541 Sineoamphisbaena hexatabularis, an amphisbaenian (Diapsida: Squamata) from the Upper Cretaceous redbeds at Bayan Mandahu (Inner Mongolia, People's Republic of China), and comments on the phylogenetic relationships of the Amphisbaenia

Xiao-Chun Wu, Donald B. Brinkman, and Anthony P. Russell

Abstract: Sineoamphisbaena hexatabularis Wu et al., 1993 is the earliest known amphisbaenian represented by well-preserved cranial and postcranial material. It reveals a mosaic of generalized lizard-like features and amphisbaenian characters. Most distinctive of the latter are features of cranial consolidation adaptive for a fossorial way of life. Phylogenetic analyses strongly confirm the monophyly of the Amphisbaenia inclusive of S. hexatabularis. The Amphisbaenia is diagnosed by a suite of apomorphic characters. The available evidence suggests a probable Amphisbaenia-Macrocephalosauridae relationship within the Scincomorpha. This is supported primarily by the unique modifications of the palate and temporal region of the skull. It is argued here that the Amphisbaenia evolved in Central Asia during the Cretaceous, in response to the transition from a perennial lacustrine environment to a dry, semiarid eolian environment. The relatively primitive morphology indicates that S. hexatabularis was not permanently subterranean. The further derived modifications of later forms are associated with tunneling in an environment of more compact soils.

RCsumC : Le plus ancien amphisbenien connu, reprtsentC par du mattriel crdnien et postcrinien bien prCservC, est Sineoamphisbaena hexatabularis Wu et al., 1993. I1 montre un assemblage de traits generaux appartenant aux lCzards et des caractkres d'amphisbCniens. Ce qui distingue le plus ces derniers, ce sont les particularitCs qui consolident l'adaptation du crine au mode de vie de reptile fouisseur. Les analyses phylogCnCtiques confirment largement la monophylie des Amphisbaenia incluant S. hexatabularis. Les Amphisbaenia sont identifiCs par un ensemble de caractbres apomorphiques. Les donnees disponibles suggbrent un rapprochement probable des Ampbisbaenia-Macrocephalosauridae a I'intCrieur des Scincomorphes. Ce qui est CtayC principalement par les modifications uniques du palatin et de la rtgion temporale For personal use only. du crine. I1 est suggCrC ici que les Amphisbaenia ont CvoluC en Asie centrale durant le CrCtacC, en rkponse a la transition d'un milieu lacustre stable depuis longtemps vers un milieu sec, semiaride et Colien. La morphologie relativement primitive indique que S. hexatabularis ne vivait pas en permanence sous terre. Les modifications dCrivCes ulterieures des formes plus tardives sont associCes au creusement de tunnels dans un milieu constituC de sols plus compacts. [Traduit par la rCdaction] Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11

Received February 8, 1995. Accepted December 13, 1995. X.-C. Wu.' Vertebrate Morphology Research Group, Department of Biological Sciences, The University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada, and Institute of Vertebrate Paleontology and Paleoanthropology, Academia Sinica, P.O. Box 643, Beijing 100044, People's Republic of China. D.B. Brinkman. Royal Tyrrell Museum of Palaeontology, P.O. Box 7500, Drumheller, AB TOJ OYO, Canada. A.P. Russell. Vertebrate Morphology Research Group, Department of Biological Sciences, The University of Calgary, 2500 University Drive NW, Calgary, AB T2N 1N4, Canada. ' Corresponding author (e-mail: rtmp@dns .magtech.ab. ca) .

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Fig. 1. (A) Regional locality map of the Gobi Basin showing the location of the Bayan Mandahu. (B) Localities of fossil vertebrates near the Bayan Mandahu seasonal herb station. The specimens of Sineoamphisbaena hexatabularis were collected from bedrock near the North Canyon site. Solid lines indicate ephemeral drainage. Modified from Figs. 1 and 3 of Jerzykiewicz et al. (1993). For personal use only.

{ To Urad Hou Qi

amphisbaenian. Its relative primitiveness provides insights nized within the redbeds (Fig. lB), representing a proximal- into the morphology, early history, and evolution of the to-distal depositional gradient from the "Paleo" Lang Shan Amphisbaenia. In the present paper, we first describe the in the south to an extensive sand sea in the north (Eberth osteological anatomy of S. hexatabularis, and then reevalu- 1993). The amphisbaenian specimens studied here were col- ate previous hypotheses of the phylogenetic relationships of lected from zone 3, in which protoceratopsian and ankylo- the group as well as discuss its origin and early adaptation. saurian (Pinacosaurus) dinosaurs are dominant, and dinosaur eggs, lizards, and mammals are common. Zone 3 is inter-

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Geological setting preted as the southern margin of an extensive sand sea and is characterized by a large number of eolian dune deposits, The Bayan Mandahu redbeds are well exposed about 50 km but also contains structureless deposits and rare lacustrine northwest of the Lang Shan mountain range (Fig. 1). The deposits (Eberth 1993). redbeds are essentially flat lying (with a regional dip < 3" W) and outcrop along a 12 km, north-south-trending escarp- Materials and methods ment, about 8 km north and slightly east of the Bayan Mandahu seasonal shepherd station. The entire stratigraphic The two available specimens were both collected in the thickness of the Bayan Mandahu redbeds unit is unknown. North Canyon area (Fig. 1B). The articulated skeleton was Jerzykiewicz et al. (1993) interpreted the redbeds as chrono- preserved in a natural posture and reported as an embryonic stratigraphically equivalent to the Djadokhta Formation of ankylosaur in the popular literature (Cui 1991). This skeleton south-central Mongolia, which is regarded to be Campanian consists of the skull without the mandible, associated first in age (Lillegraven and McKenna 1986; Jerzykiewicz and 19 vertebrae with 11 (right) and 10 (left) ribs, the left Russell 1991). Three coeval sedimentary zones are recog- pectoral girdle with the humerus, the distal portion of the 544 Can. J. Earth Sci. Vol. 33, 1996

Fig. 2. Holotype specimen of Sineoamphisbaena hexatabularis (IVPP V10.593 (= V10593-I, Wu et al. 1993)) in (A) dorsal and (B) ventral views. For personal use only.

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 right humerus and part of the right coracoid, and the placed ventrally. The ramus is missing its retroarticular posterior portion of the interclavicle (Fig. 2). The cranium process, and the ventral edge of its dentary is damaged. is missing the anterior tip of the snout, and its occipital The specimens are housed in the Institute of Vertebrate surface is slightly damaged. The neural arch is incomplete Paleontology and Paleoanthropology (IVPP), Academia and the ribs are not preserved on vertebrae 3 -7. Most of the Sinica, Beijing, People's Republic of China. According to ribs are represented by their proximal portion. The second the regulations of IVPP, different individuals of a species specimen, an isolated skull, was picked up from the surface should not share the same accession number, even if they (Fig. 3). The dermal roof elements of its cranium are heavily have been collected from the same locality. Therefore, the eroded, exposing the brain cavity, exaggerating the size of specimen number of the holotype has been changed to IVPP the external nares, and creating a pair of holes on the fron- V10593 (= V10593-1, Wu et al. 1993) and that of the para- tals. In addition, the cranium is missing its palatal elements type has been changed to IVPP V10612 (= V10.593-2, Wu and occipital condyle. The ventral surface of the braincase is et al. 1993). Specimens of many living and fossil amphis- broken, and its left quadrate has shifted anteromedially. The baenians were examined for comparative purposes and the postdentary portion of the left rarnus of the mandible is dis- generation of the data matrix for the phylogenetic study; Wu et al.

these were obtained from Pratt Museum of Arnherst College Fig. 3. Stereophotographs of the skull of the paratype of (ACM); American Museum of Natural History (AMNH); Sineoamphisbaena hexatabularis (IVPP V10612 (= V10593-2, Carnegie Museum of Natural History (CMNH); Museum of Wu et al. 1993)) in (A) dorsal and (B) ventral views. Comparative Zoology, Harvard University (MCZ); Univer- sity of California Museum of Paleontology, Berkeley (UCMP); University of Kansas Museum of Natural History (UKMNH); University of Michigan Museum of Paleon- tology (UMMP); and United States National Museum of Natural History (Smithsonian Institution) (USNM). Data for other squamates come mainly from the literature, but speci- mens of some living lizards and snakes in the collections of the Royal Tyrrell Museum of Palaeontology (RTMP) have been examined.

Systematic paleontology

Lepidosauromorpha Gauthier et al., 1988 Lepidosauriformes Gauthier et al., 1988 Lepidosauria Haeckle, 1866 Squamata Oppell, 181 1 Amphisbaenia Gray, 1844 Sineoamphisbaena hexatabularis Wu et al., 1993

Description Reconstructions of skull and general features (Fig. 4) The premaxilla, anterior portions of the nasals and maxillae, and nares are restored on the basis of the paratype, IVPP V10612. The remaining dermal elements of the cranial roof are preserved in the holotype, IVPP V10593. In ventral view, all palatal elements are preserved in the holotype, but are slightly displaced posteriorly, separating the basisphenoid - pterygoid and pterygoid -quadrate contacts and compressing the elements of the palate on the left side. The medial process For personal use only. of the palatal ramus of the pterygoid has been restored on the basis of its presence in most amphisbaenians and the pattern of breakage in the original specimen. The dentition of the upper jaw is well preserved in the paratype. The anterior- most portions of the vomers were restored based upon a com- mon pattern in other amphisbaenians. All elements of the left ramus of the paratypic mandible are present. The skull is relatively short, with a length of about 2.5 cm, or 2.4 cm as measured from the tip of the snout to either the posterior end of the otic bulge, or the end of the occipital slopes anteroventrally. The infratemporal fenestra is lizard- condyle, respectively. Extensive fusion of cranial elements like, but is posteriorly bordered by the squamosal rather than suggests that the two type specimens were adults. the quadrate. The otic capsule is greatly enlarged, projecting The dermal cranium is wider than long. The cranium posteriorly beyond the occipital condyles. In occipital view, shows no postorbital elongation and no spade-like or keeled the foramen magnum is pear-shaped, the occipital condyle Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 specialization of its snout. In dorsal view, the cranial roof is double, and the posttemporal fenestra closed. The mandible characterized by a hexagonal table between the orbits, which is robust and deep. The neck is short, and the body is flat and is distinctly elevated and rugose, being covered by vermicu- probably elongated. The forelimb and pectoral girdles are late sculpturing and a few large tubercles. The external naris well developed. No additional zygospheno-zygantral articu- is subterminal in position. The orbit is complete, but faces lations are present in the preserved vertebrae. posterolaterally. The supratemporal fenestra and upper tem- The description below is based on the holotype, unless poral arcade are retained, although the former is very small otherwise indicated. and the latter is broad. In ventral view, the basipterygoid processes are widely separate. The vomers are also widely Dermal bones of cranial roof divergent posteriorly. Thus, the interpterygoid vacuity is The almost complete premaxilla of the paratype is an unpaired, both wide and long. Anteriorly, the upper jaw forms a broad, triangular bone in dorsal view (Figs. 5A, 5B). It bears a short lip-like rim around the tooth row. In lateral view, the dorsal process that wedges between the nasals. Ventrally, the cranium has a relatively deep profile. The interorbital table bone is distinctly stepped, because the labial portion lateral 546 Can. J. Earth Sci. Vol. 33, 1996

Fig. 4. Sineoamphisbaena hexatabularis, composite skull reconstructions in (A) dorsal, (B) ventral, and (C) lateral views. a, angular; ar, articular; bo, basioccipital; bs, basisphenoid; d, dentary; ec, ectopterygoid; epi, epiphysial ossification; m, maxilla; n, nasal; cor, coronoid; f, frontal; j, jugal; 1, lacrimal; opt, opisthotic; os, orbitosphenoid; p, parietal; pf, prefrontal; pl, palatine; pm, premaxilla; porn postorbital complex; pof, post-frontal complex; pr, prootic; pt, pterygoid; q, quadrate; so, supraoccipital; sq, squamosal; st, stapes; vo, vomer; vpf, ventral premaxillary foramen; IX, cranial nerve 9; X-XI, cranial nerves 10 and 11. For personal use only. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11

to the tooth row is broadened to form a rim-like structure medially, the septomaxilla ventrally, and the premaxilla along the oral margin. The premaxilla -vomer contact is not anteromedially. preserved. The septomaxillae, missing their anterior ends, form a The nasal is much broader posteriorly than anteriorly shelf between the naris and the space for Jacobson's organ (Figs. 5A, 5C, 6A-6C). The anterior end of the nasal of the (Figs. 6A - 6C). Each septomaxilla is broad anteriorly and paratype bends strongly downward and contacts the maxilla tapers to a point posteriorly. Both dorsal and ventral surfaces along its ventrolateral edge, separating the premaxilla from of the bone are concave. The septomaxilla meets its opposite the naris. Posteriorly, the nasal forms the anterior portion of along the midline, the maxilla laterally, and the vomer ven- the interorbital table and broadly contacts the prefrontal and trally. The preserved portion shows that the septomaxilla frontal. Sutures between these bones are not strongly inter- excludes the maxilla from the space for Jacobson's organ. digitated. Viewed through the external nares, each nasal However, it is uncertain whether the maxilla enters the bears a lamina-like ventral Drocess. which contacts its mate anteriormost border of this mace. Wu et al. 547

Fig. 5. Skulls of Sineoamphisbaena hexatabularis in (A, C) dorsal and (B, D) ventral views. (A, B) Paratype skull (IVPP V10612). (C, D) Holotype skull (IVPP V10593). eo, exoccipital; fo, fenestra ovalis; hy, fragment of hyoid; jb, opening for Jacobson's organ; nat, fragment of neural arch of atlas; sm, septomaxilla; 11, V, and VII, cranial nerves 2, 5, and 7. Other abbreviations as in Fig. 4. For personal use only. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11

The maxilla bears an interlocking contact at its suture with process is tall and narrow. It forms the posterior border of the premaxillary (Fig. 5A). Dorsal to this contact a dorso- the naris and meets the nasal anterodorsally. Thus, the naris medially facing, smooth-edged notch is present at the dorso- is enclosed by only the maxilla and nasal. Posterodorsally, medial edge of each maxilla. This notch forms part of the the maxilla is widely separated from the orbit by the ventral premaxillary foramen (sensu Rieppel 1978). The prefrontal-lacrimal complex. The lateral surface of the portion of the maxilla posteroventral to the naris is dorso- maxilla is strongly concave, because the dorsal portion turns ventrally deep, but is extensively overlapped by the dorsolaterally and overhangs the ventral portion (Figs. 5B, prefrontal-lacrimal complex dorsally and the jugal poster- 5D). The maxillary portion of the rim-like structure along iorly (Figs. 6A - 6C). Superficially, therefore, the dorsal the oral margin becomes narrow posteriorly. Medially, the 548 Can. J. Earth Sci. Vol. 33, 1996

Fig. 6. Holotype skull of Sineoamphisbaena hexatabularis (IVPP V10593) in (A) lateral, (B) frontal, (C) lateral and slightly dorsal, and (D) occipital views. Abbreviations as in Figs. 4 and 5. For personal use only.

maxilla-ectopterygoid suture can be identified, but the lacrimal foramen is typically situated between the prefrontal maxilla-vomer contact is not preserved. and maxilla, or between the prefrontal and jugal, and is Each frontal is an irregularly pentagonal bone in dorsal largely exposed laterally in lepidosaurians that do not have view (Fig. 5C). It contacts the nasal anteriorly, the prefrontal- the lacrimal, such as Dibamus novaeguineae (Rieppel 1984), lacrimal complex anterolaterally , the postfrontal -postorbital Sphenodon punctatus (Carroll 1988), Amphisbaena alba complex posterolaterally, the parietal posteriorly, and its (MCZ 59244), Heloderma sp. (RTMP T-26), and Spatho- mate medially. The frontals form a hexagonal plate that is rhynchus fossorium (USNM 26317). Where a lacrimal is much wider than long and occupies the central portion of the present, the lacrimal foramen is located within the lacrimal interorbital table. Ventrally, the sutures between the frontal or between the lacrimal and prefrontal, and is not visible and adjacent bones are largely obscured by fusion, so it is laterally. The lacrimal foramen in S. hexatabularis is deep uncertain how large the descending process of the frontal is. and located on the medial surface of the prefrontal, a position Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 However, the anterior portion of the descending process can similar to that of the lepidosaurians that have a lacrimal. This be observed through the naris. It is transversely thick and suggests that the prefrontal here includes the lacrimal in extends ventrally below the space for the olfactory bulb fusion. The sutural pattern of the bone with the neighbouring (Fig. 6B). In ventral view, a triangular region just anterodor- elements, as described below, also indicates that the prefron- sal to the orbitosphenoid is identified as the ventromedian tal and lacrimal are fused. connection of the descending processes of the frontals below In dorsal view, the prefrontal -lacrimal complex is broader the olfactory tracts (Figs. 5B, 5D). It is morphologically anteriorly than posteriorly. It forms the anterolateral portion identical to that of living forms (such as Amphisbaena alba of the interorbital table. The dermal rugosity of the bony (MCZ 54299)) and appears to be partially sutured along the complex strengthens the pronounced anterolateral border of ventral midline. the table, which extensively overhangs the oral margin The fusion of the prefrontal and lacrimal is indicated by (Figs. 5B, 5D). In lateral view, the bony complex is also the position of the lacrimal foramen and the relationships of broad and is more or less vertical in orientation and rectangu- the bones to their adjacent elements (Figs. 5C, 6C). The lar in appearance (Fig. 6A). It borders the anterior half of the orbit. Similar to the maxilla, its lateral surface is concave and the orhit. The posterodorsal rarnus of the jugal contacts faces anterolaterally. Within the orbit, the bony complex is extensively the postfrontal - postorbital complex dorsally as fully hsed with the frontal. it extends posteriorly along the anterior two thirds of the The postfrontal and postorbital are also considered to be supratemporal arcade. The posteroventral ramus is missing fused with one another (Figs. 5C, 6A, 6C). The fusion of its posterior end. This ramus is free posteriorly and, if com- these elements is indicated l~ythe relationships of this com- plete, may have reached the level of the articular condyle of plex to the adjacent elements, which resemble those of the the horizontally oriented quadrate. two bones in other lepidosaurians, including both a contact The squamosal, with a broad dorsal end and a sharply with the prefrontal along the dorsal edge of the orbit and a pointed ventral extremity. forms not only the posterolateral contact with the parietal. both anterior and posterior. to the margin of the dermal cranium but also the posterior border supratemporal fenestra. of rhe infratemporal fenestra (Figs. 6A, 6C. 6D). Anteroven- Anterodorsally. the postfrontal - postorbital complex forms trally, the squamosal caps the cephalic head of the quadrate. the posterolateral portion of the interorbital table. As in the Posteroventrally, it sits against the otic capsule. In occipital anterolateral border of the table, the dermal rugosity of the view, the dorsonledial portion of the squamosal is largely complex exaggerates the posterolateral border of the table, overlapped by the supratenlpcrral process of the parietal. which expands laterally and overharys the postorbital bar. Posteriorly , the cornplcx becomes smooth and is distinclly Palatoquadrate and stapes inser below the surface of the bone. It approaches rhe pos- The quadrate. the only ossification of the palatoquadrate, is terior edge of the dermal roof of the cranium and forms the a horizontally oriented. stout. massive bone (Figs. SD. 6A, major portion of the broad and ventrolaterally inclined supra- 6C). In lateral view, this hone is triangular. Its proximal temporal arcade. The posternmedial portion of the con~plex head is large and angled dorsally. It is supported by the otic encloses the anterior half of the supratemporal fenestra and capsule posterornedially. The lateral surface of the quadrate contacts the parietal both anteromedial and posterolaterai to does not bear a foramen and is, except for its ventral edge. the fenestra. This excludes the squamosal from rhe supra- strongiy excavated to form n concave area for the attachment temporal fenestra. Laterally. the compkx hrders the of jaw muscles. The mandibular condyle of the quadrate is posterodorsal rim of the orbit. It is excluded by the jupl and transversely widened by a medial extension and is much squamosal From the infratemporal fenestra lateroventrally. smaller than the proximal head. The articular surfxe of the The parietal is the largest bone of the cranial roof quadrate condyle is also concave. The ventral surface of the (Fig. 5C). Its anterior ponion is elevated and forms the quadrate is convex, but it is occupied by a shallow depression posterior portion of the interorbital table. Each parietal has in the paratpe (Fig. 93). The ventromcdial margin of the a very strongly developed rugosity that lies along the quadrate is strongly notched for receipt of the shafr of posterior horder of the interorbital table. A median ruyosiry the stapes. An articular facet for the quadrate ramus of the 1s also pronounced and is situated at the anreriarmost cnd of prerygoid occupies the anterior half of the ventromedial the interparietal suture. The posterior half of the parietal 1s wrbce.

