Vrije Universiteit Brussel

Cases of pathological bone growth in Isanosaurus and () Jentgen, Benjamin Paul C; Stein, Koen; Fischer, Valentin

DOI: 10.13140/RG.2.2.10914.27840

Publication date: 2018

Document Version: Final published version

Link to publication

Citation for published version (APA): Jentgen, B. P. C., Stein, K., & Fischer, V. (2018). Cases of pathological bone growth in Isanosaurus and Spinophorosaurus (Sauropoda). Poster session presented at 5th International Palaeontological Congress, Paris, France. https://doi.org/10.13140/RG.2.2.10914.27840

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Download date: 29. Sep. 2021 Jentgen-Ceschino B.1,*, Stein K.2 & Fischer V.1 *Corresponding author. e-mail : [email protected]

1: EDDyLab, University of Liège, Belgium 2: AMGC, Vrije Universiteit of Brussel, Belgium

Abstract

The histology of the long bone of sauropods among Sauropoda. Its outermost position within the more internally or externally. This contrasts with the appears uniform and conservative along the cortex raises questions, because such a rapidly other dinosaurian taxa affected by RFB which Sauropoda evolutionary tree. One of the main apposited bone tissue would rather be expected in contains no secondary osteon in this bone tissue. aspects of their bone histology is to exhibit a the inner cortex (corresponding to an early juvenile The individual of Spinophorosaurus represents in Fibrolamellar Complex (FLC) with circumferential ontogenetic stage). Our thorough histological Sauropoda the first occurrence of RFB buried in the vascularization in the cortex of their long bones. analysis of these specimens reveals some highly outer cortex followed by a recovery of a ‘normal' FLC However, we report Radial Fibrolamellar bone (RFB) vascularized RFB yielding densely packed plump after this event meaning this individual survived for in the outer cortex of the humeri of a young adult osteocyte lacunae that can even obscure the some time after its phase of accelerated growth. This Isanosaurus (Histological Ontogenetic Stage - HOS - surrounding bone in both transverse and longitudinal sequence of widely distinct modes of bone 8) and an adult Spinophorosaurus (HOS 12). RFB is sections. This osteocyte pattern is restricted to the apposition suggests that these specimens are regarded as a fast-growing bone tissue and has been RFB. Bone remodelling is more expressed in this pathological. documented in a few dinosaurian taxa, but never cortical layer with denser secondary osteons than

Pathological Radial Fibrolamellar Bone (RFB): growth impulse and precocious remodelling

Sampling by core drilling of 2 humeri: [1] • CH8-66 (Isanosaurus, Nam Phong Fm., Late of Thailand ) Some say growth’s painful [2] Suddenly so fast, so odd • 2.38a (Spinophorosaurus, ‘Argiles de l’Irhazer’, Lower/Middle of Niger ) That its nature’s doubtful When the pulse’s over There’s a spiny sauropod Main histological features: Whose bones are treasure to discover • HOS 8 (young adult Isanosaurus) – 12 (adult Spinophorosaurus) • FLC in the inner to the outer cortex and RFB in the outer cortex: accelerated growing phase during slowdown in growth. Spinophorosaurus recovers a ‘normal’ FLC after this event • Biomechanics: RFB triggers precocious remodelling (microstructural weaknesses) 2.38a

0,5 mm

God dammit! I twisted my arm! 1. Drill Again!

100,0 mm 2. Core

3. Thin sections Avascular ‘normal’ CH8-66 bone cap

Outer RFB

‘Normal’ FLC

1,0 mm

Big, dense packs of plump osteocyte lacunae

0,5 mm

RFB Cortex

Periosteal surface

Radial vascular canal

[3]

0,5 mm

Weakness points: remodelling Conclusions Acknowledgements

1. The RFB apposited in Isanosaurus and Spinophorosaurus humeri are the first cases reported within Sauropoda 2. The RFB apposition during slower growth stages and coinciding with precocious remodelling is probably pathological in nature. The humerus 2.38a of Spinophorosaurus is the first case of survival of a RFB growth impulse in Sauropoda

[1] Buffetaut E. et al. (2000). Nature 407, 72-74. [2] Remes K. et al. (2009). PLoS ONE 4, e6924. doi: 10.1371/journal.pone.0006924 [3] de Margerie E. et al. (2004). The Journal of Experimental Biology 207, 869-879. doi: 10.1242/jeb.00841