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Monophyly of the Euteleostean : Neoteleostei, Eurypterygii, and Ctenosquamata Author(s): G. David Johnson Source: Copeia, Vol. 1992, No. 1 (Feb. 3, 1992), pp. 8-25 Published by: American Society of Ichthyologists and Herpetologists Stable URL: http://www.jstor.org/stable/1446531 Accessed: 24/05/2010 17:07

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http://www.jstor.org Copeia, 1992(1), pp. 8-25

Monophyly of the Euteleostean Clades-Neoteleostei, Eurypterygii, and Ctenosquamata

G. DAVIDJOHNSON

Although the integrity of Rosen's Neoteleostei, Eurypterygii, and Ctenosqua- mata has been maintained in most subsequent classifications, the evidence cited for monophyly of each is conspicuously disparate. Previously proposed synapomorphies are reviewed and evaluated based on my own assessment and/ or that of other authors. Those that appear least ambiguous with respect to a hypothesis of monophyly for each clade are identified. Three previously unrec- ognized structural innovations, each congruent with a different clade, afford new evidence of monophyly. At the level of the Neoteleostei (stomiiforms and above), concomitant with the advent of the retractor dorsalis muscle, there is a shift in the insertion of the third internal levator from the dorsal surface of the fourth pharyngobranchial cartilage to the fifth upper pharyngeal toothplate. At the level of the Eurypterygii (aulopiforms and above), the medial pelvic radial fuses with the ventral half of the medial pelvic ray in early ontogeny. At the level of the Ctenosquamata(myctophids, neoscopelids, and above), the fifth upper pha- ryngeal toothplate is absent and with it the associated third internal levator. Recognition of the unique ctenosquamate synapomorphy follows from the res- olution, based partially on ontogenetic evidence, of long-standing confusion about the identity of the fourth and fifth upper pharyngeal toothplates in higher euteleosts.

IN his seminal work emphasizing the dorsal not been challenged seriously, except by Rosen gill arch elements, upper jaws, and caudal himself (1985) (Fig. 2), there is substantial dis- skeleton, Rosen (1973) proposed the first os- parity in the evidence that has been cited sub- tensibly resolved phylogenetic hypothesis of the sequently in support of their monophyly (i.e., cladistic relationships among major groups of synapomorphy lists for each). For example, of higher euteleostean . Among the major eight synapomorphies listed in total for the conclusions of that work (Fig. 1) were (1) di- Neoteleostei by Rosen (1973), Fink and Weitz- agnosis of a monophyletic Neoteleostei, in which man (1982), Lauder and Liem (1983), and Ro- Rosen included the stomiiforms as the sister sen (1985), only one is common to all four lists. group of a monophyletic Eurypterygii (all other This ambivalence is exacerbated by the fact that neoteleosts); (2) separation of the old myctophi- characters frequently have been rejected or ig- forms (=Iniomi, sensu Gosline et al., 1966) into nored with no justification or discussion. two monophyletic lineages, a newly restricted I encountered this confusing state of affairs (myctophids and neoscopelids) in the early stages of an investigation of the and the (all other myctophi- affinities of the rare Japanese Pseudotrichono- forms, giganturids and various fossil genera); tus altivelis Yoshino and Araga (in Masuda et and (3) placement of aulopiforms as the sister al., 1975), described originally as a myctophi- group of a monophyletic Ctenosquamata, in form but suggested by Johnson (1982) to be which the new Myctophiformes is the sister more advanced. To confidently place this fish group of the . In the introduc- within one or another clade of higher eutele- tion to her treatise on the limits and interre- osts, I found it necessary to attempt to sort out lationships of acanthomorph fishes, Stiassny what might be considered "valid" synapomor- (1986) referred to the "phylogenetic reality" of phies from some of the more ambiguous evi- the Neoteleostei, Eurypterygii, and Ctenosqua- dence that has been set forth. My goal was not mata, implying that these groups generally have to undertake an overall parsimony analysis but been accepted by subsequent authors as origi- to examine proposed characters independently nally delineated by Rosen (1973). Although it to evaluate their homology based on both the is true that the monophyly of these clades has morphological evidence and congruence with

? 1992 by the American Society of Ichthyologists and Herpetologists JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 9

I .NEOTELEOSTEI I EURYPTERYGII I I CTENOSQUAMATA I ACANTHOMORPHA MYCTOPHIFORMES

AULOPIFORMES

VIII V-VII

I-IV

Fig. 1. Cladogramof relationshipsamong three euteleostean clades, as proposed by Rosen (1973). Roman numeralsrefer to charactersso numbered in text.

Rosen's (1973) hypothesis. In particular, be- In this paper, I follow the taxonomic nomen- cause of the apparent ambiguity of many of these clature of Rosen (1973), unless otherwise stated. characters, I wanted to identify what, if any, The Aulopiformes comprises two subgroups, the were the unique, unreversed synapomorphies Aulopoidei (Aulopidae, Chlorophthalmide, of the major clades; these would provide the Bathysauridae, Scopelosauridae, Bathypteroi- most satisfying solution to the placement of dae, and Ipnopidae) and the Alepisauroidei Pseudotrichonotus.In the course of my review, (Alepisauridae, Omosudidae, Scopelarchidae, three additional characters came to light, each Evermanellidae, Harpadontidae, Synodonti- providing cogent evidence for the monophyly dae, Anotopteridae, Paralepididae, and Pseu- of Rosen's Neoteleostei, Eurypterygii, and dotrichonotidae, the latter not considered by Ctenosquamata. The primary purpose of this Rosen); however, work in progress on Pseudo- paper is to describe these unique synapomor- trichonotusindicates that aulopids are the sister phies, two of which are founded in evidence group of synodontoids (Synodontidae, Harpa- from early ontogeny, and demonstrate their dontidae, and Pseudotrichonotidae). The Myc- congruence with each clade. Additionally, I dis- tophiformes includes only the Myctophidae and cuss my review of previously proposed synapo- Neoscopelidae. Giganturids and fossil taxa were morphies and identify those that appear to be not considered in the present study. the least ambiguous based on my own assess- ment and/or that of other authors. This paper NEOTELEOSTEI will provide the foundation for a more detailed study of the precise relationships of Pseudotri- Rosen (1973) diagnosed a monophyletic Neo- chonotus, which will not be considered further teleostei (Stomiiformes + Aulopiformes + here (see Johnson, Okiyama, and Tominaga, Myctophiformes + Acanthomorpha) based on 1989, unpubl. abstract, Third International three synapormorphies: (1) presence of a re- Conference on Indo-Pacific Fishes). tractor dorsalis muscle; (2) presence of ascend- 10 COPEIA, 1992, NO. 1

