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Journal of Paleontology 23(4):971±976, December 2003 ᭧ 2003 by the Society of Vertebrate Paleontology

NOTE

THE BASICRANIAL MORPHOLOGY OF MADTSOIID (, ) AND THE EARLIEST (SERPENTES)

JOHN D. SCANLON*, School of Biological Sciences, University of New South Wales, UNSW Sydney 2052,

Snakes of the extinct Madtsoiidae are known from early Late ica Woodward, 1901 (?Coniacian, Late ; Estes et al., 1970; Cretaceous to deposits in Madagascar, western and northern Caldwell and Albino, 2001), which has been interpreted as a basal al- , southwestern Europe (Spain and possibly France), and South ethinophidian or a pre-alethinophidian of similar grade to madt- America (reviewed by Rage, 1998; Rage and Werner, 1999). Two gen- soiids (reviewed by Scanlon and Lee, 2000). I also make some com- era occur in both the Campanian or Maastrichtian of Argentina and the parisons with a putative madtsoiid braincase fragment from the Ceno- early Eocene of Australia (Patagoniophis and Alamitophis, Albino, manian of Wadi Abu Hashim, Sudan (Rage and Werner, 1999), and 1986; Scanlon, 1993; see Boles, 1999, for recent discussion and con- comment on its signi®cance. ®rmation of the Eocene date), and Australia is the only region in which Comparisons with recent taxa are based on collections of the Queens- madtsoiids are known later than the Eocene. naracoortensis land Museum, Australian Museum, Macleay Museum, South Australian Smith, 1976, occurs in and deposits (Scanlon and Museum, M. Archer, D. J. Barrie, and the author (details available on Lee, 2000), and large of Scanlon, 1992, also range request). from late to late Pleistocene (Mackness and Scanlon, 1999). Riversleigh are prepared using acetic acid (e.g., Archer et al., The highest known diversity and some of the best-preserved material 1991) and the specimen described here is completely free of carbonate of madtsoiids are from the late Oligocene and of Riversleigh, matrix. The course of canals and foramina was determined visually northwestern Queensland, including Wonambi barriei, one or more un- under a binocular microscope, using a hair as a probe. named species of Yurlunggur, two small species of Nanowana, and at Terminology for cranial either follows that in Rieppel's least one additional new taxon (Scanlon, 1996, 1997; Scanlon and Lee, (1979) review of snake basicranial evolution, or Rieppel's terms are 2000). noted parenthetically when different ones are preferred. Cranial remains of Wonambi naracoortensis from Naracoorte, South Institutional Abbreviations QM F, Queensland Museum (Pa- Australia (Barrie, 1990; Scanlon and Lee, 2000), provide the best evi- laeontology), Brisbane. dence of the morphology and af®nities of any madtsoiid (though the family as currently recognized may not be monophyletic; see below). SYSTEMATIC PALEONTOLOGY These specimens were originally interpreted as supporting the inclusion of Madtsoiidae in Alethinophidia (Barrie, 1990; Scanlon, 1992), but REPTILIA reinterpretation of the morphology and more comprehensive phyloge- SQUAMATA netic analyses placed this lineage outside a including all living OPHIDIA snakes, including scolecophidians as well as alethinophidians (Scanlon, YURLUNGGUR Scanlon, 1992 1996; Scanlon and Lee, 2000; Lee and Scanlon, 2002). These results YURLUNGGUR sp. con®rm the interpretations of Hoffstetter (1961:155) and McDowell Material (1987) regarding the primitive features of madtsoiid vertebrae relative QM F23041. to those of all living snakes, and con¯ict with the widespread assump- Locality Mike's Menagerie Site (Mike's Menagerie Local Fauna), tions that scolecophidians are basal snakes and that all known Godthelp Hill, Riversleigh World Heritage Fossil Property, northwestern snakes are either scolecophidians or alethinophidians (e.g., Underwood, Queensland. 1967; Rage, 1984, 1987; Rieppel, 1988; Zaher and Rieppel, 1999; Age The deposit forms part of `Tertiary System B,' interpreted to Tchernov et al., 2000). be late Oligocene or early Miocene in age (Archer et al., 1989, 1997). Part of the braincase of a second Australian madtsoiid, similar to that Description A fragment 22.0 mm in length comprises most of the of Wonambi but differing conspicuously in proportions, has been rec- co-ossi®ed basisphenoid and parasphenoid (Fig. 1), here referred to as ognized from a late Oligocene or early Miocene deposit at Riversleigh, `sphenoid' for brevity; the width of the cultriform process immediately northwestern Queensland. This deposit contains vertebrae, , and anterior to the basipterygoid processes is 7.3 mm; the same, immedi- elements representing several taxa of madtsoiids including Nanowana ately anterior to ossi®ed portions of trabeculae is 5.0 mm; the maximum godthelpi, N. schrenki, and Wonambi barriei (Scanlon, 1996, 1997; width across the basipterygoid processes is 10.7 mm; the length of the Scanlon and Lee, 2000). However, the only vertebrae consistent in size canal for the abducens nerve is 6.4 mm; the length of the articulatory with the braincase fragment are similar to those of Yurlunggur cam- surface of the basipterygoid process (right) is 7.5 mm; the length of the ®eldensis Scanlon, 1992, allowing the braincase fragment to be referred vidian canal is greater than 6.6 mm. to the same (Scanlon, 1996). All Yurlunggur vertebrae known The dorsal surface (Fig. 1A) bears an oval, bowl-like hypophysial pit from Riversleigh have relatively higher neural spines than the somewhat (sella turcica) centered just anterior to a line joining the posterior ends later Y. cam®eldensis, so are considered speci®cally distinct, but taxo- of the basipterygoid processes. It is not recessed below the posterior nomic treatment of vertebrae is deferred pending study of recently dis- dorsum sellae (crista sellaris); the posterior and lateral walls are nearly covered articulated remains. vertical, while the anterior wall is more oblique but demarcated ante- As well as Wonambi, comparisons are made with extant snakes of riorly by a shallowly overhanging crest approximately 2 mm across. some basal lineages (anilioids and booids) and with patagon- This crest is interrupted by three small troughs probably accommodating vessels (one to the left of the midline, two smaller ones to the right). A similar pattern of three anterior troughs is seen in Calabaria reinhardti, and a slightly less similar condition in unicolor * Present address: Department of Environmental , Univer- and bicolor (Rieppel, 1979:®gs. 5, 7), where they represent sity of Adelaide, and Department of Palaeontology, South Australian the anterior course of the ramus cranialis of the cerebral carotid. Museum North Terrace, Adelaide SA 5000, Australia, e-mail: scanlon. In the midline within the hypophysial pit, 0.7 mm posterior to the [email protected] transverse anterior crest, is a small foramen opening posteriorly, re-

971 972 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 23, NO. 4, 2003

FIGURE 1. Sphenoid fragment referred to Yurlunggur sp. (QM F23041), in (A) dorsal, (B) schematic dorsal, (C) ventral, (D) right lateral (slightly ventral), and (E) anterior views. Abbreviations: a.opht., trough probably for ophthalmic artery; alar pr., alar process; ao.vc., anterior opening of vidian canal; ao.VI, anterior (extracranial) opening for abducens nerve; bpt.pr., basipterygoid process; ?cid, foramina possibly for branches of trigeminal (V4) innervating constrictor internus dorsalis musculature; cr.ven., crista ventrolateralis of basisphenoid; dor.sel., dorsum sellae; f., unidenti®ed foramen; f.c.cer., cerebral carotid foramen; h.f., hypophysial foramen; po.vc., posterior opening of vidian canal; po.VI, posterior (intracranial) opening for abducens nerve; r.cr., troughs for ramus cranialis of cerebral carotid artery; sag.keel, sagittal keel of sphenoid; s.t., sella turcica (hypophysial pit); trab., trabecula cranii; vc., vidian canal; VI, canal for abducens nerve. bar equals 10 mm.

