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The Subocular Shelf of '

C. LAVETT SMITH AND REEVE M. BAILEY Museum of Zoology, University of Michigan, Ann Arbor, Michigan

The subocular shelf is a bony lamina cumorbital series. A further distinction is that extends inward from the suborbital necessary, however, since the circumor- bones of certain fishes and forms part of bitals are readily divisible into (1) a supra- the wall of the orbit. Its presence or ab- orbital series consisting of bones that lie sence has long been used as a taxonomic dorsal to the orbit and have no associated character, particularly at the family level. sensory canal and, (2) a suborbital series Boulenger (1895) was apparently the first of bones that completes the circumorbital to introduce the character, and later ('04) ring and is penetrated or traversed by the he recorded its occurrence in the families infraorbital branch of the sensory-canal of perciform fishes admitted by him. Smith system. The supraorbitals and suborbitals ('41) used the subocular shelf to separate have very different evolutionary destinies. some pentapodid and related fishes. Re- There has been some variation in the cently Akazaki ('58) has described varia- method of counting the bones of the sub- tions in the shelf among genera of sparoid orbital series. Most authors have included fishes of Japan, and Katayama ('59, '60) the first (anterior) bone, the lachrymal has employed the configuration of the shelf (preorbital), in the count, but some have to distinguish infrafamily groups of the excluded it and others have begun the . It is apparent, however, that count from the posterior side of the orbit. few authors have properly appreciated the In the following discussion and descrip- utility of this character and it is cominonly tions the lachrymal bone, which in ignored. bears the anterior terminus of the infra- The function of the shelf seems to have orbital canal, is counted as the first mem- received little attention. Some authors dis- ber of the series. The count continues miss it with the statement that it supports backward to include the dermosphenotic. the eye, but the optical effectiveness of re- At least among teleosts the number of lated fishes that lack the shelf invites re- bones in the suborbital series is remark- consideration of this patent explanation. ably constant: usually there are 6, al- In an attempt to evaluate the taxonomic though in some fishes the bones have un- utility of the subocular shelf we have dergone reduction and in a few one or examined representatives of most of the more of them have divided, thus increasing currently recognized orders of fishes and the total number of elements. have given considerable attention to the distribution of the shelf within the Perci- Primitive fishes formes and, particularly, among the fam- ilies of the superfamily . In this In such primitive groups as the study it has been necessary to consider paleoniscids, semionotids, and lepisosteids, all bones of the circumorbital ring and in the circumorbitals are connected to the sur- so doing we have developed what appears rounding dermal bones. The supraorbitals to be a satisfactory working hypothesis of are rigidly attached to the cranium, and the functional and phylogenetic signifi- the suborbitals may either be in contact cance of the subocular shelf. with the preopercle or separated from it by a series of postorbital bones. This Nomenclature closed bony sheathing of the circumorbital In primitive fishes the eye is completely area is relatively inflexible. In the surrounded by a series of small bones that 1This study has been made possible by a research may conveniently be referred to as the cir- grant from the National Science Foundation (6-6368). 1 2 C. LAVETT SMITH AND REEVE M. BAILEY semionotid Dapedium the circumorbitals Lower teleosts approach uniformity in size and shape The primitive clupeifom Osteoglossum (fig. 1A). In Lepisosteus the anterior bones bicirrhosum (fig. 1C) has a suborbital se- are modified in conjunction with the elon- ries much like that of Amia, with the fourth gate snout (Gregory, ’33: 128-129) and and fifth bones greatly expanded to fill the several bones correspond to the single entire region between the orbit and the lachrymal of teleosts. The infraorbital preopercle and between the maxilla and canal extends forward through them and the pterotic. Here also the supraorbitals the series of fixed maxillary bones to join are wanting and the frontal and dermo- its fellow from the opposite side in a supra- sphenotic form the dorsal sector of the ethmoid (rostral) commissure, and to orbital rim. Gregory (’33: 163) identified unite with the supraorbital canal postero- the enlarged bone at the front of the orbit mediad of the posterior nostril. In Polyp- as a prefrontal. Since it is perforated by terus the solidification of the suborbitals the infraorbital canal, however, we think that it is at least in part the lachrymal and is extreme; the ventral elements behind that the suborbitals on Gregory’s figure the lachrymal are fused with the maxilla, should be renumbered. The prefrontal in and an anterior platelike extension of the Osteoglossum is unossified or is coos&ed preopercle covers the upper cheek and with the lachrymal. In the articulates with the dermosphenotic. the skull is more mobile and there are two In the course of fish evolution there supraorbital bones; the lachrymal is at- have been two prominent trends in the tached to the anterior of these rather than skull bones. The dermal bones have mi- to the prefrontal. All of the suborbitals grated inward so that they no longer pre- are thin and delicate, and the only contact sent sculptured external surfaces and there with the neurocranium is between the has been reduction in size and increased dermosphenotic and the sphenotic. In the mobility of the skull bones. The circum- Salmoninae the dermosphenotic is unossi- orbital bones have in general conformed to fied. The posterior suborbitals may be in these trends except where environmental contact with or remote from the pre- stresses have imposed additional demands opercle. that have been met by stiffening of the