Zoolo~icnScripta. V d . IN. NO. 2. pp. 31 1-319. IVNY Printed in Grcat Britain

Acregoliathidae (Osteichthyes, Teleostei), a new family of fishes from the Cenozoic of Acre State, Brazil

MARTHA RICHTER . ~ l t ~ ~ / i i d 3 Mci! IYHX

Kichtcr. M. IWY. Acrcgoliathidac (Ostcichthycs. 'l'clcostci). il new hmily o f fishes from the Cenozoic of Acn. State. Brxzil.-ZtmI. Srr. 18: 31 1-319.

A new fossil fish family (Acrcgoliathidac) with only one known species (Ac~n~~ti l i i i r l i i t l~ i~~rrrr ic~i i~c~i . ct sp.n.) isdcscrilrcd. 'I'hc nintcrial consists ofliirgc SciiIcS coming from the Plio-Pleistocene of Acre State. Northern ljrirsil. Studies involving X-ray riidiogriiph. SLM and opticiil microscopic mcthods dcnionstrstcd thc peculiarity o f the new 111iltcrii1l. whose affinities with' tho clilssicnl fish scale models ilrc hilrdly evident. 'I'hc scales o f A. riiiicii iirc n)und. with large exposed iind cnilrcdtlcd i lrcils. They hciir concentric circuli ;ind the posterior field is covered with many Irycrs o f LI gliissy ilnd hircfriiigcnt tissue. Two hony layers iirc clcilrly tlistinguish;iblc: the hiisill isopcdin mil. ahovc. an important cell-rmntaining spongiosa (protohuvcrsiaii hone tissue). The affinities o f the fossil with both s;inr)ptcrygiin and actinoplcryginn fishes arc diwusscd and the Acrcgoliiithidac arc wnsidcwd to hc tclcostcan fishes o f unwrtain systcmiitic rclationships with other fiimilicsorodcrs of this suhdivision.

Mariliu Hic.litc.r. Miiscii dc < Fnciii.v. I'oiitiJkiti lJniwr.vihdc <*uitilicci dti Hi11 (iniiidc clr, Siil. A,.. lpiniiigti. M I . 4, WMZi) I'iir~ci Alcgrc. 1i.S. 13nc:il.

Introduction

This paper deals with further material from thc collcction of fossil fish remains gathered in Acre State, Northcrn Brazil (Fig. 1). the description of which was begun by Richter (1984). The fossiliferous outcrop, called 'Lula', is situated along both sides of a road embankment, 8 km from the left bank of thc river Caete, in Sena Madurcira County (Fig. 2). The fossils were found throughout the somcwhat consolidated sedimentary rocks (Domning 1977). A previous discovery of fossil fish remains from the Cenozoic of Acre was rcported by Santos (1983). who describcd a dental plate of Lepidosiren, and by Taverne (1979). who commented upon some fish scales herein ascribed to a new genus.

Materials and methods

The present study was carried out at the Swedish Museum of Naturul History (SMNH). Stockholm. the Muscu de Citnciar, da Pontificia Universidade Catdlica do Rio Orande do Sul (MCPUCRS). Porto Alegre. at the British Museum of Natural History (BMNH). at King's College London (KQC) and at Guy's Hospital in London. The fossils helong to the Univcnidadc Federal do Acre (UFAC). Rio Branrw. Brizil. Geological information on the Solimiks Formation is given by Simpson BC h u l a Couto (1981) and by Paula Couto (1x3). Figurc 2 is hclxd on the gcologicul mup of Pmjeto Radamhil(l976). The !klim&s Formution contains remains of various mammal groups.

Aunrding w Paula Couto ( I = 34). 'the mijor part of the hones and teeth. mostly isolated. are hrokcn and mom or less rolled even when found in sitii. This is suggcstivc of reworking from older b& and that thc fiiunii is mixed up as to agc". The fossil mammals rcamrcd from the multiple Solimcies Formation lithofacics indicate. at the maximum. Late Pleistocene age.

