Seis-ing up the Super- Morrison formation sauropods.

Area of Science:

• Paleontology
• Vertebrate Paleontology
• Bone Histology

Background:

• The Morrison Formation hosts giant sauropods, Diplodocus hallorum and Supersaurus vivianae, notable for their extreme body size.
• Ongoing discussions question whether these rare, large specimens represent senescent individuals or simply large-bodied taxa.

Purpose of the Study:

• To determine the maturational status of the holotype of Diplodocus hallorum and a specimen of Supersaurus vivianae.
• To investigate the ecological and biological significance of extreme body size in Morrison Formation sauropods.

Main Methods:

• Osteohistological analysis of bone samples from D. hallorum (NMMNH P-25079) and S. vivianae (WDC DMJ-021).
• Age-determination and maturational assessments using established retrocalculation methods.

Main Results:

• Both sampled specimens, D. hallorum and S. vivianae, were found to be skeletally mature at the time of death.
• Retrocalculated age for D. hallorum suggests a maximum lifespan of 60 years; S. vivianae exceeded typical age determination limits due to advanced maturity.

Conclusions:

• The rarity of giant sauropods in the Morrison Formation is more plausibly explained by their mature status rather than them being aberrant taxa.
• These findings contribute to understanding body size trends and limits in sauropod dinosaurs.