i he Ba Aa te i A i AR I Ba he) ieee SRG ee ie eae ere a $5 ng a a (OL 630 A/B6/5 BIOLOGIA CENTRALI-AMERICANA. PISCES. BY C. TATE REGAN, M.A. 1906-1908. CONTENTS. INTRODUCTION «2. 6 ee ee ee v Maps sHow1nGc THE GEoGRAPHICAL Disrripution oF FREsH-waTER FisHes 1n MExIco AND CrentTRAL AMERICA. List or Phares . . eee ee ee ee ee) XXXL TELEOSTOMI. TELEOSTEL. ACANTHOPTERYGIE 2... ek ee ee 1 LopHOBRANCHIT . . . ee ee ee ee ee CO PERCESOCES . . . 0. eee ee ee ee ee ee eee «BG HAPLOMI . . . wee ee ee eee TH APODES. . 2... ee ee ee ee ee ee ee «109 SYMBRANCHIT. - . 0] ee eee ee ee ee ee 110 OsraRIOPHYSI . . 1.) ee ee ee ee ee eee 6«dDO MALACOPTERYGII. . 2. ee ee ee ee ee ee ee «1B GINGLYMODI . 2... ew ee ee ee ee ee «180 SELACHI. KusEvacuil. PLEUROTREMATA. . . . 0. ee we ee ee ee ew we) «182 HYPOTREMATA . 1. wee we ek wk ee ee ee ee ee) «188 CYCLOSTOMATA. HyrEROARTIL . 2. wee ee ee ee ee ee ee eee CT SuPPLEMENT . 00. ee ee ee ek ee ee eee ee ee «185 INDEX . oo. 00 ee ee ee ee ee ee ee ee ew ww «198 PLATES. a2 INTRODUCTION. THERE is a considerable literature dealing with the fresh-water fishes of Mexico and Central America, but our knowledge of them must still be regarded as very incomplete. The fact that not a single fresh-water fish has yet been described from the Republic of Honduras, or from Nicaragua north and east of the Great Lakes, may be instanced in support of this. The following account is based on the material in the British. Museum; the diagnoses of the sub-orders and families in the systematic part are intended only to apply to their Mexican and Central-American representatives; in all cases synopses of the genera and species are presented in the form of keys, and sufficient references are given for the verification of determinations thus effected. Detailed descriptions and full synonymies are given only in the case of groups which appear to need revision and which are well represented in the British Museum. | True fresh-water fishes and also marine fishes which are known to ascend rivers beyond the influence of the tides are included: thus, in addition to the problems of the distribution of nearctic and neotropical types in this area, that of the differentiation of the marine faunas of the Atlantic and Pacific coasts is dealt with to a certain extent. The introductory remarks are arranged under the following headings :— 1. Principal Faunal Works on the Fresh-water Fishes of Mexico and Central America. 2. Principal Collections described in this Work. 3. Classification. 4, Geographical Distribution. 5. The Shore-Fishes of the Atlantic and Pacific Coasts of Mexico and Central America. vi INTRODUCTION. 1. Principan FAUNAL WoRKS ON THE FRESH-WATER FISHES OF MEXICO AND CENTRAL AMERICA. The fresh-water fishes of Mexico and Central America are included in Jordan and Evermann’s great work on the fishes of North and Middle America (Bull. U.S. Nat. Mus. xlvii. 1896-1900), which is, however, so far as the Central-American fresh-water fish-fauna is concerned, rather a compilation than a critical revision ; and necessarily so, seeing that the majority of the types are preserved in the British Museum and a large proportion of the remainder at Vienna. Dr. S. E. Meek has recently made extensive collections in Mexico, and has published an account of the fresh-water fishes of Mexico north of the Isthmus of Tehuantepec (Publ. Columbian Mus., Zool. v. 1904) based on his own material. Of other works dealing with Mexican fresh-water fishes we may mention Girard’s valuable report on the fishes collected during the United States and Mexico boundary survey, published in 1859, Steindachner’s report on a collection from the Lerma Basin and the Valley of Mexico (Denkschr. Ak. Wien, Ixii. 1895), and a paper by Jordan and Snyder dealing with fishes from the same region (Bull. | US. Fish. Comm. xix. 1900). Dr. Ginther’s memoir on the Fishes of Central America (Trans. Zool. Soc. Lond. vi. 1868) is still the best account of the fresh-water fishes of this region, and it is remarkable how little our knowledge of them has been increased since its publication. It was preceded by Kner and Steindachner’s account of a collection from Panama (Abhandl. Bayer. Ak. x. 1864), and the only important contributions since are by Gill and Bransford on the fishes of Lake Nicaragua (Proc. Ac. Philad. 1877), Steindachner on those of the Rio Mamoni, Panama (Denkschr. Ak, Wien, xli. 1879), and two recent papers by Meek, one on the fishes of Lakes Managua and Nicaragua, the other describing collections from Guatemala and Costa Rica (Publ. Columbian Mus., Zool. vii. 1907). 