Bone histology of Silesaurus opolensis from the Late Triassic of PolandDzik, 2003
Version of Record online: 14 JUL 2009
© 2009 The Authors, Journal compilation © 2009 The Lethaia Foundation
Volume 43, Issue 2, pages 137–148, June 2010
How to Cite
FOSTOWICZ-FRELIK, Ł. and SULEJ, T. (2010), Bone histology of Silesaurus opolensis from the Late Triassic of Poland. Lethaia, 43: 137–148. doi: 10.1111/j.1502-3931.2009.00179.x
- Issue online: 4 MAY 2010
- Version of Record online: 14 JUL 2009
- manuscript received on 14/7/2008; manuscript accepted on 20/03/2009.
Fostowicz-Frelik, Ł. & Sulej, T. 2009: Bone histology of Silesaurus opolensisDzik, 2003 from the Late Triassic of Poland. Lethaia, Vol. 43, pp. 137–148.
The phylogenetic relationships of Silesaurus opolensis have been the subject of intense debate since its discovery. Silesaurus possesses some features characteristic of ornithischian dinosaurs, such as the presence of a beak at the front of the lower jaw, yet it lacks a number of important femoral and dental synapomorphies of Dinosauria. The microstructure of the long bones (femur, tibia and metatarsal) and ribs of this species reveals a relatively intensive rate of growth, comparable with that seen in small dinosaurs and the gracile crocodylomorph Terrestrisuchus. Cortical bone formed mainly by periosteal tissue with fibro-lamellar matrix (in older specimens parallel fibred) shows very little secondary remodelling and only in one specimen (large tibia ZPAL Ab III/1885) few lines of arrested growth are present in the outermost cortex. The vascularization is relatively dense, mainly longitudinal and ceases towards the periphery, forming almost avascular parallel fibred bone at the bone surface. This indicates maturation and significant decrease in the growth ratio in mature specimens of S. opolensis. The delicate trabeculae exhibit cores formed by the primary cancellous tissue lined with lamellar endosteal bone. The rather intense growth of S. opolensis implies a relatively high metabolic rate. Moreover, evidence from the fibro-lamellar tissue, predominant in the cortex, suggests that this kind of rapid bone deposition could be more typical of Archosauria than previously assumed, a prerequisite for the evolution of the very fast growth rates observed in large ornithischians, sauropods and large theropods. □Archosauria, Bone histology, Dinosauriformes, Late Triassic, Silesaurus opolensis.