Paleobiology allows us to understand the physiology and behavior of animals. This is key to analyze evolution, genetic and phylogenetic aspects, and adaptations to the environment. Here, through a microscopic study, key aspects can be known.
Paper
González, R., Cerda, I., Perez
Moreno, A., Calvo, J., Gonzalez Riga,
B. 2023. Paleobiology of Rinconsaurus caudamirus and
Muyelensaurus pecheni (Sauropoda, Titanosauria) from the Neuquen Group, Upper
Cretaceous of Argentina: inferences from long bone histology. Cretaceous
Research 153, 105682.
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abstract
Titanosauria is the most successful and diverse clade of sauropodomorph dinosaurs, with some of the largest and smallest sauropod species known to date. Rinconsaurus caudamirus and Muyelensaurus pecheni were two small-sized titanosaurs recollected from the Neuquen Group (Upper Cretaceous) of Argentina. The bone remains of both specimens include axial and appendicular elements corresponding to several individuals. These taxa have been anatomically and phylogenetically studied, but did not analyzed from paleohistological viewpoint yet. This contribution focuses on the description of the long bone histology of both species including several aspects of its paleobiology. For this, thin transverse sections were made at the diaphysis level and were analyzed under microscope. The histology of M. pecheni and R. caudamirus shows a uniform bone microstructure similar to other titanosaurs, with changes in bone tissue types being mostly related to the different life story. The major difference between the taxa is in the type of bone matrix. Whereas woven fibered bone predominates in the cortex of M. pecheni, R. caudamirus shows parallel-fibered bone. The presence of this last primary tissue is consistent with the reduced size of R. caudamirus. The long bone histology of M. pecheni resembles that of large basal neosauropods. Contrary to the reported for other noesauropods, the data obtained in this study does not reveal a correlation between the ontogenetic stage and the body size in R. caudamirus and M. pecheni. Finally, as was mentioned previously to others titanosaurs, both specimens show a high rate of secondary remodeling.
Fig. 7. Bone microstructure of the left femur of Rinconsaurus caudamirus MAU-Pv-RS-92. (A) Outer cortex showing parallel-fibered bone. Polarized light with lambda compensator. (B) Detail of a single annulus in the outer cortex. Normal transmitted light. (C) Abundant secondary osteons in the mid cortex. Polarized light with lambda compensator. (D) Remains of primary parallel-fibered bone between the secondary osteons. Polarized light with lambda compensator. (E) Inner cortex composed of dense Haversian bone tissue. Normal transmitted light. (F) Two generations of overlapping secondary osteons. Normal transmitted light. Abbreviations: an: annulus; cvc: circumferential vascular canal; pfm: parallel fibered matrix; po: primary osteon; rca: resorption cavity; so: secondary osteon. Scale bars: A, B; DeG ¼ 0.2 mm; C ¼ 0.3 mm.
