Acanthopholis

***Acanthopholis*** (/ˌækənˈθɒfoʊlɪs/; meaning "spiny scales") is a genus of ankylosaurian dinosaur in the family Nodosauridae that lived during the Late Cretaceous Period of England. A single species, ***A. horrida***, exists.

Also see Edmontonia.

Around 1865 commercial fossil collector John Griffiths found some dinosaurian remains, including osteoderms, at the shoreline near Folkestone in Kent, which he sold to the metallurgist Dr. John Percy. Percy brought them to the attention of Thomas Henry Huxley, who paid Griffiths to dig up all fossils he could find at the site. Despite being hampered by the fact that it was located between the tidemarks, he managed to uncover several additional bones and parts of the body armour.

In 1867 Huxley named the genus and species *Acanthopholis horridus*. The dinosaur's generic name refers to its armour, being derived from Greek άκανθα *akantha* meaning 'spine' or 'thorn' and φόλις *pholis* meaning 'scale'. The specific name *horridus* means 'frightening' or 'rough' in Latin. Arthur Smith Woodward emended the species name to *Acanthopholis horrida* in 1890 because *pholis* is feminine.

The type specimens, cotypes GSM 109045-GSM 109058, were found in the Chalk Group, a formation itself dating to the Albian to Cenomanian stages around 100 million years ago. The specimens consist of three teeth, a basicranium, a dorsal vertebra, spikes and scutes.

In 1869 Harry Govier Seeley informally named several new species of the genus based on remains from the Cambridge Greensand: "Acanthopholis macrocercus", based on specimens **CAMSM B55570-55609**; "Acanthopholis platypus" (**CAMSM B55454-55461**); and "Acanthopholis stereocercus" (CAMSM B55558-55569). Seeley (1871) formally described *Acanthopholis platypus* as a new species, and in his 1876 description of the sauropod *Macrurosaurus semnus* he considered the metatarsals included in the *A. platypus* type material to be possibly conspecific with *Macrurosaurus*. Later, Seeley split the material of *Acanthopholis stereocercus* and based a new species of *Anoplosaurus* on part of it: *Anoplosaurus major*. He also described a new species, *Acanthopholis eucercus*, on the basis of six caudal vertebrae (**CAMSM 55552-55557**). In 1902 however Franz Nopcsa changed it into another species of *Acanthopholis*: *Acanthopholis major*. Nopcsa at the same time renamed *Anoplosaurus curtonotus* into *Acanthopholis curtonotus*. In 1879 Seeley named the genus *Syngonosaurus* based on part of the type material of "A. macrocercus". In 1956 Friedrich von Huene renamed *A. platypus* into *Macrurosaurus platypus*.

In 1999 Xabier Pereda-Superbiola and Paul M. Barrett reviewed all *Acanthopholis* material. They concluded that all species were *nomina dubia* whose syntype specimens were composites of non-diagnostic ankylosaur and ornithopod remains. For example, the metatarsals included in the syntype series of *Acanthopholis platypus* are from a sauropod, but the remaining syntypes are not. They also found two previously unpublished names which Seeley had used to label museum specimens: "Acanthopholis hughesii" indicated SMC B55463-55490 and "Acanthopholis keepingi" SMC B55491-55526. Both names were not proposed by them as new species and are nomina nuda.

*Syngonosaurus* was synonymised with *Acanthopholis* in 1999, but the genus was reinstated in a 2020 study, when *Syngonosaurus* and *Eucercosaurus* were reinterpreted as basal iguanodontians.

## Description

The armour of *Acanthopholis* consisted of oval keeled plates set almost horizontally into the skin, with long spikes protruding from the neck and shoulder area, along the spine. *Acanthopholis* was quadrupedal and herbivorous. Its size has been estimated to be in the range of 3 to 5.5 meters (10 to 18 ft) long and approximately 380 kilograms (840 lb) in weight.

## Classification

*Acanthopholis* was originally assigned to the Scelidosauridae by Huxley. In 1902 Nopcsa created a separate family Acanthopholididae. Later, he named Acanthopholinae as a subfamily. In 1928, he corrected Acanthopholididae to Acanthopholidae. Today *Acanthopholis* is considered a member of the Nodosauridae within the Ankylosauria.