VtrKTEBRATEPALAEONTOLOGYOFATJSruSIA

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CHAPTBR 8

THE DIET OF THE EXTINCTBANDICOOT CHAEROPUSECAUDATUSWendy Wrightl, Gordon D. Sanson2 and C. McArthur2

Int roduct ion . . . . . . . . . . . . .230Analyt ica l Methods . . . . . . . . . . . . . . . . . . . . .230

Molar Morphology and Occlusion . .. . .. . .. .. . .. .230Examinat ion of Gut Contents. . . . . . . . . . . . . . . . . . . . .231

D issec t i on . . . . . . . . . . . . . . . . . . . . . . . 231F ixa t i on o f Gu t Con ten ts . . . . . . . . . . . . . . . . . . . . . 231S ect ioning and Microscopy. . . . . . . . . . . . . . . . . . .23 |

Resu l t s . . . . . . . . . . . . . . . . . . . 232Molar Morphology and Occlusion . . . . .. . .. .. . .. .232

Morpho logy . . . . . . . . . . . . . . . . . . . . 232O c c l u s i o n . . . . . . . . . . . . . . . . . . . . . . . . 2 3 4

Examinat ion of Gut Contcnts. . . . . . . . . . . . . . . . . . . . .234Dissect ion . . . . . . . . . . . . . . . . . . . . . . .234L igh t M ic roscopy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234Transm ission Electron Microscopy

( T E 1 O . . . . . . . . . . . . . . . . . . . . . . . 2 3 sDiscuss ion . . . . . . . . . . . . . . .236Summary and Conc lus ions . . . . . . . . . . . . . . . . . . . . . . . . . . . . .238Acknowledgements . . . . . . . . . . . . . . . . . . . . .239References . . . . . . . . . . . . . . .239P l a t e s . . . . . . . . . . . . . . . . . . . ' 4 0

I)eparrment of zoology, university of Reading, whileknights, P.O. Box 228, Re_ading, R6 62 N, England

Dipartment iy Aorciy and Zoology, Monash IJniversity, Clayton, Victorio 3168, Awtralia.

230 WRICHT ET AL .

INTRODUCTION

The Pigfootcd Bandicoot, Chaeropus ecaudatus, is a rccently extinct member of thePeramelidae, not. having bccn reportcd since 1925 (Ricle 1970). Litcrature on its diet is scarceand conflicting, thc earlicr rcports mainly consisting of anecdotal observations. Krefft (1865)considercd Chaeropus to be herbivorous, while Sturt (1848) dcscribed it as a flesh-eater (inDixon, 1988). Gould listed insects and thcir larvae as well as plant. material as dietary items(in Dixon, 1988), whilc a gut content analysis by Dixon (1988) suggestcd that Chaeroprr.s wzlshcrbivorous.

Taking somc imporunt consideradons into account, a grcat dcal about the dict of a mammalcan be inferrcd from its tccth (Sanson this volume, Chap.7). Chaeropus molars, whileshowing some sirnilariLies [o thosc of othcr bandicoots, arc Lhe most highly specialised(Benslcy 1903) within this group. Thcir devclopmcnt of shearing cresrs i i unique.Conscqucntly, thcre arc no appropriate analogues to comparc them with. However, i l ispossiblc to obrain informaLion about occlusion and thc action of thc tecth from a study of thewear on thc i r sur faccs (e.g.ButJer 1952, Mi l ls 1967, Grcavcs 1972, Rensberger 1978).Coupled wift infonnation about the physical propcrtics of dict:rry itcms and the shape of toothmorphology bcst suitcd to brcak thcm up (e.g. Lucas & Lukc 1984, Frazetta 1988), aknowlcdge o[ functional dcntal morphology cur allow prcdictions regarding the sorls of foodthat particular tccth would bc most. cl ' lcctivc at rcduoing in sizc. For cxample, Hil l (1985)found that ductilc matcrials arc bcsl. cut by shilrp bladcs or points which concentlato force over asmall surface uea. A blunt surfacc tcnds to dcform matcrials without pcnctration, unless alargcr force is applicd. Briu.lc mal.crials can bc shattcrcd duc to a forcc applied by a blunt or asharp surfacc and cvcntual failurc is duc to cracks which form and grow within the material(Gordon 1976). In cxtant anirnals, prcdictions rcgucling dict can be confirmed by dietarystudics. Sanson (1978, 1980), from a study of macropodid molar morphology, concluded thatMacropus rufogriseusandThylogale billardierr wcrc prcdominantly grazers and browsersrespectivcly, although deuiled dictary stuclics for the two specics were unavailable.Subsequently, Flctcher (1980) confirrnc.d thcsc prcdicLions, giving us some confidence that thetcchniqucs havc prcdictive power.