Usual light and scanning clectron microscope techniques wcrc used to investigate the histological structure of the fossils, which although fossilized only as detached sculcs. show cxccllent preservation. At some pints. thc surfice of thc wales have hccn corroded. possibly hy mccnt fungie (Fig. 10.fit.).

Paratypes UFAC 154 and UFAC 1.55 (wales) were embedded in epoxy resin and then sectioned with a diamond powder-coated saw (Buchlcr). ground down and polished manually against sand paper. Some of the sections around 4 mm thick were subjected to etching with I N HCI for 30 s and then metalized with gold and examined under the SEM (Jwl-35 of thc SMNH and Hitschi S2SU of Guy's Hmpiul). X-rays werc ulw uxcd to a n a l p part of the mitcrial. Both extant and fcmyil specimens of various families helonging to the muscums listed shove were uscd for mmprisons.

pE? f

\ \ \, BOLIVIA

0 LOO 400 000 Km I . . : . ' : 4

Fig. 1. Gcncrrl map of thc Uppcr Amazon Basin (based on Paula Couto (1982). Fasiliferous locality within rectangle.

31 I Zoologica Srripta 18

3 I2 M. Riditcr

K E Y

ESCALA 1: l O O O m 0 - Rood

l0Km 0 10 20 Y) 40 Q K m m u - - - I

@ Town C.Y)d:':I Holocene

Plio-Pleistocem

FossiliferOU6 OU*P

FiK. 2. Map of the fi~szilifcrous outcrop at Scn;i Madurcirii. Acre Statc (modificd from Projcuto R;rdamhrusil 1Y7h).

Systematics

Class Ostcichthycs I nfraclass Ncoptcrygii Division I lalccostomi Subdivision Tclcostci Family Acregoliathidae fam.n. Genus Acregoliath gcn.n. Acregoliath mncii spa. ~-l~c~iillcs geiintcs dc '1~li.c~tdcn": 'Ihvcrnc IY7Y. fig. 12.

~1wifdfJg.r. 'Ihc generic name rufcrs to the prcsumcd large size o r tlic fish from hen. St;rte. Br;izil. The spccics niiinc is it homage t o NLVU Kiiiicy. diii collcctctl tlic iiiiitcriiil.

7:vpi~ rrrrrrcviirl. liolotypc: lIl:hC'-PV- 1.56 (;iliiiost coiiiplctc sc;iIc). 1J;ir;itypcs: [lI:M.-I'V-I54: llI:A<'-PV-155 (sc*aioncd sr.alcn): UFAC- PV- I57 (friigmciitcd scale).

/.two/iy. *I,iil;i*. Scna M;idureirii County. hcrc Sl;rtc. Hr;tdl. Sol- i m k s I:oriii;it ion. I'lio-l'lcistocciic.

Diugtiosis of species. Ostcichthycs. bearing large. thick scalcs (domvcntral height up to 8 cm. thickncss up to 1.3 cm) round in shape. with anterior and latcral fields (over- lapped areas) with parallcl and close circuli. Posterior ficld (cxposcd area) covered with glassy and birefringcnt tissuc organized into longitudinal, subparallel and coarse ribs giving scales a dcnticulate posterior margin. Glassy tissuc laid down in lamellae, sometimes highly foldcd. Contains rare cells but abundant Sharpcy's fibrcs. Focus neat. almost ccntral. Classical radii as those found in clasmoid scalcs not observed on the surface of scalcs. Instead. shallow crests radiating from the focus back- wards. These crests also madc up of the same glassy tissue Zo,nliigiccr Scripta I8

found in the ornamental ribs of posterior ficld. Lamellar bone at bdsc of scale with superimposed layer of vascular, cancellous bone tissuc containing primary and sccondary osteons. Cuncellous bone almost completcy confined to region subjaccnt to antcrior and lateral fields. Both lamel- lar and cancellous boncs containing ostcocytes. Sharpcy's fibres abundant and widespread throughout wholc scale.