For personal use only. much wider than the anterior half and has a smooth dorsal The right stapes is preserved, but slightly displaced. in surface. Laterally. this portion border4 the posteromcdial both the holotype and paratype (Figs. SB, SD).The shaft of half of rhe supratemporal fenestra and has a depressed reginn the stapes is compressed in cross section. The footplate is inside the fenestra for the attachment of jaw muscles. massive, but incomplere in both specimens. The presence of Posteriorly. the supratemporal process of the hone is very a foramen for the stapedial artery at the base of the shaft can- slender and sharply pointed. This process extends laterally not be confirmed because of weathering. and anteroventrally, which results in a greatly broadened posterior border of the dermal roof of the cranlum. In occi- Dermal bones of palate pital view, the medial portion of the parietal is much deeper The palate is a large structure with its ventral surface strongly than the lateral portion. The parietals are fused t one concave. It is firmly attached to the ventral surface of the another in this region (Fig. 6D). A par of depressions on the braincase and bears no fencsaae. occipital portion marks the sites of the attachment of the neck Each vomer lacks its anterior end, and its anterolateral muscles. Anrerior to the supratemporal fenestra the parietal edge is incomplete (Fig. SD).The preserved ponion is trian- develops an anteroventral process that can be observed gular in outline. with a very narrow posterior end. The Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 through the orbit (Fig. 6C). This process is strong. but not strong psterolateral orientation of the bone results in a wide sheet-like. Ventrally, it is wedged hetween the orbito- space between the vomers. I! is likely that the vomers met sphenoid (plus thc fused descending process of rhe frontal) anlcriorly at the midline. although their preserved portions and prootic. The posterior horder of the frontal in the do not contact one another. The ventral surface of each paratype does not show the presence of the parietal tabs vomer is slightly convex. whereas the dorsal surface is con- (Fig. SA), which extend below the frontal in some lizards cave and floors rhe space for Jacobson's organ. The pre- (see Estes et al. 1988). served portion of the space is enclosed by only the vomer and The jugal is a triradiate bone, with s short but broad septomaxilla (Fig. 6B). The space becomes very narrow anterior ramus. an elongate posterodorsal ramus, and n small pusterinrly. In life it was probably closed by these two posteroventral ramus (Figs. 6A. 6C, 5C, 5D). Anteriorly. hones, dthough its posterior end IS incomplete, the jupal is arrow-shaped and wedges between the lacrimal The palatine is a broad. thin bone that l'orms the roof of portion of the prefmn~al-lacrimal complex and the maxilla. a very concave structure for the nasal passage (Figs. 5D,7). The jugal and the lacrimal ponion form the ventral hrder of Ir contacts the maxilla and ectopterygoid anterolaterally. Can. J. Earth Sci. Vol. 33, 1996

Fig. 7. Holotype skull of Sineoamphisbaena hexatabularis pterygoid medially. It is slightly damaged along its free (IVPP V10593) in ventrolateral view. vf, posterior foramen posterior margin. of vidian canal. Other abbreviations as in Figs. 4 and 5. Braincase The basioccipital is fused to the basisphenoid anteriorly (Figs. 5B, 5D). An epiphysial ossification ("bone X" of Zangerl 1944), which is present at the ends of the basioc- dpital-basisphenoid suture in other arnphisbaenians, is partially preserved on the left side of the paratypic skull. Posterior to the epiphysial ossification a distinct but weakly deveIoped spheno-occipital process is present. This process bends ventrally, so the ventraI surface of the basisphenoid is strongly concave. Posteriorly, the basioccipital becomes nar- row and forms the central portion of the occipital condyle. Posterolaterally, the extensive basioccipital-exoccipital suture is unfused. The basisphenoid is very broad anteriorly, because the baqipterygoid process is directed much more laterally than anteriorly (Figs. SB, 5D, 7). The parasphenoid cultriform process is incomplete in both the holotypic and paratypic skulls, but it appears to be short and narrow, as indicated by its preserved base. A shallow groove along the ventral mid- Iinc of the orbitosphenoid suggests that the pamphenoid cul- triforrn process may have extended anteriorly along with the entire length of the orbitosphenojd. The posterior portion of the basisphenoid is slightIy broader than the middle region. The lateral side of the middle region of the bone is deeply grooved and divided into a dorsolateral edge that meets the proatic and a ventrolateral edge that is free laterally. No suture between the basisphenoid and prootic can be deter- mined. A foramen present between the two lateral edges is probably the posterior opening of the vidian canal. The anterior opening of the canal is located on the anterodorsal extensively sutures with the lateral process of the palatal surface of the basisphenoid, just posterolateral to the base of For personal use only. ramus of the pterygoid posterolaterally, and is overlapped by the parasphenoid cultriform process. the vomer anteromedially. Anteriorly, the bone probably had The exoccipital is incompletely fused to the opisthotic. a sutural contact with the anterolateral portion of the vomer, The suture between these bones continues the exoccipital - although this is not preserved. The posteromedial margin of supraoccipital suture (Fig. 6D). In occipital view, the exoc- both palatines is incomplete. The holes in the palatines are cipitals form much of the lateral borders of the foramen breakages made during preservation. Both palatines meet the magnum and the ball-shaped, double occipital condyle ven- basipterygoid process, due to the posterior displacement of tromedially. A deep notch is present an each side lateral to the palate. the condyIe. The notch is frlled by a fragment of the atlas on The elongate pterygoid forms the posterior portion of the the right side and a fragment of the hyoid on the left side. palate (Figs. 5D, 7). The lateral process of its palatal ramus Thus, the foramen for cranial nerve MI, which should be is very strong and deeply wedged between the ectopterygoid present in this notch, cannot be seen. Far laterally, the and palatine, and entirely closes the suborbital fenestra. opisthotic portion of the exoccipital-opisthotic complex Anteromedially, the lateral process contributes to the nasal develops a pronounced buttress-like structure ventrally that passage. An additional small lateral process may be the rem- of Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 braces the proximal head the quadrate. Sutures between nant of the transverse flange of the pterygoid, judging from the opisthotic and proonc and between the opisthotic and its position and relationship with the ectopterygoid. The supraoccipital are clearly visible. In vcntral view, a round palatal ramus of the pterygoid most probably bore a medial depression is formed close to the exoccipital-basioccipital process along the medial margin of the palatine, as in other suture. This depression opens posteriorly (Figs. 5D,7). Two fossil and many living amphisbaenians. The incompleteness foramina lying at the bottom of the depression near its of the relevant regions of both the palatine and pterygoid anterior end are identified as the exits of cranial nerves IX suggests that the medial process was probably broken away (anterolateral foramen) and X (posteromedial foramen). In during excavation. The central portion of the pterygoid is this case, the fissure metaotica is subdivided, but the recessus relatively broad and articulates with the basipterygoid pro- scalae tympani (equal to the occipital recess of Oelrich 1956) cess. Posteriorly, the quadrate ramus of the pterygoid is is closed. Posterolateral to the depression the exoccipital short. As shown on the left side, this ramus tightly wraps bulges posteriorly into a weak prominence that forms the around the ventromedial surface of the quadrate. most posterior end of the cranium. Anterolaterally, the bone The stout ectopterygoid is narrow anteriorly and broad contributes to the posteromedial border of the fenestra posteriorly (Figs. 5D, 7), and braces the maxilla laterally and ovalis, but its suture with the prootic is obscured by fusion. Wu et al.

The supraoccipital is a large bone, forming much of the pronounced coronoid process posterior to the tooth row. It dorsal half of the occiput (Fig. 6D). Middorsally, the bone meets the surangular posteroventrally, but it is uncertain forms a U-shaped notch for receiving the deep median por- whether the bone is overlapped by the latter, because of dis- tion of the parietals. A weakly developed median ridge disap- placement. The preserved portion displays a depression for pears just dorsal to the foramen magnum. The lateral edges the attachment of jaw muscles on the posterodorsal portion of the bone are broadly wedged between the opisthotic par- of the lateral surface of the coronoid. tions of the exoccipitals and prootics. The ventral edge forms The surangular is broad posteriorly and probably tapers the narrow dorsal border of the pear-shaped foramen magnum. sharply to a point anteriorly. Posteriorly, it wraps around the The prootic is also very large, bulging on both lateral and dorsal and dorsolateral surfaces of the articular, but does not ventral surfaces (Figs. 6A, 6C, 5B, 5D, 7). A small portion extend posterior to the lateral border of the articular fossa. of the bone is exposed on the occiput, posterior to the dermal Ventrally, its suture with the angular parallels the ventral cranial roof. It extends anterolaterally under the supratem- edge of the mandible. A foramen is clearly present on the poral arcade and postorbital bar, suturing with the ventral posterolateral surface of the bone. process of the parietal anterodorsally. Anteroventrally , the The small triangular angular covers the ventrolateral sur- pleurosphenoid process (= the crista alaris, Rieppel 1981) of face of the articular and ends posteriorly slightly before the the prootic is short, and its suture with the orb$osphenoid is surangular. partially recognizable in the holotypic skull, but the two The articular forms the entire articular fossa, which is bones are fused in the paratypic skull. In living amphisbae- nearly vertical in orientation with a convex surface, matching nians, the pleurosphen6id is an independent ossifica- the concave articular facet of the quadrate condyle. The tion in young specimens and is fused to the prootic in old broken ventral edge indicates that the bone had a stout retro- adults (Zangerl 1944). In ventral view, the prootic expands articular process and shows that the bone is pneumatized. and meets the basisphenoid rnedially and the opisthotic por- No lateral notch is formed at the base of the retroarticular tion of the exoccipital posteriorly. In the paratype, a break process. reveals that the left prootic (mainly the pleurosphenoid por- tion), together with the orbitosphenoid and basispheioid, Dentition encloses a large foramen for the trigeminal nerve. A separate The description of the dentition is based on that of the para- foramen posteromedial to the latter or lateral to the edge of type. The upper teeth are distinctive in that each is almost the basisuhenoid is identified as the exit of cranial nerve VII. horizontally oriented along the medial edge of the lip-like Posterolaterally, the prootic enters the fenestra ovalis. rim of the jaw line (Fig. 5B). All the teeth preserved are The unpaired orbitosphenoid floors the anterior portion of homodont and conical in outline, and are indistinctly fused the braincase (Figs. 5B, 5D, 7). Dorsally, its sutures with the to the jaw, thus appearing to be acrodont. The last tooth of descending processes of the frontals are obscured by fusion. each maxilla is clearly much smaller than those anterior to The presence of the orbitosphenoid is determined primarily it and is not fully ankylosed to the maxilla. None of the teeth by the following features: (i) the bone is underlain by the bears a nutrient foramen medially at the base, and no replace- For personal use only. parasphenoid cultriform process; (ii) the bone meets the ment teeth are evident. These patterns indicate that the teeth prootic, basisphenoid, and ventral process of the parietal; were not replaced, and that new teeth were probably added (iii) the bone borders the foramen for the trigeminal nerve; to the posterior end of the tooth row. and (iv) the bone encloses the pair of optic nerves. Among The premaxilla bears six teeth, including a median tooth known lepidosaurians, only the amphisbaenian orbitosphe- that is distinctly larger than the others. Spaces between these noid shows all of these features. Ventrally, the orbitosphe- teeth indicate that the complete dentition of the premaxilla noid forms a pronounced median crest, which diverges probably consisted of nine teeth. The maxillary dentition also anterolaterally to reach the upper jaw. The part of the sutural includes nine teeth. The teeth in the middle region are contact with the descending process of the frontal may extend slightly larger than those at either end, and all are larger than along the anterolateral branch of the crest. Lateral to the the teeth of the premaxilla. crest the ventral surface of the bone is strongly concave. The dentary dentition also consists of nine homodont, conical teeth, of which tooth 6 is broken away. The dentary Mandible teeth are clearly larger than those of the maxilla. The first

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 The description of the mandible is based on that of the para- dentary tooth is smaller and more pointed than the following type (Fig. 5B). The splenial, if present, and the medial sur- five or six teeth. The eighth tooth is slightly smaller than the face of each element are not visible. A small subdental shelf middle six teeth. The last dentary tooth is the smallest and is indicated by the thin, concave medial surface of the den- is not well ankylosed to the dentary, indicating that teeth tary. Meckel's canal seems to be open anteriorly, as indi- were added to the back of the tooth row, as is the case with cated by the matrix filling within it. the upper jaw. Although the medial surface of the tooth row The large dentary, with its ventral edge and posterior end cannot be observed, it is evident that each tooth is distinctly damaged, is dorsoventrally broad and possesses an elongate ankylosed to the lateral surface of the bone. posterior process inserting between the surangular and angu- lar. Posterodorsally, the bone is laterally overlapped by the Vertebral column and ribs coronoid and does not develop a coronoid process. Anter- Of the 19 preserved vertebrae, the first eight are considered iorly, the bone bends slightly medially to meet its opposite to be cervicals, because their centra are shorter and less of the other side. strongly procoelous than those of succeeding vertebrae, and The coronoid is incomplete posterodorsally. The bone is because the neural spine at the end of this series is tall and exposed on the lateral surface of the mandible and forms a narrow (Fig. 8). However, some uncertainty exists, because Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 For personal use only.

Fig. 8. Sineoamphishuma herutahidoris, postcranialskeleton of holotype(IVPP V10593) in (A) dorsal and (l3) ventral views. ax, axis; afh, articular facet for hypapophysis; co, coracoid:con, anterior mracoid emargination;h, humerus; id, interclavicle;nax, neural arch of axis; nd. odontoid processof axis; sca, scapula; c, and c,, cervical N vertebrae3 and 7; r9 and r,,, ribs 9 and 19; v,, and v,,, vertebrae 10 and 15. Other abbreviationsas in Figs. 4 and 5. Wu et al. 553

Fig. 9. Selected vertebrae of the holotype of Sineoamphisbaena hexatabularis (IVPP V10593). (A-C) Atlas, axis, and the third cervical vertebra in anterior, dorsal, and ventral views, respectively. (D) Vertebrae 15- 19 in lateral view. v,, and v,,, vertebrae 17 and 19. Other abbreviations as in Fig. 8. For personal use only.

the relationship of their ribs to the pectoral girdle is unknown. teriorly on its ventral surface. These are articular facets for Although none of the cervical vertebrae bears a preserved a large anterior hypapophysis (the hypocentrum of the atlas) hypapophysis, an articular facet on the posteroventral end of and a small posterior hypapophysis. The centrum is much the centra suggests that hypapophyses were present on the broader anteriorly than posteriorly, because it is widened axis and cervical vertebrae 3 - 7. The cervical vertebrae do anteriorly by the base of a single lateral tubercle (diapapo- not bear any ventral foramina for blood vessels. The neural physis), which does not form a distinct articular facet for a arch is preserved in the atlas and axis, but has been badly rib. The ventral surface of the centrum is constricted and damaged in cervical vertebrae 3-7. The articular facets of forms a stout ridge along the ventral midline. The neural spine of the axis is high, but it is not known whether it was

