Comparative bone microstructure of two non-mammaliaform cynodonts from the Late Triassic (Carnian) Chañares formation of Northwestern Argentina

The aim of the present contribution is to examine the bone histology of two non-mammaliaform cynodonts recovered from the Late Triassic (Carnian) Chañares Formation, at Los Chañares locality, La Rioja province, Northwestern Argentina. The taxa analysed here are the Traversodontidae Massetognathus pa...

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Bibliographic Details
Published in:Historical biology 2024-01, Vol.36 (1), p.109-119
Main Authors: Garcia Marsà, Jordi Alexis, Agnolín, Federico Lisandro, Novas, Fernando E.
Format: Article
Language:English
Subjects:
Bones
Cortical bone
Cynodontia
fossoriality
Growth patterns
Histology
histovariability
Long bone
Massetognathus
palaeohistology
Probainognathus
Triassic
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Summary:The aim of the present contribution is to examine the bone histology of two non-mammaliaform cynodonts recovered from the Late Triassic (Carnian) Chañares Formation, at Los Chañares locality, La Rioja province, Northwestern Argentina. The taxa analysed here are the Traversodontidae Massetognathus pascuali and the Probainognathidae Probainognathus jenseni, both forms known from multiple skeletons. Our osteohistological results reveal an uninterrupted growth pattern and high intraspecific histovariability in Massetognathus. On the other hand, Probainognathus presents cyclical growth, a cortex dominated by parallel-fibred bone tissue and scarce vascularisation. In spite of being derived non-mammaliaform eucynodonts, Massetognathus and Probainognathus show high growth plasticity, a feature usually regarded as plesiomorphic for cynodonts. Both taxa show a thick cortex in the long bones, a feature that could be linked to counteract the strong flexion forces during digging.
ISSN:0891-2963
1029-2381
DOI:10.1080/08912963.2022.2149332