Diugnosis ofgenus and family. As for spccics.

Description

Thc scales of Acregoliafh runcii (Figs. 3-19) do not casily fall into any of the alrcady known and described types of fish scales. Round in shapc (Fig. 3) thcy cxtcrnally bcar longitudinal crests (Figs. 4. 6-11, I.c.) and conccntric circuli (Fig. 4, ci.) in the anterior ficld. Therc is also an almost ccntral. neat focus (Fig. 4.fo.). In thesc characters thcy approach the teleost clasmoid (ridgc scale) pattcrn (Berth 1944). Therc is no trace of indisputable enamel or enamcloid on the anterior or latcral fields. A glassy and strongly bircfringent tissuc, however, covcrs the wholc posterior ficld and forms longitudinal, SUbpardlkl ribs (Figs. 4, 6. 17. ri.). which are scparated from cach other by deep groovcs. The samc glassy tissuc is also present in the longitudinal crests (scc below).

Onc can infer from the type asscmblage that cach scale was ovcrlapped by three adjacent scales and that only its posterior ficld remaincd exposed. Thcrc are no articulat- ing areas on the scalcs.

X-ray radiographs tdkcn from the outsidc of the scale (Fig. 5 ) disclose a significant sponge tissuc filling thc

inside. It is shown as a rcticulate and loose network o f

Triiils\ncrsc sections tiikcn from the anterior field (SCC- tion A-V’ in Figs. 4.6) demonstrate thar the main body o f the sciilc is made up of two kinds of honc tissuc. A thin layer of Iiimellar honc biisally (Figs. 6. 7. is.) with an ovcrlying. thicker layer o f cancellous. protohavcrsian honc (Figs. 6. 7. sp.) . This canccllous layer. howcvcr. diminishes in thickness caudally. and is absent from most of the posterior field. A third type of tissuc. the glassy and hircfringcnt one rcferrcd to prcviously. miikcs up the

pOlygo11ill ho11c chiimhcrs.

smiill longitudiniil crests which r;idiatc from thc rocus (Figs. 6-1 1.I.c.).

The isopcdin contiiins flattcncd ostcocytcs (Fig. 13. os.) distributed in hctwccil the bone lai11clliic.

The spoilgiosii. o r protohavcrsian tissuc (l‘nlow & 13rown l9SO). shows liirgcr ostcocytcs (Fig. 12. (IS.) with abul1dal1t. highly brii11ching cii1l:iliculiic. I’riniary ostcons (Figs. 7. I-Clh. 18. l9 .p . ) . bone triihccul;ic (Fig. 8. It-.). viiscullir spaces (Figs. 7. 8. i’..~.) and caniils or nitturd moulds o f them. previously occupied by blood vcsscls (Figs. 11. 16. 19. II.~.). iirc characteristic o f this region. Viisculiir canals iirc iibundai1l in the middle of the SC~I~CS. being found from the isopcdin to the surface o f the sciilc (Fig. 7b. 19.c.). Sherpcy‘s fihrcs iirc also one of the most striking features of thc scalc. being seen especially in the isopcdin and in the surfiicc tissues. whcrc they ciin bc arranged in parallel bundles o f very regular pattern (Fig. 10. s.J:).

A transverse section o f the posterior field (Figs. 4. 6. section B-B’) shows that in this region the ciinccllous hone layer has disiippcarcd. The ornamental ribs arc made up of many laycm o f the glassy. birefringcnt tissue (Figs. 7-9) which contains iibundiint Sharpcy’s fibres (Fig. 10. .s.J) and occiisional. very small ostcocytcs (Fig. 10. (AS.) . Contact lincs (Fig. I 0 c.1.) can be cqually observed o n the ornanicntiil. small longitudinal crests and ribs. The &ssy tissue. which is sometimes much folded. merges transitionally with the canccllous bony tissuc o f thc layer below. Thcrc is n o sharp boundary bctwccn thcm.

Some peripheriil iircils of the sc;ilc show truncatcd lincs. here intcrprctcd iis rcsorption lincs (Fig. 7, r.1.).