2. PRINCIPAL COLLECTIONS DESCRIBED IN THIS WoRK. The present account is based on the specimens preserved in the British Museum, including the actual types of a large proportion of the species and co-types or authenticated examples of many others. First in importance are the large collections made in Central America by Messrs. F. D, Godman and O. Salvin and Capt. J. M. Dow during the years 1859-1865, which formed the basis of Dr. Giinther’s report. Next to these must be placed a fine series of Mexican fishes received from the Field Museum of Natural History, Chicago, in 1905, including examples of many of the species recently described by Dr. Meek. INTRODUCTION. vil The remaining collections may be considered in chronological order; they include :— (1) Fishes from Mexico and Central America collected by A. Sallé in 1850 and following years. (2) Co-types of some of the species described by Baird and Girard, received from the Smithsonian Institution in 1861. (3) A collection from Southern Mexico, purchased of A. Boucard in 1868. (4) A small series from Guatemala, collected by Mr. F. C. Sarg, acquired in 1880. (5) A collection made by Mr. C. Patrick Geddes in Mexico (Vera Cruz, Puebla, and Mexico) and presented by him in 1880. (6) A series from Presidio, Sinaloa, collected by A. Forrer ; purchased in 1883, (7) A collection made by the Rev. J. Robertson in British Honduras; purchased in 1890 and 1891. (8) Two collections made in Mexico by Dr. A. C. Buller—one from Vera Cruz and Oaxaca, the other from Guanajuato, Jalisco and Michoacan; acquired in 1890 and 1892 respectively. (9) Series of fishes from the Rio Grande, Chihuahua, Salamanca, and Mexico City, collected by Mr. A. J. Woolman, and including a few co-types of species described by him; purchased in 1892, . (10) A collection from San Luis Potosi, including several co-types, received from Dr. D. S. Jordan in 1900. (11) Fishes collected by Dr. H. Gadow in Vera Cruz and Oaxaca in 1902. (12) Co-types of some of the species described by Gill and Bransford from Lake Nicaragua, sent by the Smithsonian Institution in 1906. (13) A few co-types of species described by Vaillant and Bocourt, received from the Paris Museum in 1906. (14) Recently acquired collections made in Costa Rica by H. Pittier, P. Biolley, H. Rogers and C. F. Underwood. In addition to these, we may mention three collections of marine fishes, containing examples of species new to the British Museum of Galeichthys, Mugil, Centropomus, and other genera which enter fresh water. Two of these are from Panama, one acquired from A. Boucard in 1875 and the other from Dr. Jordan in 1903; the third is from Mazatlan. received from Dr. Jordan in 1895 Vili INTRODUCTION. 3. CLASSIFICATION. The class Pisces, as understood in this work, includes craniate vertebrates with gills, and typically with median and paired fins which are supported by endoskcletal elements. Three sub-classes are recognized, viz. Cyclostomata, Selachii, and Teleostomi, which are, however, separated from each other by characters at least as trenchant as those which serve for the distinction of the classes of higher vertebrates, and which have therefore, with some reason, been considered as separate elasses, in which case the term Pisces has been restricted to the Teleostomi. The Teleostomi approach the Batrachians in that they have typically a lung or its homologue, the air-bladder, and in the development of membrane bones. The Batrachia are well separated, however, by the absence of dermal fin-rays and of endoskeletal supports for the median fins, by the modification of the paired fins into pentadactyle limbs and of the hyomandibular into the stapes, and by the presence of true internal nares. I especially lay stress on the Jast character, because the impression is prevalent that the Dipneusti have internal nares, and in this respect show affinity to the Batrachians. As a matter of fact, the Dipneusti, like other Teleostomes, have two external nasal openings on each side ; these are situated on the under side of the snout, and when the mouth is closed the posterior and, to a certain extent, the anterior are covered by the lower lip. The posterior nostril is also covered by the lower lip when the mouth is closed in some Eels (e. g. Ophichthys). | | True internal nares are quite different in structure and position to the posterior external nares of the Teleostomi, being paired perforations of the palate internal to the premaxillaries and maxillaries. Their ontogenetic development in the Batrachians, the lowest group in which they occur, supports the view that they are a new formation, | The Cyclostomes and Selachians are represented by only a few species in the fresh waters of Mexico and Central America, the bulk of the fish-fauna belonging to the Teleostomi, or bony fishes. These may be arranged in two series—Actinopterygian and Crossopterygian. In the fishes of the Actinopterygian series the branchiostegal rays and supports of the paired. fins retain their primitive condition or evolve by a simple process of concentration or reduction, whilst the duct connecting the air-bladder with the digestive tract, when persistent, opens dorsally or dorso-laterally into the latter. The fishes of the Crossopterygian series comprise the orders Crossopterygii and Dipneusti; these have INTRODUCTION. 