Molnar et al, 2002

Journal of Vertebrate Paleontology 22(3):612–628, September 2002 q 2002 by the Society of Vertebrate Paleontology

AN EXTINCT PLEISTOCENE ENDEMIC MEKOSUCHINE CROCODYLIAN FROM FIJI R. E. MOLNAR1, T. WORTHY2, and P. M. A. WILLIS3 Museum of Northern Arizona, 3101 N. Fort Valley Road, Flagstaff, Arizona 86001 U.S.A., barbmoln@hotmail.com; 2 Palaeofaunal Surveys, 2A Willow Park Drive, Masterton, New Zealand, twmoa@wise.net.nz; 3 Quinkana Pty Ltd, 6/18 Francis St, Bondi, New South Wales 2026 Australia, pwillis@ozemail.com.au

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ABSTRACT—Isolated cranial and postcranial elements represent a new genus and species of endemic crocodilian, Volia athollandersoni, from presumed Pleistocene cave deposits of Fiji. Preliminary phylogenetic assessment indicates that it is a mekosuchine crocodylid. This material sheds further light on the Pleistocene tetrapod fauna of the southwestern Pacific islands.

INTRODUCTION Recent paleontological exploration of caves on Viti Levu, Fiji, has revealed a number of prehistorically extinct taxa (Worthy et al., 1999). Among these is an endemic, probably terrestrial, crocodylian, reported in two popular articles (Anderson, 1999; Anon., 1999). This material indicates that the mekosuchine radiation of crocodylids (Salisbury and Willis, 1996) was not restricted to the Australian mainland and New Caledonia.

Isolated ziphodont crocodylian teeth from Papua New Guinea (Plane, 1967) plausibly pertain to a mekosuchine, but this has yet to be established.

The Fijian archipelago (320 islands, 18,270 km2) is the largest landmass in the central Pacific (Pernetta and Watling, 1979).

It would have been considerably larger when sea level was more than 100 m lower during Pleistocene glaciations and Viti Levu linked to Vanua Levu (Watling, 1982). Viti Levu is the oldest island in the archipelago with rocks of the Yavuna Group of Late Eocene to Early Oligocene age (Rodda, 1994). Although there may have been land associated with these older rocks, emergent land was certainly present during the deposition of the Wainimala Group (Late Oligocene-Middle Miocene), and probably has been continuously present since about 16 million years ago (Chase, 1971; Rodda, 1994). Fiji is therefore older than any other Pacific oceanic landmass except New Zealand or New Caledonia.

The modern vertebrate fauna of Fiji is characterised by a lack of terrestrial mammals as are other Pacific islands. Birds dominate the fauna but there is also a diverse herpetofauna of frogs (2 spp.), iguanas (2 spp.), geckos (10 spp.; 4 presumed to be introduced by people prehistorically), skinks (12 spp.), and snakes (2 spp.) (Pernetta and Watling, 1978; Zug, 1991; Zug and Ineich, 1995). Indigenous mammals are restricted to six species of bats (Flannery, 1995). This fauna contains several endemic species that have no equivalents on truly oceanic islands—the islands of the Solomon and Philippine groups are continental shelf islands. Notable among these species are the two Platymantis frogs which are terrestrial, salt-intolerant taxa for which over-water dispersal seems unlikely. Their nearest relatives are in the Solomon Islands (Gorham, 1965; Gibbons, 1985). The iguanas (Brachylophus vitiensis, B. fasciatus)—although one is shared with Tonga—have no close relatives elsewhere and one snake, Ogmodon vitianus, is an endemic monotypic genus, although the boid Candoia bibroni is more widespread (Gibbons, 1985).

The Fijian archipelago historically had 69 indigenous breeding land birds (Watling, 1982). Due to allopatric speciation in many genera, and effects of island area, any one island has far

fewer than this total. Viti Levu has the most with 47, of which two are now extinct. While 56% of the historically known land birds are endemic (Watling, 1982), few are distinctive, and none are aberrant, which is unusual in avifaunas from older islands.

Even more unusual for an oceanic island is the fact that few species are known to have become extinct historically. Only the barred-wing rail Nesoclopeus poecilopterus and the whistling duck Dendrocygna arcuata became extinct in the late nineteenth century (Watling, 1982).

A number of prehistorically extinct taxa (Worthy et al., 1999) have been found in caves on Viti Levu, in addition to the crocodylian. Among birds, these include Megavitiornis altirostris a giant and highly modified megapode and Megapodius amissus, a Fijian form of this widespread genus of smaller megapode (Worthy, 2000). Other extinct birds include a giant flightless pigeon and a large volant pigeon (Ducula sp.), a large rail and a snipe (Coenocorypha sp.). Of considerable interest, the fauna also contained extinct herpetofaunal elements—a giant frog (Platymantis sp.), a giant iguana, and the crocodylian.

The second author searched limestone areas in various places in Viti Levu for caves and possible fossil deposits between June 1997 and October 1998 as detailed in Worthy and Anderson (1999). Two fossil sites on Viti Levu contained crocodilian fossils, Voli Voli and Wainibuku Caves (Fig. 1). In Voli Voli Cave, near the mouth of the Sigatoka River, the significant VV1 site is located about 50 m in from its submergence (where its waters flow under the ground). There, fossils were found in consolidated lateritic clay, which forms part of a once more extensive cave infill. Fossils were fragmented and the bones lack an organic fraction for radiocarbon dating, and no overlying speleothems useable for dating were present. The remnant nature of the deposit and the consolidation of the sediment, with internal slickensides, suggest that this deposit is of Pleistocene age.

Overlying this site on the surface is a doline, which has a rockshelter from which a shaft drops into the roof at VV1. Preliminary optically stimulated luminescent dates from Voli Voli Cave indicate an age of 10,000–20,000 years ago for the fossiliferous clay (Anderson et al., 2001). Although there have been difficulties resulting from the uncritical use of this technique (e.g., Gibbons, 1998), with proper care reliable dates can be obtained (Roberts and Jones, 1994; Roberts et al., 1998).

Further details are available in Anderson et al. (2001).

A few kilometers from Suva, Wainibuku Cave lies in the headwaters of Wainibuku Stream in the Wainibuku Valley (Gilbert, 1984). A small deposit of unknown age was found in potholes in the floor of a passage now abandoned by the stream that formed it (Worthy and Anderson, 1999). Although heavily

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FIGURE 1.

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The two fossil sites on Viti Levu, Fiji, yielding crocodilian fossils.

mineralized by having been buried in anaerobic clays below bat guano, the fossils are not necessarily very old as they were only 2–3 m above present stream level. The fossils are thought to have derived from a passage now blocked by flowstone, that presumably took about 3,000–4,000 years to form. The very small deposit was exhaustively worked and provided well-preserved material of the crocodylian. The fossil assemblage appears to be primarily the result of pitfall trapping as flightless birds predominate. We assume that both this site and VV1 are Pleistocene in age, but as just mentioned this site could be younger, and further work is necessary to confirm the age.

However, it seems likely that at least some of these fossils are older than those from New Caledonia, and represent the only Pleistocene crocodylian material from the southwestern Pacific region outside of Australia and Indonesia.

Map references for the sites are: Wainibuku Cave, (O28 722827, edition 1, 1990; 188 039 36.70 S, 1788 299 11.40 E), and; Voli Voli Cave #1, (L29 659713, edition 1, 1992; 188 099 390 S, 1778 289 530 E).

Collection Abbreviations MNZ, Museum of New Zealand Te Papa Tongarewa, Wellington; QM, Queensland Museum, Brisbane.

SYSTEMATIC PALEONTOLOGY CROCODYLOMORPHA Walker, 1970 CROCODYLIFORMES Benton and Clark, 1988 EUSUCHIA Huxley, 1875 CROCODYLIA Gmelin, 1788 CROCODYLIDAE Cuvier, 1807 MEKOSUCHINAE Willis, Molnar and Scanlon, 1993 VOLIA ATHOLLANDERSONI, gen. et sp. nov.

(Figs. 2–4, 7–12) Holotype MNZ S37341, a right frontal (Wainibuku Cave).

Referred Specimens Wainibuku Cave: MNZ S37345, right lacrimal; MNZ S37337 and MNZ S37336, two right postorbitals; MNZ S37342, fused parietals; MNZ S37339, right quadratojugal; MNZ S37346, left quadrate; MNZ S37344, left ectopterygoid; MNZ S37343, basisphenoid; MNZ S37332, left dentary (with two crowns) and angular; MNZ S37331, left dentary (with one replacement tooth); MNZ S37333, right angular; MNZ S37332, left angular; MNZ S37334, right surangular; MNZ S37338, right splenial; MNZ S37355, 42 isolated teeth

(five fragmentary); MNZ S37347a, cervical neural arch; MNZ S37376, incomplete neural arch; MNZ S38191, centrum; MNZ S38192, four cervical ribs; MNZ S38193, six dorsal ribs; MNZ S38194, right scapula; MNZ S37348, right humerus; MNZ S37350, radius; MNZ S37349, left ischium; MNZ S37352, right tibia; MNZ S37351 and MNZ S38188, two metapodials; MNZ S37354, 35 isolated osteoderms. Voli Voli Cave: MNZ S37158, premaxillary fragment; MNZ S38181, right squamosal; MNZ S38182, right quadratojugal; MNZ S36975, half of dorsal(?) vertebra; MNZ S38184, centrum; MNZ S38185, left(?) ulnare; MNZ S38186, fused centrale 1 distal carpal I; MNZ S37161 and MNZ S38187, two incomplete proximal femora; MNZ S38190, two isolated osteoderms; MNZ S37156, one isolated osteoderm.

