Apatosaur fused vertebra

Real Fossil - Jurassic 150 Mya - Warm Springs Ranch, Thermopolis Wyoming
These two tailbones are fused together, but the lack of additional bone growth suggests that this particular fossil is a genetic defect - the apatosaur was born with this abnormality. This fossil represents the first reported case of a congenital malformation in a sauropod dinosaur.