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 the preserved pre- and postzygapophyses of the cervical vertebrae are almost horizontally oriented, indicating free broad anteroposteriorly . lateral movement between the vertebrae. Cervical vertebra 3 is not fused to the axis, and is much The atlas is represented by its neural arches (Figs. 9A - 9C). smaller than the latter. From cervical vertebrae 3 - 8, the fol- The better preserved right arch is not narrowed dorsally. It lowing changes are evident (Fig. 8): (i) the centrum becomes is very thin and loosely contacts the left arch along the dorsal longer and wider, (ii) the ventromedian ridge becomes midline. Ventrally, the neural arch becomes lateromedially weaker, (iii) the ventral surface of the centrum becomes flat- thick. Neither neural arch is complete ventrally. ter, (iv) the lateral tubercle becomes more massive, and The axis is missing only the posterior portion of its neural (v) the articular facet for the hypapophysis becomes smaller. arch (Figs. 9A-9C). The odontoid process is fully co-ossified The ventromedian ridge and the hypapophysial facet are with the centrum. It is not sharply pointed, but is rounded entirely absent in cervical vertebra 8. Starting from cervi- anteriorly, fitting into the double occipital condyle. Posterior cal 4, the lateral tubercle forms a subcircular and slightly to the odontoid process the centrum of the axis has a large concave articular facet for a rib. The neural arch of cervical depressed facet anteriorly and a small depressed facet pos- vertebra 8 is complete. Its spine is higher and narrower than Can. J. Earth Sci. Vol. 33, 1996

that of any of the succeeding vertebrae. It is likely that the tion is present just anterior to the coracoid foramen. neural spines of cervical vertebrae 3 -7 were narrow and tall Although the anterior edge of the coracoid is not preserved, as well. this emargination is quite deep, judging from its ventral The posterior 11 vertebrae of the preserved series are border. It is impossible to determine whether the posterior identified as trunk vertebrae (Fig. 8). These vertebrae resem- coracoid emargination or the scapulo-coracoid emargination ble each another. Their centra are much more laterally con- are present from the material available. The thickened stricted; their diapapophyses (lateral tubercles) are stronger posterior edge of the bone is complete and is strongly curved than those of the cervical vertebrae; their neural arches are posteriorly. The intact medial edge of the bone is rounded. broadened between the pre- and postzygapophyses and The coracoid is ventrally convex and dorsally concave. The largely overhang the centrum; the height of their neural coracoid foramen is located between the anterior coracoid arches (from the articular facet of the postzygapophysis to emargination and the glenoid. The coracoid portion of the the dorsal tip of the spine) is distinctly greater than that of glenoid is distinctly larger than the scapular portion. their centrum; the width between their prezygapophyses is The interclavicle is represented only by its posterior end larger than that between their postzygaphyses; their neural (Figs. 8B, 10A, 10C). It does not contact the coracoid in spines are longitudinally broader, but dorsoventrally shorter living squamates. That the remains of the bone are here than the neural spine of the last cervical vertebra, and are not clamped by two coracoids is probably a creation of preserva- strongly inclined posteriorly beyond the postzygapophysis; tion, likely resulting in part from the nonfossilization of the the top of their spines is broadened to form a flat plate that cartilaginous sternum. is narrow anteriorly and wide posteriorly; and their diapapo- The nearly complete left humerus remains in articulation physes are located at the anteromedian margins of the centra, with the pectoral girdle, but it is preserved in an inverted are directed mainly laterally, and bear slightly concave artic- orientation, with the anteromediaf surface facing laterally ular surfaces. A single large median foramen for blood ves- and the posterolateral surface facing medially (Figs. 8, sels occurs at the anteroventral midline of each centrum in 10A- 1OC). Proximally, the delto-pectoral crest is located trunk vertebrae 2-9 (vertebrae 10- 17). This median fora- close to the proximal head, resultingin a broad proximal end men is of uncertain presence in the first trunk vertebra, of the humerus. Medial to the crest the humerus has a notch- because it is obscured by the overlapping pectoral girdle. like breakage. The epiphysis for the articulation with the The foramen is absent in trunk vertebra 10 (vertebra 18) and glenoid is large, but not fused to the proximal end of the is probably also absent in the following vertebrae. The cen- bone. Medial to the articular epiphysis the humerus develops tral condyles of the trunk vertebrae face primarily dorsally, a prominence that is directed posteroventrally. The epiphysis but are narrowly visible ventrally, as shown in trunk ver- capping the prominence has been lost. The distal end of the tebrae 9 and 10 (Fig. 9D). humerus is also quite broad, being only slightly narrower Most of the preserved ribs are present in their original than the proximal end. The preserved small posteromedial position, although none is articulated with its associated ver- epiphysis is slightly displaced laterally. The remaining two tebra (Fig. 8). No significant differences between the ribs are large epiphyses are missing, leaving a groove-shaped articu- For personal use only. recognizable. A complete rib has a stout head and a subcylin- lar facet across the entire surface of the distal end. The shaft drical shaft that gradually tapers distally. The head does not of the bone is twisted, so the two broadened ends occupy exhibit any additional processes. Its oval articular facet is different planes. The shaft is almost round in cross section. slightly convex, fitting the slightly concave facet of the Its diameter is about 26% of the maximum width of the prox- diapapophysis of the corresponding vertebra. On the left side imal end. Medially, the surface of both ends is concav;, and of the series the last three cervical ribs are preserved, but the shaft is somewhat curved medially. The lateral surface of cervical rib 8 is missing its distal portion, cervical rib 7 lacks the bone is not strongly convex. The ectepicondylar foramen its proximal portion, and cervical rib 6 is represented by the is present in the distal portion of the right humerus (Fig. 10D). middle portion of its shaft. The left seven trunk ribs are represented by their proximal portions, whereas most of the Comparison right 11 trunk ribs are preserved. The strongly curved shaft of the trunk ribs suggests that S. hexatabularis may have had Since no consensus on the sister-group relationships of the a laterally compressed and elongate body. Amphisbaenia has been established, comparisons have been made with as many taxa within the Squamata as possible. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Recently, the Sphenodontida (Rhynchocephalia) and Kueh- Pectoral girdle and forelimbs neosauridae have been hypothesized to be the successive The ventral portion of the left scapula is preserved (Figs. sister groups of the Squamata (Gauthier et al. 1988; Evans 10A- 10C). The anterior margin of the preserved portion is 1988), and are used as outgroups in determining the polarity damaged, so the presence or absence of any scapular emargi- of each character. Characters of S. hexatabularis are pre- nation cannot be determined. The complete scapula may sented in four main groupings: autapomorphic (uniquely have been a dorsoventrally short, anteroposteriorly elongate derived) characters (the diagnostic features of the species), bone. The posterior portion of the bone is much thicker than apomorphic (derived amphisbaenian-like) characters, plesio- the anterior portion, and the posterior border curves morphic (lizard-like) characters seen in no later amphisbae- inwards. The scapula bends slightly medially both dorsally nians, and characters variable within the Amphisbaenia. In and ventrally, and sutures to the coracoid ventrally. addition, a set of apomorphic characters that suggest proba- The left coracoid is missing its anterior and anteroventral ble relationships of the Amphisbaenia are discussed later in margins (Figs. 10A- 10C). An anterior coracoid emargina- the phylogenetic consideration. Wu et al.

Fig. 10. Pectoral girdle and forelimb of the holotype of Sineoamphisbaena hexatabularis (IVPP V10593). (A-C) Left pectoral girdle and forelimb in (A) lateral (but note that the humerus is inverted and shows the medial surface), (B) anterior, and (C) posterior views. (D) Distal end of the right humerus in lateral view. epf, ectepicondylar foramen. Other abbreviations as in Fig. 8.

D epi For personal use only. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11

Auhpmorphic characters interorbital region is arched and superficially ornamented, (i)Presence of a hexagonal interorbital table with pronounced but not elevated to form a platform-like structure in any of rugosities on parietais (Fig. 5C): Within squamntes. some the other known members. Additionally, the elements around chamaeleons. such as Rhomphoi'eon specrum 4Rieppel 19873, the orbits are extensively reduced and the frontals are the have an interorbital region that is more or less hexagonal in only bones between the orbits. dorsal view. However, ir differs from that of S, he-mtuhrf- (ii) Dermal cranium wider than long or dermal cranial lark in that it consists only of an unpaired large frontal and width subequal to skull length along ventral midline (Figs. 4A, is not raised posteriorly to form an elevated table. and no 5C): A dermal cranium that is wider than long is also present large rugosities are present. Within the Amphisbacnia, the in certain horned iguanian lizards, such as Phrynosoma Can. J. Earth Sci. Vol. 33, 1996

modesturn (RTMP T162), but in contrast to S. hexatabularis, fenestra is bordered posteriorly only by the mobile quadrate. the width of the dermal cranium is not only much greater The squarnosal, or squamosal plus supratempomi. sits on the than its length but also much greater than the length of the dorsal surface of the head of the quadrate in these forms. A entire skull. The dermal cranium is distinctly longer than ventrally open infratemporal fenestra is present in primitive wide in other amphisbaenians, owing to an elongation of the members of the Sphenodontida. In these forms, the squa- postorbital portion of the skull. mosal contributes to the posterior border of the fenestra. (iii) A fused postfrontal-postorbital complex contacting However, the posterior border in the early sphenodontidans prefrontal above orbit and parietal both anterior and pos- differs, in that the descending process of the squarnosal and terior to supratemporal fenestra (Figs. 4A, 5C, 6A, 6C): quadratojugd extends along the laterd side of the nearly ver- A postfrontal -prefrontal contact and a postfrontal-parietal tically positioned quadrate. contact are commonly present in lizards, examples being (vii).Parietal and squamosal forming a semicircular arc some chamaeleonids (Brookesia superciliaris and Rhum- tightly embracing braincase (Figs. 6A, 6D): The posttern- pholeon brachyurus, Rieppel 1987). and some burrowing poral fenestra results in a large gap between the dermal scincomorphs (Tvpldosaurus lineatus, Acontias plumbeus, cranium and the braincase in nonburrowing lizards and some Rieppel 1981). However, these forms do not have a postorbi- burrowing forms. In many burrowing lizards, amphisbae- tal, although they still have a supratemporal fenestra. To our nians, and snakes, the posttemporal fenestra is reduced and knowledge, no known Iizards that retain the supratemporal roofing elements overlap the braincase, so the dermal skull fenestra have a postorbital-parietal contact posterior to the roof and braincase merge. However, the eIements of the fenestra. In the Scincidae (Estes et at. 1988), the postorbital - dermal cranium do not extend over the ventrolateral surface parietal contact is present behind the postfrontal -parietal of the braincase in these squamates. In S. hexarabularis, the contact, but the supratemporal fenestra is entirely closed and squamosal is an elongated sphenoidal element, flanking the no postfrontal-prefrontal contact occurs above the orbit. posterolateral margin of the dermal cranium. This bone is Although the postfrontd and pstorbital are both present and overlapped posterodorsally by the supratemporal process of the former meets the prefrontal above orbit in some fossil the parietal, so the two pairs of bones form a semicircular, amphisbaenians (Berman 1973, 1976). the relationship of the arc-shaped structure along the posterior margin of the dermal postorbital to the parietal cannot be compared with that in cranium. This arc tightly hugs the dorsal and ventroiateral S. hexatabularis, because of the absence of the supratem- surfaces of the braincase, resulting in the closure of the post- poral fenestra. temporal fenestra. (iv)Tall, narrow dorsal process of maxilla and deep, broad (viii) A broadened, lip-like oral rim of upper jaw around ventral portion of prefrontal-lacrimal complex (Figs. 4C, tooth row (Fig. 5B): This rim appears to be present in certain 6A, 6C): In squamates, the lateral surface of the cranium species of the burrowing scincomorph Typhlosaurus,includ- between the naris and orbit is formed generally by the dorsal ing T. lineatus (Rieppel 1981). The detailed morphology of process of the maxilla and lacrimal or prefrontal, or fused the rim structure is different, however, between S. hexatahu- prefrontal-lacrimal. In most of the squamates without the laris and T. lineatus. In the latter, the dm is very narrow,

For personal use only. lacrimal. the ventral process of the prefrontal tapers to a and the paired premaxiliae develop a pronounced antero- point, so the broad dorsal process of the maxilla forms the median portion that extends anteriorly and is twice as broad major portion of the antorbital region. In Sphenodon, the as the oral portion (Fig. 11A). In other squamates, the only living representative of the sister group Sphenodontida. prernaxilla and maxilla are very narrow lateral to the tooth the dorsal process of the maxilla tends to be narrow and tall. row and form a sharp oral edge or do not have an oral edge but the ventral process of the prefrontal (no lacrimal) is still at all. This is also the case in the other known amphis- ventrally pointed and much narrower than in S. hexatahu- baenians . laris. This resembles the condition seen in chamaeleonid liz- (in) Otic capsule bulges posteriorIy beyond occipital con- ards (Rieppel 1987). In addition, all known fossil members dyle (Figs. 5, 6A): In typical lizards, as in most diapsid of the Sphenodontidathat have the relevant portion preserved reptiles, the otic capsule develops a pronounced posterolater- show a very broad dorsal process of the maxilla and a very ally directed paroccipital process. In general, this process narrow ventral process of the prefrontal, as in other lepido- forms the posterionnost point of the braincase (Fig. 11B). In saurornorphs (Evans 1980; Fraser 1988; Carroll 1985; other amphisbaenians, burrowing lizards, and most snakes, Whiteside 1986; Wu 1991, 1994). the otic capsule forms either a short and broad paroccipital Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 (v)A slender supratemporal process of parietal directed process or a distinct posterior bulge, but the occipital condyIe ventroIaterally and slighdy anteriorly (Figs. 4A. 5C, 6D): forms the posteriormost portion of the braincase (Figs. 11A, The supratemporal process of the parietal present in most 1 lC, 12B, I2C). During embryonic development the occipi- lizards {including many burrowing forms that have lost the tal condyle always forms the posteriormost portion of the supratemporal fenestra, as well as in the primitive snake braincase in burrowing squamates, including the scinco- Dinilysin patagonica (Estes et al. 1970)) usually points morph Acontias meleapis, the anguimorph AnnieIla pulchra strongly posteriorly or posterolaterally and forms the pos- (Bellairs and Kamal 1981, Figs. 23, 39), and the amphisbae- reromedial border of the supratemporal fenestra, if this is nian Leposternon microcephulum (Bellairs and Gans 1983, present. The supratemporal process of the parietal is also Fig. 1). Alternatively, it is initially anteriorly situated and present in most amphisbaenians, but it is stout and directed subsequently occupies the posteriormost position in later posterolaterally, as in burrowing lizards and snakes. embryonic stages as in the gekkonid Piyodacrylus hamel- (vi) Squamosal forming entire posterior border of infra- quistii and the agamid Agamu mutabilis (BeIlairs and Kamal temporal fenestra (Figs. 6A, 6C):In squamates that retain an 1981, Figs. 27, 34). infratemporal fenestra, the ventrally open infratemporal (x) Extreme elongation of basioccipital -basisphenoid Pig, 11. (A) Skull of a bumwing lizard ~vpkiosaurrn Fig. 12. (A) Skull of a snake Python regius (after Rage iirreatll~in ventral view (afrer Rieppel 1981. Fig. 7C). 1984, Fig. 1C) in ventral view. (B) Skull of a living (R} Skull of a Cretaceavs lizard Po/sgl~yphandorlst~rnbrrgi amphisbaenian Amphisbaena alba (MCZ 54299) in ventral in ventral vicw (after Gilmosc 1942h. Fg. 19). (0Shll of view. Not to scale. spt, supratemporal. Other abbreviations a living arnphisbaenian. Amphishnetlo aha (MZC 54299). in as in Figs. 4, 5, and-11 tateral view. Not to scale, ot, fused otic-nccipital complex: pis, pleurosphenoid process of prontic. Other abbreviations as A in Figs. 4 and 5. A

MCZ 145823 shows that the bone in this species differs little in orientation from other extant amphisbaenians, being very oblique but not horizontal in position. In the Sphenodontida and other nonsquamate lepidosauromorphs, the position of the quadrate is similar to that of lizards. For personal use only. (xii) Absence of quadrate foramen (Fig. 6A): A tiny fora- men is present on the ventrolateral surface of the quadrate in complex {Figs. SB, 5D): The basioccipital - basisphenoid lizards. The quadrate of Varanus dumerilli (RTMP 90.7.46) complex is usually vcry short in relation to cranial length in has an additional foramen on the dorsolateral surface. The lepidosaurims. This complex 1s relatively long in Dibamus quadrate of snakes (such as Elaphe obloleta (RTMP T-190)) novagguineae (Rieppel 1984) and the primitive snake Dini- has only a tiny foramen on its dorsolateral surface. A fora- lysin paragonicu, hut differs from the configuration in men is present on the dorsolateral surface of the quadrate in S. kexatububris. In the former species, the complex, mea- the later amphisbaenians, but it differs from that of snakes in sured from the base of the basipterygoid process to the occi- being much larger in size. It is unknown whether a quadrate pital condyle, occupies about two fifths of the cranial length. foramen is commonly present in more primitive lepidosauro- In contrast, the complex in S. hexatabularis is nearly half morphs, although it is recorded in the Jurassic burrowing (47 %) the length of the cranium. Although the cranium of the diapsid Tamaulipasaurus morenoi (Clark and Hernandez iguanian lizard Phrynosoma modestum (RTMP T162) is 1994, Fig. 1B). In the Sphenodontida, a large quadrate fora-

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 wider than long, its basioccipital-basisphenoid complex is men is enclosed by the quadrate and quadratojugal. The data only about a third of the cranial length. Within the Amphis- available seem to indicate that the the loss of the quadrate baenia, the basioccipital -basisphenoid complex is relatively foramen is apomorphic within the Squamata and probably shorter than it is in some burrowing lizards, despite the unique to S. hexatabularis. elongation of the postorbital reglon. (xiii) Presence of single median foramen on ventral mid- (xi)Quadrate horizontal in orientation (Fig. 6A): In most line of each anterior dorsal vertebra (Fig. 8B). Foramina are nonamphisbaenian squamates, including many fossorial and present anterolaterally on the ventral surface of vertebrae in burrowing forms, the quadrate is almost vertical in positlon many lizards and snakes (Estes et al. 1988). In amphisbae- when the jaws are adducted. The fossorial typhlopid and nians, such as the extinct Spathorhynchusfossorium (USNM leptotyphlopld snakes have a quadrate similar in orientation 263 17,26318) and Dyticonastis rensbergeri (UCMP 76882), to that of most known amphisbaenians (Zangerl 1944; Estes and the living Bipes biporus (MCZ 145823), Rhineura flor- et al. 1988), in which the bone is oblique in position. Accord- idana (MCZ 55615), and Cadea palirostrata (MCZ 13508), ing to Zangerl (1944, Fig. 9B), the quadrate is also hori- an anterolaterally positioned foramen is also present on each zontally oriented in Bipes biporus. However, specimen side of the ventral surface of the vertebrae. In a small skele- Can. J. Earth Sci. Vol. 33, 1996

ton of Amphisbaena alba (MCZ 54299, which has a skull the consolidation has already reached the amphisbaenian length of 2.5 cm from the snout to the occipital condyle), an level in many respects: the braincase is entirely closed; the additional median foramen is present on the ventral midline orbitosphenoid is penetrated by only a tiny pair of optic fora- of the first 19 vertebrae, 11 of which are in the trunk region. mina; the palatal elements are tightly sutured or overlap one In contrast, this median foramen occurs only in the first another to close the palatal fenestrae; the palate is firmly 10 vertebrae, two of which are in the trunk region, in a large attached to the ventral floor of the braincase; and intracranial skeleton of this species (MCZ 165208, which has a skull kineses are prevented hy compIicated sutural patterns length of 3.74 cm). This suggests that the median foramen between dermal elements, the fusion of cranid elements, and disappears with growth in this species. In S. hexatabularis, the loss of the posttemporal fenestra. anterolateral foramina are not present on the ventral surface (ii) Enlarged median tooth on fused premaxilla (Fig. 5B): of any of the preserved 19 vertebrae, and a large median The premaxilla is an unpaired bone in a11 known arnphisbae- foramen is only present on the ventral midline of vertebrae nians, as it is in most lizards, but it differs in amphisbaenians 10- 17 (condition not known in vertebra 9). In contrast to in bearing an enlarged median tooth. The enlarged median Amphisbaena alba, where the median foramen is lost onto- premaxillary tooth has been considered an autapomorphy of genetically from posterior to anterior along the vertebral the Amphisbaenja within the Squamata (Gans 1978; Estes column, the median foramen in S. hexatabularis is absent et al. 1988), The premaxilla is single in S. he.ratabularis. A anteriorly in the cervical region but present in the trunk median tooth is present, and dthough it is only slightly larger region. Consequently, we interpret the presence of a large than the others, this can be interpreted as an early stage in median foramen in the anterior trunk vertebrae as a unique the evolution of the condition seen in the latter amphis- character of S. hexatabularis within the Squamata, although baenians. it is possible that this foramen could be lost ontogenetically (iii) Unpaired dermal orbitosphenoid (Figs. 5B, 5D). in the species. Arnphisbaenians are unique in the presence of an orbitosphe- noid that is ventromedial in position and is of dermal origin Apomorphic characters (Bellairs and Gans 1983). The presence of the orbitosphenoid (i) Skull solidly built (Figs. 5, 6): The presence of a solidly in S. hexatabularis is indicated by its position, its relation- built skull with complex interdigitations between the anterior ships with the neighbouring bones and with the foramen for bones is considered by Gans (1978) and Estes et al. (1988) the trigerninal nerve, and its perforation by the optic fora- to be unique to the Amphisbaenia. The consolidation of the men. Estes et al. (1988) consider the presence of an unpaired amphisbaenian skull is accomplished primarily by the dermal orbitosphenoid to be one of the autapomorphies of the anterior closure of the braincase, the extensively sutured Amphisbaenia, but they doubt the uniqueness of the charac- palate without fenestrae, the tight contact of the palate with ter, because of the lack of a broad developmental study of the the ventral surface of the braincase, the presence of a double- bone in the group and the supposed equivalency of the bone layered floor on the anterior region of the braincase, and the to the crista alaris of the prootic of lizards, as suggested by loss of any intracranial kinesis resulting from the reduction Rieppel ( 198 1). Indeed, Rieppel argued that the pleurosphe-

