doi:10.1144/0016-76492007-154 2008; v. 165; p. 613-623 Journal of the Geological Society

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Journal of the Geological Society, London, Vol. 165, 2008, pp. 613–623. Printed in Great Britain.

613

Review

Dinosaurs of Great Britain and the role of the Geological Society of London in

their discovery: Ornithischia

DARREN NAISH & DAVID M. MARTILL

Palaeobiology Research Group, School of Earth and Environmental Sciences, University of Portsmouth,

Portsmouth PO1 3QL, UK (e-mail: eotyrannus@gmail.com)

Abstract: Completing our survey of British non-avian dinosaurs, we here review the ornithischians of Britain.

Heterodontosaurids are present in the Lower Cretaceous Lulworth Formation of Dorset, and a few earlier

possible records imply a long presence in the region of this clade. Britain’s thyreophoran record is rich and

includes the earliest well-represented taxon, Scelidosaurus, as well as Middle Jurassic stegosaurs and

ankylosaurs including a reasonably good Cretaceous record of polacanthids and nodosaurids. Cretaceous

stegosaurs are known only from fragmentary remains, but the proposal that stegosaurs were present as early as

the Rhaetian is rejected. Among British iguanodontian ornithopods, the possible dryosaurid Callovosaurus is the

oldest global record whereas the proposed synonymy of Cumnoria with Camptosaurus requires confirmation.

Iguanodon has become a taxonomic dumping ground for assorted iguanodontians and is in need of revision:

most of the British species referred to this genus are almost certainly not closely allied to the neotype species

I. bernissartensis and require new generic names. Fragmentary remains suggest the early presence of

hadrosaurids in Britain. The only British record of Marginocephalia, the Wessex Formation skull roof named

Yaverlandia bitholus, appears not to belong to this clade but seems to be from a maniraptoran theropod.

Together with their saurischian relatives, ornithischian dinosaurs

dominated terrestrial life during the Jurassic and Cretaceous

periods. Characterized by an opisthopubic pelvis, a predentary

bone and other distinctive characters, they include the familiar

stegosaurs, ankylosaurs, hadrosaurs, pachycephalosaurs and cer-

atopsians. Their feeding mechanics, evolutionary interactions

with plants, and evolution of armour and diverse cranial

structures have proved highly fertile areas of research. The first

ornithischian to be described was the ornithopod Iguanodon,

based on isolated teeth from the Hastings Beds Group of East

Sussex (Mantell 1825), and the second was the ankylosaur

Hylaeosaurus from the same strata (Mantell 1833). The term

‘ornithischian’, referring to a pelvic girdle that superficially

resembles that of birds, was published by Seeley (1888).

Although ornithischians originated in the Triassic (Butler et al.

2007), their fossils from this time are rare and many alleged

Triassic ornithischians have recently been reinterpreted (Irmis et

al. 2006). The British ornithischian record has recently been

extended to the Upper Triassic (Rhaetian), where two fragmen-

tary bones have been referred to Stegosauria (Galton 2005).

Convincing remains of thyreophorans are well documented from

the Hettangian and Sinemurian of Dorset, where partial skeletons

of Scelidosaurus, sometimes with skin preserved, have been

known since the 1860s (Owen 1861). Isolated elements and rare

partial skeletons of ornithischians have been reported from

marine strata in the Bathonian, Callovian, Oxfordian and Kim-

meridgian of central and eastern England. However, the most

substantial remains come from the Lower Cretaceous Hastings

Beds, Weald Clay and Wealden groups, where near-complete and

partial skeletons of the ankylosaurs Hylaeosaurus and Pola-

canthus and the ornithopods Hypsilophodon, Valdosaurus, Man-

tellisaurus and Iguanodon have been recovered. The youngest

non-avian British dinosaurs include ornithischian taxa from the

Albian–Cenomanian Lower Chalk, Folkestone Beds, Gault Clay

and Cambridge Greensand: among them are highly fragmentary

ankylosaurs and hadrosaurids.

In a previous paper (Naish & Martill 2007), we reviewed the

fossil record, taxonomy and phylogenetic relationships of the

saurischian dinosaurs from the British Mesozoic. Here, we

review British ornithischian dinosaurs. As discussed previously

(Naish & Martill 2007, p. 496), many names coined for British

dinosaur taxa are no longer considered adequate in terms of

establishing taxonomic validity (supplementary information is

available online at http://www.geolsoc.org.uk/SUP18267), mean-

ing that approximately 54% of named British dinosaur taxa are

nomina dubia. In view of inconsistencies in the literature, we

have used the original spellings for specific names, although this

results in an apparent inconsistency within our own text. A

number of British ornithischians have been incorrectly allocated

to a genus (e.g. most species referred to Iguanodon) and, in most

cases, it is the type species alone that should be regarded as

being correctly associated with the generic name. All other

designations to generic level should be assumed to be historical

artefacts and, following convention, we use quotation marks.

