| Bull. nat. Hist. Mus. Lond. (Geol.) 52(2): 115-118 
Issued 28 November 1996 
The first known femur of Hylaeosaurus 
armatus and re-identification of ornithopod 
material in The Natural History Museum, 
London 
PAUL M. BARRETT 
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ 
SYNOPSIS. 
The first known femur of the British Lower Cretaceous ornithopod dinosaur Hylaeosaurus armatus Mantell, 1833 
is described. The status of Camptosaurus valdensis (Lydekker, 1889) is reviewed, and it is suggested that it might be senior 
synonym of Valdosaurus canaliculatus (Galton 1975). 
| 
| INTRODUCTION 
|The purpose of this brief paper is to report and describe the first 
recognised femur of the nodosaurid ankylosaur Hylaeosaurus 
_armatus Mantell 1833, and to clarify the taxonomic position of 
|several ornithopod specimens.The status of Camptosaurus valdensis 
‘(Lydekker 1889) is also reviewed and it is provisionally placed in 
synonymy with Valdosaurus canaliculatus (Galton 1975). Unless 
|otherwise stated, all of the specimens described are of Wealden 
(Lower Cretaceous) age and are from the Isle of Wight, England. 
They belong to the Fox Collection housed in the Department of 
Palaeontology, The Natural History Museum, London (NHM; regis- 
‘ter numbers prefixed BMNH in this paper). 
SYSTEMATIC PALAEONTOLOGY 
| 
DINOSAURIA Owen 1841 
ORNITHISCHIA Seeley 1887 
THYREOPHORA Nopsca 1915, sensu Sereno 1986 
ANKYLOSAURIA Osborn 1923 
Family NODOSAURIDAE Marsh 1890 
Genus HYLAEOSAURUS Mantell 1833a 
TYPE AND ONLY SPECIES. Hylaeosaurus armatus Mantell 1833b; 
Lower Cretaceous (Upper Valanginian), East and West Sussex, 
Southern England. 
Hylaeosaurus armatus Mantell 1833 Fig. 1 
1833b Hylaeosaurus armatus Mantell: 328. 
HOLOTYPE. BMNH R3775, the anterior part of a skeleton embed- 
ded in a block of matrix. 
HORIZON AND LOCALITY. Hastings Beds (Lower Wealden), Upper 
Valanginian, Lower Cretaceous (Rawson et al 1978). Tilgate Forest, 
Cuckfield, West Sussex, England. 
REFERRED MATERIAL. As listed by Pereda-Suberbiola (1993) and 
MNH R604k (now registered as BMNH R12555), the distal 
ortion of a right femur. 
9° The Natural History Museum, 1996 
DESCRIPTION AND COMPARISON. The distal portion of a large right 
femur (Fig. la), BMNH R604k (Dawson Collection), from the 
Wealden, near Hastings, East Sussex, may represent the first recog- 
nised femur of Hylaeosaurus armatus. 
This specimen was originally identified as /guanodon sp.' but was 
later referred to as a large individual of Hypsilophodon foxii (Huxley) 
by Molnar & Galton (1986). However, the femur is much more 
massive than that of H. foxii, and the absence of a marked anterior 
intercondylar groove suggests that it is not referable to Jguanodon. 
The absence of ridges running up the femoral shaft from the condyles 
supports the view that R604k is not referable to either of these 
genera. There is a marked posterior intercondylar groove and the 
lateral and medial condyles extend equal distances posteriorly from 
the femoral shaft. The lateral condyle is much more massive than the 
medial one, and there is a distinct ‘step’ between the medial condyle 
and the medial extremity of the femur (Fig. 1b). The femur bears a 
strong resemblance to that of the Oxfordian nodosaur Cryptodraco 
eumerus (Galton 1983) which also displays a ‘step’ between the 
medial condyle and the medial border of the femur. BMNH R604k 
can be distinguished from the femora of the other known Wealden 
nodosaur Polacanthus foxii (BMNH R175) by a number of features. 
For example, Polacanthus shows no ‘step’ medial to the medial 
condyle, and the medial condyle is more massive in Polacanthus 
than in BMNH R604k. It seems unlikely, therefore, that BMNH 
R604k is referable to Polacanthus. It is suggested that BMNH 
R604k is not ornithopod as previously supposed but thyreophoran, 
and the locality and the horizon from which the specimen was 
recovered suggests that it is referable to Hylaeosaurus. The rela- 
tively small size of the femur (only 83mm across the distal end) 
suggests that it belonged to a juvenile (W. Blows, pers. comm.). 
Unfortunately, due to the fragmentary nature of the specimen, this 
assignment can only be tentative. Nonetheless, the femur provides 
valuable information on the alleged synonymy of Hylaeosaurus and 
Polacanthus (Coombs 1971, Blows 1987, Coombs & Maryanska 
1990, Pereda-Suberbiola 1991, 1993). 
Coombs (1971) and Coombs & Maryanska (1990) suggested that 
'Lydekker (1888) listed a number of specimens as BMNH R604a-e. These registered 
numbers include a number of theropod, ornithopod and ankylosaur remains, all of 
which come from the Wadhurst Clay near Hastings and are part of the Dawson 
Collection. The femur in question is labelled BMNH R604k. There is no record of this 
number in either Lydekker (1888) or in the accessions catalogues of the Natural History 
Museum (S. Chapman pers. comm.). The specimen label identified the femur as 
Iguanodon sp. from the Wadhurst Clay near Hastings. 