For personal use only. of the temporal fenestrae and strong interdigitations between noid is a homologous ossification of the crista alaris of the the elements. Snake skulls share some of the above condi- prootic in the lizards of the Acotinae, but he doubted the tions with amphisbaenians, such as the closure of the anterior presence of a separate pleurosphenoid and did not compare braincase, the loss of metakinesis between the dermal cranium the bone to the orbitosphenoid, or indicate that the and braincase, the reduction of the temporal fenestrae, and "pleurosphenoid" and "orbitosphenojd" represent an iden- the extensive overlap of the dorsal surface of the braincase tical ossification in amphisbaenians. The pleurosphenoid and by the parietal. However, loose connections between palatal orbitosphenoid are two independent ossifications in amphis- elements, a wide separation between the palate and floor of baenians, and the former 1s ontogenetically fused to the the braincase, the presence of mesokinesis between the prootic (Zangerl 1944). Our own examination shows that the frontal and parietal, and the presence of a pair of large optic pleurosphenoid has already fused with the prootic to form foramina mean that the skull architecture of snakes is signifi- the dorsalmost border of the foramen of the trigeminal nerve cantly less robust than that of arnphisbaenians. In some in a 2.5 cm long sku11 of Amphisbaena alba (MCZ 54299), fossorial lizards, such as Dibamus novaeguineae, the skull whereas the orbitosphenoid is still independent of all neigh- resembles that of amphisbaenians in dorsal view in the loss bouring bones and is separated by a tiny ventral process of

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 of the meta- and mesokinetic joints, but differs in ventral the parietal from the pleurosphenoid (pleurosphenoid process view in retaining a braincase that is widely open anteroven- of the prootic) at the anterodorsal margin of the foramen in trally and a palate that is fenestrated and lacks a firm contact this skull (Fig. I 1C). Nevertheless, in a 3.74 crn long skull with the braincase floor. The anterior closure of the brain- of this species (MCZ 165208) the orbitosphenoid extends case in the Jurassic burrowing diapsid Tamaulipasaurus further posteriorly along the ventral margin of the parietal morenoi is similar to the situation in snakes. In the former, and has become fused to the pleurosphenoid process of the the palatine -pterygoid contact does not appear to be present. prootic through a very slender posterior process along the The retention of a small supratemporal fenestra, a supra- dorsal border of the foramen of the trigeminal nerve. In temporal arcade resulting in a weak connection between the the specimens of some fossil taxa at hand (Sparh~rkynchus elements of the dermal cranium and the dorsal surface of the fossorium (USNM 26317, 263181, Sptkorhynchus nasroni- braincase, and weak interdigitations between the anterior GUS (AMNH 8677) and Rhineura hibbardi (UMMP 2543 1)). bones indicate that the skull is consolidated to a lesser degree no suture is recognizable between the orbitosphenoid and in S. hexatabularis than in other amphisbaenians. However, pleurosphenoid process of the prootic. In these fossil taxa, Wu et al.

the parietal is excluded from the foramen of the trigeminal wrapping posteromedial (ventromedial if quadrate hori- nerve by the fusion of the orbitasphenoid and pleurosphenoid zontally oriented) surface of quadrate (Figs. 5D, 7). The process. as in the largc specimen of Amphisl?mnn r~lh.In pterygoid has an elongated quadrate ramus that is loosely S. hexarabularis. the suture between the orh~tosphenoicland connected to the posteromedial surface of the quadrate just pleurosphenoid process is still open in the holotypic skull above the articular condyle in lizards. This is also the case (Fig. 6C), but obscured by Fusion In the paratypic skull. The in fossorial or burrowing lizards and snakes (Figs. 11A, available evidence indicates that the orhitosphenoid is an 11B, 12A). The quadrate ramus of the pterygoid is greatly additional ossification rather than is homologous to the reduced in length in extant amphisbaenians (Fig. 12B). pleurosphenoid in the Ampfiishaenia. although it fuses with Examination of the original specimens of the fossil amphis- the pleurosphenoid at a late stage of gowth. baenians at hand (Spathorhynchusfossorium (USNM 263 17, {iv) Anlerior braincase floored by single orbitosphenoid 263 18), Spathorhynchus natronicus (AMNH 8677), Dyti- (Figs. 5B. 5D): Gans (1978) argued that rhe anterior brain- conastis rensbergeri (UCMP 76881, 76883). and Rhinerrru case of the Arnphisbaenia is unique in its complete closure hihbnrhi (UMMP 25431)) reveals that the quadrate ramus of by the parietals. frontals, lacrimals (or prefrontals). and the ptetygoid is also very shorf and wraps around the orbitosphenoid, these bones forming a continuous tube from posteromedial surfacc of the quadrate. The disarticulatd the cranial cavity to the nasal passage. Estes et al. (19X8) quadrate ramus of the left pterygoid of Dyticonusris rms- considered that the anterior closure of the braincase is a hrr,iyri (UCMP 7688 1) shows a distinctly convex - concave derived character uniquely shared with snakes. However, as articular faccf that occupies the entire surface of the ramus. Gans pointed out, the closure of the anterior hraincnse in This further demonstrates that the articulation between amphisbaeninns and snakes differs. It is closed by the fron- the pterygoid and quadrate is firm and immovable in the tal~and parietals resting on the parasphenoid cultriform Amphisbaenia. A firm, immobile articulation between the process in snakes. whereas the orbitosphenoid form5 the pterygoid and quadrate is also present in the Sphenodontida. rloor of the anterior braincase and the parasphenoid oultri- However, this is accomplished by an interlocking connection form process underlies the orhitosphenoid in anlphishae- between the greatly broadened quadrate ramus of the ptery- nians.-~hus.this process floors the anterior braincasc along goid and the similarly sized pterygoid ramus of the quadrate, the ventral midline in snakes. but the anterior braincase IS and differs from the condition in the Amphisbaenia, in which double-floored in amphisbaenians. the ptepgoid ramus of the quadrate is entirely absent. Ir) A pair of tiny optic foramina situated entirely within The apomorphic characters discussed above, which are orbitosphenoid [Fig. 5R): In lizards, including burrowing uniquely shared by S, hcrulahularis and all other amphisbae- forms, the anterior braincase is widely open and the optic nians, constitute a set of wtapomorphies for the Amphisbae- nerves exit the cranial cavity freely. In snakes, the antcrior nia. Ln addition to these characters, a suite of derived features braincase is closed by bones and the optic nerves exit the shared by S. hexatabularis, other amphisbaenians, and one braincase through a pair of large foramina that are sur- or more groups within the Squamata is present. These are as rounded by the frontals, parietals, and parabasisphenoid follows. (Estes et al. 1970. Fig. 5A) or by the frontals and parictals (viii) Prefrontal contacting postfrontal (or fused post- For personal use only. (Fig. 12A). The Amphisbaenia differ in that the optic frontal-postorbital complex) above orbit (Estes et al. 1988) foramina are greatly reduced in size and only pcnelratc (Figs. 5C, 6A, 6C): Among other known amphisbaenians, the unpaired, ventromedially positioned orbitosphenoid species of Spathorhynchus retain a complete orbit and the Fig. 12B), but, this is not sure in fossil taxa, owing to the two bones that meet above it (Berman 1973; the authors' firm overlap by the palate and broad parabasisphenoid process. personal observation). In the Sphenodontida and nonsqua- (I+) A large foramen for trigeminal ncrve enclosed hy mate lepidosauromorphs in which this character is known, orbitosphenoid. prootic. and p&tbasisphenoid (Fig, 33): the two bones do not meet along the orbit. The tripminal nerve extends anteriorly through an open (ix) Descending processes of frontals contacting each notch located at the anterolatcral wall (formed by rhe prmtic) other below olfactory tracts (Estes et al. 1988): The ventro- of he braincase in all lizards. In snakes. the anterior brain- median contact of the descending processes of the frontals case is no longer open and the trigeminal nerve exits the below the olfactory tracts forms a triangular structure that braincase thmugh one or two foramina located entirely inserts posteriorly into the orbitosphenoid in living amphis- within the prootic or bctween the prootic and parietal. In thc. baenians (Fig. 12B). The nature of the contact is unknown

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 primitive snake Dinihsia pcrtaponini (Estes et al. 1970. in other fossil amphisbaenians, because it is completely hid- Fig. SA), a single larpe foramen for the trigeminal nerve is den by palatal elements. Although no suture between the enclosed by the prootic rather than by the prwtic and parie- frontals and orbitosphenoid is recognizable in either the holo- tal. as in an erycine snake Ety miilleri (Ricppel 1978. typic or paratypic skulls of S. hexatabulnris, a triangular por- Fig. 1). In many lhring snakes. branches of the trigeminal tion immediately anterodorsal to the anterior ridge of the ncrve pass through foramina located only within the prootic orbitosphenoid (Figs. 5B, 5D) resembles the ventromedian (Fig. 12A). Where known in amphisbaenians. the foramen contact of the descending processes of the frontals of living for the trigemind nerve is a single, larpe openlng that is taxa in both morphology and position. In frontal view, as bordered by the orbitosphenoid anteriorly. prootic dorsally seen through the naris, the descending processes of the and posteriorly, and parabasisphenoid ventrally. The parietal frontal in the holotypic skull extend ventrally over the also forms a tiny poninn of the dorsal border of the opening opening for the olfactory tracts (Fig. 6B). The above evi- in young individuals of Amphishaena alh. dence indicates that a ventromedian contact of the descending (vii) Quadrate ramus of pterygoid very short and tightly processes of the frontals is most probably present and located Can. J. Earth Sci. Vol. 33, 1996

anterior to the orbitosphenoid in S. hexatabularis, as it is in occipital recess (Oelrich 1956), or may be just equivalent to living taxa. the recessus scalae tympani (Rieppel 1985). The closure of (x) Supratemporal lost (Estes et al. 1988). The identifi- the occipital recess results in a tiny foramen for cranial nerve cation of a temporal bone located along the posterolateral IX. This is closely related to a great reduction of the middle margin of the dermal cranium as the squamosal rather than ear apparatus and occurs in all known amphisbaenians. The the supratemporal in S. hexatabularis is primarily based recessus scalae tympani was reported to be present in S. ha- upon the relationships of the bone with neighbouring ele- arabuluris (Wu et al. 1993, Fig. 2b. "or"). Further exami- ments. In the Squamata, the squamosal generally contacts the nation reveals that the recessus is completely closed, as in postorbital and, together with the latter, forms the supratem- other arnphisbaenians. The feature that was identified as the poral arcade, as in other diapsids. In some squamate taxa and occipital recess is actually a depression between the occipital fossil sphenodontidans (Carroll 1988; Wu 1994), this bone condyle and otic capsule. A similar depression is seen in also meets the jugal along the lateral border of the supratem- Amphisbaena alba (Fig. 12B). In the holorypjc skull, a frag- poral arcade. In addition, this bone is occasionally separated ment of the atlas (left side) and a piece of a hyoid (right side) from the supratempora1 fenestra by the postorbital- are preserved in the posterior border of the depression, so the supratemporal contact in a few squarnates, such as in Vara- shape of the depression is equivocal (Fig. 5D). In Spheno- nus dumerilli (RTMP 90.7.46) and the fossil scincomorphs don, the middle ear shows a primitive condition and the Darchansaurus estesi and Macrocephalosaurus chulsanensis occipital recess is absent. This is traditionally considered to (Sulimslu 1975; Estes 1983, Figs. 19D, 19F). The supratem- be an ancestral pattern retained from that of early diapsids, poral is usually situated between the squamosal and parietal although recent studies (Whiteside 1986; Wu 1991) argued and forms the posterior border of the supratemporal fenestra thar the pattern of the middle ear in Sphenodon is a derived in the Squamata. It is often fused to the squamosal in squa- rather than a primitive condition. Furthermore, the presence mates, but the sequence of fusion seen in M. chulsanensis of a lizard-like impedance-matching middle ear in the shows that this bone is never excluded from the border of the Sphenodontida (a large middle ear chamber, a fenesm rotun- supratemporal fenestra. The supratemporal never meets the durn within the occipital recess, a rod-like stapes, and a jugal in any known lepidosauromorph, although it may con- tympanum) has been suggested by a study of fossil taxa from tact the postorbital in a few lizards. Therefore, using the the Lower Jurassic of China (Wu 1991, 1994). Therefore, jugal contact, the postorbital contact, and the separation from the closure of the recessus scalae tympani is an apomorphic the supratemporal fenestra as criteria, the temporal bone in character. but is evoIved independently within the Squamata S. hexatabularis is the squamosal. The squamosal is retained and Sphenodontida. in a few fossil amphisbaenians (Spathorhynchusfossorium, (dv) Pterygoid teeth lost Fstes et d. 1988) (Fig. 5D): Hyporhina antiqua, Gilmore 1928), but no supratemporal Pterygoid teeth or denticles have not been reported in other has been recorded in any known amphisbaenians. The supra- amphisbaenians. Jn Sphenodorr, pterygoid teeth are also temporal is absent in many members of the Sphenodontida absent, but in fossil sphenodontidans pterygoid teeth are (Fraser 1982; Wu 1994) and the Kuehneosauridae (Evans numerous or are arranged in two rows (Evans 1980; Fraser

For personal use only. 1980), but Estes et al. (1988) argued that the loss of this bone 1982; Whiteside 1986; Wu 1991, 1994). occurred independently in these groups. (xv) Occipital condyle double (Gans 19781 (Fig. 6D): The (xi) Epipterygoid lost (Estes et al. 1988). The epiptery- occipital condyle in amphisbaenians is formed mainly by the goid is a rod-like bone, sitting ventrally in a pit on the dorsal exoccipitals. The basioccipital portion curves inwards, so surface of the pterygoid near the basipterygoid articulation the condyle is U-shaped in outline. No nonsquamate Iepido- and extending dorsally to the descending process of the saurornorph has a double occipital condyle. parietal or meeting the dorsalmost point of the alar process (xvi) Epiphysial ossification on ends of basioccipital- of the prootic in lizards. In the holotype of S. hexatabularis, basisphenoid suture (Gans 1978) Wig. 5B): ZangerI (1944) the pterygoid does not bear an articular pit for an epiptery- described independent ossifications (his "elements X") lying goid on the dorsal surface, and the lateral bulging of the lateral to the basioccipital-basjsphenoid suture in the prootic prevents a straight rod-like epipterygoid from Amphisbaenia. A pair of the X bones were identified by extending between the pterygoid and the descending process Lakjer (1927) as spheno-occipital epiphyses. The epiphysial of the parietal (Figs. 5B, 5D). Thus, we believe that the ossifications never occur in the Sphenodontida, nor in any epipterygoid was not present in S. hexatabularis. In the other nonsquamate lepidosauromorphs (for which this char- Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Sphenodontida and other nonsquamate lepidosauromorphs in acter can be determined), including the Jurassic burrowing which this character is known, the epipterygoid is well diapsid Tamnulipasaurus morenoi. ossified. (xvii) Fused basioccipital-basisphenoid complex in adult (xii) Large, laterally placed fenestra ovalis (Rieppel 1984; (Gans 1978): In 1 iving amphisbaenians, the basiocci pi tal- Greer 1985)(Fig. 5D): This character does not occur in the basisphenoid suture remains open in juveniles and becomes Sphenodontida (Wu 1991). The condition in other nonsqua- fused in adults, as it does in S. hexurahmlaris (Figs. 5B, 5D). mate lepidosauromorphs is unknown. A small skull of Amphishaena alba (MCZ 54299) has (xiii) Closure of recessus scalae tympani (Rieppel 1984; separate basioccipital and basisphenoid (Fig. 12%).but these Greer 1985): The recessus scalae tympani is located in the bones are completely fused in a large skull of the same exoccipital and merges ventrally with the large spheno- species (MCZ 165208). This is also the caqe in the fossil occipital recess in the basioccipital. The occipital recess may species Spathoriiynchusfossonum. where the suture is absent be the equivalent of the recessus scalae tympani + spheno- in the holotype WSNM 263 17) but open in the smaller pam- Wu et al.

type (USNM 26318). In the Sphenodontida, the basioccipital- of the cranium is short; (vi) all dermal elements of the basisphenoid suture remains open (Carroll 1985; Whiteside cranium except the supratemporal are retained; (vii) the der- 1986; Wu 1991). mal cranium is not fully fused with the braincase; (viii) the (xviii) Subdental shelf small or lost (Estes et al. 1988): anterior dermal bones of the cranial roof are weakly inter- The presence of a small subdental shelf in S. hexatabularis digitated; (in) the prefrontal contacts the nasal; (x) the parie- is suggested by a thin, concave medial surface of the dentary, tal~are paired; (xi) the descending process of the parietal is which is preserved in the paratypic skull (Fig. 5B). In addi- narrow; (xii) the jugal has a pronounced posteroventral tion to all known amphisbaenians and some squamates, this process; (xiii) the exoccipital is partially sutured to the primitive feature is widespread in nonsquamate lepidosauro- opisthotic; (xiv) the ventral surface of the basisphenoid is morphs. However, Estes et al. (1988) argued that this longer than that of the basioccipital; (xv) the basipterygoid character is secondarily achieved within the Squamata. process is well developed; (xvi) the parasphenoid cultriform (xix) Loss of conch on quadrate (Fig. 6A): In most lizards process is small; (xvii) the postdentary elements of the man- a conch-like structure is formed on the lateral surface of the dible are sutured with one another; (xviii) the anterior quadrate. This is also the case in the Jurassic burrowing diap- embayment of the coracoid is present; (xix) the interclavicle sid Tamaulipasaurus morenoi. The quadrate conch is entirely is present; (xx) the ectepicondylar foramen is present on the eliminated in all known amphisbaenians (Fig. 11C). Within humerus; (xxi) neural spines of the dorsal vertebrae are dis- the Sphenodontida, early fossil taxa have the quadrate conch, tinct; and (xxii) ribs lack an additional process posterior to although the squamosal and quadratojugal join the formation the articular head. of the tympanic frame of the conch (Evans 1980; Fraser In all of the other known amphisbaenians in which the 1982; Whiteside 1986; Wu 1991, 1994). The loss of the condition can be determined, each of the above characters conch in later and living sphenodontidans is believed to be shows, with very few exceptions, a derived state. In some, secondary (Whiteside 1986; Wu 1991). The more remote sis- the naris is very small and located at the anterolateral end of ter group Kuehneosauridae has a quadrate almost identical in the snout, facing ventrolaterally, whereas in others it moves morphology to that of typical lizards (Robinson 1962; to the anteroventral end and faces completely ventrally. The Colbert 1970). orbit is greatly reduced in size, and generally its posterior (xx) Cervical intercentrum attached or fused to preceding border is lost. None retain the supratemporal fenestra and its centrum (Estes et al. 1988): An articular facet on the postero- arcade, although most of the relevant bones are still present ventral edge of the first seven cervical centra of the holotype in a few fossil taxa, such as Hyporhina (Gilmore 1928; in S. hexatabularis is considered evidence for the presence Taylor 195 I), Spathorhynchus (Berman 1973, 1977), and of a hypapophysis (intercentrum) between these cervicals, Dyticonastis (Berman 1976). The snout is strongly inclined which articulates with the preceding centrum (Fig. 8B). The anteroventrally and sometimes becomes keeled or spade- cervical intercentrum is completely fused to the preceding shaped, and the postorbital portion of the cranium is greatly centrum in other amphisbaenians. According to Estes et al. elongated, so as to be much longer than the snout. A few fos-