Some spirit prcscrvcd spccirrrcns of Chaeropu.s survive, ancl onc of thcse was kindly madeavailablc by N{s J. Dixon of thc N{uscurn of Vicl.oria. This allowcd cxamination of themorphology of thc digcstivc systcrn and of thc gut contcnts. It is not known whether theanimal was kcpt alivc and fcd in captivity bcforc it dicd. Thus, thc gut contcnts may not reflectthe natural diet.. Howcvcr, in this cr.rsc thcrc is rnuch corroborativc cvidcncc Lo suggcst that thisspccics wus hcrbivorous.

ANALYTICAL METHODS

NIOLAR MORPHOLOGY AND OCCLUSION

Uppcr and lowcr Looth rows of onc rclativcly worn (Muscum of Victoria, MV C468) andonc rclativcly unworn (MV C2900) spccinicn of Chaeropus ecaudatus wcrc photographed usingKodek Panatomic X l ihn on a Wildpholornacroskop M100 camcra. Spccimcns were coatedwith sublimatcd arnmonium chloridc to rcducc rcflcction and il luminatcd using a Volpifibrcoptic lunp. Thc ncgalivcs wcrc placcd on thc shgc of a Nikon V20 Profile Projector, andthc ilnagc, produccd by Lransmittcd light, was traccd onto ransparcnt shccts. Toolh wcar facctswcrc cxamincd undcr rcflcctcd l ight and rnarkcd on lhc tracings. The spccimens were also

DIET OF CHAEROPUS ECAUDATUS .23I

cxamined under a Hitachi 5570 scanning electron microscope. Because of their ranty, thespecimens were not sputter coated, but the teeth had sufficient conductance to produce imageswithout too much flaring. Micrographs were taken of occlusal surfaces using Ilford XPI 400film. Facet development and striation patterns were recorded on the occlusal maps. Thetracings of upper and lower molar tooth rows were superimposed and manipulated to reproduceocclusion ensuring that facets and striae direction matched.

EXAMINATION OF GUT CONTENTS

Disse ct ion

A spirit-preserved specimen (MV C5858) was collected during the Spencer-GillenExpedition (1901-1902) from Barrow Creek, Northern Territory and had since been stored inl07o ethanoL The abdominal cavity had been opened previously and the gut was, therefore,accessible without further damage to the specimen. Minimal cuts in the mesenteries were madeto allow the digestive tract to be displayed. Both the anterior mesenteric and the posteriormesenteric circulatory systems were sevcrcd. Photographs of thc displayed gut were takenusing Kodachrome 25.

Gut contents were removed from various regions of the digestive tract after shortlongitudinal cuts were made in the gut wall. Ligatures prevented the loss of digesta fromunsampled areas and were left in place following the dissection. Samples were taken from tiestomach, the proximal colon, proximal caecum, and disral caccum. Very littlc matcrial waspresent in the stomach, and the contents of this organ wcre l lushcd out with a syringe.Samples were placed in separate vials in

'l}Va alcohol.

Fixation of Gut Contents

The samples were rehydrated by repeatedly changing the ethanol solution, reducing theconcentration of cthanol by l}Vo at. each charge. Samples were centrifuged between each step,allowing liquid to be drawn off with a pipcttc without losing any of the sample. The digesurcmained in each solution for 5 minutes. After reaching a solution of l}Vo ethanol, thcsamples were rinsed twicc in distilled water and ccntrifugcd. Excess watcr was removed with apipctte. 2.5o/o gluteraldehyde in PIPE's buffer was added to each sample and left for t hour.Samples were then centrifuged and thc glutcraldehyde/buffer solulion removed with a pipette.Aflcr two changes of PIPE's buffer, 17o OsOa in PIPE's buffer was added to each sample. Anhour later, the sunplcs were rinsed twice with distillcd watcr and centrifuged. Excess liquid wasrcmoved.

Dchyfuation of the samplcs involvcd repcatedly changing the ethanol solution, increasingtie concenuation of ethanol by l)Vo at each change until a concentration of 90Vo alcohol wasrcached. After two changcs of 95Vo ethanol, thrce changes of dry ethanol wcre made.

Sectioning and Microscop!

Spurr's resin was addcd to cach sample until the solution consisted of 70Vo resin and 90%cthanol. This was lcft for I hour. The concentration of resin was then increascd dropwise toapproximately 80Vo. The suspcnsions wcre stirred regularly during this process. Samples wereccntrifuged and the resin-cthanol solution removed. 1007o resin was added l,o each sample. Thesamples were then lcft for 36 hours. Fresh resin replaced the first l00%o change, and thesamples were pipetted into plastic moukls and placcd in an oven at 70oC for 24 hours.

232 - WRIGHT ET AL.

The hardened blocks were trimmed and sections for light microscopy were cut with glassknives on a Reichert oMu2 microtome. These were ptacea on glass sides ana stained;ithloluidine blue at pH 9 (O'Brien &_McCully l98l). Paraffin oil and'a coverslip were added andthe sections were viewed under a light microscope at. Xl00 and X400. photographs were takenof sections from each area of the. gut using Kodak Ektachrome 160 for a tungJten light source.