Some characids have a large supra- circumorbital ring. orbital that meets the dermosphenotic to In Amia calva (fig. 1B) the maxilla is exclude the frontal from the orbital rim, as in Hydrocyon and Brycon (Gregory, ‘33 : freely movable and bears no canal. Per- haps partly in response to the loss of sup- 184-185), or the supraorbital may be ab- sent, as in Erythrinus (Gregory, 182) port from the maxilla and partly as protec- ‘33: and Carnegiella (Weitzman, ’54: 249). In tion for the critical joints at the proximal the three genera first named the suborbitals end of that bone, the anteriormost suborbi- are large plating bones that fully sheath tal has become enlarged and modified as the cheek; in CarnegieZEa they are much the lachrymal. The infraorbital canal ex- reduced. The bone termed adnasal by tends forward from the lachrymal into the Weitzman seems to be the lachrymal; al- adnasal. The second and third suborbitals though not shown in his figure, it bears a are small and slender but the fourth and tube of the infraorbital canal. fifth are much enlarged and extend back- In most cyprinids (fig. 1D) and in the ward nearly to the preopercle; the upper more generalized genera of the Catos- edge of suborbital 5 contacts the pterotic as tomidae, the prefrontal provides the sole well as the dermosphenotic. Amia lacks osseus support of the anterior suborbitals, the supraorbital bones but this is probably and posteriorly only the dermosphenotic a specialization since some fishes higher in is in contact with the skull. There is a the evolutionary series retain them. Oc- single large supraorbital bone. In the casionally there are a few bony nodules, more advanced catostomids (Catostominae) “supplementary dermal bones,” that ap- the supraorbital is lacking, being fully pear to be vestigial postorbitals (Wood- coossified with the frontal (Weisel, ’60: ward, 1895: 369). 110). In the ictalurid the lachry- THE SUBOCULAR SHELF OF FISHES 3 mal is a small, Y-shaped bone and the re- suborbital series. This seems to be the maining 5 or 6 suborbitals are reduced to primitive condition but through selective slender tubular ossifications around the loss and retention of elements the shelf infraorbital canal. In the Ictaluridae there has assumed modified forms in various is no supraorbital. fish groups. In the beryciform Mono- Throughout the and the centris japonicus (Starks, '04: 618), as in modifications serve to most members of the perciform super- make the suborbital series more flexible. family Percoidea, the third bone alone con- The bones are reduced in size, the connec- tributes to the shelf. The third suborbital tions between them are ligamentous, and is nearly always involved and this is per- the diarthrosis between the lachrymal and haps presaged in Myripristis where the the prefrontal is developed to allow move- segment of the shelf derived from the third ment in any plane. The lachrymal has bone is the widest. In Channa lucius the been specialized to protect the anterior end third suborbital enters the shelf but the of the maxilla. At the same time the trend in the supraorbitals is toward reduction, fourth and fifth, which contribute equally, loss, or fusion so that the dorsal rim of the form most of the shelf, which consequently orbit is rigid. No malacopterygian is forms the posterior wall of the orbit. In known to have a subocular shelf. Channa striata only the fourth and fifth suborbitals participate in the shelf, but Development of the shelf the fifth is much the larger (fig. 3R). In In the there is a temporary and Mullidae the second and reversal of the trend toward increasing third bones contribute the shelf. These flexibility of the circumorbital ring. Part variations seem readily derivable from the of the resultant stiffening is achieved unmodified shelf in Myripristis, a finding through the development of sutures be- that is consistent with the hypothesis that tween the individual suborbital bones. A the beryciform fishes are on or near the more important bracing device is evolved stem line leading to the and through the expansion of some of the sub- their derivatives. orbital bones to provide structural strength- In the climbing , Anabas testu- ening and additional area for the attach- dineus, of the order Perciformes, sub- ment of connective tissues. This expansion orbitals two through five contribute to a of the bones has taken place in the only shelf that lines both the inferior and poste- direction possible - inward. In the proc- rior walls of the orbit. Suborbitals three ess the suborbital ring has been converted to five form a wide, stiff plating over the from a flat chain to a series of inflexible cheek and buttress the preopercle. The bones that are L-shaped in cross section. well-developed shelf, which is perhaps in This interpretation explains the presence part a secondary elaboration, seems here of the subocular shelf as a response to the to provide effective strengthening for the need for mechanical strengthening of the expanded suborbitals. These in turn con- entire complex of structures in the sub- tribute bracing for the opercular bones ocular area rather than for simple support that are modified to assist in terrestrial of the eyeball. Further evidence to dis- locomotion (Norman, '31: 46). credit the latter hypothesis is provided by Variations and modifications in the the snakehead, Channa (commonly known subocular shelf as Ophicephalus). In this the well- developed shelf lies on the posterior face Although systematists have largely con- rather than the floor of the orbit (Day, fined their utilization of the subocular '14: 26). shelf to statements as to its presence or The subocular shelf first appears in the absence in particular families, study of its beryciform fishes and seems to be con- structural variations (1) demonstrates fined to the orders Beryciformes and Perci- that much greater use can be made of the formes. In Myripristis microphthalmus shelf as a taxonomic character, and (2) (fig, 1E) the shelf is made up of segments adds confirmation to the hypothesis that derived from bones two through five of the the shelf is a stiffening brace. 4 C. LAVETT SMITH AND REEVE M. BAILEY

