Bone Histology of the Late Triassic Dinosauriform Silesaurus opolensis

Fostowicz-Frelik, L., and T. Sulej. 2009. Bone histology of Silesaurus opolensis Dzik, 2003 from the Late Triassic of Poland. Lethaia. 10.1111/j.1502-3931.2009.00179.x

Abstract- 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.


  1. I wonder how many long bone histology studies have been done across Pseudosuchia. Seems like it'd be a worthwhile project.

  2. de Ricqles et al 2003 looked at a variety of pseudosuchian archosaurs as well as the archosauriform Erythrosuchus. They found that pseudosuchians grew slower than dinosaurs and similar to crocodylomorphs; but surprisingly Erythrosuchus grew fast like dinosaurs.

  3. This is waaay late, but:

    de Ricqles et al 2008 follows up:

    I did a blog post on the subject too:

  4. When do you know you need to start with a new method of studying? I realized after I was almost close to flunking my histology paper. After that, I created thesehistology flashcards and started using many more which were available there

  5. No one wants to buy your flash cards.



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