For personal use only. (1988), neither a sutured nor a fused state of this character sil taxa retain the postfrontal or postorbital or both, and occurs in nonsquamate lepidosauromorphs for which the squamosal, but the lacrimal and jugal are lost. The dermal condition can be determined. cranium is firmly fixed to the dorsal surface of the braincase (xxi) Parietal foramen closed (Estes et al. 1988) (Fig. 5C). by means of an extensive overlapping contact. Anteriorly, This is typically the case in amphisbaenians, although a the dermal bones are interlocked by a complex interdigitating parietal foramen is retained in a few species of Monopeltis sutural pattern. With the loss of the lacrimal and jugal, the (Gans 1978). It is commonly present in nonsquamate maxilla reaches the border of the orbit and often forms its lepidosauromorphs, although it is closed in the Jurassic bur- entire ventral border (the authors' personal observation). rowing diapsid Tamaulipasaurus morenoi. Although the prefrontal -nasal contact is present in Amphis- (xxii) Ten or fewer maxillary and dentary teeth (Fig. 5B): baena alba (Zangerl 1944, Figs. 1A; MCZ 54299, 165208), A low tooth count of the dentary is one of the major charac- it is absent in all other amphisbaenians. The descending ters on which a supposed Paleocene lizard, Oligodontosaurus process of the parietal is huge, sheet-like, and largely con- wyomingensis Gilmore, 1942a (represented by a jaw), was tributes to the dorsal and lateral walls of the elongated brain- reassigned by Estes (1965) to the Amphisbaenia. All known case. The exoccipital and opisthotic are entirely fused. The Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 fossil and living amphisbaenians have a low tooth count in epiphysial ossification that is developed at the ends of the both the dentary and the maxilla. Nonsquamate lepidosauro- basioccipital - basisphenoid suture can be used to indicate morphs have more than 10 teeth on both dentary and maxilla, the boundary between these two bones in adults. Using this except for the Jurassic burrowing diapsid Tamaulipasaurus as a basis, the basisphenoid (post-parabasisphenoid process) morenoi. is shorter than the basioccipital (Fig. 12B). In addition, the parasphenoid cultriform process is greatly enlarged or broad- Plesiomorphic characters ened, so its boundary with the reduced basipterygoid process Sineoamphisbaena hexatabularis is primitive relative to is ambiguous and the pyriform recess (the interpterygoid other amphisbaenians in the following characters: (i) the vacuity) is closed. In some fossil taxa, the surangular is naris is relatively large and dorsolaterally positioned; (ii) the independent of the co-ossification of the remaining post- orbit is relatively large and complete; (iii) the supratemporal dentary elements, but generally these elements are fused. fenestra and supratemporal arcade are present; (iv) the snout The anterior emargination of the coracoid, the interclavicle, is not strongly ventrally deflected; (v) the postorbital region and the ectepicondylar foramen on the humerus are lost in Can. J. Earth Sci. Vol. 33, 1996

Bipes, the only taxon other than S. hexatabularis that retains separates the premaxilla from the external naris in S. hexa- a pectoral girdle and forelimbs. The neural spines of the tabularis, as in some other amphisbaenians, for example, dorsal vertebrae are shorter. Like many fossorial or burrow- Rhineura hatcheri (UKMNH 8220) and Rhineura jloridana ing lizards, ribs develop an additional process from the (MCZ 4337). In Spathorhynchus fossorium (USNM 2637 I), posterior margin of the proximal head in all living and fossil Spathorhynchus natronicus (AMNH 8677), Ototriton solidus amphisbaenians for which this character is known. (ACM 3639), and Dyticonastis rensbergeri (UCMP 76881 (V6630)), the premaxilla is nearly excluded from the exter- nal naris. This character is obviously derived within the Characters variable within Amphisbaenia Amphisbaenia. (i)Maxilla excluded from orbit (Figs. 6A, 6C). The maxilla (v) Absence of dorsal process of dentary covering antero- forms the anteroventral border of the orbit in the two succes- lateral surface of coronoid (Fig. 5B): As in S. hexatabularis, sive sister groups of the Squamata, the Kuehneosauridae and the dentary does not have a dorsal (coronoid) process that the Sphenodontida. Thus, the separation of the maxilla from overlaps the coronoid in all other fossil amphisbaenians, the orbit in some squamates is a reversed condition within the except Oligodontosaurus wyorningensis (Estes 1983, Fig. 49C) group. This character is not applicable to most later forms of and all living species of Rhineura (Estes 1983). The dentary the Amphisbaenia, because of the reduction of the orbit and of the Paleocene 0. wyomingensis and all other living relevant bones. It varies in the amphisbaenians that retain a amphisbaenian species develops a narrow but distinct dorsal complete orbit; that is, the maxilla enters the orbit in Dyti- process extending along the anterolateral surface of the coro- conastis rensbergeri, Hyporhina galbreathi (Taylor 1951, noid, as it does in many lizards. The absence of the dorsal Fig. 2A), and Spathorhynchus fossorium, but is separated process of the dentary is a primitive condition for the from the orbit by the jugal-prefrontal contact in Spatho- Squamata. rhynchus natronicus (the authors' personal observation). (vi) Acrodont dentition (Fig. 5B). A group of living (ii) Ventral premaxillary foramen located within maxilla amphisbaenians with acrodont dentition has been identified (Figs. 4A, 5A): The ventral premaxillary foramen is gener- (Gans 1960). This is a derived character within the Squa- ally positioned in the premaxilla in squamates. The location mata, although we do not think that the acrodont dentition of this foramen is the same in other fossil and living amphis- suggests a close relationship between S. hexatabularis and baenians that we examined, although it shifts from the the living amphisbaenians with acrodont teeth, because of the anterolateral surface to the anteroventral surface when the large number of derived characters indicating a relationship external nares face ventrally (Estes 1983, Figs. 51C, 51D). between living amphisbaenians exclusive of Sineoamphis- The location of the foramen at the maxilla may be unique to baena. S. hexatabularis within the Squamata. However, a broader (vii) Relatively high tooth count of dentary, premaxilla, investigation of this character within the Amphisbaenia is and maxilla (Fig. 5B). The tooth count of the dentary of needed before confirming this postulation. S. hexatabularis, Oligodontosaurus wyomingensis, and (iii) Posterior foramen of vidian canal placed within Amphisbaena alba (on the right side (MCZ 165208)) is the For personal use only. basisphenoid (Fig. 7): The location of the posterior foramen highest in the group, each numbering nine. The premaxilla of the vidian canal in the basisphenoid is a primitive condi- and each maxilla also bear nine teeth in S. hexatabularis. In tion within the Lepidosauromorpha (Estes et al. 1988). Two Amphisbaena alba, seven teeth are present in the premaxilla, derived conditions are that this foramen is located at the and five in the maxilla. The tooth count of S. hexatabularis suture of the basisphenoid with the prootic, or lies entirely probably represents the basal condition for the Amphis- within the prootic. The primitive condition of the character baenia. occurs in S. hexatabularis, some other fossil amphisbaenians (viii) Cervical vertebra 3 and axis unfused (Fig. 8): The (such as Spathorhynchus species, Dyticonastis rensbergeri, centrum of cervical vertebra 3 is fused to that of the axis in and Ototriton solidus (the authors' personal observation)), living acrodont amphisbaenians (Gans 1960). The centrum of and the living and fossil species of Rhineura (such as the cervical vertebra 3 is also fused to the axis in a large speci- fossil species R. wilsoni (UKMNH 7651) and the living men of Amphisbaena alba (MCZ 165208). These two ele- species R. jloridana (MCZ 55615)). The two above- ments are unfused in S. hexatabularis, Spathorhynchus mentioned derived conditions of the character are not present fossorium (USNM 263 18), and Dyticonastis rensbergeri

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 in any other species of amphisbaenians that we examined. (UCMP 76881 (V6630)), the only fossil amphisbaenians in However, the posterior foramen of the vidian canal is which an axis is preserved. The separation of the axis and enclosed by the prootic and the epiphysial ossification, just cervical vertebra 3 is a primitive condition. anteroventral to the fenestra ovalis in some living species (such as Amphisbaena alba (MCZ 54299) and Cadea pali- rostrata (MCZ 13508)). This condition is unique within the Phylogenetic relationships Squamata and is probably related to the complete reduction of the basipterygoid process and the great shortening of the A full cladistic study on the phylogenetic relationships of the basisphenoid body in these taxa (Fig. 12B). Amphisbaenia is not possible at present, because problems (iv) Premaxilla excluded from external naris (Figs. 5B, exist regarding the monophyly of many crown taxa of the 4A): In lizards, snakes, and other lepidosauromorphs, the Squarnata (Estes et al. 1988; Kluge 1989), and because there premaxilla consistently contributes to the border of the exter- are no proper methods for evaluating missing data or nonap- nal naris. This is also the case in many amphisbaenians. The plicable data to relevant taxa (especially fossil taxa). There- contact of the maxilla with the nasal medial to the naris fore, the present phylogenetic study relies primarily on the characters that can be scored for S. hexatabularis and pro- Analyses and results duces results that are preliminary. The data matrix used here The plesiomorphic states of all characters of the data matrix includes 107 ostalogical characters (Appendixes I and 7). were artrihuted ro the ancestor of the Lepidosauria for Of these, 85 (characters 1 -85) are taken from the 130 nsteo- computer runs, although some characters are indwidually logical characters used by Estes et al. (19R8), although some rnrc\inp or equivocal for certain taxa of nonlepidosaurian of them are modified in description or state distriburion (see lepidosaurnrnorphs (see Estes et al. 1988). Because of the Appendixes 2 and 3). The remaining characters are new large data matrix, we performed two analyses using the (characters 86- 107), including those that were not consid- heuristic alporithm (general searching options) of PAUP ered by Estes et al. (1988) in computer runs owing to the version 3. l .I (Swofford 1993). The first analysis with all the reflection of a burrowing mode of life. The 18 soft ana- taxa included yielded 28 equally parsimonmus trees (with a tomical characters employed by Estes et al. (1988) are not tree length (TL) of 316. a consistency index (CJ) of 0.389, included, because of the large number of fossil taxa used in and a retention index (RI) of 0.561 ). As shown in the strict this study. The autapomorphies of each taxon are excluded consensus tree of the 28 trees (Fig. 13A). the monophyly of as well, because they do not help resolve the relationships of the Arnphisbaenia including Sineoamphisbaena is unequivo- the taxa in question. cal. hut relationships among the nonnnguimorph squamates Within the Lepidosauromorpha, phylopenetic relation- are poorly resolved. Nineteen of the 2R trees suppoa an ships of the outgroups of the Squnmata are well established Amphisbacnia- Dibarnidae relationship within a menophy- (Gauthier et ai. 1988: Evans 1988). The characters r 1 -85) lctic group including the Gekkota and snakes (this group is from the investigation of Estes el al. (19881 change little with the sister taxon of the Autarchogln~sa(the Scincomorpha regard to polarity. We employed the Younginiformcs. the plus Anguimorpha) in 9 of the 19 trees (topologically similar Kuehneosauridae, and Sphenodontida as sequential out- In that of Fig. 14A). is related to the Scincon~orphawithin groups ror polarizing the newly added characters within the a monophyletic taxon in 8 of the 19 trees, or closely linked Squamata, although we did not include the former two in to the Anguimorpha in 1 of the 19 trees. respectively), Appendix 2. Following Estes et al. (19&8),two conventinns whereas the remaining 9 trees suggest an Amphisbaenia- arc used for polarizing characters: (i) if both plesiornorphic Macroccphalosauridae relationship within the monophyletic and apomorphic states occur in a taxon. then the plesio- Scincomorpha (topologically resembling those of Figs. 13B morphic state is scored for that taxon; the apomorphic state and 14B). is assumed to have evolved within the group. and this Numerous lizard-like features suggest that Sineoamphis- requires the fewest ad hoc hypotheses to explain its distribu- baena is the most primitive taxon of the Amphisbaenia yet tion (Farris 1983); or (ii) the apomorphic state is scored known and is still too general in morphology to be placed in when established relationships within the taxon have demon- any of the later groups. Once Sitreormiphish~te~~ahad been strated that the plesiomorphic state has been acquired by consistently referred to the Amphisbaenia, we used this reversal (see Estes ct al. 1988, pp. 125-1281, spc~icsas the representative of the Amphisbaenia. because of The ingroup taxa considered in this study consist of 19 its primitiveness. and reanalysed the data matrix, with the six

For personal use only. squarnate families or genera used by Estes et al. (19881, arnphrsbaenian autapomorphies (characters 86 -9 1 3 climi- Sineoampkisbama, and six fossil taxa represented by rela- na~ed.Kine equally parsimonious trees were obtained (with tively well preserved material and originally referred to the a tree length of 298. a consistency index of 0.379. and a Scincomorpha (Appendix 2). The definitions of each taxon of' retention Index of 0.544). This analysis produced a better the ingroup and the taxa at higher levels follow those of Estes resolution of relationships among the tam. In the strict con- et a!. (1988) except for the Teiidae. Amphisbaenia. and the sensus tree of the nine tree?, the Amphisbaenia (represented newly added fossil taxa. Three Fossil taxa are from the hy Sirienantphishu~na)- Macrocephalosauridae relationsh~p Teiidae: the Macrocephalosauridae (Sulimski 1975). Puly- within the monophyletic Scincomorpha is further demon- glyphanodontidae [Sulimski 1975). and the genus Arlumi- stra~ed,and the Dibamidne and snakes form the successive snunrs (representing the Adamisauridae, Sulirnski 1978). We sister groups to the Gekkota. For Lhe strict consensus tree of followed the original definitions of the three families and this anal>s~s.a list of synapomorphies by character numbers treated them as separate taxa. because the palate, maxilla. for each node and terminal taxa is given (Fig. 13B). and temporal region of these taxa are significantly different. Tn rest the robustness ot the abovc-mentioned clado- Three additional fossil taxa are Globaura and Eoxanra gram<. we also tried two analyses Tor which the data matrix Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 (Borsuk-Bialynicka 1988) and Slavoia (Sulimski 1984). They consisted of 170 characters. including thc remaining 45 osteo- are all from the Upper Cretaceous of Central Asia. We use logical features and the 18 soft anatomical characlers used by the taxon "Other Amphisbaenians" to include amphisbae- Estes et al. in 1988 (see Appendix 4 for data information on nians exclusive of Sin~onnzphisbocna.This category is there- the nculy added taxa in th~sstudy). With no taxa eliminated. fore equivalent to the Amphisbaenia of Estes et ai. 1 1988). the first analysis yields twn equally parsimonious mees (with The taxan Amphisbaenia as used here includes the Other a tree length of 512. a consistency index of 0.398, and a Amphishaenians and Sineoa~ty#iisbaena.Additionally. the retention index of 0.5763) (Fig. 14A). The results of this anal- taxon Sphenodontida (Wu 1991. 1994) used here is equiva- ysis resemble those supported by some of 28 trees derived lent to the Rhynchocephalia of Estes et al. (1988) and from ihe first analysis of 107 characters. However. the replaces the genus Sphenoh as the first out-group. This is rewlts of the second analysis (Fig. 14B). in which the because recent studies have shown that the living genus Amphisbaenia was represented only by Sineoampltisbucna, Spherwdon is highly derived (Whiteside 1486; Wu 1991. are similar to those derived frum the above second analysis 1994). (without the taxan Other Amphisbaenians) based on 107 char- Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 For personal use only.

m D

I SPHENODONTIDA 1 SPHENODONTIDA

IGUANIDAE ANGUIDAE HELODERMATIDAE HELODERMATIDAE - E LANTHANOTUS 3 WAR4NUS XENOSAURIDAE ge XENOSAURIDAE CORDYLIDAE SClNClDAE g CORDXLIDAE 5 SClNClDAE - XANTUSIIOAE XANTUSIIDAE EOXANTA EOMMA - ADAMlSAURUS 0m ADMiSAURUS SLA VUtA 0z m VOIA GLOBAURA DIBAMIDAE g GLOBAUR4 - GXMNOPHTHALMIDAE GEKKONlDAE TEllDAE PYGOPODIDAE r LACERTIDAE GYMNOPHTHALMIDAE SINEOAMPHISBAENA TEllDAE T+,K MACROCEPHALOSAURIDAE LACERTIDAE 'CD POLYGLYPHANODONTIDAE OTHER AMPHISBAENIANS

1- 1- DIBAMIDAE SINEOAMPHISBAENA GEKKONlDAE SNAKES ;E;;yDAE MACROCEPHALOSAURIDAE 4-w POLYGLYPHANODOKTIDAE ANCESTOR IGUANIDAE ANCESTOR Wu et al. 565

