Origin evolution and homologies of the Weberian apparatus a new insi - PDF document

Origin, evolution and homologies of the Weberian apparatus: a new insight. SUMMARY Department of Anthropology, George Washington University, Washington DC, USA. 334 macropomaClupavus maroccanusSorbininardus apuliensis and Tischlingerichthys viohli(Diogo, 2007; see Fig. 1). This thus allows having a moreand evolution of some key Weberian structures. Origin, evolution and homologies of the Weberian apparatus: a new insight. MATERIAL AND METHOD The phylogenetic framework for the discussionscladistic analysis of teleostean higher-level phylogenyostariophysans) are shown in Figure 1. The actinopterygiancias Naturales de Madrid (MNCN), the American Museumof Natural History (AMNH), the Academy of Natural Sciencesof Philadelphia (ANSP), the Chinese Academy of Sciencesat Wuhan (CASW), the California Academy of SciencesMuseum of Natural History (USNM). The list of specimensobserved. Dissections were made using a Wild M5 dissectingmicroscope equipped with a camera lucida. The informationextensive overview of the literature available (e.g. Taverne,: ANSP 107961, 2 (alc); ANSPplatyrhincus: AMNH 74789, 2 (alc). Psephurus gladius: CASW,: AMNH 44315, 1 (alc); AMNH 44344, 1 (alc).Hiodon tergisussetirostris: MNCN 245730, 3 (alc). brevirostrisnigrodigitatusCromeria nilotica: MRAC P.141098, 2 (alc).Danio rerio: MNCN, 10 (alc). Diplomystes chilensis: MRAC A0-048-P-2630, 3Gonorynchus greyi: INHS 35493, 2 (alc). MNCN 115675, 2 (alc). Opsariichthys uncirostrisParakneria abbreviataPhractolaemus ansorgii: MRAC P.137982, 3 Pimelodus blochiiTrichomycterus areolatus: MRAC A0-048-P-2539, 3 (alc). Alepocephalus rostratusArgenti-Argentina sphyraenaMNCN

001134, 12 (alc); MNCN 78530, 5 (alc). Astronesthesniger: MNCN 1102, 1 (alc). 1170, 6 (alc). Bathylagus longirostris: MNHN 2005-1978, 2 (alc). Chlorophthalmus: MNCN 1193, 3 (alc); MNCN 1182, 5 (alc).Coregonus lavaretusCoregonus: MNCN 193795, 11 (alc). mordaxRetropinna retropinna: AMNH 31037, 1 (alc). : MNCN 115147, 1 (alc); MNCN114992, 1 (alc). Origin, evolution and homologies of the Weberian apparatus: a new insight. 336 (modified from Chardon Dorsal view of labyrinths, sinus impar and ossicles. The right labyrinth was pushed laterally for showing the Dorsal half of the swimbladder with ossicles and hind part of labyrinths. Notice the exoccipital bridge (inlight grey) covering the saccules and lagenas. The ossicles were pulled laterally (arrow) as if the swimbladder was compressed.Ventral half of the swimbladder showing the thin median area and its anterior arch and the lateral cutaneous areae (both in lig, camera aerea Weberiana; osus Origin, evolution and homologies of the Weberian apparatus: a new insight. RESULTS AND DISCUSSIONHomologies of the Weberian ossicles With exception to the shape of the os suspensorium(see below), the overall configuration of the Weberian2, 3D, 4B, C, D, 6B; e.g. Weber; Sagemehl; Bridge &Haddon; Chranilov, 1927, 1929; Alexander, 1961b, 1964ab;Popper, 1971; De la Hoz & Chardon, 1984; Grande &). The curved posterior portionhand, connected by the suspensor ligament to the ossuspensorium (Figs. 2, 3D, 6B). The anterior portion of et al. Such a configurationof the Weberian ossicles and associated ligaments thusmakes that, by changing the volume of the swimbladder, consequently, the anterio