Sections for transmission electron microscopy (TElvf) were cut with-glass [niues on aReichert-3 microtome, stained with methanolic urairyi acetare followed by leid cinate 1o nrien& McCully 1981) and examined in a JEOL 200 CX transmission elecrron microscope.

RESULTS

MOLAR MORPHOLOGY AND OCCLUSION

Morphology

The occlusal surface of the upper molar is rectangular in shape Gig. l) and the teeth areseparated by gaps or embrasures which extend to the buccal edges of the teeth. In no otherperamelid does the embra.sure between the upper molars extend this far. The major features ofthe upper molar are similar to those of other bandicoots, such as Isoodon lWrigtrt tggg),although certain structures ha-ve.been emphasised while others have been reduied. itt" upp"imolar is 'tiered'

and can be divided into three areas: the stylar shelf, the buccal tier and'ihelingual tier (Plate la). In Chaeropus the lingual tier is much ieduced and is the smallesr and

St.ASt.B

pr.pac

po.pac

pa

pr.prprpo.prcr

pr

St ,ESt.D

po.rnec

pr.mec

me

po.hycpr. hychy

Buccaltier

Lingn:altiert

BA . F P

L

IStyhr shelf

I

Flgure 1. Occlusal view of an upper molar of Chaeropus. Abbreviarions: A, anterior; B, buccal; hy,hypocone; L, l ingual ; mer melacone; P, poster ior ; pa, paracone; po.hyc, posrhypocr ista; po-_"" ,Postmetacrista; po-pac, Postparacrista; po.prcr, po.tptoro".ista; pr.hyc, preirypocrisra; pr.mec, premetacrista;pr.pac' prep_ara_cnsra; pr, protoc_onei pr.prcr, preprotocrista; St.A, stylar cusp A; St.B, stylar cusp B; Sr.D,stylar cusp D; St.E, stylar cusp E.

lowest 9f any peramelid, with a very small hypocone and protocone. Concomitantly, thebuccal tier has expanded lingually compared to that of the othir bandicoots. The cusps oi thebuccal tier (metacone and paracone), and the crests associated with these, are the majoi featuresof the tooth. The posrparacrista is well developed in Chaeropu.r, extending to stitar "urp Cand emphasizing the Sroove between the post-paracrista and pie-metacrista.-the crests of the

DIET OF CHAEROPUS ECAUDATUS .233

buccal tier are almost parallel and form two adjacent open triangles. The shearing edges showevidence of tooth-tooth contact; that is they have plan'ar attridJn facers @1. tnyl Wltir wear,lhe crests become rounded and show evidence of tooth-food-tootJr abrasion @t. iC;. Attritionfacets are planar with even, generally parallel striations. Abrasion facets, caused by the tooth-food-tooth contact, are rounded with uneven multidirectional striae (Sanson 1980).

The small protocone and hypocone are linkcd by the post-paracrista and the pre-hypocrista.These two crests and the pre-protocrista and post-hypocrista enclose the lingual tiet *O O.fin"the protocone and hypocone. The lingual sidcs of ttrese cusps are polished, and the flat area ofthe lingual tier, between these, does not appear to occlude el. lD).

- Like other peramelids, the occlusal surface of the lower molars of Chaeropu.l is composedof two adjlc"lt 9p"n triangles, one in the talonid and anorher in the trigonid .egions of thetooth (Fig. 2,Pl.2A). The triangles are better defined in Chaeropu.r, and ilre pre-hlpocristid iswell developed, leading from the hypoconid to a point. anterioi to the base bf the entoconid.The height difference between the tiers of the upper tooth effectively prevents the protocone andhypocone from occluding with the lingual cuips of tie lower .olats and allows effectivecontact of the pre-hypocristid against the post-paracrista.

pacd

rnecd

prd

padnpd

po.hycdpr.hycd

BA-]- P

L

Figure 2' occlusal view of a.lorver molar of Chaeropus. Abbreviations: A, anterior; a.c., anrerior cingulum;B, buccal; end, enroconid; hyd, hypoconid; hyld, hyplonulid; L, lingual; mecd, metacristid; med, meraconid;P' .poster ior ; .

pacd, paracr ist id; pad, p" i ""oni4 po.cyd, posrh 'ypocr ist id; prd, proioconia; p.6y"J,prehypocristid.

With wear, the buccal cusps become lower than ttre lingual cusps and, of the buccal cusps,the hypoconid wears faster than the protoconid. The sheaiing cteits lparac.istid, metacristio,pre-hypocri^stid an{ post-hypocristid) show attrition striations,-becoming rounded and showingevidence of tooth-food-tooth abrasion witr wear el. 2B). Only the Uuicat sioes of the ringrajcusps are worn.

