H. willetti is known from a single holotype specimen, BMNHB 001876 from the Wealden Group of the Isle of Wight that includes a well-preserved nearly complete skull. It was collected by Edgar W. Willett at Cuckfield, West Sussex, from the Valanginian-aged Grinstead Clay Member, of the Hastings Group, Wealden Supergroup. Willett showed the specimen to the Geological Society of London in or around 1877 or 1878, and it was then Hulke described it as a specimen of Goniopholis crassidens, an identification derived from a similar tooth form. The specimen was considered lost among the crocodyliformresearch community but was actually safely accessioned at the Booth Museum in Brighton. It was identified as "the long-lost crocodilian of Mr Willett" by Steve, "Willett’s specimen" by Salisbury et al. and "Hulke’s specimen" by Andrande et al.. It was assigned to a new species of Goniopholis, Goniopholis willetti, by Salisbury and Naish in 2011honoring its collector. A broad phylogenetic analysis of crocodyliforms published the same year by Andrande et al., found the specimen to be the sister taxon of the clade formed by Anteophthalmosuchus hooleyi and the unnamed "Dollo’s goniopholidid". Thus it was reassigned to its own genus by Buscalioni et al., creating the combinatio nova, Hulkepholis willetti. The generic namehonorsJohn Whitaker Hulke who described the specimen as belonging to Goniopholis. A second species, Hulkepholis plotos, was first described and named by A.D. Buscalioni, L. Alcalá, E. Espílez and L. Mampel in 2013. The specific name is derived from Greek mythologyπλοτός, plotos, the drifter. It is known solely from the holotype AR-1/56, a partial skeleton which consists of AR-1-2045, a nearly complete but crushed skull; AR-1-2048, 4859, 4860, three vertebrae; AR-1-2046, a rib; AR-1-2048, a metapodial; and AR-1-2049, 4861, 4862, three osteoderms. It was collected from the early Albian-aged Escucha Formation, at Santa Maria Mine located in the municipality of Ariño, Teruel Province, of Aragon, along with the closely related Anteophthalmosuchus escuchae.
Phylogeny
Goniopholis willetti was included in a phylogeneticanalysis of goniopholidids that was published soon before the specimen was redescribed. It was found to be most closely related to the clade formed by a specimen called "Dollo's goniopholidid", and "Hooley’s goniopholidid", now named Anteophthalmosuchus hooleyi. Below is a cladogram from that analysis:
