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Home , Aristosuchus, Chondrosteosaurus, Nomen dubium, Wessex Formation

Possible b aryonychid t eeth f rom the W essex F ormation (Lower C retaceous, B arremian) of the ,

David M . Martill* and S teve Ruut

MARTILL, D . M . & HUTT, S . 1 996. Possible b aryonychid dinosaur t eeth f rom the W essex F ormation (Lower C retaceous, B arremian) o f the I sle o f W ight, England. P roceedings of the G eologists ' Association, 107, 8 1-84. Isolated, l aterally c ompressed, recurved t eeth o f theropod d inosaurs f rom the F ormation ( ) of the I sle o f W ight are d istinguished f rom o ther theropod t eeth b y t heir finely d enticulate carinae and b y lingual and l abial l ongitudinal f aceting. T hese t eeth are c omparable with t hose o f walkeri C harig & Milner 1986 and are t entatively assigned t o the e nigmatic theropod f amily B aryonychidae.

* Department ofGeology, U niversity ofPortsmouth, P ortsmouth pal 3QL. t Museum ofIsle ofWight Geology, Sandown, I sle of Wight P036 8 AF.

1. INTRODUCTION Dinosaur remains are abundant i n the clays and of the W essex F ormation, , of the southern coast o f the I sle o f W ight. England (see B enton & Spencer, 1995 for a r eview of Wealden G roup reptile l ocalities) (Fig. I). The a rea has b ecome f amous for b oth the abundance and diversity of its dinosaur fauna w hich includes the ornithopods , , and (Sues & Norman, 1 991; N orman & Weishampel, 1991), the ankylosaur (Blows, 1 987), the b rachiosaur sauropods Pelerosaurus and (Mclntosh, 199 1), a diplodocid sauropod (Charig, 1980) and t heropods. Until r ecently, t heropods f rom the I sle o fW ight w ere r epre- sented only b y isolated b ones and t eeth. Isolated t eeth h ave usually b een referred t o sp., w hile a syn- , originally thought t o b elong t o a p terosaur, and named Ornithodesmus, has b een shown to be f rom a maniraptoran theropod. possibly with affinities to the Troodontidae (Howse & Milner, 1993). Lydekker (1988) referred f ive isolated theropod tooth crowns (BMNH R21O) from the I sle of Wight to Megalosaurus dunkeri Dames, but later considered that they might be referred to Megalosaurus oweni Lydekker (Lydekker, 1890). As M. oweni is based on a right metatarsus. these teeth cannot be referred to this taxon. Additionally, M. dunkeri is based on an isolated and worn tooth from the Wealden of Germany, and should be considered as a . Bones of the pelvic region and lumbar vertebrae of a theropod from Brook, Isle of Wight were made the of pusillus (Owen), and a number of other specimens were also referred to this taxon (Lydekker, 1888), mostly without justification. A number of names were erected last century for small Isle of Wight theropods on the basis of isolated vertebrae, including Calamo- spondylus foxi Lydekker based on two cervical vertebrae

Proceedings ofthe Geologists ' Association. 107, 81-84. and Thecocoelurus daviesi (Seeley) b ased o n a n i ncomplete cervical v ertebra. Apart from the type material of Aristosuchus pusillus and Ornithodesmus c luniculus all o f the I sle o f W ight theropod material i s i nadequate for sensible generic d etermination. For a r eview o f the e arly history o f the I sle o f W ight d inosaurs and t heir c ollectors a detailed account can b e f ound i n Swinton (1936). More recently the remains o f a l arge and e xceptionally well p reserved a llosaurid skeleton h ave b een r ecovered. This specimen i s c urrently b eing prepared and i s u nder study b y one o f the authors. P reservation o f b one i n the Wessex F ormation i s o ften excellent and has b een the subject of a r ecent t aphonomic study (Clarke & Barker, 1993). The purpose of t his p aper is t o describe a n umber of iso- lated theropod teeth from the W essex Formation w hich were examined during a search for teeth. The t eeth dinosaur-bearing Wealden Group. Possible baryonychid teeth have been found at the localities arrowed.

0016-7878/96 $07·00 ©1996 Geologists' Association

82 D. M. MARTILL in question are held in the Isle of Wight Museum of Geology. Accession numbers IWCMS 3642; 5 120; 5122; 1995,207; 1995,208; 1995,209. In addition, a seventh tooth also f rom the W essex Formation of the I sle of Wight is held in the collection of the Geology D epartment of the University of P ortsmouth, accession n umber U 0P97.