Zoologitu Scriptu 18

3 14 M. Richter

ri.

R- 6-' 6'

A-

- 5 mm

Fig. 6. Ac.qo/iuth mnrii gen. et sp.n. Camera lucida drawings based on paratype UFAC-W-154 transvcncly sectioned at the junction of thc anterior with the posterior field and at the middle of the posterior field (arcas cnmsponding to sections A-A' and B-B' in Fig. 4).

Resorption also occurs in the cancellous bone of the spongiosa .

Discussion

The Ainazon rivcr system now contains scvcral very large fishes (scc. for example. Gudgcr 1943). most of them Ostcoglossi formcs or catfishes. Thesc havc been captured for decades and it is likely that all of thc cxtant large fish species art: known. Ncvcrthcless. thc actual lcvcl of know- ledge ahwt the idcntity and interrelationships of South American fish is only equivalent to the knowledgc of the North Amcrican ichthyofauna of a century ago (Bohlkc et ol. 1978; Fink & Fink 1978). Scales from many of thew large cxtant fishes. including Arqmimcr. were examined in an effort to determine the affinities of these fossil scales. The following is an attempt to summarize the principal affinities and differenccs betwccn Acregoliuth tind those fishcs which sccmed to present any similarities to it.

Because of the rcmarkablc general trcnd. within thc highcr categories of living Osteichthyes. to acquirc ii rounded and elasmoid scelc in parallel (Bricn 1962; Schultzc 1966). it is sometimes difficult to recognize the characteristic features o f the classical modcls of such exoskeletal clcments when dealing with fossil spccics.

Tavcrne ( 1979) first mcntioned and figurcd the mutcrial dcscribcd here. Hc obtained some photographs from Dr Kubcns da Silva Santcx (Rio de Janeiro) and. although ascribing it to the Ostcoglossiformcs, he found that "ces Cciiillcs paraissent cepcndant differentes dcs ccllcs d'Arup~~imci gigus qu'il m'a CtC donnC dc voir. . . . II est donc possible. ct meme probable. que leu Ccailles fossiles dc R. da Silva Santos appartiennent ii une autre esptcc qu'Arupuinia gigus ct peut-etrc mCme ii un autrc genrc qu'Arupuiinu" (Taverne 1979: 137).

According to Meunicr (19H4), the scales of Arupaima have a basal layer of ccllular. incompletcly mincralized hmc. which is picrced by vascular canals and a thick

superficial. pseudolamellar layer of cellular bone rich in Sharpey's fibres.

The scalcs of Artrpairntr do supcrficiiilly rcscmblc thosc o f the dipnoan Neocerutotlus. with thc cxposcd area showing "labyrinthoid rugosity and the concealed part. elongated reticulations and bcadcd circuli" (Cockerell 19 12). On thc other hand. Lepidosirm and Pr~~tcipterus **both havc a strong radial network. whilc circuli are rcducxd to innumerable finc tubcrclcs or coarse granula- tions. approaching the condition in the lateral area of Ne~~cerntadirs" and "in I'roropferirs the network is morc obviously similar to that of the osteoglossids" (Cockerell

Nclson ( 1969: 24). cxamining the inter-relationships of osteoglossids. found that "pcrhaps thc most notable peculiarity shared by all four gcncra (SckmIpngcJs, Osreo- glossum, Arupuirnu and Hererotis) is the reticulatc typc of scale". However. as we havc sccn. reticulate scales are not ;in cxclusivc character of osteoglossids. ? I c y a h occur in Dipnoi. both fossil and cxtant (Cockerell 191 Iu, h; Brien 1962). as well as in mormyrids (Cockerell 1912).

To date, Lepidosireti pururloxu Nattcrcr is the only living dipnoan known to inhabit South American frcsh waters, but the scales of this fish arc quite distinct from thosc of Acregolinth. The same is true of rhc other cxtant dipnoan gcncra now living in Africa and Australia. All three of them have reticulatc scalcs.