.- Trigonid Talonid -

234 - WRIGHT ET AL.

Occlus ion

The occlusal cycle in Chaeropus emphasises fine shcar, as in grey kangaroos, rather thanl.he shear and grind seen in Perqmeles andlsoodon The lingual t ier, used as a grindingplatform in other peramelids, is greatly reduced, and the shearing crests are emphasized in bothheight and lcngth. Shear occurs when two edges pass each other, and material caught betweentlem is loaded with two compression forces not in fte same plane. Brittle materials fail due toforced crack propagation. Ductile materials break due to laminar flow of material away fromthe points whcre force is applied. Eventually, the material tears, or fails in tension, as halfflows one way and half flows the other way. Crushing occurs between two surfaces broughttogether with no translational motion along the plane perpendicular to the axis of occlusion.Grinding is cssentially crushing with an added translational component. so that material issubjected to both compression and torsion. These definitions are modified after Rensberger(1973), Rosenberger & Kinzcy (1976),FrazeLta (1988) and Sanson (1989).

Molar occlusion in Chaeropus consists of the lowcr molars moving antero-lingually acrossthe uppcrs as the jaw closes (Fig. 3A,B). The apices of the lower open triangles, theprotoconids and hypoconids, pass bctween the paracones and metacones. The protoconid passesbctween fte paracone and nretacone of adjacent upper teeth and along the embrasure bounded bylhe postmel.acrista and preparacrista. The embrasure between the uppers allows this to occur.Similarly thc hypoconid passes between the meacone and paracone of the opposing uppermolar. Wear faccts and attrition striations along the cristae and cristids indicates tooth-toothcontact, and it is interpreted that shearing occurs between these edges and their occludingcounterparts. Abrasion striations on the flat areas of the buccal tier enclosed by these crestsindicates tooth-food-tooth conLact. Food caught in this area would be stretched across thetriangles, cut by the shearing edges as the teeth move through one another and deposited in theintervening valleys. Prcsumably, the paracone and metacone grind such material caught in thevalleys of the lowers, and the protoconid and hypoconid would do the same in the uppervalleys.

EXAMINATION OF GUT CONTENTS

Dissect io n

Thc spccimen, draincd of alcohol, had a body mass of 300 gm and a body length ofapproximatcly 20 cm. The caecum was found to bc a simplc, unsacculated organapproximately 5 cm in length, and was relatively empty in this particular specimen. The colonwas relativcly long for such a small animal, about 210 cm. Thc tissues were hardencd by thepreservative but appearcd to have becn considerably expandcd in lifc (Pl. 3). Material from thecolon contained pieces of fibrous planl material. Digcsra from Lhe caecum was made up of fineparticles. All samples conurined subsnntial quanritics of grit.

Light Microscopy

Sections of digesta from the distal caecum conurincd very fine particles of plant material,the largest of which were only a fcw cclls across. Most of the cells at the edges of theseparticles were lysed and empty. Most of the inner cells sti l l conmined cell contents. Someplant fragmcnts conlained fibre bundles. Groups of bacteria were apparent el. 4A), and thcirprescnce conhrmed by TEM.

DIET OF CHAEROPUS ECAUDATUS .235

BA . + - P

L

upper molars

lower molars

Figure 3. Stages in the occlusal cycle of Chaeropus. A, the beginning of occlusion with the buccal cuspsof rhe upper and lower molars aligned: B, towards the end of the occlusal cycle with the lower molars havingmoved lingually and slightly anteriorly across the upper molars.

Particles of plant material found in the proximal caecum were somewhat largcr than thoseof the distal caecum. Often the cells remaincd attached to a midrib. Again, lysed cells appcaredto have lost their cell contents, although this could have occurrcd during preparation. Theseempty cells were most often at thc edgcs of the fragmcnt, or surrounding a crack in thefragment. Large clumps of bactcria wcrc again prescnt (Pl. 48). Histologically, plant materialin samples from the caecum appeared to be from a grass (T.P. O'Brien, pers. comm.). Partrclesin sections from the proximal colon were much larger than those in the caecum. Sections ofgrass nodcs were visible in some preparations (PI. 4C), but the prcscnce of small quantities ofvery dark brown-staining material, probably tannins, suggests that dicotyledonous plantmaterial made up part of the diet, since grasses do not normally conrain hnnins.

Very little digesta was found in the stomach. Fine pafticles of plant material were presenqalong with small rafts of bacteria (Pl. 4D). There was no cvidence of the animal havingingested anything other than plant material and grit.

Transmission Electron Microscopy (fEM)

TEM confirmed the results given above. Bactcria wcre found to be present in sectionsprepared from the proximal caccum (Pl. 5A), the distal caecum el. 5B), the proximal colon(Pl. 5C) and from the stomach (Pl. 5D). Sections of plant material were found only in the

A- i P

236 . WRIGHT ET AL.

distal caecum, but the presence of plant fragments in light microscope sections from other partsof the gut indicates that this was merely a sampling error.