garded as the hypophysial foramen (reported as `cerebral foramen' in while a more anterolateral (but still intracranial) position is usual in W. naracoortensis; Barrie, 1990). snakes. While it is intersected by some narrower passages which may A large cerebral carotid foramen opens into each side of the hypo- have conveyed smaller nerves or vessels (see below), the canal and physial pit, just posterior to its midpoint, from the medial branch of the anterior opening are here considered as primarily for the abducens vidian canal. The bifurcation of the canal is exposed by breakage on nerve. On the left side the bone has broken along the canal and it is the left and is visible through its posterior opening on the right (shown preserved only as a short trough facing dorsolaterally, directly above, schematically in Fig. 1B), the medial branch being somewhat smaller but at a slight angle to, the vidian canal. than the main anterior branch. The bone is incompletely fused dorsal to the abducens canal, leaving The posterior wall of the pit is pierced by three small foramina, one a T-shaped hairline suture connecting the dorsal margins of both open- just to the right of the midline and two smaller ones farther to the left. ings (Fig. 1A); a similar feature has been illustrated in and These communicate with a cavity within the dorsum sellae, exposed (Rieppel, 1979:®g. 4). Two smaller foramina lie on this posteriorly by breakage. Their identity is unknown, unless they indicate suture lateral to the hypophysial pit (only the anterior one of the pair an extracranial course of the basilar artery as in (cf. Russell, is preserved on the left side, and it is smaller than the corresponding 1967). one on the right). The narrow canal from the more posterior foramen Posterolateral to the hypophysial pit on the right side, near the broken intersects the abducens canal and exits the braincase laterally above the posterior edge, is a large foramen, opening posterolaterally, which com- rear of the basipterygoid process. The more anterior bifurcates imme- municates by a long canal with a similar-sized foramen just postero- diately within the bone, sending an anterior branch (preserved on both dorsal to the anterior opening of the vidian canal. The position of the sides) ventrolaterally to join the vidian canal, and a posterior branch posterior opening is typical for n. abducens (VI) (e.g., Rieppel, 1979; (complete on the right side) to the abducens canal. This anterolateral Bellairs and Kamal, 1981). In most squamates the abducens nerve tra- pair occupies the same position relative to the hypophysial pit as do the verses a very short tunnel through the dorsum sellae and the anterior internal carotid foramina of anilioids (cf. Rieppel, 1979), though such opening is on the anterior-facing wall lateral to the hypophysial pit, a role seems unlikely in this case as their connections with the vidian NOTES 973 canal are less direct. Each branch apparently rami®es further within the not smooth facets of dense bone as in the corresponding structures of bone, resulting in four groups of smaller foramina on the external sur- booid snakes. The articulating surfaces are roughly triangular; the con- face; these are mostly too small to probe successfully, so that only three vex apical part of the facet is demarcated by a longitudinal groove and external openings can be identi®ed con®dently (?cid in Fig. 1C, D). It a notch in the anterodorsal edge, and is continuous with a crest extend- seems likely that some or all of these foramina provide egress for ing posterodorsally (lateral margin of the sphenoid unit) which, at least branches of the cid-nerve (V4 levator bulbi, innervating the constrictor posteriorly, was in sutural contact with the prootic. internus dorsalis musculature), but no detailed similarity to this arrange- Comments The Yurlunggur fragment has been compared with a ment has been found in other taxa. A similar-sized canal enters the slightly more complete sphenoid of Wonambi naracoortensis that is dorsum sellae in a medioventral direction from the posterior opening associated with other braincase and jaw elements (Barrie, 1990; Scanlon for nerve VI; this is truncated by breakage, and its identity is unclear. and Lee, 2000). The two madtsoiids are similar in most respects, but Immediately lateral to the posterior opening of the abducens