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Early Cretaceous Lizards from the Okurodani Formation of Japan
EARLY CRETACEOUS LIZARDS FROM THE O K U R O D A N I FORMATION OF JAPAN SUSAN E. EVANS & MAKOTO MANABE EVANS S.E. & MANABE M. 1999. Early Cretaceous Lizards from the Okurodani Formation of Japan. [L6zards du Cr6tac6 inf6rieur de la Formation Okurodani, Japon]. GEOBIOS, 32, 6: 889-899. Villeurbanne, le 31.12.1999. Manuscrit d6pos6 le 24.07.1998; accept6 d6finitivement le 20.11.1998. ABSTRACT - The Early Cretaceous Okurodani Formation of Gifu Prefecture, Central Honshu, Japan, is yielding an assemblage of small freshwater and terrestrial vertebrates which represent some of the oldest specimens of their kind from Japan. Although rare, at least two types of lizards - probably more - have been recovered. The most common form, described here under the name Sakurasaurus shokawensis nov. gen. et sp., is a robust scincomorph with distinctive sculptured frontals and a heterodont dentition in which the anterior teeth are tapering and recurred while the posterior teeth are blunt and striated. Parsimony analysis places it provisionally as a basal scincomorph. Other taxa are represented by isolated elements, including dentaries, maxillae, and some heavily sculptured skull roofing bones which may be anguimorph. This Japanese lizard assemblage differs from roughly contemporaneous assemblages in other parts of the world and thus contributes to our knowledge of Early Cretaceous lizard diversity in general, and to our understanding of the evolution of Asian lizard assemblages. KEYWORDS: LIZARDS, EARLY CRETACEOUS, JAPAN, SCINCOMORPHA, NEW GENUS. RI~SUMI~ - Les gisements du Cr6tac6 inf6rieur (Formation Okurodani) de Gifu, Honshu central, Japon, ont livr6 une faune de petits animaux terrestres et d'eau douce, dont certains sont les plus anciens repr6sentants de leur groupe connus au Japon. Les 16zards sont rares, mais deux formes au moins sont pr6sentes, et probablement davantage. La forme la plus courante, d6crite ici sous le nora de Sakurasaurus shokawnsis nov. gen. et sp., est un 16zard scincomorphe de type robuste avec des frontaux ornement6s et une denture h6t6rodonte. Les dents ant6rieures sont aigu~s et recourb6es; les dents post6rieures sont 6mouss6es et stri6es. L'analyse cladistique situe provisoirement ce taxon h la base des scincomorphes. Les autres 16zards sont repr6sent6s par des ossements isol6s: dentaires, maxillaires et quelques 616ments du toit cr~nien fortement sculpt6s; il s'agit probablement de 16zards anguimorphes. Cet ensemble de 16zards du Japon est diff6rent des ensembles plus ou moins contemporains connus ailleurs dans le monde; il constitue donc une contribution importante h notre connaissance de la diversit6 des 16zards du Cr6tac6 inf6rieur, ainsi qu'~ notre compr6hension de leur 6volution en Asie. MOTS-CLI~S: LI~ZARDS, CRI~TACI~ INFI~RIEUR, JAPON, SCINCOMORPHA, NOUVEAU GENRE.
INTRODUCTION T h e E a r l y C r e t a c e o u s r e p r e s e n t s a k e y period in the t r a n s i t i o n b e t w e e n t h e e s s e n t i a l l y archaic lizard f a u n a s of the J u r a s s i c (e.g. p a r a m a c e l l o d i d s , b a v a r i s a u r s , a r d e o s a u r s , E v a n s 1993) a n d the m o r e m o d e r n a s s e m b l a g e s of t h e L a t e C r e t a c e o u s (e.g. varanoids, a g a m i d s , teiids, Alifanov 1993; Gao & H o u 1995). E a r l y C r e t a c e o u s lizard a s s e m b l a g e s r e m a i n r e l a t i v e l y r a r e b u t are c u r r e n t l y k n o w n f r o m Europe; North, S o u t h a n d C e n t r a l America; Africa; a n d Asia. T h e L a t e C r e t a c e o u s record of lizards in Asia is v e r y good, largely as a r e s u l t of m a n y y e a r s of collecting in C h i n a a n d Mongolia (Gao & H o u 1995). By contrast, the E a r l y Cretaceous record of Asia is limited to f r a g m e n t a r y m a t e r i a l f r o m K a z a k h s t a n (Gao & Nessov 1998; Nessov 1997), Mongolia (Albian, Alifanov 1989a,b,
1993) a n d p r o b a b l y China, if the deposits yielding Yabeinosaurus (Endo & S h i k a m a 1942) are of b a s a l C r e t a c e o u s ( ? B e r r i a s i a n age, Yang et al. 1986) as g e n e r a l l y thought. E a r l y C r e t a c e o u s lizard fossils h a v e n e v e r previously b e e n recorded f r o m J a p a n . H e r e we describe a n a s s e m b l a g e of f r a g m e n t a r y lizard r e m a i n s from the E a r l y C r e t a c e o u s O k u r o d a n i F o r m a t i o n , Tetori Group, of C e n t r a l H o n s h u , J a p a n . GEOLOGY T h e s p e c i m e n s described h e r e w e r e r e c o v e r e d f r o m a bone-bed horizon in t h e K o b u d a n i Valley, S h o k a w a village, Gifu P r e f e c t u r e . T h e locality, d e s i g n a t e d K 0 2 by its finder, Mr Ikoi S h i b a t a , b u t listed s i m p l y as Locality 2 by H a s e g a w a et al.
890 (1995, p. 38), has yielded more t h a n 800 vertebrate fossils (Evans et al. 1998), as well as invertebrates and plants. The Jurassic-Cretaceous (Bathonian-Albian) Tetori Group outcrops in Central Japan (Ishikawa, Fukui, Gifu and Toyama Prefectures, of Central Japan; see Azuma & Tomida 1995; Manabe & Hasegawa 1995, for review). Traditionally (e.g., Maeda 1961; Azuma & Tomida 1995), the Tetori Group has been divided into three parts - the lower Kuzuryu subgroup (Bajocian to Oxfordian in age), the Itoshiro subgroup (Kimmeridgian to Berriasian), and the upper Akaiwa subgroup (Valanginian to Albian). The KO2 bone-bed horizon is in the Okurodani Formation which forms the upper part of the Itoshiro subgroup (Matsukawa et al. 1996). This would suggest a Berriasian age (135-140 Ma, Harland et al. 1990; 144-137 Ma, Gradsten et al. 1995) for the KO2 assemblage. Fission track and K-Ar analysis of several tuff layers in the Okurodani and Bessantani Formations have given an age of 140-120 Ma (Gifu-Ken Dinosaur Fossil Research Committee 1993), although there may be problems with younger intrusions. More recently, new work in the area has identified further tuff bands both above and below the bone-bed horizon (Nicholas, in press). New radiometric dating of these should provide a tighter constraint on the age of the locality, but at present a basal Cretaceous age seems most likely for the KO2 assemblage. The bone-bed matrix is a dark grey silty-sandstone. The productive horizon is characterised by a basal layer of plant macrofossils, overlain by a concentration of shell debris and bones, and then by rarer articulated specimens (turtles, choristoderes); dinosaur teeth are found scattered throughout. Almost all of the specimens are preserved in 3-D, with relatively little crushing, and they are little abraded, suggesting deposition under relatively low energy conditions (Cook et al. 1998). The most common vertebrates are aquatic taxa - fish, turtles, choristoderes, and KO2 clearly represents a predominantly freshwater assemblage, with rarer terrestrial elements. Previous work suggests t h a t the Late Jurassic Tetori Group sediments were deposited in a narrow marine basin between the land masses of the Sino-Korean continent to the North West, and an active Jurassic accretionary prism to the South East (Faure & Charvet 1987; Cluzel & Cadet 1992; Otsuki 1992; Takami & Itaya 1996; Isozaki 1996; Nicholas, in press). By the Early Cretaceous, a broad coastal plain had developed, with wide meandering river systems flowing northwards into the basin. Recent geological work (Nicholas, in press) has demonstrated t h a t one such river flowed through the Kobudani Valley, and the KO2
bone bed was probably deposited in one of a network of stagnant pools or "ox-bow" lakes, high in organic matter and choked with silt. MATERIAL
The lizard m a t e r i a l from the Okurodani Formation at Shokawa comprises some thirteen specimens including jaw and cranial elements, a vertebra and a pelvis, representing two or more distinct taxa. Most of the material was collected over a period of several years (1990-1995) by a dedicated group of amateur collectors, principally Mr Ikoi Shibata. Much of Mr Shibata's collection, including the material described here, has been formally deposited in the Visitor's Centre of the Izumi Board of Education, Izumi, F u k u i Prefecture, Japan and all those specimens carry the prefix IBEF VP. Additional lizard specimens have been found and prepared by Mr Katsumi Shimizu, Mr Masatoshi Ohkura and Mr Shizuo Shimojima. These have been deposited in the Visitor's Centre of the Board of Education, Shokawa village, and carry the prefix SBEG VP. Five of Mr Shibata's specimens can be attributed to a single genus, and of these, three (IBEF VP 17, a left dentary; IBEF VP 18, a right dentary with associated frontals; and IBEF VP 19, a right maxilla) probably belong to a single individual as they bore consecutive field numbers and were found in the same piece of rock. A further three maxillae of the same genus were recovered from the collections of Mr Ohkura (SBEG VP 001 and 002) and Mr Shimizu (SBEG 003). SYSTEMATIC P A L A E O N T O L O G Y SQUAMATA SCINCOMORPHA S a k u r a s a u r u s nov. gen. Type and only species - Sakurasaurus shokawensis. Derivation o f n a m e - From the Japanese word, Sakura, meaning cherry blossum, in reference to the ancient cherry blossum trees for which Shokawavillage is famous. Range - Early Cretaceous (140-120 Ma) of Japan. Diagnosis
-
As for type and only species.
Sakurasaurus shokawensis nov. sp. Derivation
of name
-
From the village of Shokawa, close to
the type locality. Holotype - IBEF VP 17, a left mandible (Fig. 1A, Fig. 3). Type locality - KO2, Stream section in the KobudaniValley, near Shokawa village, Gifu Prefecture, Japan (36E03' N; 136 E53'E). Type Horizon - Bonebed approximatelymidwaythrough the basal member of the Okurodani Formation,Tetori Group.
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FIOURE 1 - Sakurasaurus shokawensis nov. gen. et sp., Okurodani Formation, Japan. A, IBEF VP 17, holotype left mandible in lateral view; B, IBEF VP 18, right dentary in partial medial view; C, IBEF VP 18, right dentary in partial ventral view to show structure of the symphysis. All scale bars = l m m . Abbreviations used in the Figures: a, angular; ac, acetabulum; ap, anterior symphysial process; co, lateral border of conch; cp, coronoid process of dentary; d, dentary fragments; il, ilium; is, ischium; J, jugal facet; n, nasal facet; pa, recess for processus ascendens of supraoccipital; pf, postfrontal facet; p p , posterior process; ppr, postparietal process; p r a , prearticular; prf, prefrontal facet; pt, possible broken base of pterygoid lappet; P u , pubis; sp, splenial; sq, squamosal notch or groove; su, surangular; utf, upper temporal fenestra. A, holotype, mandibule gauche, vue latdrale; B, dentaire droit, vue mdsiale partielle; (7, dentaire droit, vue semi-ventrale montrant la structure de la symphyse.