0 0"3 \ , < 6~io~3~- (p-5 9C3 0 0, •o•S 0 " 0 0 + 0 0 0 . oo,,? o ,9 "o

37-38

35-36

27-34

15-26

12-14

9-11

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Fig. 2. Cladogramfrom Rosen (1985), showing proposed unresolved polytomies. 4i1-5 ing and articular premaxillary processes; and Rosen (1985), in another look at euteleostean (3) presence of an advanced internal division of classification that included a detailed review of the adductor mandibulae to the maxilla, Ab. the anatomy of the occipital region and rostral Fink and Weitzman (1982) convincingly reject- cartilage, listed three neoteleost synapomor- ed the latter two, based on nonhomology (mor- phies: (1) retractor dorsalis; (2) exposure of the phological) and broader taxonomic distribution exoccipitals as part of the posterior occipital (incongruence). They agreed with Rosen's eval- outline and joined with the basioccipitals by an uation of the retractor dorsalis as synapomor- inverted Y-shaped suture (and the correlated phic and proposed three additional neoteleost precervical gap); and (3) presence of an inter- synapomorphies: (2) presence of a rostral car- operculohyoid ligament. Rosen's (1985) treat- tilage; (3) Type 4 tooth attachment (Fink, 1981); ment of the interoperculohyoid ligament as a and (4) articulation of both exoccipitals and bas- neoteleost feature is puzzling; Lauder (1982, ioccipitals with the vertebral column. In a sum- 1983) and Lauder and Liem (1983) cite it as a mary of the Teleostei, Lauder and eurypterygian feature, lacking in stomiiforms. Liem (1983, fig. 14) listed as neoteleost synapo- Of the other two synapomorphies listed by Fink morphies the first three of Fink and Weitzman and Weitzman (1982), Rosen (1985) made no (1982), retractor dorsalis, rostral cartilage, and mention of Type 4 tooth attachment and re- Type 4 tooth attachment, but omitted without jected the rostral cartilage as a synapomorphy discussion the exoccipital-basioccipital verte- at this level on the basis of structural nonhomol- bral column articulation. They also added, based ogy. Hartel and Stiassny (1986) also argued con- on unpublished observations of Lauder, the vincingly, based on more extensive compari- presence of a posterior tendinous origin of ad- sons, that homologies of "rostral cartilages" ductor mandibulae section on the the Neoteleostei are AW quadrate, among highly questionable preopercle, or opercle. I can find no further and that homology of that structure as a single reference to the latter character and am unable median chondrified element bound to the pre- to evaluate it without more detailed description maxillary ascending processes by a well-devel- and documentation of its distribution. My cur- oped maxillo-rostroid ligament is unequivocal sory observations suggest substantial variation only at the acanthomorph level. in the of as is true for other sections I believe the four advanced features origin Aw following of the adductor mandibulae. (the last previously unrecognized) offer the least JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 11 ambiguous evidence for monophyly of the Neo- isosteus, some muraenid , some cyprinids, si- teleostei: luriforms), it generally has been interpreted as nonhomologous with the retractor dorsalis of I. Exoccipitals and basioccipitalsexposed posteriorly neoteleosts (for discussion and further refer- and joined byan invertedY-shaped suture. -Among ences, see Nelson, 1967, 1969). I believe that the works discussed above, only Lauder and homology of the neoteleost retractor dorsalis is Liem (1983) omitted a tripartite occipital con- corroborated by an associated modification of dyle from their list of neoteleost synapomor- the dorsal gill arch muscles of primitive neo- phies and, because they offered no justification, (stomiiforms and aulopiforms). This that omission may have been inadvertent. A modification, a shift in the insertion of the third detailed examination of this highly complex internal levator, is described below as a fourth character was beyond the scope of my study. A neoteleost specialization. comprehensive investigation of its ontogeny is needed and could provide important insight IV. Insertion of the third internal levator on thefifth have concerning homology. For the present, I upper pharyngeal toothplate.--Internal levator no reason to challenge the assessments of Rosen muscles originate on the cranium and insert on (1973) and Fink and Weitzman (1982), partic- the pharyngobranchials. Primitively, euteleosts ularly in light of Rosen's (1985) more critical have three, the first inserting on the ossified appraisal of structural homology. In the latter second pharyngobranchial, the second on the paper, Rosen suggested possible independent ossified third pharyngobranchial, and the third origin of a similar configuration below neotele- along the dorsal surface of the fourth pharyn- osts but did not reject the neoteleost configu- gobranchial cartilage (Fig. 3A). Insertion of the ration as synapomorphic. third internal levator on the fourth pharyngo- branchial cartilage characterizes all nonneotele- II. Type4 toothattachment.-Fink (1981) and Fink osts that I have examined, including those men- and Weitzman (1982) presented logical argu- tioned above that have some sort of retractor ments for the interpretation of Type 4 depress- musculature. With the advent of the neoteleost ible teeth as a neoteleostean specialization, even retractor dorsalis, however, there is a shift in though they occur in a relatively small per- the insertion of all or most of the third internal centage of neoteleosts. This type of tooth at- levator from the fourth pharyngobranchial car- tachment, in which the teeth are hinged with a tilage to the fifth upper pharyngeal toothplate posterior axis of rotation, results from sup- (Fig. 3B-C). This arrangement appears func- pression of mineralization and loss of collagen tionally effectual, because it provides for a for- from the anterior surface of the tooth ward pull on the fifth toothplate acting antag- (Fink, 1981). It characterizes juveniles of sev- onistically to the backward pull of the retractor eral primitive stomiiforms as well as adults of dorsalis on that element. Insertion of the third some others, is common in primitive eurypte- internal levator on the fifth upper pharyngeal rygians, and has been retained in a few acan- toothplate uniquely characterizes stomiiforms thopterygians. Type 4 teeth are known to occur and aulopiforms; the remaining neoteleosts among more primitive teleosts only in Esox, (ctenosquamates) lack both the third internal where parsimony and a different pulp cavity levator and fifth upper toothplate (see below). morphology indicate an independent origin. Nelson's (1967) erroneous observation that Au- lopus lacks a third internal levator probably re- III. A retractordorsalis muscle.-Of the eight syn- sulted from his failure to recognize the shift in apomorphies previously proposed for the Neo- its insertion. I interpret the shift in the insertion teleostei, there has been unanimous agreement of the third internal levator as an unequivocal about only one, the presence of a retractor dor- synapomorphy of the Neoteleostei, one that salis muscle. This muscle, extending from the lends credence to the homology of the neote- anterior vertebrae to the dorsal gill arch ele- leost retractor dorsalis. ments, is a consistent feature of neoteleosts and Fink (1984) noted the presence of a retractor is surely one of the major structural and func- dorsalis in . He cited this as evi- tional innovations in teleostean evolution. Al- dence suggesting that Lepidogalaxias could be though musculature between the vertebral col- the of neoteleosts, although he umn and dorsal gill arch elements occurs in a pointed out other characters that conflict with few lower euteleosts (e.g., Pantodon, Amia, Lep- this hypothesis. Subsequently, Begle (1991) has 12 COPEIA, 1992, NO. 1

LI1 proposed that Lepidogalaxias is part of a mono- phyletic Osmeroidei and, thus, could not be the sister group of neoteleosts. It is worth noting, in this regard, that Lepidogalaxias, unlike neotel- LI2 eosts, retains insertion of the third internal le- vator on the fourth pharyngobranchial carti- lage. Lack of the associated neoteleost SLI13 modification is at least consistent with an in- dependent origin of the "retractor dorsalis" of PB4 Lepidogalaxias, although it does not specifically UP4 UP5 refute the Lepidogalaxias-neoteleost hypothesis.