r Weberian ossicles,3D). Above the scaphium usually lies a small ossicle, theclaustrum (Fig. 4B, C, D). This ossicle does not really makeswimbladder and the inner ear. Authors such as Grande &different ontogenetic origins for the Weberian ossicles ofextant otophysans, thus suggesting different homologiesteleosts (e.g. Weber; Watson, 1939; Bamford, 1948; Butler;., 1989; Vandewalle Coburn & Futey, 1996; Coburn & Grubach, 1998; Heyd &Pfeiffer, 2000; Grande & Shardo, 2002; Chardon 2004; Grande & Young, 2004).Weberian ossicles have been proposed in the literature: that(e.g. Weber); that they represent modified portions of theWatson; Kulshresta; Chardon ). The first of thesetheories (Weber) has been discarded by the accumulation ofdata on vertebrate phylogeny, ontogeny and evolution.However, there is still controversy on whether the Weberianossicles are exclusively, or just partially, originated byWeberian apparatus of extant otophysans (e.g. neural arches,Grande; Grande & De Pinna, 2004; Grande & Young, 2004). Authors such as Bamford; Butler; Rosen &Watson; Kulshresta; Rademarker .; Vandewalle (1990); Grande & Young (2004), stated that this ossicle ismesenchyme. According to some of these latter authors (e.g.Watson), the mesenchyme contributes to the formation of The phylogenetic scenario shown in Fig.1, includingChanoides macropoma andClupavus marocannusChanoides macropoma show typical Origin, evolution and homologies of the Weberian apparatus: a new insight. Intercalarium Regarding the intercalarium, authors such asBamford; Vandewalle from the second neural arch. Others (e.g. Watson; Butler, et aland evolution of the Weberia

n apparatus as a whole. In fact,the origin and evolution of the chain of Weberian ossiclesindirect the scaphium (Fig. 6B). The other hypothesis, which I calldirect hypothesis', was formulated by authors such asWatson; Chardon thus the complete intercalarium (Fig. 3D). Thus, anbe used by some researches as an argument in favor of thedirect hypothesis. Alternatively, an initial ontogenetic originof the intercalarium from two different parts, one from theligament interossicular, with the connection between theseby some authors as an argument in favor of the indirecthypothesis. Developmental studies on the Weberianto the surrounding Weberian structures.Chanoides macropomaChanoides chardoni andClupavus maroccanusChanoides macropomashown in Fig. 4A, Patterson, draw the ligament interossicular,but this was due to the functional interpretation of that author,not to a real preservation of this ligament in the fossil). Firstly,otophysans. This because, as will be seen below, althoughneural arch of other fishes. For example, they are largeChanoides macropoma (Figs. 4A, 5;Secondly, the overall configuration of the Weberianevolution of the Weberian apparatus. For instance, theChanoides macropomahypothesis (Fig.4A). Moreover, the intercalarium of theWeberian apparatus of and Clupavus maroccanus eitherChanoides macropoma et.). Any of these two options would support the directhypothesis. This because they would suggest that in thosefunctional, Weberian apparatus the manobrium was stillChanoides macropoma Origin, evolution and homologies of the Weberian apparatus: a new insight. 339 (2003) hypothesis about the origin of the Weberian app

aratus (modified from 'Clupeiform-like' stage with an otophysic connection. The anterior duct between the swimbladder and the bulla is coated by the tunica exterlabyrinth is surrounded by a perilymphatic space. The first two haemal arches are reduced. Parapophyses and ribs 3 and 4 are jo Fully hypothetical stage. The haemal arches are not figured. The endodermic epithelium andsplanchnopleura have disappeared in the duct and bulla. The duct, reduced to the fibrous tunica externa, becomes the interossicof the tripus where the fibers of the tunica externa exert a traction. The parapophyses of free vertebrae 3 and 4 are not figurChanoides macropoma and/or -like stage. The anterior neural arch (or a paired supraneural?) becomesthe claustrum. The first neural arch transforms into the scaphium (articular and ascendens processes) and fuses with the conchathird haemal and possibly the third rib fuse with the transformator and become the tripus. The fourth haemal arch transforms inligament. An osseous nodule probably appears in the interossicular ligament: the manubrium of the future intercalarium (not fig Stage of extant otophysans. The second neural arch attaches to the manubrium to form the intercalarium. Origin, evolution and homologies of the Weberian apparatus: a new insight. morphofunctional point of view, if one applies the indirecthypothesis suggested by Rosen & Greenwood to basalunfunctional, unlikely Weberian apparatus. As can be seenin Figure 5B and 5D, these fossils seemingly had large andintercalarium) and 3. Moreover, these structures wereessentially situated dorsally to the tripus. Thus, with such aarches (lig. E o