~===~ FIGURE 2 - Sakurasaurus shokawensis nov. gen. et sp., Okurodani Formation, Japan. A-C, paratype, left maxilla, SBEG VP 001, in A, lateral, B, partial medial, and C, alveolar views. Scale b a r = 1 mm. A-C, paratype, maxiUaire gauche, A, vue latdrale, B, vue mdsiale incomplete, C, vue ventrale. P a r a t y p e - SBEG VP 001, a left maxilla (Fig. 2A-C). N o t e - A maxilla is chosen as a paratype r a t h e r t h a n a second dentary as maxillary characters (e.g. shape of facial process, premaxillary process; orbital process; p a t t e r n of facets for neighbouring bones) are particularly useful in distinguishing between members of related taxa, while dentaries can be more difficult to distinguish at low taxonomic level. R e f e r r e d s p e c i m e n s - IBEF VP 18, a right dentary, frontals and ectopterygoid; IBEF VP 19, a right maxilla; IBEF VP 25, a right frontal; IBEF VP 20, a parietal; SBEG VP 002, a left maxilla; SBEG VP 003, a right maxilla. All from the same horizon as the holotype.
Diagnosis - A scincomorph lizard characterised by the following combination of derived features: mandible short and robust with deep robust postdentary region; posterolateral dentary process
apparently overlapping coronoid laterally; medial surface of maxilla has facets for prefrontal and lacrimal and suggests the maxilla met the frontal to separate nasals and prefrontals; heterodont pleurodont dentition, with curved weakly keeled anterior teeth and short, blunt striated posterior teeth; frontals paired, sculptured and with strongly forked anterior nasal margins; cristae cranii
892 well-developed but not approaching in the midline; fronto-parietal suture transverse but with lateral processes separated by central interdigitated region; angles of narrow dorsolateral facets suggest postfrontal bone was furcate, clasping fronto-parietal suture; anterolateral borders of parietal without strong flanges to underlie frontals but with small pocket facets which apparently received the posterolateral corners of the frontals; postparietal processes short, triangular and almost horizontal in orientation; processes separated in midline by deep pit for processus ascendens bounded by short flanking processes. C o m p a r i s o n - Sakurasaurus differs from all previously described Late J u r a s s i c and Early Cretaceous fossil lizards in the possession of a strongly heterodont dentition with blunt posterior crushing (durophagous) teeth, and in the morphology of the parietal with its deep posterior pit and flanking processes. The robust posterior teeth most closely resemble those of an unnamed jaw fragment (Richter 1994b) from the Spanish Early Cretaceous locality of Galve, but the Spanish specimen shows only a portion of the tooth row and is therefore difficult to compare in any detail with that of Sakurasaurus. The only other early lizard known to have a clearly heterodont dentition is Meyasaurus (Evans & Barbadillo 1997) from several sites of Early Cretaceous age in Spain. However, in Meyasaurus, the posterior teeth are slender and bicuspid rather than blunt and striated. In the shape of the crown, the posterior teeth of Sakurasaurus show some resemblance to those
FIGURE 3 - Sakurasaurus shokawensis nov. gen. et sp., Okurodani Formation, Japan. Scanning Electron Micrographs of the dentition. A-B, holotype left mandible, IBEF 17, A, anterior tooth, B, posterior tooth; C,D, right dentary, IBEF 18, C, part of anterior dentition, D, posterior tooth. All scale bars = 100F except C, 500F. Photo SEM de la denture. A,B, holotype, mandibule gauche: A, dent antdrieure; B, dent postgrieure; C,D, dentaire droit: C, denture antdrieure pro parte; D, dent postdrieure.
of a very poorly known taxon from the Jurassic/ Cretaceous of China (Shikama 1947). This jaw, named Teilhardisaurus and attributed to a lizard, is problematic and may not be reptilian. The teeth are much longer and more slender than those of Sakurasaurus, but the posterior crowns have a similar form. Unfortunately, the wherabouts of this specimen is now unknown. A similar problem exists with the only other Mesozoic lizard to be described from Japan, Tedorosaurus (SmKAMA 1969). The specimen is in a private collection and is not available for examination. Shikama's (1969) figure and descriptions suggest sharply pointed teeth along the entire tooth row, a condition at variance with that of Sakurasaurus. D e s c r i p t i o n - Three specimens, IBEF VP 17, 18 and 19, are of similar size and dental morphology, and have consecutive field numbers, 911103-011, 911103-012, and 911103-013. This means they were recovered from the same piece of rock collected on November 3rd, 1991. Since they also include both left and right dentaries, it is highly likely that the specimens belong to a single individual. As such, they provide the basis for our understanding of the morphology of Sakurasaurus. IBEF VP 17 is a well-preserved left dentary with associated accessory bones. The bone is deep and robust (Fig. 1A) with a sharp posterodorsal border which probably overlapped the coronoid but no marked posterior incisures. The dentition (Fig. 3) consists of around twelve small slightly recurved anterior teeth with weak anterior and posterior
893 keels. These are followed by eleven broader strongly striated teeth in which the crown becomes increasingly blunt. As a whole, the dentition suggests a durophagous diet, in which tough-bodied invertebrates were caught and held by the anterior dentition before being crushed by the posterior molariform teeth. Laterally, there are six neurovascular foramina. The surangular has disarticulated slightly, becoming posteriorly displaced so that the facet for the dentary is visible. The contact between the two bones was strong. The surangular foramen is clearly visible and is entirely within the surangular. The angular has been exposed by a break in the lower posterior border of the dentary. The bone is slender and the majority of it seems to be restricted to the medial surface of the jaw. The articular is not preserved but its impression is clearly visible. As might be expected from the stout posterior teeth, the posterior part of the jaw is short, deep and robust. The edge of a splenial is visible from the inferolateral surface as is part of the surangular. The coronoid has been displaced upwards but is preserved mostly in impression, indicating only a strong dorsal process, a short anterior process and a deep ventral flange. IBEF VP 18 (Fig. 1B,C) is a right dentary which complements the left as it is preserved in medial view, providing further information on tooth shape and implantation as well as the form of the Meckelian groove (Fig. 1B,C; Fig. 3). Again the dentition consists of an anterior set of 11-12 small tapering closely packed teeth, with a further eight larger thicker teeth like those on the holotype IBEF VP 17. The teeth show rapid iguanian replacement, as evidenced by the frequency of replacement pits. They are supported below by a strong subdental ridge above an open Meckelian canal. The canal becomes nearly horizontal and ventral anteriorly, and bears a strong horizontal splenial facet on its upper margin. The symphysis is weak but of rather peculiar shape (Fig. 1C) with a small anterior process. Whether the process is a charac-
FIGURE 4 - S a k u r a s a u r u s shokawensis nov. gen. et sp., O k u r o d a n i F o r m a t i o n , J a p a n . I B E F VP 19, r i g h t m a x i l l a , in m e d i a l view. Scale b a r = 1 ram. Maxillaire droit, vue
mgsiale.
teristic feature of the species, or an anomaly, cannot be determined without a more representative sample of specimens. Preserved with the dentary, and ahnost certainly part of the same individual, are paired articulated frontals (Fig. 5A). These have a pustulate sculpture but no trace of overlying scale marks. The midline suture is straight and relatively simple (i.e. no marked interdigitation). There are anterior processes forming a single median process, and lateral processes. These processes are separated by a deep facet - presumably for the nasal. The bones are relatively long and almost parallel-sided, widening slightly posteriorly towards the frontoparietal suture. At this point, the frontal appears to have been expanded slightly to form a lateral extension which met a lateral flange from the parietal, and a central region which contributed to an interdigitated frontoparietal suture. On the underside of the same small block is a right ectopterygoid, with a small lateral foot, slender neck and forked pterygoid flange. The maxilla of Sakurasaurus is represented by four specimens all of which show the same heterodont dentition as the dentaries. Three specimens (SBEG VP 001,002 and 003) are preserved in lateral view and show the shape of the sculptured facial and premaxillary processes elearty (Fig. 2A), The fourth, IBEF VP 19 (Fig. 4), is preserved in medial view. The posterior section of the orbital process had broken and rotated away from the remainder of the bone during preservation, but is restored in position in figure 4. The facial process is deep and appears to have a sharply pointed dorsal process incised from below. However, careful examination - prompted by the other maxillae, shows that this is artifact. The process is, in fact, broad and rounded with pustulate lateral sculpture. This dorsal process is also strongly facetted medially and it seems clear that the maxilla met, or nearly met, the lateral process of the frontal to separate the nasal from the prefrontal. The poste-
894 FIGURE 5 - S a k u r a s a u r u s shokawensis nov. gem et sp., Okurodani Formation, Japan. Skull roofing ~ones. A, IBEF VP 18, paired ~rontals in dorsal view; B,C, IBEF VP 25, a right frontal in B, dorsal, ~nd C, lateral views; D,E, IBEF VP 20, parietal, in D, ventral view ?rior to preparation of dorsal surhce, and E, partial dorsal view. ~cale bars = i mm. Ossements du oit cr~tnien. A, frontaux, rue dor~ale; B, C, frontal droit: B, rue dor~ale, C, rue latgrale: D,E, paridtaI: 9, rue ventrale avant prdparation; ~,, vue dorsale partielle apr~s prdmration de la surface.
