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A New Titanosaurian Braincase from the Cretaceous "Lo Hueco" Locality in Spain Sheds Light on Neuroanatomical Evolution within Titanosauria.

Knoll F, Witmer LM, Ridgely RC, Ortega F, Sanz JL - PLoS ONE (2015)

Bottom Line: Here we describe a braincase from the uppermost Cretaceous locality of ''Lo Hueco" in Spain that is one of the most complete titanosaurian braincases found so far in Europe.Although the titanosaurian Ampelosaurus sp. is known from the same locality, this specimen is clearly a distinct taxon and presents a number of occipital characters found in Antarctosaurus and Jainosaurus, which are approximately coeval taxa from southern Gondwana.Compared with that of many sauropodomorphs, the endocast appears only slightly flexed in lateral view and bears similarities (e.g., reduction of the rostral dural expansion) with Gondwanan titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus.

View Article: PubMed Central - PubMed

Affiliation: School of Earth, Atmospheric & Environmental Sciences, University of Manchester, Manchester, United Kingdom; School of Earth Sciences, University of Bristol, Bristol, United Kingdom; Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain.

ABSTRACT
Despite continuous improvements, our knowledge of the neurocranial anatomy of sauropod dinosaurs as a whole is still poor, which is especially true for titanosaurians even though their postcranial remains are common in many Upper Cretaceous sites worldwide. Here we describe a braincase from the uppermost Cretaceous locality of ''Lo Hueco" in Spain that is one of the most complete titanosaurian braincases found so far in Europe. Although the titanosaurian Ampelosaurus sp. is known from the same locality, this specimen is clearly a distinct taxon and presents a number of occipital characters found in Antarctosaurus and Jainosaurus, which are approximately coeval taxa from southern Gondwana. The specimen was subjected to X-ray computed tomographic (CT) scanning, allowing the generation of 3D renderings of the endocranial cavity enclosing the brain, cranial nerves, and blood vessels, as well as the labyrinth of the inner ear. These findings add considerable knowledge to the field of sauropod paleoneuroanatomy in general and titanosaurian endocast diversity in particular. Compared with that of many sauropodomorphs, the endocast appears only slightly flexed in lateral view and bears similarities (e.g., reduction of the rostral dural expansion) with Gondwanan titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus. The vestibular system of the inner ear is somewhat contracted (i.e., the radius of the semicircular canals is small), but less so than expected in derived titanosaurians. However, as far as the new specimen and Jainosaurus can be contrasted, and with the necessary caution due to the small sample of comparative data currently available, the two taxa appear more similar to one another in endocast morphology than to other titanosaurians. Recent phylogenetic analyses of titanosaurians have not included virtually any of the taxa under consideration here, and thus the phylogenetic position of the new Spanish titanosaurian--even its generic, let alone specific, identification--is not possible at the moment. Nevertheless, both the braincase osteology and the endocast morphology suggest that the specimen represents a derived titanosaurian that presumably branched further from the base of Lithostrotia, potentially even near Saltasauridae, comparable in evolutionary terms with Jainosaurus.

No MeSH data available.


Related in: MedlinePlus

Endosseous labyrinths of some sauropod taxa discussed in the text, displayed on a cladogram.In lateral view. Dorsal is to the top. From left: surface renderings of CT images of the inner ears of Giraffatitan brancai (MB.R.2180.22.1–4, right side mirrored), Ampelosaurus sp. from Spain (MCCM-HUE-8741, right side mirrored), the indeterminate titanosaurian from Spain (MCCM-HUE-1667, left side), and the indeterminate titanosaurian from Uzbekistan (CCMGE 628/12457, left side). Scale bar equals 20 mm.
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pone.0138233.g008: Endosseous labyrinths of some sauropod taxa discussed in the text, displayed on a cladogram.In lateral view. Dorsal is to the top. From left: surface renderings of CT images of the inner ears of Giraffatitan brancai (MB.R.2180.22.1–4, right side mirrored), Ampelosaurus sp. from Spain (MCCM-HUE-8741, right side mirrored), the indeterminate titanosaurian from Spain (MCCM-HUE-1667, left side), and the indeterminate titanosaurian from Uzbekistan (CCMGE 628/12457, left side). Scale bar equals 20 mm.

Mentions: The vestibular system of the inner ear is somewhat contracted (i.e. the radius of the semicircular canals is small), but less so than in other titanosaurians (Fig 8), such as Bonatitan reigi ([8]: fig. 9A, E; [44]: fig. 13.8, 13.11), Ampelosaurus sp. ([9]: figs 4, S1, S2, S3), and CCMGE 628/12457 ([10]: fig. 4A-C). Compared with the situation in Giraffatitan brancai ([29]: fig. 6; [40]: fig. 3), the rostral semicircular canal of all titanosaurians, including CCMGE 628/12457 ([10]: fig. 4A-C), is much shorter (Fig 8). Although our knowledge of the morphology of the vestibular system among sauropod taxa is still deficient, this equalization of the length of the two vertical semicircular canals may well turn out to be a titanosaurian synapomorphy. We have previously brought up the reasons behind the reduction of the semicircular canal radii of curvature in most sauropods [9,29,42], and quantitative analyses are underway. In birds, the slenderness and great length of the semicircular canals is related inter alia with their level of exposure to abrupt displacements during flight [53]. The reduction of the relative length of the semicircular canals in titanosaurians (an observation in line with the above-mentioned reduction of the floccular recess) and other sauropods might be linked to a restricted head rotation range.


A New Titanosaurian Braincase from the Cretaceous "Lo Hueco" Locality in Spain Sheds Light on Neuroanatomical Evolution within Titanosauria.