D I S C T J S S I O N

The molars of ChaeropuJ show a suite of dental characters which suggest that it is aspecialist herbivore. The post-paracrista and the pre-metacrista are prominent in the uppermolars, and they are of similar importance to the pre-paracrista and post-metacrista. This is notthe case in any of the other peramelids, where the two central crests (post-paracrista and pre-metacrista) are lower than the pre-paracrista and post-metacrista. The other bandicoots areinsectivorous or omnivorous taking fungus, seeds, root nodules and vascular plant material intheir diet (Quin 1985, Harison 1963, Opie 1980, Lobert 1985). None are recorded as takinggrass. In Chaeropus the lower tooth has lost its talonid basin and is composed of two sets ofcrests, which form open triangles and oppose those of the upper molar in occlusion. Thelingual tier is much reduced, the high shearing crests extending almost to tlte lingual edge ofthe looth, so that the teeth are essentially one-tiered. Gaps between the upper molars allow theprotoconid to fit between adjacent upper molars. If these gaps did not exist, the crests of theprotoconid could not shear past those of the upper tooth. As the upper molars of Chaeropusare square in outline, separation of the upper teeth in particular allows the crests to pass eachother.

How the gaps are maintained between the upper molars is unknown. It is possible that thepresence of the protoconid in the embrasure resists the tendency of transseptal fibres to pull theteeth together. Such a system would theoretically keep the anterior and posterior crests ofadjacent upper molars in close occlusion with the crests of the protoconid.

The shear exhibited by the dentition of Chaeropus can be described as 'fine shear' (Sanson1989). By contrast, 'coarse shear' occurs in systems like the occlusion of the large sectorialpremolars of potoroids and allows thick stems and midribs of plants to be cut, due to a high ordeep shearing crest (Sanson 1989). The crests of Chaeropus, while high compared with thoseof the other bandicoots, are low compared with the thickness of twigs, stems and midribs ofdicotyledonous browse and would be relatively inefficient at cutting these materials. Thethickness of the material would prevent the curved edges contacting each other and generatingshear. Thin, laminar leaves of grasses are effectively reduced by the fine shearing teeth ofgazing kangaroos (Sanson 1989), which have crests on a similar scale to those of Chaeropus.It is interesting to note that Dasyurus, with molars of similar size to Chaeropus, and with animportant shearing component in its occlusal cycle, is also able to shear grasses, reducing themto small particles (Wright 1988). Chaeropus,the peramelid which Bensley (1903) consideredhighly specialised with regard to the dentition, and furthest modified from the ribosphenicdentiLion, appears to have been able to shear grasses even more finely than Dasyurus (Wrightle88).

Few studies are available which deal with the diet of Chaeropus. Gerard Krefft, during anexpedition to the Murray-Darling plains, was informed by local Aborigines that these animalsfed on coarse barley grass. He kept captive animals on lettuce, barley grass, bread and bulbousroots and noted that Chaeropus, unlike other peramelids, did not eat mice or meat which werepresented. Krcfft described the dung of wild Clneropus to be entirely composed of grass, and heconsidered them herbivores (Ikefft 1865).

Dixon (1988) cites Sturt (1848) as reporting Chaeropus to be partial to flesh, and Gould(1863) noted that the diet consisted of insects and their larvae and some vegetation (in Dixon,1988). Dixon (1988) examined two preserved specimens from the Museum of Victoria,concluding that the faecal pellets consisted almost entirely of grasses. This study, and that ofDixon (1988), supports the hypothesis that Chaeropus was primarily herbivorous, with grassperhaps being an important part of the diet. However, the specimens used in both of these

DIDT OF CHAEROPUS ECAUDATUS .237

studies may have been held in captivity for some time bcfore prcservation. If this is the case,results based on gut content analyses will reflect the food items fed [o the captive animals,rather than the natural diet. Howevcr, it is perhaps unlikely Lhat an insectivore or omnivorewould readily eat grass even if that was all that was offercd.

lf Cha-eropus was dealing with grasses, tooth wear anrl the capacity to extract enoughnutrients from a nutritionally poor diet would have been major problems. The shearing creitsof Chaeropus wear vertically, becoming lowcr. The height of th! fingual part of the buCcal tierof the upper molars and the lingual cusps of lhe lower molars wear first (Fh Oe,S). This is tobe expected since these are the important shcaring crests. Wear results in the crests becominglorv and rounded, but they may be kept in tight occlusion by the tendcncy for the upper molarito drift together and rhe presence of the proroconid keeping rhcm aparr (Fig 4). Ir isnoteworthy that the hypoconid, which occludcs onto the surface of rhe uppei molar, wears morethan the protoconid, wltich occludes in the embrasure between successive upper molars.