canal the present specimen provides additional information as most of the and dorsal to the posterior opening of the vidian canal, i.e., at the lateral canals within the bone have not been observed directly in Wonambi. edge of the dorsum sellae, is an angular dorsal prominence of the sphe- Other phylogenetically relevant comparisons are with Dinilysia (see noid element (somewhat worn), which corresponds topographically to above) and extant snakes such as anilioids and booids; also relevant are the alar process of (Oelrich, 1956; Russell, 1967; Bellairs and the likely nearest outgroups to snakes, represented by terrestrial vara- Kamal, 1981; ϭ `clinoid process' in Rieppel and Zaher, 2000). The noid lizards and mosasauroids (Lee, 1998; Caldwell, 1999; Rieppel and posterior face of this prominence has several low transverse corruga- Zaher, 2000). Some information from the present specimen has already tions, and a compact appearance (in contrast to the rest of the element been incorporated in phylogenetic analyses (Scanlon and Lee, 2000; which appears more chalky) suggesting endochondral bone. Lee and Scanlon, 2002). The vidian canal opens anteriorly above the center of the basiptery- As in many other snakes the dorsum sellae of madtsoiids is low and goid process on each side, and the similar-sized abducens canal just saddle-shaped, not overhanging anteriorly, and there are no retractor posterodorsal to it; however, the processes are located asymmetrically, pits or a median crest within the hypophysial pit. The abducens canal about 1 mm more anterior on the left than right, so that the foramina emerges anterolateral to the hypophysial pit rather than within it; the are also asymmetrical in position. Distortion is absent, as in most Riv- basisphenoid rostrum is broad and well ossi®ed between the trabeculae, ersleigh fossils, so the asymmetry was present in life, but it is not known which remain separate and parallel into the orbital region of the . whether this represents individual or taxic variation. The original pos- These are differences from typical lizards such as Varanus and (in most terior opening of the vidian canal is not preserved on either side, but cases) from mosasaurs (e.g., Rieppel and Zaher, 2000). on the more complete right side the canal is exposed by breakage about The vidian canals give off an interior branch for the cerebral carotid 4 mm posterior to the basipterygoid process, which may have been very that emerges in the posterolateral wall of the hypophysial pit, and the close to its natural position (Fig. 1D). main anterior opening lies on the anterodorsal face of the basipterygoid The anterior part of the fragment is bounded laterally by the vertically process, entirely within the sphenoid complex, as in Dinilysia and liz- oval, cylindrical trabeculae cranii (cristae trabeculares); these are seen ards. There is thus no secondary anterior opening on the sphenoid- in anterior view (Fig. 1E) to be ossi®ed separately from the broad plate parietal boundary as seen in anilioids and most other alethinophidian joining them (basisphenoidal rostrum), which is the same depth as the snakes (Underwood, 1967; Estes et al., 1970; Rieppel, 1979). trabeculae laterally, gently concave dorsally, and bears a low midventral Immediately above and behind the anterior vidian foramen is the ridge. The cristae trabeculares must have formed the dorsal surfaces for similar-sized anterior opening of the abducens canal. The anterior ab- contact with the lower edge of the parietal, but (as in Wonambi)donot ducens foramen thus occupies a similar (extracranial) position, relative show any distinctly bounded facet-like structures, implying an abutting to the vidian canal and basipterygoid process, as in typical lizards (Riep- or weakly clasping (syndesmotic) contact rather than a suture. There pel, 1979) and mosasauroids (Russell, 1967). Its position in extant are only irregular and asymmetrical traces of longitudinal grooves on snakes is lateral or anterolateral to the hypophysial pit, which results the dorsal surface just medial to the cristae (Fig. 1A), whereas Wonambi from two likely apomorphies of snakes: greater length of the canal, and has more distinct grooves here, possibly for the ophthalmic arteries the formation of a distinct anterolateral margin of the hypophysial pit (Barrie, 1990). The anterior ends of the