MeMoirs - Queensland Museum/media/Documents/QM/... · THE LARGE ASPIDORHYNCHID FISH, RICHMONDICHTHYS SWEETI (ETHERIDGE JNR AND SMITH WOODWARD, 1891) FROM ALBIAN MARINE DEPOSITS OF

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VOLUME 49 PART 2

MeMoirsOF ThE

Queensland MuseuM

THE LARGE ASPIDORHYNCHID FISH, RICHMONDICHTHYS SWEETI (ETHERIDGEJNR AND SMITH WOODWARD, 1891) FROM ALBIAN MARINE DEPOSITS OF

QUEENSLAND, AUSTRALIA

ALAN BARTHOLOMAI

Bartholomai, A. 2004 06 30: The large aspidorhynchid fish, Richmondichthys sweeti(Etheridge Jnr and Smith Woodward, 1891) from Albian marine deposits of Queensland,Australia. Memoirs of the Queensland Museum 49(2): 521-536. Brisbane. ISSN 0079-8835.

Material previously referred to the genera Belonostomus Agassiz, 1834, AspidorhynchusAgassiz, 1833 and Vinctifer Jordan, 1919 from Lower Cretaceous (Albian) marine depositsof Queensland (Australia) is considered to be referable to Richmondichthys gen. nov., withinthe species R. sweeti (Etheridge Jnr & Smith Woodward, 1891). This is shown to be a verycommon and widespread aspidorynchid halecostome (Actinopterygii:Teleostei), the largestspecies within the family. R. sweeti differs significantly from the South American V.comptoni (Agassiz,1841), to which it is nonetheless closely related. Lack of teeth, elongategill filaments, hinged cheek bones and a very deep lower jaw suggest the species was a filterfeeder, possibly a gulper. � Actinopterygii, Halecostomi, Teleostei, Aspidorynchidae,Richmondichthys sweeti, Albian.

Alan Bartholomai, Director Emeritus, Queensland Museum, PO Box 3300, South Brisbane4101, Australia; received 10 March 2004.

Aspidorhynchid fish remains compriseconspicuous and common elements of the fossilvertebrates recovered from widespread localitiesin the Lower Cretaceous (Albian) marine depositsof the Great Artesian Basin in central Queens-land. The majority of referred material fromprecisely recorded localities has been derivedfrom the shallow water, marine sediments of theToolebuc Formation, a unit rich in invertebratefossils and containing not only fish but also a richsuite of marine and some terrestrial reptiles.Rarer aspidorhynchid occurrences are recordedfrom the Allaru Mudstone, also of LowerCretaceous (Albian) age.

The presence of ganoid fish in the Great ArtesianBasin deposits was first recorded by Etheridge(1872) in a collection of fossils from ‘HughendenStation’where they were referred to Aspidorhynchussp. Jack & Etheridge (1892) later referred thismaterial to Belonostomus sweeti, a species thathad been described by Etheridge Jnr & SmithWoodward in 1891, also based on material fromHughenden in central Queensland.

The specimens then available lacked most ofthe cranial elements and the neurocraniumremained undescribed. Over the past century, theavailable sample of remains referrable to thespecies has expanded considerably and aceticacid preparation techniques have permittedpreviously unheard of detail to be revealed fromthe encompassing concretionary, calcilutitestructures in which the fossils are usually

preserved. A much more comprehensive des-cription of the taxon is now possible, enablingbetter comparisons with other genera and species.

Exhaustive studies of other aspidorhynchidsfrom elsewhere in the world have been under-taken by Brito (1992, 1997), including a verydetailed study of related South and centralAmerican species of Vinctifer. Based upon limitedmaterial, Brito regarded the Australian materialas also being referrable to Vinctifer, a conclusionthat is not supported by the present study.

ABBREVIATIONS. Ang = Angular; acv = foramenfor anterior cerebral vein; ant. my. = anteriormyodome; Apto = Autopterotic; art inf = articulationfor Ist infrapharyngobranchial; Aspo = Auto-sphenotic; Boc = Basioccipital; br = branchiostegalray; Bsp = Basisphenoid; ci = foramen for internalcarotid artery; Cl = Cleithrum; Dpt-Exsc = Dermo-pterotico-Extrascapular; Dsp = Dentalosplenial;Dsph = Dermosphenotic; Epo = Epiotic; Epto =Epipterotic; Exo = Exoccipital; fm = foramen magnum;Fr-Pa = Fronto-Parietal; Hymd = Hyomandibular;hymdf = hyomandibular fossa; Ic = Intercalar; ica =foramen for internal carotid artery; Io = Infraorbital;jd = jugular depression; juv = foramen for jugularvein; l.Eth = Lateral Ethmoid; mdc = mandibularcanal; Mx = Maxillary; Na = Nasal; Nerves:; I =olfactory nerve; II = optic nerve; III = commonoccular motor nerve; IV = pathetic nerve; V =trigeminal nerve; V+VII opht = opthalmic trunks oftrigeminal and facial nerves; VI = abducens nerve;VII = facial nerve; VII jugm = jugulohyomandibular

trunk of facial nerve; IX = glossopharyngeal nerve;X = vagus nerve; oa = foramen for orbital artery;occa = foramen for occipital artery; Op = Operculum;Opo = Opisthotic; opp = opercular process; orb. =orbital cavity; Ors = Orbitosphenoid; Pdt = Pre-dentary; pea = foramen for pseudo-branchial efferentartery; Pmx = Premaxillary; Po = Postorbital; Pop =Preoperculum; Post = Post-temporal; Pro = Prootic;pr psp = process of the parasphenoid; Psp = Para-sphenoid; ptf = post-temporal fossa; Pts =Pterosphenoid; ptsp = pterosphenoid pedicule; Qu =Quadrate; Rart = Retroarticular; Ro = Rostral; Scl =Sclerotic Ring; Sclt = Supracleithrum; Soc = Supra-occipital; Sor = Supraorbital; Sop = Suboperculum;1st vert. = first vertebra; Vom = Vomer.

All Queensland Museum specimens areidentified with the prefix QMF. Material fromother collections is identified by institutionwherever they are referred to.

Class OSTEICHTHYSSub-class ACTINOPTERYGII

Division HALECOSTOMI (sensu Patterson, 1973)Sub-division TELEOSTEI (sensu Patterson, 1973)Family ASPIDORHYNCHIDAE Nicholson &

Lydekker, 1889

Richmondichthys gen. nov.

DIAGNOSIS. Until further species are defined,the characters that define the species are alsothose that define the genus.

GENOTYPE. Richmondichthys sweeti (Etheridge Jnr &Smith Woodward, 1891).