In its most common form the shelf is and allow little movement of the entire derived from the third suborbital only, is suborbital series. roughly semicircular in outline, and is In the snook, undecimaZis slightly concave to conform to the contour (fig. 2J), the shelf gives rise to a posterior of the orbit. The shelf is commonly longer bony process that connects by ligament to than the exposed part of the bone so that the anterior edges of the hyomandibular it overlaps the second and fourth sub- and the metapterygoid. The process and orbitals. The red hind, Epinephelus gut- its ligament thus serve as a guy to steady tatus (fig. lF), and the bigeye, Priucunthus the suborbital ring. A similar but shorter arenatus (fig. 2G),illustrate this condition process is found in Roccus chrysops. in with broad and narrow preor- In the sparid Calamus calamus (fig. bital regions, respectively. In the fresh- 2K) the shelf has an anterior process that water drum, Aplodinotus grunniens (fig. joins the prefrontal. Here also the articu- 2H), the shelf is reduced to a narrow, lation between lachrymal and prefrontal fingerlike process and the lateral faces of is modified to limit motion to a hinge line. the suborbitals are broad, thin plates, Calamus is a deep-headed form and the thickened along the orbital margin and lachrymal is much enlarged to cover the strengthened by a radial series of narrow preorbital region. bridges to provide protection for the in- A similar arrangement is found in the fraorbital canal. pomacentrid Hypsypops rubicundus (fig. Three major trends in the structure of 2L). Suborbitals two through five con- the shelf and the supporting bones have tribute to the shelf but the segment de- been discerned in this survey. These are: rived from the third bone is the largest (1) increased bracing of the suborbital and is provided with a knob that extends ring leading to secondary contact between inward to articulate with a complex proc- the suborbitals and the neurocranium or ess of the palatoquadrate mechanism. the palato-quadrate arch, (2) complete This process is formed by the palatine, (secondary) loss of the shelf, and (3) ectopterygoid, and mesopterygoid, but the utilization of the shelf for muscle attach- only contact is with the mesopterygoid. ment. These are considered with selected Again the lachrymal-prefrontal joint is a examples below, Additional trends will hinge that allows little movement. doubtless be found when other specialized Secondary loss of the subocular shelf. groups of fishes are studied carefully. Within the superfamily Percoidea a few Increased bracing of the suborbital se- families have no trace of the subocular ries. Additional stiffening of the subor- shelf. Because there is an apparent cor- bitals may be achieved through modifica- relation between the absence of the shelf tion of the articulation between the and the habitat occupied by most members lachrymal and the prefrontal, as seen in of the family we believe that loss of the Scatophagus argus (fig. 21). In this spe- shelf is a specialization. The families that cies a stout peg of bone that extends in- lack the shelf are not particularly closely ward articulates firmly along its entire related and do not form a single phyletic dorsal face with the ventral surface of the line, so it is evident that this specializa- prefrontal. Anteriorly the lachrymal artic- tion must have been derived independ- ulates with the palatine and posteriorly it ently several, perhaps many, times. is completely fused with the second sub- Certain Iong-established families of orbital, which in turn is rigidly sutured freshwater fishes have lost the shelf: the to the third suborbital. In the wolf-, , , Cichlidae, and Anarrhichthys ocellatus, the suborbital Toxotidae are examples. In the large- bones are massive, and a mesial shelflike mouth , Micropterus salmoides (fig. projection derived from the first two bones 3M), the loss of the shelf is not the only articulates firmly with the prefrontal. It modification leading to mobility of the is not certain that this structure is homol- suborbital ring since the second and third ogous with the usual perciform shelf. suborbitals are subdivided and the connec- These adaptations effectively limit motion tions between the bones are diarthroses, between the lachrymal and the prefrontal, affording maximum flexibility. Even more THE SUBOCULAR SHELF OF FISHES 5 extreme is the situation in the white crap- the subocular shelf. In order to compen- pie, Pomoxis annularis (fig. 3N), in which sate for the muscle pull there is a ligament the second bone has been lost, leaving an connecting the fourth and fifth bones with interrupted infraorbital canal and an in- the hyomandibular. Thus, there is a direct complete suborbital ring. Possibly the line of stress from the hyomandibular, shelf has been lost in freshwater fishes in through the ligament, the fifth suborbital, response to the need for an efficient gill the fourth suborbital, the shelf, and the pump in an environment subject to oc- muscle from its origin to its insertion on casional periods of oxygen deficit. The the inner face of the proximal end of the Nandidae, Channidae, and Anabantidae maxilla. constitute exceptions in that they are In the black jack, Carunx Zugubris (fig. freshwater groups that retain the shelf. 3Q), there is an apparent independent de- A second group of families that lack the velopment of the shelf as an origin for the shelf contains fishes adapted for a mid- adductor mandibulae muscle. In a sense, water or pelagic existence: the Rachycen- this species appears to be subjected to con- tridae, Coryphaenidae, Bramidae, and Ky- flicting demands. It retains the shelf of its phosidae are examples. In suborders of the more sedentary ancestors and needs a Perciformes other than the , the brace for the shelf to counteract the pull Scombridae, Stromateidae and Mugilidae of the muscle. At the same time the jack also fall into this category. Perhaps the is adapted for a midwater existence that demands of respiration or of predaceous requires a flexible suborbital ring. It has or piscivorous habits necessitate a flexible been successful in meeting both condi- suborbital ring. tions: the brace is a splint of bone from The third group in which there is no the shelf that articulates with the hyo- subocular shelf includes those families mandibular; the flexibility is achieved by which have specializations of the mouth- the development of diarthroses between parts that