1x the branchiostegal rays replaced by a pair of large gular plates (absent in some specialized Dipneusti), the paired fins more or less lobate, their basal supports becoming axial in the more specialized forms, and the duct of the air-bladder opening into the ventral part of the cesophagus. The Actinopterygian series includes two main groups which may be given ordinal rank; in the lower (Chondrostei) the clavicles (infra-clavicles) are distinct from the cleithra (clavicles), the pelvic fins have a well- developed series of radials, the median fins have the dermal rays more numerous than their endoskeletal supports, and the caudal fin is typically strongly heterocercal. The living members of this order are the Sturgeons (Acipenseride) and Paddle-fishes (Polyodontidee) ; neither family is represented in Mexico or Central America. In the more specialized group, the Teleostei, the clavicles do not exist as separate elements, the radials of the pelvic fins are absent or vestigial, the dermal rays of the median fins are equal in number to their endoskeletal supports, and the caudal fin is abbreviate heterocercal or homocercal. The Teleostei are the dominant group to which the great majority of living fishes belong ; their classification is by no means an easy matter. The genera Lepidosteus and Ama differ from other living Teleosts in the presence of a splenial and of a metapterygium, and in the absence of an endochondral supraoccipital ossification ; they have been regarded as belonging to a separate order, Holostei. Some of the supposed distinctive features of the Holostei have been found in undoubted Teleosts (Elopide, Albulide, Chirocentride), and a study of the fossils makes it still more difficult to recognize two orders, annectent forms (e. g. Dapedius, Pholidophorus) occurring. Lepidosteus is represented in the fresh waters of Mexico and Central America ; it is the type of the sub-order Ginglymodi, characterized by the opisthoccelous vertebra. The remaining Teleostei have a well-ossified endochondral supraoccipital, the lower jaw composed of three elements only (dentary, articulare, and angulare), and the pectoral radials all directly attached to the scapula and coracoid, the metapterygium being absent. The most generalized of these form the sub-order Malacopterygii, soft-rayed fishes with abdominal ventral fins, with a pneumatic duct, and with a mesocoracoid element in the pectoral arch. ‘This sub-order is represented in the fresh waters of Mexico and Central America by a few marine types. BIOL. CENTR.-AMER., Pisces, February 1908. b x INTRODUCTION. The fishes of the next sub-order, Ostariophysi, differ from the Malacopterygii in the modification of the superior and lateral elements of the anterior vertebra to form a chain of ossicles connecting the air-bladder with the auditory organ. This group is almost entirely composed of fresh-water fishes, and five of the six families recognized by Boulenger are represented in Mexico and Central America. The Ostariophysi agree with the Malacopterygii in having a mesocoracoid bone, but in the other groups to be considered this element has been lost. Of four groups of more or less anguilliform fishes, Lyomeri, Heteromi, Symbranchii, and Apodes, which appear to be independent offshoots of the Malacopterygii, the last two are represented in the rivers of Mexico and Central America. In the Symbranchii the body is eel-shaped, the dorsal and anal fins are continuous with the caudal, the ventral fins are absent, the gill-openings are confluent to form a single ventral slit, and the well-developed premaxillaries exclude the maxillaries from the border of the mouth. The Eels of the sub-order Apodes differ in having the small gill-openings usually separate and in having the mouth bordered above by the maxillaries, which are separated in the median line by the ethmo-vomer, to which the premaxillaries (if present) are suturally united. The sub-ordinal groups already mentioned appear to be natural and well-defined, but the next sub-order, Haplomi, which differs from the Malacopterygii only in the absence of a mesocoracoid, is less satisfactory, and includes four or five groups which may not be related. The Cyprinodontide are abundant in the rivers of Mexico and Central America. Recent researches have shown that some members of this family are physoclistic *, and that in others the lower pharyngeal bones are suturally united. On this account I would place the physoclistic Scombresocide, which have the lower pharyngeals completely united, near the Cyprinodontide in the sub-order Haplomi. In my opinion they are much more closely related to the Cyprinodontide than to the Atherinide, with which they have recently been associated. Most of the physoclistic Teleosts with abdominal ventral fins are placed by Boulenger in two sub-orders, Catosteomi and Percesoces, the former being distinguished from the latter by the supposed enlarged coracoid. In the ‘Cambridge Natural History’ Boulenger writes:—‘“'The whole question of the arrangement of the * Philippi, Sitzungsb. Gesellsch. naturf. Freund. 