From science philosophers Adrian Currie and Derek Turner at Aeon:
Both Triceratops and Torosaurus lived in what is now western North America near the end of the Cretaceous period. Torosaurus was bigger and had a longer frill on its head, which sported openings or ‘fenestral’.
The two species are considered quite distant (different genera). But
In 2010, the palaeontologists John Scannella and John Horner challenged this consensus with the so-called ‘Toroceratops’ hypothesis. They argued that Torosaurus and Triceratops were really the same kind of animal, and that the differences were just a question of the creature’s age. As individuals grew up, they got bigger, their frills got longer, and they developed holes. According to this view, a Torosaurus is just a grown-up Triceratops.
Where’s the proof? Scannella and Horner observed that we have a lot more Triceratops skeletons than Torosaurus ones, and that bone tissue analysis of the Torosaurs suggested that they were all older, mature adults. On the other hand, some of the bountiful Triceratops specimens are smaller juveniles and young adults. This raises the question: where are all the young Torosaurs? In response, Scannella and Horner conclude that the absence of baby Torosaurs is evidence that there simply weren’t any. More.
More on the idea.
The bottom line is that the history of life is a history, not a philosophy or metaphysic, and we can only really find out answers to these species questions by accumulating many more fossils in both classifications.
See also: What the fossils told us in their own words
Follow UD News at Twitter!