BULLETIN OF MARINE SCIENCE, 52(1): 554-626, 1993 PERCOMORPH PHYLOGENY: A SURVEY OF ACANTHOMORPHS AND A NEW PROPOSAL G. David Johnson and Colin Patterson ABSTRACT The interrelationships of acanthomorph fishes are reviewed. We recognize seven mono- phyletic terminal taxa among acanthomorphs: Lampridiformes, Polymixiiformes, Paracan- thopterygii, Stephanoberyciformes, Beryciformes, Zeiformes, and a new taxon named Smeg- mamorpha. The Percomorpha, as currently constituted, are polyphyletic, and the Perciformes are probably paraphyletic. The smegmamorphs comprise five subgroups: Synbranchiformes (Synbranchoidei and Mastacembeloidei), Mugilomorpha (Mugiloidei), Elassomatidae (Elas- soma), Gasterosteiformes, and Atherinomorpha. Monophyly of Lampridiformes is justified elsewhere; we have found no new characters to substantiate the monophyly of Polymixi- iformes (which is not in doubt) or Paracanthopterygii. Stephanoberyciformes uniquely share a modification of the extrascapular, and Beryciformes a modification of the anterior part of the supraorbital and infraorbital sensory canals, here named Jakubowski's organ. Our Zei- formes excludes the Caproidae, and characters are proposed to justify the monophyly of the group in that restricted sense. The Smegmamorpha are thought to be monophyletic principally because of the configuration of the first vertebra and its intermuscular bone. Within the Smegmamorpha, the Atherinomorpha and Mugilomorpha are shown to be monophyletic elsewhere. Our Gasterosteiformes includes the syngnathoids and the Pegasiformes (Pegasus) and Indostomiformes (lndostomus), two groups which are shown to be immediately related to syngnathoids by modifications of the gill filaments and their skeletal supports. Monophyly of the Gasterosteiformes in this sense is justified by several characters. We are unable to resolve the interrelationships among the five subgroups of Smegmamorpha. The remaining percomorphs are the Perciformes (including Caproidae), Scorpaeniformes, Dactylopteri- formes, Pleuronectiformes and Tetraodontiformes; we have found nothing to indicate that Percomorphain that sense are monophyletic, although our survey does not cover Tetraodonti- formes. We believe that Scorpaeniformes and Pleuronectiformes are nested within Perci- formes, but again have found nothing to indicate that Perciformes in this expanded sense are monophyletic. We recommend extending the Percomorpha to include the Atherinomorpha (and other smegmamorphs), and argue that this larger group is monophyletic. A scheme of relationships of the seven groups Lampridiformes, Polymixiiformes, Paracanthopterygii, Stephanoberyciformes, Zeiformes, Beryciformes and the expanded Percomorpha is presented and supported by apomorphies. New names for higher acanthomorph taxa are proposed as follows: Euacanthomorpha (Acanthomorpha minus Lampridiformes), Holacanthopterygii (Eucanthomorpha minus Polymixiiformes), and Euacanthopterygii (Acanthopterygii minus Stephanoberyciformes). Monophyly of Beryciformes s.1. (including stephanoberyciforms) is rejected because Beryciformes s.s. share several apomorphies with the expanded Percomor- pha, all of which are absent in Stephanoberyciformes. The Zeiformes are the most problematic of the acanthomorph groups; with the characters that we have been able to assess, the zeiforms are placed most parsimoniously as the sister-group of Euacanthopterygii (i.e., between stepha- noberyciforms and beryciforms on the cladogram), but we do not propose a name for the taxon so formed. There is a disturbing incidence of homoplasy in the characters that we have investigated in acanthomorphs. Fishes, considered collectively ... offer to the philosopher an endless source of meditation and surprise. J.-A. Brillat-Savarin, "The Philosopher in the Kitchen," 1825. Thus, recent work has resolved the bush at the bottom, but the bush at the top persists. G. Nelson (1989: 328). 554 JOHNSON AND PATTERSON: PERCOMORPH PHYLOGENY 555 Our original intention, in getting together to produce a concluding paper for this symposium volume on percomorph phylogeny, was to summarize and draw together the contents of the volume. We have, in fact, produced something more pretentious or utopian. The organizer of a symposium on percomorph phylogeny might hope that the result would be a new and well-supported scheme of rela- tionships for the group, or at least for its major clades. That is not what this volume contains; the majority of the included papers deal with phylogenetic relationships within perciform clades. We do not comment on those, not because we disregard them but because they concern disparate twigs of the tree, and so make no connected story. Here we are more concerned with the main branches of the tree, percomorphs and their relatives. We