Etymology Volia in reference to Voli Voli Cave, where the largest specimen was recovered, and athollandersoni for Prof.

Atholl J. Anderson, in recognition of his contributions to the understanding of the prehistory, human settlement and Quaternary paleoecology of the southwestern Pacific islands.

Type Locality Wainibuku Cave, Wainibuku Valley, Viti Levu, Fiji.

Age Presumed Pleistocene.

Diagnosis Strongly rising orbital rim on frontal, and marked inclination of dorsal surface of anterior process of frontal to form prominent trough. If, as seems plausible, all this material pertains to a single taxon the following autapomorphies can be added: a prominent sulcus in the margin of the squamosal that contributes to the supratemporal fenestra; posterolaterally projecting process of squamosal (overlying paroccipital process) absent; anterior (or maxillary) process of ectopterygoid flattened to form a narrow horizontal shelf; and an external buttress of the surangular.

DESCRIPTION For the description, this material is assumed to represent a single species: the reasons for this assumption are given in the ‘Discussion’. Because this material represents the best-preserved, as well as the most complete disarticulated cranial material of a Quaternary mekosuchine crocodylian, this unprecedented opportunity is taken to present a detailed description of as much of mekosuchine osteology as is preserved for this taxon. The description emphasizes noteworthy features of Volia

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athollandersoni, and the general description of crocodylian cranial elements given by Iordansky (1973) is used as a basis.

Preservation The material from Wainibuku Cave is better preserved than that from VV1. The Wainibuku material is largely complete or with only slight breakage at the margins of bones, tips of processes, and bases of isolated teeth. The two exceptions are a procoelous centrum (MNZ S38191) and a right tibia (MNZ S37352). Damage to the left ischium (MNZ S37349), incomplete distally and lacking both iliac and pubic articular surfaces, is less severe. The rim of the cotyle, the entire condyle and the (presumably) broken bases of the pedicles of the centrum are all much worn and abraded. The tibial shaft (Fig. 11D, E) is well preserved but the articular surfaces, particularly the proximal, are incomplete and broken. The material from VV1 shows more breakage. The proximal articular region of femur MNZ S38187 is missing, and judging from the red cave earth present at the break, the break occurred prior to burial. The distal break is just proximal to the middle of the shaft, and is oblique. The other femur (MNZ S37161) is slightly more complete, with its shaft broken at the same point, but with about 60% of the proximal articular surface remaining.

Skull Premaxilla A fragment from VV1 (MNZ S37158), with one complete alveolus, and the adjacent margin of another, is from a premaxilla (Fig. 2A, B). No teeth remain, but part of the rim of the external naris is preserved medially. The complete alveolus preserved is probably that of the third premaxillary tooth because it lies at the junction of the thin anterior part of the narial rim with the thicker posterior part, as does that of Crocodylus porosus. This alveolus has a raised rim and is separated from the incomplete alveolus of the ?fourth premaxillary tooth by a shallow sulcus. On the opposite, mesial side a deeper sulcus probably includes an accommodation pit for one of the dentary crowns. The external, dorsal face is ornamented with small pits, like foramina but not clearly extending through the bone. In lateral view, the dorsal margin (here formed by the narial margin) is inclined at approximately 358 to the ventral margin (Figs. 2B, 7A).

Lacrimal The right lacrimal, from Wainibuku, (MNZ S37345) is complete (Fig. 2C, D). It is roughly rectangular in form, 23 mm long by 15 broad. It is deeply embayed posteriorly by the orbital margin. Externally, the bone bears a prominent, rugose ridge along its medial margin, which in turn bears a few pits, smaller than those of the frontal. The remainder of the external face is relatively smooth. The openings of the nasolacrimal canal are large relative to the size of the bone (as is the canal itself), the posterior being 3 mm in (dorsoventral) diameter and the anterior 7 mm wide by 2 high.

Frontal The right frontal from Wainibuku (MNZ S37341) is incomplete, and relatively broad. It is broken from its antimere medially (Fig. 3), and its dorsal face is marked by prominent pits. The orbital rim rises markedly from the central body of the bone. The anterior process is flexed downwards medially, so that the frontals together must have formed a prominent trough into which the nasals inserted. Ventrally the crista cranii frontales forms a prominent curved ridge set well medial to the orbital margin. The contacts with the prefrontal and postorbital are overlapping, but that for the parietal is a sutural butt joint.

This piece articulates with the parietal MNZ S37342, suggesting that they derive from the same individual.

Parietal The well preserved parietal (MNZ S37342, from Wainibuku) is complete, and its form may be seen in Figure 2G, H. The antimeres are completely fused along the midline, and have an almost transverse contact with the frontals. Dorsally the parietal is shallowly concave both transversely and longitudinally. Its dorsal surface is marked by prominent, dis-

tinct pits in an asymmetric pattern. The supratemporal fenestrae are bounded by a distinct, raised rim. The ceiling of the endocranial cavity is broad, narrowing posteriorly, with the cristae cranii parietales restricted to the lateral margins of this part of the parietal. The contact surface for the squamosals is deeply interdigitating and the posttemporal passage forms a deep embayment interrupting this contact surface. Ventrally, half of the length of the parietal is occupied by the contact surface for the supraoccipitals, which were thus presumably quite large. The supraoccipital was received into a prominent notch in the posterior margin.

Postorbital Two postorbitals were collected from Wainibuku, the left (MNZ S37337) more complete and slightly larger than the other (MNZ S37336), a right (Fig. 2E, F). The left is almost complete, missing only the anterior rim, and the smaller is missing part of the posterior moiety. The smaller articulates with the frontal (MNZ S37341) and parietals (MNZ S37342) (Fig. 3). The dorsal face of the postorbital—which when articulated with the parietals is horizontal rather than inclined like that of the frontal—is marked with pits, somewhat shallower and less distinct that those of the nasal, frontal or parietal. The rim of the supratemporal fenestra is smooth, but not raised as on the parietals. The postorbital bar, complete on both specimens, is stout and triangular in section. It is slightly inset from the lateral margin of the bone. There is no posterior descending process.

Squamosal A right squamosal (MNZ S38181) was found at VV1. It is nearly complete, with only the anterior portion (that contacted the postorbital) missing. Its form may be seen in Figure 2N, O. The dorsal surface is generally horizontal, rising slightly to the lateral edge and is deeply pitted with rounded impressions, in a slightly radiate pattern. The lateral edge and that for the parietal contact are parallel and both are perpendicular to the posterior margin. On the posterior face, a pronounced difference is seen between the posterior subdermal surface and that giving rise to the m. depressor mandibulae.

The subdermal portion is roughened with very small foramina or foramen-like pits, and substantially overhangs the muscular attachment surface—that surface is smoother with similar, but subdued, surface structure medially, and smooth laterally.

The lateral margin of the dorsal surface is roughened with small pits and grooves, and overhangs the horizontal portion of the narrow, L-shaped lateral face. This is almost matched by a lateral shelf along the ventral margin, so that a deep laterally facing groove, affording attachment for the musculature of the ear flap, extends along the squamosal part of the margin of the skull deck. This ‘ridge’ bears a prominent foramen, as does the face below it. The descending process, that contacts the paroccipital process and corpus quadrati, descends almost vertically.

The ventral surface of this bone is more or less flat, with a sharp, descending marginal ridge (broken anteriorly), and two shallow depressions that formed the roof of the external otic recess. Only a small portion, approximately 25%, of the rim of the supratemporal fenestra is preserved. This margin of the squamosal bears a deep, horizontal groove (in turn with prominent foramina), so that there are, in effect, both an upper and lower rim to the fenestra on the squamosal.

Quadratojugal A flat, elongate element (MNZ S38182) with sutural contacts on the two long sides and an external sculpture of shallow pits and tubercles found at VV1 represents a right quadratojugal (Fig. 2K). The element is almost complete, but the anterior process adjacent to the laterotemporal fenestra is missing. The lateral face is very shallowly concave dorsoventrally and bears a swelling posteroventrally that seemingly overlapped the posterior process of the jugal. This structure is broken anteriorly, and the broken surface suggests that it probably extended forward as a flange for about 1.5 cm. The medial

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FIGURE 2. Cranial elements of Volia athollandersoni. Right premaxillary fragment (MNZ S37158) in A, ventral and B, right lateral view.

Right lacrimal (MNZ S37345) in C, internal and D, external view. Right postorbital (MNZ S37336) in E, lateral and F, dorsal view. The anterior margin of this specimen is broken away. Coalesced parietals (MNZ S37342) in G, dorsal and H, ventral view: anterior is to the left. Left quadratojugal, from Wainibuku, (MNZ S37339) in I, medial and J, lateral view. K, Right quadratojugal, from VV1, (MNZ S38182) in lateral view: much of the ventral margin is broken away. Left ectopterygoid (MNZ S37344) in L, ventral and M, lateral view. Right squamosal (MNZ S38181) from VV1 in N, dorsal and O lateral view, anterior is to the right. Basisphenoid (MNZ S37343) in P, dorsal and Q, ventral view, anterior is to the right. Left quadrate (MNZ S37346) in R, lateral and S, ventral view, anterior is to the left. Scales in mm.

face of the element is smoothly concave, with a large foramen posteriorly where the jugal and quadrate approach one another.