EURYPTERYGII

Of listed Rosen A PP2 eight synapomorphies by (1973) for his Eurypterygii (Aulopiformes + Myctophiformes + Acanthomorpha), all but one were seriously challenged by Fink and Weitz- man (1982), and most were rejected convinc- L11 ingly. Nonetheless, these authors accepted the LL13 monophyly of Rosen's Eurypterygii, diagnos- able the of a fused to PB2Ilh UP4 by presence toothplate the third epibranchial. They also allowed that Rosen's seventh character, reduction of the sec- ond preural neural spine to a half spine, might be diagnostic and added a eurypterygian syna- pomorphy described by Lauder (1982, 1983) P04 UP4 UPS but erroneously attributed by Fink and Weitz- man (1982) to Lauder (1981), presence of an bb td ,d 0 interoperculohyoid ligament (inappropriately listed by Rosen [1985] as a neoteleostean syn- P4P2P apomorphy and erroneously attributed to Lauder and Liem [1983]). Lauder and Liem (1983), largely following Fink and Weitzman (1982), showed four eury- pterygian synapomorphies on their cladogram: (1) reduction of the second preural neural spine to a half spine; (2) replacement of the mandibu- lohyoid ligament with an interoperculohyoid dC7 UP5 ligament; (3) fusion of a toothplate to the third epibranchial; and (4) retractor dorsalis with a RD tendinous insertion on the third pharyngo- branchial. No explanation of the fourth char- P84 acter was given, and Rosen's (1973) illustrations and my own observations indicate that it is not diagnostic for eurypterygians. In some aulopi- "UPS form genera (e.g., Aulopus, Trachinocephalus),the retractor dorsalis has direct muscular insertion

Fig. 3. Pharyngobranchials(PB) 2-4 with tooth- plates, showingupper pharyngealtoothplates (UP) 4- 5, internal levators (LI) 1-3, and retractor dorsalis 128.5 mm SL; (B) Aulopusjaponicus, AMNH 28635, (RD), right side, medial and ventral views; stippling 97 mm SL; (C) Maurolicusmulleri, USNM 302396, denotes cartilage.(A) Argentina striata, USNM 188212, 41.8 mm SL. JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 13 on the third pharyngobranchial, and in others anatomy and phylogeny of fishes. Nonetheless, (e.g., Synodus, Lestidium), it has no insertion of the 1985 paper exists, with its shortcomings, any type on that bone. The validity of a reduced and because I disagree with the conclusions, I, neural spine on the second preural as a eurypte- have no choice but to explain why. rygian synapomorphy is also suspect, given its A major part of the problem with Rosen's widespread occurrence among preneoteleosts (1985) analysis is that many characters are sub- (C. Patterson, pers. comm.). A somewhat short- stantially more variable than indicated by their ened NPU2 characterizes some of the most distribution on the cladogram. This is not unique primitive teleosts such as Pholidophorus,Leptole- to the 1985 paper (true also of Rosen, 1973), pis, and Tharsis (Patterson and Rosen, 1977, figs. but in the 1985 paper, the confusion is aggra- 31, 33, 35). Furthermore, a bladelike half-spine vated by a lack of systematic treatment of pre- much like that seen in eurypterygians occurs in viously accepted, and subsequently unchal- the fossil elopocephalan Anaethalion (Patterson lenged, synapomorphies, the use of nebulous and Rosen, 1977, figs. 39, 41-44), in Elops (Mo- taxonomic groupings (e.g., "aulopoids" and nod, 1968, figs. 20-24), in the fossil salmoni- "chlorophthalmids"), and by a number of in- forms Gaudryella and Humbertia (Patterson, ternal inconsistencies in the text. For example, 1970, figs. 13, 14, 27), and in primitive osme- "aulopoids" (said to include at least Aulopus, roids (Patterson, 1970, figs. 42, 43). but, for no cited reasons, also possibly bathy- Rosen (1985) rejected the monophyly of his saurids, bathypteroids, and ipnopids, but not (1973) Aulopiformes and Myctophiformes, Chlorophthalmus)are hypothesized as the sister placing the alepisauroids in an unresolved tri- group of ctenosquamates based on nine synapo- chotomy with stomiiforms and the remaining morphies, none of which is discussed and all of eurypterygians, within which there was also un- which I believe are problematic. certainty about the placement of neoscopelids, In the following listing of these characters, I "chlorophthalmids" and "aulopoids" in rela- briefly note the problems associated with their tion to the ctenosquamates (Fig. 2). A conse- interpretation as synapomorphic at this level: quence of this new proposal, not adequately dis- (1) high-set pectorals and (2) subthoracic pelvics cussed by Rosen (1985), is that the monophyly (characters of degree, both variable among au- of his (1973) Eurypterygii is also rejected. Rosen lopiforms and showing advanced states in some (1985) suggested that a new Eurypterygii would alepisauroids; e.g., synodontids, where they are "come to include the Ctenosquamata and per- about equivalent in position to those of many haps the Chlorophthalmidae and some aulo- myctophiforms); (3) ctenoid scales (true ctenoid poids." However he did not explicitly elaborate scales [sensu Johnson 1984] occur only among his reasons for excluding the alepisauroids and percomorphs; the serrate or spiny scales that made no mention of the characters cited in characterize Aulopus also characterize Chloroph- Lauder and Liem (1983) as diagnostic of the old thalmus, are present among myctophiforms only Eurypterygii, nor of the unique configuration in the neoscopelid Solivomerand the myctophids of the dorsal-gill arch elements that he de- Notoscopelusand a few species of Myctophum[see scribed (Rosen, 1973) as evidence for mono- Johnson, 1982] and have a spotty distribution phyly of the Aulopiformes. among acanthomorphs; spiny scales are found Although Rosen (1985) provided an insight- also among stomiiforms, e.g., Chauliodus and ful review of occipital anatomy and its bearing ostariophysans); (4) three or fewer supraneurals on the monophyly of the Neoteleostei, he seems (three or fewer characterize many stomiiforms, to have brought, in that paper, more confusion and most aulopiforms, including many alepi- than resolution to the problem of eurypterygian sauroids); (5) reduced spine on NPU2 (a euryp- limits and intrarelationships. I find myself in the terygian synapomorphy in Rosen [1973], Fink awkward position of having to criticize a paper and Weitzman [1982], and Lauder and Liem that was written at a time when Rosen was se- [1983] characterizes all aulopiforms, including riously ill, and, as Patterson has pointed out alepisauroids; treated elsewhere by Rosen [1985] (Rosen and Patterson, 1990), the thoroughness as a synapomorphy of "osmeroids" and neote- with which he could approach a problem was leosts, see below); (6) derived premaxillary mor- understandably limited. In so doing, in no way phology (not described, but presumably the form do I intend to demean Rosen's seminal and pro- of the symphyseal or ascending process; Stiassny digious contribution to our knowledge of the [1986] concluded that homologies of the ele- 14 COPEIA, 1992, NO. 1 vation medial to the articular process on the alluded to its "phylogenetic reality" in her in- premaxillae of various nonacanthomorphs are troduction. not clear); (7) type of retractor dorsalis (not de- I conclude from all of this, and from my ad- scribed); (8) toothplate fused to third epibran- ditional observations, that the monophyly of the chial (present in most alepisauroids and treated Eurypterygii, as originally conceived by Rosen as a eurypterygian synapomorphy by Rosen (1973), has not been challenged seriously and [1973], Fink and Weitzman [1982], and Lauder that it is supported by three synapomorphies, and Liem [1983]); and (9) median rostral carti- one of which has not been previously recog- lage (homologies of rostral structures among nized as such. aulopiforms and myctophiforms rejected by Hartel and Stiassny [1985]). Having listed those V. A toothplatefused to the third epibranchial.-A nine synapomorphies of "aulopoids" and cten- fused third epibranchial toothplate (EB3TP) is osquamates, Rosen (1985), without further dis- unique to eurypterygians, though not univer- cussion, listed only three of them in his final sally present within the clade. Absence of the "synapomorphy scheme": median rostral car- EB3TP in some myctophids is most parsimo- tilage, subthoracic pelvics, and three supra- niously interpreted as reversal. The same is true neurals. The remaining six were either not for its absence in only some members of the mentioned at all or listed as synapomorphies at alepisauroid families Paralepididae (including other levels. This represents only one example Anotopterus), Evermanellidae, and Synodonti- of numerous discrepancies that cast doubt on dae and in the highly derived and closely related the validity of Rosen's (1985) hypotheses and, Alepisaurus and Omosudis. Loss of the EB3TP is at the very least, make them extremely difficult also common among percomorphs (Johnson, to evaluate. 1981, 1984). Stiassny (1986) agreed with Rosen's proposal that neither the Aulopoidei nor the Aulopi- VI. Presence of an interoperculohyoidligament.- formes of Rosen (1973) are monophyletic, but My cursory observations support those of Lau- for different reasons. She placed a group of der (1982, 1983) that a shift in insertion of the aulopoids, specifically Aulopus, Chlorophthalmus, mandibulohyoid ligament to the interopercle and Parasudis, as the sister group of the Cteno- (i.e., the advent of an interoperculohyoid liga- based on their possession of an ele- ment) diagnoses the Eurypterygii, but I have vated and reoriented cranial condyle of the head not done an exhaustive survey, nor did Lauder. of the maxilla and the concomitant exposure of a maxillary saddle for the reception of a "pal- VII. Fusion of the ventral half of the medial pelvic atine prong" on the head of the palatine. Like ray to the medial pelvic radial.-Gosline (1961) Rosen (1985), Stiassny did not mention the dis- described a specialized feature of the pelvic fin, tinctive configuration of the dorsal gill arch el- fusion of the innermost radial with the ventral ements used by Rosen (1973) to defend aulopi- half of the innermost pelvic ray, and noted that form monophyly. That unique configuration it characterizes the great majority of "inio- involves lateral displacement of the second pha- mous" fishes. He also observed this condition ryngobranchial, concomitant elongation of the in Aphredoderus, Percopsis, Holocentrus, Chriodo- uncinate process of the second epibranchial, and rus, and Ablennes and interpreted this as evi- (not noted by Rosen, 1973) absence of a carti- dence of an iniomous derivation for the orders laginous condyle on the third pharyngo- , , and Beloni- branchial for articulation of the second epi- formes. Because he observed some variability branchial; it is obviously a fairly complex (two exceptions among inioms, Alepisaurus and specializaiton that is unlikely to have arisen in- Bathypterois,see discussion below) and had done dependently, as would be the case if aulopiforms only a very cursory survey among other groups, are not monophyletic. Stiassny's (1986) hypoth- and because this feature was not "of any great esis is also at odds with that of Johnson et al. structural importance," Gosline (1961) be- (1989), which places Aulopus as the sister group lieved it "inadvisable to push too far the infer- of the synodontoids. It does not, however, chal- ence that can be drawn . . . regarding genetic lenge the monophyly of Rosen's (1973) original relationships." Gosline et al. (1966) described Eurypterygii, and consequently, Stiassny (1986) this character as one of several that distinguish- did not discuss evidence, pro or con, relating to es the Iniomi from isospondylous fishes, but the integrity of that assemblage, although she Gosline (1971) did not mention it in his work JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 15

