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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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Endosseous labyrinths (right side).(A) Erlikosaurus andrewsi (IGM 100/111), (B) Nothronychus mckinleyi (AZMNH-2117, portions reconstructed from the left side shown in different color), (C) Falcarius utahensis (holotype specimen, UMNH VP 15000), (D) Falcarius utahensis (referred specimen, UMNH VP 15001). From left to right in lateral, dorsal, rostral and caudal view. Abbreviations: c, cochlear duct; crc, crus communis; csc, caudal semicircular canal; csca, ampulla of the caudal semicircular canal; fc, fenestra cochleae; ed, endolymphatic duct; fv, fenestra vestibuli; lsc, lateral semicircular canal; lsca, ampulla of the lateral semicircular canal; rsc, rostral semicircular canal; rsca, ampulla of the rostral semicircular canal.
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pone-0052289-g008: Endosseous labyrinths (right side).(A) Erlikosaurus andrewsi (IGM 100/111), (B) Nothronychus mckinleyi (AZMNH-2117, portions reconstructed from the left side shown in different color), (C) Falcarius utahensis (holotype specimen, UMNH VP 15000), (D) Falcarius utahensis (referred specimen, UMNH VP 15001). From left to right in lateral, dorsal, rostral and caudal view. Abbreviations: c, cochlear duct; crc, crus communis; csc, caudal semicircular canal; csca, ampulla of the caudal semicircular canal; fc, fenestra cochleae; ed, endolymphatic duct; fv, fenestra vestibuli; lsc, lateral semicircular canal; lsca, ampulla of the lateral semicircular canal; rsc, rostral semicircular canal; rsca, ampulla of the rostral semicircular canal.

Mentions: The endosseous labyrinths were extracted for all four therizinosaurian specimens (Figure 8). The labyrinth is most complete and shows the highest level of detail in Erlikosaurus. However, due to the damage to the left side of the skull, only the right endosseous labyrinth could be reconstructed. Although the respective regions are slightly less complete and well preserved, the endosseous labyrinths of both sides were reconstructed for Nothronychus and the two specimens of Falcarius (for details see also Material and methods). Generally, the endosseous labyrinths are similar in their morphology, although there are some distinct inter- and intraspecific differences between the single specimens.


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)

Endosseous labyrinths (right side).(A) Erlikosaurus andrewsi (IGM 100/111), (B) Nothronychus mckinleyi (AZMNH-2117, portions reconstructed from the left side shown in different color), (C) Falcarius utahensis (holotype specimen, UMNH VP 15000), (D) Falcarius utahensis (referred specimen, UMNH VP 15001). From left to right in lateral, dorsal, rostral and caudal view. Abbreviations: c, cochlear duct; crc, crus communis; csc, caudal semicircular canal; csca, ampulla of the caudal semicircular canal; fc, fenestra cochleae; ed, endolymphatic duct; fv, fenestra vestibuli; lsc, lateral semicircular canal; lsca, ampulla of the lateral semicircular canal; rsc, rostral semicircular canal; rsca, ampulla of the rostral semicircular canal.
© Copyright Policy
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3526574&req=5

pone-0052289-g008: Endosseous labyrinths (right side).(A) Erlikosaurus andrewsi (IGM 100/111), (B) Nothronychus mckinleyi (AZMNH-2117, portions reconstructed from the left side shown in different color), (C) Falcarius utahensis (holotype specimen, UMNH VP 15000), (D) Falcarius utahensis (referred specimen, UMNH VP 15001). From left to right in lateral, dorsal, rostral and caudal view. Abbreviations: c, cochlear duct; crc, crus communis; csc, caudal semicircular canal; csca, ampulla of the caudal semicircular canal; fc, fenestra cochleae; ed, endolymphatic duct; fv, fenestra vestibuli; lsc, lateral semicircular canal; lsca, ampulla of the lateral semicircular canal; rsc, rostral semicircular canal; rsca, ampulla of the rostral semicircular canal.
Mentions: The endosseous labyrinths were extracted for all four therizinosaurian specimens (Figure 8). The labyrinth is most complete and shows the highest level of detail in Erlikosaurus. However, due to the damage to the left side of the skull, only the right endosseous labyrinth could be reconstructed. Although the respective regions are slightly less complete and well preserved, the endosseous labyrinths of both sides were reconstructed for Nothronychus and the two specimens of Falcarius (for details see also Material and methods). Generally, the endosseous labyrinths are similar in their morphology, although there are some distinct inter- and intraspecific differences between the single specimens.

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