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rior process is relatively deep and the jugal, while extending forward, may not have been visible in the anterolateral orbital margin. IBEF VP 25 is a partial frontal (Fig. 5B,C) which shares the same distinctive shape and sculpture to those described above and can be attributed to the same taxon. The orbital flanges are deep but they did not meet in the ventral midline. The postfrontal/postorbitofrontal facet is small by comparison with the strong prefrontal facet. IBEF VP 20 is a relatively well-preserved parietal (Fig. 5D,E) which is attributed tentatively to Sakurasaurus on the basis of the general fit between it and the posterior margin of the frontal. The specimen as originally prepared, in ventral view (Fig. 5D), was complete, but preparation of the dorsal surface (Fig. 5E) has resulted in a small amount of damage to the anterior region. The body is short with wide triangular postparietal processes which lie in the horizontal plane and taper sharply. The dorsal surface bears shallow pustulate sculpture (like that on the rear portion of the frontals described above). The pit for the processus ascendens is flanked by short but pronounced medial processes. Anteriorly, the frontoparietal suture shows strong medial interdigitations flanked by more rounded
lateral processes which clearly received a small facetted flange from the frontal (for which they have a little niche). There is a small central parietal foramen and the adductor muscles were clearly ventral, but there is no trace of descending processes of the kind seen in many living scincids. ADDITIONAL COMPONENTS OF THE
LIZARD
ASSEMBLAGE
While the majority of the lizard bones recovered from KO2 by the Shokawa collectors are attributable to Sakurasaurus, there is skull and jaw material which is clearly distinct from that of Sakurasaurus, as well as unattributable elements (a dorsal vertebrae, a pelvis, a quadrate). While these additional specimens are too fragmentary to formally name, they add to our knowledge of the diversity of the Japanese lizard assemblage at this time. LIZARD B Lizard B is represented by a well-preserved parietal and possible frontal, associated on the basis of similarities in sculpture. Both have a much coarser sculpture than that of Sakurasaurus. IBEF VP 26 (Fig. 6A) is a single frontal which is smaller than those described for Sakurasaurus,
895 6 - Lizard B, Okurodani Formation, Japan. Skull roofing elements in dorsal view. A, frontal, small arrows mark posterior limits of prefrontal facets; B, parietal. Scale bar = 1 mm. Osse-
FIGURE
Jk
ments clu toit crgtnien en vue dorsale; A, frontal; les fl~ches indiquent la limite postdrieure des facettes prgfrontales; B, paridtal.
pf
FICURE 7 - Lizard C, Okurodani Formation, Japan. Partial left dentary in lateral view. Dentaire gauche incomplet, rue latdrale.
b u t w h e r e left a n d r i g h t sides a r e f u s e d w i t h o u t a t r a c e of a midline s u t u r e . B e t w e e n the orbits, the bone is slightly w a i s t e d . A n t e r i o r l y t h e r e are facets a n d processes as in I B E F VP 18 a n d 25, b u t the a r r a n g e m e n t is different - t h e l a t e r a l a n d m e d i a n processes a r e not as s t r o n g a n d the b o r d e r is less deeply incised. T h e p r e f r o n t a l facet is large a n d e x t e n d s well b a c k a l o n g t h e bone - a l m o s t to the point of m i n i m u m i n t e r o r b i t a l w i d t h - a n d t h e r e are deep oblique orbital flanges (cristae cranii) which e x t e n d f u r t h e r t o w a r d s t h e midline. I B E F VP 24 (Fig. 6B) is a complete parietal, preserved in dorsal view, which differs strikingly from I B E F VP 20. The surface is coarsely s c u l p t u r e d with a raised a r e a a r o u n d the central p a r i e t a l foramen. The l a t e r a l borders b e a r deep flanges indicating t h a t the u p p e r t e m p o r a l f e n e s t r a e were large and t h a t the a d d u c t o r m u s c u l a t u r e was not restricted to the v e n t r a l surface of the bone. The postparietal processes are long, d o r s o v e n t r a l l y deep, and ridged along the dorsal midline to create a strong
posterior surface for the neck muscles. There is no trace of the paired median processes seen in IBEF VP 20 and the frontoparietal suture also looks to be less imbricated. In addition, the bone is long - this animal had long open upper temporal fenestrae in strong contrast to those of IBEF VP 20. LIZARD
C
IBEF VP 21 is a relatively well preserved left dentary (lateral aspect) with eroded teeth (Fig. 7). It has a sharply tapering anterior symphyseal region deepening posteriorly. The rear of the bone is damaged but bears short dorsal and ventral processes. The dorsal process matches that of Sakurasaurus and many scincoids in which the dentary overlaps the coronoid. Laterally, the bone bears five neurovascular foramina, the anteriormost opening into a marked groove which runs to the tip of the jaw. The bone bears about 20 tooth positions but the teeth are all damaged. In general shape, IBEF VP 21 resembles
896 FIGURE 8 - Isolated s q u a m a t e right quadrate, Okurodani Formation, Japan, in A, lateral; B, posterior, * m a r k s position of f o r a m e n for chorda t y m p a n i nerve; and C, dorsal views. Scale bar = i m m . Carrd droit isolg, A, rue latdrale; B, vue postgrieure, C, rue dorsale.
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the dentary of Sakurasaurus, but the tapering anterior region is distinctive and appears to be indicative of a separate taxon. Without the dentition, however, it is difficult to be certain. Similarly, without further material, we are not in a position to judge whether the elements attributed to lizard B and lizard C might belong to a single taxon. NON-DENTAL LIZARD ELEMENTS
IBEF VP 27 (Fig. 8A-C) is a right quadrate. The medial border is damaged but appears to include the broken base of a small pterygoid lappet. The lateral conch is well developed and has a clear "tympanic" crest which is deeply notched dorsally and has a hooked posterior tip. In lateral view (Fig. 8A), the bone is seen to have a strongly overhanging posterodorsal process, which has a posterior articular surface (Fig. 8B) for the paroceipital process of the opisthotic and is deeply grooved laterally for the squamosal. In dorsal view (Fig. 8C), this posterior process is seen to be sharply demarcated from the rest of the bone. IBEF VP 23 (Fig. 9A-F) is a procoelous dorsal vertebra with a completely formed condyle and a strong zygosphene/zygantral system (seen most clearly in dorsal, Fig. 9D, and anterior, Fig. 9F, views). The centrum is flask-shaped like that of many scincomorphs and is ventrally ridged and grooved - not unlike the centrum of the Spanish Early Cretaceous lizard Meyasaurus (Evans & Barbadillo 1997). IBEF VP 22 is a partial conjoined pelvis, with the ilium and the proximal parts of the pubis and ischium (Fig. 10). The ilium has a long slender iliac blade, with a strong dorsal flange rising from a pronounced lateral ridge. There are no taxonomically useful characters except that the acetabular surface appears to lie well below the level of the sacral articulation - a possible scleroglossan state. DISCUSSION
D
E
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SAKURASA UR US
FIGURE 9 - Squamate dorsal vertebra, Okurodani Formation, Japan, in A, left lateral view; B, ventral view; C, right lateral view; D, dorsal view; E, posterior view; and F, anterior view.
Although the remains attributable to Sakurasaurus are limited, there is enough information for
Scale bar = 1 r a m . Vert~bre dorsale, A, vue latdrale gauche; B, vue ventrale; C, vue latgrale droite; D, vue dorsale, E, vue postdrieure; F, vue ant~rieure.
897 FIGUR~ 10 - S q u a m a t e left pelvic girdle, lateral view. Scale b a r = l m m . Ceinture pelvienne gauche,
vue latdrale.
a general discussion of relationships. The deep subdental shelf, vermiculate skull ornament and clearly bifurcate postfrontal/postorbitofrontal argue for scleroglossan affinity (Estes et al. 1988). At the same time, the strong subdental shelf and iguanid type tooth replacement support scincomorph rather than anguimorph relationship. The heterodonty and centrally interdigitating frontoparietal suture are lacertoid features (lacertids, teiids, gymnophthalmids), but the absence of anterolateral parietal tabs is problematic. Similarly, while the absence of scale marks on the roofing bones and the heterodonty would be consistent with teioid affinity, as would the narrow curved premaxillary process of the maxilla, but Sakurasaurus lacks the typically teioid step in the maxillary tooth row (Estes et al. 1988). The strong posterodorsal coronoid process of the dentary is a scincoid character state (scincids, cordylids), and the median processes on the parietal and the posterior dentary process which overlaps the coronoid resemble those of some scincoids, but this is contradicted by the absence of descending parietal processes. We entered the character states of Sakurasaurus into a data matrix (31 terminal lepidosauromorph taxa, 259 character states: characters and main matrix published elsewhere, Evans & Barbadillo, in press a,b; Evans & Chure 1998). Using the heuristic search mode, Paup 3.1 yielded a single tree (length 492 steps, CI - 0.46; RI - 0.59) in which Sakurasaurus was positioned as the sister group to all other scincomorphs (i.e. scincids, cordylids, teiids, lacertids, xantusiids and gymnophthalmids). Clearly, with the very limited information available for Sakurasaurus, this is only a very provisionM result, but it does support scincomorph affinity. Excavations in the Okurodani Formation and its lateral equivalents are conti-
.-.-...~-..:~;:~.:~ ~ -
nuing and we may expect additional material to be found in due course. THE OTHER LIZARDS Lizard B is represented by fused frontals and parietals (if correctly associated). The shape of the frontoparietal region again suggests the presence of a strongly bifurcate postfrontal or postorbitofrontal a scleroglossan character state. Fused frontals occur in iguanians and teiids, and as a variable feature in other groups but the posterior position of the parietal foramen makes an iguanian unlikely (although the position in reversed in anoles), as does the apparently bifurcate structure of the postfrontal/postorbitofrontal. The upper temporal fenestrae were clearly widely open and the adductor muscles invaded the sides of the parietal. The parietal is long with extended posterior processes suggesting large upper temporal fenestrae as in iguanians and teiids, but the shape, the general pattern of the dermal sculpture, and the triangular interparietal shield region (Borsuk-Bialynicka 1984, Fig. 24) all resemble that of living anguids such as Anguis and Gerrhonotus. Frontal fusion and deep orbital flanges occur in many groups, but would also be consistent with an anguimorph, as would the long posterior orbital processes of the prefrontals (a feature of anguines and some gerrhonotines, Rieppel 1980). No clearly anguimorph jaw material has yet been found, however, and pending further specimens, lizard B remains incertae sedis, as does lizard C. CONCLUSIONS The lizards from the Okurodani Formation of the Tetori group in Gifu Prefecture represent some of the oldest lizard specimens in Japan. The only can-
898
didate for an older lizard specimen is the single specimen of Tedorisaurus, supposedly from the Late Jurassic Kuzuryu Subgroup of the Tetori Group, Fukui Prefecture (Shikama 1969). Unfortunately, this specimen is not available for study. Early Cretaceous lizard assemblages have now been recorded from Europe (Britain, Spain, Italy, Hoffstetter 1967; Richter 1994a,b; Evans & Barbadillo 1997), North (Winkler et al. 1990), South (Evans & Yabumoto 1998) and Central America (Mexico, Reynoso 1995, 1998), Africa (Morocco, Richter 1994a, Broschinski & Sigogneau-Russell 1996), and Asia (Mongolia, China - Alifanov 1989a, 1993; Endo & Shikama 1942). Few of these lizards are known in any detail (exceptions are those from Mexico and Spain) and none show a marked resemblance to those from Shokawa. Recently, however, new lizard material has been recovered from a locality at Shiramine, Ishikawa Prefecture, Japan, in a horizon roughly contemporaneous with that at Shokawa. Although work on this material is still in progress, the Shiramine material includes paramacellodids, a group of scincomorphan lizards with an almost global distribution in the Jurassic and Early Cretaceous (Evans & Chure 1998). The new Japanese material thus adds to our general knowledge of lizard diversity in the Early Cretaceous, and specifically to our understanding of Asian lizard assemblages in the Mesozoic. This is important. As a result of the extraordinarily rich finds of Late Cretaceous lizards made by the Polish-Soviet, American M u s e u m of Natural History, and Institute of Vertebrate Palaeontology and Palaeoanthropology expeditions to Inner and Outer Mongolia over the last thirty years, we will soon have an unprecedented knowledge of Late Cretaceous lizard diversity (iguanians, scincomorphs, anguimorphs) in Asia (Sulimski 1972, 1975; Borsuk-Bialynicka 1984, 1985, 1988; Borsuk-Bialynicka & Moody 1984; Alifanov 1989b; Borsuk-Bialynicka & Alifanov 1991; Gao & Hou 1992, 1995, Keqin Gao, pers.comm.1997). As yet, however, we know relatively little about the earlier Asian assemblages from which they arose, and this must form a priority in future work. A c k n o w l e d g e m e n t s - We are indebted to the fossil collectors of Shokawa - Mr Shibata, Mr Shimizu, Mr Ohkura, and Mr Shimojima for finding and preparing the material described here, for making it available to us for study, and for their willingness to deposit it in regional museums. The Mayor and Administration of Shokawa Village, Gifu Prefecture, Japan, have been generous in their hospitality and support. We are also grateful to Dr Keqin Gao for discussions about lizard material from China and Central Asia. Drs Liz Cook and Chris Nicholas shared with us the results of their work on the taphonomy and geology of the KO2 locality. Dr Denise Sigogneau-Russell (Paris) was kind enough to help with the French abstract, and we are grateful to Dr J.-C. Rage (Paris) and Dr P.A. Murry (Texas) for
suggesting improvements to the text. The text figures were mostly drafted by Aysha Raza (UCL). This work was funded by the Royal Society/British Council/Japanese Society for the Promotion of Science Joint Research Projects Program.