2. I SLE OF W IGHT THEROPOD TEETH Two dental m orphotypes considered t o b elong t o f1esh- eating o ccur i n the W essex F ormation of the I sle of W ight. B oth m orphotypes are usually e ncountered as isolated crowns, and h ave usually suffered some d amage due e ither t o p ost-mortem effects, or, in m any cases as a result o f w ear d uring o cclusion. E ven i n s pecimens w ith post-mortem damage, d etail offine structure i s often visible as theropod t eeth are r elatively r esistant t o abrasion (Argast, Farlow, Gebet & Brinkman, 1987). The f irst m orphotype is l aterally c ompressed, recurved w ith smooth lingual and l abial sides, and has coarsely d enticulate carinae (serrations) b oth a nteriorly and p osteriorly. I n the p ast, i t has b een c ommon practice t o r efer t o t his t ooth t ype a s megalosaurid (or e ven for t hem t o b e p laced i n the g enus Megalosaurus). Indeed, historically. m any species of Megalosaurus w ere erected o n the b asis o f t eeth a lone (see Waldman, 1 974). The r ecent d iscovery o f a n a llosaurid i n the Wealden o f the I sle o f W ight w ith t his t ooth t ype s hows that such isolated t eeth can n o l onger b e p laced i n Megalosaurus w ith any c onfidence, and t his practice s hould stop u ntil i t can b e d emonstrated t hat M egalosaurus t eeth can be distinguished f rom the t eeth o f all o ther theropod genera. I t remains t o b e e stablished w hat t ype o f t eeth were p ossessed b y O rnithodesmus, the o ther I sle o f W ight theropod. The s econd t ooth m orphotype, and the m ain subject of this p aper, i s similar i n overall s hape t o t hat o f m ost theropod t eeth, but i s c haracterized b y h aving l ongitudinal fluting o n the l abial and lingual s urfaces, and b y h aving very f ine d enticles o n the anterior and p osterior carinae (Fig. 2). The s pecimens d escribed h ere are not w ell localized, but r WCMS 3 642 was f ound a t Y averland. IWCMS 5 120 was f ound a t Hanover P oint ( Fig. I).

3. D ESCRIPTION Teeth varying i n c rown h eight between 1 8 and 4 4 mm, w ith anteroposterior d imension a t the b ase o f the c rown between 8 and 2 3 m m (in the current s ample s et; n o minimum o r maximum s ize i s i nferred). C rown g ently p osteriorly flexed, labial and lingual surface o f c rown w ith l ongitudinal faceting, s ometimes i n l arge s pecimens becoming m inor carinae r ootwards ( Fig. 3). L abial and lingual surface may b e f inely rugose, e specially towards b ase o f c rown. Cross-section o val, enhanced b y p ossession o f anterior and posterior carinae. Carinae f inely d enticulate ( serrated) w ith seven t o e ight d enticles per m illimetre ( Fig. 3). R oot not known b eyond a few m illimetres b elow the c rown. & S. HUTT a b c d

Fig. 2 . Possible b aryonychid t eeth: (a) I WCMS 5 122, complete tooth c rown i n lateral v iew, x I ; (b) I WCMS 1 995/208, i ncomplete tooth c rown and r oot i n lateral v iew showing l ongitudinal r idges and faceting o f ?lingual surface, x 1 .25; (c) I WCMS 3 642, t ooth crown i n lateral v iew w ith o cclusion w ear f acets ( arrowed), x 1.8; (d) s ame t ooth a s (a) a bove i n anterior v iew showing proximal carina, x 1.5.

Root/crown boundary may b e obvious and i rregular (Fig. 2).

4. A FFINITIES Historically m any dinosaur t axa w ere b ased o n isolated teeth, a practice w hich, happily, i s d ying o ut. However, recent w ork (Farlow, B rinkman, A bler & Currie, 1 991 ) has s hown t hat theropod t eeth can b e u sed for t axonomic purposes, although w e d o not r ecommend u sing t eeth a s anything but a m inor p art o f any theropod t axon d iagnosis. Using a c ombination o f c haracters, i ncluding overall s hape, surface texture, s erration density and s ize, F arlow e t al.