require exceptional mobility. the individual bones of the suborbital se- The and the Gerridae have ries. extremely protrusible mouths. Except in There is a more notable specialization the gerrid genus Diapterus the shelf is in the spotted , Pseudupeneus lacking. In at least some species of Poma- maculatus, in which the anteroventral dasyidae (e.g., Haemulon sciurus, fig. 30), shelf is derived from the second and third the mouth is modified so that it can be suborbitals. The long narrow lachrymal, opened widely to display its red lining. which bears numerous branches of the in- Apparently correlated modifications in- fraorbital canal, is excluded from the or- clude the loss of the subocular shelf and bital margin. Two dorsal bundles of the the presence of a true diarthrosis between adductor mandibulae insert together on the palatine and pterygoid bones. The the maxilla; the dorsal one originates on labrids and scarids, with protrusible the shelf of the enlarged second suborbital, mouths or parrotlike beaks, also lack the the one below passes directly beneath the shelf. third suborbital to its tendonous origin on Utilization of the shelf for muscle at- the hyomandibular. This tendon is at- tachment. In most species with a sub- tached by many small muscle fibers to the ocular shelf no major muscles are attached shelf of the third suborbital. Here, the to it, but in a few forms the shelf has sec- strain produced by the contraction of the ondarily been taken over for the origin of a upper segment is counteracted by the ten- muscle. In the snapper Lutjanus black- don of the lower. for& (fig. 3P) the lachrymal is wide and In Channa it is the levator arcus palatini covers the shaft of the maxilla; the shelf muscle that is attached to the subocular is roughly quadrangular and overlaps the shelf, morphologically a postocular shelf fourth suborbital but not the second. (fig. 3R; see p. 3). In this genus the There is a flexible ligamentous connection postorbital part of the head is excessively between the second and third suborbitals. elongate to accommodate a suprabranchial The dorsal portion of the adductor mandi- respiratory chamber. In conjunction with bulae originates on the ventral surface of this modification the head of the hyoman- 6 C. LAVETT SMITH AND REEVE M. BAILEY dibular is greatly lengthened and an exten- marked utility in classification and in re- sion of the anterior portion of the levator vealing phyletic trends. The number of arcus palatini originates on that segment kinds examined is not exhaustive so a of the shelf derived from the fifth subor- shelf may have been overlooked in certain bital. The muscle inserts on the metaptery- groups in which it is present in some goid. In Channa the suborbitals are unus- forms. Nevertheless, the distribution is ually deep and thick and are broadly probably rather well indicated. Among laminated to produce a shield that is rigid the groups commonly classified as sub- in the sagittal axis but semiflexible in a orders of the Perciformes we have failed horizontal plane. In the distantly related to find a shelf in any of the following: anabantid Anabas testudineus (see p. 3) Siganoidei, Kurtoidei (Boulenger, ’04 : 688), the suprabranchial chamber is provided Trichiuroidei, Scombroidei, Gobioidei, Cal- with an elaborate labyrinthine apparatus lionymoidei, Ophidioidei, Stromateoidei, for aerial respiration. In this form, how- and Mugdoidei. As indicated above (p. ever, the head is not notably elongate, and 3) a well-defined shelf is present in the levator arcus palatini does not attach Chunna and in Anabas (Anabantoidei). to the shelf. We have examined only two genera among the Blennioidei. In Labrisomus the Occurrence of the subocular shelf shelf, if present, is narrow; that in Anar- As indicated above, we have not found rhichthys has been discussed (p. 4). In a subocular shelf in any primitive fish or the Acanthuroidei, sometimes placed in in any lower . Nor have we dis- the Percoidei, we find a shelf in Zanclus covered a shelf in representatives exam- (Zanclidae) but nqi in Acanthurus, Cteno- ined from such “intermediate” orders as chaetus, or Zebrasoma (Acanthuridae). the (Belonidae, Exocoetidae), Among representatives of the Cottoidei ex- Notacanthiformes (, Boul- amined, the shelf is present (Sebastes) or enger, ’04: 624), (Cy- absent (Scorpaena) in the Scorpaenidae, prinodontidae, Poeciliidae), Gadifonnes and absent in the Cottidae, Anoplopomati- (Gadidae), (Gasteros- dae, and Hexagrammidae. The majority teidae), Pegasiformes (Pegasidae), Lam- of the percoid fishes are in the suborder pridiformes (Lampridae), (Zei- Percoidei, a group in which the shelf is dae), and (Percopsidae, commonly present but has presumably Aphredoderidae). been lost repeatedly in separate phyletic In the Beryciformes a subocular shelf is lines. In the , Emmelichthyi- present in the three species of the suborder dae, Ephippidae, Gerridae, Pempheridae Berycoidei that were examined : and some genera have the shelf japonica Gunther [Polymixiidae], Holo- and others lack it. More commonly, how- centrus rufus (Walbaum) and Myripristis ever, all forms in a single family agree. microphthaZmus Bleeker []. The species of the order Perciformes that Hoplostethus japonicus Hilgendorf [Tra- have been examined for presence or ab- chichthyidae] and Monocentris japonicus sence of a subocular shelf are listed, by (Houttuyn) [Monocentridae] are also re- family, in table 1. ported to have a shelf (Starks, ’04: 606, Among the orders derived from the 618). There is no shelf, however, in the Perciformes, none is known to have a sub- bathypelagic species Melamphaes bispi- ocular shelf. For several of these the spe- nosus Gilbert [Melamphaeidae]of the sub- cies studied lack suborbital bones altogether order Anoplogasteroidei. In this species or retain only a reduced lachrymal: Pleuro- the thin, delicate suborbitals are much nectiformes, Bothus Zunatus (Linnaeus), modified and are expanded laterally as a Parophrys vetulus Girard; Tetraodonti- partial protective support for the infraor- formes, Rhineacanthus aculeatus (Lin- bital canal. naeus), Balistes sp.; Gobiesociformes, It is in the order Perciformes that the Gobiesox sp. (Gregory, ’33: 372); Batra- subocular shelf reaches its best develop- choidiformes, Opsanus tau (Linnaeus) ; ment. Many hundreds of species have a Lophiiformes, Histrio histrio (Linnaeus) ; shelf and its presence or absence is of Mastacembeliformes, Macrognathus acu- THE SUBOCULAR SHELF OF FISHES 7