The problem of such a small animal gaining enough nutricnts from a di-et of plant materialmay have been avoided or iessened by processes such as selective grazing, fermentation andcoprophagy, which appear possible from aspects of this study. Light and transmission electronmicroscopy provided reasonable evidence for a large popularion-of hindgut flora, suggestingthat Chaeropas fermented plant material in the caecum and the large colon. Parallels witfr othersmall hindgut fermenters with separation of contcnts in the colon (Bjornhag 1972), some ofwhich are caecotrophic, are interesting.

I-ee & Cockburn (1985) considered hcrbivory in marsupials to be confined to animals whichhave an adult body weight above 600 g. This is due to the necessity for fte digesta !o spend acertain time in the gut to permit bacterial fermentation of the cell wail components.Chaeropu_s has a body weight of approximately 300 g. Small herbivores tend ro U'e trlgtrtyselective, feeding on relatively easily digested food itcms rich in encrgy and prolein. Chaeropusmay have been a selective grazer, taking only thc nutritious pars of ptants and avoiding fibrousregions of the leaf and the stem, low in readily digestiblc matter. The presence of grais nodesin some of the sections supports this argumcni, as rhe nodes of giass plants ire high inconcentrations of amino acids and proteins (t.P. O'Brien, pers. comm.). Demment (1980) alsonoted that small herbivores often select high quality foods, stating ttrat they often chew-foodmore completely than larger herbivores, !o increase is digcstibility, since there is a shorter gutretention time. He also suggested coprophagy as a mechanism whereby small herbivores danextend the period that the food spends in the digestive rract., The presence of bacterial rafts in lhe stomach of Chaeropus suggests that these animals mayItuu: Egn copro-phagous, reingesting faecal or faecal pellcis whic[ contain nurrienrs providedby the hindgut flora. This is similar to fte situation observed in ringrail possums (OrBrien eta/. 1986).

Fine shear is emphasised in the dentition of Chaeropur at thc expense of other functions,and it appears that this bandicoot was ablc to rcduce grasscs to fini particles. Shearing inChaeropus is extremely fine, and it is unlikcly that. such fine shear has developed for-thecommunition of insects, which can be effectivcly reduced by relatively coarse-shearing crestssuch as those of Dcsyurus (Wright 1988) and Dasyuroides (Moore, t9-86). Grasses arJrich insilica and cause excessive wear in mammalian Lccth. Mature plants and oldcr leaves have ahigher silica content than do younger plants ancl lcaves (Lewin & Reimann 1969). An animalas small as Chaeropus has an advantage ovcr large hcrbivores in tcrms of the scale of thesubstrate to its absolute energy requircments. It has becn suggestcd lhat some small herbivoresare able to survive in this way (}.{orbury et al. 1989). For examplc, the small Hare WallabyLagorchestes hirswus has been shown to selcct the very tips of grisses @olton &Latz 1978).

Chaeropus is describcd herc as a specialist herbivore, probabiy taking a mixture of herbs andgrasses. Selective herbivory, fermentation and coprophagy arc suggestcd traits which may haveenabled this small animal to mcet. and sustain its melabolic requircments. Behavioural and

238 WRIGHT ET AL.

Figure 4' Wear facets on the shearing crests of Chaeropus molars. A, occlusion of the crests of the upperand lower molan along wear facets (shaded); B, edges of the two opposing shearing crests along the line "b"

in (A). Dotted lines indicate successive states of wear, changing from planar facers wirh relatively sharpedges to facers with rounded edges.

nutritional studies to test these proposals are prevented because of the recent extinction of thisanimal, although investigation into the digestive strategies of the extant omnivorousbandicoots may provide some insight as to how Chaeropus maintained itself on a diet ofrclatively lower nutritional quality plant material.

SUMMARY AND CONCLUSIONS

A study of the occlusal morphology and wear of the molars of the extinct bandicootChaeropus ecaudatus, suggests that this animal may have been a herbivore, and more precisely,a grazer. Examination of a spirit-preserved specimen and light and transmission electronmicroscopy of the gut contents supported this hypothesis.

Fine shear was emphasised in the occlusal cycle of Chaeropus, reducing all other functions.The high crests provided enough shearing amplitude so that Ciaeropus walable to reduce plantmaterial, including grasses, to fine particlcs. The shearing molars probably released cell

A

B

DIET OF CHAEROPUS ECAUDATUS .239

contents for digestion in the small intestine and prepared plant material for fermentation in thehindgut. If so, Chaeropus was unique among the Perameloidea, with the capacity forfermentatior of plant material in the hindgut. Coprophagy is suggested as a mechinismwhereby Chaeropus

13y havg prolonged the period thai ptint rat"iit spenr in the digesrivetract, enabling more efficient digestion.