ossi®ed trabeculae, level with (weakly or not de®ned in lizards); these are also present in the madt- each other, have concave surfaces whence they extended forward as soiids. However, the anterior abducens foramen in modern snakes also cartilaginous rods (indicating a platytrabic condition as in Dinilysia and differs from that in the madtsoiids in being intracranial, i.e., medial to alethinophidians). the secondary braincase wall (parietal-sphenoid contact). Three small foramina on the ventral surface, close to the midline A large foramen in the extracranial, `supra-vidian' position was re- between the anterior ends of the basipterygoid processes (Fig. 1C) ap- ported in Dinilysia patagonica by Estes et al. (1970), but not identi®ed. pear to be multiple openings of the hypophysial foramen, but they are Rieppel (1979) and McDowell (1987) interpreted it as the exit of the too narrow (especially dorsoventrally) to demonstrate this directly by cid-nerve (ϭV4 levator bulbi) from the cavum epiptericum, but separate probing. As in Wonambi, clearly bounded concave surfaces (presumably channels, likely to be for the cid-nerve, are present in Yurlunggur (see for muscle origin) are present on the posterior part of the sphenoid, above). Estes et al. (1970:®g. 5) partially excavated the vidian canal separated posteriorly by a median keel that broadens gradually between and the canal dorsal to it in Dinilysia, and though they did not expose the basipterygoid processes, and extending to a line between the anterior the intracranial opening, they show the posterior part of the upper canal tips of the processes. However, the posterior keel is sharp-edged rather extending to a position dorsomedial to the posterior vidian canal open- than thickened ventrally as in Wonambi, and also less prominent. Such ing. This is precisely the same situation as in Yurlunggur (Fig. 1B) and a mid-ventral keel (extending onto the basioccipital) is not present in as inferred in Wonambi.InDinilysia there is also a small branch joining Dinilysia or lizards, and may be present or absent in alethinophidians. or intersecting both of the two longitudinal canals posterior to the bas- When present in extant snakes, the median keel separates the areas of ipterygoid process, which is similar if not identical to the (tentatively origin of the mm. protractor pterygoidei, whereas in lizards these mus- identi®ed) cid-nerve canal in Yurlunggur. The similarity of position of cles do not extend farther medially than the basipterygoid process. The the abducens openings in the madtsoiid and lizards, and the similarity crest extending posteriorly from the basipterygoid process in Yurlung- of these canals and their anterior openings in Yurlunggur and Dinilysia, gur (crista ventrolateralis; Oelrich, 1956) is also sharper than the equiv- indicate that the `unknown foramen' of Dinilysia patagonica is also for alent structure in Wonambi. The similarly concave surface lateral to this the abducens nerve. crest (posterior and partly dorsal to the basipterygoid process) is un- It might be signi®cant that the Platecarpus also has a large likely to provide the origin of an entirely different muscle since the m. foramen immediately above and behind the anterior vidian canal open- levator pterygoidei in snakes typically originates more dorsolaterally, ing, the function of which is also uncertain (exit for basilar artery ac- on the parietal; the division by a longitudinal crest might indicate a cording to Russell, 1967; `dorsal anterior opening of Vidian canal' in division of the protractor pterygoidei into separate medial and lateral Rieppel and Zaher, 2000:499 and ®g. 2C). An intracranial anterior open- heads, as in some extant snakes, but it is the lateral one that would ing for nerve VI is also reported in Platecarpus by Rieppel and Zaher resemble that of lizards such as Varanus. (2000:®g. 4), but it is not clear from their descriptions whether the The basipterygoid processes, slightly asymmetric in position as noted identities of these foramina have been assumed, or actually demonstrat- above, are elongated almost parallel to the midline and face ventrolat- ed by tracing internal canals. erally and slightly anteriorly. Their distal surfaces are convex and Rieppel (1979) regards the anilioid and primitive booid condition of bumpy, like the cartilage-invested basipterygoid processes