f Fig. 6A), as proposed by the indirectClupavus maroccanus does not lie within the line oftly only two ways in which the Weberian apparatusof these fossils might have been functionally efficient. One isby having a direct ligament between the tripus and thescaphium (Fig.3C). The other is by having a sesamoidChanoides macropoma (Figs.3D,4A). Therefore, in view ofthe origin and evolution of the Weberian interossicularligament. Thus, I am inclined to agree with an evolutionaryMoreover, my own anatomical comparisons between extantsuch as Rosen & Greenwood. This because, among all thediscussing homologies. As explained above, theneural arch. However, it is also important to stress thatdevelopmental data is not the only, and in some specific ca-in discussions of homology. Development does not alwaysMabee, 1989ab, 1993; Gould, 2002). This is well-known intheory, but unfortunately continues to be too often neglectedin practical discussions of homology, as pointed out by As stated by De Pinna & Grande; Grande & De Pinnacontinues to be, controversial. The data available from theChanoides macropoma andClupavus maroccanus does not help to clarify thespecimens (Figs. 4A, 5). According to Patterson, Gayet(1981, 1985), Taverne (1995) and Filleul & Maisey, the lackChanoides macropomamaroccanus might be due to a real absence of the ossicle or,perhaps more likely, to its bad preservation in the fossil re-cord. The apparent presence, according to Taverne's (2005:Chanoides chardoni Concerning the developmental data available, differentauthors have different interpretations. For instance, Fink &Fink (1981) argued that the claustrum develops fr

om adissociated portion of the first neural arch. In turn, Watson;Vandewalle the arguments used to support each of these three hypotheses.These latter authors argued that the developmental data(2004) also provided topological and functional arguments infavor of their hypothesis. They argued that the claustrum, like Origin, evolution and homologies of the Weberian apparatus: a new insight. 341 Fig. 4. Outline drawings of the Weberian ossicles in Chanoides macropomaOpsariichthys uncirostris (C) Diplomystes papillosus (modified from Patterson, 1984; the identity of thelatter vertebra (Fig. 3A). Thus, as explained above, accordingarch series. The homology between the claustrum of extantclupeomorphs has also been considered to be likely by. Consequently, this now constitutes, in a certainway, the most accepted hypothesis for the origin of thisossicle. However, more detailed developmental, as well as Origin, evolution and homologies of the Weberian apparatus: a new insight. Tripus Concerning the tripus, authors of developmental. (1988), Vandewalle (1993, 1996)argued that this ossicle develops exclusively from theBamford, Rosen & Greenwood; Grande & Young (2004)authors, e.g. Watson; Kulshrestha; Bogutskaia argued thator of the interossicular ligament. This latter hypothesis was The palaeontological data obtained so far from basal strongly support the idea that bothotophysans. This because both these structures are clearlyFig. 5D). As written on the above discussion on theWeberian apparatus should pay special attention to theligament or the swimbladder, as well as to the connectionsbetween these and other Weberian structures.

Developmental studies such as Vandewalle (1993, 1996)parapophysis of the fourth free vertebra. However,this vertebra. Other authors, e.g. Rosen & Greenwood, argued The os suspensorium is the Weberian structure thatotophysans (see e.g. Fig. 4B, C, D). This structure does alsoChanoides macropomaChanoides chardoni and Clupavus maroccanus macropoma the compound structure formed by the rib anduncirostris (Fig. 4A, B). However, no information is availableChanoides macropoma (Patterson).Consequently, it is difficult to discern if in this species anyswimbladder, asthe os suspensorium of uncirostrisWeberian apparatus Some authors suggested that the characteristicWeberian apparatus present in the extant members of theGayet 1981, 1985, 1986a, 1986b; Gayet & Chardon). Thismore closely related to fossils with a 'plesiomorphic'Weberian apparatus such as Chanoides macropoma or Clupavus maroccanus than tosome other extant otophysans. This hypothesis was however et alcontroversy was the fact that, until so far, discussions on theChanoides macropomaClupavus maroccanusbut also members of closely related groups such asTischlingerichthys viohli and Origin, evolution and homologies of the Weberian apparatus: a new insight. 343 Fig. 5. Outline drawings of the Weberian ossicles in Clupavus maroccanus (modified from Gayet, 1985; Taverne, 1995; Filleul & Maisey, 2004; the identity of the structures illustated follows that usedSorbininardus apuliensis as well as clupeomorphs, cantherefore bring light to this controversy. According to theChanoidesmacropoma Clupavus maroccanus appear, together with another fossilexhibiting a 'plesiomorphic' Weberia

