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Article: Inner ear morphology of diadectomorphs and seymouriamorphs (Tetrapoda) uncovered by high‐resolution x‐ray microcomputed tomography, and the origin of the amniote crown group

Palaeontology - Vol. 63 Part 1 - Cover Image
Publication: Palaeontology
Volume: 63
Part: 1
Publication Date: January 2020
Page(s): 131 154
Author(s): Jozef Klembara, Miroslav Hain, Marcello Ruta, David S Berman, Stephanie E. Pierce, and Amy C. Henrici
Addition Information

How to Cite

KLEMBARA, J., HAIN, M., RUTA, M., BERMAN, D.S., PIERCE, S.E., HENRICI, A.C. 2020. . Palaeontology, 63, 1, 131-154. DOI: /doi/10.1111/pala.12448

Author Information

  • Jozef Klembara - Department of Ecology Faculty of Natural Sciences Comenius University in Bratislava Ilkovičova 6 84215 Bratislava Slovakia
  • Miroslav Hain - Institute of Measurement Science Slovak Academy of Sciences Dúbravská cesta 9 84104 Bratislava Slovakia
  • Marcello Ruta - Joseph Banks Laboratories School of Life Sciences University of Lincoln Green Lane Lincoln LN6 7DL UK
  • David S Berman - Section of Vertebrate Paleontology Carnegie Museum of Natural History 4400 Forbes Avenue Pittsburgh PA 15213 USA
  • Stephanie E. Pierce - Department of Organismic & Evolutionary Biology, & Museum of Comparative Zoology Harvard University Cambridge MA USA
  • Amy C. Henrici - Section of Vertebrate Paleontology Carnegie Museum of Natural History 4400 Forbes Avenue Pittsburgh PA 15213 USA

Publication History

  • Issue published online: 24 December 2019
  • Manuscript Accepted: 27 May 2019
  • Manuscript Received: 17 January 2019

Funded By

Vedecká Grantová Agentúra MŠVVaŠ SR a SAV. Grant Number: 1/0228/19
Agentúra na Podporu Výskumu a Vývoja. Grant Number: 14‐0719

Online Version Hosted By

Wiley Online Library
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The origin of amniotes was a key event in vertebrate evolution, enabling tetrapods to break their ties with water and invade terrestrial environments. Two pivotal clades of early tetrapods, the diadectomorphs and the seymouriamorphs, have played an unsurpassed role in debates about the ancestry of amniotes for over a century, but their skeletal morphology has provided conflicting evidence for their affinities. Using high‐resolution X‐ray microcomputed tomography, we reveal the three‐dimensional architecture of the well preserved endosseous labyrinth of the inner ear in representative species belonging to both groups. Data from the inner ear are coded in a new cladistic matrix of stem and primitive crown amniotes. Both maximum parsimony and Bayesian inference analyses retrieve seymouriamorphs as derived non‐crown amniotes and diadectomorphs as sister group to synapsids. If confirmed, this sister group relationship invites re‐examination of character polarity near the roots of the crown amniote radiation. Major changes in the endosseous labyrinth and adjacent braincase regions are mapped across the transition from non‐amniote to amniote tetrapods and include: a ventral shift of the cochlear recess relative to the vestibule and the semicircular canals; cochlear recess (primitively housed exclusively within the opisthotic) accommodated within both the prootic and the opisthotic; development of a distinct fossa subarcuata. The inner ear of seymouriamorphs foreshadows conditions of more derived groups, whereas that of diadectomorphs shows a mosaic of plesiomorphic and apomorphic traits, some of which are unambiguously amniote‐like, including a distinct and pyramid‐like cochlear recess.

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