The inferior edge bears a sutural contact with anteroposteriorly directed ridges and grooves. The dorsal edge also bears a sutural contact of grooves and tubercles.

Wainibuku yielded a left quadratojugal (MNZ S37339) about 66% as large as that from VV1, and substantially more complete (Fig. 2I, J), although still lacking much of the anterior process. This specimen articulates with the quadrate MNZ S37346. It is a slender element, with a row of deep, elongate pits just dorsal to the contact for the jugal. The posterior swelling seen in the VV1 specimen is less prominent, but this may

be related to its smaller size. A flange overhanging the ventral articulation of the bone extends forward almost to the anterior end of the body of this element. Unlike the rough external face of the VV1 specimen, in this the face dorsal to the row of pits is smooth. There is no indication of a spina quadratojugalis, although it may have been lost.

Quadrate The left quadrate (MNZ S37346) is complete (Fig. 2R, S). It is a flat, rectangular bone (occupying an oblique position in the skull) with dorsal projections. The anterior of these contacts the ventral face of that portion of the squamosal contributing to the skull deck, and the posterior passes between the descending posterior process of the squamosal and the lat-

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FIGURE 3. Fused parietals of Volia athollandersoni (MNZ S37342), frontal (MNZ S37341) and postorbital (MNZ S37336) in A, ventral and B, dorsal view. Anterior is at top, scale in mm. Abbreviations: F, frontal; Nso, notch for supraoccipital; P, parietal; Pof, postorbital; STF, superior temporal fenestra.

eral process of the exoccipital (that forms the paroccipital process). A broad process also projects medially from the anterior half of the medial margin, to contact the lateral wall of the braincase. The anterior margin of the body is deeply embayed by the channel from the supratemporal fenestra.

In general form, the bone is much like that of Crocodylus.

The exposed surface of the bone is smooth, except for that of the otic fossa (anterior to the otic passage), where the surface is rougher, and marked by a field of low ridges, that form a network over the surface, and small pits. The preotic siphonium, immediately in front of the otic passage, is large (4 mm in diameter). The foramen aereum opens into a pronounced sulcus on the dorsal surface of the body about 8 mm anterior of the mandibular condyles, and set 4 mm lateral to the medial margin of the quadrate.

The anteroventral face of the quadrate lacks the extensive development of the characteristic crests for tendinous attachment found in other crocodylians (Iordansky, 1964). Crests A, A9, B9, and D are missing, and crest B, which extends parallel to the posterior margin of the bone, is restricted the region behind and posteromedial to the trigeminal foramen. The region where crest C may be expected is still obscured by adherent matrix.

Basisphenoid A median element of complex shape (MNZ S37343) is a basisphenoid (Fig. 2P, Q). A trough-like angulate sutural contact is for the descending plate of the basioccipital.

The gutter is marked by an open passage extending along its length: this is the canal ascending from the Median Eustachian foramen. The dorsal portion of this passage opens into a vertical, transverse, slit-like cavity that opens on both sides of the element. Free surfaces (as opposed to contact surfaces) form a relatively small part of the surface of this element. Adjacent, but inclined, to the angulate sutural contact is the concave floor

of the posterior portion of the endocranial cavity. A substantial subtriangular pit anterior to this floor, and penetrating posteriorly beneath it, accommodated the hypophysis. On either side of this region, free surfaces of the bone join together ventrally to form a marked sheet-like keel—presumably the base of the basisphenoid rostrum.

Ectopterygoid A left ectopterygoid (MNZ S37344) was recovered from Wainibuku. It is a triradiate bone as in most other crocodylians (Fig. 2L, M), with the anterior (maxillary) process flattened to form a restricted horizontal shelf that would have projected medially from the body of the maxilla.

Cranial Fenestrae The supratemporal fenestra is approximately rectangular in form, with its long axis parallel to the sagittal plane (Fig. 3B). The width of the opening is about 75% of its anteroposterior length. The medial portion of the opening is shallow, floored by a shelf projecting laterally from the parietal. The medial margin of a large posttemporal foramen communicating posteriorly with the otic region via the temporal canal is preserved at the back of this shelf.

Lower Jaw Dentary Two complete dentaries, both left, were recovered (Fig. 4A–F) from Wainibuku. The larger, 148 mm long, (MNZ S37332) retains two crowns (the fourth and thirteenth) in place, and articulates with an almost complete angular. The smaller, 130 mm long as preserved, (MNZ S37331) retains only a single replacement tooth (the fourth). The dentigerous margin shows marked festooning, with the fourth and tenth alveoli occupying the summits of the convex regions of the margin. The fourth alveolus is substantially larger than those adjacent (Fig. 5). In MNZ S37332, the rim of the first alveolus is also noticeably elevated, the only such in the dentary, but is less prominently

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FIGURE 4. Mandibles of Volia athollandersoni from the Wainibuku locality. Larger incomplete mandible (MNZ S37332) in A, lateral, B, medial, and D, dorsal view. Smaller incomplete mandible (MNZ S37331) in C, lateral, E, dorsal and F, medial view. Parallax in F gives a misleading appearance to the position of the posterior margin of the symphysis relative to the alveoli, the position is accurately shown in D. Rearticulated right surangular (MNZ SS37334) and angular (MNZ S37333) in G, lateral and H, medial view. Scales in mm, A–F and G–H to scale.

Abbreviations: Afs, articular facet for splenial; An, angular; ds, trace of sulcus mentioned in text; Fbm, facet for branchiomandibular muscle; FIC, caudal intermandibular foramen; Fm, facet for external mandibular adductor; FME, external mandibular fenestra; Fpp, facet for posterior pterygoid muscle; LR, lateral ridge mentioned in text; Sa, surangular; SR, attachment ridge for zwischensehne.

FIGURE 5. Mesiodistal alveolar diameters plotted against alveolar position for both dentaries of Volia athollandersoni from Wainibuku. The relatively great size of the fourth dentary alveolus (and tooth) can be seen, as well as the relatively large sizes of the posterior dentary alveoli.

Solid line, MNZ S37332; dashed line, MNZ S37331; open circles, estimated values.

so in MNZ S37331. The lower margin of MNZ S37331 is mildly convex in lateral view; that of MNZ S37332 is almost flat, but slightly concave along the mid-section. The external faces of both dentaries are rugose and marked with abundant foramina, many associated with small, posteriorly directed sulci becoming more abundant toward the back. The foramina are arranged irregularly, but there is a distinct row just below the dorsal margin to at least the level of the eighth alveolus. The ornament of the dentaries is noticeably finer than that of the skull elements. Sulci for the reception of maxillary teeth occur on the lateral surface just in front of and behind the eighth alveolus.

The symphyseal region is low and flat, but elevated anteriorly in MNZ S37332 by the raised rim of the first alveolus. The Meckelian groove is sharply marked. The medial face of the dentary bears a clear articular facet for the splenial that extends to a level between the seventh and eighth alveoli: the symphyseal platform extends back to the level of the sixth alveolus. A small, shallow, but distinct sulcus descends obliquely backwards from just medial to the eleventh alveolus. A faint trace of this sulcus continues (on MNZ S37332) for a short distance across the upper surface of the dentary, to a level just in front of the ninth alveolus. The sulcus presumably accommodated a branch of the inferior alveolar nerve or artery.

The alveoli are subcircular in form in MNZ S37332 and separated by distinct partitions. They are generally deep, although the last two (fourteen and fifteen) are quite shallow (4.5 mm for the fifteenth vs. 8.5 for the twelfth). In MNZ S37331 the

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last three alveoli are noticeably shallower, and the last two are confluent. The tenth and eleventh may also have lacked a partition although, because this dentary is broken here, this may be an artefact.

Angular Both a right (MNZ S37333)(Fig. 4G, H) and a left angular (part of MNZ S37332)(Fig. 4A, B) were also recovered at Wainibuku. They are of the same size and so could derive from the same individual. The left is complete, save for the anteriormost and posteriormost extremities. The right lacks more substantial parts of both ends, as well as parts of the medial and lateral portions. This description is based on the left element.

The angular is basically an anteroposteriorly-aligned trough, with a larger lateral and smaller medial vertical sheet. The lateral sheet forms the entire posterior margin of the external mandibular fenestra and the medial sheet the posterior and ventral, and half of the dorsal, margin of the caudal intermandibular foramen. The external face is ornamented with large, irregular pits and sulci, the latter along the ventral margin and becoming smaller anteriorly. The ventral margin of the Meckelian fossa is marked by a prominent, shallowly sigmoid ridge, to which the zwischensehne attached (cf. Iordansky, 1964). Two prominent foramina open on the ventral margin below the attachment for this tendon. Anterior to these, between the Meckelian fossa and the caudal intermandibular foramen, the ventral margin bears a narrow, flat facet, laterally delimited by a low but sharp ridge, presumably for the m. branchiomandibularis. The posterior process of the angular, bearing the attachment region for the lateral part of the m. pterygoideus posterior, flexes medially from the long axis of the mandible at approximately 308.

Surangular The right surangular (MNZ S37334) from Wainibuku articulates with the angular (MNZ S37333). The element is almost complete, lacking only some of the lateral face anterior to the external mandibular fenestra. Its form may be seen in Figure 4G, H. The lateral face is ornamented with large and small pits and bears a pronounced lateral ridge along the dorsal margin, extending anteriorly from the contact for the articular. Dorsal to this ridge is the flat, smooth facet for the attachment of the external mandibular adductors. Corresponding to the flexure of the angular, the posterior portion (that contacts the articular) is medially flexed at about 308.