REFERENCES AL1FANOVV.R. 1989a - The oldest gecko (Lacertilia: Gekkonidae) from the Lower Cretaceous of Mongolia. Paleontological Journal, 23: 128-131. ALIFANOVV.R. 1989b - New priscagamids (Lacertilia) from the Upper Cretaceous of Mongolia and their systematic position a m o n g I g u a n i a . Paleontological Journal, 1989: 68-80. ALIFANOVV.R. 1993 - Some peculiarities in the Cretaceous and Palaeogene lizard faunas of the M o n g o l i a n People's Republic. Kaupia, 3: 9-13. AZUMA Y. • TOMIDAY. 1995 - Early Cretaceous dinosaur fauna of the Tetori Group in Japan. In AILING SUN & YUANQING WANO (eds), Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short papers, 125-131. China Ocean Press, Beijing. BORSUK-BIALYN1CKA M. 1984 - Anguimorphans and related
lizards from the Late Cretaceous of the Gobi Desert, Mongolia. Palaeontologia Polonica, 46: 5-105. BO~SuK-B~ALYNtCKA M. 1985 - Carolinidae, a new family of xenosaurid-like lizards from the Upper Cretaceous of Mongolia. Acta Palaeontologica Polonica, 30: 151-176. BORSUK-BIAL~ICKA M. 1988 - Globaura venusta gen. et sp. nov. and Eoxanta lacertifrons gen. et sp. nov. - non-teiid lacertoids from the Late Cretaceous of Mongolia. Acta Palaeontologica Polonica, 33: 211-248. BORSUK-BIALYNICKA M. & ALIFANOV V.R. 1991 - First Asiatic 'iguanid' lizards in the Late Cretaceous of Mongolia. Aeta Palaeontologica Polonica, 36: 325-342. BORSUK-B;ALYNIC~(A M. & MOODY S.M. 1984 - Priscagamidae, a
new sub-family of the Agamidae (Sauria) from the Late Cretaceous of the Gobi Desert. Acta Palaeontologica
Polonica, 29: 51-81. BROSCHINSKI A. & SIGOGNEAU-RUSSELL D. 1996 - Remarkable lizard remains from the lower Cretaceous of Anoual (Morocco). Annales de Paldontologie (Vert.-lnvert.) , 82: 147-175. CLUZELD. & CADETJ-P. 1992 - Geodynamic evolution of Korea: a view. The IslandArc, 1: 64-70. Cook E., ISAJI S. & MANABE M. 1998 - Preliminary results of a t a p h o n o m i c s t u d y of a vertebrate accumulation from the Tetori G r o u p (Lower Cretaceous) of Japan. Paleontological Research, 2: 47-52. ENDO R. & SHII~MA T. 1942 - Mesozoic reptilian fauna in the Jehol mountainland, Manchoukuo. Bulletin of the Central National Museum, Manchoukuo, 3, 12 p. ESTES R., GAUTHI~RJ. & DE QUEIROZK. 1988 - Phylogenetic relationships within Squamata. In EST~S R. & PREGILL G. (eds), Phylogenetic Relationships of the Lizard Families: Essays commemorating Charles L. Camp. Stanford: Stanford University Press: 119-281. EVANS S.E. 1993 - Jurassic lizard assemblages. Revue de Paldobiologie, Vol. Sp., 7: 55-65. EVANS S.E. & BARBADILLOL.J. 1997 - Early Cretaceous lizards from los Hoyas, Spain. Zoological Journal of the Linnean Society, 119: 23-49. EVANS S.E. & BARBADILLOL.J. 1998 - An u n u s u a l lizard from the Early Cretaceous of Las Hoyas, Spain. Zoological Journal
of the Linnean Society, 124: 235-265. EVANS S.E. & BARBADILLOL.J. 1999 - A short-limbed lizard from the Early Cretaceous of Spain. Special Papers in Palaeon-
tology, 60: 73-85. EVANS S.E. & CHURE D.C. 1998 - Paramacellodid lizard skulls from the Jurassic Morrison Formation at Dinosaur Natio-
899 nal Monument, Utah. Journal of Vertebrate Paleontology, 18: 99-114.
EVANS S.E., MANABE M., COOK E., HIRAYAMA R., ISMI S., NmHOLAS C.J., UNWIND. • YABUMOTO Y. 1998 - An Early Cretaceous assemblage from Gifu Prefecture, Japan. Bulletin of the
New Mexico Museum of Natural History, 14: 183-186. EVANS S.E. • YABUMOTO Y. 1998 - A lizard from the Early Cretaceous Crate Formation, Araripe Basin, Brazil. Neues Jahrbuch fi~r Geologic und Paliiontologie, 1998 (6): 349-364. FAUREM.& CHARVETZ. 1987 - Late Permian/early Triassic orogeny in Japan: piling up ofnappes, transverse lineation and continental subduction of the Honshu block. Earth and Planetary Science Letters, 84: 295-308. GAO K-Q, & Hou L-H. 1992 - Fossil lizards from the Upper Cretaceous Djadochta Formation, the Gobi Desert of China. Journal of Vertebrate Paleontology, 12: 29A. GAO K-Q. & Hou L-H. 1995 - Iguanians from the Upper Cretaceous Djadochta Formation, Gobi Desert, China. Journal of Vertebrate Paleontology, 15: 57-78. GAO K-Q. & NESSOVL.A. 1998 - Early Cretaceous squamates from the Kyzylkum Desert, Uzbekistan. Neues Jahrbueh f~tr Geologie und Pal(tontologie, 207: 289-309. GIFU-KEN DINOSAURRESEARCH COMMITEE 1993 - Report on the dinosaur fossil excavation in Gifu Prefecture, Japan. Gifu. 46 p, Gifu Prefectural Museum [in Japanese]. Gr~ADSTEN F.M., ACTER~RRG F.P., eGG J.G., HARDENBOLJ., VAN VEEN P., THIERRY J. & HUANG Z. 1995 - A Triassic, Jurassic and Cretaceous time scale. In BERGGRENW.A., KENT D.u AUBRY M.P. & HARDENEOL J. (eds), Geochronology Time
Scales and Global Stratigraphic Correlation, SEPM (Society for Sedimentary Geology) Special Publication, 54: 95-126. Tulsa, Oklahoma.
HARLAND W.B., ARMSTRONG
R.L., COXA A.V., CRAIG L.A., SMITH
A.G. & SMITH D.G. 1990 - A geologic timescale 1989, 263 p. Cambridge University Press, Cambridge.
HAS~AWA Y., MANABE M., I~AZl S., OI{KURA M., SmRATA I. & YAMAGUCHI I. 1995 - Terminally resorbed iguanodontid teeth from the Neocomian Tetori Group, Ishikawa and Gifu Prefecture, J a p a n . Bulletin of the National Science Museum, Series C (Geology & Paleontology), 21: 35-49. HOFFSTETTER R. 1 9 6 7 - Coup d'oeil sur les Sauriens (=lacertiliens) des couches de Purbeck (Jurassique sup6rieur d'Angleterre. R6sum6 d'un M6moire). Colloques Inter-
nationaux du Centre National de la Recherche Scientifique, 163: 349-371. ISOSAKIY. 1996 - Anatomy and genesis of a subduction-related orogen: a new view of geotectonic subdivision and evolution of the Japanese Islands. The IslandArc, 5: 289-320. MAEDA S. 1961 - On the geological history of the Mesozoic Tetori Group in Japan. Journal of the Collections of Arts and Science, Chiba University 3:369-426 [in Japanesel MANABEM.& HASEGAWAY. 1995 - Diapsid fauna and its palaeobiogeographical implication; the Neocomian section of the Tetori Group, Japan. In SUN A-L. & WANGY-Q. (eds), Sixth
Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short papers, 179. China Ocean Press, Beijing. MATSUKAWAM., KAWASHIMAK. & KOARAIK. 1996 - Nonmarine molluscan assemblages in the middle p a r t of the Tetori Group (Upper J u r a s s i c to Lower Cretaceous), Gifu Prefecture, central Japan. Bulletin of the Tokyo Gakugei University Section, 4 48:101-113 [in Japanese with English abstract].