1906, p. 232, INTRODUCTION. xi physoclists with abdominal ventrals (Catosteomi and Percesoces) is, I feel, much in need of revision, and it may be found advisable to break up this group [Catosteomi|] into a greater number of sub-orders.” I have paid a good deal of attention to these groups, and am of opinion that they are unnatural and indefinable. After removal of the Selenichthyes, which I have recently been able to show are related to the Teniosomi, and of the Hypostomides, the remainder of the Catosteomi, which corresponds to the Hemibranchii of Smith Woodward, is still a heterogeneous assemblage which I find incapable of definition, and includes three well-marked but probably related groups which should, in my opinion, be given sub-ordinal rank. These are: (1) THoracoste1*, which have on each side a large dermal plate, which in the adult is co-ossified with the coracoid and suturally united to the clavicle ; (2) SoLENICHTHYES (nom. nov.), which have a considerable amount of dermal armour but no plates similar to the ectocoracoids of the Thoracostei—the tubiform snout, terminal toothless mouth, pectinate gills, and elongate anterior vertebre with separate transverse processes further characterize this group; (3) LopHosrancuil, differing from the Solenichthyes in the lobate gills and normal anterior vertebre. The resemblances between the Centriscide and the Solenostomide, respectively the most generalized of the Solenichthyes and the Lophobranchii, seem to indicate relationship, but are, no doubt, in great part due to similar modes of life. A few fishes belonging to the sub-order Lophobranchii are found in the rivers of Mexico and Central America. Adding the Osphromenide, which should, in my opinion, be placed with the Anabantide, and after removing the Scombresocide to the Haplomi, the Ammodytide and Champsodontide to the Percomorphi, and the Chiasmodontide (incert@ sedis), the families included by Boulenger in the Percesoces may be arranged thus :— I. Pelvic bones remote from the clavicles; a separate spinous dorsal; no supra- branchial organ; no esophageal sacs. «ww ee ee ee) Atherinide, Mugilide,, Polynemide, and Sphyrenide. II. A suprabranchial organ. . . . . . . Ophiocephalide, Anabantide, and Osphromenide. III. Gsophagus with a pair of lateral muscular sacs, with internal papille which may be toothed. . . 2. 2 2 e+ «© 6 © © © e es « Letrayonuride, Stromateide. IV. Pelvic bones remote from the clavicles; no fin-spines; no suprabranchial organ; no cesophageal sacs... 1. 6 6 6 1 ee we ew ee we + LeOsteide. In the second and third of these divisions we see the transition from abdominal * Swinnerton, Quart. Journ. Micr. Sci. xlv. 1902, p. 580, and xlix. 1905, pp. 369-380. b2 x11 INTRODUCTION. to truly thoracic ventral fins (with the pelvic bones directly attached to the clavicles) in the series Ophiocephalus, Anabas, Osphromenus and Tetragonurus, Centrolophus, Stromateus respectively, and in order to attain precise diagnoses it becomes necessary to regard each of these two groups as of primary, é. é. sub-ordinal, rank, and to neglect the character of the attachment of the pelvic bones in defining them. The first and second of these sub-orders have the names Percesoces and Labyrinthici respectively. For the third I propose the name Zenopharyngii, whilst the fourth, comprising fishes with the skeleton in great part cartilaginous, may be termed Malacichthyes. Of these groups only the Percesoces is represented in the fresh waters of Mexico and Central America. The sub-order Acanthopterygii, as understood by Boulenger, is defined by a single character, viz., the direct attachment of the pelvic bones to the pectoral arch. When the systematic portion of the present work was commenced, more than two years ago, the sub-order was accepted by me; but I now think that the fact has to be recognized that the pelvic bones have become directly attached to the clavicles in several groups and that a large group defined by this character alone is unnatural. It has been mentioned above that each of two natural groups, Zenopharyngii and __ Labyrinthici, includes forms with the pelvic bones remote from the clavicles and others in which they have acquired a direct attachment to the clavicles. In a third group, the Berycoids, the two conditions are also found, Polymixia exemplifying the first and Z'rachichthys the second. It seems pretty certain that the Cyttide and the Percoid fishes have evolved independently from the Berycoids, and we cannot lay much stress on the fact that the pelvic bones are directly attached to the clavicles in the two first-named groups as indicating any special relationship between them. Enough has been said to show that the Acanthopterygii should be split up into several sub-orders; two of these are represented in the fresh waters of Mexico and Central America, viz. Percomorphi and Heterosomata, the latter including the single family Pleuronectide. 