n apparatus,, in a monophyletic unit that is the sister-This thus seems to suggest that the characteristic Weberianonce. A 'plesiomorphic' Weberian apparatus appeared in theChanoides macropoma,Clupavus maroccanus Origin, evolution and homologies of the Weberian apparatus: a new insight. orders, being then further modified in the characteristic,functional Weberian apparatus (e.g. Chardon Chanoides macropoma seem effectively more and maroccanus are not well preserved, and it is thus not clear if et al. The primaryClupavus maroccanusmacropoma are less derived thanChanoides macropoma Clupavus maroccanus (Fig. 5). However, the intercalaria of these three latterspecies are effectively much larger than the intercalaria ofFig. 4B, C, and D). The primary homology hypothesis statingClupavus maroccanusChanoides macropoma Taverne (1999), Chardon . and Taverne (2005) calledthe attention for some morphological differences betweenmaroccanusChanoides macropomaChanoides chardoniChanoides macropomaChanoides chardoni is alsorelatively small, although it is not as small as that ofChanoides macropoma: Taverne, 2005: fig. 12). Moreover,Chanoides macropoma and chardoni seemingly lacks a transformator tripodis; inChanoides macropoma most of the lateral portion of theHowever, it should be noted that Fink & Fink (1996) statedChanoides macropoma. Therefore, it is not clear whetherChanoides macropoma has, or not, a transformator tripodis. is apparently situated mainly anteriorlyto its mesial portion. This, again, is different to thecompare with Fig. 4B, C, D). Moreover, according to the(Fig. 5B). However, the tripus of the specimens shown in figur

es 24 and 25 ofGayet (1985) is apparently very different from that showndistal incurvation. The tripus of is unknown (Cavin). As noted by Taverne (1995), the tripusClupavus maroccanus specimens analyzed by himis poorly preserved (Fig. 5C). However, from the figuresprovided in Taverne's (1995) work, it seems that the tripusof that species is also different from the characteristic tripusClupavus maroccanus isnot homologous. They support, instead, the view of authorsTaverne (1999, 2005) and Chardon et al.Clupavus maroccanusChanoides macropoma, chardoni derived than that of extant Origin, evolution and homologies of the Weberian apparatus: a new insight. 345 and otophysans such as the (modified fromD, E, F, G, ligaments A, B, C, D, E, F Origin, evolution and homologies of the Weberian apparatus: a new insight. Chanoides macropoma,Clupavus maroccanus (Figs. 4A,5A, B, C, D). However, as noted by Patterson, Gayet (1981,1985), Taverne (1995) and Filleul & Maisey, in extantsuch as gymnotiforms and many siluriforms. According towas effectively missing in all members of those species. Asnoted above, this view was supported by the apparentdiscovery, by Taverne (2005), of a well-developed claustrumChanoides chardoni.macropoma,maroccanus otophysans. Interestingly, contrary to the configuration foundPatterson, Gayet (1985) and Taverne (1995) the osChanoides macropoma and Clupavus maroccanus does not form,should however be stressed that Patterson apparentlyChanoides macropoma (see above). Therefore, this latterthe rib of the fourth free vertebra of this species (Fig. 4A). Asshape, and, thus, that it difficult to define, in reality, wh