Splenial The right splenial (MNZ S37338) from Wainibuku articulates with both the angular (MNZ S37333) and the surangular (MNZ S37334). From comparison with the articular surface for this element on the dentary MNZ S37332, about 15 mm of the front of the splenial is missing and (presumably small) parts of the posterior margin are absent as well. The splenial is a smooth, flat, plate-like element flexed laterally along both dorsal and ventral margins. The dorsal margin is sharply flexed, at almost 908, with a low, but distinct, longitudinal ridge at the flexure: the ventral flexure is more gentle.

Mandibular Fenestrae The external mandibular fenestra is oval, with the long axis inclined at about 308 to the horizontal (Figs. 4A, 7A). The opening is almost complete in MNZ S37332, and is placed closer to the dorsal than to the ventral margin of the mandible.

The caudal intermandibular foramen is large, a fenestra rather than a foramen, and situated on the medial face of the mandible just anterior to the external mandibular fenestra. Just over threequarters of the margin of the foramen is preserved in MNZ S37332, where it is a low, elongate, horizontally-oriented aperture (Fig. 4B).

Teeth Thirty-seven crowns (and five fragments) were recovered from Wainibuku, and all are catalogued as MNZ S37355 (Fig.

FIGURE 6. Isolated crowns of Volia athollandersoni from the Wainibuku locality (all catalogued as MNZ S37355) in A, mesial or distal, and B, lingual views. The two crowns at left are of the first form described in the text, the adjacent two of the second form, the adjacent three of the third, and the crown at right of the fourth form. The fourth from right is worn near the tip (seen in lingual view). The third from the right is shown in lingual view only. Scale in mm. Abbreviations: S, sulcus along the carina mentioned in the text; wf, wear facet.

6). A variety of forms are to be seen among the crowns, depending on position in the jaws.

The larger crowns (8–22 mm in height) are conical and mildly flexed (presumably) medially. They are oval in section at the base, becoming more nearly D-shaped higher. This is due, as in Crocodylus porosus, to the development of asymmetricallydisposed mesial and distal carinae that give a strongly convex labial and weakly convex lingual face to the crowns. The labial face is smoothly curved, but on some crowns the lingual face is composed of five or six more or less plane facets with low, longitudinal ridges at their junctions. On others, especially the larger crowns, the facets are indistinct or this face is smoothly curved. The carinae, like that of the fourth dentary tooth described above, bear distinct microscopic perpendicular ridges.

Two very small crowns (6 mm high), with roots attached, are of this form as well.

Seven large crowns (18–23 mm in height) are similar, but in addition to the medial flexure, are subtly to distinctly curved labially near the tip. This gives a slight sigmoid appearance when viewed mesially. The other features of these crowns are like those just described.

Seven crowns (8–101 mm high) are more laterally compressed and broader, with the mesial and distal margin diverging at about 398 (on the preceding types of crown these diverge at about 258). Both labial and lingual faces are curved, but both bear very shallow sulci adjacent to both carinae. The carinae have strongly marked perpendicular ridges that give a serrate appearance, although they are not actually serrate as are the teeth of ziphodont crocodylians. From comparison with C. porosus these are probably posterior teeth. Most of these crowns are smaller than many of the preceding two forms but one is almost as large, consistent with the relatively large size of the posterior dentary alveoli (Fig. 5).

Two even smaller crowns (4–5 mm high) are similar, but broader, with the mesial and distal edges diverging at about 508.

In labial aspect the edges are curved. These differ from those just described in lacking the sulci adjacent to the carinae and in having less distinct carinae and less distinct microscopic

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FIGURE 7. Reconstruction of skull and jaws of Volia athollandersoni in A, left lateral and B, dorsal view. In A the teeth are restored, except for the fourth and thirteenth dentary teeth. In B elements present on only one side have been reconstructed for the other side, and the outline of the left mandible is shown. Scale equals 50 mm.

ridges on the carinae. In the smaller tooth those ridges extend as fine striae over both faces of the crown.

A few teeth show wear. One crown seems to have been broken and developed a wear facet on the break (Fig. 6B, fourth from right). The largest of those of the third type discussed above has lost its tip from wear similar to that described by Molnar (2000) for theropod dinosaurs as ‘tip-rounding.’ Another of these has a longitudinal facet of the lingual face extending to the neck. Other breakage was probably post-mortem.

The dentary crowns surviving in place are slightly laterally compressed, although by no means ziphodont. The fourth is medially flexed and bears prominent carinae mesially and distally and low, blunt longitudinal striae on the lingual surface.

The anterior carina, although much worn distally, basally bears distinct microscopic ridges orientated perpendicular to the edge of the tooth, but serrations are absent. The thirteenth crown is lower than the fourth, more strongly laterally compressed, and blunt. Its tip is strongly worn, and the enamel bears very fine, irregular, vertical grooves.

Vertebrae and Ribs Two vertebrae were recovered from VV1. One is an isolated centrum, the other a little more than the left half of a vertebra (retaining the arch). The two centra are of the same length, but

the neural arch has been disarticulated from the complete centrum, while that of the half centrum is firmly fused in place, without trace of the neurocentral suture. The half vertebra (MNZ S36975) consists of the centrum and neural arch lacking the distal part of the transverse process and the neural spine.

The preserved portions of the arch, including the zygapophyses, are typically crocodylian in form (Fig. 8A, B). The centrum is stepped so that the posterior articular face (condyle) is set ventral to the anterior (cotyle) (Fig. 8B). It is 23.3 mm in length, taking the rim of the anterior face to be vertical, and the vertical diameter of that face at the (medial) break is 10.6 mm.

Centra The isolated centrum (MNZ S38184) is deeply procoelous and in all other obvious features typically eusuchian in form (Fig. 8C, D). It is 21.3 mm in length, 15.4 mm in maximum transverse diameter at its anterior face and 10.7 mm in vertical diameter at that face. As indicated by these measurements, the centrum is mildly depressed. The absence of parapophyses, hypapophyses and facets for chevrons suggests that this centrum, and the half vertebra discussed above, are middle or posterior dorsals.

A procoelous centrum (MNZ S38191) from Wainibuku is so worn that it shows little other than that procoelous centra were present.

Neural Arches Wainibuku also yielded MNZ S37347a, a

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JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 22, NO. 3, 2002 complete cervical neural arch (Fig. 8E, F). It is typically crocodyliform in shape, except for the neural spine. This is vertical or even slightly anteriorly inclined, rather than posteriorly inclined. In Crocodylus acutus, the neural spine is vertical on cervical 5, so MNZ S37347a might represent C5. The spine does not taper distally (as it does in C. porosus) but is incomplete at the tip. Both prezygapophyseal and postzygapophyseal facets are inclined at about 458 to the horizontal. The spine is confined to the posterior half of the arch. The anterior portion has an almost rectangular pit with a smooth floor, but a rugose posterior wall, immediately beneath the anterior margin of the spine: this is apparently for attachment of the interspinous ligament. Posteriorly, there is a distinct excavation, with a ventral rim or floor, between the processes supporting the postzygapophyses near their ventral margins, presumably also for this ligament. The front wall of this pit continues dorsally, tapering, to become a sharp posterior blade that forms the back 40% of the neural spine. This blade is sharply set off from the distinctly broader, anterior moiety of the spine (Fig. 8E). This anterior portion of the spine is asymmetrical, with a shallow sulcus extending up the anterior margin, but only on the left side. The pedicle bears no obvious parapophysis, but is broken anteroventrally. This indicates that the parapophysis was located at the neurocentral junction, and thus suggests that this was an anterior post-axial cervical, in the region of cervicals three to six. Because of the breakage, it is not clear whether the neurocentral junction was fused.

An incomplete neural arch (MNZ S37376), also from Wainibuku, including the middle portions of the laminae and both postzygapophyses but lacking the neural spine and diapophyses, probably derives from a dorsal. The transversely elongate postzygapophyseal facets are inclined at about 128 to the horizontal.

The posterior margin of the spine descended into a distinct pit, floored ventrally by a lamina connecting the ventral margins of the postzygapophyses. As this specimen is so incomplete, it is not feasible to determine from which region of the trunk it originated.

Ribs Four cervical (all MNZ S38192) and six dorsal ribs (all MNZ S38193) were found at Wainibuku, as well as two fragments, probably parts of dorsal ribs. The cervical ribs have three size classes: 14, 18 and 22 mm long along the lateral edge.

The smallest size class includes both a right and left, the other two ribs are both from the right. They are reasonably complete, but only the largest retains both heads. The ribs show the typical crocodylian bicipital head, with a narrow, acutely-pointed anterior process, and broader trough-like posterior process (shaft). The shortness of the shaft indicates that they are all anterior cervical ribs.

The dorsal ribs are all of basically crocodylian shape (Fig. 8G, H), and four are essentially complete, but missing the ventral end or one of the proximal articular surfaces. The two incomplete ribs, both lacking the ventral ends and tubercula, are smaller and more slender. The shafts of the ribs are flattened, most strongly in the two incomplete examples. Three of the more complete ribs bear a low, rounded flange-like process along their anterior edges a few millimeters distal to the bases

�

FIGURE 8. Vertebrae and ribs of Volia athollandersoni. Half vertebra from VV1 (MNZ S36975) in A, dorsal and B, left lateral view. Isolated centrum (MNZ S38184) from VV1 in C, lateral and D, dorsal view.