4. GEOGRAPHICAL DISTRIBUTION. In discussing the distribution of fresh-water fishes we need not take notice of marine fishes (Centropomus, Pomadasis, Mugil, &c.) which ascend rivers for con- siderable distances, either in search of food er for breeding-purposes, nor need we consider fishes which descend the rivers to breed in the sea (e.g. Anguilla). Fresh-water species of marine genera (e.g. Chirostoma humboldtianum) and fresh- water genera of marine families (e.g. Aenatherina) have little importance. True INTRODUCTION. Xlll fresh-water fishes belong to families which are wholly (eg. Percidew, Cichlide) or chiefly (e.g. Cyprinodontide, Siluride) confined to fresh water. In Mexico and Central America these are the following:—Cichlide, Percide, Centrarchide, Cyprinodontide, Loricariide, Siluride, Cyprinide, Gymnotide, Characinidee, and Lepidosteide. The Cicuuipa are Perciform fishes which bear a considerable resemblance in appearance and anatomy to the most generalized group of Perciformes, the widely- distributed marine family Serranide, but differ from them in certain features of specialization, such as the presence of but a single nostril on each side, the absence of teeth on the palate, the coalescence or sutural union of the lower pharyngeals, and the reduced number of branchiostegal rays. No known fossils can be referred to the Cichlide, which inhabit America, from Texas to Montevideo, and Africa, including Madagascar. Seven species occur in Syria, and a single genus with three species inhabits Ceylon and Southern India. The American Cichlidea comprise over 150 species which may be arranged in 23 genera; from Africa more than 200 species referred to 35 genera have been described. Not one of the genera is common to Africa and America, but the South-American Acara is scarcely generically distinct from the African Paratilapia, and there can be no doubt that these are the most generalized of living Cichlide and very near to the ancestral type of the family. The Mexican and Central-American Cichlide are more specialized than the South- American ones, and have certainly been derived from them; not one of the genera with three anal spines is found north of the Isthmus of Panama, and all the South- American Cichlide have simple conical teeth. Of the Southern types only Cichlosoma has reached Mexico and Central America, and has there given rise to a variety of more specialized forms. We have no evidence in favour of dating the origin of the Cichlide before the Eocene. At the same time we have to explain their occurrence in South America, Africa, and India at the present day. . Boulenger, in his address to the Zoological Section of the British Association in 1905, whilst adopting a non-committal attitude, put forward the hypothesis that the Cichlide were originally a Northern group, and that in the Kocene they ranged over North America and Northern and Eastern Asia, which were then one continent, and that they have attained their present distribution by a southward migration and by becoming extinct in their original habitat. This view XIV INTRODUCTION. is supposed to be supported by the occurrence in the Eocene of Wyoming and Utah of a fish, Priscacara, which has been referred by some authors to the Cichlide. But Priscacara has neither the reduced number of branchiostegals nor the toothless palate which characterize all living Cichlid, and it appears to me that it has no bearing on the problem of how two very closely allied genera, Acara and Paratilapia, differing from it and agreeing with each other in some important features which are obviously due to their near relationship, have come to inhabit South America and Africa respectively. DIstRIBUTION oF CICHLID®. The Indian Kéroplus is an isolated type, more specialized than Paretroplus of Madagascar, which appears to be its nearest relative, and, as has already been stated, a study of the American Cichlide leaves no possible doubt that the Mexican and Central-American Cichlid fauna has originated with immigrants from South America ; consequently the hypothesis of the northern origin of the family should, I think, be rejected. We are therefore led to believe that in early Eocene times Africa was connected by land with South America on the one side and with India, vid Madagascar, on the other. The Mexican and Central-American Cichlide number about 65 species; they are INTRODUCTION. Xv not found on the Mexican Plateau, but in lowland rivers they extend northward to Sinaloa on the West and to the Rio Grande on the East. The South-American Acara and Geophagus are each represented by a single species in Panama. Most of the Mexican and Central-American Cichlide belong to the genus Cichlosoma, but usually to different sections of the genus from the South-American species. The section Theraps contains 21 species: 16 are from Guatemala and Mexico south of the Balsas, one of them ranging southwards to Panama; the most northern species occurs in the Panuco; whilst 3 are found in Lakes Managua and Nicaragua and 1 in Costa Rica. Archocentrus comprises 6 species, 5 from Guatemala and Southern Mexico and 1 from Lake Nicaragua.