Fig. 13. (A) Strict consensus tree of the 28 equally parsimonious trees (with TL of 316, CI of 0.389, RI of 0.561) produced by analysing 107 characters for all taxa. (B) Strict consensus tree of the 9 equally parsimonious trees (with TL of 298, CI of 0.379, RI of 0.544) derived from the analysis of 107 characters with the taxon Other Amphisbaenians eliminated. For the strict consensus tree (B), synapomorphies by numbers (following those listed in Appendix 1) for the nodes and terminal taxa of the ingroups are given below. All synapomorphies are character state 1 unless otherwise indicated in parentheses. Equivocal synapomorphies (which alter in the level at which they are diagnostic when different optimization procedures are employed) are underlined. Node A: m, 92(0), 93, 96, 97, 100, 101; node B: 33(0), 9,43, 65, 85(0); node C: m,51(0), 80; node D: 18(0), 22, 35(0), 69, node E: 46(0), 63, 73; node F: 81, 82, 83; node G: 18(0),43, 63;node H: UOJ, 30(0), 54, 59; node I: 2, 3, 29(0), 40, 55(2), 57(0), 72(0), 77, 84(0); node J: 3, 10, 16, 25, 26, 340,43, 56, 58, 67(2), 68, 70; node K: 18(0), 50, 640,84; node L: 16, 31, 65, 74, 103; node M: 10, 25, 27, 33, 3,79, 99(2), 104, 105(2);node N: 12, 65, 66, 67(3), 74; Squamata: 1, 21, 24, 2,46, 48, 64, 71, 75, 78, 92; Iguania: 6-8, 15,47, 62; Scleroglossa: 9, 13,32, 37, 38, 39, 42, 3,85, 99;Gekkota: 6, 21(0), 40(0), 49, 51, 57, 61, 105(0);Autarchoglossa: 17, 3,57, 84(2); Anguimorpha: 34, 52, 53(0), 55(0), 67, 74, 82, 83; Scincomorpha: 4, 23, 51; Agamidae: 33(0), 46(0), 72(0), 99; Chamaeleontidae: 24(0), 36, 45, 47(0), 62(0), 76, 78(0), 79, 80, 95, 98, 107; Iguanidae: 30, 35(0), 64(0); Anguidae: 33(0), 81, 99(0), 101; Helodermatidae: 20, 35(0), 51, 78(0); Lanthanotus: 100,99(0), 102; Varanus: 5(0), 14, 16(0), 25(0), 31, 34, 50(0), 64, 65, 82(0), 83(0); Xenosauridae: 7, 24(0), 32(0); Cordylidae: 1, m, 18(0), 19, 24(0); Scincidae: 20, 23(0), 34, 41; Xantusiidae: 12, 19, 21(0), 22, 24(0), 26, 36, 49, 57(0), 60, 630,84(2); Adamisaurus: 32(0), 37(0), 46(0), 92(0), 102; Globaura: 6, 7, 44(0); Slavoia: 5, 26, 3,76, 98, 102; Gymnophthalmidae: 6, 10, 11, 25, 53(0), 99; Teiidae: 9(0), 32(0), 43, 44, 72(0); Lacertidae: 12, 20, 23(0), 24(0), 30(0), 34, 50, 83; Sineoamphisbaena: 5, 10, 13(0), 14, 21(0), 23(2), 25, 28, 45, 46, 48(0), 51(0), 53(0), 63(0), 66, 67(3), 73(0), 74, 94(2), 95, 98, 102, 103, 105, 106, 107; Polyglyphanodontidae: 32(0), 44, 80; Dibamidae: 4, m,22, 23(3), 26, 41, 42, 48(0), 50(2), 54, 60, 67, 76, 95, 98, 102, 106; Gekkonidae: 1(0), 71(0), 75(0), 79(0), 99(0); Pygopodidae: 36, 78(0); Snakes: 13(0),23(4), 45, 56, 640,67(2), 72(0), 73, 94.

acters (Fig. 13B). Again, the Amphisbaenia (represented by 1983, Fig. 5 1C). In other extant amphisbaenians, these two Sineoamphisbaena) - Macrocephalosauridae relationship bones approach one another but do not meet (Fig. 15D). The was recognized within the monophyletic Scincomorpha. extensive posterior elongation of the vomer beyond the tooth row of the maxilla and the large palatal ramus of the Discussion pterygoid suggest that this contact existed in Sineoamphis- The analyses presented above strongly support the contention baena in life (see above). In other squamates, this contact that Sineoamphisbaena is an amphisbaenian. According to only occurs in Adamisaurus, where it results from the tree 15 of the first analysis based on 107 characters, a extreme anterior elongation of the palatal ramus of the monophyletic Amphisbaenia, including Sineoamphisbaena, pterygoid (Sulimski 1978, Fig. lc). can be diagnosed by 26 characters, as recognized by ACC- Character 93-presence of a lateral process of palatal

For personal use only. TRAN optimization. These include 22 unequivocal charac- ramus of pterygoid (unique, but see below). The lateral ters (characters 5, 10, 13(0), 28, 45, 51(0), 53(0), 63(0), process ofthe palatal ramus of the pterygoid is elongate, 73(0), 74, 86, 87, 88, 89, 90, 91, 94(2), 95, 102, 103, 106, extending anterolaterally along the lateral edge of the pala- 107) and four equivocal characters (characters 23(2), 46, 67, tine in Sineoamphisbaena and other arnphisbaenians (Figs. 4B, 105), meaning the level at which it is diagnostic differs when 15B- 15D). This process is relatively short but distinct in the different optimization procedures are employed. Of the 22 two genera of the Macrocephalosauridae (Fig. 15A; see also unequivocal characters, seven are autapomorphic for the Sulimski 1975, Figs. 2C, 4A2, 5A2, 12B5). In some indi- Am~hisbaenia. viduals of the polyglyphanodontid Cherminsaurus, a small The Amphisbaenia - Macrocephalosauridae relationship lateral process of the palatal ramus of the pterygoid is formed (as recognized by two analyses for which the Amphisbaenia along the lateral edge of the palatine (Fig. 15E; see also is represented only by Sineoamphisbaena) is supported Sulimski 1975, Fig. 13A3), showing the only example of primarily by the following six unequivocal characters (of the presence of the process within the other squamates. This which four are unique). process is absent in other individuals of Cherminsaurus and Character 92(0)-contact of pterygoid with vomer. As the other polyglyphanodontids (Gilmore 19426, Fig. 19). Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Sulimski (1975) pointed out, the pterygoid-vomer contact Character 96-suborbital fenestra entirely closed by the in the Macrocephalosauridae (Fig. 15A) is a primitive state lateral process of palatal ramus of pterygoid (unique): In both within the Squamata. This conclusion is supported by the the Amphisbaenia and Macrocephalosauridae, the lateral widespread occurrence of this feature in nonsquamate lepido- process of the palatal ramus of the pterygoid meets the sauromorphs. However, the phylogenetic analysis presented ectopterygoid laterally, so the suborbital fenestra is closed here supports the suggestion of Estes et al. (1988) that this (Figs. 15A- 15D). In contrast, the lateral process forms part contact is an apomorphic reversal for the taxa within the of the medial border of the suborbital fenestra in some Squamata. The pterygoid -vomer contact is present in fossil individuals of Cherminsaurus of the Polyglyphanodontidae amphisbaenians for which the condition can be determined (Fig. 15E). The closure of the suborbital fenestra in some (Figs. 15B, 15C; Estes 1983, Figs. 49-51), and in the taxa of the Xantusiidae, such as Lepidophyma (Borsuk- extant Rhineura. Our reexamination of the holotypic speci- Bialynicka 1988, Fig. I), differs in that it is a result of the men shows that the pterygoid meets the vomer in fossil posterior contact of the ectopterygoid with the palatine, and Dyticonastis rensbergeri, in contrast to the previous view does not involve the pterygoid. that these two bones fail to contact one another (see Estes Character 97-dorsal portion of maxilla partially expand- Can. J. Earth Sci. Vol. 33, 1996

Fig. 14. (A) Strict consensus tree of the 2 equally parsimonious trees (with TL of 512, CI of 0.398, RI of 0.576) generated by analysing 170 characters with all taxa included. (B) Strict consensus tree of 4 equally parsimonious trees (with TL of 487, CI of 0.400, RI of 0.569) yielded by the analysis of 164 (with 6 autapomorphies of the Amphisbaenia eliminated) character with the taxon Other Amphisbaenians excluded. For personal use only. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Wu et al. 567

Fig. 15. Skulls and palate of relevant squamates in ventral views. (A) A Cretaceous macrocephalosaurid lizard, Macrocephalosaurus gilmorei (after Sulimski 1975, Fig. 4a). (B) A fossil amphisbaenian Spathorhynchus fossorium (after Berman 1973, Fig. IF). (C) A fossil amphisbaenian, Hyporhina galbreathi (after Taylor 1951, Fig. 2C). (D) A living amphisbaenian, Bipes biporus (MCZ 145823). (E) The palate of a Cretaceous polyglyphanodontid lizard, Cherminsaurus kozlowskii (after Sulimski 1975, Fig. 13A3). Not drawn to scale. Abbreviations as in Fig. 1.

Fig. 16. Skulls of relevant squamates in dorsal view. (A) Sineoamphisbaena hexatabularis. (B) A Cretaceous macrocephalosaurid lizard, Darchansaurus estesi (after Sulimski 1975, Fig. 12B). (C) A Cretaceous adamisaurid lizard, Adamisaurus magnidentatus (after Sulimski 1978, Fig. 1B. (D) A Cretaceous polyglyphanodontid lizard, Polyglyphanodon sternbergi (after Gilmore 19426, Fig. 17). Not drawn to scale. spt, supratemporal. Other abbreviations as in Fig. 1. For personal use only.

ing dorsolaterally or bulging laterally, overhanging the tinct in some burrowing scincid lizards, such as acontines dental margin (unique). In Sineoamphisbaena, the postero- and feylinids (Rieppel 1981, Figs. 1-4, 7-9, 13, 14). dorsal portion of the maxilla is laterally expanded and over- Thus, the dorsolateral expansion of the maxilla is inde-

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 hangs the dental margin (Figs. 4B-4D). This is similar to pendently achieved within some families of lizards as an the condition seen in living acrodont amphisbaenians, where adaptation to a burrowing or fossorial way of life. The the external nares are anteroventral in position, and the Macrocephalosauridae are the only nonburrowing lizards anterodorsal portion of the maxilla is largely expanded later- that have the dorsolateral expansion of the maxilla, and the ally (Gans 1960, Figs. 9, 11, 12, 15). In the extant Bipes and Amphisbaenia is the only squamate group in which most some fossil forms, the dorsal portion of the maxilla bulges members have a dorsolaterally expanded or bulged maxilla. distinctly laterally (Figs. 15B-15D; see also Estes 1983, Character 100-postorbital large, posteriorly broad, extend- Figs. 49 -51). The dorsolateral expansion of the maxilla is ing posteriorly beyond supratemporal fenestra, and approach- very strong in the two genera of the Macrocephalosauridae ing posterior edge of dermal cranial roof (unique): This (Fig. 15; see also Sulimski 1975, Figs. 2 -4, 12; Estes 1983, character is not applicable to amphisbaenians other than Figs. 15B, 16). In the other squamates, the anterodorsal Sineoamphisbaena, because of the loss of the supratemporal expansion or bulge of the maxilla occurs in a fossorial fenestra, and is not applicable to those taxa in which the pygopodid, Aprasia striolata (Rieppel 1984, Fig. 9). The supratemporal fenestra is entirely closed. It was argued lateral bulge of the dorsal portion of the maxilla is not dis- above that the large bone flanking the posterolateral dermal Can. J. Earth Sci. Vol. 33, 1996

cranial roof in Sineoamphisbaena is a fused postorbital- localities, two of Maastrichtian age and one of Albian age. postfrontal complex. We believe that the orbital portion of An amphisbaenian was included in a list of fossil lizard taxa the complex is the postfrontal, and the temporal portion is the from the Barun Goyot Formation, which is thought to be postorbital. In squamates that retain a supratemporal fenes- Maastrichtian in age (Borsuk-Bialynicka 1991), although the tra, only Sineoamphisbaena and the Macrocephalosauridae material remains undescribed. An amphisbaenian was also possess this character. In these taxa, the postorbital is not reported from Maastrichtian deposits at Laiio, south Spain only broadened posteriorly to form the major portion of the (Astibia et al. 1991). This report is based on five proceolous supratemporal arcade but also greatly extends posteriorly vertebrae that lack neural spines. Recently, Hodzhakulia along the lateral border of the supratemporal fenestra to magma Nessov, 1985 was identified as an amphisbaenian by almost reach the posterolateral edge of the dermal cranial Nessov and Gao (1993). This species is also represented by roof (Figs. 16A, 16B). A large postorbital is one of the diag- fragmentary material (some incomplete dentaries) from the nostic characters of the ~ac~ocephalosauridaeas defined by uppermost Lower Cretaceous (Albian), Kyzylkumy Desert Sulimski (1975), but Estes (1983) believed that this character of Central Asia (Nessov 1985, P1. I, Figs. 4-6). showed much intergradation among the members of the The occurrence of both the earliest known amphisbae- Macrocephalosauridae, Polyglyphanodontidae, and Adami- nians and the supposed sister group of the Amphisbaenia in sauridae. However, the postorbital in the latter two is differ- Central Asia suggests that this may have been the area in ent from that in the former in that the bone ends at or beyond which the Arnphisbaenia evolved. Sedimentological evidence the midpoint of the supratemporal arcade, just as it does in shows that the northern part of Chinese Inner Mongolia and many other squamates, and posteriorly it tapers off and never the southern part of People's Republic of Mongolia were reaches the posterolateral border of the supratemporal fenes- dominated by semiarid eolian depositional conditions during tra (Figs. 16C, 16D; see also Estes 1983, Figs. 18A, 19A- the Campanian (Jerzykiewicz et al. 1993; Eberth 1993). The 19C). In Ophisaurus apodus (the Anguidae), the postorbital Amphisbaenia may be associated to the development of a extends posteriorly well beyond the anteriorly positioned fossorial mode of life during the transition from perennial supratemporal fenestra, but it is relatively small, posteriorly lacustrine condition of the Early Cretaceous - early Late pointed, and widely separated from the posterior edge of the Cretaceous to a dry, semiarid eolian environment of the dermal cranial roof (Estes et al. 1988, Fig. 28). In most other middle Late Cretaceous. Fossorial adaptations of Sineo- anguids, the condition of the postorbital resembles that of amphisbaena are well demonstrated by the structural special- most squamates (Rieppel 1980, Figs. 16, 18). izations of its skull. As in later amphisbaenians and other Character 101 -squamosal excluded from supratemporal burrowing or fossorial squamates, the orbit is small and faces fenestra by contact of postorbital with parietal or with posterolaterally, the posttemporal fenestra is completely supratemporal (unique, except for Ophisaurus and Varanus closed, so the dermal cranium largely contacts the braincase, dumerilli). This character is also not applicable to the taxa the otic capsule is greatly enlarged, the tympanum, middle that lack the supratemporal fenestra. The postorbital -parietal ear chamber, and fenestra rotundum are lost, the fenestra contact separates the squamosal from the supratemporal ovalis is large, and the stapes is massive. For personal use only. fenestra in Sineoamphisbaena, a situation similar to that seen Sineoamphisbaena is much less specialized than later in Ophisaurus apodus, but unlike the condition in other amphisbaenians in retaining well-developed limbs and dis- anguids (Rieppel 1980). The failure of the squamosal to enter tinct neural spines of the dorsal vertebrae. Thus it may not into the supratemporal fenestra is a result of the contact of have been a fully subterranean dweller. Like many snakes the postorbital with the supratemporal in the Macrocephalo- and many burrowing lizards, Sineoamphisbaena may have sauridae. It is present in Varanus dumerilli (the authors' frequently emerged on the surface. All of the later amphis- personal observation). As described below, the squamosal is baenians are permanent burrowers that construct their own fused with the supratemporal in adults of the Macrocephalo- tunnels in compact soils (Gans 1969), rather than utilizing sauridae and Polyglyphanodontidae. The ontogenetic evi- previously existing tunnels or underground nests (like the dence shows that when the squamosal remains separate, it worm-like snakes), or occupying only loose sands and soils. never enters into the border of the supratemporal fenestra A series of features of later amphisbaenians reveal them to in the Macrocephalosauridae (Estes 1983, Figs. 19D - l9F), be more specialized for burrowing: the supratemporal fenes- in contrast to the condition in Polyglyphanodontidae (Estes tra and supratemporal arcade are lost, the postorbital region 1983, Figs. 19A- 19C) and other lizards. of the cranium is greatly elongated, the orbit is small and Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 We have not attempted here to detail the relationships of faces posteriorly, the snout is of various shapes (being the other ingroup taxa, which are indicated in the consensus shovel-shaped or keeled or bluntly pointed), the external trees (Figs. 13, 14). However, it is noticeable that the naris is terminal or anteroventral in position, the limbs are Dibamidae and snakes have been almost always linked to generally lost, and the body is greatly elongated and cylindri- the Gekkota in a monophyletic group in each-of the four cal in shape. analyses. The consolidation of the skull, a unique feature of the Amphisbaenia within the Squamata, is probably associated Origin and early adaptation of the with the use of the head skeleton for burrowing (Gans 1969, Amphisbaenia 1978; Wake 1993). Since Sineoamphisbaena already pos- sesses the amphisbaenian-type skull consolidation, the head Sineoamphisbaena, from the Campanian redbeds, is the skeleton had already become an important tool in burrowing. oldest well-documented record of an arnphisbaenian. Previ- In Sineoamphisbaena, the short and broad skull, with a well- ously, the group has been reported from three Cretaceous developed massive and heavily rugose interorbital cranial Wu et al.