Isolated cervical neural arch (MNZ S37347a) in E, right lateral and F, anterior view. Three dorsal ribs from Wainibuku (part of MNZ S38193) in G, lateral and H, anterior view. Bars indicate processes mentioned in text. Scales in mm, A–C to scale, with anterior to the left. Abbreviations: Poz, postzygapophysial process; Prz, prezygapophysial facet.

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FIGURE 9. Scapula and forelimb elements of Volia athollandersoni from Wainibuku. A, Left scapula (MNZ S38194) in lateral view. The bar marks a small lump of matrix still adhering to the bone. Right humerus (MNZ S37348) in B, anterior and C, medial view. Right radius (NMZ S37350) in D, anterior and E, medial view. Scale in mm, B–E to scale.

of the tubercula. The fourth rib has, in this position, a more prominent triangular process projecting 4 mm.

Shoulder Girdle and Forelimb Scapula The right scapula (MNZ S38194) from Wainibuku lacks most of the dorsal margin, as well as most of the acromial portion (Fig. 9A). The glenoid articulation is preserved, as is

FIGURE 10. Ulnare of Volia athollandersoni, from VV1 (MNZ S38185), in A, proximal, B, dorsal, and C, distal view, compared with that of Crocodylus porosus, (QM J48126) in D, proximal, E, dorsal and F, distal view. Abbreviations: Das: distal articular surface; Pas, proximal articular surface.

the ventral end of a pronounced acromial process. The lateral face of the scapular blade is convex, and the internal face concave. The blade expands distally, and is 1 mm in thickness, widening to 2 mm along the posterior margin.

Humerus The right humerus (MNZ S37348) from Wainibuku, 90 mm long, is complete, except for the loss of cortical bone from the proximal and distal articular surfaces (Fig. 9B, C).

In form, it is very much like those of living crocodylians.

The most obvious difference is that in anterior or posterior view, the shaft is more nearly straight and the head broader.

There is a pronounced fossa on the flexor surface, immediately distal to the proximal articular surface.

Radius The right radius (MNZ S37350) found at this locality is well preserved and almost complete, lacking only small portions of cortical bone from the margins of both articular surfaces (Fig. 9D, E). It is 62 mm in length. The smoothly walled shaft is very slightly curved (almost straight) and Dshaped in section along most of its length. The slightly concave proximal articular surface is subtriangular in form. The convex distal articular surface is crescentic in form.

Ulnare A very strongly constricted, superficially phalanxlike element from VV1 (MNZ S38185) is identified as a crocodylian ulnare (Fig. 10). The grounds for this are the very strong degree of constriction of the shaft, the extreme expansion of the (presumed) proximal end, the width of which exceeds the length of the element, and the absence of flexor and extensor attachments and of pits for collateral ligaments.

The element has an almost triangular proximal articular surface (for the ulna) with a narrow, strip-like surface for the radiale. The surface for the ulna is shallowly concave. The shaft is roughly triangular in section, with a shallowly convex dorsal surface, a concave ventral face bounded both laterally and medially by sharp ridges, and a convex medial surface. The distal articular surface is roller-like, with a shallow central sulcus, giving it a trochlear appearance (Fig. 10C). The surface subtends an angle of approximately 1408.

Fused Centrale 1 Distal Carpal I A discoidal, inflated bone also from VV1 (MNZ S38186) may represent the fused centrale and distal carpal I. The bone is abraded along its edge

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JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 22, NO. 3, 2002 posteriorly adjacent to the trochanter, is prominent, although shallow. Proximal to the trochanter the anteroposteriorly compressed neck expands abruptly. The anterior (flexor) surface bears a marked fossa laterally.

The other, left, femur (MNZ S37161) is smaller, but slightly more complete than the right (Fig. 11B, C). In diameter, it is about 66% as large as the right, and in form it differs in no significant features.

Tibia A right tibia (MNZ S37352), also from Wainibuku, has a well preserved shaft, approximately 78 mm long, but broken articular surfaces (Fig. 11D, E). The surface of the shaft is covered with fine, but distinct striae and a muscle insertion, possibly for the m. ilio-flexorius, is prominent.

Metatarsal A well-preserved, but incomplete metatarsal (MNZ S37351) was recovered from Wainibuku (Fig. 11F, G).

The trochlear distal end is almost complete, but the proximal has been lost. It is approximately 43 mm long, as preserved.

The shaft is dorsoventrally compressed and prominently expanded proximally.

Osteoderms

FIGURE 11. Ischium and hindlimb elements of Volia athollandersoni.

A, Left ischium from Wainibuku (MNZ S37349) in lateral view. Proximal part of incomplete left femur from VV1 (MNZ S37161) in B, posterior and C, anterior view. Right tibia (MNZ S37352) from Wainibuku in D, anterior and E, medial view. Metatarsal (MNZ S37351) in F, dorsal and G, medial or lateral view. Scales in mm.

and to some extent on both proximal and distal articular surfaces. One articular face is almost completely flat, the other shows pronounced convexity.

Pelvic Girdle and Hindlimb Ischium The left ischium (MNZ S37349), found at Wainibuku, is incomplete (Fig. 11A). The shaft (or blade) of the ischium is similar to that of Crocodylus porosus in form, but the pubic peduncle is substantially more elongate.

Femur Two incomplete femora were found at VV1. One (MNZ S38187) is the proximal portion of a right femur. The fourth trochanter is marked, and relatively broad, occupying more than one-half of the width of the shaft. The ‘summit’ of the trochanter is rounded. Distal to the trochanter (at the break) the shaft is sub-triangular in section. The fossa, for attachment of the puboischiofemoralis and caudofemoralis musculature,

Thirty-five complete osteoderms, and two incomplete, were found at Wainibuku, of five forms (MNZ S37354). Comparison with the skin of Caiman crocodilus (QM J53058) indicates that they probably derive from the dorsum of the neck and trunk, although no exact matches were found. The osteoderms were also compared with those of a skin of Crocodylus porosus (QM J6066), which showed less similarity than those of Caiman crocodilus.

The osteoderms attributed to Volia are of five forms. The first are flat or almost flat, roughly square (or rectangular) elements, with a very low or no keel, distinct round to markedly elongate pits which (when elongate) are arranged in a radiate pattern centered on the center of the osteoderm, and a low shelf along one margin presumably for overlap by the adjacent osteoderm. These measure about 20 3 20 mm, and are interpreted as deriving from the dorsum of the trunk.

In addition are rectangular elements, with a low keel marking a slight angulation between the two sides, distinct round to elongate pits which (when elongate) are arranged transversely, and a low shelf along one (apparently the anterior) margin.

These measure from 15 3 16 to 17 3 19 mm, and are interpreted as also deriving from the dorsum of the trunk.

Smaller (measuring from 7 3 11 to 13 3 20 mm) osteoderms are elongate, oval elements, with a prominent longitudinal keel, and distinct oval pits. These are interpreted to derive from the back (immediately behind the occiput) or side of the neck.

The fourth kind are similar, but larger and broader (measuring about 15 3 16 mm) elements, that are reduced in area on one side relative to other, giving a subtriangular form. These were not well-matched by any scutes seen in Caiman crocodilus, but are most similar to the osteoderms of the fifth form (discussed next), and so may also derive from the dorsolateral margin of the neck (or trunk).

Finally, there are large, strongly keeled elements, with the two dorsal faces meeting at about 1108. These are ornamented with elongate or oval pits arranged transversely and measure 12 (long) 3 25 (broad) mm. From the angulation of the two sides of the osteoderm, these probably derive from the dorsolateral part of the neck.

Three osteoderms were recovered from VV1: the largest (MNZ S38190) is also the more complete, missing only a small portion, about 15%, of its margin (Fig. 12B). The internal surface is covered with minute, approximately orthogonal striae, and the outer surface shows rounded pits of typically crocodylian form. This pertains to the first type discussed above, but is almost twice as big as any of that kind from Wainibuku.

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FIGURE 12. Osteoderms of Volia athollandersoni, from VV1. A, Osteoderm of the second type discussed in the text (MNZ S37156), B, of the first type (MNZ S38190), and C, of the third type (also MNZ S38190), broken along the margins. Scale in mm, all to scale. Abbreviations: k, keel; S, shelves mentioned in text.

That of intermediate size (MNZ S37156) pertains to the second kind, and is only slightly larger than those from Wainibuku but less complete at the margins (Fig. 12A). This osteoderm is strongly keeled over about two-thirds of its length, but considerably flatter over the remaining half. The smallest (also MNZ S38190) is of the third type described above, and is flat with only a subdued keel, extending over about 60% of the length of the scute (Fig. 12C). The margins are broken, with only about 10–15% of the margin remaining. It has a smooth internal face, and a pitted external surface, with some of the pits suggesting a radial arrangement.

COMPARISON The comparison is limited to material from the southwestern Pacific because of availability of specimens and because southwestern Pacific material is considered most likely to be relevant in terms of phylogenetic relationship. Crocodylus porosus ranges broadly over this region (Molnar, 1993) so comparison with C. porosus is made in detail to support the contention that the Fijian material does not pertain to that species.