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imm1 mm

D

Fig. 4. Pelvic girdle (G), radials(L, lateral; M, medial), and fin rays (D, dorsal half; V, ventral half; V+M, ventral half fused with medial radial; S, splint); left side, ventral views; ventral halves of all except medial- most fin ray removed: (A) Argentina striata, USNM 188224, 127 mm SL; (B) Percopsis omiscomaycus,USNM 179711, 84.5 mm SL. on functional morphology and teleostean clas- in pholidophorids (C. Patterson, pers. comm.), sification, nor has it been considered in any sub- elopiforms, clupeomorphs (where it is often sequent treatment of teleostean relationships. more irregularly shaped), and lower euteleosts. My observations indicate that this feature is a Among euteleosts, it occurs in at least some synapomorphy of the Eurypterygii, and I de- ostariophysans (both in anotophysans and oto- scribe it in more detail below. physans), argentinoids (Fig. 4A), osmeroids, Primitively in teleosts, there are three autog- salmonoids (Fig. 5A), and stomiiforms but not enous radials at the posterior margin of each in esocoids, where there are no separate pelvic half of the pelvic girdle with which the pelvic- radials and the pelvic rays articulate directly fin rays articulate (Figs. 4A, 5A). The medial with the cartilaginous posterior margin of the radial is the largest and has a configuration that pelvic girdle (this is presumably a secondary differs substantially from that of the other two condition, but I have not attempted to assess basically ovoid elements. It consists of an ossi- it). Although stomiiforms exhibit reductive fied, posteriorly tapering cone with a cartilag- trends in the morphology of the medial pelvic inous bulb or articular surface anteriorly. This radial, including its complete absence, the os- distinctive larger medial radial also is present sified protracted cone or commalike configu- in more primitive actinopterygians, where there ration characterizes primitive members of the are more than three radials (e.g., Amia, Good- major stomiiform groups; sternoptychids (e.g., rich, 1930, fig. 206; and paleoniscoids, Gardi- Thorophos,Weitzman, 1974, fig. 105), stomiids ner, 1984, fig. 138), and it has been suggested (e.g., Neonesthes, Fink, 1985, fig. 161), and gon- (Stensio, 1921; Rosen et al., 1981; Gardiner, ostomatids (e.g., Diplophos, Fink and Weitzman, 1984) that it may represent a metapterygial el- 1982, fig. 20). ement. Most frequently in teleosts, this medial In noneurypterygian euteleosts, the distinc- radial is somewhat protracted and is slightly bent tive medial radial always remains fully autoge- near midlength, such that the posterior portion nous (Figs. 4A, 5A), although in some groups lies approximately parallel to the shaft of the (e.g., salmonids, osmerids, argentinoids), the medial pelvic ray, its overall shape more or less ventral half of the medial one or two pelvic rays resembling that of an inflated comma. An os- may be firmly attached to it by connective tissue. sified medial pelvic radial with this configura- However, in all aulopiforms (Figs. 5B, 6A), ex- tion is lacking in osteoglossomorphs but present cept the Ipnopidae (including bathypteroids), in 16 COPEIA, 1992, NO. 1

A ... B C

V+M1 M -V+M V D

T1mm

D E F

V•• mm v*MT T 1mm 1mm 1mm SI I

Fig. 5. Medial-mostpelvic-fin ray (D, dorsal half; V, ventral half; V+M, ventral half fused with medial radial),radials (L, lateral;M, medial),and girdle margin (G);left side, ventralviews: (A) Salmosalar, SU 49265, 78.3 mm SL; (B) Parasudis truculentus, USNM 159850, 96.1 mm SL; (C) Neoscopelus macrolepidotus,AMNH 49533, 100.5 mm SL; (D) Setarchesguentheri, USNM 157704, 57.6 mm SL; (E) Pronotogrammusaureorubens, USNM 185228, 65.7 mm SL; (F) Menidiaberyllina, USNM 200735, 53.0 mm SL.

all myctophiforms (Fig. 5C), and in most acan- characterizes some beryciforms (e.g., holocen- thomorphs (Figs. 4B, 5D-F, 6B), the medial ra- trids and berycids), which also have two ossified dial fuses to the proximal end of the ventral lateral radials, and in other beryciforms (e.g., half of the medial pelvic ray early in ontogeny. trachichthyoids), where the two lateral radials In its most privitive embodiment, as seen in au- are lacking, the lateral process on the ventral lopiforms, myctophiforms, , and per- ray is smaller. The latter condition is found copsiforms (Fig. 4B), the coalesced medial radial among stephanoberycoids (e.g., melamphaeids, remains large, and the ventral half of the medial Barbourisia, Gibberichthys),but in Rondeletia and ray is, consequently, somewhat reminiscent of Stephanoberyxa free medial radial is embraced a golf club. In these groups the two primary by the bases of the medial ray. If this free radial lateral radials are also well developed, and in is the homolog of that present in noneurypteryg- some taxa, there may be an additional lateral ians, rather than a neomorph, this is the only radial associated with the lateral most ray. instance of reversal of medial radial fusion I have done a broad, but not yet exhaustive, among acanthomorphs of which I am aware. survey of this ventral ray/medial radial fusion In most percomorphs (Fig. 5D-E) and ath- among acanthomorphs; it is widespread and un- erinomorphs (Fig. 5F), wherein the two lateral doubtedly primitive for the group. Within ac- radials are extremely reduced or more com- anthopterygians, the primitive golf-club form monly absent, the coalesced medial radial is also JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 17