Although present in recent dipnoan species and being long recorded in thc gcological history (c.g. Sagenodus from the Carboniferous), rcticulatc scales are not vcry frequent in the mtijority o f fossil spccics. which tire by far morc numcrous than the extant oncs. Acregoliuth defi- nitely lacks reticulatc scales like those of the Ostcaglos- siformes or extant Dipnoi. Ncvcrthcless. the extcrnal ornamcntation of the posterior ficld of the scales of Acregoliath is vcry similar to the ribs found in thc same rcgion of cosmine-free sctilcs of somc fossil dipnoans, c.g. Griphognuthus sciilptu Schultze ( 1969: fig. 32).

The scales of Acreguliuth are also superficially akin to thosc of somc other sarcoptcrygians. for instance thc

I91 Ih: 831).

Zooiagiru Scriptu I8

V.C.

- .-__ . -- ..

7b - 1 mm

Fig.s. 7. Acrcgaliuth runcii yen. et spn. Transverse section of paratype UFAC-155 rwrrcsponding 10 I A-A' section of thc wale (vide Fig. 4).-u. Thin scct ion.4. Corresponding drawing.

rhipidistian 1loloprycliiu.s (Hcintz 1032). Thus. in posses- sion of circuli and thc pattern o f the posterior field ornamentation. as well as the cancellous bonc tissue. Acri*goliiirh resembles Haloptychius. The 'circuli' in all sarwptcrygian sciilcs cxamincd. however. are longitudi- nally distributed and continuous in the ovcrlapping arca (c.g. Liirinicria. in Smith el a/. 1972). and not concentric and bciidcd as they usually arc in tclcostcan scalcs.

Conccrning thc intcrnal structurc. thc undisputed notion prcvails that cxtant dipnoans bear reduced cos- rnoid scalcs. Despite the fact that thc scalcs in thc thrce living genera display H general double-layered 'Bauplan', viz. iin external layer o f calcified plates and the basal isopedin. thcrc still remains a thin "soubassement

Iticuniiirc" (Brien 1962: 106) joined to the surface tissue. This cancellous bascmcnt layer. though not being consi- dered by Bricn as a "vdritablc tissu osscux" (op. cit.: 108). becausc he recognizcd that it is formed of ccdlagcn fibres dclimiting lacuniir spaces which eventually calcify, ncvcrtheless rcscmblcs the cancellous laycr found in Acregoliufh. Primary ostcons are absent in the scalcs of cxtant dipnoans. but prcscnt in the cancellous bone of Acregaliufh and also in thc superficial bonc tissuc of thc scales of Ostcoglossidae (see Meunier 1984: fig. 17).

As for its evolutionary significancc among sarcoptery- gians. the presencc of cosmine has often been cmnsidered of minor importance, since it apparently also occurs in ancient egnathans (Sertmar 1968). It is possiblc. how-

Zaalagica Scriptu 18

Fig. 8-13. Arrq<J/iUth rursrii p n . ct sp.n. Transverse scx!ions t o show the histological features of scales.410. Paratype UFAC-PV-ISS. Superficial tissues anterior field under normal light microscope.--'). Same hut under polarized light micn)scopc.-/O. Detail o f the contact lines (incwrncntal lines) in the area of the ornamental. small cmsts radiatinb from thc focus.-//. Paratype UFAC-PC-1.54. Scanning clcctronic micrograph irf superficial tissues (etched in dilute HCI) in the untcrior field. mrresponding to A-A' in Fig. 4.-/2./3. Paratype UFAC-PV-l55.-12. Osteinytcs of the upper part of the spngiusu luycr.-/3. Ostcixytes of the h;isal lamcllrr tissuc of the yrulc.

ever. that dil'l'crcnt 'types' ol' cosminc miiy bc distinguish- able itnd this would be o f interest. s inw they may thcn be rcstrictcd to different taxi1 and ~OSSCSS dcvclopmcntid ilnd hiologicol aspects of thcir own.