NESSOVL.A. 1997 - Cretaceous nonmarine vertebrate~ofNorthern Eurasia. University of Saint-Petersburg, Institute of Earth Crust. 217 p + 60 pl. St Petersburg, Russia [in Russianl. NICHOLASC.J., In press - Geology of the Shokawa vertebrate beds in the Jurassic-Cretaceous Tetori Group, Gifu Prefecture, Japan. Journal of the Geological Society of Japan. OTSU~a K. 1992 - Oblique subduction, collision of micro-continents and subduction of oceanic ridge: their implications on the Cretaceous tectonics of Japan. The Island Arc, 1: 51-63. REYNOSO V.H. 1995 - Lepidosaurian reptiles from the Cantera Tlayua (Albian), Tepexi de Rodriguez, Puebla, Mexico. Second
International Symposium on Lithographic Limestones, Lleida-Cuenca (Spain), Extended Abstracts, 131-132. Ediciones de la Universidad Aut6noma de Madrid, Spain. REYNOSOV.H. 1998 - HuehuecuetzpaUi mixtecus gen. et sp. nov.: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodriguez, Central Mexico. Philosophical Transactions of the Royal Society, (B), 353: 477-500. RICHTERA. 1994a - Der probSlematischer Lacertilier Ilerdaesau. rus (Reptilia: Squamata) aus der Unter-Kreide von Ufia und Galve (Spanien). Berliner geowissenschaftliche Abhandlungen, 13: 135-161. RICHTERA. 1994b - Lacertilier aus der Unteren Kreide von Ufia und Galve (Spanien) und Anoual (Marokko). Berliner geowissenschaftliche Abhandlungen, 14,147 p. RIEPPEL O. 1980 - The phylogeny of anguimorph lizards. Denk-
shriflen der Schweizerischen Naturforschenden Gesellschaft, 94: 5-86. SHIKAMA W. 1947 - Teilhardosaurus and Endotherium, new Jurassic Reptilia and Mammalia from the Husui Coalfield, South Manchuria. Proceedings of the Japanese Academy, 23: 76-84. SHIKAMA W. 1969 - On a Jurassic reptile from Miyama-cho, Fukui Prefecture, Japan. Science Reports of Yokohama National University, Section 2, 15: 25-34. SULIMSKIA. 1972 - Adamisaurus magnidentatus nov. gem, nov. sp. (Sauria) from the Upper Cretaceous of Mongolia. Acta Palaeontologia Polonica, 27: 33-40. SULIMS~ A. 1975 - MacrocephMosauridae and Polyglyphanedontidae (Sauria) from the Late Cretaceous of Mongolia. Acta Palaeontologia Polonica, 33: 25-102. TAZAMI M. & ITAYAT. 1996 - Episodic accretion and metamorphism of Jurassic accretionary complex based on biostratigraphy and K-Ar geochronology in the western part of the MinoTamba Belt, Southwest Japan. The Island Arc, 5: 321-336. WINKLER D.A., MURRYP.A. & JACOBS L.L. 1990 - Early Cretaceous (Comanchean) vertebrates of central Texas. Journal of Vertebrate Paleontology, 10: 95-116. "fANG Z., CHENG Y. & WANG H. 1986 - The Geology of China. Oxford Monographs in Geology and Geophysics, 3, 303 p. Oxford, Clarendon Press. S.E. EVANS
Department of Anatomy and Developmental Biology University College London Gower Street G.-B., London WCIE 6BT M. MANABE National Science Museum 3-23-1 Hyakunin-Cho, Shinjuku-Ku Tokyo 169-0073, J a p a n
INTRODUCTION T h e E a r l y C r e t a c e o u s r e p r e s e n t s a k e y period in the t r a n s i t i o n b e t w e e n t h e e s s e n t i a l l y archaic lizard f a u n a s of the J u r a s s i c (e.g. p a r a m a c e l l o d i d s , b a v a r i s a u r s , a r d e o s a u r s , E v a n s 1993) a n d the m o r e m o d e r n a s s e m b l a g e s of t h e L a t e C r e t a c e o u s (e.g. varanoids, a g a m i d s , teiids, Alifanov 1993; Gao & H o u 1995). E a r l y C r e t a c e o u s lizard a s s e m b l a g e s r e m a i n r e l a t i v e l y r a r e b u t are c u r r e n t l y k n o w n f r o m Europe; North, S o u t h a n d C e n t r a l America; Africa; a n d Asia. T h e L a t e C r e t a c e o u s record of lizards in Asia is v e r y good, largely as a r e s u l t of m a n y y e a r s of collecting in C h i n a a n d Mongolia (Gao & H o u 1995). By contrast, the E a r l y Cretaceous record of Asia is limited to f r a g m e n t a r y m a t e r i a l f r o m K a z a k h s t a n (Gao & Nessov 1998; Nessov 1997), Mongolia (Albian, Alifanov 1989a,b,
1993) a n d p r o b a b l y China, if the deposits yielding Yabeinosaurus (Endo & S h i k a m a 1942) are of b a s a l C r e t a c e o u s ( ? B e r r i a s i a n age, Yang et al. 1986) as g e n e r a l l y thought. E a r l y C r e t a c e o u s lizard fossils h a v e n e v e r previously b e e n recorded f r o m J a p a n . H e r e we describe a n a s s e m b l a g e of f r a g m e n t a r y lizard r e m a i n s from the E a r l y C r e t a c e o u s O k u r o d a n i F o r m a t i o n , Tetori Group, of C e n t r a l H o n s h u , J a p a n . GEOLOGY T h e s p e c i m e n s described h e r e w e r e r e c o v e r e d f r o m a bone-bed horizon in t h e K o b u d a n i Valley, S h o k a w a village, Gifu P r e f e c t u r e . T h e locality, d e s i g n a t e d K 0 2 by its finder, Mr Ikoi S h i b a t a , b u t listed s i m p l y as Locality 2 by H a s e g a w a et al.
890 (1995, p. 38), has yielded more t h a n 800 vertebrate fossils (Evans et al. 1998), as well as invertebrates and plants. The Jurassic-Cretaceous (Bathonian-Albian) Tetori Group outcrops in Central Japan (Ishikawa, Fukui, Gifu and Toyama Prefectures, of Central Japan; see Azuma & Tomida 1995; Manabe & Hasegawa 1995, for review). Traditionally (e.g., Maeda 1961; Azuma & Tomida 1995), the Tetori Group has been divided into three parts - the lower Kuzuryu subgroup (Bajocian to Oxfordian in age), the Itoshiro subgroup (Kimmeridgian to Berriasian), and the upper Akaiwa subgroup (Valanginian to Albian). The KO2 bone-bed horizon is in the Okurodani Formation which forms the upper part of the Itoshiro subgroup (Matsukawa et al. 1996). This would suggest a Berriasian age (135-140 Ma, Harland et al. 1990; 144-137 Ma, Gradsten et al. 1995) for the KO2 assemblage. Fission track and K-Ar analysis of several tuff layers in the Okurodani and Bessantani Formations have given an age of 140-120 Ma (Gifu-Ken Dinosaur Fossil Research Committee 1993), although there may be problems with younger intrusions. More recently, new work in the area has identified further tuff bands both above and below the bone-bed horizon (Nicholas, in press). New radiometric dating of these should provide a tighter constraint on the age of the locality, but at present a basal Cretaceous age seems most likely for the KO2 assemblage. The bone-bed matrix is a dark grey silty-sandstone. The productive horizon is characterised by a basal layer of plant macrofossils, overlain by a concentration of shell debris and bones, and then by rarer articulated specimens (turtles, choristoderes); dinosaur teeth are found scattered throughout. Almost all of the specimens are preserved in 3-D, with relatively little crushing, and they are little abraded, suggesting deposition under relatively low energy conditions (Cook et al. 1998). The most common vertebrates are aquatic taxa - fish, turtles, choristoderes, and KO2 clearly represents a predominantly freshwater assemblage, with rarer terrestrial elements. Previous work suggests t h a t the Late Jurassic Tetori Group sediments were deposited in a narrow marine basin between the land masses of the Sino-Korean continent to the North West, and an active Jurassic accretionary prism to the South East (Faure & Charvet 1987; Cluzel & Cadet 1992; Otsuki 1992; Takami & Itaya 1996; Isozaki 1996; Nicholas, in press). By the Early Cretaceous, a broad coastal plain had developed, with wide meandering river systems flowing northwards into the basin. Recent geological work (Nicholas, in press) has demonstrated t h a t one such river flowed through the Kobudani Valley, and the KO2
bone bed was probably deposited in one of a network of stagnant pools or "ox-bow" lakes, high in organic matter and choked with silt. MATERIAL
The lizard m a t e r i a l from the Okurodani Formation at Shokawa comprises some thirteen specimens including jaw and cranial elements, a vertebra and a pelvis, representing two or more distinct taxa. Most of the material was collected over a period of several years (1990-1995) by a dedicated group of amateur collectors, principally Mr Ikoi Shibata. Much of Mr Shibata's collection, including the material described here, has been formally deposited in the Visitor's Centre of the Izumi Board of Education, Izumi, F u k u i Prefecture, Japan and all those specimens carry the prefix IBEF VP. Additional lizard specimens have been found and prepared by Mr Katsumi Shimizu, Mr Masatoshi Ohkura and Mr Shizuo Shimojima. These have been deposited in the Visitor's Centre of the Board of Education, Shokawa village, and carry the prefix SBEG VP. Five of Mr Shibata's specimens can be attributed to a single genus, and of these, three (IBEF VP 17, a left dentary; IBEF VP 18, a right dentary with associated frontals; and IBEF VP 19, a right maxilla) probably belong to a single individual as they bore consecutive field numbers and were found in the same piece of rock. A further three maxillae of the same genus were recovered from the collections of Mr Ohkura (SBEG VP 001 and 002) and Mr Shimizu (SBEG 003). SYSTEMATIC P A L A E O N T O L O G Y SQUAMATA SCINCOMORPHA S a k u r a s a u r u s nov. gen. Type and only species - Sakurasaurus shokawensis. Derivation o f n a m e - From the Japanese word, Sakura, meaning cherry blossum, in reference to the ancient cherry blossum trees for which Shokawavillage is famous. Range - Early Cretaceous (140-120 Ma) of Japan. Diagnosis
-
As for type and only species.
Sakurasaurus shokawensis nov. sp. Derivation
of name
-
From the village of Shokawa, close to
the type locality. Holotype - IBEF VP 17, a left mandible (Fig. 1A, Fig. 3). Type locality - KO2, Stream section in the KobudaniValley, near Shokawa village, Gifu Prefecture, Japan (36E03' N; 136 E53'E). Type Horizon - Bonebed approximatelymidwaythrough the basal member of the Okurodani Formation,Tetori Group.
891 A
B
L
I
C ap
'~",.~,.~,. I
..~r~,~.: ~I:~:L~.~:.~'~"
I
.-
.-
FIOURE 1 - Sakurasaurus shokawensis nov. gen. et sp., Okurodani Formation, Japan. A, IBEF VP 17, holotype left mandible in lateral view; B, IBEF VP 18, right dentary in partial medial view; C, IBEF VP 18, right dentary in partial ventral view to show structure of the symphysis. All scale bars = l m m . Abbreviations used in the Figures: a, angular; ac, acetabulum; ap, anterior symphysial process; co, lateral border of conch; cp, coronoid process of dentary; d, dentary fragments; il, ilium; is, ischium; J, jugal facet; n, nasal facet; pa, recess for processus ascendens of supraoccipital; pf, postfrontal facet; p p , posterior process; ppr, postparietal process; p r a , prearticular; prf, prefrontal facet; pt, possible broken base of pterygoid lappet; P u , pubis; sp, splenial; sq, squamosal notch or groove; su, surangular; utf, upper temporal fenestra. A, holotype, mandibule gauche, vue latdrale; B, dentaire droit, vue mdsiale partielle; (7, dentaire droit, vue semi-ventrale montrant la structure de la symphyse.
~===~ FIGURE 2 - Sakurasaurus shokawensis nov. gen. et sp., Okurodani Formation, Japan. A-C, paratype, left maxilla, SBEG VP 001, in A, lateral, B, partial medial, and C, alveolar views. Scale b a r = 1 mm. A-C, paratype, maxiUaire gauche, A, vue latdrale, B, vue mdsiale incomplete, C, vue ventrale. P a r a t y p e - SBEG VP 001, a left maxilla (Fig. 2A-C). N o t e - A maxilla is chosen as a paratype r a t h e r t h a n a second dentary as maxillary characters (e.g. shape of facial process, premaxillary process; orbital process; p a t t e r n of facets for neighbouring bones) are particularly useful in distinguishing between members of related taxa, while dentaries can be more difficult to distinguish at low taxonomic level. R e f e r r e d s p e c i m e n s - IBEF VP 18, a right dentary, frontals and ectopterygoid; IBEF VP 19, a right maxilla; IBEF VP 25, a right frontal; IBEF VP 20, a parietal; SBEG VP 002, a left maxilla; SBEG VP 003, a right maxilla. All from the same horizon as the holotype.