1mm

D D

ST GG

Imm

V+M

Fig. 6. Medial-mostpelvic-fin ray (D, dorsal half; V, ventral half; V+M, ventral half fused with medial radial),radials (lateral, L; medial, M), and girdle margin (G), developing; left side, ventral views: (A) Synodus sp., left, USNM 315317, 27.0 mm SL, right, USNM 315318, 79.2 mm SL; (B) Moroneamericana, USNM 315315, left to right, 16.2 mm SL, 17.8 mm SL, 28.1 mm SL. much reduced and may be detectable only as a trachinoids, notothenioids, blennioids (includ- small, cartilage-tipped bony prominence or car- ing tripterygiids), gobioids (including Rhyaci- tilaginous nubbin on the lateral side of the prox- chthys),acanthuroids, scombroids, stromateoids, imal tip of the ventral ray half. Nonetheless, the and anabantoids. Where the cartilage-tipped origin of this structure can be seen in larval process is lacking in perciforms (e.g., in many specimens to be the result of ontogenetic fusion blennioids, gobioids, the labroid family Labri- of the initially elongate cartilaginous medial ra- dae), the medial radial is also lacking, suggesting dial to the ray tip (Fig. 6B). I have found such that this secondary condition, which is not struc- a modified ventral ray half in the pelvic fin of turally homologous with that in noneuryptery- most percoids and in at least some labroids, gians, arose through reduction of the fused ra- 18 COPEIA, 1992, NO. 1

dial process rather than through paedomorphic dorsal gill arch evidence for monophyly of the truncation (i.e., failure of the radial to fuse in Aulopiformes, discussed above. Subsequent ontogeny). Among scorpaeniforms, the modi- work by Sulak (1977) and Johnson (1982) also fied medial pelvic ray characterizes anoplo- placed ipnopids as close relatives of other au- pomatids, hexagrammids, and at least some lopiform subgroups, all of which have a fused scorpaenoids (Fig. 5D), and platycephaloids; medial radial. however, I have not found it in cottoids except Fusion of the medial pelvic radial to the ven- in the problematic Normanichthys(which prob- tral half of the medial pelvic ray apparently has ably is not a scorpaeniform). It is lacking in most occurred independently once among noneury- pleuronectiforms but well developed in the pterygians in a few, though not all, New Zealand primitive Psettodes. species of , as reported by Weitzman The distribution of this character in paracan- (1967). My observations confirm those of Weitz- thopterygians is interesting and merits further man concerning Galaxias but are contrary to his investigation. In percopsiforms (Fig. 4B), there statement that this fusion also characterizes is a cartilage-tipped, golf-club-like ventral ray Elops; I found the medial pelvic radial to be half much like that of aulopiforms and myc- autogenous in larval, juvenile, and adult Elops. tophiforms and three well-developed lateral ra- dials. All other paracanthopterygians (Anacan- CTENOSQUAMATA thini, sensu Patterson and Rosen, 1989) examined show no evidence of ventral ray/me- Of the three major clades under considera- dial radial fusion and either have no pelvic ra- tion here, the Ctenosquamata (Myctophiformes dials (gadiforms and ophidiiforms, all pelvic rays + Acanthomorpha) has received the least at- articulate directly with cartilaginous margin of tention. Rosen (1973) listed 10 synapomorphies girdle) or have one to several cartilaginous ra- that purportedly unite myctophiforms and dials (batrachoidiforms and lophiiforms). Ab- acanthomorphs. Fink and Weitzman (1982) did sence of ventral ray/medial radial fusion is pre- not consider ctenosquamate monophyly. Lau- sumably secondary, because the other option der and Liem (1983, fig. 14) showed only two requires a noneurypterygian origin for these synapomorphies at the ctenosquamate node, one groups. Consequently, it has no bearing on the comprising two of the 10 listed by Rosen (1973) tenuous monophyly of the and an additional one described by Lauder but could be interpreted as an additional apo- (1982). The latter, a pharyngohyoideus muscle morphy of the Anacanthini. inserting on the urohyal, was said by Lauder As for exceptions among primitive eurypte- and Liem to have been found in some aulopi- rygians, specifically aulopiforms, Gosline's forms, casting doubt on its validity as a cteno- (1961) observation that the medial radial is free squamate specialization; I have not attempted in Alepisaurus was apparently based on a young to evaluate this observation. Lauder and Liem specimen; ossification and fusion of the medial (1983) did not discuss their reasons for exclud- radial to the ventral half of the medial ray is ing the remaining eight synapomorphies in Ro- delayed ontogenetically in Alepisaurus and the sen's original list, although for many of them, closely related Omosudis as compared to other the reasons are obvious. aulopiforms, but the fusion is complete in large There are varying degrees of ambiguity as- specimens. (In light of this, I examined large sociated with all 10 of Rosen's (1973) ctenosqua- specimens of salmonids and other noneurypte- mate synapomorphies; they either are not rygians to confirm that the medial radial re- unique to ctenosquamates, are variable within mains autogenous throughout development, even primitive ctenosquamates, or both. The even though firmly attached to the ventral ray last five in his list are the least convincing. For half in some.) Gosline (1961) also noted that the some of these (e.g., "ctenoid" scales, dorsal-fin ipnopid Bathypteroisretains a free medial radial, "spines"), there remain questions of homology and I have confirmed this for that genus and on morphological grounds. More important, Ipnops. Ipnopids possess the three other euryp- none of them characterizes all myctophiforms, terygian synapomorphies, and thus the lack of and most are found in only a few species of medial radial fusion is either a reversal or places myctophids; some are also variously present them as the sister group of all other eurypterygi- among primitive acanthomorphs. As Rosen ans. Reversal seems most likely, because the lat- (1973) himself observed with regard to the sub- ter hypothesis is at odds with the convincing ocular shelf, "perhaps we are seeing no more JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 19 than a proclivity to develop this structure in a single division inserting on UP5. Further- both groups." more, emphasis on insertion of the retractor Rosen's other five putative synapomorphies dorsalis on PB3 is far from universal among warrant more extensive discussion: ctenosquamates; many acanthomorphs have a (1) Reduction of the posterior upper pharyn- single retractor dorsalis bundle inserting on both geal dentition and formation of a hinge joint PB3 and UP4. between the fourth upper pharyngeal tooth- (4) A hinge joint between the toothplates of plate (UP4) and the toothplate of the third pha- the second epibranchial (EB2) and pharyngo- ryngobranchial (PB3). Rosen (1973) was con- branchial (PB2). Rosen (1973) did not discuss fused about homology and presence or absence or present any further description of this fea- of the fourth and fifth upper toothplates, and ture, and I find his characterization oversim- thus his interpretation of posterior toothplate plified. Many percoids have a single, large, au- reduction and articulation is flawed. As de- togenous, ovoid toothplate at the anterior end scribed below, the critical feature is not the dim- of EB2 that articulates with the cartilaginous inution of the posterior pharyngeal dentition posterior tip of PB2, frequently contacting the but the unique absence of the fifth upper tooth- fused toothplate of the latter (see Rosen's [1973] plate (UP5). An overlapping, hingelike articu- illustrations of Centropomus,fig. 93, and Caranx, lation between UP4 and the toothplate of PB3 fig. 97). A similar condition is found in some (undoubtedly associated with the loss of UP5) beryciforms, whereas others have a series of is somewhat difficult to characterize unambig- small toothplates along the anterior portion of uously and is variable, even among primitive EB2 or lack toothplates there altogether as do ctenosquamates. Within myctophiforms, for ex- many percomorphs, paracanthopterygians, and ample, Neoscopelushas a broad shelf on UP4 that atherinomorphs. Neoscopelids have a single overlaps the toothplate of PB3 ventrally, where- large toothplate on EB2, similar to, but more as in Diaphus there is no contact of any kind asymmetrical than, that of percoids, but it does between UP4 and PB3. not form a "hinge-joint" with the fused tooth- (2) Reduction of the fourth pharyngo- plate of PB2, nor does the smaller second epi- branchial cartilage (PB4). Here again, there is branchial toothplate of myctophids, which shows a trend toward a smaller PB4, but its size is more considerable variation in shape and size and fre- variable than implied by Rosen (1973). As is quently does not even reach the anterior tip of clear in Rosen's (1973) illustrations, there is not EB2. If any generalization can be made, it is, an unequivocal reduction in size at the cteno- perhaps, that flattened, autogenous toothplates squamate node. In myctophids and neoscope- apparently do not occur on EB2 below the lids, PB4 is substantially shortened compared Ctenosquamata. to most aulopiforms, but most synodontoids have (5) Further reduction of the second preural a comparably reduced PB4, and in numerous neural spine to a low crest and extension of the acanthomorphs (e.g., Polymixia, Percopsis, Veli- first epural over it. Rosen (1985) later ques- fer, Caranx), this cartilage is considerably larger tioned the wisdom of basing "major taxonomic than it is in myctophiforms. judgements" on the length of NPU2, and the (3) A separate internal division of the retrac- extreme variability in this and the position of tor dorsalis inserting on the third pharyngo- the first epural are obvious in his earlier mon- branchial (PB3). There is a general trend to- tage of the epural-uroneural complex (Rosen, ward insertion of the retractor dorsalis more 1984, figs. 35-37). anteriorly, but substantial variation in its inser- Although I view all of Rosen's (1973) cteno- tion exists, and this is evident in Rosen's (1973) squamate synapomorphies as problematic, I ar- illustrations. Most aulopiforms have little or no gue below that monophyly of the Ctenosqua- insertion of the retractor dorsalis on PB3, how- mata is supported by a reductive restructuring ever in Aulopus (Rosen's fig. 4), a major portion of the dorsal gill arches that uniquely charac- inserts on PB3, and a separate division inserting terizes all members of the clade. For this and on PB3 occurs in Scopelarchoides (Rosen's fig. other reasons, I disagree with Rosen's later 13). Within synodontoids there is a large inter- (1985) exclusion of the Neoscopelidae from the nal division inserting along much of the length Ctenosquamata (Fig. 2). In the preceding sec- of PB3 in Saurida and Harpadon (not shown in tion on the Eurypterygii, I explained how Rosen Rosen's fig. 8), whereas the closely related Tra- (1985) challenged the monophyly of his (1973) chinocephalus and Synodus (Rosen's fig. 7) have Myctophiformes (Myctophidae + Neoscopeli- 20 COPEIA, 1992, NO. 1