Nevertheless. no sort of cosminc as defined by C3rvig ( 1969) or figured by Thomson (IWS) was recognized in Acr~~~dicrrli. Thc spongiosa ( pmtohavcrsian bony layer) in this genus is dircctly bound to the glassy laycr above without any kind o f dentine scparating them.

Studies by Thomson (1975) led to the umclusion that .*the influence of thc fields in the corium upon the cosminc Iilycr o f the dcrmal skeleton is quite indepcndcnt o f the

Ztmlogica Scripru IN

foctors intlucncing the patterns o f growth i d structure in the spongiosil and lamcllar bonc making up thc rcst o f thc dcrmal skclcton" (Thornson 1975: I I ) . Whcthcr or not the spongiosa in Ac.rcJglolicit/i rcprcscnts the kind of bone tissuc associatcd with cosminc in undisputcd cosmoid scalcs is o f intcrcst. but impossible to determinc.

Sciilcs of 1Wyptewt.s (Cladistia) i~lso passcss ;I vascular layer beneath the dcntinc (Mcinkc IOXl?), but the vascular systcm of this genus mey bc interpreted ils pulp cavities o f ii dcntinal systcm rather than a truc spongiosa likc that found in Acregolidi. Anothcr striking differencc bctwcen thc tiixii is thilt lJo/yp/iwi.s hes scilles coiitcd with

it thick layer o f ganoinc. which is now prcsurncd to be true (cctodcrrnitl) cnarncl (Sire e/ ti/. IC)tK,. 1087). Bcsidcs. no cladistian fishes live in South American rivers nor have any hccn recorded as fossils.

T r d y cilnccllous bonc in scnlcs of living fish is only obscrvcd in Siluriformcs. Describing the dcrnioskclcton in ('iillic/ir/i~.s cullidiyt/i~.s. Bhatti ( 1938: 38) found that "The scute consists o f (a) an inferior hiisid lilycr of Iilmcl- liitcd iwpcdin. the larncllac running pilrallcl to the haw of the scutc with hmc-cells interspersed hctwccn them . . .

(13) the middle vascular lilycr of true I lavcrsian canals with concentric bonc lilrncllilc . . . . This layer is rich in bonc- cells: the upper layer ("ostcoid layer") which is homogeneous and hyalinc in structure. and lies over the uncovered part of the scutc. I t forms the supcrficial oriliImcntiition of well-defined ridges scp;iratcd by deep grooves or dcprcssions. which ilrc. in life. filled with blood vcsscls and nmncctivc tissue fibres and communi- ciitc directly with the middle bony liiycr. hut is sharply defined from it hy the iibscncc of bone-cells. The hone-

Z(io/oj$ku Scripru 18

cclls lie immediately beneath the upper laycr and spread out their ctinaliculi. but do not pcnctratc into its sub- stance".

Agiissiz ( 1&3.33-44) interprctcd the surface laycr of Cd- Iidithys scutcs as enamel (so placing thc Siluriformcs within the 'Ganoidci'). but Bhatti ( 1938) concludes (fol- lowing Hcrtwig 1876) "that thc upper layer in Ciil- lychthyidae is not enamcl is dcfinitcly shown by the action of the acids. which do not dissolve it. For the same reason it is not ganoinc" Bhatti 1938: 38). Further on. he um- cludcs that thc rcferred tissue "is simply a layer o f cwtcoid cell-free bonc-tissue" (Bhatti 1938: 70).

I do not agrcc that this simple acid-vulnerability criter- ion is valuable in distinguishing tissues. A diffcrcntial response to ctching. however. measurablc by the time consumed during the ilction of acids o n various tissues to achieve 11 dcfinite or established result. could bc used for this purposc. sincc it dcpcnds on both qualitative and quantitative aspects of the mincral contents in mineralized tissues. It would hardly bc a secure method to distinguish the various mincralizcd tissues of fossil remains. for in these miltcriiils the original mincral composition may bc considerably altered during fossilization.

