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Osteohistology of the silesaurid Sacisaurus agudoensis from southern Brazil (Late Triassic) and implications for growth in early dinosaurs
- Source :
- Anais da Academia Brasileira de Ciências, Vol 91, Iss suppl 2
- Publisher :
- Academia Brasileira de Ciências.
-
Abstract
- Abstract: The non-dinosaurian dinosauriform silesaurids are the closest relatives of crown-group dinosaurs and are thus, important for understanding the origins of that group. Here, we describe the limb bone histology of the Late Triassic silesaurid Sacisaurus agudoensis from the Candelária Sequence of the Santa Maria Supersequence, Rio Grande do Sul state, Brazil. The sampled bones comprise eight femora and one fibula from different individuals. The microscopic analysis of all elements reveals uninterrupted fibrolamellar bone tissue indicating rapid growth. A transition to slower growing peripheral parallel-fibered bone tissue in some individuals indicates a decrease in growth rate, suggesting ontogenetic variation within the sample. The osteohistology of Sacisaurus agudoensis is similar to that of other silesaurids and supports previous hypotheses that rapid growth was attained early in the dinosauromorph lineage. However, silesaurids lack the complex vascular arrangements seen in saurischian dinosaurs. Instead, they exhibit predominantly longitudinally-oriented primary osteons with few or no anastomoses, similar to those of some small early ornithischian dinosaurs. This simpler vascular pattern is common to all silesaurids studied to date and indicates relatively slower growth rates compared to most Dinosauria.
- Subjects :
- Archosauria
bone microstructure
dinosauriform
fibrolamellar bone
growth rates
Science
Subjects
Details
- Language :
- English
- ISSN :
- 00013765 and 16782690
- Volume :
- 91
- Database :
- Directory of Open Access Journals
- Journal :
- Anais da Academia Brasileira de Ciências
- Publication Type :
- Academic Journal
- Accession number :
- edsdoj.ba290ef4afea42ad8695cc8e00a3fb08
- Document Type :
- article
- Full Text :
- https://doi.org/10.1590/0001-3765201920180643