Diagnosis - A scincomorph lizard characterised by the following combination of derived features: mandible short and robust with deep robust postdentary region; posterolateral dentary process
apparently overlapping coronoid laterally; medial surface of maxilla has facets for prefrontal and lacrimal and suggests the maxilla met the frontal to separate nasals and prefrontals; heterodont pleurodont dentition, with curved weakly keeled anterior teeth and short, blunt striated posterior teeth; frontals paired, sculptured and with strongly forked anterior nasal margins; cristae cranii
892 well-developed but not approaching in the midline; fronto-parietal suture transverse but with lateral processes separated by central interdigitated region; angles of narrow dorsolateral facets suggest postfrontal bone was furcate, clasping fronto-parietal suture; anterolateral borders of parietal without strong flanges to underlie frontals but with small pocket facets which apparently received the posterolateral corners of the frontals; postparietal processes short, triangular and almost horizontal in orientation; processes separated in midline by deep pit for processus ascendens bounded by short flanking processes. C o m p a r i s o n - Sakurasaurus differs from all previously described Late J u r a s s i c and Early Cretaceous fossil lizards in the possession of a strongly heterodont dentition with blunt posterior crushing (durophagous) teeth, and in the morphology of the parietal with its deep posterior pit and flanking processes. The robust posterior teeth most closely resemble those of an unnamed jaw fragment (Richter 1994b) from the Spanish Early Cretaceous locality of Galve, but the Spanish specimen shows only a portion of the tooth row and is therefore difficult to compare in any detail with that of Sakurasaurus. The only other early lizard known to have a clearly heterodont dentition is Meyasaurus (Evans & Barbadillo 1997) from several sites of Early Cretaceous age in Spain. However, in Meyasaurus, the posterior teeth are slender and bicuspid rather than blunt and striated. In the shape of the crown, the posterior teeth of Sakurasaurus show some resemblance to those
FIGURE 3 - Sakurasaurus shokawensis nov. gen. et sp., Okurodani Formation, Japan. Scanning Electron Micrographs of the dentition. A-B, holotype left mandible, IBEF 17, A, anterior tooth, B, posterior tooth; C,D, right dentary, IBEF 18, C, part of anterior dentition, D, posterior tooth. All scale bars = 100F except C, 500F. Photo SEM de la denture. A,B, holotype, mandibule gauche: A, dent antdrieure; B, dent postgrieure; C,D, dentaire droit: C, denture antdrieure pro parte; D, dent postdrieure.
of a very poorly known taxon from the Jurassic/ Cretaceous of China (Shikama 1947). This jaw, named Teilhardisaurus and attributed to a lizard, is problematic and may not be reptilian. The teeth are much longer and more slender than those of Sakurasaurus, but the posterior crowns have a similar form. Unfortunately, the wherabouts of this specimen is now unknown. A similar problem exists with the only other Mesozoic lizard to be described from Japan, Tedorosaurus (SmKAMA 1969). The specimen is in a private collection and is not available for examination. Shikama's (1969) figure and descriptions suggest sharply pointed teeth along the entire tooth row, a condition at variance with that of Sakurasaurus. D e s c r i p t i o n - Three specimens, IBEF VP 17, 18 and 19, are of similar size and dental morphology, and have consecutive field numbers, 911103-011, 911103-012, and 911103-013. This means they were recovered from the same piece of rock collected on November 3rd, 1991. Since they also include both left and right dentaries, it is highly likely that the specimens belong to a single individual. As such, they provide the basis for our understanding of the morphology of Sakurasaurus. IBEF VP 17 is a well-preserved left dentary with associated accessory bones. The bone is deep and robust (Fig. 1A) with a sharp posterodorsal border which probably overlapped the coronoid but no marked posterior incisures. The dentition (Fig. 3) consists of around twelve small slightly recurved anterior teeth with weak anterior and posterior
893 keels. These are followed by eleven broader strongly striated teeth in which the crown becomes increasingly blunt. As a whole, the dentition suggests a durophagous diet, in which tough-bodied invertebrates were caught and held by the anterior dentition before being crushed by the posterior molariform teeth. Laterally, there are six neurovascular foramina. The surangular has disarticulated slightly, becoming posteriorly displaced so that the facet for the dentary is visible. The contact between the two bones was strong. The surangular foramen is clearly visible and is entirely within the surangular. The angular has been exposed by a break in the lower posterior border of the dentary. The bone is slender and the majority of it seems to be restricted to the medial surface of the jaw. The articular is not preserved but its impression is clearly visible. As might be expected from the stout posterior teeth, the posterior part of the jaw is short, deep and robust. The edge of a splenial is visible from the inferolateral surface as is part of the surangular. The coronoid has been displaced upwards but is preserved mostly in impression, indicating only a strong dorsal process, a short anterior process and a deep ventral flange. IBEF VP 18 (Fig. 1B,C) is a right dentary which complements the left as it is preserved in medial view, providing further information on tooth shape and implantation as well as the form of the Meckelian groove (Fig. 1B,C; Fig. 3). Again the dentition consists of an anterior set of 11-12 small tapering closely packed teeth, with a further eight larger thicker teeth like those on the holotype IBEF VP 17. The teeth show rapid iguanian replacement, as evidenced by the frequency of replacement pits. They are supported below by a strong subdental ridge above an open Meckelian canal. The canal becomes nearly horizontal and ventral anteriorly, and bears a strong horizontal splenial facet on its upper margin. The symphysis is weak but of rather peculiar shape (Fig. 1C) with a small anterior process. Whether the process is a charac-
FIGURE 4 - S a k u r a s a u r u s shokawensis nov. gen. et sp., O k u r o d a n i F o r m a t i o n , J a p a n . I B E F VP 19, r i g h t m a x i l l a , in m e d i a l view. Scale b a r = 1 ram. Maxillaire droit, vue
mgsiale.
teristic feature of the species, or an anomaly, cannot be determined without a more representative sample of specimens. Preserved with the dentary, and ahnost certainly part of the same individual, are paired articulated frontals (Fig. 5A). These have a pustulate sculpture but no trace of overlying scale marks. The midline suture is straight and relatively simple (i.e. no marked interdigitation). There are anterior processes forming a single median process, and lateral processes. These processes are separated by a deep facet - presumably for the nasal. The bones are relatively long and almost parallel-sided, widening slightly posteriorly towards the frontoparietal suture. At this point, the frontal appears to have been expanded slightly to form a lateral extension which met a lateral flange from the parietal, and a central region which contributed to an interdigitated frontoparietal suture. On the underside of the same small block is a right ectopterygoid, with a small lateral foot, slender neck and forked pterygoid flange. The maxilla of Sakurasaurus is represented by four specimens all of which show the same heterodont dentition as the dentaries. Three specimens (SBEG VP 001,002 and 003) are preserved in lateral view and show the shape of the sculptured facial and premaxillary processes elearty (Fig. 2A), The fourth, IBEF VP 19 (Fig. 4), is preserved in medial view. The posterior section of the orbital process had broken and rotated away from the remainder of the bone during preservation, but is restored in position in figure 4. The facial process is deep and appears to have a sharply pointed dorsal process incised from below. However, careful examination - prompted by the other maxillae, shows that this is artifact. The process is, in fact, broad and rounded with pustulate lateral sculpture. This dorsal process is also strongly facetted medially and it seems clear that the maxilla met, or nearly met, the lateral process of the frontal to separate the nasal from the prefrontal. The poste-
894 FIGURE 5 - S a k u r a s a u r u s shokawensis nov. gem et sp., Okurodani Formation, Japan. Skull roofing ~ones. A, IBEF VP 18, paired ~rontals in dorsal view; B,C, IBEF VP 25, a right frontal in B, dorsal, ~nd C, lateral views; D,E, IBEF VP 20, parietal, in D, ventral view ?rior to preparation of dorsal surhce, and E, partial dorsal view. ~cale bars = i mm. Ossements du oit cr~tnien. A, frontaux, rue dor~ale; B, C, frontal droit: B, rue dor~ale, C, rue latgrale: D,E, paridtaI: 9, rue ventrale avant prdparation; ~,, vue dorsale partielle apr~s prdmration de la surface.
ppr I
I
E .-
pf
,i:::::' .....
,
,
.
:
prf
rior process is relatively deep and the jugal, while extending forward, may not have been visible in the anterolateral orbital margin. IBEF VP 25 is a partial frontal (Fig. 5B,C) which shares the same distinctive shape and sculpture to those described above and can be attributed to the same taxon. The orbital flanges are deep but they did not meet in the ventral midline. The postfrontal/postorbitofrontal facet is small by comparison with the strong prefrontal facet. IBEF VP 20 is a relatively well-preserved parietal (Fig. 5D,E) which is attributed tentatively to Sakurasaurus on the basis of the general fit between it and the posterior margin of the frontal. The specimen as originally prepared, in ventral view (Fig. 5D), was complete, but preparation of the dorsal surface (Fig. 5E) has resulted in a small amount of damage to the anterior region. The body is short with wide triangular postparietal processes which lie in the horizontal plane and taper sharply. The dorsal surface bears shallow pustulate sculpture (like that on the rear portion of the frontals described above). The pit for the processus ascendens is flanked by short but pronounced medial processes. Anteriorly, the frontoparietal suture shows strong medial interdigitations flanked by more rounded
lateral processes which clearly received a small facetted flange from the frontal (for which they have a little niche). There is a small central parietal foramen and the adductor muscles were clearly ventral, but there is no trace of descending processes of the kind seen in many living scincids. ADDITIONAL COMPONENTS OF THE
LIZARD
ASSEMBLAGE
While the majority of the lizard bones recovered from KO2 by the Shokawa collectors are attributable to Sakurasaurus, there is skull and jaw material which is clearly distinct from that of Sakurasaurus, as well as unattributable elements (a dorsal vertebrae, a pelvis, a quadrate). While these additional specimens are too fragmentary to formally name, they add to our knowledge of the diversity of the Japanese lizard assemblage at this time. LIZARD B Lizard B is represented by a well-preserved parietal and possible frontal, associated on the basis of similarities in sculpture. Both have a much coarser sculpture than that of Sakurasaurus. IBEF VP 26 (Fig. 6A) is a single frontal which is smaller than those described for Sakurasaurus,
895 6 - Lizard B, Okurodani Formation, Japan. Skull roofing elements in dorsal view. A, frontal, small arrows mark posterior limits of prefrontal facets; B, parietal. Scale bar = 1 mm. Osse-
FIGURE
Jk
ments clu toit crgtnien en vue dorsale; A, frontal; les fl~ches indiquent la limite postdrieure des facettes prgfrontales; B, paridtal.
pf
FICURE 7 - Lizard C, Okurodani Formation, Japan. Partial left dentary in lateral view. Dentaire gauche incomplet, rue latdrale.