Heterodontosauridae

Heterodontosaurids were small, gracile ornithischians, best

known for the caniniform teeth and elongate hands present in

most genera. Conventionally regarded as ornithopods (Sereno

1986; Norman et al. 2004), they may be basal ornithischians

outside of Genasauria (Butler et al. 2008) or the sister-taxon to

Marginocephalia (Xu et al. 2006). Most heterodontosaurids are

from the Lower Jurassic of South Africa but Echinodon becklesii

Owen, 1861, probably from the Berriasian Warbarrow Tout

Member of the Lulworth Formation of Durlston Bay, Dorset,

appears to belong to this group (Norman & Barrett 2002) (Fig.

1). Teeth like those of E. becklesii are known from the Bathonian

Forest Marble of Kirtlington and the Tithonian Portland Stone of

Wiltshire (Norman & Barrett 2002). Small, conical osteoderms

from the Purbeck Limestone Group, dubbed ‘granicones’, were

considered referable to E. becklesii when this taxon was regarded

as a possible thyreophoran, but are now known to be osteoderms

from solemydid turtles (Barrett et al. 2002). Heterodontosaurids

have recently been reported from the Lower Cretaceous Camar-

illas Formation of Spain (Sanchez-Hernandez et al. 2007) and

this group may prove to have been more widespread in the Early

Cretaceous in Europe than realized so far.

Thyreophora

Thyreophora is the armoured ornithischian clade: in addition to

the familiar ankylosaurs and stegosaurs it includes several basal

forms from the Lower Jurassic. Conventionally regarded as one

of these basal forms, Scelidosaurus harrisonii Owen, 1861 is one

of Britain’s most historically significant ornithischians. First

described from an incomplete hindlimb and an associated skull

and skeleton from a different individual (Owen 1861), it is from

the Sinemurian Charmouth Mudstone Formation of Charmouth,

Dorset. The hindlimb on which Owen (1861) based the generic

name proved to belong to a tetanuran theropod (Newman 1968)

and, accordingly, Charig & Newman (1992) proposed that the

skull and skeleton be regarded as the lectotype. Owen made little

of the fact that S. harrisonii provided support for his view of

dinosaurs as comparatively heavy-limbed quadrupeds (Norman

2000, 2001).

Owen (1861) also described other elements (dorsal centrum,

phalanges and right hind limb bones) as belonging to a juvenile

S. harrisonii. This identification was doubted by Newman

(1968), who proposed that these were from a ‘hypsilophodontid’.

Another specimen suggested to be a juvenile S. harrisonii (Rixon

1968; Charig 1972), BMNH R6704, was thought by Thulborn

(1974, 1977) to represent a different taxon, probably allied to

basal ornithischians such as Lesothosaurus. Coombs et al. (1990)

Fig. 1. (a) Dentition of Echinodon becklesii paralectotype specimen BMNH 48215b in lingual view. Scale bar represents 10 mm. (b) Skeletal

reconstruction of the Lower Jurassic heterodontosaurid Heterodontosaurus tucki. Echinodon would have been similar overall to this taxon, although

different in its details. Diagram by kind courtesy of J. Headden. Scale bar represents 10 cm.

D. NAISH & D. M. MARTILL614

also regarded it as a distinct taxon, albeit a thyreophoran.

However, Galton (1975) reaffirmed the identification of both

controversial specimens as S. harrisonii.

Some unpublished S. harrisonii individuals sport curving

squamosal horns and thorn-like spikes running in rows along the

limbs (Naish & Martill 2007, fig. 1). Possibly this is evidence of

sexual dimorphism. The concept of S. harrisonii as a basal

thyreophoran was challenged by Carpenter (2001), who argued

that character evidence better places S. harrisonii as the sister-

taxon to Ankylosauria (the S. harrisonii + Ankylosauria clade

being termed Ankylosauromorpha), but this has not been

supported in a recent global analysis of ornithischian phylogeny

(Butler et al. 2008). Reports of S. harrisonii from the Rhaetian

Westbury Formation of Shepton Mallet, Somerset (Storrs 1994),

Lower Jurassic Kayenta Formation of Arizona, USA (Padian

1989) and Lufeng Formation of Yunnan, China (Lucas 1996) are

probably erroneous (Norman et al. 2007). A detailed, modern

description of S. harrisonii is still lacking.

Following S. harrisonii, thyreophorans are unknown from

Britain for perhaps 20 Ma or more. A few fossils might help fill

this gap, however. Clark (2001) described a thyreophoran from the

Bajocian of the Isle of Skye, known only from a proximal radius

and ulna. The rugose, inflated olecranon process suggests an

ankylosaurian identity more than a stegosaurian one. Hoffstetter

(1957) suggested that two armour plates from the Bathonian

Chipping Norton Formation of Stow-on-the-Wold, Gloucester-

shire, might be ankylosaurian, but Galton (1985) referred these to

the stegosaur Lexovisaurus.