table that is angled with the postorbital region and faces fossil vertebrates from Lafio (Basque County, Spain); new evi- anterodorsally, can be interpreted as being adapted for bur- dence on the composition and affinities of the Late Cretaceous rowing in the sandy environment in which it was found. continental faunas of Europe. Terra Nova, 2: 460-466. Sineoamphisbaena may have utilized its forelimbs to initiate Bellairs, A.d'A., and Gans, C. 1983. A reinterpretation of the amphisbaenian orbitosphenoid. Nature (London), 302: 243 -244. and dig the tunnels, and may have employed the strong Bellairs, A.d'A., and Kamal, A. 1981. The chondrocranium and interorbital table of the skull to ram or compact their loosely the development of the skull in recent reptiles. In Biology of the cemented sandy walls in the eolian dune deposits. Reptilia 11 (Morphology F). Edited by C. Gans and T. Parsons. The isolation of Central Asia during the Middle-Late Academic Press, London and New York, pp. 1 -226. Jurassic ended by the Aptian-Albian time of the Early Berman, D.S. 1973. Spathorhynchus fossorium, a Middle Eocene Cretaceous (Russell 1993). North America was subdivided amphisbaenian (Reptilia) from Whamming. Copeia, 4: 704- by an interior seaway into western and eastern parts during 721. most of the Late Cretaceous, and the land mass of the Berman, D.S. 1976. A new amphisbaenian (Reptilia: Amphis- western part was relatively smaller than that of Central Asia. baenia) from the Oligocene-Miocene John Day Formation, Europe was also subdivided into smaller land masses. Oregon. Journal of Paleontology, 50: 165 - 174. According to Marshall (1988), the predominant direction of Berman, D. S. 1977. Spathorhynchus natronicus, a new species of rhineurid amphisbaenian (Reptilia) from the Early Oligocene of the dispersal of organisms between lands is from the larger Wyoming. Journal of Paleontology, 51: 986 - 991. to the smaller. Thus the distribution of fossil amphisbaenians Borsuk-Bialynicka, M. 1988. Globaura venusta gen. et sp. n. and is consistent with their origin in Asia prior to the Campanian Eoxanta lacertifrons gen. et sp. n.-Non-teiid lacertoids from and their subsequent dispersal into Europe and North the Late Cretaceous of Mongolia. Acta palaeontologia polonica, America. If the Lafio vertebrae of Spain represent a true 33(3): 211 -248. amphisbaenian, then the dispersal of amphisbaenians into Borsuk-Bialynicka, M. 1991. Cretaceous lizard occurrences in southern Europe may have occurred during the very early Mongolia. Cretaceous Research, 12: 607 -608. Maastrichtian. No amphisbaenian older than Paleocene has Carroll, R.L. 1985. A pleurosaur from the Lower Jurassic and the been found in North America, so amphisbaenians may have taxonomic position of the Sphenodontida. Paleontographica, dispersed to there about the very late Late Cretaceous or 189: 1-28. Carroll, R.L. 1988. Vertebrate paleontology and evolution. W.H. even the Early Paleocene. The oldest fossil amphisbaenian in Freeman and Company, New York. South America is from the Miocene (Estes 1983). No bar- Clark, J.M., and Hernandez, R. 1994. A new burrowing diapsid riers have been present between Eurasia and Africa since the from the Jurassic La Boca Formation of Tamaulipas, Mexico. late Neogene, but few fossil remains have been found from Journal of Vertebrate Palaeontology , 14: 180 - 19.5. the non-Quaternary deposits of Africa (Estes 1983). Colbert, E. 1970. The Triassic gliding reptile Icarosaurus. Bulletin of the America Museum of Natural History, 143: 85 - 142. Acknowledgments Cui, G. 1991. The smallest ankylosaurian skeleton in the World. China Pictorial, 4: 16- 17. (In Chinese.) X.-C. Wu is greatly indebted to the Institute of Vertebrate Eberth, D.A. 1993. Depositional environments and facies transi- Paleontology and Paleoanthropology (IVPP), Academia tions of dinosaur-bearing Upper Cretaceous redbeds at Bayan For personal use only. Sinica, Beijing, People's Republic of China, for permission Mandahu (Inner Mongolia, People's Republic of China). Cana- to study this amphisbaenian. We thank Drs. P.J. Currie and dian Journal of Earth Sciences, 30: 2196-2213. D.A. Eberth of the Royal Tyrrell Museum of Palaeontology Estes, R. 1965. Notes on some Paleocene lizards. Copeia, 1965: (RTMP) for discussions on paleobiology and sedimentology 104-106. of the fossil locality, and Dr. K. Gao for sharing information Estes, R. 1983. Sauria terrestria, Amphisbaenia. Handbuch der Palaoherpetologie, part 10a. Gustav Fischer Verlag, Stuttgart. and his family for their hospitality during X.-C. Wu's visit Estes, R., Frazzetta, T.H., and Williams, E.E. 1970. Studies on the to the University of Alberta. Drs. D.S. Berman, R.L. Carroll, fossil snakes Dinilysia patagonica Woodward: part I. Cranial and 0. Rieppel reviewed the manuscript and made critical morphology. Bulletin of the Museum of Comparative Zoology, comments and suggestions that improved it significantly. For Harvard University, 140: 25 -74. the loan of specimens, we are grateful to Drs. D.S. Berman Estes, R., Queiroz, K.de, and Gauthier, J. 1988. Phylogenetic rela- (Carnegie Museum of Natural Hislory). J.M. Ctark (Arneri- tionships within squamate reptiles. In Phylogenetic relationships can Museum of Natural History), W. Coombs (Pratr of the lizard families. Edited by R. Estes and G. Pregill. Stan- Museum of Amherst College), P.D. Gingerich (University ford University Press, Stanford, Calif., pp. 119- 183. Evans, S. 1980. The skull of a new eosuchian reptile from the

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 of Michigan Museum of Paleontology 1, N. Hotton IT1 (U.S. National Museum of Natural History. Smithsonian Institu- Lower Jurassic of south Wales. Zoological Journal of the Lin- naean Society, 70: 203 - 264. tion), H. Hutchison (University of California Museum of Evans, S. 1988. The early history and relationships of the Diapsida. Paleontology, Berkeley), D. Miao (University of Kansas In The phylogeny and classification of the Tetrapods. Vol. 1: Museum of Natural History), and Mr. J. Rosado (Museum amphibians, reptiles, birds. Edited by M.J. Benton. Clarendon of Comparative Zoology, Harvard University). Mrs. G. Cui Press, Oxford, pp. 22 1-260. (IVPP) and C. Coy (RTMP) are acknowledged for the excel- Farrjs, J.S. 1983. The logical bases of phylogenetic analysis. In lent preparation of the holotype specimen and the photogra- Advances in Cladistics, Proceeding of the 2nd Meeting of Willi phy, respectively. X.-C. Wu was supported by a University Hennig Society. Edited by N.I. Platnick and V.A. Funk. Colum- of Calgary postdoctoral fellowship. bia University Press, New York, pp. 1-36. Fraser, N. C. 1982. A new rhynchocephalian from the British upper References Trias. Palaeontology , 25: 709 -725. Fraser, N.C. 1988. The osteology and relationships of Clevosaurus Astibia, H.E., Buffetaut, E., Buscalioni, A.D., et al. 1991. The (Repti1ia:Sphenodontida). Philosophical Transactions of the Can. J. Earth Sci. Vol. 33, 1996

Royal Society of London. Series B, 321: 125-178. part 11. Gustav Fischer Verlag, Stuttgart. Gans, C. 1960. Studies on amphisbaenids (Ampbisbaenia, Rep Rieppel, 0. 1978. A functional and phylogenetic interpretation of tilia), I. A taxonomic revision of fhc Trogonophinae. and a the skull of the Erycinae (Reptilia, Serpents). Journal of functional interpretation of the amphisbaenid adaptive pattern. Zoology (1965 - 1984), 186: 185-208. Bulletin of the American Museum of Natural History, 119: Rieppel, 0. 1980. The phylogeny of anguimorph lizards. Denk- 135-204. schriften der Schweizerischen Naturforschenden Gesellschaft, Gans, C. 1967. A check list of recent amphisbaenians (Amphisbae- 94: 1- 96. nia, Reptilia). Bulletin of the American Museum of Natural Rieppel, 0. 1981. The skull and the jaw adductor musculature in History, 135: 61 - 106. some burrowing scincomorph lizards of the genera Acontias, Gans, C. 1969. Amphisbaenians-reptiles specialized for a burrow- Typhlosaurus and Feylinia. Journal of Zoology (1965 - 1984), ing existence. Endeavour, 28: 146- 151. 195: 493 -528. Gans, C. 1978. The characteristics and affinities of the Amphisbae- Rieppei, 0.1984. The cranial morphology of the fossorial lizard nia. Transactions of the Zoological Society of London, 34: genus Dibamus with a consideration of its phylogenetic relation- 347-416. ships. Journal of zoo log^ (1965- 1984). 204: 289-327. Gauthier, J., Estes, R., and Queiroz, K.de. 1988. A phylogenetic Rieppel, 0. 1985. The recessus scalae tympani and its bearing on analysis of Lepidosauromorpha. In Phylogenetic relationships of the classification of reptiles. Journal of Herpetology, 19: 373- the lizard families. Edited by R. Estes and G. Pregill. Stanford 384. University Press, Stanford, Calif., pp. 15 -98. Rieppel, 0. 1987. The phylogenetic relationships within the Gilmore, C.W. 1928. The fossil lizards of North America. Chamaeleonidae, with comments on some aspects of cladistic Memoirs of the National Academy of Sciences, 22: 33-50. analysis. Zoological Journal of the Linnaean Society, 89: Gilmore, C.W. 1942a. Paleocene faunas of the Polecat Bench 41 -62. Formation, Park County, Wharnming. Part 11. Lizards. Pro- Robinson, P. 1962. Gliding lizards from the Upper Keuper of Great ceedings of the American Philosophical Society, 85: 158 - 167. Britain. Proceedings of the Geological Society of London, 1601: Gilmore, C.W. 19426. Osteology of Polyglyphanodon, an Upper 137-146. Cretaceous lizard from Utah. Proceedings of the United States Robinson, P. 1973. A problematic reptile from the British Upper National Museum, 92: 229 -265. Trias. Journal of the Geological Society of London, 129: 457 - Gilmore, C.W., and Jepsen, G. 1945. A new Eocene lizard from 479. Wyoming. Journal of Paleontology, 19: 30-34. Romer, A. 1956. Osteology of the Reptiles. University of Chicago Greer, A. 1985. The relationships of the lizard genera Anelytropsis Press, Chicago. and Dibamus. Journal of Herpetology, 19: 116- 156. Russell, D.A. 1993. The role of Central Asia in dinosaurian Jerzykiewicz, T., and Russell, D.A. 1991. Late Mesozoic stratigra- biogeography. Canadian Journal of Earth Sciences, 30: 2002 - phy and vertebrates of the Gobi Basin. Cretaceous Research, 12: 2012. 345 - 377. Sulimski, A. 1975. Results of the Polish-Mongolian paiaeon- Jerzykiewicz, T., Currie, P.J., Eberth, D.A., Johnston, P.A., tological expeditions-Part Vl. Macmcephalosauridae and Koster, E.H., and Zheng, J.-J. 1993. Djadokta Formation cor- PoIyglyphandontidae {Sauria) from the Late Cretaceous of relative strata in Chinese Inner Mongolia: an overview of the Mongolia. Palaeontologia Polonica, 33: 25 - 102. stratigraphy, sedimentary geology, and paleontology and com- Sulimski. A. 1978. New data on the genus Adamisaurus Sulimski, parisons with the type locality in the pre-Altai Gobi. Canadian 1972 (Sauria) from the Upper Cretaceous of Mongolia. Palaeon- For personal use only. Journal of Earth Sciences, 30: 2180 -2195. tologia Polonica, 38: 43 -56. Kluge, A.G. 1989. Progress in squamate classification. Herpe- Sulimski, A. 1984. A new Cretaceous scincomorph lizard from tologica, 45: 268 -279. Mongolia. Palaeontologia Polonica, 46: 143 - 155. Lakjer, T. 1927. Studien iiber die Gaumenregion bei Sauriern im Swofford. D.L. t993. PAUP, phylogenetic analysis using par- Vergleich rnit Anamniern und primitiven Sauropsiden. Zoologische simony (version 3.1.1). Illinois Natural History Survey. Cham- Jahrbuecher Abteilung fuer Anatomie und Ontogenie der Tiere, paign, Ill. 49: 57-356. Taylor, E. 1951. Concerning Oligocene amphisbaenid reptiles. Lillegraven, J.A., and McKenna, M.C. 1986. Fossil mammals University of Kansas Science Bulletin, 34: 521 -558. from the "Mesaverde" Formation (Late Cretaceous, Judithian) Wake, M.H. 1993. The skull as a locomotor organ. In The skull. of the Bighorn and Wind River Basins, Wyoming, with defini- Vol. 3: functional and evolutionary mechanisms. Edited by tions of Late Cretaceous North American land-mammal J. Hanken and R.K. Hall. The University of' Chicago Press, "Ages." American Museum Novitates, No. 2840. Chicago and London. pp. 215-220. Marshall, L.G. 1988. Land mammals and the great American inter- Whiteside, D.1. 1986. The head skeleton of the Rhaetian spheno- change. American Scientist, 76: 380 - 388. dontid Diphydonrosaurus avonis gen, et sp. nov. and the moder- Nessov, L.A. 1985. Rare bony fish, terrestrial lizards and nizing of a living fossil. Philosophical Transactions of the Royal Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 mammals of the zones of Cretaceous lagoons and coastal Society of London. Series B, 312: 379-430. lowlands of the Kyzylkumy region. Yezhegodnik Vsesoyuznogo Wu, X.-C. 1991. Comparative anatomy and systematics of Meso- Paleontologicheskogo Obshchestva (Yearbook of the all-Union zoic sphenodonbdans. Ph.D. dissertation. McGill University. Paleontological Association), 28: 189-219. (In Russian.) Montrhl . Nessov, L.A., and Gao, K. 1993. Cretaceous lizards from the Wu. X.-C. 1994. ?Late Triassic - Early Jurassic sphenodontidans Kyzylkumy desert, Uzbekhistan. Journal of Vertebrate Paleon- (Clevosaums) from China and the phylogeny of the Sphenodon- tology, W(Supp1. to 3): 51A. (Abstr.) tida. in In the shadow of the dinosaurs: Early Mesozoic Terra- Oelrich, T. 1956. The anatomy of the head of Ctenosaurapectinata pods. Edited by N. Fraser and H.-D. Sues. Cambridge (Iguanidae). Miscellaneous Publications of the Museum of University Press. New York, pp. 38-69. Zoology, University of Michigan, 94: 1 - 122. Wu, X.-C.,Brinkman, D.B., Russcll, A.P., Dang. 2.-M., Currie, Presh, W. 1988. Phylogenetic relationships of the "Scinco- P.J., Hou, L.H.. and Cui, G.H. 1993. Oldest known amphis- morpha." In Phylogenetic relationships of the lizard families. baenian from the Upper Cretaceous of Chinese Inner Mongolia. Edited by R. Estes and G. Pregill. Stanford University Press, Nature (London), 366: 57 - 59. Stanford, Calif., pp. 471 -492. Zangerl, R. 1944. Contribution to the osteology of the skull of the Rage, J.C . 1984. Serpents. Handbuch der Palaoherpetologie, Amphisbaenidae. American Midland Naturalist, 33: 417 -454. Appendix 1 Table Al. List of characters used in this study. Character No. Description

Ontogenetic fusion of premaxillae: paired well into postembryonic ontogeny (0); fused in embryo (1) Bony external naris extent: opening not extended posteriorly, frontal not close to or incorporated into opening (0); opening extended posteriorly, frontal coming close to or incorporated into opening (1) Ontogenetic fusion of nasals: paired well into postembryonic ontogeny (0); fused in embryo (1) Nasal-prefrontal contact: present (0); absent, two bones separated by anterolateral process of frontal, the latter contacting maxilla (1) Prefrontal contact with posterior orbital bones: no contact with postorbital, postfrontal, or fused postorbital-postfrontal above orbit (0); contact with postorbital, postfrontal, or fused postorbital-postfrontal above orbit (1) Ontogenetic fusion of frontals: paired well into postembryonic ontogeny (0); fused in embryo or early in postembryonic ontogeny (1) Lateral borders of frontals: more or less parallel (0); strongly constricted between orbits (1) Frontal shelf: lacking broad shelf below nasals (0); broad shelf underlying nasals present, frontal often exposed dorsolaterally as wedges or spikes (1) Descending processes of frontals: participation in orbitonasal fenestra: weakly developed and prefrontals broadly participating in wide orbitonasal fenestra (0); prominently developed and prefrontals narrowly or not at all in margins of

narrow orbitonasal fenestra (1)~, Median contact of descending processes of frontals: not in contact below olfactory tracts (0); in contact below olfactory tracts (1) Frontal tabs: no tabs (0); frontal tabs projects posteriorly over dorsal surface of parietal (1) Postfrontal: present may be separate or seen to fuse at some stage of ontogeny (0); absent, never seen as a separate element (1) Postfrontal forking: subtriangular, not forked medially (0); semilunate, forked medially, clasping frontoparietal suture (1) Postfrontals fusion: separate or absent (0); fused to postorbital (1) Postfrontal size: extensive, usually not confined to orbital rim (0); reduced, subtriangular, confined to orbital rim (1) Postorbital: present (0); absent (1) Postorbital contribution to posterior border of orbit: forming about one-half of posterior orbital border and primarily an orbital bone with a strong ventral process (0); forming less than one-half of posterior orbital border and primarily a temporal bone with reduced ventral process (1) For personal use only. Jugal-squamosal contact on supratemporal arch: absent (0); present (1) Supratemporal fenestra restriction by postorbital: open or restricted primarily by postfrontal (0); restricted primarily by postorbital (1) Supratemporal fenestra restriction by postfrontal: open or restricted primarily by postorbital (0); restricted primarily by postfrontal (1) Ontogenetic fusion of parietal: paired well into postembryonic ontogeny (0); fused in embryo or early in postembryonic ontogeny (1) Parietal tabs: absent (0); parietal tabs present as thin, triangular structures that extend anteriorly into shallow triangular fossae on the ventral surface of frontals (1) Parietal downgrowths: absent (0); pointed ventral downgrowths extended to (or just medial to) the epipterygoid (1); pointed ventral downgrowths deeply inserted between the obitosphenoid-frontal complex and the prootic (2); broad, sheet-like downgrowths with free ventral contact (3); broad, sheet-like downgrowths with ventral contact with parabasisphenoid (4); broad, sheet-like downgrowths with ventral contact with obitosphenoid and porotic (5) Parietal table and supratemporal process length: table extensive posteriorly, largely obscuring braincase in dorsal view, Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 supratemporal process short (0); braincase exposed broadly in dorsal view below and behind parietal table, supratemporal process long (1) Parietal foramen: present (0); absent (1) Posterior extent of maxilla: extending well back under orbit (0); extending only just beyond anterior edge of orbit (1) Lacrimal: present, either separate or fused to prefrontal (0); absent (1) Lacrimal fusion: separate (0); fused to prefrontal (1) Lacrimal foramen number: double (0); single (1) Anteroventral border of orbit: formed by maxilla with jugal confined to medial surface of maxilla (0); formed by jugal (1) Jugal-postorbital bar: jugal large, postorbital bar complete (0); jugal reduced or absent, postorbital bar incomplete (1) Dorsal process of squamosal: present (0); absent (1) Supratemporal: absent or fused to squamosal (0); present (1) Palpebral ossifications: absent (0); present (1) Pterygoid lappet of quadrate: present (0); absent (1) 572 Can. J. Earth Sci. Vol. 33. 1996

Table A1 (continued).