TABLE 1 The subocular shelf in fishes of the order Perciformes. To facilitate reference the sequence is alphabetical. Presence of a shelf is indicated by (+), absence by (0). Subocular Subocular Family - Species shelf Family - Species shelf Acanthuridae Chiasmodontidae Acanthurus coeruleus Bloch and Chiasmodon niger Johnson 0 Schneider 0 (Norman, '29: 532-533) A. matoides Valenciennes 0 Cichlidae A. triostegus (Linnaeus) 0 Cichlasoma cyanoguttaturn (Baird Ctenochaetus striatus (Quoy and and Girard) 0 Gaimard) 0 C. biocellatum (Regan) 0 Zebrasaa flavescens (Bennett) 0 Geophagus jurupari Heckel 0 Ammodytidae Haplochromis strigigena (Pfeffer) 0 Ammodytes hexapterus Pallas 0 Petenia splendida Gunther 0 Anabantidae Pterophyllum eimekei Ahl 0 Anabas testudineus (Bloch) + Tilapia zilli (Gervais) 0 Anarhichadidae Anarrhichthys ocellatus Ayres (see text) Cirrhitus alternatus Gill + Anoplopomatidae Paracirrhites arcatus (Cuvier) + Anoplopoma fimbria (Pallas) 0 Clinidae Apogonidae Labrisomus nuchipinnis (Quoy Apogon conklini (Silvester) + and Gaimard) 0 A. lineatus Temminck and Schlegel + Coryphaenidae A. stellatus (Cope) + hippurus Linnaeus 0 Arripidae Cottidae Ampis trutta (Forster) + Cottus cognatus Richardson 0 Banjosidae C. ricei (Nelson) 0 banjos (Richardson) + Scorpaenichthys marmoratus (Ayres) 0 Dichistiidae argentea Goode and sp. + Bean + (Norman, MS.) Bramidae Drepanidae Brama rayi (Bloch) 0 punctata (Linnaeus) 0 Branchiostegidae Eleotridae Caulolatilus princeps (Jenyns) + Eleotris pisonis (Gmelin) 0 plumieri (Bloch) + Embiotocidae Callionymidae Cymatogaster aggregata Gibbons + Callionymus richardsoni Bleeker 0 Embiotoca jacksoni Agassiz + Carangidae Hysterocarpus traski Gibbons + Caranx latus Agassiz + c. lugurnPoey + Centracanthus cirrus Rafinesque + Selene vomer (Linnaeus) 0 Dipterygonotus gruveli Chabanaud + Seriola falcata Valenciennes + Emmelichthyups atlantica Schultz 0 Centrarchidae Erythrocles schlegeli (Giinther) + 13 species in genera Acantharchus, Merolepis vulgaris (Valenciennes) + Ambloplites, Archoplites, Enoplosidae Chaenobryttus , Enoplosus amatus (White) Lepomis, Micropterus, and Ephippidae + Pomoxis 0 Chaetodipterus fuber (Broussonet) 0 Centropomidae Ephippus orbis (Bloch) + Centropomus undecimalis (Bloch) + Gerridae Cepolidae Diapterus olisthostomus (Goode and Acanthocepola krusensterni (Tem- Bean) + minck and Schlegel) + D. plumieri (Cuvier) + Cepola rubescens Linnaeus + Eucinostomus argenteus Baird and Chaetodontidae Girard 0 aya Jordan + Gerres cinereus (Walbaum) 0 C. striatus Linnaeus + Girellidae Chelmon rostratus (Linnaeus) + Girella nigricans (Ayres) + Holacanthus bermudensis (Goode) + Gobiidae Pomacanthus aureus (Bloch) + Awaous transandeanus (Gunther) 0 Channidae Hexagrammidae Channa lucius (Kuhl and van Ophiodon elongatus Girard 0 Hasselt ) + Histiopteridae C. striata (Bloch) + Quinquarius japonicus (Doderlein) + (continued) 8 C. LAVETT SMITH AND REEVE M. BAILEY