b u t w h e r e left a n d r i g h t sides a r e f u s e d w i t h o u t a t r a c e of a midline s u t u r e . B e t w e e n the orbits, the bone is slightly w a i s t e d . A n t e r i o r l y t h e r e are facets a n d processes as in I B E F VP 18 a n d 25, b u t the a r r a n g e m e n t is different - t h e l a t e r a l a n d m e d i a n processes a r e not as s t r o n g a n d the b o r d e r is less deeply incised. T h e p r e f r o n t a l facet is large a n d e x t e n d s well b a c k a l o n g t h e bone - a l m o s t to the point of m i n i m u m i n t e r o r b i t a l w i d t h - a n d t h e r e are deep oblique orbital flanges (cristae cranii) which e x t e n d f u r t h e r t o w a r d s t h e midline. I B E F VP 24 (Fig. 6B) is a complete parietal, preserved in dorsal view, which differs strikingly from I B E F VP 20. The surface is coarsely s c u l p t u r e d with a raised a r e a a r o u n d the central p a r i e t a l foramen. The l a t e r a l borders b e a r deep flanges indicating t h a t the u p p e r t e m p o r a l f e n e s t r a e were large and t h a t the a d d u c t o r m u s c u l a t u r e was not restricted to the v e n t r a l surface of the bone. The postparietal processes are long, d o r s o v e n t r a l l y deep, and ridged along the dorsal midline to create a strong
posterior surface for the neck muscles. There is no trace of the paired median processes seen in IBEF VP 20 and the frontoparietal suture also looks to be less imbricated. In addition, the bone is long - this animal had long open upper temporal fenestrae in strong contrast to those of IBEF VP 20. LIZARD
C
IBEF VP 21 is a relatively well preserved left dentary (lateral aspect) with eroded teeth (Fig. 7). It has a sharply tapering anterior symphyseal region deepening posteriorly. The rear of the bone is damaged but bears short dorsal and ventral processes. The dorsal process matches that of Sakurasaurus and many scincoids in which the dentary overlaps the coronoid. Laterally, the bone bears five neurovascular foramina, the anteriormost opening into a marked groove which runs to the tip of the jaw. The bone bears about 20 tooth positions but the teeth are all damaged. In general shape, IBEF VP 21 resembles
896 FIGURE 8 - Isolated s q u a m a t e right quadrate, Okurodani Formation, Japan, in A, lateral; B, posterior, * m a r k s position of f o r a m e n for chorda t y m p a n i nerve; and C, dorsal views. Scale bar = i m m . Carrd droit isolg, A, rue latdrale; B, vue postgrieure, C, rue dorsale.
A
sq
B
~
C
PP--
|
the dentary of Sakurasaurus, but the tapering anterior region is distinctive and appears to be indicative of a separate taxon. Without the dentition, however, it is difficult to be certain. Similarly, without further material, we are not in a position to judge whether the elements attributed to lizard B and lizard C might belong to a single taxon. NON-DENTAL LIZARD ELEMENTS
IBEF VP 27 (Fig. 8A-C) is a right quadrate. The medial border is damaged but appears to include the broken base of a small pterygoid lappet. The lateral conch is well developed and has a clear "tympanic" crest which is deeply notched dorsally and has a hooked posterior tip. In lateral view (Fig. 8A), the bone is seen to have a strongly overhanging posterodorsal process, which has a posterior articular surface (Fig. 8B) for the paroceipital process of the opisthotic and is deeply grooved laterally for the squamosal. In dorsal view (Fig. 8C), this posterior process is seen to be sharply demarcated from the rest of the bone. IBEF VP 23 (Fig. 9A-F) is a procoelous dorsal vertebra with a completely formed condyle and a strong zygosphene/zygantral system (seen most clearly in dorsal, Fig. 9D, and anterior, Fig. 9F, views). The centrum is flask-shaped like that of many scincomorphs and is ventrally ridged and grooved - not unlike the centrum of the Spanish Early Cretaceous lizard Meyasaurus (Evans & Barbadillo 1997). IBEF VP 22 is a partial conjoined pelvis, with the ilium and the proximal parts of the pubis and ischium (Fig. 10). The ilium has a long slender iliac blade, with a strong dorsal flange rising from a pronounced lateral ridge. There are no taxonomically useful characters except that the acetabular surface appears to lie well below the level of the sacral articulation - a possible scleroglossan state. DISCUSSION
D
E
I
SAKURASA UR US
FIGURE 9 - Squamate dorsal vertebra, Okurodani Formation, Japan, in A, left lateral view; B, ventral view; C, right lateral view; D, dorsal view; E, posterior view; and F, anterior view.
Although the remains attributable to Sakurasaurus are limited, there is enough information for
Scale bar = 1 r a m . Vert~bre dorsale, A, vue latdrale gauche; B, vue ventrale; C, vue latgrale droite; D, vue dorsale, E, vue postdrieure; F, vue ant~rieure.
897 FIGUR~ 10 - S q u a m a t e left pelvic girdle, lateral view. Scale b a r = l m m . Ceinture pelvienne gauche,
vue latdrale.
a general discussion of relationships. The deep subdental shelf, vermiculate skull ornament and clearly bifurcate postfrontal/postorbitofrontal argue for scleroglossan affinity (Estes et al. 1988). At the same time, the strong subdental shelf and iguanid type tooth replacement support scincomorph rather than anguimorph relationship. The heterodonty and centrally interdigitating frontoparietal suture are lacertoid features (lacertids, teiids, gymnophthalmids), but the absence of anterolateral parietal tabs is problematic. Similarly, while the absence of scale marks on the roofing bones and the heterodonty would be consistent with teioid affinity, as would the narrow curved premaxillary process of the maxilla, but Sakurasaurus lacks the typically teioid step in the maxillary tooth row (Estes et al. 1988). The strong posterodorsal coronoid process of the dentary is a scincoid character state (scincids, cordylids), and the median processes on the parietal and the posterior dentary process which overlaps the coronoid resemble those of some scincoids, but this is contradicted by the absence of descending parietal processes. We entered the character states of Sakurasaurus into a data matrix (31 terminal lepidosauromorph taxa, 259 character states: characters and main matrix published elsewhere, Evans & Barbadillo, in press a,b; Evans & Chure 1998). Using the heuristic search mode, Paup 3.1 yielded a single tree (length 492 steps, CI - 0.46; RI - 0.59) in which Sakurasaurus was positioned as the sister group to all other scincomorphs (i.e. scincids, cordylids, teiids, lacertids, xantusiids and gymnophthalmids). Clearly, with the very limited information available for Sakurasaurus, this is only a very provisionM result, but it does support scincomorph affinity. Excavations in the Okurodani Formation and its lateral equivalents are conti-
.-.-...~-..:~;:~.:~ ~ -
nuing and we may expect additional material to be found in due course. THE OTHER LIZARDS Lizard B is represented by fused frontals and parietals (if correctly associated). The shape of the frontoparietal region again suggests the presence of a strongly bifurcate postfrontal or postorbitofrontal a scleroglossan character state. Fused frontals occur in iguanians and teiids, and as a variable feature in other groups but the posterior position of the parietal foramen makes an iguanian unlikely (although the position in reversed in anoles), as does the apparently bifurcate structure of the postfrontal/postorbitofrontal. The upper temporal fenestrae were clearly widely open and the adductor muscles invaded the sides of the parietal. The parietal is long with extended posterior processes suggesting large upper temporal fenestrae as in iguanians and teiids, but the shape, the general pattern of the dermal sculpture, and the triangular interparietal shield region (Borsuk-Bialynicka 1984, Fig. 24) all resemble that of living anguids such as Anguis and Gerrhonotus. Frontal fusion and deep orbital flanges occur in many groups, but would also be consistent with an anguimorph, as would the long posterior orbital processes of the prefrontals (a feature of anguines and some gerrhonotines, Rieppel 1980). No clearly anguimorph jaw material has yet been found, however, and pending further specimens, lizard B remains incertae sedis, as does lizard C. CONCLUSIONS The lizards from the Okurodani Formation of the Tetori group in Gifu Prefecture represent some of the oldest lizard specimens in Japan. The only can-
898
didate for an older lizard specimen is the single specimen of Tedorisaurus, supposedly from the Late Jurassic Kuzuryu Subgroup of the Tetori Group, Fukui Prefecture (Shikama 1969). Unfortunately, this specimen is not available for study. Early Cretaceous lizard assemblages have now been recorded from Europe (Britain, Spain, Italy, Hoffstetter 1967; Richter 1994a,b; Evans & Barbadillo 1997), North (Winkler et al. 1990), South (Evans & Yabumoto 1998) and Central America (Mexico, Reynoso 1995, 1998), Africa (Morocco, Richter 1994a, Broschinski & Sigogneau-Russell 1996), and Asia (Mongolia, China - Alifanov 1989a, 1993; Endo & Shikama 1942). Few of these lizards are known in any detail (exceptions are those from Mexico and Spain) and none show a marked resemblance to those from Shokawa. Recently, however, new lizard material has been recovered from a locality at Shiramine, Ishikawa Prefecture, Japan, in a horizon roughly contemporaneous with that at Shokawa. Although work on this material is still in progress, the Shiramine material includes paramacellodids, a group of scincomorphan lizards with an almost global distribution in the Jurassic and Early Cretaceous (Evans & Chure 1998). The new Japanese material thus adds to our general knowledge of lizard diversity in the Early Cretaceous, and specifically to our understanding of Asian lizard assemblages in the Mesozoic. This is important. As a result of the extraordinarily rich finds of Late Cretaceous lizards made by the Polish-Soviet, American M u s e u m of Natural History, and Institute of Vertebrate Palaeontology and Palaeoanthropology expeditions to Inner and Outer Mongolia over the last thirty years, we will soon have an unprecedented knowledge of Late Cretaceous lizard diversity (iguanians, scincomorphs, anguimorphs) in Asia (Sulimski 1972, 1975; Borsuk-Bialynicka 1984, 1985, 1988; Borsuk-Bialynicka & Moody 1984; Alifanov 1989b; Borsuk-Bialynicka & Alifanov 1991; Gao & Hou 1992, 1995, Keqin Gao, pers.comm.1997). As yet, however, we know relatively little about the earlier Asian assemblages from which they arose, and this must form a priority in future work. A c k n o w l e d g e m e n t s - We are indebted to the fossil collectors of Shokawa - Mr Shibata, Mr Shimizu, Mr Ohkura, and Mr Shimojima for finding and preparing the material described here, for making it available to us for study, and for their willingness to deposit it in regional museums. The Mayor and Administration of Shokawa Village, Gifu Prefecture, Japan, have been generous in their hospitality and support. We are also grateful to Dr Keqin Gao for discussions about lizard material from China and Central Asia. Drs Liz Cook and Chris Nicholas shared with us the results of their work on the taphonomy and geology of the KO2 locality. Dr Denise Sigogneau-Russell (Paris) was kind enough to help with the French abstract, and we are grateful to Dr J.-C. Rage (Paris) and Dr P.A. Murry (Texas) for
suggesting improvements to the text. The text figures were mostly drafted by Aysha Raza (UCL). This work was funded by the Royal Society/British Council/Japanese Society for the Promotion of Science Joint Research Projects Program.