dae), proposing instead that myctophids alone though it is true that neoscopelids have a large are the sister group of acanthomorphs and plac- cervical gap, Rosen's statement (p. 13) that they ing neoscopelids in an unresolved polytomy also have an accessory neural arch is erroneous; immediately preceding the newly restricted my observations indicate that all three neos- Ctenosquamata together with two loosely de- copelid genera lack an accessory neural arch. fined groups, "chlorophthalmids" and "aulo- Oddly, Rosen (1985) himself noted that the poids." I discussed some specific examples of, structure that Rosen and Patterson (1969, fig. the myriad problems associated with Rosen's 61 A) labeled as an accessory neural arch in Neos- character analysis, most of which relate to ques- copeluswas actually the first of four supraneurals tions of structural homology and substantially but did not elaborate further on his conviction greater variability in character states than in- that neoscopelids have an accessory neural arch. dicated in the character analysis and cladogram. An interarcual cartilage occurs in only a few Here, I will briefly touch upon additional prob- myctophid species, and among primitive acan- lems of a similar nature. thomorphs only in anomalopids and a few me- Rosen's (1985) proposal of an unresolved lamphaeids, and in none of these groups does polytomy below ctenosquamates is puzzling it resemble the rodlike structure that charac- in light of his synapomorphy scheme. Although terizes more advanced acanthomorphs. Num- his cladogram (Rosen, 1985, fig. 45) shows 12 ber of supraneural ("predorsal") bones is quite synapomorphies at this unresolved node, the variable among aulopiforms, and three or fewer synapomorphy scheme indicates that, of these, is common. As for the rostral cartilage, I invoke neoscopelids share eight with ctenosquamates, again the persuasive arguments of Hartel and whereas "aulopoids" share only three and Stiassny (1986) that homology of the rostral car- "chlorophthalmids" only one. Thus, even if one tilage is unclear below acanthomorphs, wherein accepts Rosen's highly problematic character the configuration has stabilized to a single me- interpretations and analysis, his putative poly- dian chondrified cartilage strongly bound to the tomy is fully resolved on a parsimony basis, premaxillary ascending processes by well-de- and his original Ctenosquamata remains intact. veloped maxillo-rostral ligaments. This is not to suggest that Rosen's (1985) new Stiassny (1986) described four putative syn- character evidence for ctenosquamate mono- apomorphies of myctophids and neoscopelids, phyly is any less ambiguous than that of the corroborating Rosen's original (1973) Myc- 1973 paper discussed above, only that the prem- tophiformes and thus conflicting with Rosen's ise that "aulopoids" or "chlorophthalmids" may (1985) myctophid-acanthomorph synapomor- be more closely related to ctenosquamates than phies of which all but the subocular shelf appear neoscopelids is not logically defended. equivocal. I agree with Stiassny's assessment of Rosen (1985) further argued against a sister the conelike parapophyses on the first vertebra group relationship between myctophids and but have not attempted to evaluate her other neoscopelids based on eight putative synapo- three characters, which involve rostral liga- morphies of myctophids and acanthomorphs, ments and subtleties in the configuration of the all purportedly lacking in neoscopelids. Al- head of the maxilla that I find difficult to in- though this would not necessarily challenge terpret. ctenosquamate monophyly (neoscopelids need The question of monophyly of the Myctophi- not be excluded from ctenosquamates if they formes remains somewhat problematic; how- are the sister group of myctophids + acantho- ever, I suspect that Stiassny's corroboration of morphs), it warrants discussion. Of the eight Rosen's (1973) original hypothesis is valid. As putative myctophid-acanthomorph synapomor- for ctenosquamate monophyly, the evidence phies, presence of a well-developed subocular presented to date is inconclusive. Nonetheless, shelf is the least ambiguous. The others are too I maintain that the Ctenosquamata, as originally variable to be considered unequivocally synapo- delineated by Rosen (1973), is monophyletic, morphic at this level. Rosen's use of partial clo- based on a fundamental reductive restructuring sure of the cervical gap, absence of an accessory of the dorsal gill arches that has gone unrec- neural arch, and the associated modifications as ognized as unique among euteleosts to neosco- synapomorphies that unite myctophids and pelids, myctophids, and acanthomorphs. It may acanthomorphs is particularly disconcerting be that certain features of the dorsal gill arches given the extreme variability among these fea- interpreted by Rosen (1973) as ctenosquamate tures within aulopiforms. Furthermore, al- synapomorphies (discussed above) are correlat- JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 21 ed with this restructuring. A comprehensive posterior toothplates but saw no clear resolu- parsimony analysis could demonstrate that some tion. Accordingly, he stated, "The loss of the of these features, though variable, are inter- fourth and fifth toothplates is a character of pretable as ctenosquamate synapomorphies, but possible systematic significance, but so far not only the specialization described below is unique sufficiently understood," and it appeared to him to and unreversed within the Ctenosquamata. that "the fourth and fifth plates seem indepen- dently to have been lost many times." I agree VIII. Absenceof thefifth upper pharyngeal toothplate with Nelson (1969) that the fourth upper pha- and the associated third internal levator muscle.- ryngeal toothplate has been lost independently The primitive complement of upper pharyngeal many times within both nonctenosquamates and toothplates among euteleosts is four (Fig. 3B), ctenosquamates; however, I believe that the fifth one fused to the ossified second pharyngo- upper pharyngeal toothplate has been lost only branchial, one fused to the ossified third pha- once in the evolution of euteleosts, in the com- ryngobranchial, one (UP4) associated with the mon ancestor of ctenosquamates. This convic- cartilaginous fourth pharyngobranchial, and tion follows from resolution of the long-stand- one (UP5) variously associated with, but rot ing homology problem relating to identity of fused with, the fourth epibranchial. There is UP4 and UP5. Close scrutiny provides unam- some question regarding the origin of UP5; biguous evidence that the single toothplate pre- Weitzman (1967) suggested that it might have viously identified as UP4 in nonctenosquamate been derived, along with UP4, from the dermal- fishes is actually UP5. element series of the fourth, rather than the Rosen (1973) diagnosed one of his two au- fifth, arch, and Nelson (1969) discussed the dif- lopiform subgroups, the alepisauroids, on the ficulties associated with determining this. The basis of several specializations of the dorsal gill actual origin of this element need not concern arch elements, including absence of the fifth us here, so long as it is understood that, among upper pharyngeal toothplate and concomitant euteleosts, UP5 refers to the homolog of the enlargement of UP4 (see his figs. 7-16). As separate toothplate that lies posterior to UP4, pointed out by Johnson (1982), Rosen's obser- whether or not UP4 is present. vations and illustrations indicating a single pos- Many euteleosts have only a single toothplate terior upper pharyngeal toothpl'ate in most posterior to the third pharyngobranchial (Figs. alepisauroids were erroneous. With the excep- 3C, 7), one of the posterior ones having been tion of synodontoids (Pseudotrichonotus,Synodus, lost, and there has been categorical confusion Trachinocephalus, Saurida, and Harpadon) and regarding the identity of the remaining tooth- Anotopterus, all aulopiforms have two posterior plate in various groups. All ctenosquamates have toothplates (Johnson [1982] reported that Alepi- a single posterior toothplate that has been iden- saurus has a single toothplate, but my specimens tified, correctly I believe, as UP4 (Fig. 7B-D). clearly have two). In alepisauroids, however, un- The single posterior toothplate that character- like aulopoids, the more anterior of the two, izes many nonctenosquamates (Figs. 3C, 7A) also UP4, is usually quite small, and in some species has been identified most frequently as UP4, in- (e.g., Coccorellaatrata, Johnson [1982, fig. 15A]) dicating (incorrectly, as I will argue below) that is edentulous. Rosen (1973) apparently missed UP5 is lacking in these groups. For example, the small UP4 in most alepisauroids, assumed Weitzman (1967) observed that the fifth upper that UP5 had been lost, and interpreted the pharyngeal toothplate was missing in all eso- large UP5 as UP4. Because UP4 is substantially coids, osmeroids, salmonids, stomiiforms, and reduced among those alepisauroids having two synodontids that he examined. The following toothplates, it seems reasonable that the re- illustrations of dorsal gill arch elements of var- maining toothplate in synodontoids and Anotop- ious nonctenosquamate fishes have the single terus is UP5, not UP4 as previously thought. I posterior toothplate labeled UP4: Rosen (1973), extend this hypothesis to include all noncten- figs. 5 (salmonid), 7-8 (synodontids), 17 (gigan- osquamates with a single posterior toothplate turid), 18-22 (stomiiforms), 58 (umbrid); Rosen and maintain that it is corroborated by two in- (1974), fig. 15A (umbrid); Weitzman (1974), figs. dependent lines of evidence establishing the 76, 78 (sternoptychids), 79 (osmerid); Lauder identity of each toothplate: ontogeny and as- (1983), fig. 2B (esocid). sociated musculature. Nelson (1969) recognized and discussed po- Ontogeny: Examination of developing dorsal tential confusion about the identity of the two gill arch elements (Fig. 8) affords a clear ex- 22 COPEIA, 1992, NO. 1