Ankylosauria

Indisputable ankylosaurs do not appear in the British fossil

record until the Callovian. An incomplete lower jaw from the

Peterbrough Member of the Oxford Clay Formation of Fletton,

Cambridgeshire, was named Sarcolestes leedsi Lydekker, 1893.

In its rostrally continuous tooth row and proportionally small

predentary S. leedsi resembles nodosaurids (Galton 1983a) and it

was regarded as the sister-taxon to Nodosaurinae by Sereno

(1998). However, Vickaryous et al. (2004) proposed that S. leedsi

should be regarded as Ankylosauria incertae sedis. This poses a

problem for Sereno’s (1998) phylogenetic definition of Nodo-

saurinae, as S. leedsi was employed as a specifier. Three isolated

osteoderms from the Oxford Clay Formation were suggested by

Galton (1994) to belong to S. leedsi.

A younger ankylosaur, Cryptosaurus eumerus Seeley, 1869, is

based on a right femur from the Ampthill Clay of Great

Gransden, Cambridgeshire. A dorsal vertebra from the Oxford

Clay of Weymouth referred to the taxon was reidentified as

probably belonging to a theropod (Galton 1983b). Although

Lydekker (1889) argued that Cryptosaurus was preoccupied

(prompting the replacement name Cryptodraco Lydekker), he

was incorrect (B. Creisler, pers. comm.). Galton (1980a, 1983b)

regarded the femur as most like that of Hoplitosaurus, a North

American ankylosaur regarded as a polacanthid by those workers

who recognize this group (Kirkland 1998a; Carpenter 2001) and,

on the basis of the prominent trochanters, proposed that Crypto-

saurus may have been facultatively bipedal (Galton 1983b). The

latter idea has not been accepted by other workers. Cryptosaurus

lacks autapomorphies and should be regarded as Ankylosauria

indet.

Priodontognathus phillipsii (Seeley, 1869), known only from a

maxilla and originally described as Iguanodon phillipsii, was

reinterpreted by Galton (1980b) as a nodosaurid. The specimen

exhibits unusual teeth combining denticulate cingula and bowl-

like lingual depressions (Barrett 2001), and its recent consign-

ment to the status of nomen dubium (Vickaryous et al. 2004) is

probably unjust. It has yet to be determined whether Priodontog-

nathus is from the Upper Jurassic of Yorkshire or the Lower

Cretaceous of Sussex.

Far better represented are the Wealden ankylosaurs Hylaeo-

saurus armatus Mantell, 1833 and Polacanthus Owen in Anon.,

1865. Though once considered synonymous, they are clearly

distinct. Hylaeosaurus is from the Grinstead Clay Formation of

East Sussex (Mantell 1833) with a referred specimen from West

Sussex (Mantell 1841). The holotype consists of an articulated

anterior portion of a skeleton, still with cervical and scapular

armour in position, and possibly incorporating cranial material

(Mantell 1833; Pereda-Suberbiola 1993). Mechanical and acid

preparation has been used on this specimen, and more informa-

tion will be forthcoming.

Polacanthus is represented by two species. P. foxii Owen in

Anon., 1865 was described for a partial skeleton from the

Wessex Formation whereas P. rudgwickensis Blows, 1996 is from

the Barremian Upper Weald Clay Formation of Rudgwick, West

Sussex (Hulke 1881; Blows 1987, 1996; Pereda-Suberbiola 1993,

1994). Cranial material referred to P. foxii includes a partial

neurocranium, a possible angular, and a tooth (Blows 1987;

Norman & Faiers 1996; Naish & Martill 2001a). The characters

that differentiate P. foxii from P. rudgwickensis are not entirely

satisfactory, and unpublished specimens from the Isle of Wight

and East Sussex are intermediate between the two. In addition to

its presence in the Wessex Formation, P. foxii has been reported

from the Vectis Formation and from a Lower Greensand Forma-

tion exposure between Humble Point and Pinhay Bay, Devon

(Blows 1996). The latter record, initially reported as being from

Charmouth, Dorset, lacks characters that allow its identification

beyond Ankylosauria. Specimens from Spain and the USA have

been referred to Polacanthus, and, in addition to its occurrence

in the Weald, Hylaeosaurus has been reported from Germany,

France and the Isle of Wight, although all of these additional

records are probably erroneous (Naish & Martill 2001a). The

affinities of Hylaeosaurus and Polacanthus remain uncertain:

although often regarded as basal nodosaurids, both have been

regarded as part of a Polacanthidae clade (Kirkland 1998a;

Carpenter 2001).