Knoll F, Witmer LM, Ridgely RC, Ortega F, Sanz JL - PLoS ONE (2015)

Endosseous labyrinths of some sauropod taxa discussed in the text, displayed on a cladogram.In lateral view. Dorsal is to the top. From left: surface renderings of CT images of the inner ears of Giraffatitan brancai (MB.R.2180.22.1–4, right side mirrored), Ampelosaurus sp. from Spain (MCCM-HUE-8741, right side mirrored), the indeterminate titanosaurian from Spain (MCCM-HUE-1667, left side), and the indeterminate titanosaurian from Uzbekistan (CCMGE 628/12457, left side). Scale bar equals 20 mm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596832&req=5

pone.0138233.g008: Endosseous labyrinths of some sauropod taxa discussed in the text, displayed on a cladogram.In lateral view. Dorsal is to the top. From left: surface renderings of CT images of the inner ears of Giraffatitan brancai (MB.R.2180.22.1–4, right side mirrored), Ampelosaurus sp. from Spain (MCCM-HUE-8741, right side mirrored), the indeterminate titanosaurian from Spain (MCCM-HUE-1667, left side), and the indeterminate titanosaurian from Uzbekistan (CCMGE 628/12457, left side). Scale bar equals 20 mm.
Mentions: The vestibular system of the inner ear is somewhat contracted (i.e. the radius of the semicircular canals is small), but less so than in other titanosaurians (Fig 8), such as Bonatitan reigi ([8]: fig. 9A, E; [44]: fig. 13.8, 13.11), Ampelosaurus sp. ([9]: figs 4, S1, S2, S3), and CCMGE 628/12457 ([10]: fig. 4A-C). Compared with the situation in Giraffatitan brancai ([29]: fig. 6; [40]: fig. 3), the rostral semicircular canal of all titanosaurians, including CCMGE 628/12457 ([10]: fig. 4A-C), is much shorter (Fig 8). Although our knowledge of the morphology of the vestibular system among sauropod taxa is still deficient, this equalization of the length of the two vertical semicircular canals may well turn out to be a titanosaurian synapomorphy. We have previously brought up the reasons behind the reduction of the semicircular canal radii of curvature in most sauropods [9,29,42], and quantitative analyses are underway. In birds, the slenderness and great length of the semicircular canals is related inter alia with their level of exposure to abrupt displacements during flight [53]. The reduction of the relative length of the semicircular canals in titanosaurians (an observation in line with the above-mentioned reduction of the floccular recess) and other sauropods might be linked to a restricted head rotation range.

Bottom Line: Here we describe a braincase from the uppermost Cretaceous locality of ''Lo Hueco" in Spain that is one of the most complete titanosaurian braincases found so far in Europe.Although the titanosaurian Ampelosaurus sp. is known from the same locality, this specimen is clearly a distinct taxon and presents a number of occipital characters found in Antarctosaurus and Jainosaurus, which are approximately coeval taxa from southern Gondwana.Compared with that of many sauropodomorphs, the endocast appears only slightly flexed in lateral view and bears similarities (e.g., reduction of the rostral dural expansion) with Gondwanan titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus.

View Article: PubMed Central - PubMed

Affiliation: School of Earth, Atmospheric & Environmental Sciences, University of Manchester, Manchester, United Kingdom; School of Earth Sciences, University of Bristol, Bristol, United Kingdom; Departamento de Paleobiología, Museo Nacional de Ciencias Naturales-CSIC, Madrid, Spain.

ABSTRACT
Despite continuous improvements, our knowledge of the neurocranial anatomy of sauropod dinosaurs as a whole is still poor, which is especially true for titanosaurians even though their postcranial remains are common in many Upper Cretaceous sites worldwide. Here we describe a braincase from the uppermost Cretaceous locality of ''Lo Hueco" in Spain that is one of the most complete titanosaurian braincases found so far in Europe. Although the titanosaurian Ampelosaurus sp. is known from the same locality, this specimen is clearly a distinct taxon and presents a number of occipital characters found in Antarctosaurus and Jainosaurus, which are approximately coeval taxa from southern Gondwana. The specimen was subjected to X-ray computed tomographic (CT) scanning, allowing the generation of 3D renderings of the endocranial cavity enclosing the brain, cranial nerves, and blood vessels, as well as the labyrinth of the inner ear. These findings add considerable knowledge to the field of sauropod paleoneuroanatomy in general and titanosaurian endocast diversity in particular. Compared with that of many sauropodomorphs, the endocast appears only slightly flexed in lateral view and bears similarities (e.g., reduction of the rostral dural expansion) with Gondwanan titanosaurians such as Jainosaurus, Bonatitan, and Antarctosaurus. The vestibular system of the inner ear is somewhat contracted (i.e., the radius of the semicircular canals is small), but less so than expected in derived titanosaurians. However, as far as the new specimen and Jainosaurus can be contrasted, and with the necessary caution due to the small sample of comparative data currently available, the two taxa appear more similar to one another in endocast morphology than to other titanosaurians. Recent phylogenetic analyses of titanosaurians have not included virtually any of the taxa under consideration here, and thus the phylogenetic position of the new Spanish titanosaurian--even its generic, let alone specific, identification--is not possible at the moment. Nevertheless, both the braincase osteology and the endocast morphology suggest that the specimen represents a derived titanosaurian that presumably branched further from the base of Lithostrotia, potentially even near Saltasauridae, comparable in evolutionary terms with Jainosaurus.

No MeSH data available.


Related in: MedlinePlus