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