L12

L13 L12 PB4 LI1 RD A PB2 . ... UP4 .-. R - B :PI4 PB2 PB3 PB4 UP PB3

UP4UP

PB2

PUP4

PB2 PB4 PB4 UP4 RDD .UP4 P13 P83 P4 PB is R P132 $ 40 D P83_ _ UP4 %,~~?N-"A?7i: ,P PP34

UP4

0 P

Fig. 7. Pharyngobranchials(PB) 2-4 with fused toothplates, showing upper pharyngeal toothplates (UP) 4-5, internal levators (LI) 1-3, and retractor dorsalis (RD); right side, medial and ventral views; stippling denotes cartilage:(A) Trachinocephalusmyops, USNM 185861, 124 mm SL; (B) Diaphusmollis, AMNH 29449, 38.8 mm SL; (C) Solivomerarenidens, USNM 135419, 110 mm SL; (D) Moroneamericana, USNM 109851, 44.5 mm SL.

position of posterior toothplate homology. At posterior toothplates in those taxa having both their initial appearance in early development permits positive identification of the remaining the fourth and fifth upper pharyngeal tooth- element in taxa with only one. Using these cri- plates evince specific positional relationships teria, UP5 is present in all nonctenosquamates with respect to the fourth pharyngobranchial examined; in taxa with a single posterior tooth- cartilage and the fourth epibranchial (EB4). plate (Fig. 8B), that element appears initially Among taxa possessing both toothplates, UP4 at the tip of EB4, and the ventral surface of PB4 consistently appears on the ventral surface of is vacant until UP5 grows forward to cover it. PB4, whereas UP5 appears at the distal tip of In contrast, all ctenosquamates lack UP5, UP4 EB4 (Fig. 8A). The specific relationship be- appears initially on the ventral surface of PB4, tween UP4 and PB4 is generally obvious in and there is no toothplate associated with EB4 adults; however, UP5 frequently extends an- (Fig. 8C-D). teriorly along the ventral surface of UP4 with Internal levators: Euteleosts primitively have growth, such that its primary association with three internal levator muscles, the third insert- EB4 may be obscured (e.g., Figs. 3C, 7A). An- ing on the fourth pharyngobranchial cartilage terior expansion of UP5 occurs most commonly in nonneoteleosts (Fig. 3A) and shifting to the where UP4 is reduced or absent, and this has fifth upper pharyngeal toothplate in neoteleosts substantially confounded the UP4-UP5 ho- (Fig. 3B), with the advent of the retractor dor- mology problem. Knowledge of the early on- salis. The first two internal levators insert on togenetic positional relationships of the two the second and third pharyngobranchials, re- JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 23