Characters and character states of Volia athollandersoni and taxa used for systematic comparison (Crocodylus johnstoni, C. novaeguineae, C. porosus, Mekosuchus sanderi, M. whitehunterensis, and Trilophosuchus rackhami) are given in appendices 1 and 2. From these, it can be seen that the material from Fiji

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differs substantially from that of Crocodylus of the southwestern Pacific. The Fijian material is more similar to, although still distinct from, that of the Australian mekosuchines.

Some aspects of the comparison deserve discussion. The squamosal from VV1 lacks the projecting posterolateral extension (overlying the paroccipital process) found in both Trilophosuchus rackhami (Willis, 1993) and Mekosuchus sanderi (Willis, 2001), as well as in C. porosus. This extension, however, is also absent in both species of Paleosuchus. The squamosals of both M. sanderi and T. rackhami have a longitudinal groove in the lateral edge of the squamosal portion of the skull deck, like the Fijian croc. The longitudinal groove of the lateral margin in all three modern species examined lacks the prominent development of foramina seen in the Fijian material, suggesting that V. athollandersoni had a richer vascular supply in this region, presumably for the ear flap and its musculature.

Why the attachment for this musculature is distinctly more prominent than in modern crocodylians remains unknown.

The quadrate is generally similar to those of M. sanderi and T. rackhami. However, although they are from smaller individuals, more of the tendinous crests of the quadrate (Iordansky, 1964) are prominent: at least crests A and B in M. sanderi (QM F31166), and A, B and B9 in T. rackhami (QM F16856). The mandibles of Mekosuchus inexpectatus (Balouet and Buffetaut, 1987) and M. whitehunterensis (QM F31053) (Willis, 1997) also differ from that of V. athollandersoni in being twice as deep at the caudal intermandibular foramen (20 mm) as at the level of the second last alveolus (10 mm) indicating a greatly expanded attachment for the mandibular adductors, by inference also greatly expanded.

Cervicals of mature C. porosus (QM J52809) show the posterior margin of the neural spine produced into a thin sheet similar to, but of lesser extent than in, the Fijian specimen.

Although the ulnare is variable in form in the QM specimens of C. porosus, the Fijian ulnare differs substantially in that: the breadth of the proximal articular surface exceeds the length of the entire element; the distal articular surface is mildly trochlear, rather than shallowly concave; the shaft is not elliptical in section, but has a concave ventral surface; as well as differing in the outline of the proximal articular surface. The second of these differences suggests a closer approximation of the joint surfaces, hence possibly more a hinge-like motion at this joint, that may in turn be related to more terrestrial habits in V. athollandersoni than in C. porosus In modern Crocodylus porosus (QM J48127), the fourth trochanter occupies less than one-half the width of the shaft. The ‘summit’ of the trochanter is sharply angulate (rather than rounded as in V. athollandersoni) and the shaft distal to the trochanter is sub-elliptical in section (as opposed to sub-triangular). The fossa posteriorly adjacent to the trochanter is noticeably shallower. Proximal to the trochanter the neck expands less abruptly, and is anteroposteriorly thicker, than in the femora from VV1. The lateral fossa of the anterior (flexor) surface is much shallower and subdued in C. porosus.

Osteoderms similar to the first kind discussed above are found in the anterior trunk region of Australosuchus clarkae (Willis and Molnar, 1991). These osteoderms agree with those of Volia in being flat, rectangular bones, lacking a keel, with round or elongate pits arranged in a radiate pattern centered on the center of the osteoderm. The osteoderms of Australosuchus so far seen, however, lack the low shelf along one margin presumably for articulation with the adjacent osteoderm.

DISCUSSION Very few elements—only the quadratojugal, vertebral centra and osteoderms—are represented both at Wainibuku and VV1.

Of these, the centra are uninformative as they carry no auta-

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FIGURE 13. Phylogenetic position of Volia as determined by the presence of character states used by Salisbury and Willis (1996). Only about one-third of the states used in that study are determinable for Volia athollandersoni, thus this position is correspondingly tentative. Cladogram modified from that of Salisbury and Willis (1996); lettered but unlabelled nodes represent unnamed taxa.

pomorphies. The quadratojugal from VV1 has suffered considerable breakage, and when this and its greater size are taken into account there are no obvious differences from that found at Wainibuku. The forms of the osteoderms also do not obviously differ. Considering the ecological implausibility of two related moderately large carnivorous crocodylians on the relatively small, isolated landmass of Quaternary Fiji, and pending the discovery of further fossil material, all the specimens are referred to a single species. However, the material is disarticulated and derives from two localities presumed, but not yet known, to be of the same age. Furthermore, the localities, with few exceptions, yielded different elements. Thus, although reference to a single species is conservative, further discoveries are necessary for assurance on this point.

Two femora of different size from VV1 indicate that at least two individuals were represented there. Two left dentaries from Wainibuku likewise indicate at least two individuals there, but some of the isolated crowns are substantially larger than the largest dentary alveoli (9 mm for the crowns vs. 6 for the alveolus), thus suggesting that at least three individuals are represented there. Thus at least five individuals are represented in the two fossil assemblages.

Phylogenetic Affinities The differences, particularly in the cranial bones, from Crocodylus porosus show that this material is not referable that species. There are some resemblances to Mekosuchus. Phylogenetic analyses of Salisbury and Willis (1996) and Brochu (1999) support the existence of a mekosuchine clade, found in Australia and New Caledonia. A full phylogenetic analysis of mekosuchine crocodylians has not been conducted here because of logistical and other constraints. A revision of mekosuchine phylogenetics is part of on-going work by the authors and Volia will be included in future analyses.

Volia shows only 16 of the 44 character states of Salisbury and Willis (1996), given in appendices 3 and 4. Thus its phylogenetic placement is tentative. These states suggest that Volia is a crocodyline (state 40) and a mekosuchine (state 16). State 6 is shared with the Alligatoroidea, but because two states indicate that it is a crocodyline, we suggest this state was inde-

pendently acquired by Volia. State 16 implies that it is a crowngroup mekosuchine, the sister-group of Mekosuchus or Quinkana (Fig. 13).

Following from this, a preliminary analysis, using the characters of appendix 1, was conducted to determine where Volia is placed among the taxa above node P (the second node below R) of Salisbury and Willis (1996). In addition to Volia, the analysis included the four genera above node P (Baru, Mekosuchus, Quinkana, and Trilophosuchus), with the successive sister taxa as determined by Salisbury and Willis as out-groups.

This analysis included several taxa, Baru huberi, Baru wickeni, Mekosuchus whitehunterensis and Quinkana meboldi (all described by Willis, 1997) and Mekosuchus sanderi, described after the appearance of Salisbury and Willis (1996). The analysis was done by hand following the method of Wiley et al.

(1991), in view of the small number of characters and taxa involved. Missing data were treated by considering both possibilities, i.e., looking at alternative pairs of trees with missing data filled in by 1 for one tree and 0 for the other. This method introduced uncertainties regarding the distribution of character states among some nodes, but did not affect the form of the tree.

Volia was found to be the sister group of Mekosuchus or Quinkana, supported by character states: prominent orbital rim of frontals with the crista cranii frontales placed near the midline; a large preotic siphonium relative to size of otic passage; anterior process of ectopterygoid flattened to form a narrow horizontal shelf; and posterolaterally projecting process of squamosal (overlying paroccipital process) absent. Only one character state (great disparity in tooth size, inferred from the disparity of alveolar size) is shared by Mekosuchus and Volia, but not Quinkana. However this character state is an apparent reversal in Quinkana, and plesiomorphic for mekosuchines. Thus the relationships between Volia, Mekosuchus and Quinkana are provisionally regarded as an unresolved trichotomy.

Autapomorphies of Volia include: a marked inclination of dorsal surface of anterior process of frontal to form a prominent trough; elevated rim of parietal portion of supratemporal fenes-

MOLNAR ET AL.—PLEISTOCENE CROCODYLIAN FROM FIJI tra; and relatively large pits in ornament of skull deck (an apparent reversal).

Synapomorphies of Volia, Mekosuchus, Quinkana, and Trilophosuchus include: a marked notch in the parietals for the supraoccipital, that would have had a broad dorsal exposure on the skull roof; lateral margin of squamosal with a deep, horizontal groove; broad exposure of postorbital on skull deck; postorbital bar triangular in section, and slightly inset from lateral margin of (dorsal) body of bone; margins of quadratojugal more or less parallel; body of postorbital, contributing to skull deck, thick; medial margins of supratemporal fenestrae straight and nearly parallel; and skull deck ornament of many, closelyspaced pits.

Synapomorphies of Volia, Mekosuchus, Quinkana, Trilophosuchus, and Baru include: reception pit between premaxillary teeth 3 and 4 absent; and anterior portions of frontals weakly depressed.

Volia has a variety of character states usually seen in mekosuchines, including great disparity in tooth size (inferred from the disparity of alveolar size, Fig. 5), an alveolar process and a prominent wedge of the supraoccipital exposed on the dorsal surface of the skull deck (Salisbury and Willis, 1996; Willis, 1997). There are also a number of features, that have not previously appeared in the literature, that may prove characteristic of mekosuchines. These include an angle on the lateral margin of the dentary near the fourth tooth (in dorsal view: Fig. 4E, but not apparent in Figure 4D because of perspective), a mandible that curves inward posteriorly (Fig. 4D) and a deep horizontal groove on the lateral margin of the squamosal (Fig. 2O). Volia has an enlarged nasolacrimal canal, also seen in other mekosuchines, that could be a paedomorphic feature.