Character No. Description

Vomer fusion: separate well into postembryonic ontogeny (0); fused in embryo or early postembryonic ontogeny (1) Vomer size: relatively small, extending posteriorly less than half the length of maxillary tooth row (0); elongate posteriorly, extending one-half or more the length of maxillary tooth row and usually restricting internal naris (1) Median contact of septomaxillae: separated by a gap filled by cartilaginous internarial septum (0); septomaxillae meeting or nearly meeting on midline in a raised crest (1) Dorsal expansion of septomaxilla: flat or concave, Jacobson's organ small (0); expanded and convex, reflecting large size of Jacobson's organ (1) Posterior border of opening for Jacobson's organ: not closed by bones ("paleochoanate") (0); closed by bones ("neochoanate") (1) Medial extension of palatine: absent (0); medial extension from ventrolateral edge of palatine forming air passage for bony secondary palate (1) Choanal fossa of palatine: small in relation to palatine size (0); relatively prominent in relation to palatine size (1) Ectopterygoid contact with palatine: failing to contact palatine anteromedially (0); contacting palatine anteromedially (1) Ectopterygoid size and restriction of suborbital fenestra: ectopterygoid relatively slender, fenestra widely open (0); ectopterygoid enlarged medially, restricting suborbital fenestra (1) Epipterygoid: present (0); absent (1) Pyriform recess width: narrow throughout most of its length (0); broad (1); or closed by a broadened parabasisphenoid process (2) Supratrigeminal process of prootic: feebly developed or absent (0); finger-like projection above trigeminal notch (1) Opisthotic-exoccipital fusion: bones remaining separate or fused to exoccipital relatively late in postembryonic ontogeny (0); fused to exoccipital in embryo or in early postembryonic ontogeny, or two bones developed from a single ossification centre (1) Enclosure of lateral head vein in bony canal formed by crista prootica: crista prootica may or may not extend forward onto the basisphenoid process, but does not enclose the lateral head vein in a bony canal (0); crista prootica extends forward onto process, enclosing lateral head vein in a bony canal (1) Posterior opening of vidian canal: within basisphenoid (0); at basisphenoid-prootic suture (1); or entirely within prootic (2); or at suture of prootic with epiphysial ossification (3) Origin of jaw adductor musculature: extending onto dorsal surface of parietal (0); attaching only on ventral surface of parietal (1) Meckel's canal exposure ventrally: opens medially for entire length (0); opens ventrally anterior to anterior inferior alveolar foramen (1)

For personal use only. Subdental shelf size: small or absent (0); large (1) Dorsal extension of coronoid process of dentary: absent or with only small dorsal extension (0); large, extending dorsally onto anterolateral surface of coronoid (1); or almost covering entire lateral surface of coronoid (2) Posterolateral dentary shape: no surangular or coronoid notches present (0); surangular and coronoid notches present (1); or coronoid and surangular notches reduced (2) Dentary-postdentary articulation: extensive overlap, tongue and groove articulation present (0); reduced overlap (1) Coronoid lateral process as a lappet on dentary: absent (0); present (1) Coronoid anterior extension: anterior border of coronoid curves smoothly into dentary (0); anterior border of coronoid levels out before reaching dentary, producing a long, low, horizontally oriented anterodorsal extension (1) Restriction of coronoid lateral process by dentary and surangular: coronoid lateral process present or absent, not overlapped by dentary anteriorly (0); lateral process overlapped anteriorly by dentary and restricted by surangular posteriorly, so lateral exposure of process is limited to a narrow wedge between dentary and surangular (1) Angular: present (0); absent (or fused) (1) Retroarticular process offset: no offset (0); offset medially with lateral notch forming a waist proximally (1) Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Finger-like angular process: absent (0); present (I) Adductor fossa size: small or moderate (0); expanded, inflated, widely open (1) Palatine teeth: present (0); absent (1) Pterygoid teeth: present (0); absent (1) Marginal tooth implantation: pleurodont (0); "acrodont" (1) Marginal teeth replacement: replacement tooth developing lingually, large resorption pits present ("iguanid" type) (0); replacement tooth developing posterolingually, small resorption pits present (intermediate type) (1); or replacement tooth developing posterolingually, no resorption pits present ("varanid" type) (2); or no replacement tooth and new tooth added to posterior end of tooth row (3) Basal infolding of marginal teeth: not striated (0); dentine infolded, producing striations (1) Step of offset in tooth margin of maxilla: absent (0); present (1) Vertebral condyle orientation: condyle and cotyle meeting with no or only slight obliquity; cotyle generally not entirely visible in ventral view (0); strong obliquity present; cotyle may or may not be entirely visible in ventral view (1) Wu et al. 573

Table A1 (concluded).

Character No. Description

Vertebral centrum articulation: amphicoelous (0); procoelous (1) Vertebral centrum constriction: constricted anterior to condyle (0); not constricted anterior to condyle (1) Zygosphene and zygantrum development: weakly developed or absent (0); strongly developed (1) Zygosphene and zygantrum: present (0); absent (1) Posterior trunk (thoracolumbar) intercentra: present (0); absent (1) Number of cervical vertebrae I: eight or more (0); fewer than eight (1) Number of cervical vertebrae 11: eight or fewer (0); more than eight (1) Anterior (primary) coracoid emargination: absent (0); present (1) Interclavicle: present throughout postembryonic ontogeny (0); absent in postembryonic ontogeny (1) Ectepicondylar foramen: ontogenetic enclosure of ectepicondylar groove to form a foramen (0); foramen and groove absent (1) Ventral body osteoderms: absent (0); present (1) Dorsal body osteoderms: absent (0); present (1) Cephalic osteoderms: absent (0); present (1) Dermal rugosities: absent (0); present, not vermiculate (1); or present, vermiculate (2) Epiphysis fusion: fused to diaphyses at same time or after fusion of braincase elements (0); fused to diaphyses prior to fusion of braincase elements (1) Orbitosphenoid: absent (0); present (1) Anterior braincase floor: no floor formed (0); floored by orbitosphenoid, parasphenoid cultriform process underlying orbitosphenoid (1); or floored by parasphenoid cultriform process (2) Skull solidarity: cranial elements loosely connected and palate not firmly attached to braincase floor (0); cranial elements tightly connected and palate firmly attached to braincase floor (1) Enlarge median tooth on fused premaxilla: absent (0); present (1) Position and size of optic foramina: no optic foramen formed and optic nerves coming out of brain cavity freely, or a pair of optic foramina large and located between frontals and parietals (0); a pair of optic foramina tiny and positioned entirely within orbitosphenoid (1) Size of quadrate ramus of pterygoid: long and large, loosely connecting to quadrate (0); short and small, tightly wrapping around posteromedial (ventromedial if quadrate horizontally oriented) surface of quadrate (1) Contact of pterygoid with vomer: present, palatal ramus of pterygoid meeting vomer anteriorly (0); absent (1) Lateral process of palatal ramus of pterygoid: absent (0); present, a lateral process of palatal ramus developed along lateral

For personal use only. border of palatine (1) Foramina for branches of trigeminal nerves: absent (0); one or two pairs of small foramina enclosed by prootics or by both prootics and parietals (1); or a pair of large openings enclosed by orbitosphenoid, prootics (pleurosphenoid processes), and parabasisphenoid (2) Recesses scalae tympani: present (0); closed (1) Suborbital fenestra: present or restricted but not completely closed (0); entirely closed by lateral process of palatal ramus of pterygoid (1) Dorsal portion of maxilla: extending dorsomedially (0); partially expanding dorsolaterally or bulging laterally, overhanging dental margin (1) Frontal: longer than wide (0); wider than long, along midline (1) Parietal: longer than wide (0); wider than long, along midline (1); greatly elongated, reaching at least half the length of skull (2) Postorbital: small, posteriorly tapering off, widely separate from posterior border of supratemporal fenestra (0); large, posteriorly broadened, extending posteriorly beyond posterior border of supratemporal fenestra and approaching posterolateral margin of dermal cranial roof (1) Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 Squamosal: entering supratemporal fenestra (0); excluded by postorbital - supratemporal contact or postorbital - parietal contact from supratemporal fenestra (1) Dentary tooth count: high, more than 10 dentary teeth (0); low, 10 or fewer dentary teeth (1) Double occipital condyle: absent (0); present (1) Postorbital bar: present (0); entirely absent (1) Posttemporal fenestra: present (0); closed by tight contact of parietal-squamosal complex with otoccipital complex (1); closed by sutural contact of parietal with otoccipital complex (2) Large, ventrolaterally positioned ovalis with massive stapes: absent (0); present (1) Quadrate conch: present (0); completely absent (1).

Notes: Characters 1-85 were taken from Estes et al. (1988). Of these, characters 1-24 are numerically the same as those used by Estes et al.; the others have their previous identifying numbers in parentheses. *Character has been modified in either definition or state distribution; see Appendix 3. Can. J. Earth Sci. Vol. 33, 1996

Appendix 2

Table A2. Character state distribution.

Character No. (Estes et al. 1988):

Character No. 1 2 3 4 Taxon \ (this study): 1234567890 1234567890 1234567890 1234567890 Outgroups Ancestor Sphenodontida

Ingroups Agamidae OlNONOOlOO 0000100000 1 Anguidae 0101101110 11 1 A Chamaeleontidae OlNONOOlOO OOlOllONNO 1 Cordylidae 0010001010 A Dibamidae OOlOOlNNNN IN N Gekkonidae OOlOOlNNNN OOOllOlNNO 1 1 N Gymnophthalmidae 1010001000 1111100011 1 1 11 Helodermitdae OOlOOlNNNl 1001110011 N Iguanidae 0000100100 1001000011 1 N 1 1 IN Lacertidae 0110001001 1100000010 A I 1 1 Lanthanotus OOlOOlNNNN 1001110001 For personal use only. Pygopodidae OOlOOlNNNN OOOllOlNlO A 1 A N 1 Scincidae 0010001101 1 1 NN

Teiidae

Varanus

Xantusiidae 0110?01010 OllOOlNNlO A 11 Xenosauridae 0010001100 1000000011 1 I Other Amphisbaenians OOOOOONNNN 1051000111

Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 AN NA 1 1N 11 Sineoamphisbaena 0001001100 Snakes OOOOOOONNN 1 N

Macrocephalosauridae Slavoia Globaura Eoxanta Polyglyphanodontidae

Adamisaurus 10010000?0 0010001000 10?1000010 001?100??? Notes: Characters were analysed using the heuristic algorithm of PAUP, version 3.1.1. Character-state codes: 0, plesiomorphic; 1, 2, 3, 4, below indicates (indicate) the variation of a character within the taxon. "A" below a character state indicates that the state scored is equivocal. State N was treated as state ? by the "equate" option for computer runs, as suggested by PAUP. Wu et al.

0000000 0000000

0000000

1000000

000000 1

NOOOOOO

N1 11210

00 1 1000

0000000

NO00000

0000000

NO 0 0 0 0 0

Nl 00000 NO1 1000 For personal use only.

NO 0 0 0 0 0

0000000

0000000

N000OOO

0000000

N110211 Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 1110111 NO0 1200

1000000 0 I 0 0 I1 TI 0 0 0 U D 0 '? 0 00001)"O Onooaoo

1 I?'?'???lo? 0100000

and 5, apomorphic; N, not applicable; ?, unknown or uncertain. Multiple apomorphic states of a character are not ordered. Character state (states) The taxon Ancestor is a collective of primitive lep~dosauromorphs,for which the pleslomo!-phk state of each character is scored for computer runs. Can. J. Earth Sci. Vol. 33, 1996

Appendix 3: Modification of characters from Estes et al. (1988) Most of the modifications of the data matrix result from the use of the Sphenodontida, rather than the genus Sphenodon, as an outgroup in this study. In addition, a few characters are redefined so that they are scorable in more taxa. Character 13: Sphenodon exhibits the apomorphic state for this character. However, the plesiomorphic state occurs in many primitive sphenodontidans, including Gephyrosaums (Evans 1980), Diphydontosaums (Whiteside 1986), Planocephalosaurus (Fraser 1982), and Clevosaums (Robinson 1973; Wu 1994). Thus, the plesiomorphic state of this character is scored for the Sphenodontida. Character 17: This character was thought to be equivocal in the Amphisbaenia by Estes et al. (1988). It is treated here as a nonapplicable character in Other Amphisbaenians, because the supratemporal fenestra is entirely reduced in the group and no available information can demonstrate whether or not the bone located along the posterodorsal border of the orbit in some fossil taxa of the group is the postorbital. Characfer 18: The apomorphic state of this character is restricted to the presence of the jugal-squamosal contact on the supratempord arch. The plesiornorphic, rather than the apomorphic state, is scored for the Teiidae. In contrast, the presence of the plesiomorphic state in Sphenodon is consider4 ro he a result of an apomorphic reversal within the Sphenodontida. because the jugal -squamosal contact is consistently present in dl the fossil taxa that have the character preserved (Wu 1991. 1994). Therefore, the apomorphic state of the character is scored for the Sphenodontida. Chamcwr 22: No information concerning this character within the Amphisbaenia was available to Estes et al. (1988). However, a skull of Amphisbaena alba (MCZ 54299) indicates that the plesiomorphic state of the character is present. Thus, we score this state for the taxon Other Amphisbaenians. Characrer 23(23): Downgrowths of the parietal vary in the squamates, they are well developed in snakes, the Dibamidae, and amphisbaenians. We used five apomorphic states for different conditions in these taxa. Chamcter 2404): The plesiomorphic state of this character occurs in the fossil genera of the Sphenodontida for which it can be determined (Wu 1991, 19941 and is scored for the group. Chararier 27(28]: Recent studies of phylogenetic relationships among the Sphenodontida suggest that Gephyrosaurus (Evans 1980) is the most primitive member of the group (Gauthier et al. 1988; Wu 1991, 1994). Since the lacrimal is retained in this gnus, we consider the Sphenodontida to retain the plesiomorphic state, even though it is lost in other forms. Characfcr28(29): The lacrimal is separated from the prefrontal in Gephyrosaunrs. Thus the plesiomorphic state of the character is scored for the Sphenodontida. The lacrimal is fused to the prefrontal in Sineuarnphishaena and some living amphisbaenians (Rorner 1956). although the location of the lacrimal foramen at the jugal-prefrontal suture indicates that the lacrimal wes Iost in other genera. Therefore, within the Other Amphisbaenia, both the apomorphic state and a nonapplicable state are present. We use the apomorphic state for phylogenetic analyses. Characrer 33 (35): We include both the absence or fusion (to the squarnosal) of the supratemporal as the pleriomorphic state of this character, because it is not possible to determine whether the squamosal is a single bone or includes the supratemporal in many taxa. The apomorphic state (presence of supratemporal (Kluge 1989)) is here assigned to the Sphenodontida. because For personal use only. this state is present in some fossil genera, such as CIevosaums (Robinson 1973; Fraser 1988; Wu 1991, 1994). Character 40M2): The apomorphic state of this character is the posterior closure of the opening for Jacobson's organ. Although Estes et d. (1988) discussed that the opening was cIosed by the vomer and septnmaxilla in snakes, as in Dibamus of the Dibamidae, they scored a nonappticable state for the former. The method of the closure of the opening in Sineoamphisbaem is similar to that of both snakes and Dibmus, but is different in that the maxilla does not have a medial process (present in snakes) posterior to the opening and is far apart (firmly contacts the vomer in Dibarnus) from the vorner posterior to the opening. We did not code the conditions in Dibamus. snakes, and Sineoamphishaena as three apomorphic states, but assigned the same state for all of them. Chamcrer 43(451: This character is simplified by considering the presence of an anteromedial contact between the ectopterygoid and palatine as an apornorphic state and the absence of such a contact as the plesiomorphic state. We do nor include the relationship to the suborbital fenestra in defining this character, because the latter is entirely closed in some included taxa. Estes et a!. (1988) considered the Amphisbaenia to be plesiomorphic, because the anteromedial contact of the ectopterygoid with the palatine is not universally present. In Dyriconastis rensbergeri and Sparhorhynckm, the ectopterygoid is indeed 51C. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11 separated from the palatine by a psteromedid process of the maxilla when seen in ventral view (Estes 1983, Figs. 51D). However, this separation is supeficial. The two bones contact one another on the dorsal surface of the palate in Dyliconm~isrensbergeri WCMP 76881 = V6630; the authors' personal observation). Consequently, we scored Other Amphisbaenians as being apomorphic for this character. Character 46(48): The Amphisbaenia were considered to be apomorphic in this character by Estes et al. (1988). A broad pyriform recess (the interpterygoid cavity) is formed in Sineoamphishaena, but this recess is entirely closed by the broadening of the parasphenoid cultriform process in Other Amphisbaenians (see Estes 1983. Figs. 49-52; 7agerl 1944. Figs. 1, 8- 10, 12, 14- 17). This process is very slender and points freety inlo the pyrifom recess anteriorly in other lepidosauromorphs, including many burrowing or fossorial lizards. In the Dibamidae, the parasphenoid cultsiform process is shon and broad. but does not cover the broad pyrifom recess (Rieppel 1984, Fig. I). The closure of the pyriform recess in Other Amphisbaenians is treated here at apomorphic state 2. Cl~oracser50(53): In Estes d al. (1988), this character is cited as undetermined for the Amphisbaenia. In fossil and living amphisbaenians we examined, neither of the two previously defined apomorphic states (posterior vidian opening at suture between hasisphenoid and prootic or entirely within prootic) was seen, but the plesiomorphic state (posterior opening of vidian canal within basisphenoid) is present within the group, as in Sineoamphisbaena hexatabularis. Additionally, a third apomorphic state (posterior vidian opening located between the prootic and epiphysial ossification) is noted in Amphisbaena alba (MCZ 54299, 165208) and Cadea palirostrata (MCZ 13508). Thus, the plesiomorphic state of the character is scored for Other Amphisbaenians, and apomorphic state 3 of the character is thought to have been derived within the group. Character 54(60):Estes et al. (1988) considered this character to be nonapplicable to most sphenodontidans, and scored its plesiomorphic state for Sphenodon. However, a prominent dorsal process of the dentary is present in all members of the Sphenodontida in which the condition is determinable (Wu 1991, 1994, Fig. 18). This process differs from that of the lizards in being wide and almost covering the lateral surface of the whole coronoid, except for the dorsalmost tip, rather than being narrow and only covering the anterolateral surface of the coronoid (the apomorphic state). We consider here the condition of the dorsal process of the dentary in the Sphenodontida to be representative of apomorphic state 2 of the character. Character 67(85):This character was not considered by Estes et al. (1988) to be applicable to the taxa with an acrodont dentition. We differ in considering the condition of no tooth replacement and new tooth added to the posterior end of the tooth row to be a third apomorphic state. The plesiomorphic state iguanid type and apomorphic state 3 are both present in the Sphenodontida. In Other Amphisbaenians, all three apomorphic states are present (iguanid type, intermediate type, and varanid type), although following Estes et al. (1988), apomorphic state 1 was considered to be the state for the present phylogenetic analyses. Character 84(129): The plesiomorphic state of this character was scored by Estes et al. (1988) for the Amphisbaenia, although apomorphic state 2 is present in some members of the group. We differ from Estes et al. in scoring apomorphic state 2 for Other Amphisbaenians, because the plesiomorphic state of the character is interpreted as an apomorphic reversal within the group. Apomorphic state 2 is present in all of the fossil taxa at hand. Of these taxa, Spathorhynchus species and Dyticonastis rensbergeri are more primitive than other fossil or living forms in retaining a complete orbit. Following Kluge (1989), the plesiomorphic states for characters 30, 35, and 94 were changed.

Appendix 4 Table A3. Character state distribution of 25 of the remaining 45 from the 130 osteological characters of Estes et al. (1988), which are scorable for one or more of the six fossil taxa.

Character No. 1111111 1111 2345566677 7770000111 1122 Taxon 5395956705 6890456135 6903 For personal use only. Macrocephalosauridae 1010011000 ?OO????lOO 101 1 Slavoia NOlOOllOOO 000?000100 101? Globaura 00?001100? Ill??????? ???? Eoxanla 00?001100? Ill??????? ???? Polyglyphanodontidae 10?0011000 OOOO???lOO 101? Adamisaurus 10?0011000 OOO?OOO??? ???? Notes: The character state distribution of the 45 osteological and 18 soft characters for the living taxa are referred to those of Estes et al. (1988) in their Table 2 with the plesiomorphic states of characters 65, 66, 103, and 145 being changed, as suggested by Kluge (1989). For the Sphenodontida the plesiomorphic states of characters 56, 59, 74-76, 78, and 79 were assigned on the basis of information from fossil taxa. Numbers are equivalent to those used by Estes et al. (1988). Symbols are defined as in Appendix 2. Can. J. Earth Sci. Downloaded from www.nrcresearchpress.com by 129.107.48.242 on 04/20/11