at is theWeberian apparatus, needs to be made: when it is said, as wasdone above, that the 'true', functional Weberian apparatus. and Grande & De Pinna (2004), it isWeberian apparatus and many of the necessary requirementsswimbladder, the constriction of the swimbladder into twoGrande & De Pinna 2004). However, as stressed by Chardonthese fishes have a functional Weberian apparatus as that ofof the Weberian apparatus.various features involved in the functioning of the Weberianavailable, it seems effectively possible to provide here an up-been, in major lines, the evolution of these features. Thisdiscussion is given below, and is divided into three parts, which Some important features related to the peculiarconfiguration and the peculiar functioning of the Weberianapparatus of extant otophysans seemingly appeared in the nodeostariophysans (Fig. 1). These include, for instance, the pos-De Pinna, 2004). Thus, plesiomorphic otocephalans seeminglycrucial for the formation and functioning of the Weberianapparatus of extant otophysans. However, one should keep inand that, althoughthese structures seem effectively to be Origin, evolution and homologies of the Weberian apparatus: a new insight. be completely sure if they were effectively also present in orTischlingerichthys viohli (Fig.1). Consequently, unless theif such features were effectively present in these fossils, onethe Weberian apparatus as a whole, and that may also possiblyattachment of the anterior pleural ribs to the swimbladder.and in extant otophysans. However, as pointed out by GrandeSince it is difficult to discern if such a configuration wasTischlingerichthys vi

ohliSorbininardus apuliensis, it is difficult to appraise ifClupeomorpha (its absence in extant clupeiforms such as being thus due to a secondary loss), and, therefore,Chardon & Vandewalle (1997) and Chardon of the Weberian ossicles: the presence of an anterior otophysicskull and contacting the inner ear, as seen for example in manyextant clupeiforms (Fig. 3). As explained above, according tothese authors the interossicular ligament of the Weberian chainswimbladder diverticula (Fig. 3). As an argument forligaments. Therefore, they hypothesized that clupeiform-like3). According to these authors, this sheet was probablyinefficient in transporting gas (and pressure) instantaneouslybecause the lumen of the diverticula was too narrow, whileConsequently, according to them, the 'functional part' of theWeberian ossicles would be the result of intraligamentous.). Therefore, the neural arches 1 and seems to suggestdiverticula connecting the swimbladder to the inner ear.origin of the interossicular ligament of the otophysan Weberianand gonorynchiforms seem effectively to have followed twodifferent evolutionary pathways regarding the connectionHowever, if one accepts Chardon Weberian interossicular ligament from anterior diverticula ofthe swimbladder, one could as well postulate an alternativescenario, which is perhaps even more likely than thatin clupeomorphs. That is, it might well be that both otophysansear. Such a scenario is not unlikely. As recently summarizedwithin teleosts. They are for example present in numerousHolocentridae and Cichlidae. Moreover, one should keep inCalophysus macropterus exhibits a modified swimbladder Or

igin, evolution and homologies of the Weberian apparatus: a new insight. These diverticula lie ventral to the Weberian ossicles and are1968: fig 71). As swimbladder diverticula have been acquiredvarious times within the Teleostei, one cannot exclude theCalophysus macropterus or those found in clupeomorphsand then been transformed in the Weberian ossicular ligament.in at least some of their descendents. Thus, starting fromdifferent otocephalan groups such as clupeomorphs ands hypothesis of an origin of theinterossicular ligament of the Weberian apparatus fromGreenwood, illustrated in Figure 6. According to this latterhypothesis, the Weberian interossicular ligament was derivedjoining this latter neural arch to the first neural arch. However,there are three main difficulties with this hypothesis. Firstly,(see above). Secondly, in all the numerous otocephalan fishesI have dissected so far, I never found a well-defined ligamentGreenwood hypothesis. Thirdly, if such a ligament wasneural arch should have suffered an evolutionary loss of theirthe interossicular ligament of otophysans (see Fig. 6). Thisis not theoretically impossible. However, the recent advances., 1996; Collard & Wood,for the origin of the interossicular ligament of the Weberianintermuscular bone. As stressed by Patterson & Jonhsonteleosts. And the study of muscles and ligaments has,unfortunately, deserved less attention in teleostean literature2000b). As noted by Patterson & Jonhson; Chardon Two arguments can be given in order to support apossible origin of the Weberian interossicular ligament ofbone. The first is that, as noted by Patterson & Jonhson,region of

