Torosaurus was proven to be merely a mature version of Triceratops, making the names synonymous.
The relationship between Triceratops and Torosaurus remains scientifically contentious. In 2010, John Scannella and Jack Horner proposed they were the same species at different life stages, with Torosaurus representing an older, larger Triceratops. However, subsequent studies in 2011-2015 by other paleontologists (including Longrich and Field) argued they are distinct species based on horn morphology, frill structure, and other skeletal features. Recent phylogenetic analyses lean toward separate valid species, but the debate persists. This exemplifies how paleontological taxonomy can shift as new data accumulates.