Richmondichthys sweeti (Etheridge Jnr &Smith Woodward, 1891)

Richmondichthys sweeti (Etheridge Jnr & Smith Woodward,1891) pls 1-7.

Aspidorhynchus sp. Etheridge (partim), 1872; Jack &Etheridge Jnr, (partim), 1892.

Belonostomus sweeti Etheridge Jnr & Smith Woodward,1891; Jack & Etheridge Jnr, 1892.

Vinctifer sweeti, Brito, 1997.

HOLOTYPE. MVP (Museum of Victoria) 12988, partialskeleton including posterior of head and bulk of body,Hughenden, central Queensland.

FORMATION. Mostly from the ToolebucFormation, of Lower Cretaceous (Albian). Alsofrom the Allaru Mudstone, of Lower Cretaceous(Albian).

DIAGNOSIS. Very large, exceeding 1.6 metresin length. Neurocranial roof with markedlyasymmetrical fronto-parietals, dermopterotico-extrascapulars and post-temporals; rostral notextending beyond maxillary; premaxillary

without teeth and short, not extending anteriorlyas far as the dentalosplenial; circumorbital bonesare extremely well developed; maxillary withoutteeth, set well anterior to orbit; predentary verysmall, edentulate; gill filaments extremelyelongated; dentalosplenial deep anteriorly andvery deep posteriorly, lacking teeth; lateral linescales greatly deepened; all scales heavilycovered with ganoine, raised into heavy ridgesand tubercles; ornamented ganoine also coversthe outer bones of the head and is present on thelarger elements of the fin rays.

MATERIAL. QMF1764, scales, Hughenden, CQ;QMF1841, scales, Hughenden, CQ; QMF1842, scales,Hughenden, CQ; QMF2296, partial body, MarathonStation,EofRichmond,CQ;QMF2389, scales,Hughendendistrict, CQ; QMF2389, partial skeleton, no locality;QMF2390, partial skull and skeleton, Hughenden district,CQ; QMF2437, scales, nr Hughenden, CQ; QMF2582,partial skeleton, Lydia Downs Station, N of Nelia, CQ;QMF5651, partial skeleton including parts of skull andanterior of body, Dingading Station, nr McKinlay, at MR404304 McKinlay 1:250000 sheet, NWQ; QMF5660,partial skeleton, Dunraven Station, 48km NW ofHughenden, at Pelican Bore, CQ; QMF5661, partial body,Dingading Station, nr McKinlay, at por. 4, Par. Collins,NWQ; QMF5662, vertebrae, Hughenden, CQ; QMF5663,fragment with scales, Hughenden Station, Hughenden, CQ;QMF5664, fragment with scales, Hughenden Station,Hughenden, CQ; QMF5666, partial skeleton, Boree ParkStation, at MR 627413 Richmond 1:250000 sheet, CQ;QMF5667, fragment with ventral body scales, MeiraPaddock, Boree Park Station, about 12km NW ofRichmond, nr MR 622416 Richmond 1:250000 sheet, CQ;QMF5668, scales, Boree Park Station, at MR 627413Richmond1:250000sheet,CQ;QMF5669,partial skeleton,PubPaddock,BoreeParkStation,nrMR627413Richmond1:250000 sheet, CQ; QMF5670, fragment with vertebraeand scales, Pub Paddock, Boree Park Station, at MR 627413Richmond1:250000sheet,CQ;QMF5671,partial skeleton,Pub Paddock, Boree Park Station, nrMR 627413 Richmond1:250000sheet,CQ;QMF5672,partial skeleton,DingadingStation, McKinlay, at por. 4, Par. Collins, NWQ; QMF5673,partial body, 22km N of Springvale Station, SE of Boulia,NWQ; QMF5674, partial body, 8km WSW of MarathonStation homestead, E of Richmond, CQ; QMF5675, partialskull and body, including gill filaments, Dingading Station,nr McKinlay, at MR 406306 McKinlay 1:250000 sheet,NWQ; QMF7568, partial skeleton including parts of skullandanteriorofbody,MarathonStation,EofRichmond,CQ;QMF7668, partial skull, no locality; QMF10608,neurocranium, Warra Station, NWQ; QMF12706, partialbody, Stewart Creek, Dunraven Station, 3rd creek crossingfrom main road on track to Pelican Bore, CQ; QMF12856,neurocranium, no locality; QMF12904, partial body,Hughenden, CQ; QMF13412, neurocranium, SlashersCreek Station, NWQ; QMF13037, partial skeleton,Marathon Station, nr Richmond, CQ; QMF13413,neurocranium, Springvale Station, NWQ; QMF13711,partial skeleton, including partial skull and anterior of body,

522 MEMOIRS OF THE QUEENSLAND MUSEUM

Dunraven Station, Stewart Creek, unnamed tributary on Sside, downstream from junction with Soda Creek andupstream from Pelican Bore, NW of Hughenden, CQ;QMF13726, scales, Dunraven Station nr Hughenden, CQ;QMF13727, partial skeleton, Stewart Creek, upstream fromjunctionwithSodaCreek,DunravenStation,nrHughenden,CQ; QMF13728, partial skeleton, bank of unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF 13729, partial skeleton, StewartCreek upstream from Pelican Bore, Dunraven Station, nrHughenden, CQ; QMF13731, partial skeleton, StewartCreek downstream from Pelican Bore, Dunraven Station, nrHughenden, CQ; QMF13734, partial skull, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13744, partial skeleton, StewartCreek, upstream from junction with Soda Creek, DunravenStation, nr Hughenden, CQ; QMF13745, partial skull, bodyand scales, Stewart Creek, downstream from Pelican Bore,Dunraven Station, N of Hughenden, CQ; QMF13746,partial skeleton,StewartCreek,upstreamfromPelicanBore,Dunraven Station, nr Hughenden, CQ; QMF13747, partialskeleton, unnamed tributary of Stewart Creek, DunravenStation, nr Hughenden, CQ; QMF13748, partial skeleton,tributary of Stewart Creek, Dunraven Station, N ofHughenden, CQ; QMF13753, partial skeleton, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13767, partial skeleton, tributary ofStewart Creek, Dunraven Station, N of Hughenden, CQ;QMF13771, partial skeleton, unnamed tributary of StewartCreek, Dunraven Station, nr Hughenden, CQ; QMF13772,unnamed tributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13773, partial skeleton, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13774, partial skull, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13775, partial skeleton, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13776, partial skeleton, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13777, partial skeleton, unnamedtributary of Stewart Creek, Dunraven Station, nrHughenden, CQ; QMF13778, partial skeleton, DunravenStation,unnamed tributaryofStewartCreek,nrHughenden,CQ; QMF13779, partial skeleton, unnamed tributary ofStewart Creek, Dunraven Station, nr Hughenden, CQ;QMF13780, partial skeleton, unnamed tributary of StewartCreek, Dunraven Station, nr Hughenden, CQ; QMF13781,partial skeleton, unnamed tributary of Stewart Creek,DunravenStation,nrHughenden,CQ;QMF(unnumbered),partial skeleton, Rocky Waterhole, Flinders River, JuliaCreek at L398 (QM collection register); QMF13787,neurocranium, Dunraven Station, N of Hughenden, CQ;QMF13788, partial skeleton and scales, Stewart Creek,downstream from Pelican Bore, Dunraven Station, N ofHughenden, CQ; QMF13789, partial skeleton and scales,tributary of Stewart Creek, Dunraven Station, N ofHughenden, CQ; QMF13790, partial skull, Stewart Creek,upstream from Pelican Bore, Dunraven Station, N ofHughenden, CQ; QMF13791, partial skeleton and scales,tributary of Stewart Creek, Dunraven Station, N ofHughenden, CQ; QMF13793, partial skeleton, tributary of