REFERENCES AL1FANOVV.R. 1989a - The oldest gecko (Lacertilia: Gekkonidae) from the Lower Cretaceous of Mongolia. Paleontological Journal, 23: 128-131. ALIFANOVV.R. 1989b - New priscagamids (Lacertilia) from the Upper Cretaceous of Mongolia and their systematic position a m o n g I g u a n i a . Paleontological Journal, 1989: 68-80. ALIFANOVV.R. 1993 - Some peculiarities in the Cretaceous and Palaeogene lizard faunas of the M o n g o l i a n People's Republic. Kaupia, 3: 9-13. AZUMA Y. • TOMIDAY. 1995 - Early Cretaceous dinosaur fauna of the Tetori Group in Japan. In AILING SUN & YUANQING WANO (eds), Sixth Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short papers, 125-131. China Ocean Press, Beijing. BORSUK-BIALYN1CKA M. 1984 - Anguimorphans and related
lizards from the Late Cretaceous of the Gobi Desert, Mongolia. Palaeontologia Polonica, 46: 5-105. BO~SuK-B~ALYNtCKA M. 1985 - Carolinidae, a new family of xenosaurid-like lizards from the Upper Cretaceous of Mongolia. Acta Palaeontologica Polonica, 30: 151-176. BORSUK-BIAL~ICKA M. 1988 - Globaura venusta gen. et sp. nov. and Eoxanta lacertifrons gen. et sp. nov. - non-teiid lacertoids from the Late Cretaceous of Mongolia. Acta Palaeontologica Polonica, 33: 211-248. BORSUK-BIALYNICKA M. & ALIFANOV V.R. 1991 - First Asiatic 'iguanid' lizards in the Late Cretaceous of Mongolia. Aeta Palaeontologica Polonica, 36: 325-342. BORSUK-B;ALYNIC~(A M. & MOODY S.M. 1984 - Priscagamidae, a
new sub-family of the Agamidae (Sauria) from the Late Cretaceous of the Gobi Desert. Acta Palaeontologica
Polonica, 29: 51-81. BROSCHINSKI A. & SIGOGNEAU-RUSSELL D. 1996 - Remarkable lizard remains from the lower Cretaceous of Anoual (Morocco). Annales de Paldontologie (Vert.-lnvert.) , 82: 147-175. CLUZELD. & CADETJ-P. 1992 - Geodynamic evolution of Korea: a view. The IslandArc, 1: 64-70. Cook E., ISAJI S. & MANABE M. 1998 - Preliminary results of a t a p h o n o m i c s t u d y of a vertebrate accumulation from the Tetori G r o u p (Lower Cretaceous) of Japan. Paleontological Research, 2: 47-52. ENDO R. & SHII~MA T. 1942 - Mesozoic reptilian fauna in the Jehol mountainland, Manchoukuo. Bulletin of the Central National Museum, Manchoukuo, 3, 12 p. ESTES R., GAUTHI~RJ. & DE QUEIROZK. 1988 - Phylogenetic relationships within Squamata. In EST~S R. & PREGILL G. (eds), Phylogenetic Relationships of the Lizard Families: Essays commemorating Charles L. Camp. Stanford: Stanford University Press: 119-281. EVANS S.E. 1993 - Jurassic lizard assemblages. Revue de Paldobiologie, Vol. Sp., 7: 55-65. EVANS S.E. & BARBADILLOL.J. 1997 - Early Cretaceous lizards from los Hoyas, Spain. Zoological Journal of the Linnean Society, 119: 23-49. EVANS S.E. & BARBADILLOL.J. 1998 - An u n u s u a l lizard from the Early Cretaceous of Las Hoyas, Spain. Zoological Journal
of the Linnean Society, 124: 235-265. EVANS S.E. & BARBADILLOL.J. 1999 - A short-limbed lizard from the Early Cretaceous of Spain. Special Papers in Palaeon-
tology, 60: 73-85. EVANS S.E. & CHURE D.C. 1998 - Paramacellodid lizard skulls from the Jurassic Morrison Formation at Dinosaur Natio-
899 nal Monument, Utah. Journal of Vertebrate Paleontology, 18: 99-114.
EVANS S.E., MANABE M., COOK E., HIRAYAMA R., ISMI S., NmHOLAS C.J., UNWIND. • YABUMOTO Y. 1998 - An Early Cretaceous assemblage from Gifu Prefecture, Japan. Bulletin of the
New Mexico Museum of Natural History, 14: 183-186. EVANS S.E. • YABUMOTO Y. 1998 - A lizard from the Early Cretaceous Crate Formation, Araripe Basin, Brazil. Neues Jahrbuch fi~r Geologic und Paliiontologie, 1998 (6): 349-364. FAUREM.& CHARVETZ. 1987 - Late Permian/early Triassic orogeny in Japan: piling up ofnappes, transverse lineation and continental subduction of the Honshu block. Earth and Planetary Science Letters, 84: 295-308. GAO K-Q, & Hou L-H. 1992 - Fossil lizards from the Upper Cretaceous Djadochta Formation, the Gobi Desert of China. Journal of Vertebrate Paleontology, 12: 29A. GAO K-Q. & Hou L-H. 1995 - Iguanians from the Upper Cretaceous Djadochta Formation, Gobi Desert, China. Journal of Vertebrate Paleontology, 15: 57-78. GAO K-Q. & NESSOVL.A. 1998 - Early Cretaceous squamates from the Kyzylkum Desert, Uzbekistan. Neues Jahrbueh f~tr Geologie und Pal(tontologie, 207: 289-309. GIFU-KEN DINOSAURRESEARCH COMMITEE 1993 - Report on the dinosaur fossil excavation in Gifu Prefecture, Japan. Gifu. 46 p, Gifu Prefectural Museum [in Japanese]. Gr~ADSTEN F.M., ACTER~RRG F.P., eGG J.G., HARDENBOLJ., VAN VEEN P., THIERRY J. & HUANG Z. 1995 - A Triassic, Jurassic and Cretaceous time scale. In BERGGRENW.A., KENT D.u AUBRY M.P. & HARDENEOL J. (eds), Geochronology Time
Scales and Global Stratigraphic Correlation, SEPM (Society for Sedimentary Geology) Special Publication, 54: 95-126. Tulsa, Oklahoma.
HARLAND W.B., ARMSTRONG
R.L., COXA A.V., CRAIG L.A., SMITH
A.G. & SMITH D.G. 1990 - A geologic timescale 1989, 263 p. Cambridge University Press, Cambridge.
HAS~AWA Y., MANABE M., I~AZl S., OI{KURA M., SmRATA I. & YAMAGUCHI I. 1995 - Terminally resorbed iguanodontid teeth from the Neocomian Tetori Group, Ishikawa and Gifu Prefecture, J a p a n . Bulletin of the National Science Museum, Series C (Geology & Paleontology), 21: 35-49. HOFFSTETTER R. 1 9 6 7 - Coup d'oeil sur les Sauriens (=lacertiliens) des couches de Purbeck (Jurassique sup6rieur d'Angleterre. R6sum6 d'un M6moire). Colloques Inter-
nationaux du Centre National de la Recherche Scientifique, 163: 349-371. ISOSAKIY. 1996 - Anatomy and genesis of a subduction-related orogen: a new view of geotectonic subdivision and evolution of the Japanese Islands. The IslandArc, 5: 289-320. MAEDA S. 1961 - On the geological history of the Mesozoic Tetori Group in Japan. Journal of the Collections of Arts and Science, Chiba University 3:369-426 [in Japanesel MANABEM.& HASEGAWAY. 1995 - Diapsid fauna and its palaeobiogeographical implication; the Neocomian section of the Tetori Group, Japan. In SUN A-L. & WANGY-Q. (eds), Sixth
Symposium on Mesozoic Terrestrial Ecosystems and Biota, Short papers, 179. China Ocean Press, Beijing. MATSUKAWAM., KAWASHIMAK. & KOARAIK. 1996 - Nonmarine molluscan assemblages in the middle p a r t of the Tetori Group (Upper J u r a s s i c to Lower Cretaceous), Gifu Prefecture, central Japan. Bulletin of the Tokyo Gakugei University Section, 4 48:101-113 [in Japanese with English abstract].
NESSOVL.A. 1997 - Cretaceous nonmarine vertebrate~ofNorthern Eurasia. University of Saint-Petersburg, Institute of Earth Crust. 217 p + 60 pl. St Petersburg, Russia [in Russianl. NICHOLASC.J., In press - Geology of the Shokawa vertebrate beds in the Jurassic-Cretaceous Tetori Group, Gifu Prefecture, Japan. Journal of the Geological Society of Japan. OTSU~a K. 1992 - Oblique subduction, collision of micro-continents and subduction of oceanic ridge: their implications on the Cretaceous tectonics of Japan. The Island Arc, 1: 51-63. REYNOSO V.H. 1995 - Lepidosaurian reptiles from the Cantera Tlayua (Albian), Tepexi de Rodriguez, Puebla, Mexico. Second
International Symposium on Lithographic Limestones, Lleida-Cuenca (Spain), Extended Abstracts, 131-132. Ediciones de la Universidad Aut6noma de Madrid, Spain. REYNOSOV.H. 1998 - HuehuecuetzpaUi mixtecus gen. et sp. nov.: a basal squamate (Reptilia) from the Early Cretaceous of Tepexi de Rodriguez, Central Mexico. Philosophical Transactions of the Royal Society, (B), 353: 477-500. RICHTERA. 1994a - Der probSlematischer Lacertilier Ilerdaesau. rus (Reptilia: Squamata) aus der Unter-Kreide von Ufia und Galve (Spanien). Berliner geowissenschaftliche Abhandlungen, 13: 135-161. RICHTERA. 1994b - Lacertilier aus der Unteren Kreide von Ufia und Galve (Spanien) und Anoual (Marokko). Berliner geowissenschaftliche Abhandlungen, 14,147 p. RIEPPEL O. 1980 - The phylogeny of anguimorph lizards. Denk-
shriflen der Schweizerischen Naturforschenden Gesellschaft, 94: 5-86. SHIKAMA W. 1947 - Teilhardosaurus and Endotherium, new Jurassic Reptilia and Mammalia from the Husui Coalfield, South Manchuria. Proceedings of the Japanese Academy, 23: 76-84. SHIKAMA W. 1969 - On a Jurassic reptile from Miyama-cho, Fukui Prefecture, Japan. Science Reports of Yokohama National University, Section 2, 15: 25-34. SULIMSKIA. 1972 - Adamisaurus magnidentatus nov. gem, nov. sp. (Sauria) from the Upper Cretaceous of Mongolia. Acta Palaeontologia Polonica, 27: 33-40. SULIMS~ A. 1975 - MacrocephMosauridae and Polyglyphanedontidae (Sauria) from the Late Cretaceous of Mongolia. Acta Palaeontologia Polonica, 33: 25-102. TAZAMI M. & ITAYAT. 1996 - Episodic accretion and metamorphism of Jurassic accretionary complex based on biostratigraphy and K-Ar geochronology in the western part of the MinoTamba Belt, Southwest Japan. The Island Arc, 5: 321-336. WINKLER D.A., MURRYP.A. & JACOBS L.L. 1990 - Early Cretaceous (Comanchean) vertebrates of central Texas. Journal of Vertebrate Paleontology, 10: 95-116. "fANG Z., CHENG Y. & WANG H. 1986 - The Geology of China. Oxford Monographs in Geology and Geophysics, 3, 303 p. Oxford, Clarendon Press. S.E. EVANS
Department of Anatomy and Developmental Biology University College London Gower Street G.-B., London WCIE 6BT M. MANABE National Science Museum 3-23-1 Hyakunin-Cho, Shinjuku-Ku Tokyo 169-0073, J a p a n