While the previously mentioned characters indicate a relationship to mekosuchines, and specifically Mekosuchus, other characters, in addition to the autapomorphies given above, exclude the Volia material from Mekosuchus. Volia has a deeper symphyseal region, the external mandibular fenestra is open and prominent (although small) and the frontal is not as broad between the orbits as in Mekosuchus. Also, Volia lacks the prominent cranial crests of Trilophosuchus and is not ziphodont as in Quinkana.

Taphonomy The taphonomy of the VV1 site is difficult to interpret but the fragmented nature of the material, which comprises mainly terrestrial species, suggests it may have been scavenged or predated, probably by the crocodylian. The fossils are buried in massive unstructured sediment so fluvial deposition is unlikely. The slickensides in the matrix indicate alternate wetting and drying of the lateritic clays, which probably contributed to the crushing of many fossils, but not those of the crocodile. Subsequent diagenesis has resulted in sediment compaction and may have contributed to the crushing of the specimens.

The elements from Wainibuku are often complete, and apparently derived from a disarticulated skull (or skulls), which in turn suggests that these represent juvenile individuals in which the skull elements had not yet become tightly joined. In skulls of comparable size of C. porosus and other mekosuchines in the Queensland Museum collections, the corresponding elements are all tightly joined. However, long soaking can permit a crocodylian skull to become disarticulated. This suggests that either the Fijian material derives from younger individuals than the other crocodylian skulls, or that this material was submerged for a long period. Given the relatively small area of even Pleistocene Fiji, the population presumably would have been small.

Almost all specimens seem unworn, except for a few localized patches of possible wear. From inspection, the material from VV1 appears to be original bone, little altered except for staining and the loss of organic components, leaving the bone

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chalky. That from Wainibuku, however, appears externally to be finely preserved bone, but the breaks reveal no internal bony structure whatsoever. Instead the surfaces show conchoidal fracture, very like that of cryptocrystalline quartz. When mildly jostled together they produce a metallic tinkling sound. We conclude that these specimens are pseudomorphs, but the material of which they are composed remains unknown.

Paleozoogeography Molnar (1993) argued that in the southwestern Pacific region the genus Crocodylus shows a zoogeographic pattern of insular endemic species ‘superimposed’ on the broad range of C. porosus. Pleistocene fossils indicate that a similar pattern probably existed, but involving a widespread endemic genus, Mekosuchus, and its close relatives, rather than a widespread species (Molnar, 1993). Mekosuchus has been found in Australia and New Caledonia, and an undetermined crocodylian in New Zealand (Molnar and Pole, 1997).

The discovery of the Fijian crocodylian extends this pattern to Fiji. Thus the radiation of mekosuchine crocodylians encompassed not only Australia, but also large southwestern Pacific islands.

The distribution of mekosuchines is similar to that of meiolaniid chelonians in that these tortoises also have a long fossil record in Australia, and are found in the Pleistocene deposits of some southwestern Pacific islands (Balouet, 1991).

Determining whether the mekosuchian distribution is due to dispersal or vicariance is difficult because of the absence of a pre-Pleistocene fossil record, and the uncertainties of reconstructing the geological history, of Fiji. Balouet (1991) concludes that many New Caledonian animals were already part of its fauna during the Mesozoic, when it was still adjacent to (effectively part of) the Australian-Antarctic continent, i.e., they are vicariant. Other forms, e.g., Varanus, clearly arrived later, probably dispersing along the then-emergent Rennell Ridge from New Guinea or Australia (Balouet, 1991). There is no obvious reason why mekosuchines could not also have dispersed in this fashion. Most of the modern flora is thought also to have reached New Caledonia by dispersal (Talent, 1984).

New Caledonia seems to have been largely submerged during the Miocene, although obviously not so much as the eliminate the vicariant component of the fauna (Balouet, 1991). The discovery of a Miocene crocodylian on New Zealand (Molnar and Pole, 1997) suggests that crocodylians (perhaps mekosuchine) may pertain to the vicariant component of the faunas of large southwestern Pacific islands, an interpretation supported by the existence of Platymantis, salt-intolerant frogs, in Fiji. These considerations suggest that both dispersal and vicariance are plausible mechanisms for the distribution of mekosuchine crocs in the southwestern Pacific.

Land was present on the Fijian Plateau, probably continuously, since late in Early Miocene times, at least intermittently during the Late Oligocene, but probably not prior to the Eocene (Chase, 1971). Chase (1971) argues that Fiji originated as part of the Australian plate during the Eocene, adjacent to the Vanuatu island arc. This region apparently moved north-eastward about 60 million years ago from its earlier position off the northeastern continental shelf of Australia (Veevers, 1984). Fiji separated from Vanuatu less than 10 million years ago. Thus all of these lands originated near Australia, where the mekosuchine lineage is known to date back at least to the Eocene (Willis et al., 1993). Furthermore New Zealand originated near the Ross Sea region of Antarctica. Thus mekosuchines, and possibly meiolaniids, could have inhabited these lands from their formation. Considerable further study of the relationships of Fijian animal, as well as of the other mekosuchines, is necessary before the issue of whether or not their distribution is due to vicariance can be resolved. The discovery of meiolaniid turtles, a lineage dating at least to the Eocene in South America, in New Zealand would support this interpretation of vicariance.

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This interpretation would also suggest that fossils of mekosuchians might be expected to be found on other islands in the New Zealand-New Caledonia-Fiji-Solomons region, but not as far east as Tonga or Samoa.

Paleobiology The squamosal from VV1 is rugose along its posterior and lateral margins and deeply sculptured dorsally, suggesting a mature animal. Furthermore, it is too large to pertain to any of the individuals from Wainibuku. Nonetheless it became disarticulated, rather than broken, from the paroccipital process and parietal, suggesting that it derived from a young individual. The cranial (and jaw) bones from Wainibuku are also all disarticulated, rather than broken apart (the dentary and angular in Fig. 4 are glued together). Together with the large size of some isolated crowns, this indicates that all of the material—except possibly the largest represented at each site—is from immature animals. This is supported by Iordansky’s (1973) observation that the development of these crests on the quadrate for attachment of the adductor tendons is dependent on age of the individual, and as the Wainibuku specimen is smaller than that from VV1, it may have been immature and not yet developed some of these crests.

The absence of extensive development of the characteristic crests of the ventral surface of the quadrate (for tendinous attachment) found in other crocodylian quadrates, if not due to immaturity, suggests less complex adductor architecture, with fewer tendons. The premaxilla suggests that the snout was deeper than in C. porosus, and terminated more abruptly anteriorly.

One right femur (MNZ S38187) is about 33% smaller in diameter than the corresponding diameter of that of QM J48127 (C. porosus), which was 3.58 m long. This suggests that this individual from which the femur derived might have been about 2–3 m long. The left quadrate (MNZ S37346) is, as near as can be determined, the same size as those of a juvenile C. porosus skull in the Queensland Museum (QM J48379): that skull is 211 mm long (snout to occipital condyle). If the skulls were similar in proportions, the Fijian skull from which this element derived would have been about that length.

The differences of the quadratojugals from VV1 and Wainibuku may be related to overall size, but other explanations are possible. They may indicate that two taxa were present or sexual dimorphism or, perhaps more relevant to an insular habitat, that there were dietary differences, one of animals having a diet with less calcium. In zoo specimens, this results in ornament with thinner walls and shallow pits (Brochu, pers. comm., 2000).

In the absence of any mammalian and lacertilian predators, this crocodylian was presumably the top carnivore of the Pleistocene and prehistoric Holocene Fijian Islands. It may have preyed upon the large birds and iguanids found there (Worthy et al., 1999) or, alternatively, on fish. The existence of both sharp (anterior) dentary teeth with blunt, but compressed, posterior ones suggests that the posterior teeth might have crushed hard but thin structures, such as snail shells or insect cuticles, or even bird or frog bones.

ACKNOWLEDGMENTS Staff at the Fiji Museum were instrumental in facilitating the fieldwork that led to the discovery of the specimens. Particular thanks are due to Kate Vusoniwailala (Director), Mrs. Tarisi Sorovi-Vunidilo (Archaeologist), Sepeti Matararaba (Mata) (Field officer), Jone Naucabalavu, William Copeland, and Kalpana Nanda (Museum education officer). Gavin Udy of New Zealand, Sepeti Matararaba (Fiji Museum), and Atholl Anderson (Australian National University, Canberra, Australia) helped THW collect the material.

We also wish to thank the Roko Tui Nadroga/Navosa, Mr.

Inoke Kedralevu, and the Provincial Officer, Mr. Uraia Kunaturaga, for introducing us to Mr. Savenaca Batimala (Turangani-koro, Voli Voli Village), and to Mrs. Latileta Tubou (owner) and Mr. Nemani Tubou, for allowing access to their land and Voli Voli cave. Mr. Dharam Singh kindly allowed us to work in Wainibuku Cave.

The fieldwork that produced the specimens reported here was made possible by the financial assistance of the Wenner-Gren Foundation, the Royal Society of New Zealand and the Australian Research Council to A. J. Anderson, who directed the multi-disciplinary project on the colonization of Fiji and its effects, of which this research is part.