Numerous ankylosaur remains from the Albian–Cenomanian

Lower Chalk, Folkestone Beds, Gault Clay and Cambridge

Greensand, described as Anoplosaurus major Seeley, 1879 and

five species of the supposed nodosaurid Acanthopholis Huxley,

1867, were reviewed by Pereda Suberbiola & Barrett (1999) and

shown to be based on non-diagnostic ankylosaurian material,

some of which had been combined with ornithopod and sauropod

material. Only one ankylosaur from these units, Anoplosaurus

curtonotus Seeley, 1879 from the Upper Gault Clay or Cam-

bridge Greensand near Reach (Cambridgeshire), is diagnosable

(Pereda Suberbiola & Barrett 1999). In its low number of sacral

vertebrae, rostral extent of its dentary tooth row and other

features, Anoplosaurus appears to be a basal nodosaurid. The

absence of dermal armour in the holotype probably reflects

juvenile status.

Stegosauria

Britain has a reasonably good stegosaur record that includes

some of the geologically oldest and youngest specimens in the

world, as well as the first stegosaur to be recognized historically.

The latter, a partial lower jaw named Regnosaurus northamptoni

Mantell, 1848 from the Berriasian–Valanginian Hastings Beds

BRITISH DINOSAURS 615

Group (the exact horizon is unknown, but the specimen was most

probably from the Grinstead Clay Formation) of Cuckfield, East

Sussex, was originally referred to Iguanodon and not recognized

as stegosaurian until recently (Olshevsky 1993; Barrett &

Upchurch 1995). Unlike stegosaurid stegosaurs (Barrett &

Upchurch 1995; Maidment et al. 2006), Regnosaurus lacks a

lateral lamina obscuring the dentary tooth row from view, and

shares two detailed features of the dentary with the most basal

stegosaur, Huayangosaurus from the Middle Jurassic of China.

Although this suggests that archaic stegosaurs survived into the

Early Cretaceous of Europe (Fig. 2), we should be cautious in

basing so much on lower jaw characters alone, given the paucity

of stegosaur cranial material. Most recently, Regnosaurus has

been regarded as a nomen dubium unclassifiable beyond Stego-

sauria (Galton & Upchurch 2004). Isolated elements from the

Hastings Beds Group, Weald Clay Group and Wessex Formation,

including an incomplete vertebra, armour plates and a pubis,

have been suggested to be stegosaurian (Galton 1981; Blows

2001; Naish & Martill 2001a) although not without controversy

or later reidentification (Galton 1985). Craterosaurus pottonensis

Seeley, 1874, from the Aptian Potton Sands of Potton, Bed-

fordshire, might be reworked from the Hastings Beds Group and

thus synonymous with Regnosaurus. A depression between the

prezygapophyses appears unique to Craterosaurus and it has

been regarded as a valid stegosaurid (Galton 1981; Galton &

Upchurch 2004).

Britain’s oldest undoubted stegosaurs are among the oldest

stegosaur body fossils in the world: they comprise teeth and

postcranial elements from the Bathonian Sharp’s Hill Formation

of Oxfordshire and Chipping Norton Formation of Gloucester-

shire (Galton & Powell 1983; Metcalf & Walker 1994; Benton &

Spencer 1995). Possible stegosaur spikes have been reported

from the Aalenian–Bajocian Inferior Oolite Formation of Brad-

ford Abbas, Dorset (Benton & Spencer 1995).

Galton (2005) argued that two partial columnar bone segments

from the Rhaetian Westbury Formation of Aust Cliff, Avon,

represent femora of Late Triassic stegosaurs. Interpreted as

femora, these bones would have been c. 1 m long when complete

and would have belonged to animals comparable in size with

Stegosaurus (total length 7–9 m). The columnar bone shape and

presence of a thin cortex and of extensive cancellous bone and/or

trabeculae were used to support a stegosaurian identity (Galton

2005). The idea that giant stegosaurs were present as early as the

Late Triassic is surprising and based on scant evidence. Butler et

al. (2006) and Norman et al. (2007) argued that these specimens

cannot be identified beyond Reptilia indet. Irmis et al. (2006)

argued that the specimens lacked features allowing identification,

that the details on internal structure employed by Galton are of

no use in taxonomic identification, and that the specimens should

be identified as Tetrapoda indet. We agree with these reapprai-

sals.

The best known British stegosaurs are the basal stegosaurid

Dacentrurus armatus (Owen, 1875) from the Kimmeridge Clay

Formation of Swindon and the stegosaurine stegosaurid Lexovi-

saurus durobrivensis (Hulke, 1887) from the Callovian Oxford

Clay Formation of Fletton. Both species were originally de-

scribed as belonging to Omosaurus Owen, 1875, a name

preoccupied by a North American phytosaur. To rectify this,

Dacentrurus Lucas, 1902 was coined for ‘O.’ armatus, and

Lexovisaurus Hoffstetter, 1957 erected for ‘O.’ durobrivensis.