Stewart Creek, Dunraven Station, N of Hughenden, CQ;QMF13794, partial skeleton, tributary of Stewart Creek,Dunraven Station, N of Hughenden, CQ; QMF13795,partial skeleton and scales, tributary of Stewart Creek,Dunraven Station, N of Hughenden, CQ; QMF13796,partial skeleton, tributary of Stewart Creek, DunravenStation, N of Hughenden, CQ; QMF14339, partial body,Boree Park, W of Richmond, CQ; QMF18040, partialskeleton, Marathon Station, nr Richmond, CQ; QMF18115,partial skull, Flinders River crossing, W of Marathon Stationhomestead, Allaru Mudstone, CQ; QMF18153, body andskull fragments, 1.4km S of Jacks Bore, Canary Station, SEof Boulia, NWQ; QMF15328, skull fragment, Pelican Borearea, Dunraven Station, CQ; QMF18218, partial skull andanterior of body, NE of Canary Station homestead, SE ofBoulia,NWQ;QMF18253,partialbody,2.6kmSofCanaryStation homestead, in lambing paddock, SE of Boulia,NWQ; QMF18295, skull and anterior of body, old Councilquarry, 5km S of Flinders River, Wof Richmond, CQ;QMF18603, partial skeleton, 2km E of Jacks Bore, CanaryStation,SEofBoulia,Toolebuc,NWQ;QMF18898,almostcomplete skull and post-cranial skeleton, 20km W ofRichmond, nr Old Richmond/ Maxwelton Highway, CQ;QMF25074, partial skull, Flinders River, at QM collectionlocality L815, Allaru Formation, CQ; QMF25077, partialskeleton, Flinders River at QM collection locality L815,Allaru Formation, CQ; QMF25331, body scales, CanaryStation, nr Boulia, NWQ; QMF41492, scales, Boree ParkStation, nr Richmond, CQ; QMF41493, partial skull, BoreePark Station, nr Richmond, CQ; QMF41494, partial skull,Boree Park, nr Richmond, CQ; GSQF12904 (GeologicalSurveyofQueenslandCollection), scales,Hughenden,CQ

DESCRIPTION. General. General body shape iselongate and sub-cylindrical, but much deeperthan broad. Richmondichthys was a very largefish, with preserved individuals exceeding 1.6min length and with fragments of even largerindividuals preserved. Body depth exceeded27cm. The body is deepest just posterior to thehead, gradually reducing in depth to the caudalpeduncle where the depth is about 25% ofmaximum depth. Table 1 (linked to Fig.1),provides measurements for the most complete ofthe R. sweeti specimens (QMF18898) compared

CRETACEOUS ASPIDORHYNCHID FISH 523

FIG. 1. Hypothetical aspidorhynchid teleost (from Brito,1997) illustrating parameters applied in Table 1.

with those for specimens of V. comptoni providedin Brito (1997).

The head is long and narrow. Premaxillaries areextended anteriorly but do not reach as farforward as the dentalosplenials, let alone thepredentary. The head represents approximatelyone-quarter the length of the fish. Its length ismore than twice its maximum depth (Figs 2-4).The quadrato-mandibular articulation is situatedanterior to the level of the front of the orbit (Fig. 3).

The scales are heavily covered with ganoine.Those along the flanks, especially anteriorly, aremuch deeper than dorsal and ventral scales. Atotal of 82 rows of scales are present inQMF18898 (Fig. 5) between the posterior borderof the supracleithrum and the posterior of thecaudal peduncle. As defined in the scale formulaoutlined by Westoll (1944) and applied by Brito(1997), the pelvic, anal, dorsal and caudal fins arelocated along the body as follow:

__________61______

37 55 69

It is likely that the pelvic, anal and dorsal finswere reclining backwards and that the caudal finwas relatively large and forked as in otheraspidorhynchids.

Cranium. The endocranium in Richmondichthysis well ossified in more mature individuals (Figs6-8). It comprises a bony box with anterior andposterior moieties united by the parasphenoidbelow and the frontalo-parietal above, withcontiguous elements firmly sutured and withsuch sutures variably tending to disappear withage, similar to those in other members of theAspidorhynchidae (Brito, 1992).

The following measurements have been derivedmainly from QMF7568.

Length, from the anterior of the nasal fossa tothe posterior border of the post-temporal,19.4cm; from the anterior of the nasal fossa to theposterior border of the basioccipital (lateralview), 14.3cm. Breadth, at the level of thepost-orbital processes, 5.5cm. Depth, at theanterior of the basisphenoid, 3.1cm.

These measurements allow a broad comparisonto be made with similar measurements inVinctifer comptoni especially as these relate toproportions calculated by Brito (1992) for thatspecies. The endocranium in Richmondichthys isvery long, being 6.2� as long posterior to thenasal fossa as the maximum depth (c.f. 4.5� in V.comptoni). The nasal fossa is relatively short,representing 6% of the endocranial length inlateral view (20% in V. comptoni). The orbit iscomparatively large (35.6% of the same measurec.f. 32% in V. comptoni) while the post-orbitalregion is very large, being 57.6% of the lateralendocranial length (48% in V. comptoni).

Ethmoid Region. Only the posterior of the ethmoidregion is exposed in one individual, QMF568. Itis well ossified and forms the floor and posteriorwall of the nasal fossa. Amedian septum separatesthe fossa, while its upper extent is limited by theanterior of the frontals and the posterior of therostral; the anterior of the nasal fossa appears tobe contained by the ethmoid itself.