Recently Burbidge et al. (1988) have reported dietary information about various extinct orrare mammals, obtained from_interviewing Aborigines from the centnl deserts and surroundingareas. They_ did not present data unless it was corroborated by two or more groups of people.They stale_that. lhe reported food of Chaeropu.r was "termites

and ants, including troney-potants" (p. 20). We are unable to assess the information in that report, and can only Indicate thatit is not supporred by rhis study.

-. This study emphasises the value of preserved specimens in the determination of possiblediets of extinct species, but it also shows that observation of molar wear patterns can lead touseful speculations about diets of such animals.

ACKNOWLEDGEMENTS

We wish to acknowledge the support. and generosity of Ms Joan Dixon, Curator ofMammals, Museum of Victoria. We alio would l'ike to thank Dr T.p. O'Brien, Or W.l. Fofeyand Ms S. Moore, for their advice, commenls and discussion. The work was supported by agrant from the Museum of Victoria.

REFERENCES

BENSLEY' B'A', 1903. on rhe evolution of rhe Ausrralian Marsupialia; with remarks on rhe relarionships of^-^^-,!,"- marsupials in general. Trans. Linn. Soc. Lond. (2nd seri'es) S, t}-Zti.BJORNHAG' G.' L972. Separarion and delay of content.s in the rabbir colon. Swedisl J. agric. Res.2:125-

1 3 6BoLToN, B'L' & LATZ, P.K., 1978. The Westem Hare-wallaby Lagorchestes hirsulus (Gould)(Macropodidae)

in rhe Tanami Desen. Ausr. Wild!. Res. S: 2gS-293.BURBIDGE, A.A., JOHNSON, K.A., FULLER, P.J. & SOUTIIGATE, R.I., 1988. Aboriginal knowledge of rhe

mammals of the cenrral deserts of Australia. Aust. Wildt. Res. l5: 9_39.BUTLER, P'M ' 1952. The Milk-molars of Perissodactyla, with remarks on molar occlusion. proc. Zoo!

Soc. Lond. l2 l : 77 ' l -81 '1 .DEM-\'{ENT, M'w., 1980. Body S.ize and llerbivory. PhD Thesis, University of Wisconsin, Madison.DIXON, J'' 1988' Notes on the diet of three mammals presumed ro be exrinct: the pig-footed Bandicoot, the__ __!"r."r Bilby and the Desen Rat Kangaroo. Victorian Nal. 105: ZOg_Zll.FLETCHER' H'L', 1980. Browsing damage in Tasmanian fores! areas and affects of 1080 poisoning. Interim

Repo--rt-, Forestry Commission (Tasmania), Depaflmenr. of Agriculture (Tasmania), National parks andWildlife Service (Iasmania).

FRAZZETTA, T 'H' , 1988. The mechanics of cut t ing and rhe form of shark reerh (Chondr ichthyes,_ Elasmobranchi i ) . Zoomorphologyl0g: 93-107.GoRDoN' J'8" 1976. The New

|ri1"ri of Strong Materials or Why You Don'r Fall Through the Floor (2ndEdition) (Penguin Books: Middlesex).

GOULD, J., 1863. Marwrals of Australia. Gould, London.GREAVES, W'S., 1972' The inference of jaw motion from toorh wear facers. J. paleont.4T: 1000-1001.HARRISON, J.L., 1963. The food of somi Innisfail mammals. proc. R. Soc. ed 73:37-43.HILL' D', 1985' Functiona!_ Dental Morphology in Some Snnll Dasywids. Unpublished llonours Thesis,--*__Z"ol9gy Departmenl, Monash Universiry,

-Clayron.

KREFFT, G., 1865. Vertebrara of rhe Lower Murruy. Trans. phir. sac. NSW rg62-rE65: r2-r4.tEt '

AI : - l COCKBURN' A. , 1985. Evolut io iary Ecology of Marsupials. Cambridge Univ. press,

LamDnd Pe.

I IYI I - I -& igIvnxN, B.E.F. , 1969. Si l icon and plant growrh. Ann. Rev. p lant physiot .2o: 289-304.LOBERT, B', 1985. The Ecotogy of rhe Southern bro.n Bandicoot in South-east Australian Ileathland.

Unpublished M.Sc. Thesis, Zoology Dept. , Monash Universiry, Clayton.

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LUCAS, P.W. & LUKE, D.A., 1984. Chewing i t over; basic pr incip les in food breakdown. ln FoodAcqukition and Processing in Primates. D.J. Chivers, B.A. Wood & A. Bilsborough, eds., PlenumPress, New York.

MILLS, J.R.E., 1967. A comparison of lateral jaw movements in some mammals from wear facets on theteeth. Arc l rs. Oral Bio l .12: 645-661.

MOORE, S., 1986. The Functional Molar Morphology of Petaurus breviceps. Unpublished Honours Thesis,Zoology Department, Monash Univenity, Clayton.