Much material from Dorset, Wiltshire, Oxfordshire, Northamp-

tonshire and Cambridgeshire has been referred to these taxa

(Galton & Powell 1983; Galton 1985) and several other names

are regarded as probable junior synonyms. Among these is

‘Omosaurus’ phillipsi Seeley, 1893, based on a femur from the

Oxfordian Corallian Oolite Formation of Slingsby, North York-

shire (Galton 1983c), and deliberately given the same specific

name as Priodontognathus phillipsii (although note that Seeley

Fig. 2. Skeletal reconstructions of selected

British stegosaur taxa portrayed in their

phylogenetic context. (a) Regnosaurus

northamptoni, a possible basal stegosaur

(based only on a partial lower jaw).

(b) Dacentrurus armatus, a basal

stegosaurid. (c) Lexovisaurus durobrivensis,

a stegosaurine stegosaurid. Not to scale.

Diagrams courtesy of T. L. Ford.

D. NAISH & D. M. MARTILL616

(1893) spelt the specific name differently) because Seeley

thought it would prove synonymous with it! D. armatus was a

large stegosaur exceeding 7 m in total length: the femur of the

holotype is over 1200 mm long (Galton & Boine 1980) and

therefore similar in size to that of Stegosaurus.

Ornithopoda

The name Ornithopoda is today restricted to the clade that

incorporates the hadrosaurid Edmontosaurus and all taxa closer

to it than to the marginocephalian Triceratops (Norman et al.

2004). Basal ornithopods were small, bipedal cursors but larger

size and more robust proportions were evolved by members of

the clade Iguanodontia.

Fragmentary remains indicate the presence of basal ornitho-

pods within the British fossil record. A premaxillary tooth from

Stonesfield was identified as that of a basal ornithopod (Galton

1975), and a dentary tooth from the Kimmeridge Clay of

Weymouth, accessioned to the UCMP (as UCMP 46911), was

identified as cf. Bugenasaura (Galton 1999). Even allowing for

phylogenies indicating that basal ornithopods such as Bugen-

asaura originated in the Middle Jurassic (Weishampel et al.

2003), this is surprising given that Bugenasaura is a Maastrich-

tian North American taxon. The provenance of this specimen is

dubious, and it is likely that it did not originate in Dorset (Martill

et al. 2006).

The best known British ornithopod (after Iguanodon) is

Hypsilophodon foxii Huxley, 1869, one of the first small

ornithischians to be recognized. First identified as a juvenile

Iguanodon, Huxley (1869, 1870) showed it to be a distinct taxon.

Numerous specimens are known from the Hypsilophodon Bed

near the top of the Wessex Formation, as well as from the Vectis

Formation (Galton 1969, 1974, 1989). Reports of Hypsilophodon

sp. from East Sussex (Weishampel 1990) are erroneous. Mis-

interpreted by some 19th and 20th century workers as scansorial,

H. foxii was actually a terrestrial cursor (Galton 1971a, b, 1974).

Ornithischians similar to H. foxii persisted throughout most of

the Mesozoic and, until recently, were all united in a ‘family’

Hypsilophodontidae (e.g. Sereno 1986; Weishampel & Heinrich

1992). Phylogenetic studies indicate that this grouping is artifi-

cial (Weishampel et al. 2003; Norman et al. 2004; Butler et al.

2008).

Basal members of the ornithopod clade Iguanodontia were

superficially similar to H. foxii and were long classified with

them in ‘Hypsilophodontidae’. Among these are the dryosaurids:

gracile cursors with narrow feet lacking a hallux. Valdosaurus

canaliculatus (Galton 1975) from the Wessex Formation is

similar to Dryosaurus and was initially named as a species of

this genus (Galton 1975). V. canaliculatus was named for femora

but numerous other elements have been referred to it (Galton &

Taquet 1982; Barrett 1996; Blows 1998; Naish & Martill 2001b).

Although the Wessex Formation hindlimb elements can be

reliably referred to this species, the same cannot be said for the

others. Some of the referred material is from the Hastings Beds

Group of Heathfield and Cuckfield in East Sussex and its referral

to V. canaliculatus is questionable. Barrett (1996) suggested that

‘Camptosaurus’ valdensis Lydekker, 1889, based on an incom-

plete left femur presumed to be from the Wessex Formation,

might be a senior synonym of V. canaliculatus.