clupeomorph and gonorynchiform fishes. Suchostariophysans. And they are, in fact, present in some basalChanoides macropoma and (e.g. Patterson; Gayet, 1981,1985). Moreover, in some adult otocephalans I have dissected, Ilisha and the gonorynchiform The paragraphs above stressed the fact that someWeberian apparatus of otophysans, such as the posteromedianof a silvery peritoneal tunic of the swimbladder, but also theattachment of the anterior ribs to the swimbladder, mightHowever, as might be expected, the configuration of the an-Tischlingerichthys viohli andSorbininardus apuliensis Origin, evolution and homologies of the Weberian apparatus: a new insight. leading to the Ostariophysi there was an acquisition of a largenumber of peculiar, derived features that were subsequentlycrucial for the formation and functioning of the Weberianapparatus. The marked enlargement of the anterior neural5, 6). According to Rosen & Greenwood; Fink & Fink (1981,otophysans. However, as explained above, it is not possibleSorbininardus apuliensisTischlingerichthys viohliin the node leading to the Ostariophysi is the enlargement ofthe anterior supraneurals. Within this clade, these supraneuralsare usually enlarged in the Gonorynchoidei and in theSorbininardus apuliensisTischlingerichthys viohli had, very likely, enlarged anteriorsupraneurals. However, since the anterior supraneurals of theTischlingerichthys viohli enlargement of the anterior supraneurals is a synapomorphyof the whole Ostariophysi, or, instead, of ostariophysans and, also present an enlargement of the anterior supraneuralsGrande & De Pinna, 2004; Diogo, 2007). However, this is and

in basal clupeomorphs such as probably due to homoplasy.Tischlingerichthys viohli and Sorbininardus, this is not so clear. In Tischlingerichthys viohlicentra of the free vertebrae 4, 5 and 6, for example (e.g. Arratia:Sorbininardus apuliensistra of the first three free vertebra is unknown (Taverne, 1999).shortening of the centra of the first three free vertebraeFrom the first ostariophysans, two main differentotophysans, respectively. In gonorynchiforms, there is aand the back of the skull (Rosen & Greenwood). The detailsand will thus be only briefly summarized here. As infree vertebrae (Fig. 6). However, although in gonorynchiformsthe rib of the third free vertebra is usually enlarged relativelythe peculiar Weberian apparatus of these latter fishes (see Fig.skull, near to the level of the inner ear, such as the basioccipitaland/or exoccipital. A careful dissection of the postcranial regionmovements of the external layer of the swimbladder thesomewhat mobile rib of the third free vertebra does effectivelyHowever, as pointed out by e.g. Chardon the anterior portions of the cephalic ribs do not really penetrateto directly contact with the structures of the inner ear, it doesefficiently transmitted to the inner ear. That is why I agreeefficient otophysic connection between the swimbladder andthe inner ear. In fact, such an indirect connection between the (Diogo, Origin, evolution and homologies of the Weberian apparatus: a new insight. structure attached to the swimbladder, as ingonorynchiforms (Fig.6A). Also, as in manyeffectively establish an indirect connection between this riband the back of the skull. Moreover, the la

teral surface ofgirdle. This latter is, in turn, associated to the back of theskull by two strong, thick ligaments: the Baudelot's ligamentligament attaches anteriorly on the intercalar, which is a smallswimbladder, realized by the anterior extensions of thisbladder (Fig. 3A). Thus, derived clupeiforms such as have: 1) a direct connection between theswimbladder and the inner ear, which according to authors. could have originated the Weberiangirdle, similar to that found in gonorynchiforms. As into constitute a functional, efficient system allowing the innerear to detect the changes of volume of the swimbladder. Suchthe pectoral girdle), or, less likely, as part of a system related The evolutionary pathway followed by otophysanswas quite different from that followed by gonorynchiforms.swimbladder as the inner ear, as described above (Figs. 2, Some of the most significant morphologicaltransformations that have lead to the Weberian apparatus ofextant otophysans, and that differentiate the condition foundClupavus maroccanusChanoides macropomaHowever, since the data available does not allow to discernClupavus maroccanusmacropomaClupavus maroccanusmacropoma, and already had'plesiomorphic' Weberian structures such as the tripus,major differences concerning the configuration of theseClupavus maroccanus (Fig. 5C), in extant otophysans theC, D). And, contrary to some of these fossils, as e.g.Chanoides macropoma (Fig. 4A), in the vast majority ofdifferences between the Weberian ossicles of these fossilsand those of extant otophysans is given above. What isthe claim that the characteristic Weberian apparatus foundher, some extant ot