NORBURY, G.L., SANSON, G.D. & LEE, A.K., 1989. Feeding ecology of the Macropodoidea. In Kangaroos,Wallabies and Rat Kangaroos. G. Grigg, P. Jarman & I. Hume, eds., Surrey Beatty and Sons, Sydney:1 6 9 - 1 7 8 .

O'BzuEN, T.P. & MCCULLY; M.E., 1981. The Study of Plant Structwe: Principles and Selected Methods.Termarcarphi, Melboume.

O'BRIE}I, T.P., LOMDAHL, A. & SANSON, G., 1986. Prcliminary microscopic investigations of the digestaderived from foliage of Eucalyptus ovata (l,abrlt.) in the digestive tract of the Common Ringtail Possum,Pseudocheirus peregrinus (Marsupialia). Aust. J. Zool. 34:157 -176.

OPIE, A.M., 1980. llabiut selection and the dietof Isoodon obesults. Aust. Mamm. Soc. Bull.6:56.QUIN, D.G., 1985. Aspecrs of rhe Feeding Ecology of the Bandicoots Perameles gunni (Cray, 1838) and

Isoodon obesulus (Shaw and Nodder, 1797) (Marsupialia: Peramelidae) in Southern Tasmania.Unpublished Honours Thesis, Zoology Departrnent, University of Tasmania, Hobart.

RENSBERGER, J.M., 1973. An occlusion model for mastication and dental wear in herbivorous mammals. ,I.Pa leon t . 4T : 515 -528 .

RENSBERGER, J. M., 1978. Scanning electron microscopy of wear and occlusal events in some smallherbivores. ln Developmen!, Function and Evolution of Teeth. Burler, P. M. & Joysey, K. A., eds.,Academic Press, London.

zuDE, W.D.L., 1970. A Guide lo the Native Mamtnals of Australia. Or-ford Univenity Press, Melbourne.ROSENBERGER, A.L. & KINZEY, W.G., 1976. Functional pattems of molar occlusion in platyrrhine

pr imates. Am. J. phys. Anthrop.45: 281-298.SANSON, G.D., 1978. The evolution and significance of mastication in the Macro@idae. Aust. Mammal.2.

23-28.SANSON, G.D., 1980. The morphology and occlusion of the molariform cheek teeth in some Macropodinae

(Marsupialia: Macropodidae). Aust. J. Zool. 28; 341-365.SANSON, G.D., 1989. Morphological adaptations of teeth to diets and feeding in the Macropodoidea In

Kangaroos, Wallabies and Ral-kangaroos. G. Grigg, P. Jarman & I. Hume, eds., Surrey Beatty.Sydney : l 5 l - 168 .

WRIGHT, W., 1988. Functional Molar Morphology in Fow Genera of Marsupial Bandicoots. UnpublishedHonours Thesis, Zoology Department, Monash University, Clayton.

PLATES

Plate 1. Scanning^electron micrographs of the upper molars of Chaeropus. A, Upper tooth row lookingposteriorly from M2 to M4l B, postmetacrista of M3 on a relatively unwom specimen; note the planar facetwith attrition striae; C, preparacrista of MJ on a relatively wom specimen; note the rounded abrasion facet.D, occlusal view of the narrow lingual tier between the paracone and metacone. Abbreviations as for Fig.l.

Pfate 2. A, scanning electron micrograph of the lower molars M2 and M3 of Chaeropus; B, metacristid of

the wom lower molar of Chaeropus; note lhe rounded nature of the crest and the well developed attrition striae.A = anterior.

Plate 3. Gut of Chaeropus ecaudatus (MV C5858) indicating caecum and expanded colon and showing sitesfrom which samples of gut conlents were taken: 1, distal caecum; 2, proximal caecum; 3, proximal colon;4, stomach.

Plate 4. Light micrographs of sections prepared from the gut contents of Chaeropus ecaudatus (C5858)

(X480). A, planr marerial and bacreria prepared from the contents of the distal caecumi B, plant material

prepared from the conrents of rhe proximal caecum; C, section of a grass node from the contents of the

proximal colon; D, plant material and bacreria from the contents of the stomach'

DIET OF CHAEROPAS ECAUDATUS - 24I

Plate 5' Transmission electron micrographs of sections prepared from rhe gut contents of Chaeropusrcaudatus (C5858). A, bacteria and digesta from the contents of the proxirnal caecum (X14,000); B, bacteriaand digestr from the contents of the distal caecum (X27,000); C, bacreria and digesta from the contents of theproximal colon (X20,00O); D, bacteria surrounded by digesta from the conr.ents of the sromach CX27,0O0).

Plrt€ 6. Scanning clectron micrographs of wom molars of Chaeropus ecaudatus. A, lingual view of M2showing rcduced height of rhe tooth on the lingual edge; note the embrasure between adjacent molan; B,posrerior view of the left upper tooth row showing the reduced height of rhe lingual pan of the buccal tier.

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DIET OF CHAEROPUS ECAUDATUS .243

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