The posterior of the lateral ethmoid bears alarge, horizontal ridge directed posteromediallytowards the orbitosphenoid, above the para-sphenoid, presumably supporting the olfactorynerve (I) and capping the anterior myodome. Theforamen for the orbitosphenoid vein is present atthe base of the large ridge and there is an artic-ulation surface anteromedially on the ethmoidbase for the palatine. Anteriorly, the ethmoidregion encircles a posterior extension of thepremaxillaries.

Orbito-Temporal and Otic Region. The posteriorsurface of the orbit is penetrated by a large numberof foramina for nerves and blood vessels to themandible and the anterior of the cranium.

The orbitosphenoid is fully ossified in thoseindividuals in which it is visible (QMF7568 andQMF13412). It comprises the posterodorsal roofof the orbital cavity, fanning anteriorly and wellseparated from the posteromedial processes ofthe ethmoid region. It is sutured laterally to thepterosphenoids. In anterior view, the orbito-sphenoid extends a medial plate anteriorly toform the base of the canal for the passage of the


1 2 3 4 5 6 7 8 9

R. sweeti (QMF18898) - 147.9 34.2 35.1 14.5 118.2 114.1 94.4 4.6

V. comptoni (USU 49) 75.0 70.0 19.0 13.0 8.0 55.0 54.6 47.0 1.4

V. comptoni (USU 07) 12.0 11.6 5.0 1.6 0.9 8.7 8.4 - -

V. comptoni (FMNH PF 13486) 27.0 26.0 8.8 - 1.5 21.5 21.3 - -

TABLE 1. Comparative morphometric values (cm). (See Brito, 1997 for information on V. comptoni specimens)

82

olfactory nerve (I) and the roof of the largeopening for the optic nerves (II). There is noevidence of the presence of a foramen for thepassage of the anterior cerebral vein.

The pterosphenoid forms the posterolateralpart of the posterior orbital wall. It is supporteddorsally by the frontal and extends to join withthe autosphenotic laterally and with the base anddorsal wing of the basisphenoid. It is excludedfrom lateral contact with the prootic by theautosphenotic and the parasphenoid. There is aprominent bony crest forming a pterosphenoidpeduncle, subparallel to the ventrolateral rim ofthe opening for the orbital nerve. Medially andfloored by the pterosphenoid peduncle is arelatively large foramen for nerve III, close to thesuture with the wing of the basisphenoid. Close tothe internal border of the pterosphenoid peduncleand just above the basisphenoid suture is aforamen interpreted as that for nerve IV. Thisappears to be separated fairly widely fromanother small foramen near the lateral extent ofthe pterosphenoid peduncle, possibly for theanterior cerebral vein. The lateral extension ofthe peduncle surrounds and provides the rim ofthe tigeminofacial orifice and anterodorsally tothis is penetrated by nerve V.

The basisphenoid has a stalk that meets thedorsal surface of the parasphenoid and slopesposterodorsally, separating the left and rightmoieties of the posterior myodome. The base of

the basisphenoid has dorsolateral extensions thatform the floor and ventrolateral walls of the largeorifice for the passage of the optic nerves(II) andthat meet a moderately large process of thepterosphenoid.

The autosphenotic is relatively small andtriangular and caps the lateral extent of theorbitotemporal and otic regions. The dorsal faceis in contact with the cranial roof in the region ofthe dermosphenotic but is not united with it. Theanterior face is slightly curved, forming theposterodorsal extent of the orbit with both thepterosphenoid and the lateral process of the para-sphenoid. Posterolaterally, the autosphenotic


FIG. 3. Richmondichthys sweeti (Etheridge Jnr & SmithWoodward, 1891): Reconstruction of the head inlateral view, based primarily on QMF13711 andQMF18898. Scale bar represents 5cm.

FIG. 2. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891), QMF13711, lateral view of right sideof head. Scale bar = 5cm.

meets the prootic and bears a large depressionthat represents the anterior extent of the articularfossa for the hyomandibular.

The prootic is a large, complex bone that formsthe bulk of the floor and walls of the neuro-cranium, reaching from the back of the postorbitalprocesses to the cranial roof and the lateral wallsand back of the posterior myodome. In lateralview, the prootic extends to meet the basioccipital,the suture with which is sometimes partially orcompletely obscured and difficult to identify.Similarly, the suture separating the prootic andopisthotic is not able to be identified in availablespecimens.

In lateral view, the otic region carries the bulkof the large, horizontal, hyomandibular fossa,which extends from the back of the postorbitalprocess below the cranial roof to the abutment ofthe autopterotic. The fossa is slightly hour-glassshaped. Immediately below the hyomandibularfossa are several well developed and largeforamina – the large opening for the passage of thejugular vein into the trigemino-facial chamber; theforamen for the jugulohyomandibular trunk ofthe facial nerve, midway along the prootic; theslightly smaller foramen for the glossopharyngealnerve (IX), situated near the basioccipital suturewithin the jugular depression; and the largerforamen for the passage of the vagus nerve (X),opening at the dorsal end of the otico-occipital

suture. The depression for the jugular vein is verydistinct, especially in the area of the foramen forthe jugulohyomandibular trunk of nerve VII. Theextracranial trigemino-facial chamber opensbackwards through the large oriface or thepassage of the jugular vein. The space alsoappears to provide a communication with thecranial cavity for the profundus, trigeminal (V)and facial (VII) nerves. The orbital opening of thetrigemino-facial chamber is divided by thepedicule of the pterosphenoid with the medianopening accommodating the ophthalmic rami ofthe trigeminal and facial nerves (V + VII opht)and a lateral opening possibly for the trigeminaland facial nerves and for the jugular vein andorbital artery. The profundus nerve appears toproceed through a foramen more anterodorsally,near the suture between the pterosphenoid andthe orbitosphenoid, close to a foramen believedfor the median cerebral vein. The ventral borderof the prootic, immediately behind the para-sphenoid process contributes to the articulationfor the first infrapharyngobrachial, although thebulk of the articulation is on the parasphenoidprocess itself. The articulation of the infra-pharyngobrachial has not been observed in anyspecimen.

The opisthotic is generally fused to the prooticand the suture is not easily observed. It extendsbackwards from behind and above the large


FIG. 4. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891), QMF13711, lateral view of left side ofhead. Scale bar = 5cm.

foramen for the glossopharyngial nerve (IX) andjust reaches that for the vagus nerve (X). Thebone was much smaller than the prootic.