ophysans were very likely more closelyClupavus maroccanus and than to other extantotophysans. However, the results of Diogo's 2007 cladistichypothesis. Those results support a single origin of a Origin, evolution and homologies of the Weberian apparatus: a new insight. 'plesiomorphic' Weberian apparatus, as that found in fossilsClupavus maroccanusChanoides macropomaand a single origin of the characteristic Weberian apparatus of It is hoped that, by complementing the author'smaroccanusChanoides macropomaof the Weberian apparatus. The complex Weberian apparatusfunctioning of this apparatus. This, of course, is just abe, tested in future studies. There are, in fact, interestingof the Weberian apparatus. For instance, special attentionsurrounding structures of the Weberian apparatus ofinformation through the Weberian ossicles to the labyrinths.And, hopefully, if this will be possible, to the configurationof new fossil Weberian apparatuses. It is precisely hopedthat this work may stimulate, and pave the way for, suchstructural complexes of Vertebrates, the Weberian apparatus. I would like to thank J. Snoeks, E. Vreven, and the lateG.G. Teugels (Muse Royal de l'Afrique Centrale), P. Laley Nationale du Bnin), R. Vari, J. Williams and S.Jewett (National Museum of Natural History), T. GrandeNatural History), Mark Sabad and J. Lundberg (Academy of(Illinois Natural History Survey) and P. Pruvost and G.providing a large part of the specimens analyzed for this study.I would also like to acknowledge P. Vandewalle, I. Doadrio,Z. Peng, S. Weitzman, T. Abreu, A. Zanata, F. Meunier, S.He, D. Adriaens, F. Wagemans, C. Oliveira, E. Parmentie

r,M.M. de Pinna, P. Skelton, F.J. Poyato-Ariza, H. Gebhardt,M. Ebach, A. Wyss, J. Waters, B. Perez-Moreno, G. Cuny, A.Choudhury, M. Vences, S.H. Weitzman, L. Cavin, F. Santini,J.C. Briggs, L.M. Gahagan, S. Hughes, M. Gayet, J. Alves-Gomes, G. Lecointre, M. Chardon, P. Vandewalle, C. Bor-anatomy, functional morphology, phylogeny and/or evolution. RESUMENdo interno. A pesar de ser uno de los sistemas complejos m como de un recientefalos Otofisios y no Otofisios existentes, sino tambiChanoides macropoma, Clupavus maroccanus, Santanichthys diasii, Lusitanichthys characiformis, Sorbininardus apuliensisTischlingerichthys viohliPALABRAS CLAVE: Evolucia funcional; Ostariofisios; Otocefalos; Otofisios; Filogenia; Teleosteos; Apara- Origin, evolution and homologies of the Weberian apparatus: a new insight. Alexander, R. McN. The physical properties of the swimbladdersof some South American Cypriniformes. Alexander, R. McN. The structure of the Weberian apparatus inProc. Zool. Soc. Lond., 139Alexander, R. McN. The evolution of the Weberian apparatus inProc. Zool. Soc. Lond., 143Alexander, R. McN. The structure of the Weberian apparatus inProc. Zool. Soc. Lond., 142Alexander, R. McN. Structure and function in catfish. Arratia, G. Basal teleosts and teleostean phylogeny. Bamford, T. W. Cranial development of Galeichthys felis. Proc.Zool. Soc. Lond., 118Bogutskaia, H. G. Development of the Weberian apparatus duringBridge, T. W. & Haddon, A. C. Contributions to the anatomy offishes: II The air- bladder and Weberian ossicles in the siluroidPhil. Trans. Roy. Soc. Lond., 184Butler, J. Development of the Weberian apparatus of catostomidfis

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)&&?)4 5 Origin, evolution and homologies of the Weberian apparatus: a new