Paleobiology of the basal sauropodomorph Mussaurus patagonicus inferred from its long bone histology

CERDA, IGNACIO; DIEGO POL; ALEJANDRO OTERO; ANUSUYA CHINSAMY

PALAEONTOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022

0031-0239

The biology and growth of basal sauropodomorphs are known from histological studies performed in relatively few taxa, usually from scarce individuals. To increase the knowledge about basal sauropodomorph bone histology and its paleobiologic implications, we performed a detailed histological study of long bones from an ontogenetic series of Mussaurus patagonicus, a basal sauropodomorph form the early Jurassic of Argentina. Twenty long bones, including humerii, femora and fibulae, obtained from thirteen individuals of variable body size were sampled for histological analysis. In general terms, the cortical bone is formed by a well vascularized fibrolamellar and parallel fibered bone. With the exception of the smaller individuals, cyclical growth marks (CGMs) are well recorded in all the specimens, but their number and relative position is strongly variable. Mussaurus exhibits strongly variation regarding relative growth rates, with individuals growing much faster than others. Such variation affects the size of the adult individuals, which results in a poor correlation between the body size and the age/ontogenetic stage for this taxon. These discrepancies appear to be related with sexual dimorphism and/or developmental plasticity. Intraspecific variation is also recorded with regard to the growth strategies, which can vary from cyclical, as other basal sauropodomorphs, to rather continuous, as reported in sauropods. Regarding sexual maturity onset, it appears to be reached between 23 and 31 years, which is strongly delayed in comparison with the reported for other basal sauropodomorphs, but more comparable with derived sauropods. Somatic maturity attainment appears to be reached from 14 years after the onset of sexual maturity.