An alleged dryosaurid tibia has been reported from the

Callovian Oxford Clay of Fletton, Cambridgeshire (Galton

1977), but it cannot be reliably allocated to Dryosauridae and

should be regarded as Ornithopoda indet. A left femur, also from

the Oxford Clay of Fletton, was described as Camptosaurus

leedsi Lydekker, 1889 and, although suggested at times to be part

of Dryosauridae (Gilmore 1909; Galton 1974), was given its own

genus, Callovosaurus Galton, 1980, in Camptosauridae. Signifi-

cant in being the earliest reported iguanodontian, it has most

recently been argued to be a valid dryosaurid (Ruiz-Omenaca et

al. 2007).

Better represented is the partial camptosaurid from the

Kimmeridge Clay of Cumnor, Oxfordshire, named Iguanodon

prestwichii Hulke, 1880 but later awarded the generic name

Cumnoria Seeley, 1888. Although it has been argued that this

taxon is referable to Camptosaurus (Lydekker 1889; Galton

1980c; Galton & Powell 1980), derived characters shared by the

Kimmeridge Clay taxon and Camptosaurus have yet to be

identified and the characters used to allocate it to Camptosaurus

are unconvincing, consisting almost entirely of plesiomorphies.

Furthermore, some of the similarities that have been used to

support referral of Cumnoria to Camptosaurus (e.g. small

antorbital fenestra) are now known not to occur in the latter

taxon: the cranial material typically illustrated for Camptosaurus

actually belongs to another iguanodontian, Theiophytalia (Brill

& Carpenter 2007).

Iguanodon

Iguanodon Mantell, 1825 was first described from teeth from the

Hastings Beds Group of Cuckfield (Mantell 1825) but is today

regarded as ranging from Berriasian to Albian, and to contain six

British species (Norman 2004). Although the species-level

taxonomy of Iguanodon is regarded as non-controversial, it

requires revision. There has been considerable confusion as to

which unit yielded Mantell’s original material: Topley (1875)

stated that the ‘Tilgate Grit’ that yielded Mantell’s original

specimens was part of the Wadhurst Clay Formation, Norman

(1987) regarded the Upper Tunbridge Wells Sand Formation as

the source of Mantell’s specimens, whereas Blows (1998)

claimed that the fossils were collected from the Grinstead Clay

Formation. Although Mantell acquired specimens from various

horizons of the Hastings Beds Group, Mantell’s ‘Tilgate Grit’

was part of the Grinstead Clay Formation (Radley 2004).

Mantell’s type material of Iguanodon was later named Iguano-

don anglicus Holl, 1829 (originally I. anglicum). Unfortunately,

it is non-diagnostic so, to save the generic name, Charig &

Chapman (1998) proposed that the Belgian species Iguanodon

bernissartensis be made the new type species, and the ICZN

ruled in favour of this proposal. Although I. bernissartensis is

the earliest named valid species referred to the genus, and the

one best associated with it, it is substantially different from other

species referred to Iguanodon, and from the Hastings Beds

Group material.

The oldest species referred to Iguanodon, ‘I.’ hoggii Owen,

1874 from the Berriasian Lulworth Formation of Swanage,

Dorset, was argued by Norman & Barrett (2002) to belong to

Camptosaurus and was renamed C. hoggii. Other elements from

Dorset have been referred to C. hoggii, as have bones from

Buckinghamshire and from the Berriasian Speeton Clay Forma-

tion of Yorkshire (Norman & Barrett 2002).

In addition to I. anglicus, three species from the Hastings Beds

Group have been referred to Iguanodon. Older than I. bernissar-

tensis and more archaic, it is doubtful that they are congeneric

with this species (Lydekker 1888). Vertebrae and pelvic and

hindlimb bones, representing a large species from the Wadhurst

Clay Formation of Hastings, were named ‘I.’ dawsoni Lydekker,

1888. Several additional specimens were referred by Blows

(1998) to ‘I.’ dawsoni, with the best of them being BMNH

BRITISH DINOSAURS 617

R3788 (Fig. 3a) from Old Roar Quarry, St. Leonards-on-Sea,

East Sussex. This referral is almost certainly incorrect and the

true affinities of this specimen remain to be determined.

‘I.’ fittoni Lydekker, 1889, also from the Wadhurst Clay

Formation, is characterized by tall neural spines on its posterior

dorsal vertebrae (Norman 1987). It is incorrectly listed as being

based on ‘3 partial skulls and jaws’ by Norman (2004, p. 416).

‘I.’ fittoni has been argued to be synonymous with ‘I.’ hollingto-

niensis Lydekker, 1889 (Blows 1998; Norman 2004), also of the

Wadhurst Clay Formation.