The autopterotic is very small, developedabove the back of the opisthotic and lateral to theeven smaller epipterotic. It has a well defined androbust process directed posteriorly to be suturedwith the intercalar process. The autosphenotic istotally independent of the dermal bones of thecranium.

The intercalar is prominent, extending posteriorlyas a large, flattened and vertically expandingprocess from the junction of the opisthotic andautosphenotic. It is fused laterally to the processof the autosphenotic and extends well beyond thevertebra fused to the basioccipital. It is partiallycovered by the extrascapular and the post-temporal and bears a large foramen anteriorly,above the suture with the autopterotic.

Occipital Region. The bony mass of the occipitalregion is limited anteriorly by the suture with theprootic (the otico-occipital fissure), to include thewhole of the foramen for nerve X and posteriorlyby the fusion of the basioccipital and the firstvertebra.

The basioccipital is defined laterally by welldefined sutures. It comprises the ventral andlateral margins of the occipital region. Theventral margin extends slightly anterior to theforamen for the glossopharyngeal nerve (IX). It isunited with the prootic and opisthotic by anoblique suture. The basioccipital has not, as yet,been exposed in posterior view. Posterodorsally,it meets the exoccipital. Occasionally, a smallforamen is present above and towards the back ofthe parasphenoid for the passage of the occipital

artery. The first vertebra is firmly fused to thebasioccipital and forms part of the endocranium.

The exoccipital contributes to the dorsolateralpart of the occipital region and to the posteriorsurface. It extends from just above and behind theforamen for the vagus nerve (X) and is sutureddeeply with the basioccipital anteroventrally andposteriorly fused with the first vertebra. Eachexoccipital is extended posterodorsally into anarch, comparable with that of the first vertebraand deeply sutured to it.

The epiotic forms the posterior margins of thepost-temporal fossa. It is positioned between theexoccipital and the posterior process of theintercalar and contributes to the posterodorsalborder of the endocranial roof. It is deeply suturedto the exoccipital posterodorsally and is penetratedby a number of foramina, the largest of which isinterpreted to be for the posterior cerebral vein.

The supraoccipital is largely hidden by theextrascapular in most specimens. It is a smallbone, firmly fused with the epiotic and has a pairof posterodorsal processes that overlap the archstructure of the exoccipitals.

Dermal Bones of the Anterior Aspect of theEndocranium. The parasphenoid comprises anarrow veneer of bone under the neurocranium. Itis very long anteroposteriorly, extending fromnear the front of the ethmoid region to justposterior to the level of the foramen for the vagusnerve (X). It appears to contribute medially to theposterior of the rostral tubes and is anteriorlybroadened and flattened between the ethmoids. Itdoes not appear to bifurcate in this region toenvelop the vomer and its relationship with thevomer has not been observed. The parasphenoidis slender below the orbit, flattened laterally and


FIG. 5. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891), QMF18898, almost completeskeleton from right side. Scale bar = 10cm.

dorsally crested. It then presents a concavitytowards the back of the orbital cavity that curvesdorsally to about the level of the postorbitalprocesses before extending posteriorly andflattening dorsoventrally below the otico-occipital region.

A wing-like process is developed on each sideof the parasphenoid below the postorbitalprocesses. These are directed ventrolaterally tobelow the autosphenotics, with the anteriormargin of the parasphenoid process forming theborder of the posterior myodome and theposterior margin scalloped out to contribute tothe foramen for the passage of the internal carotidartery. Another foramen is present in each wing,well beyond the midline and these are believedfor the pseudobranchial efferent artery.

The parasphenoid is totally devoid of teeth andlacks any trace of a basipterygoid process.

The vomer has not been observed in any specimenyet found. It is possible that it is present within theanterior broadening of the parasphenoid in

F7568. However, no sutures are evident and thereis no evidence for any vomerine teeth.

Rostral Region. The premaxillaries comprise themajor elements of the anterior of the rostral region.They are ornamented with fine, longitudinalstriae, where exposed. Posteriorly, the bone isinserted deeply below other dermal bones andforms the rostral tube that is fitted into theendocranial ethmoid region. Anteriorly, the pre-maxillaries are not greatly tapered and terminateposterior to the junction of the dentalosplenialand the predentary. Ventrally, it is believed thatthe premaxillaries are underlain by theparasphenoid and possibly the vomer; posteriorly,each is encased by the rostral above and thedorsal margin of the maxillary. Contact with thenasal does not appear to occur. The premaxillariesare edentulate where they have been observed.

The rostral is a large bone, transversely convexand much longer than wide, covering the posteriorof the premaxillaries and overlapping the frontals.It is ornamented by ridges of ganoine.


FIG. 6. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891) neurocranium. A, lateral view of rightside, QMF7568, � 0.65; B, ventral view, QMF13412, � 1.75.

The nasal is a small bone, limited dorsally bythe rostral and appears to be limited anteriorlyand posteroventrally by the first infraorbital andposterodorsally by the supraorbital. Associationof the infraorbital canal with the nasal has notbeen observed in any of the available specimens.The anterior of the supraorbital canal traversesthe nasal.

Cranial Roof. Apart from the rostral region,the cranial roof comprises a series of bonesidentified as the fronto-parietals, dermopterotico-extrascapulars and the post-temporals.

The fronto-parietals comprise the largest bonesof the cranial roof. They extend from the rostralsto the dermosphenotico-extrascapulars, justabove the front of the opercular. In dorsal view,the width is almost constant from front to back,although there is a slight broadening above therear of the orbit. The bones are markedlyasymmetrical, with the mediodorsal suturedeeply interdigitated and set mainly to the left butoccasionally to the right of the midline. Thefrontals have usually been firmly welded to theparietals but sutures with the latter are sometimes

visible. The surfaces areheavily ornamented withridges and tubercles of dentine,generally radiating anteriorly,posteriorly and medially frompoints on the frontals, abovethe autosphenotics. Laterally,the fronto-par ie ta ls areshallowly grooved to accom-modate the upper margins ofthe uppermost postorbital andthe supraorbitals.

The dermopterotico-extrascapulars comprise a pairof gently arched bones that,like the fronto-parietals aremarkedly asymmetrical andthat have a well-defined medio-dorsal suture. Variable ridgesand tubercles of ganoineradiate on the surface fromanterolateral loci. Lateralgrooves accommodate theupper margin of part of thedermosphenotic.

The post-temporals aresimilar to the dermopterotico-extrascapulars and comprise apair of markedly asymmetrical,gently arched bones that areanteriorly overlain by the

extrascapulars and that meet one another along adeeply overlapping and broadly undulatingmediodorsal suture. Ornamentation is of strongridges and tubercles of ganoine radiating fromloci mid-way along the lateral margins.