TABLE 1 (Continued)

Subocular Family Species Subocular Family - Species shelf - Shelf Kuhliidae Pempheridae Kuhlia malo (Valenciennes) 0 Pempheris oualensis Cuvier + K. marginata (Cuvier) 0 P. schomburgki Miiller and Troschel 0 K. rupestris (LacBpBde) 0 Percidae Kurtidae Etheostoma blennwides Rafinesque 0 Kurtus indicus Bloch 0 E. simoterum (Cope) 0 (Boulenger, '04: 688) Perca flauescens (Mitchill) 0 Kyphosidae Percina maculata (Girard) 0 Hermosilla azurea Jenkins and Stizostedion canadense (Smith) 0 Evermann 0 S. uitreum (Mitchill) 0 Kyphosus sectatrix (Linnaeus) 0 Plesiopidae Labracoglossidae Plesiops melas Bleeker + Labtacoglossa argentiuentris Peters + P. nigticans (Riippell) + Labridae Polynemidae Bodianus rufus (Linnaeus) 0 Polydactylus octonemus (Girard) + Coris gaimardi (Quoy and Gaimard) 0 Pomacentridae Halichoeres radiatus (Linnaeus ) 0 Chromis punctipinnis (Cooper) + Lachnolaimus maximus (Walbaum) 0 Hypsypops rubicundus (Girard) + Pimelometopon pulchrum (Ayres) 0 Pomadas yidae Lactariidae Anisotremus davidsoni (Steindachner ) 0 Lactarius Zactarius (Bloch and A. surinamensis (Bloch) 0 Schneider) 0 Conodon serrifer Jordan and Gilbert 0 Leiognathidae Haemulon plumieri (LacBpBde) 0 Gazza minuta (Bloch) 0 H. sciurus (Shaw) 0 Leiognathus nuchalis (Temmick and Orthopristis chrysopterus (Linnaeus) 0 Schlegel) 0 Plectorhinchus cinctus (Temminck L. ruconius (Hamilton-Buchanan) 0 and Schlegel) 0 Pomadasys crocro (Cuvier) Lobotidae 0 Datnioides microlepis Bleeker 0 Pomatomidae Lobotes surinamensis (Bloch) 0 Pomatomus saltatrix (Linnaeus) + Scombrops bows (Houttuyn) + Caesio chrysozona Cuvier + arenatus Cuvier + C. lunatis Cuvier + Rachycentridae Lutjanus apodus (Walbaum) + Rachycentron canadum (Linnaeus) 0 L. blackfordi Goode and Bean + Scaridae griseus (Linnaeus) L. + Scarus guucamaiu Cuvier 0 L. uiuanus (Cuvier) + ouiceps Valenciennes Ocyurus chrgsurus (Bloch) S. 0 + Sparisoma rubriptnne (Valenciennes) 0 Rhomboplites aurorubens (Cuvier) + Menidae Scatophagus argus (Linnaeus) (Bloch and + Schneider ) 0 Aplodinotus grunniens Rafinesque + nobilis (Ayres) + Monodactylus argenteus (Linnaeue) + C. parvipinnis Ayres Mugilidae Eguetus lanceolatus (Linnaeus) + Mugil curema Valenciennes 0 Menticirrhus undulatus (Girard) + Mullidae Scombridae + Mulloidichthys ma&nicus (Cuvier) + Auxis tapeinosoma Bleeker 0 Pseuduveneus maculatus (Bloch) + Sarda sardu (Bloch) 0 Nandidae- Scomber scombrus Linnaeus 0 Polycentrus schomburgki (Muller Scomberomorus regalis (Bloch) 0 and Troschel) + Scorpaenidae Pristolepis fasciutus (Bleeker) + Scorpaena guttata Girard 0 Nototheniidae Sebastes atrwtrens (Jordan and Notothenia macrocephala Gunther 0 Gilbert) + Opisthognathidae S. diploproa (Gilbert) + Opisthognathua maxQlosus Poey 0 S. entomelas (Jordan and Gilbert) + Oplegnathidae S. goodet (Eigenmann and fasciatus (Temminck Eigenmann ) + and Schlegel) I- S. paucispinis Ayres + 0.punctatus (Temminck and S. rhodmhloris (Jordan and Gilbert) + Schlegel) + S. serriceps (Jordan and Gilbert) + (continued) THE SUBOCULAR SHELF OF FISHES 9