of lizards, an intracranial primary anterior opening of the vidian canal to be prim- 974 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 23, NO. 4, 2003 itive for snakes as a whole, and contrasts this with the condition in interpret the corrugated areas as basipterygoid `facets' (functionally at Dinilysia and advanced booids (some members of both and least), and their sessile (i.e., non-pedicellate) nature suggests the sphe- Pythoninae) in which the primary opening is extracranial, as in lizards. noid-pterygoid attachment may have been formed by short ligaments Rieppel suggests (1979:427) that ``. . . elongation of the braincase rel- as reported in anilioids or bolyeriids, in contrast to the discrete sliding ative to the facial region of the skull together with the enclosure of the or hinge joints formed by the prominent, pedicellate processes in the brain within frontal and parietal downgrowths in snakes makes complex madtsoiids or booids (which in these respects resemble Dinilysia and changes necessary before the lacertilian of Vidian canal was re- lizards). established,'' and that the condition in Dinilysia was derived in parallel The formation of a lateral wing, apparently by the upturned ventro- to that of advanced booids. This comparison depends partly on Riep- lateral part of the sphenoid (i.e., basipterygoid process) meeting the pel's interpretation of the `unidenti®ed foramen' of Dinilysia (Estes et parietal lateral to the vidian canal, has long been regarded as a signif- al., 1970) as an exit for the cid-nerve. icant and reliable alethinophidian synapomorphy (Underwood, 1967; But if, as argued here, this foramen in Dinilysia is the opening of the McDowell, 1967, 1974, 1987; Rieppel, 1979, 1988), and this view is abducens canal as in Yurlunggur sp., the Dinilysia condition is distinct supported by several recent analyses (Scanlon, 1996; Scanlon and Lee, from that in derived booids and similar in both respects to that of lizards 2000; Lee and Scanlon, 2002). Hence, Vb-690 can be referred to Ale- (where the anterior abducens opening is almost directly dorsal to that thinophidia based on its possession of the derived condition. By the of the vidian canal, albeit `intracranial'). Following this interpretation, same criterion, the Australian madtsoiids are not alethinophidians the enclosure of the brain by the parietal in primitive snakes took place (Scanlon and Lee, 2000). medial to the anterior openings of both the vidian and abducens canals. The snake fauna of Wadi Abu Hashim is diverse, including at least This does not affect the polarity for changes within Alethinophidia nine species and at least seven families (Werner and Rage, 1994; Rage (Rieppel's conclusion is supported by the distribution of character states and Werner, 1999). All of these families have been referred to Alethin- among extant forms; see also Underwood, 1967:15±18), but implies that ophidia in widely accepted classi®cations (e.g., Rage, 1987), and some the state seen in anilioids and basal booids originated subsequent to the even to the highly advanced clade , previously unknown enclosure of the brain, and after the origin of lineages leading to Din- before the Eocene (Rage and Werner, 1999). Together with phylogenetic ilysia and madtsoiids. The phylogenetic position of Dinilysia (and analyses (Cundall et al., 1993; Scanlon and Lee, 2000; Tchernov et al., where included, madtsoiids) as basal to Alethinophidia has been sup- 2000; Lee and Scanlon, 2002), these identi®cations have the surprising ported by almost all analyses (reviewed in Scanlon and Lee, 2000). implication that nearly all of the major (`superfamily' level) lineages of A sphenoid fragment of a snake from the of Sudan modern snakes would have originated by the Cenomanian (Rage and (Rage and Werner, 1999) was considered comparable in some respects Werner, 1999). However, while the of fossil snakes neces- to Wonambi and hence possibly referable to the madtsoiid (indetermi- sarily depends mainly on vertebrae, these present a very restricted set nate genus and species) represented by vertebrae in the same deposit, of phylogenetically informative features compared to certain bones of although a number of other snake taxa were also present. Some com- the skull. Hence the proposed relationships of most of the extinct fam- parisons are therefore made here between