Cheek. The orbit is surrounded by the infraorbitalseries and by the dermosphenotic and supraorbital.Two large postorbital plates and the preoperculumcomplete the cheek bones. The cheek bones arelargely unornamented by ridges and tubercles ofganoine except for the supraorbital and dermo-sphenotic where coarse ornamentation is presentin rows paralleling the dorsal margins. Thesclerotic ring appears to comprise no more thantwo plates.

The dorsal margins of the cheek bones fit into agroove along the dorsolateral margin of theneurocranium, forming a hinge along which thecheek bones can be rotated outwards.

The infraorbital series comprises five bones,generally increasing in size from a smallrectangular element posterior to the orbit, aroundthe ventral and anterior rim of the orbit. The large,


FIG. 7. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891):Reconstructed neurocranium based primarily on QMF7568, QMF13711and QMF13412. A, dorsal view; B, lateral view; and C, ventral view. Scalebar = 5cm.

uppermost anterior element reaches well in frontof the nasal and has broad contact with themaxillary. The second infraorbital is equally largeand also has broad contact with the maxillary.Remaining infraorbitals (Io 3-5) complete theventral and posterior margins of the orbit andbroadly contact the postorbitals.

The supraorbital is a robust element approx-imately twice as long as it is high. It forms theanterodorsal margin of the orbit and abuts thefrontal, reaching anteriorly to the nasal and therostral.

The dermosphenotic is very long and robust,extending posteriorly from its suture with thesupraorbital above the middle of the orbit to apoint above the dorsal extremity of the pre-operculum. It has a long abutment with the frontaland the dermopterotic.

The postorbitals comprise two very largeelements that cover the anterior margin of thepreoperculum. The ventral element makes broadcontact with the maxillary and meets Io 2-4.

The preoperculum is an extremely large,triangular bone with the posteroventral angleapproximately 90º. The preopercular canal hasnot been observed in any specimen.

Opercular Series. No interoperculum is present.The operculum is a large, heavy element, subovate

in outline with a slightly indented ventral margin,

a straight anterior margin and near right angledanteroventrally. The facet for the articulation withthe hyomandibular is situated anterodorsally. Thesurface is heavily ornamented with numerous,irregular and concentric ganoine ridges andtubercle rows, centred approximately above thehyomandibular facet.

The suboperculum is a moderately large bone,filling the space between the preoperculum andthe operculum and ventral to the latter. It is quadrant-shaped and its surface is heavily ornamented withlow, irregular, concentric ganoine ridges andtubercles around a centre near the anterodorsalextremity. Areas overlapped by other bones lackganoine.

Some 13 branchiostegal rays are present belowthe posteroventral angle of the mandible.

No gular plate is present.

Upper Jaw. The maxillary is a large, boomerang-shaped bone that is much more developed in itsposterior part than anteriorly. It is positionedconsiderably in advance of the orbit with theposteroventral margin remaining well anterior tothe anterior of the orbit and not extending to thepreoperculum. The posterior portion is thin andbroadly covers the posterodorsal area of themandible. The anterior presents a weak dorsalprocess that articulates with the premaxillary. Noteeth are present. The bone is coated with largely


FIG. 8. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891) neurocranium. A,C, dorsal andposterior views of QMF10608, � 1.4; B, dorsal view of QMF7568, � 0.45.

featureless ganoine extending backwards anddorsally from the oral margin.

No supramaxillary is present.

Lower Jaw. A predentary is present as a medialelement at the extreme anterior of the mandibles.It is edentate and is a tiny bone deeper than long.The oral border is much shorter than the depth ofthe bone.

The mandible has a relatively elevated andvery deep symphysis, united in its upper moietywith the predentary by a near vertical suture. Thecoronoid process is virtually non-existent and iscovered by the maxillary in most specimens. Thelateral face is largely formed by the dentalo-splenial. The angular is relatively large but isalmost completely covered by the posterior of themaxillary. The articular facet for the quadrate isformed at the base of the coronoid process by theangular and retroarticular on the upper surface ofthe mandible, at the base of the coronoid process.A short posterior process present behind thearticular facet is formed by the articular and theretroarticular. The dentalosplenial and the angularare crossed longitudinally by the mandibular canalwhich has surface expression on the dentalosplenialas a shallow groove towards the ventrolateralmargin. Ventrolaterally and around the anteriorborder, the mandible is heavily ornamented withganoine ridges and tubercles, generally arrangedlongitudinally. The remainder of the lateralsurface is coated with smooth ganoine.

The mandible is edentate.

Hyoid Arch Area. The mandibular-neurocranialconnection is through the hyomandibular and thequadrate There is no evidence for the presence ofa symplectic.

The hyomandibular is upright with the articularfacet for the junction with the neurocraniumelongate and near horizontal and with its distalextremity slightly curved anteriorly. The lateralsurface is strengthened by a prominent ridge thatseparates a deep anterior portion that appears toabut the metapterygoid. The posterior bordercarries a prominent opercular process towards itstop. The body of the bone is penetrated by thelarge foramen providing passage for thehyomandibular trunk of the facial nerve. Thedistal extremity has not been well exposed in anyspecimen but apparently provides broad contactwith the quadrate anteroventrally and with theproximal ceratohyal towards the back. There isno evidence for the presence of an interhyal andthe distal ceratohyal, hypohyal and basihyal havenot been exposed in any of the available specimens.

The quadrate is a large, triangular bone but thedorsal extremity is not exposed in any of theavailable material. Anterodorsally, the quadrateoverlies the ectopterygoid and is assumed tocontact the metapterygoid dorsally. It also hasbroad contact with the hyomandibular dorsally.The articular condyle is oriented ventrally andanteriorly.

The autopalatine is almost completely obscuredin all specimens, as are the metapterygoid andentopterygoid. The ectopterygoid is visible onlyposteriorly, where its ventral border is almosthorizontal and the whole bone is essentiallystraight and tapering anteriorly. The bone isedentate.

The branchial arch is imperfectly preserved.Each element of the gill arches bears verynumerous, extremely elongated gill filamentsdirected away from the arch (Fig. 9). Slightlymore robust and elongated gill rakers occuranteromesially.