TABLE 1 (Continued) Subocular Subocular Family - Species shelf Family - Species shelf Scorpidae L. hatak (Forskill) Rudimentary Medialuna culiforniensis (Stein- L. nebulosus (ForskAl) Rudimentary dachner ) + Nemiptems hypselognathus (Bleeker) + Microcanthus strigatus (Cuvier) + N. uirwtus (Houttuyn) + Serranidae Pentapodus caninus-(&vier) + 24 species in the genera Acropoma, tumifrons (Temminck Alphestes, Cephalopholis, Doder- and Schlegel) + leinia, Epinephelus, Hapalo- Scolopsis Mlineata Kner + genys, Malakichthys, Myctero- Stenotomus chrysops (Linneaus) + perca, Paralabrax, Paranthias, Sphyraenidae Percichthys, Petrometopon, Prio- Sphytaena argentea Girard 0 nodes, Roccus, and Rypticus + Stromateidae Siganidae Peprilus paru (Linnaeus) 0 Lo uulpinus (Schlegel and Muller) 0 Theraponidae Siganus sp. 0 Therapon jarbua (Forskill) + T.oxyrhynchus Temminck and japonica Temminck and Schlegel + Schlegel + T.theraps Cuvier + S. sihama (Forskill) + Toxotidae Sparidae' Toxotes faculator (Pallas) 0 Archosatgus rhomboidulis (Linnaeus) + Trichiuridae Calamus calamus (Valenciennes) + Trichiutus lepturus Linnaeus 0 Diplodus atgenteus (Valenciennes) + Trichodontidae Gymnocrunius griseus (Scblegel) + Trichodon trichodon (Tilesius) 0 Lethtinus haematoptetus Zanclidae Schlegel Rudimentary Zanclus cornutus (Linnaeus) -I-

1The genera here assigned to the S aridae together with certain related groups, have an unsettled family history. many having been juggled geely thong the Denticidae, , Lutjanidae, Nemipteridae. Pentapodidae, Pomadasyidae, and Scolopsidae. On the basis of work still incomplete these genera seem best associated in a single family. In view-of the vagaries and inconsistencies of prior classifications, adoption of this provisional.arrangement is deemed preferable to acceptance of any of the older schemes, all of which are demonstrably imperfect. leatus (Bloch) ; Synbranchifonnes, Fluta (e.g., Cynoscion nobilis, Menticirrhus un- alba (Zuieuw). In remora (Lin- dulatus). Most sciaenids, however, in- naeus), of the order Echeneiformes, the habit estuaries or other euryhaline waters. suborbital series is of a generalized per- A truly marine species, Equetus lanceo- coid , with 6 bones; there is no sub- latus, has a slightly larger shelf but it still ocular shelf. is not as well developed as in groups hav- ing a long oceanic history. It is inviting to DISCUSSION speculate, then, that Equetus has in- If it is correct that the suborbitals are habited the sea longer than Aplodinotus modiiled as an indirect response to the has lived in fresh water. In the light of environment, it appears that selection for this reasoning one may suspect that and against the presence of the shelf is ex- nandids are recent invaders of fresh water, tremely slow. This suggests that the sur- for in Pristolepis fasciata the shelf is well vival value of the shelf, though slight, is developed. still present. Then it follows that the shelf The posterior shelf of Channa is appar- is indicative of the phyletic history of the ently related to the development of the group. For example, strictly freshwater suprabranchial chamber. Thus, its pres- serranids still retain the large shelf of ence facilitates aerial respiration. their marine ancestors, as does the only re sidu a1 freshwater embiotocid, Hystero- SUMMARY carps traslzi. The subocular shelf is interpreted as a The freshwater sciaenid Aplodinotus mechanism for stiffening the suborbital grunniens has a slender shelf and one ring. It apparently developed first in the might suspect that it is being lost. But Beryciformes with bones two through five other sciaenids also have a slender shelf of the suborbital series contributing to the 10 C. LAVETT SMITH AND REEVE M. BAILEY

