YAVERLANDIA

In 1930, Watson mentioned a partial skull cap from Yaverland Point on the Isle of Wight, noting that it most closely resembled Troodon from Alberta while also sharing traits with one of Wight's own dinosaurs. Swinton followed his lead in 1936 and referred the specimen to Vectisaurus. But when Steel (1969) concurred with Hulke (1879) and listed the latter as an iguanodontid, Galton stepped in, reclaimed the bone, named it Yaverlandia, and assigned it to Pachycephalosauria: a group of thick-headed, possibly omnivorous dinosaurs affectionately known as "headbangers".

Based on the Early Cretaceous age of its Wessex Formation home, Yaverlandia was long regarded as the oldest known pachycephalosaur, and despite being based on meagre remains, had managed to survive many pachycephalosaurian taxonomic reviews. However, aspersions were cast on its family ties in 2000 by Sullivan, who removed said skull cap — weakly domed and very thick — from Pachycephalosauria because it lacked the features that define the group. He offered no alternative identification, however, and its affinities remained shrouded in mystery until Darren Naish subjected the fossil to CT scans as part of his dissertation in 2006.

The results echoed a familiar cautionary tale. Just as the Madagascan Majungatholus was misidentified for two decades because of its thick skull roof, Yaverlandia also turned out to possess several theropod-like traits, albeit far subtler ones. Whereas Majungatholus became Majungasaurus, a large, gnarley-skulled abelisaurid, Yaverlandia is perhaps a small, feathered maniraptoran—part of the coelurosaurian radiation that includes sloth-like therizinosaurs, peculiar alvarezsaurids, wrongly accused egg-snatching oviraptorids, and modern birds. In 2011, Naish even floated the possibility that it might represent a troodontid — a delicious irony, given that Watson had likened its remains to Troodon seven decades previously, when troodontids were still thought to be pachycephalosaurs rather than theropods, due to the similarity of their teeth.

A new twist arrived in 2026 after the discovery of a second skull cap, highly similar to the holotype and representing essentially the same portion of the cranium, but more eroded and less pristine. It's close match confirmed that Yaverlandia's unusual features were real and not just artefacts of abrasion or disease, which should have been glorious news. Instead, what seemed like a blessing was a actually a curse: the strong similarity between the two specimens added nothing to our anatomical knowledge, and substantially better material will be required to determine whether Yaverlandia is a weird maniraptoran, a misidentified ornithischian, or perhaps not a dinosaur at all.