Postcranial Skeleton. The vertebral column hasnot been completely exposed in any specimen,making it impossible to indicate the number ofindividual ver tebrae. Each centrum isamphicoelous and ovate in anterior view, beingslightly higher than long. Each bears a smallcentral foramen, the remnant of the notochord.The centrum is otherwise entirely ossified andonly very slightly constricted longitudinally.Length of each centrum is about equal to thewidth. The lateral surface is smooth (Fig. 9). Insection, the centrum possesses very fine radiatinglaminae of bone, separated by unossified areas.Neural arches are attached and bear prezygopo-physes and postzygopophyses and supportelongate, posteriorly directed neural spines, atleast anteriorly in the body. In this area, suchspines consist of separate lateral elements.Anterior neural arches are very elongate,occupying the entire length of each centrum ,with the spines emerging above the middle of thecentrum. Very short epineural spines are presentanteriorly, fused firmly at the base of each neuralspine. Anterior parapophyses are fused to thecentra ventrolaterally. In more posterior vertebrae,haemal arches appear slender and at least in someindividuals, both these and the neural arches arenot fused to the centrum. The ventral surface ofanterior vertebrae bears a median, longitudinalridge separated from the parapophyses byshallow depressions.

The pectoral girdle is only partially exposed inall specimens. The supracleithrum extends from



FIG. 9. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward, 1891). A, gill elements, QMF5675, � 0.7; B,portion of vertebral column, QMF7568, � 1.6.

near the dorsal limit of the convexupper margin of the operculumventrally to about one-half waydown its posterior margin. Exposedportions are ornamented withirregular ridges and tubercles ofganoine, arranged parallel to thedorsoventral axis of the bone. Thecleithrum is a much larger element,overlapped dorsally by the supra-cleithrum and extending aroundand under the posteroventral andventral margins of the operculumand suboperculum. It is markedlyconcave anteriorly and exposedportions are ornamented withganoine. The scapula and coracoidare almost completely obscuredbut the former is facetted to carrythe pectoral fin. Other bones of thepectoral girdle are unknown.

Remains of the bases of all finsare preserved in only one specimen,QMF18898, and the formula forthe fin positions above have beenbased upon this. Some exposedbasal elements of all fins appear to have beencoated with ganoine.

The pectoral fin appears to have seven rays,with the first smaller than the second, the latterbeing the largest ray in the series. At leastproximally, the rays bear ornamentation ofganoine. As the rays broaden distally, thelongitudinally orientated ganoine ridges areincreased by insertion of additional ridges. Thefin is moderately long, at least equal to two-thirdsthe depth of the anterior expanded flank scales.The pelvic, anal, dorsal and caudal fins areknown from only remains of their bases.

Scales. The scales are heavy, strong andconspicuous and are the most commonlypreserved parts of the skeleton (Figs 5,10). Theyare thickly ornamented with ganoine pits, lowridges and tubercles. Anterior and mid-body

scales of the median flank series are very large.Individual lateral line scales in large specimensare up to 14.5cm deep and 2.3cm long. Table 2details the depths of flank scales along the body inQMF18898.

Each median flank scale is slightly laterallyconvex with the convexity increasing dorsally.The posteroventral border is rounded. Theventral border, while generally convex, has abroad mesial process. The posterior margin isfinely and irregularly serrate where the lowridges of ganoine project. The upper margin ispointed, with the apex posterior to the apex of thescale. The leading edge is smooth. A heavyganoine ridge runs down the axis of the scale andthis is usually paralleled by a second, less welldefined ridge, just anterior to it.

The major ridge is often ornamented withtubercles, while the other ridge sometimesdegenerates to a series of tubercles only. Theanterior ganoine is smooth or only very slightlypitted or tuberculate. Posterior to the main ridge,irregular ganoine ridges run generally antero-posteriorly, often bifurcating or reuniting butgive a general impression of subparallel,longitudinal ornamentation. Ornamentation isheavier dorsally. The lateral line is marked by aheavier, longitudinal plication, close to the dorsallimit of the scale.


FIG. 10. Richmondichthys sweeti (Etheridge Jnr & Smith Woodward,1891) mid-body scales with dorsal wall uppermost. A, GSQF12904;B, reconstruction (by T. Lees); both � 0.3.

CharacterNear Head(Row 4)

AbovePelvic Fin

AboveAnal Fin

Front ofCaudal Fin

A 5.0 2.7 1.0 0.8

B 10.6 11.6 7.9 5.6

C 21.4 22.1 16.6 10.1

TABLE 2. Depth of flank scales (cm) where: Ameasures scale immediately ventral to lateral linescale; B measures lateral line scale; and C measuresmaximum observed body depth.

Ventral to the main flank scales are at least fourand possibly up to six rows of progressivelysmaller scales. In large individuals, anteriorly theuppermost are up to 5cm deep. The next scalesrow are up to 1.8cm deep, those in the third roware up to 1.5cm deep, while in the fourth row theyapproach 1cm deep. The uppermost of theseventral scales has very similar structure andornamentation to the main flank scales. Lowerscales generally have little or no ornamentation,other than traces of the median ridge and aresubovate in shape but have a distinct pegarranged axially along the dorsal margin.

Dorsal scales above the main flank scales alsoappear to be in no less than four rows anteriorly.Unlike the ventral series where scales arearranged in near vertical rows, those above themain flank scales are angled anteriorly. Inoutline, scales of the first row are similar to themain flank scales but have a ventral emarginationrather than a peg. The median ridge is less stronglydefined but minor ornamentation is similar. Inlarge specimens, the lowermost dorsal scale is upto 2.8cm deep. Scales above this row are insertedto leave a broadly convex posterior margin butare otherwise rhomboidal in shape. Little traceremains of a median ridge and ornamentationconsists of anteroposteriorly arranged , irregularganoine ridges. Occasional heavy tubercles arepresent. In depth, the dorsal scales decrease insize dorsally and in large individuals measure upto 2cm, 1.9cm and 1.7cm within each row.

More posteriorly along the body, depth of thelarge flank scales gradually decreases and nearthe base of the caudal fin, all scales are of asimilar size, are rhomboidal and are arranged inan imbricated pattern. Ornamentation has been

reduced to a posterior, longitudinal keel withsubparallel minor ridges. Up to 82 rows of scalesare present in the flank series.