Australian madtsoiids and the ilies, presently known only from vertebrae, stand in need of testing by much older African specimen (Technical University of BerlinÐSpecial discovery and analysis of associated cranial remains. Research Project 69, Vb-690) based on the published illustrations (Rage Rage and Werner (1999) remained uncertain as to the af®nities of the and Werner, 1999:®g. 22). only snake cranial element recognized from Wadi Abu Hashim, con- Yurlunggur, Wonambi and Vb-690 are similar in having a well-de- cluding from its relatively large size compared to most of the vertebral ®ned, ellipsoidal hypophysial pit (circular in Vb-690) pierced by pos- remains that ``Vb-690 may belong to the Madtsoiidae, to a lapparen- terolateral carotid foramina (their connection with the vidian canals not tophiid-grade family, or to a still unknown family'' (Rage and Werner, con®rmed in Vb-690, but hardly to be doubted) and an anterior, median 1999:107). If it is accepted that Madtsoiidae as presently de®ned are hypophysial foramen that emerges on the ventral midline somewhat monophyletic, Vb-690 can now be excluded by possession of a `de®n- anterior to the internal foramen. There is a sagittal ventral keel that itive' alethinophidian character that is absent in both madtsoiids where divides anteriorly below the hypophysial pit, enclosing a ¯at triangular it can be evaluated. The same apomorphy would also be unexpected in space within which the hypophysial foramen emerges. The foramen a lapparentophiid-grade snake, as Lapparentophis and similar forms interpreted as the anterior opening of the abducens canal also lies di- (known only from vertebrae) have always been considered to occupy rectly behind and above the anterior vidian canal opening, in a common an even more basal phylogenetic position (Hoffstetter, 1959; Rage, concavity or trough. Each of these shared features is matched in some 1984, 1987; McDowell, 1987; Rage and Werner, 1999). However, there extant snakes, but in combination they appear to distinguish these three is an additional possibility that seems at least as plausible as the pres- from all other snakes and indeed all squamates (cf. Rieppel, 1979; Rage ence of an additional large snake taxon in the fauna, none of whose and Werner, 1999). However, there are also a number of differences. vertebrae have yet been found: Vb-690 may indeed belong to the same For instance, the dorsum sellae is less prominent in Vb-690; the pos- taxon as the `madtsoiid' vertebrae, if their combination of vertebral terior openings of the abducens canals relatively smaller and closer to features actually characterises a paraphyletic stem-group to Alethino- the hypophysial pit; the posterior openings of the vidian canals farther phidia, rather than a clade. Support for of all madtsoiids is anterior and more distant from the borders with the prootics; and the weak (a single apomorphy, presence of parazygantral foramina and fos- element strongly `arched' in the sagittal dimension rather than conspic- sae; e.g., Rage, 1998), they encompass considerable diversity in other uously ¯at as in the Australian forms. These proportional and shape aspects of vertebral form, and indeed the possibility of has differences might be explained as correlates of size difference (Vb-690 been suggested before (Scanlon, 1996; M. K. Hecht, pers. comm.). is roughly half as large as the Yurlunggur specimen) or indicating a It can at least be inferred that the Cenomanian snake represented by low level of phylogenetic divergence, but others seem more signi®cant. Vb-690 was more closely related to extant alethinophidians than to Yur- I disagree with Rage and Werner's interpretation (1999:106±107) that lunggur or Wonambi, thus providing a good minimum date for the di- neither a lateral wing nor basipterygoid processes are present in Vb- vergence of these Australian madtsoiids from all extant alethinophidian 690. In fact the specimen shows the typically alethinophidian condition lineages. Con®rmation of alethinophidian skull characters adds support (McDowell, 1967, 1987; Rieppel, 1979) of an upturned lateral wing to Rage and Werner's (1999) interpretation that at least some of the projecting between the prootic and parietal, directly lateral to the hy- vertebrae from the same site represent alethinophidian families. How- pophysial pit, with the anterior opening