PB3 E4

A **. PB4 - ----lmm UP4 -----UP5

lmm

D UP4

O .. ... up .5mm UP4

Fig. 8. Selected dorsal gill arch elements at early stage of development, right side, medial views, showing pharyngobranchials(PB) 3-4, upper pharyngeal toothplates (UP) 4-5, epibranchial(E) 4; stippling denotes cartilage:(A) Scopelarchussp., USNM 315316, 28 mm SL; (B) Synodussp., USNM 315317, 22.5 mm SL; (C) Symbolophoruscaliforniense, USNM 315314, 16.5 mm SL; (D) Morone saxatilis, USNM 315315, upper, 7 mm SL, lower, 8.5 mm SL.

spectively, and UP4 never receives levator mus- mate fishes differ from all other euteleosts in cles. Insertion of the third internal levator on having lost UP5 and the associated third inter- UP5 in primitive neoteleosts provides a marker nal levator. As with the retractor dorsalis for for the identity of that element in taxa with a neoteleosts, this unique, fundamental structural single posterior toothplate. Using that criteri- and functional innovation is cogent evidence of on, the hypothesis that absence of UP5 is unique the monophyly of the Ctenosquamata. to ctenosquamates is corroborated, as it is with All the ontogenetic evidence. nonctenosqua- MATERIAL EXAMINED mate neoteleosts (stomiiforms and aulopiforms) have three internal levators, the third inserting Comparative observations were made on the on the posterior-most toothplate (i.e., UP5; Figs. pelvic girdle and dorsal gill arch elements in a 3C, 7A). In contrast, all myctophids, neosco- broad range of euteleosts, and a complete listing pelids, and acanthomorphs have only two in- of the hundreds of cleared and stained speci- ternal levators, the first inserting on the second mens examined would be impractical. Most are pharyngobranchial and the second on the third part of the permanent skeletal collection of the pharyngobranchial (Fig. 7B-D). Identity of the USNM; a few were borrowed from the AMNH, posterior-most toothplate as UP4 is supported FMNH, and MCZ collections. In addition to by its lack of an associated internal levator. cleared and stained specimens, whole specimens The dorsal gill arch elements of all ctenosqua- representing over 200 genera in a broad range 24 COPEIA, 1992, NO. 1 of euteleost families were dissected to examine Notograptidae (1), Opistognathidae (2), Oplegnathidae (1), Ostra- branchial musculature. In most of these dissec- coberycidae (1), Percichthyidae (6), Percidae (2), Plesiopidae (2), Po- lynemidae (1), Pomacanthidae (1), Pomatomidae (1), Priacanthidae tions, the head of each specimen was sagittally (1), Pseudochromidae (2), Rachycentridae (1), Scatophagidae (1), sectioned along the midline, continuing poste- Sciaenidae (3), Scombrolabracidae (1), Scorpididae (1), Serranidae the anterior several vertebrae. (6), Sillaginidae (1), Sparidae (1), Terapontidae (1), Toxotidae (1). riorly through Stromateoidei.-Centrolophidae (1). One-half of the head (usually the left) was then Labroidei.-Cichlidae (1), Embiotocidae (1), Labridae (1), Pomacentri- removed and stained for bone and to dae (1). cartilage .-Gasterochismatidae (1), Gempylidae (1), Istiophoridae (1), facilitate observation of muscle origins and in- Scombridae (2), Sphyraenidae (1). sertions on the dorsal gill arch elements. Less Acanthuroidei.-Acanthuridae (1), Luvaridae, Siganidae, Zanclidae. intrusive dissections were done on some Gobioidei.- (1), Eleotrididae (4), Rhyacichthyidae (1), Schin- speci- dleriidae (1), Xenisthmidae (1). mens to check only insertions of internal leva- Blennioidei.-Blenniidae (9), Chaenopsidae (2), Clinidae (2), Dactylosco- tors. pidae (1), Tripterygiidae (1), Labrisomidae (6). Callionymoidei.-Callionymidae (1). Listed below are families for which cleared Zoarcoidei.-Bathymasteridae (1), Zoarcidae (1). and stained specimens of one or more (for most Stichaeoidei.-Pholidae (1). members were examined. Numbers in Pholidichthyoidei.-Pholidichthyidae (1). families) Ammodytoidei.-Ammodytidae (1). parentheses indicate the number of genera in Trachinoidei.-Champsodontidae (1), Cheimarrichthyidae, Chiasmo- which branchial muscles were also examined. dontidae (2), Leptoscopidae, Parapercidae (1), Percophididae (3), Trachinidae (1), Trichidontidae (1), Trichnotidae (1), Uranoscopidae The taxonomic groupings are for convenient (1). reference, and no phylogenetic inferences are Notothenioidei.-Bovichthyidae, Harpgiferidae (1), Nototheniidae (1). intended. ACKNOWLEDGMENTS .-Albulidae (1), Elopidae, Megalopidae. Clupeomorpha.-Clupeidae (1), Engraulidae (1). I thank M. N. T. K. E. Esocoidei.-Esocidae (1), Umbridae (1). Feinberg, Grande, Ostariophysi.-Ariidae (1), Chanidae, Characidae (1), Cyprinidae (1). Hartel, R. K. Johnson, and M. L. J. Stiassny for Salmonoidei.- (1). assistance in borrowing specimens. C. Baldwin, Argentenoidei.-Argentinidae (1), Bathylagidae (1), Platytroctidae (1). W. L. F. Osmeroidei.-Galaxiidae (1), Lepidogalaxiidae (1), Osmeridae (1), Ple- Fink,J. Moore, C. Patterson, W. Smith- coglossidae, Retropinnidae. Vaniz, and M. L. J. Stiassny read and provided Stomiiformes.-Gonostomatidae (2), (1), Stomiidae (2). valuable comments on the cam- Ateleopoidei.-Ateleopodidae (1). manuscript. My Aulopiformes.-Alepisauridae (1), Anotopteridae, Aulopidae (1), Bathy- era lucida drawings were rendered by J. E. Tre- sauridae (1), Chlorophthalmidae (1), Evermanellidae (1), Harpadon- cartin. tidae (1), Ipnopidae (1), Notosudidae, Omosudidae, Paralepididae (1), Pseudotrichonotidae (1), Scopelarchidae (1), Synodontidae (2). Myctophiformes.-Myctophidae (3), Neoscopelidae (1). LITERATURE CITED Polymixioidei.-Polymixiidae (1). Batra- Paracanthopterygii.-Antennariidae (1), Aphredoderidae (1), BEGLE,D. 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The relationships of the pa- pididae (1), Bathyclupeidae (1), Caesionidae (1), Callanthiidae (1), laeoniscid a review on new Centracanthidae fishes, based specimens Carangidae (4), (1), Centrarchidae (2), Centropom- of Mimia and from the idae (2), Cepolidae (1), Cirrhitidae (1), Coryphaenidae (1), Dinoles- Moythomasia Upper Devo- tidae (1), Drepaneidae (1), Emmelichthyidae (1), Ephippididae (1), nian of Western Australia. Bull. Brit. Mus. (Nat. Epigonidae (1), Gerreidae (1), Glaucosomatidae (1), Girellidae (2), Hist.), Geol. 37:173-428. Haemulidae Howellidae Grammatidae (1), (1), Hapalogenysidae (1), GOODRICH,E. S. 1930. Studies on the structure and (1), Kuhliidae (1), Kurtidae (1), Kyphosidae (1), Inermiidae (1), Lactariidae (1), Leiognathidae (1), Lethrinidae (1), Lobotidae (1), developmentof .Dover Publ.,New York, Lutjanidae (2), Malacanthidae (1), Moronidae (2), Nemipteridae (1), New York (1958 reprint). JOHNSON-MONOPHYLY OF EUTELEOSTEAN CLADES 25

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