Better known than these taxa are those from the Barremian

and Aptian. ‘I.’ atherfieldensis Hooley, 1925 was named for a

partial skeleton, with skull, from the lower Aptian part of the

Vectis Formation of the Isle of Wight (Fig. 4c). This species is

highly distinct from I. bernissartensis and the two group apart in

some phylogenetic studies (Norman 2002, 2004). Accordingly,

‘I.’ atherfieldensis was removed from Iguanodon by Paul (2007)

and made the type of a new genus, Mantellisaurus. One of the

most famous British specimens referred to Iguanodon, the

‘Maidstone specimen’ or ‘Mantel-piece’, discovered in 1834 and

Fig. 3. (a) The iguanodontian specimen

BMNH R3788 from the Wadhurst Clay

Formation of Old Roar Quarry, St.

Leonards-on-Sea, East Sussex, questionably

referred to Iguanodon dawsoni. This

specimen is of historical interest in being

supposedly involved in the Piltdown Man

saga. Scale bar is 30 cm. (b) Life

restoration of the iguanodontian Iguanodon

bernissartensis.

D. NAISH & D. M. MARTILL618

obtained by William H. Bensted, is also one of the youngest,

coming from the Aptian Lower Greensand Formation. Long

thought (incorrectly) to be the type for Iguanodon mantelli von

Meyer, 1832, it was referred by Norman (1993) to M. atherfiel-

densis. Two other iguanodontians, Vectisaurus valdensis Hulke,

1879 and Sphenospondylus gracilis Lydekker, 1888, have been

argued to be synonyms of M. atherfieldensis (Norman 1990).

Alhough this is likely to be correct it cannot be demonstrated,

and these taxa are best regarded as Iguanodontia indet.

Large, robust iguanodontians from the Wessex Formation and

Fig. 4. Map of SE England showing key iguanodontian specimens and their discovery sites. (a) The near-complete tail and partial pelvis DORK G18,

discovered in 1895 at the bottom of a well in Capel. (b) Skeleton reconstruction, after Norman (1993), of the ‘Mantel-piece’ from near Maidstone.

(c) Holotype skull of Mantellisaurus atherfieldensis, after Hooley (1925), from Atherfield Point. (d) Holotype ilium of I. seelyi, after Hulke (1882), from

Brook Chine. (e) BMNH R10147, a pelvis probably referable to M. atherfieldensis, from Ockley. (f) BMNH R3788, a pelvis and associated vertebrae

from St. Leonards-on-Sea (see Fig. 3a). (g) Holotype pelvis of I. dawsoni, after Lydekker (1888), from Hastings.

BRITISH DINOSAURS 619

Barremian Upper Weald Clay Formation have been referred to

I. bernissartensis (Naish & Martill 2001b; Norman 2004) and are

similar to Belgian specimens. However, I. seelyi Hulke, 1882,

named after Charles Seely (and not H. G. Seeley), was coined

for notably robust elements from a large Isle of Wight iguano-

dontian (Fig. 4d). Although it has been assumed that I. seelyi is a

junior synonym of I. bernissartensis, the two differ in the form

of the ilium (Hulke 1882) and this synonymy should be regarded

as provisional. Largely overlooked has been the conditional

proposal by Delair (1966) that Weald Clay material named

Streptospondylus major Owen, 1842 should be recognized as a

new iguanodontian taxon, I. major. Delair (1966) speculated that

I. major differed in enough subtle details from I. bernissartensis

to be considered distinct.

It seems that Iguanodon is the ornithopod version of Cetio-

saurus and Megalosaurus: a taxonomic dumping ground for any

iguanodontian remains that are not clearly referable to any other

named taxon. The status and phylogenetic relationships of many

of the referred species and specimens require further study.

Possible hadrosaurids

‘Iguanodon’ hillii Newton, 1892, the youngest British species

referred to this genus, has been suggested to be a hadrosaurid

(Horner et al. 2004) but is better regarded as Iguanodontia indet.

Based on only a partial maxillary tooth, it was thought by Head

(1998) to be indistinguishable from the basal iguanodontian

condition, but this is probably incorrect as the tooth is highly

derived. A second proposed British hadrosaurid is ‘Trachodon’

cantabrigiensis (not cantabrigensis, as spelt by Newton (1892))

Lydekker, 1888, a nomen dubium based on a single tooth from

the Cambridge Greensand. Although ‘T.’ cantabrigiensis is

hadrosaurid-like and has been regarded as a member of Hadro-

sauridae (Benton & Spencer 1995; Kirkland 1998b; Horner et al.

2004), Head (1998) argued that the absence of further British

hadrosaurid material, the variation observed within the tooth

morphology of iguanodontian taxa, and the geographical isola-

tion of the British archipelago from the Aptian on rendered this

identification tenuous. Further remains are needed for the

presence of hadrosaurids in Britain to be verified, and for now

‘T.’ cantabrigiensis remains a tantalizing enigma.

