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Scope of the Book
This is the second and final volume of the Fishes of the Gulf of Mexico, and it covers 693 species in 303 genera, 84 families, and four orders: Scorpaeniformes, Perciformes, Pleuronectiformes, and Tetraodontiformes. The format follows that of the first volume, except descriptions are somewhat expanded for the families of fishes, pertinent references are provided following the family accounts, and the number of species of the family known from the western Central Atlantic (Cape Hatteras, NC, to the equator) are placed between the total known worldwide and those recorded from the Gulf of Mexico. Also, the species accounts are expanded to include more distributional and ecological data, following advice of peers regarding the first volume. As in the first volume, the classification is according to J. S. Nelson (1994), with the following exceptions: Peristediinae is treated as a family, following advice of William Richards. The percoid genera Howella and Symphysanodon are treated as distinct families, Howellidae and Symphysanodontidae, respectively, because neither shares synapomorphies with other percoid taxa (G. David Johnson, pers. comm., July 1999). Nelson (1994) placed Howella in Acropomatidae and Symphysanodon in Lutjanidae. The family Kyphosidae was interpreted according to G. D. Johnson and R. A. Fritzsche (1989), that is, limited to four genera (Hermosilla, Kyphosus, Neoscorpis, and Sector). Poecilopsettinae was also treated as a family rather than as a subfamily of Pleuronectidae, following Chapleau and Keast (1988) and Chapleau (1993). Unlike the first volume, in which families were largely arranged alphabetically within orders, in this volume, families within orders are arranged according to Nelson (1994). Families that are not recognized by Nelson immediately follow the family to which they are thought to be most closely related; for example, Symphysanodontidae follows Lutjanidae.
The eastern boundary of the Gulf of Mexico is a line connecting Cape Catoche, near the eastern tip of the Yucatán Peninsula, and Key West, Florida (Fig. A). This boundary, which essentially follows that of R. H. Backus and J. E. Craddock (1977), is the same recognized in the first volume, and it thus excludes the Florida Keys and the northwestern coast of Cuba from the Gulf of Mexico. Florida Bay, on the other hand, is considered to be in the Gulf.
As was the case in the first volume, the fish species composition of the Gulf of Mexico was based on extensive review of the literature and unpublished species lists, and on surveys of the major natural history collections of the United States and Mexico. An attempt was made to survey all of the major natural history collections with holdings from the Gulf of Mexico, and the following institutions were included: Academy of Natural Sciences, Philadelphia (ANSP), PA; American Museum of Natural History (AMNH), New York, NY; Field Museum of Natural History (FMNH), Chicago, IL; Florida Board of Conservation Fish Collection (FBC), St. Petersburg, FL; Florida Museum of Natural History (FM), Gainesville, FL; Gulf Coast Research Laboratory (GCRL), Ocean Springs, MS; Museum of Comparative Zoology (MCZ), Cambridge, MA; Milwaukee Public Museum (MPM), Milwaukee, WI; National Museum of Natural History (USNM), Washington, D.C.; Texas Cooperative Wildlife Collection (TCWC), College Station, TX; Texas Natural History Collection (TNHC), Austin, TX; Tulane Museum of Natural History (TU), New Orleans, LA; Universidad Nacional Autónoma de México (UNAM), Mexico City; University of Alabama Ichthyological Collection (UAIC), Tuscaloosa, AL; and University of Michigan Museum of Zoology (UMMZ), Ann Arbor, MI. (The above acronyms follow Leviton et al. ). Over the course of the project, one to four weeks were spent at each of these institutions.
How to Identify Fishes
The fishes included in the second volume are more morphologically similar in shape than those covered in the first volume but still display considerable variation in shape and size. The same methods used in the first volume apply for making measurements and counts, but some of these are further elaborated. Proportional measurements are based on standard length (SL), head length (HL), and occasionally on fork length (FL). Standard length is the distance from the tip of the snout to the end of the hypural plate and is determined by bending the tail against a flat surface and measuring to the seam representing the junction between the hypural plate and the fin rays. The hypural plate forms the surface onto which the caudal fin rays attach medially. Head length is the straight-line distance between the tip of the snout and the opercular flap (Figs. B and C). Fork length is used in fishes such as carangids that have bony scutes running along the posterior section of the lateral line to the base of the caudal fin. The scutes make it difficult to accurately determine the end of the hypural plate. For this reason, proportional lengths are expressed in percentage of fork length rather than in percentage of standard length. Fork length is measured from the tip of the snout to the midlateral margin of the caudal fin when the fin is expanded dorsoventrally. All measurements are made from point to point.
