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The endocranial anatomy of therizinosauria and its implications for sensory and cognitive function.

Lautenschlager S, Rayfield EJ, Altangerel P, Zanno LE, Witmer LM - PLoS ONE (2012)

Bottom Line: This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory.The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon.In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.

View Article: PubMed Central - PubMed

Affiliation: School of Earth Sciences, University of Bristol, Bristol, United Kingdom. glzsl@bristol.ac.uk

ABSTRACT

Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare.

Methodology/principal findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon.

Conclusion/significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.

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Cranial endocast and braincase of Nothronychus mckinleyi (AZMNH-2117).In (A) and (B) in left lateral, (C) caudal, (D) dorsal, and (E) ventral view. Bone in (B) rendered transparent. Abbreviations: car, cerebral carotid artery canal; cvcm, caudal middle cerebral vein; fl, floccular lobe; lab, endosseous labyrinth; pfo, pituitary (hypophyseal) fossa; V1, ophthalmic branch of the trigeminal nerve canal; V2, maxillary branch of the trigeminal nerve canal; V3, mandibular branch of the trigeminal nerve canal; VI, abducens nerve canal; VII, facial nerve canal; IX–XI, shared canal for the glossopharyngeal, vagus and spinal accessory nerve; XII, hypoglossal nerve canal.
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pone-0052289-g005: Cranial endocast and braincase of Nothronychus mckinleyi (AZMNH-2117).In (A) and (B) in left lateral, (C) caudal, (D) dorsal, and (E) ventral view. Bone in (B) rendered transparent. Abbreviations: car, cerebral carotid artery canal; cvcm, caudal middle cerebral vein; fl, floccular lobe; lab, endosseous labyrinth; pfo, pituitary (hypophyseal) fossa; V1, ophthalmic branch of the trigeminal nerve canal; V2, maxillary branch of the trigeminal nerve canal; V3, mandibular branch of the trigeminal nerve canal; VI, abducens nerve canal; VII, facial nerve canal; IX–XI, shared canal for the glossopharyngeal, vagus and spinal accessory nerve; XII, hypoglossal nerve canal.

Mentions: The cerebellum is not as clearly demarcated in the endocast as is the cerebrum, but it appears to be relatively high and narrow in Erlikosaurus (Figure 3A, B), as well as in the other three therizinosaurian specimens (Figure 5, 6, 7). It is situated in the space between the endosseous labyrinths. The height, however, cannot be exactly determined, as a dural venous sinus covered the dorsal part of the endocast, obscuring cerebellar details. A moderately developed dural peak is present in all the therizinosaurian endocasts. Ventrally, the outline of the pons is indicated by an expanded area, which merges with the medulla oblongata. The latter is considerably enlarged and as wide as the cerebellum at its widest expansion, where it exits the braincase through the foramen magnum. Whereas the medulla oblongata is slightly wider than high in Erlikosaurus and Nothronychus (Figure 5E), it is slightly higher than wide in the two endocasts of Falcarius (Figure 6C, 7C).


The endocranial anatomy of therizinosauria and its implications for sensory and cognitive function.

Lautenschlager S, Rayfield EJ, Altangerel P, Zanno LE, Witmer LM - PLoS ONE (2012)

Cranial endocast and braincase of Nothronychus mckinleyi (AZMNH-2117).In (A) and (B) in left lateral, (C) caudal, (D) dorsal, and (E) ventral view. Bone in (B) rendered transparent. Abbreviations: car, cerebral carotid artery canal; cvcm, caudal middle cerebral vein; fl, floccular lobe; lab, endosseous labyrinth; pfo, pituitary (hypophyseal) fossa; V1, ophthalmic branch of the trigeminal nerve canal; V2, maxillary branch of the trigeminal nerve canal; V3, mandibular branch of the trigeminal nerve canal; VI, abducens nerve canal; VII, facial nerve canal; IX–XI, shared canal for the glossopharyngeal, vagus and spinal accessory nerve; XII, hypoglossal nerve canal.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3526574&req=5

pone-0052289-g005: Cranial endocast and braincase of Nothronychus mckinleyi (AZMNH-2117).In (A) and (B) in left lateral, (C) caudal, (D) dorsal, and (E) ventral view. Bone in (B) rendered transparent. Abbreviations: car, cerebral carotid artery canal; cvcm, caudal middle cerebral vein; fl, floccular lobe; lab, endosseous labyrinth; pfo, pituitary (hypophyseal) fossa; V1, ophthalmic branch of the trigeminal nerve canal; V2, maxillary branch of the trigeminal nerve canal; V3, mandibular branch of the trigeminal nerve canal; VI, abducens nerve canal; VII, facial nerve canal; IX–XI, shared canal for the glossopharyngeal, vagus and spinal accessory nerve; XII, hypoglossal nerve canal.
Mentions: The cerebellum is not as clearly demarcated in the endocast as is the cerebrum, but it appears to be relatively high and narrow in Erlikosaurus (Figure 3A, B), as well as in the other three therizinosaurian specimens (Figure 5, 6, 7). It is situated in the space between the endosseous labyrinths. The height, however, cannot be exactly determined, as a dural venous sinus covered the dorsal part of the endocast, obscuring cerebellar details. A moderately developed dural peak is present in all the therizinosaurian endocasts. Ventrally, the outline of the pons is indicated by an expanded area, which merges with the medulla oblongata. The latter is considerably enlarged and as wide as the cerebellum at its widest expansion, where it exits the braincase through the foramen magnum. Whereas the medulla oblongata is slightly wider than high in Erlikosaurus and Nothronychus (Figure 5E), it is slightly higher than wide in the two endocasts of Falcarius (Figure 6C, 7C).

Bottom Line: This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory.The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon.In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.

View Article: PubMed Central - PubMed

Affiliation: School of Earth Sciences, University of Bristol, Bristol, United Kingdom. glzsl@bristol.ac.uk

ABSTRACT

Background: Therizinosauria is one of the most enigmatic and peculiar clades among theropod dinosaurs, exhibiting an unusual suite of characters, such as lanceolate teeth, a rostral rhamphotheca, long manual claws, and a wide, opisthopubic pelvis. This specialized anatomy has been associated with a shift in dietary preferences and an adaptation to herbivory. Despite a large number of discoveries in recent years, the fossil record for Therizinosauria is still relatively poor, and cranial remains are particularly rare.

Methodology/principal findings: Based on computed tomographic (CT) scanning of the nearly complete and articulated skull of Erlikosaurus andrewsi, as well as partial braincases of two other therizinosaurian taxa, the endocranial anatomy is reconstructed and described. The wider phylogenetic range of the described specimens permits the evaluation of sensory and cognitive capabilities of Therizinosauria in an evolutionary context. The endocranial anatomy reveals a mosaic of plesiomorphic and derived characters in therizinosaurians. The anatomy of the olfactory apparatus and the endosseous labyrinth suggests that olfaction, hearing, and equilibrium were well-developed in therizinosaurians and might have affected or benefited from an enlarged telencephalon.

Conclusion/significance: This study presents the first appraisal of the evolution of endocranial anatomy and sensory adaptations in Therizinosauria. Despite their phylogenetically basal position among maniraptoran dinosaurs, therizinosaurians had developed the neural pathways for a well developed sensory repertoire. In particular olfaction and hearing may have played an important role in foraging, predator evasion, and/or social complexity.

Show MeSH
Related in: MedlinePlus