shelf. Through selective modification and ume first. British Mus. (Nat. Hist.), London, loss of elements the shelf has assumed pp. i-xix, 1-391. - 1904 Fishes. Systematic account of diverse form in various groups of perci- Teleostei. In: The Cambridge Natural History. form fishes. Structural change of the shelf Macmillan and Company, Ltd., London, pp. and associated parts has proceeded in 539-760. several directions - additional bracing Day, A. L. 1914 The osseus system of Ophio- through contact with the skull or the cephalus striatus Bloch. Philippine Jour. Sci., palatoquadrate arch, reduction or com- 9: 19-56. Gregory, W. K. 1933 Fish skulls: A study of plete loss, and utilization as a muscle the evolution of natural mechanisms. Trans. origin. Complete loss of the shelf has oc- Amer. Philo. SOC., N. S., 23: part 2: i-vii, 75- curred in several freshwater families, in 481. midwater and pelagic fishes, and in fishes Katayama, M. 1959 Studies on the serranid with specialized mouthparts for which ad- fishes of Japan (1). Bull. Fac. Educ., Yama- ditional flexibility is required. Loss of the guchi Univ., 8: 103-180. 1960 Fauna Japonica. Serranidae suborbitals or failure of ossification is a (Pisces). Tokyo News Service, Ltd., Tokyo, frequent specialization in perciforms and pp. i-vii, 1-189. their derivatives. Norman, J. R. 1929 The teleostean fishes of The subocular shelf is usually a con- the family Chiasmodontidae. Ann. Mag. Nat. Hist., 111: 529-544. sistent taxonomic character at the family - 1931 A history of fishes. Frederick A. level, but in a few families some forms Stokes, New York. have and others lack the shelf. Those Smith, J. L. B. 1941 The genus Gymnocsanius known to us are the Carangidae, Em- Klunzinger, with notes on certain rare fishes from Portuguese East Africa, Trans. Royal SOC. melichthyidae, Ephippidae, Gerridae, Pem- So. Africa, 28: part 2: 441-452. pheridae, Scorpaenidae, and Sparidae. Starks, E. C. 1904 The osteology of some Modifications in the shape or structural berycoid fishes. Proc. U. S. Nat. Mus., 27: composition of the shelf may prove useful 601-619. Weisel, G. F. 1960 The osteocranium of the either at infrafamily or suprafamily levels. catostomid fish, Catostomus macrochellus. A There is indication that changes in the study in adaptation and natural relationship. form of the shelf take place slowly and J. Movh., 106: 109-129. that the shelf may serve as an indicator of Weitzman, S. H. 1954 The osteology and the phyletic history. relationships of the South American characid fishes of the subfamily Gasteropelecinae. Stan- ford Ichth. Bull., 4: 213-263. LITERATURE CITED Woodward, A. S. 1895 Catalogue of the fossil Akazaki, M. 1958 Studies on the orbital bones fishes in the British Museum (Natural History). of sparoid fishes. 2001. Mag. (Dobutsugaku Part 3, containing the actinopterygian Teleo- Zasshi), 67: 32S325 (in Japanese, with stomi of the orders (concluded), English rtsumb). Protospondyli, Aetheospondyli, and Isopondyli Boulenger, G. A. 1895 Catalogue of the fishes (in part). British Mus. (Nat. Hist.), London in the British Museum. Second edition. Vol- pp. i-xlii, 1-544. PLATES PLATE 1 EXPLANATION OF FIGURES

1 Representative Circumorbital Bones of Fishes. A to D in left lateral aspect. E and F in left lateral and dorsal aspects. (W. L. Brudon, del.) A. Dapedium politum Leach (redrawn from Woodward, 1895). B. Amia calva Linnaeus. UMMZ 175897-S. C. Osteoglossum bicinhosum Vandelli. UMMZ 177342-S. D. Cyprinus carpi0 Linnaeus. UMMZ 171795-S. E. Myripristis (? ) microphthulmus Bleeker. UMMZ 177346-5. F. Epinephelus guttatus (Linnaeus). UMMZ 1725434.

12 THE SUBOCULAR SHELF OF FISHES PLATE 1 C. Lavett Smith and Reeve M. Bailey

13 PLATE 2 EXPLANATION OF FIGURES

2 Suborbital Bones of Fishes. All shown in left lateral and dorsal aspects. (W. L. Brudon, del.)

G. Priacanthus arenatus Cuvier. UMMZ 173988-S. H. Aplodinotus grunniens Rafinesque. UMMZ 1471994. I. Scatophagus argus (Bloch). UMMZ 1773474. J. Centropomus undecimalis (Bloch). UMMZ M59-31. K. Calamus calamus (Valenciennes). UMMZ 142475. L. Hypsypops rubicundus (Girard). UMMZ 176284-S.

14 THE SUBOCULAR SHELF OF FISHES PLATE 2 C. Lavett Smith apd Reeve M. Bailey

15 PLATE 3

EXPLANATION OF FIGURES

3 Suborbital Bones of Fishes. M to Q in left lateral and dorsal aspects. R in left lateral and anterodorsal views. (W. L. Brudon, del.)

M. Micropterus salmoides (LacCpBde). UMMZ 171793-5. N. Pomoxis annularis Rafinesque. UMMZ 1734693. 0. Haemulon sciurus (Shaw). UMMZ 173411-S. P. Lutjanus blachfordi Goode and Bean. UMMZ 1 741 374. Q. Caranx Zugubris Poey. UMMZ 177361-S. R. Channu striata (Bloch). UMMZ 171840.

16 3 THE SUBOCULAR SHELF OF FISHES PLATE C. Lavett Smith and Reeve M. Bailey

17