Marginocephalia

Marginocephalians (the pachycephalosaurs and ceratopsians) are

restricted to North America and Asia, with only a few dubious

records from elsewhere. Yaverlandia bitholus Galton, 1971, from

the Wessex Formation of the Isle of Wight and based on an

incomplete skull roof, has been regarded as a pachycephalosaur

(Galton 1971c). In lacking characters present in all definite

pachycephalosaurs it has been interpreted by some as one of the

most basal members of the group (Wall & Galton 1979; Sues

1980; Galton & Taquet 1982; Williamson & Carr 2002). How-

ever, the features that have led to its identification as a

pachycephalosaur (domed frontals, interfrontal fusion) are pre-

sent only in derived, dome-skulled members of the clade, and

consequently some workers have regarded it as a derived form

(Sues & Galton 1987; Maryanska 1990; Sereno 2000; Naish &

Martill 2001c). Furthermore, Yaverlandia differs in numerous

detailed features from definite pachycephalosaurs, leading several

workers to doubts its inclusion within the group (Giffin 1989;

Sullivan 2000, 2003, 2005). Restudy by Naish (in preparation),

incorporating computerized tomography scanning, has shown

that Yaverlandia appears, surprisingly, to be a maniraptoran

theropod. This reidentification expunges marginocephalians from

the British fossil record.

Discussion

This contribution concludes our review of the British dinosaur

assemblage (see Naish & Martill 2007). Although it is clear that

Britain is home to a rich and diverse dinosaur assemblage, we

also note again the huge contribution to the subject made by the

Geological Society of London. The well-known and well-repre-

sented British ornithischians Lexovisaurus durobrivensis, Hypsi-

lophodon foxii, Cumnoria prestwichii and Mantellisaurus

atherfieldensis were all described in the Quarterly Journal of the

Geological Society of London, and, among the more obscure

forms, Sarcolestes leedsi, Anoplosaurus curtonotus, Cratero-

saurus pottonensis and ‘Iguanodon’ dawsoni (and others) were

too.

The absence from the British Upper Triassic and Lower

Jurassic of basal ornithischians resembling Lesothosaurus,

Eocursor and members of Heterodontosauridae suggests that

Britain was not important in the early history of the clade.

However, the presence of the relict heterodontosaurid Echinodon

in Berriasian strata of Dorset shows that this mostly Early

Jurassic group survived into the Early Cretaceous. If teeth from

the Bathonian of Kirtlington are correctly identified as those of

heterodontosaurids (Norman & Barrett 2002), it would appear

that British members of the clade were not Cretaceous novelties

that invaded the region from elsewhere, but were in fact present

here throughout the Jurassic.

Britain’s oldest reported ornithischian is the thyreophoran

Scelidosaurus, one of the first dinosaurs to be described from

good, associated remains. Excellent articulated specimens mean

that this taxon has the potential to be one of the most thoroughly

described and best understood of all thyreophorans, but a

comprehensive modern analysis is still lacking. The British

record of ankylosaurs and stegosaurs is reasonably good, with a

handful of taxa, including Polacanthus, Hylaeosaurus and

Dacentrurus, represented by articulated remains.

Britain’s record of iguanodontians is particularly rich. Callovo-

saurus leedsi is the oldest global record of this clade. If correctly

identified by Ruiz-Omenaca et al. (2007) as a dryosaurid, the

Callovian age of Callovosaurus means that the ghost lineages of

many ornithopod taxa (including Hypsilophodon, Rhabdodonti-

dae and Tenontosaurus) are even longer than previously proposed

(Weishampel et al. 2003). The systematics and phylogenetic

relationships of species and specimens referred to Iguanodon

would appear to be a fertile area of further research, with

surprisingly few specimens having been adequately described. It

remains to be determined with certainty that robust iguanodon-

tians from the Wealden Group and/or Weald Clay Group are

referable to Iguanodon bernissartensis, the type species of the

genus, and several species referred to Iguanodon are almost

certainly not congeneric with I. bernissartensis.

Finally, marginocephalians (until recently thought present in

Britain because of Yaverlandia bitholus from the Wessex Forma-

tion) are absent from the British record.

For data, discussion and opinion, we thank P. Barrett, R. Butler, P. Galton,

J. Kirkland, M. Simpson, G. Paul and R. Sullivan. We thank M. Benton

and E. Buffetaut for their reviews of the manuscript. We thank

J. Headden for the heterodontosaurid reconstruction, T. Ford for the

stegosaur reconstructions, and J. Owen (Natural History Museum,

London; NHM) for use of images of NHM specimens. For access to

specimens we thank S. Chapman and A. Milner (NHM), S. Hutt and

D. NAISH & D. M. MARTILL620

M. Munt (Isle of Wight County Museum Service) and J. Cooper (Booth

Museum of Natural History, Brighton). We thank R. Strachan and A.

Hills for editorial support.

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Received 29 October 2007; revised typescript accepted 11 November 2007.

Scientific editing by Rob Strachan

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