decided, perhaps unwisely, to grasp the nettle, to plunge into the glycerin, and to propose a scheme of relation- ships for those groups. That was, in part, an aim of the symposium, because in the concluding general discussion the participants collaborated, with more or less enthusiasm, in drawing up such a scheme. Our own concluding cladogram agrees with that post-symposium version in having eight nodes or non-terminal com- ponents, but all eight of those components are different in the two, and only six out of a dozen terminals are identical (they are polymixiids, lampridiforms, par- acanthopterygians, gasterosteiforms, mugiloids, and atherinomorphs). There are several billion other possibilities, and in presenting ours we recognize one other point that came up in the post-symposium discussion, that any tree can be justified by special pleading, by insisting that certain characters are uniquely derived but others are more labile or plastic. Our adventure with the glycerin convinced us of one thing-very few of the characters found among percomorphs and their relatives are uniquely derived, and progress will not be made without some special pleading. Reviewing and comparing all of the contributors' manuscripts for this volume has been a stimulus to the development of our own ideas, however misguided they may be. Inevitably, those ideas contradict some of the contributors, most of whom have not had the opportunity to respond. We apologize to them here, and acknowledge the unfair advantage that we enjoyed. THE PERCOMORPH PROBLEM When Rosen (1973) named Percomorpha, it included beryciforms, perciforms, and the groups placed between and beyond those in Greenwood et al.'s (1966) classification, such as zeiforms, lampridiforms, gasterosteiforms, scorpaeniforms, pleuronectiforms and tetraodontiforms; in others words, Percomorpha = Acan- thopterygii minus Atherinomorpha. Rosen gave no characters for his Percomor- pha, and to our knowledge, no one has subsequently found any that characterize all the included taxa (e.g., Lauder and Liem, 1983). Possible counter examples to that statement may be found in Stiassny (1990), who cited medial suturing or apposition of the pelvic bones and ventral displacement of the anteromedial process of the pelvic bone, and Roberts (1993), who cites transforming ctenoid scales. But Stiassny's percomorph characters are denied by Stiassny's (1990, 1993) own argument that mugiloids, which have the characters, are related to atheri- nomorphs, and Roberts's character, strictly applied (as he employs it in this volume), necessitates exclusion from the percomorphs of percoid taxa such as Priacanthidae, Epigonidae, Bramidae, Ostracoberyx and Howella. Our current understanding of the Percomorpha as circumscribed by Rosen is that they are polyphyletic, and are therefore an unreal and uncharacterizable group. We believe that the situation can be rectified only by modifying the content ofPercomorpha, 556 BULLETIN OF MARINE SCIENCE, VOL. 52, NO. I, 1993 excluding some of Rosen's percomorphs and including some of his non-perco- morphs. Our reasons for these changes include proposals and opinions concerning (I) the lampridiforms, (2) the paracanthopterygians, (3) the beryciforms, (4) the atherinomorphs, (5) the perciforms, and (6) the zeiforms. In the following sections we summarize information on those six groups, discussing characters (given bold numbers) of which some are described in detail only in the succeeding character list. Nevertheless, there is unavoidable repetition between the accounts of indi- vidual groups and the concluding description of characters. Our conclusions on those six groups lead us to propose names for several new higher taxa within acanthomorphs, a procedure that may seem premature. But our goal is to focus in on the Percomorpha, to characterize the group and to specify what it does and does not contain; we give new names for acanthomorph taxa that we believe to be either more or less inclusive than Percomorpha to achieve that goal and to place Percomorpha in the hierarchy. Rosen (1964: 220) wrote "In any study that involves taxonomic rearrangements, inevitably there arises the question of what to call various groups during the presentation of new evidence, especially when new group names are proposed and groups of long standing are dismembered and the components are redistrib- uted." We faced the same problem here. In the following we use the name "lam- pridiforms" in the sense of Olney et al. (1993; i.e., excluding ateleopodids); "par- acanthopterygians" and "atherinomorphs" are used in the conventional sense (as circumscribed, for example, respectively by Patterson and Rosen, 1989, and Pa- renti, 1993); "perciforms" means Perciformes in the conventional sense (Nelson, 1984),