DISCUSSION

Brito (1997) has undertaken a major revision ofthe Family Aspidorhynchidae and referred theAustralian material, previously ascribed toBelonostomus sweeti, to the genus Vinctifer.Fragmentary aspidorhynchid remains fromCretaceous sediments at Hughenden Station incentral western Queensland and referred byEtheridge (1872) to Aspidorhynchus sp. includedparts of large body scales that are ornamentedwith ridges and tubercles of ganoine. This materialwas referred to the species Belonostomus sweetiby Jack and Etheridge Jnr (1892). Clearly, thismaterial is not referable to Aspidorhynchus,which is shown by Brito (1997) to lack ganoineon its scales. Similarly, it is not referable to eitherBelonostomus or Vinctifer both of which haveunornamented ganoine on their principal andother body scales. However, rugosity may bepresent on the scales in some V. comptoni, asdescribed by Jordan (1921). The Hughendenmaterial is here referred to the new genus,Richmondichthys, although non-diagnosticspecimens can only be regarded more generallyas undetermined aspidorhynchids. Table 3 providesa comparison of major morphological characterswithin the genera of the family, based on thosefeatures that are present in all of them. Figure 11compares the heads of the aspidorhynchids.

In many of the earlier reconstructions of V.comptoni, the extent of the premaxillary spinewas not recognized e.g., in that illustrated inJordan (1921). The retracted nature of this featurein R.sweeti might thus be supposed to reflect a


Characters Richmondichthys Vinctifer Belonostomus Aspidorhynchus

Premaxillary teeth Absent Absent Present Well developed

Maxillary teeth Absent Present Present Present

Supramaxillary Absent Absent Present Present

Maxillary Very expanded Large Slender Slender

Premaxillary Short Attenuated Very attenuated Attenuated

Neurocranium Fused Fused Fused Unfused

Parasphenoid Edentulate Edentulate Toothed Toothed

Anterior infraorbitals Much expanded Unexpanded Unexpanded Unexpanded

Predentary Minute Small Very attenuated Small

Lateral line scales Very deep Deep Somewhat deep Shallow

Scale ganoine Very ornamented Unornamented Unornamented Absent

TABLE 3. Comparison of Aspidorhynchid genera. Information on Vinctifer, Belonostomus and Aspidorhynchusis based on revised diagnoses and descriptions in Brito (1997).

similar accident of preservation, with anattenuated spine broken off and lost duringpreservation. Close examination of the tips of thepremaxillaries in QMF18898 shows that thisspecimen presents the entire extent of the spineand that the termination of this structure isposterior to the anterior extent of the lower jaw.

In ascribing B. sweeti to Vinctifer, Brito (1997)believed the species to be close to but much largerthan the type species, V. comptoni from theAlbian Santana Formation, Jardim, Ceara, Brasil.Temporal and geographical distribution of V.comptoni is recorded by Brito (1997) as alsobeing from the Santana of the Araripe Basin, theAptian/Albian Codo Formation of the ParnaibaBasin, the Aptian Muribeca and Albian RiachueloFormations of the Sergipe and Alagoas Basins andin the Aptian Apon Formation of Venezuela andthe Albian Morelos Formation of Tepexi deRodriguez, Puebla, Mexico.

Apart from V. comptoni, to which Brito (1997)referred the recently described V. punctatusSantos,1985 from the Aptian/Albian MuribecaFormation in the State of Alagoas, Brasil, anumber of other species of Vinctifer have beenrecognised, namely V. longirostris Santos, 1990and V. araripensis Santos, 1994 from theBrasilian Aptian Marizal Formation in theTucano Basin and the Albian Santana Formationin the Araripe Basin respectively. Like V. comptoni,these species are quite distinct from the Australianmaterial here referred to the new genusRichmondichthys.

A heavily ossified and fused neurocraniumfrom the late Campanian of Patagonia, illustratedby Brito (1997) could relate to either V. comptonior R. sweeti but is too incomplete to enable itsspecific identity to be resolved with any certainty.Predentaries and isolated scales that are muchdeeper than long are recorded from the BarremianMissao Velha Formation of the Chapada doAraripe and identified as Vinctifer by Brito etal.(1994). This material appears to lack closeaffinity with Richmondichthys.

Taverne (1969) referred the partial posterior ofa body of an aspidorhynchid from the Cretaceousof Equatorial Guinea to Belonostomus; thismaterial has very deep lateral line scalescompared with those immediately above andbelow them, suggesting to Brito (1997) thematerial is more likely to be referable to Vinctifer,supporting a view taken earlier by Maisey(1991). It is unlikely this material is more closelyrelated to R. sweeti. Similarly, the specimen from

the Jurassic of Antarctica, illustrated by Brito(1997, fig. 28) appears to be more appropriatelyassigned to Vinctifer as suggested by him. It hadbeen identified previously as Aspidorhynchus byRichter & Thomson (1989).

It thus appears that Richmondichthys is knownonly with certainty from the Albian of northcentral Queensland, Australia. On the other hand,Vinctifer probably existed widely throughoutGondwanaland from South America, Africa andAntarctica but, as yet, has not been recorded fromAustralia.

Day et al. (1983) indicate that, during theAlbian, deposition in the northern part of theEromanga Basin in central Queensland took placein restricted marine and lagoonal environments,with limited communication with the sea in theCarpentaria Basin to the north. The northern


FIG. 11. Comparison of reconstructed heads ofaspidorhynchids. A, Aspidorhynchus acutirostris(Blainville, 1818); B, Belonostomus tenuirostris(Agassiz, 1833); C, Vinctifer comptoni (Agassiz,1841); and D, Richmondichthys sweeti (Etheridge Jnr& Smith Woodward, 1891). A,B and C from Brito(1997). Scale bars = 1cm.

seaway reestablished across the Euroka Arch inlate Albian times and was marked by thedeposition of the interbedded black shale andlimestone of the Toolebuc Formation. Oil shaledeposits of this formation indicate specialisedenvironmental conditions which favoured thegrowth and preservation of organic remains.These conditions were terminated by continuedtransgression and the succeeding Allaru Mudstonerepresents normal marine deposition. Sediment-ation in the Eromanga Basin ended with theregressive cycle in late Albian time as the seawithdrew into the Carpentaria Basin.

Richmondichthys was well equipped throughthe defensive nature of its heavily armouredscales and dermal bones to co-exist with a rangeof predatory reptilian, teleost and selachiancontemporaries. Lack of teeth and the weight ofthe skeletal elements point to an incapacity tomove quickly either to capture food or to escapepredators. The organisation of the cheek bonesand their ‘hinging’ along the length of theneurocranium, together with the extreme lengthof the gill rakers support the view that R. sweetiwas a filter feeder, either gulping to ingest food orwidely opening its jaws and ballooning its cheekswhilst moving slowly through plankton swarms.Large specimens predominate amongst thosepreserved and the species was one of the mostcommon in Queensland’s Lower Cretaceous.

ACKNOWLEDGEMENTS

The author wishes to acknowledge the con-tribution made to this paper in an early draft andin the preparation of several of the figures by MsTempe Lees (now Mrs J. Thane).

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