of the vidian canal (in a channel ever, it remains to be seen how many, and which, of the Cenomanian on the dorsal surface of the wing) medial to the parietal contact and taxa will ®nd a permanent place within Alethinophidia. thus intracranial. This lateral wing has both a thickened dorsolateral Acknowledgments I thank Olivier Rieppel, Jean-Claude Rage, Da- edge, interpreted as contacting the parietal (with no counterpart in the vid Cundall, Mike Caldwell, Mike Archer, Max Hecht, Martin Sander, Australian material, at least not lateral to the vidian canal), and a dis- Paul Willis, and Mike Lee for valuable comments on earlier drafts and/ tinctly bounded, `corrugated' ventral surface corresponding in position or related manuscripts. This research was commenced with support from to the basipterygoid facet of the madtsoiids. The corrugated areas are the Australian Commonwealth Postgraduate Awards scheme, and com- interpreted by Rage and Werner as muscle attachment areas for m. pro- pleted with support from the Australian Research Council through tractor pterygoidei; however, in extant snakes with a sagittal keel on grants to M. Lee. the posterior sphenoid, this muscle reaches the keel and extends ante- The Riversleigh project has been supported ®nancially by the Aus- riorly to just behind or between the basipterygoid articulations (e.g., tralian Research Council (Grant PG A3 851506P); the University of , Frazzetta, 1966; Casarea, Cundall and Irish, 1989). Thus, I New South Wales; the National Estate Grants Scheme (Queensland); NOTES 975 the Riversleigh Society Inc.; the Queensland National Parks and Wild- omons, with special reference to those in the Bernice P. Bishop life Service; Century Zinc Pty Ltd; Pasminco Pty Ltd; Earthwatch Aus- Museum, Part I. . Journal of 8:1±57. tralia; ICI Australia Pty Ltd; the Australian Geographic Society; the ÐÐÐ 1987. Systematics; pp. 1±50 in R. A. Seigel, J. T. C. Collins, Queensland Museum; the Australian Museum; the Royal Zoological and S. S. Novak (eds.), Snakes: Ecology and Evolutionary Biology. 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(2000:®g. 2g) is from a different locality and age (pp. 813, 824); how- sphenoid (usually considered to be homologues of the basipter- ever, it was collected by John Barrie from the same deposit as the rest ygoid processes; McDowell, 1967) extending dorsolaterally to form su- of P30178. Rieppel et al. (2002) also consistently misspell the speci®c tural contacts with the parietal and prootic, thus producing a triangular epithet of Wonambi barriei as `barrei.' dorsal prominence between the latter elements in lateral view. In Won- Rieppel et al. also give a number of interpretations of Wonambi na- ambi (as in Dinilysia and Yurlunggur) the corresponding parts of the raacoortensis differing from those in Scanlon and Lee (2000) and this sphenoid are indeed present, but they form basipterygoid processes pro- work. Their statement (p. 816, and their character 18) that ``the anterior jecting ventrolaterally, are entirely free of the prootic and parietal, and opening of the Vidian canal is bipartite in Wonambi'' is rendered un- the external dorsolateral margin of the basisphenoid is straight. Rieppel likely by the observations on Yurlunggur in this paper. Their coding of et al. code Wonambi with a different state from Dinilysia (character 21 a laterosphenoid as persent (their character 28) in Wonambi is based on in appendix 3, p. 828), but their suggestion of the `best way' to evaluate the idea that its absence is due to damage (p. 819). Most relevant to this character is not applicable to Dinilysia, where no disarticulated the present paper, they also state (2002:817) that `[t]he ``lateral wings'' basisphenoid has been described. of the basisphenoid are present in Wonambi . . . Comparing the disar- ticulated basisphenoid of (Rieppel, 1979b:®g. 3) with that of LITERATURE CITED alethinophidians (Rieppel, 1979a) and with Wonambi is the best way to ascertain the presence of ``lateral wings'' of the basisphenoid in the Rieppel, O., A. G. Kluge, and H. Zaher. 2002. Testing the phylogenetic latter genus.' As used in the present paper, the alethinophidian character relationships of the Pleistocene snake Wonambi naracoortensis ``presence of lateral wings'' involves the lateral margins of the basi- Smith. Journal of Vertebrate Paleontology 22:812±829.