DINOSAUR TEETH FROM THE ISLE OF WIGHT 83 (1991) w ere a ble t o d istinguish between the t eeth o f a number o f theropod genera. W e f ollow t his p ractice, but do not attempt t o a ssign the t eeth d escribed h ere t o any specific t axon, rather, w e m erely w ish t o p oint out t hat significant s imilarities e xist w ith b etter d iagnosed theropod taxa. A feature t hat appears t o set the I sle o f W ight t eeth a part from m ost o ther theropod t eeth i s the r emarkably f ine denticulation ( serration) o f the anterior and p osterior carinae. O nly i n Baryonyx and Saurornitholestes does the number of d enticles approach t hat of the I sle o f W ight teeth. I t is w orth n oting t hat t here i s a d ifference i n denticle density between the anterior and p osterior carinae i n Saurornitholestes (Table I) which i s not the c ase for the I sle of W ight t eeth. I n addition t o the h igh denticle c ount, the Isle o f W ight t eeth are also c haracterized b y the p ossession of l ongitudinal facets. Such a feature i s a lso reported for the teeth o f Baryonyx walkeri from the Wealden o f Surrey, England (Charig & Milner, 1986, 1990) w hich t hese workers r efer t o a s fluting. T hus the I sle o f W ight t eeth have a n overall s hape, denticle density and facets w hich are comparable w ith t hose o f Baryonyx.

5. DISCUSSION Baryonyx is k nown f rom a partial skeleton d iscovered i n a clay pit i n Surrey ( for a n account o f its d iscovery see Milner, Croucher & Charig, 1986) and i t a ttracted m edia attention because o f the s ize o f its large claws. Baryonyx proved d ifficult t o a ssign t o any theropod g roup, w hich led Charig & Milner ( 1986) t o e rect the family B aryonychidae to accommodate it. Subsequently, B uffetaut ( 1989) c om- pared Baryonyx with the giant African theropod Spinosaurus, and s uggested a possible r elationship between these two genera. Material assigned t o Spinosaurus by Taquet (1984) from the A ptian of N iger, and from the probably b asal C enomanian of Morocco, and a lso identified as Spinosaurus, is c onsidered b y C harig & Milner ( 1990)

Table 1. Table o f m easurements o f denticle ( serration) density o f selected theropod t axa, b ased o n c ounts g iven i n the l iterature o r taken f rom p hotographs

Taxon Denticles per 5 m m

Baryonyx walkeri 35 Charig & Milner, 1986, 1990 Carcharadontosaurus s aharicus 10 Deperet & Sorvnin, 1927 r aptorius 12 Chaterjee, 1978 a irelennsis 15 Cuny & Galton, 1993 Megalosaurus hesperis II Waldman, 1974 Sauronitholestes l angstoni ant. 35, p ost. 25-26 Sues, 1978 Spinosaurus a egyptiacus 0 Stromer, 1915 troodontid i ndet. 14* Barsbold, Osmolska & Kurzanov, 1987 Isle o f W ight t eeth 35

Data f rom Barsbold et ai. (1987), C harig & Milner (1990), C hatterjee (1978), C uny & Galton (1993), Deperet & Savomin (1927), Stromer (1915), Sues (1978) and Waldman (1974). * Note the t eeth oft he t roodontid d escribed b y Barsbold et ai. ( 1987) are l ess than 5 m m h igh and t his f igure is e xtrapolated.

84 D. M. MARTILL & S. I-IUTr to belong to Baryonyx. The teeth of Spinosaurus can be distinguished readily from those of Baryonyx, and indeed most (?all) other theropod teeth, by their complete lack of denticles on the carinae. Unfortunately the type material of Spinosaurus was destroyed during a bombing raid on Munich in 1944, and other isolated t eeth identified as Spinosaurus must be treated with caution (e.g. the isolated teeth figured by Bouaziz, B uffetaut, Ghanmi, Jaeger, Martin, M azin & Tong, 1988). I t i s t herefore n o longer possible to compare directly the t eeth of Baryonyx with Spinosaurus. What is clear, however, i s t hat B aryonychidae were not j ust r estricted t o Europe, or i ndeed t o the Barremian. It is therefore highly likely that baryonychid skeletal remains will tum up on the Isle of Wight.

ACKNOWLEDGEMENTS DMM would l ike t o thank the University of P ortsmouth for the use of f acilities. W e especially thank Drs A ndrew and Angela M ilner for helpful discussion, and for suggesting that w e might l ook at Baryonyx. Useful discussions were held w ith John Martin, D ina F rey, A rthur Cruickshank and Mike Barker. W e t hank N ikki Phillips for t yping the manuscript, and M r R . Branson for a ssistance w ith SEM.

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Received 2 4 M arch 1 995; revised t ypescript accepted 4 October 1 995.