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. 2017 Sep 20;7(1):11931.
doi: 10.1038/s41598-017-11737-5.

Endocast of the Late Triassic (Carnian) dinosaur Saturnalia tupiniquim: implications for the evolution of brain tissue in Sauropodomorpha

Mario Bronzati  1   2 , Oliver W M Rauhut  3   4 , Jonathas S Bittencourt  5 , Max C Langer  6
Affiliations

Endocast of the Late Triassic (Carnian) dinosaur Saturnalia tupiniquim: implications for the evolution of brain tissue in Sauropodomorpha

Mario Bronzati et al. Sci Rep. .

Abstract

The evolutionary history of dinosaurs might date back to the first stages of the Triassic (c. 250-240 Ma), but the oldest unequivocal records of the group come from Late Triassic (Carnian - c. 230 Ma) rocks of South America. Here, we present the first braincase endocast of a Carnian dinosaur, the sauropodomorph Saturnalia tupiniquim, and provide new data regarding the evolution of the floccular and parafloccular lobe of the cerebellum (FFL), which has been extensively discussed in the field of palaeoneurology. Previous studies proposed that the development of a permanent quadrupedal stance was one of the factors leading to the volume reduction of the FFL of sauropods. However, based on the new data for S. tupiniquim we identified a first moment of FFL volume reduction in non-sauropodan Sauropodomorpha, preceding the acquisition of a fully quadrupedal stance. Analysing variations in FFL volume alongside other morphological changes in the group, we suggest that this reduction is potentially related to the adoption of a more restricted herbivore diet. In this context, the FFL of sauropods might represent a vestigial trait, retained in a reduced version from the bipedal and predatory early sauropodomorphs.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Figure 1
Figure 1
The early sauropodomorph Saturnalia tupiniquim. Skeletal reconstruction (A). Virtual preparation of cranial bones as preserved inside the matrix (B), with braincase highlighted in right lateral (C) view. Reconstruction of the soft tissues associated with the braincase: right inner ear in lateral (D) and dorsal (E) views, and endocast in lateral (F), dorsal (G), and, ventral (H) views. Abbreviations: asc – anterior semicircular canal; co – cochleae; fl – Floccular Fossae Lobe; ie – inner ear; lsc – lateral semicircular canal; psc – posterior semicircular canal; V – trigeminal nerve; VI – abducens nerve; VII – facial nerve; XII hypoglossal nerve. Scale bars = 1 cm.
Figure 2
Figure 2
Simplified Archosauriformes phylogeny highlighting character acquisition in Sauropodomorpha (A). Endocasts of Saturnalia tupiniquim (MCP-3845-PV), Plateosaurus (MB.R.5586-1), and a sauropod specimen tentatively reffered to Cetiosaurus (OUMNH J13596) in dorsal (B,C,D) and anterolateral (E,F,G) views showing the morphology of the Floccular Fossae Lobe in sauropodomorph dinosaurs. Abbreviations: fl – Floccular Fossae Lobe, ie – inner ear, 1 – Archosauriformes, 2 – Archosauria, 3 – Dinosauromorpha, 4 –Dinosauriformes, 5 – Dinosauria, 6 – Saurischia, 7 – Sauropodomorpha, 8 – Sauropoda.
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