The glassy tissue found on the surface of the s c i k of Acregoliufh approaches the configuration of this surfacc layer of tclcost scalcs rather than thc structurc of enamcl or cnameloid. It was not possiblc to demonstrate the prescncc o f any definite prismatic or hypcrmincriilizcd laycr on thc scalcs of the new genus. This surface laycr could. therefore. bc callcd 'hyalodentinc' (Hofcr 1X90; Hasc 1907) or 'hyodcntinc' of Jollic (1968: figs. 8-39. c. (1). hut the applicability o f these terms, as well as their usefulness. will be discussed in ii futurc work.

On the othcr hand. the presence o f a well-developed spcmgiosa may be an attractivc argument in favour of the siluriform affinitics o f Acregolicrth. Siluriform scutcs. however. arc highly differentiated structures, believed to hiivc becn derived from much simpler. clasmoid actinop- tcrygian scales. This differcntiation no doubt affccted not only the external shape of thc scales. which in almost till gcncra bccamc polygonel. but also affected the structure of the exposcd surface. which in many cases carrics deeply embedded. articulating denticules (odontodes). The embcdded iirea too. is very short in Siluriform scutes. hardly approaching the condition in the fossil under study.

At the moment. it thercforc scems rcasonablc to place Acregolitif/? rancii among the Teleostci fishcs. but its phylogcnctic relationships with othcr species remain unccrtain. Hopefully. future field expeditions planned for thc next fcw years will provide complemcntnry fossil material cnabling a bctter comprehension of this new species.

Acknowledgements

The author is mcmt grateful t o Alrvu Kancy. M..k (UFAC. Rio Brilnm) for sending the fossil niaterial descrihcd hen.; ti) the geologist Erncsto L. Liivinii for in formiition concerning thc strutigriphy of the collecting iiwii: t o Prof. T. Brvig for his hospitrlity in Stockholm end for many profitrhlc discussions about the histology of hird tissues in lower vcrtchmtcs: to Mrs Rosalie Rcnchimol (Univcrsidadc Fcdcnil do Amwn)nas). Jonas Pcrcira de !hum Filho. M.k . (UFAC. Rio Brilnrw). Luiz Roberto Malrharhr. M.Sc. and Rohcrto L w r dos Rcic. M.Sc.

Zmlogica Sctipta I8

(hoth from MCI'UCKS. Ikr to Align.). for supplying Rcrvnt ichthyological miitcrirl for aompriwns: to Mr K. C. Rcdmond (King's College London) for linguistic corrections: to Dr Moyii M. Smith (Guy's Hospital. London) for discussing the histological structurc o f the fossil iind giving the iluthor access to Guy's Hospit;il facilities: to Prof. B. G. Ciadincr (King's Ciollcgc London). Dr Colin I'uttcrson. Dr 1'. L. Fowy. I)r P. 11. Circcnwcwxl (British Muscum of Naturiil History) and Dr Bobh Schiicffcr (Amcricain Museum of Natural History) for sharing with her the still unsolved problem of the systematic dfinitics of the fiwil. Dr CCcilc Poplin and Dr J.Y. Sire (Paris) commented on the manuscript. providing much improvement. 'The author gratefully iicknowlcdps the grints rcrvivcd to dcvcliqi this work. hoth in Rnrzil itnil alr,nd. by the <'onsclho Nacionul dc Dcscnvolvimcnto Cicntifirw c TLu.nol6girw (CNPq) of Brazil.

Abbreviations used in the figures c'i. c:l p. f l i . i.s. 1.e.

p.i>. ri. I: I

sp. tr.

fAY.

b. f

r.c. I'.S.

rimiili line focus possible fungal remains isopcdin longitudinal small crcsts

primiiry cEitcons cirnamcntal rihsof the posterior field resorption lines Shiirpey's fihrcs spongicwzr mrdc upof pn>toh;ivcrsiiin bone tissue Inme trahccullu vascular c;iniils (or autural mouldsof them) viisculiir spaces

1EitCCK)lCS

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