We gratefully thank Alan Tennyson (Museum of New Zealand Te Papa Tongarewa), Patrick Couper (Queensland Museum) and Steve Salisbury (University of New South Wales) for their help to this study, and Jeffrey Wright and Bruce Cowell (Queensland Museum) for the photography. We also appreciate the helpful assistance of the two anonymous reviewers and the editor, Christopher Brochu.

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Brochu, C. A. 1999. Phylogenetics, taxonomy, and historical biogeography of Alligatoroidea. Society of Vertebrate Paleontology Memoir 6:9–100.

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Received 19 May 2000; accepted 7 November 2001.

APPENDIX 1 Characters and character states used for comparison of Volia athollandersoni with other Australian mekosuchines and some modern species of Crocodylus.

1. Angle of rise of dorsal margin of premaxilla: c. 208 (0); c. 358 (1).

2. Deep reception pit between premaxillary teeth 3 and 4 (0); this pit absent (1).

3. Deep notches laterally visible between teeth on premaxilla (0); such notches absent (1).

4. Lacrimal ridge: prominent and narrow (0); low and broad (1).

5. Openings of nasolacrimal canal: small (0); large (1).

6. Anterior portions of frontals: not depressed (0); depressed (1).

7. Anterior portions of frontals: weakly depressed (0); strongly depressed (1).

8. Ratio of length of frontal to half interorbital distance: less than 5 0.2 (0); greater than 0.2 (1).

9. Crista cranii frontales: near orbital rims of frontals (0); substantially inset from orbital rims (1).

10. Orbital rim of frontals: not elevated (0); elevated (1).

11. Skull deck ornament of: many, closely-spaced pits (0); few, widelyspaced pits (1).

12. Medial margins of supratemporal fenestrae: not nearly parallel and straight (0); nearly parallel and straight (1).

13. Exposure of postorbital on skull deck: small (0); broad (1).

14. Body of postorbital contributing to skull deck: thin (0); thick (1).

15. Descending process of postorbital: not inset from lateral margin of (dorsal) body of bone (0); inset (1).

16. Descending process of postorbital: robust relative to body of bone (0); slender (1).

17. Cross-section of descending process of postorbital: rounded (0); triangular (1).

18. Lateral margin of dorsal surface of squamosal: not elevated (0); slightly elevated (1); distinctly elevated (2).

19. Longitudinal groove in lateral margin of squamosal: absent (0); present (1).

20. Occipital face of squamosal: inclined c. 608 posterior to the vertical (0); almost vertical (1); vertical (2).

21. Parietal rim of supratemporal fenestra on skull deck: not elevated (0); elevated (1).

22. Posterior margin of parietal for supraoccipital: lacking or with small notch for supraoccipital (0); with large notch for supraoccipital (1).

23. Bony surface of otic fossa covered by: field of rounded foramina (0); field of foramina and anastomosing ridges (1).

24. Preotic siphonium: small (0); large (1).

25. Sculpture of external surface of quadratojugal: absent (0); present (1).

26. Sculpture of external surface of quadratojugal: weak (0); prominent (1).

27. Margins of quadratojugal: not parallel (0); more or less parallel (1).

28. Posterior portion of quadratojugal: not swollen (0); swollen and overlapping jugal (1).

29. Flattened anterior process of ectopterygoid: absent (0); present (1).

30. Flattened anterior process of ectopterygoid: narrow (0); broad (1).

31. Posterolaterally projecting process of squamosal (overlying paroccipital process): present (0); absent (1).

32. External mandibular fenestra: open and prominent (although small) (0); closed (1) 33. Posterior margin of external mandibular fenestra: not nearly vertical (0); nearly vertical (1).

34. Alveolar process of dentary: absent (0); present (1).

35. Angle on the lateral margin of the dentary near the tooth 4 (in dorsal view): absent (0); present (1).

36. Anterior process of surangular: not descending (0); sharply descending (1).

37. Dorsal margin of surangular: lacking lateral buttress (0); with lateral buttress (1).

38. Retroarticular process: deflected medially at c. 158 (0); deflected medially at c 308 (1).

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39. Substantial disparity in size of dentary alveoli, hence—by inference—of dentary teeth: absent (0); present (1).

APPENDIX 2 Character states found in Volia athollandersoni and taxa used for comparison. The numbers for the respective character and character state are separated by a period (e.g., 10. 1).

Volia athollandersoni: 1. 1; 2. 1; 3. 1; 4. 1;5. 1; 6. 1; 7. 1; 8. 0; 9. 1; 10. 1; 11. 1; 12. 1; 13.

1; 14. 1; 15. 1; 16. 1; 17. 1; 18. 2; 19. 1; 20. 2; 21. 1; 22. 1; 23. 1; 24.

1; 25. 1; 26. 1; 27. 1; 28. 1; 29. 1; 30. 0; 31. 1; 32. 0; 33. 1; 34. 1; 35.

1; 36. 1; 37. 1; 38. 1; 39. 1 Mekosuchus sanderi: 6. 1; 7. 0; 8. 1; 9. 1; 10. 1; 11. 0; 12. 0; 13. 1; 14. 1; 19. 1; 21. 0; 22.

1; 24. 1; 25. 2; 27. 1; 31. 0.

Trilophosuchus rackhami: 6. 1; 7. 0; 8. 0; 9. 0; 10. 0; 11. 0; 12. 1; 13. 1; 14. 1; 15. 1; 16. 0; 18.

1; 19. 1; 20. 2; 21. 1; 22. 1; 24. 0; 25. 1; 27. 1; 28. 0; 29. 2; 31. 0.

Baru wickeni: 2. 1; 3. 1; 4. 1; 29. 1. 34. 1; 35. 1.

Quinkana spp.

1. 1(inferred); 2. 0; 4. 1; 5. 0; 6. 0; 34. 1.

Crocodylus porosus: 1. 0; 2. 0; 3. 0; 4. 0; 5. 0; 6. 1; 7. 0; 9. 0; 10. 0; 11. 0; 12. 0; 13. 0; 14. 0; 15. 0; 16. 0; 17. 0; 18. 0; 19. 0; 20. 0; 21. 0; 22. 0; 23. 0; 24.

0; 25. 0; 27. 0; 28. 0; 29. 0; 31. 0; 32. 0; 33. 0; 34. 0; 35. 0; 36. 0; 37.

0; 38. 0.

Crocodylus johnstoni: 1. 0; 5. 1; 6. 1; 7. 0; 9. 0; 10. 0; 11. 1; 13. 0; 14. 0; 15. 0; 16. 0; 17.

0; 18. 1; 19. 0; 20. 0; 22. 0; 23. 0; 25. 1; 26. 0; 27. 0; 28. 0; 29. 0; 31.

0; 32. 0; 33. 0; 34. 0; 35. 0; 36. 0; 37. 0; 38. 0.

Crocodylus novaeguineae: 1. 0; 4. 0; 5. 1; 6. 0; 9. 0; 10. 0; 13. 0; 15. 0; 17. 0; 18. 0; 19. 0; 20.

1; 21. 0; 22. 0; 23. 0; 25. 0; 27. 0; 28. 0; 29. 0; 31. 0; 32. 0; 33. 1; 34.

0; 35. 0; 36. 1; 38. 1.

APPENDIX 3 Characters of Salisbury and Willis (1996) found in Volia athollandersoni (original numbering is retained).

1. Postorbital bar level with lateral margin of jugal (0); postorbital bar inset from lateral margin of jugal (1).

2. Vertebrae amphicoelous (0); some vertebrae procoelous (1); all vertebrae procoelous (2).

3. Postorbital bar confluent with lateral margin of skull deck (0); postorbital bar inset from skull deck (1).

5. Third and 4th dentary alveoli confluent (0); 3rd and 4th dentary alveoli separate (1).

6. Robust postorbital bar (0); postorbital bar moderately built (1); postorbital bar thin and rod-like (2).

7. External mandibular fenestrae absent (0); external mandibular fenestrae present (1).

8. Frontal(s) in supratemporal fenestrae (0); frontal(s) excluded from supratemporal fenestrae (1).

11. Splenial in mandibular symphysis (0); splenial excluded from mandibular symphysis (1).

16. Alveolar process absent or low (0); alveolar process moderate (1); alveolar process high (2).

17. Tooth disparity low (0); great tooth disparity (1) (ratio of d4 and d5 less than 0.475).

18. Dorsal exposure of supraoccipital on skull deck small or absent (0); supraoccipital exposure on skull deck large, forming triangular wedge that is anteriorly extensive (1); supraoccipital broadly exposed on skull deck, contacting squamosal and excluding parietal from posterior margin of skull deck (2).

23. Preotic siphonium present (0); preotic siphonium reduced or absent (1).

24. Rotated teeth absent (0); rotated teeth present (1).

27. Preorbital transverse ridge present (0); preorbital transverse ridge absent (1).

32. Supratemporal fenestrae ovate or circular (0); supratemporal fenestrae compressed laterally (1).

40. Anterior border of articular on lingual surface of surangular lacking an anterior process (0); anterior process of angular on lingual surface of surangular (1).

APPENDIX 4 Character states of Salisbury and Willis (1996) found in Volia athollandersoni. The numbers for the respective characters and character states are separated by a period (e.g., 11. 1).

1. 1; 2. 1 or 2 (not 0); 3. 1; 5. 1; 6. 0; 7. 1; 8. 0; 11. 1; 16. 2; 17. 1; 18. 1 (possibly 2); 23. 0; 24. 0; 27. 1; 32. 1; 40. 1