Due to the enormous size of the fossil, scientists initially believed that the Poseidonosaurus bones they discovered were from an ancient tree. Poseidonosaurus lived during the Early Cretaceous period, approximately 118-110 million years ago. When the first Poseidonosaurus fossil was discovered in the United States in 1994, experts initially thought it might be a fossilized tree because of its enormous size.
These fossils were eventually identified as vertebrae. The longest one measures 1.4 meters, meaning that the total length of this sauropod dinosaur's neck is estimated to be up to 12 meters.
Although it is long, it is slightly shorter than the 15-meter-long neck of the South China Mamenchisaurus, which may be the longest dinosaur neck ever discovered.
However, estimates of Poseidonosaurus's size may be inaccurate. Its vertebrae are often compared to those of Brachiosaurus and Brachiosaurus, which were once considered the largest known dinosaur. However, these dinosaurs are not as closely related as previously thought. Poseidonosaurus is now believed to be more closely related to Titanosaurus than to Brachiosaurus.