Many of the fishes included in the second volume have the ultimate dorsal fin ray and anal fin divided to the base, thus care must be taken if this is the case to count the two sections of the ray as one ray. The gill raker counts on the first gill arch in the text include all elements, even the rudiments, unless otherwise stated in the text. Rudiments are generally considered elements that are wider than they are tall. Pectoral fin counts given in the text refer to all elements, whether branched or unbranched, paired or single. In some literature sources, especially older references, the short unbranched, unpaired elements are given as lowercase Roman numerals. Lateral line scale counts are inclusive of pored, tubed, or grooved scales from above the operculum to the end of the caudal peduncle. In some accounts, lateral line scales posterior to the caudal peduncle are given separately: 35+1+1, as for the scorpaenids. Horizontal scale series are those between the upper free margin of the operculum and the caudal peduncle. The scales between the origin of the dorsal fin and the lateral line are counted diagonally and posteriorly from the base of the first dorsal fin spine (ray) to the lateral line. The scales between the lateral line and the anal fin origin are counted diagonally and anteriorly from the origin of the anal fin to the lateral line.
Biogeography of Fishes of the Gulf of Mexico
Species Richness and Composition and Biogeographical Affinities
Based on distributional patterns of continental shelf species, the Gulf of Mexico is considered both a warm temperate and a tropical body of water (Briggs 1974). Its northern section, Cape Romano, FL, to Cape Rojo, Veracruz (see Fig. A), is warm temperate and shares faunal elements with the remainder of the Carolinian province (Cape Hatteras, NC, to Cape Canaveral, FL). Its southern sections—Cape Rojo to Cape Catoche, Yucatán, and the west coast of Florida south of Cape Romano—are tropical and share faunal elements with the Caribbean province. Based on the distribution of mesopelagic fishes, such as myctophids, the Gulf of Mexico is considered distinct but most similar to the Atlantic Tropical Region (Backus et al. 1977). J. V. Gartner et al. (1987) and C. Karnella (1987) also noted similarities as well as some differences in species composition of myctophids between the eastern Gulf of Mexico and the tropical Atlantic. According to Backus et al. (1977), the Gulf undergoes significant winter cooling and, possibly because of this cooling, also shares species with the Atlantic Tropical-Subtropical, the Atlantic Tropical-Semitropical, and the Atlantic Temperate-Semitropical regions. Unlike J. C. Briggs (1974), Backus et al. (1977) considered the Gulf to be undivided and to constitute both a biogeographical region and a province, although no myctophid species are endemic to the Gulf of Mexico. R. H. Gibbs et al. (1983) and T. T. Sutton and T. L. Hopkins (1996) found the stomiid mesopelagic assemblage (Astronesthidae, Chauliodontidae, Idiacanthidae, Malacosteidae, Melasnostomiidae, and Stomiidae) of the Gulf of Mexico to be significantly different from that of the tropical Atlantic in both species richness and composition. According to all of the above interpretations, the Gulf of Mexico shares tropical and warm temperate species with the Atlantic Ocean and is most similar in species composition to the western Central Atlantic region (Cape Hatteras, NC, to the equator).
The present two-volume study documents 1,443 fish species in 677 genera, 222 families, and 45 orders in the Gulf of Mexico (765 species in 390 genera, 138 families, and 40 orders in volume 1; 657 species in 280 genera, 84 families, and 4 orders in this volume; and 23 additional species in 7 genera, 3 families, and 1 order and 2 species and 1 genus deletions to accounts included in volume 1). Another 42 species in 8 additional genera and 2 families are included because of the likelihood that they occur but to date have not been documented from the Gulf. Based on several published and unpublished studies (Rosen 1973; Compagno 1984; W. J. Richards and M. Leiby, pers. comm., December 2001; McEachran and de Carvalho 2002), there are about 2,247 species of fishes in 858 genera, 241 families, and 45 orders in the western Central Atlantic. Thus 64.3 percent of the species, 79.4 percent of the genera, 92.5 percent of the families, and all of the orders of fishes recorded from the western Central Atlantic have been documented from the Gulf of Mexico. Families represented in this area but not represented in the Gulf are mostly deep-sea and oceanic fishes and, to a lesser extent, temperate fishes rare south of Cape Hatteras or tropical fishes rare north of Central America or west of the Bahamas or Greater Antilles.
Deep-sea families present in the western Central Atlantic but not in the Gulf of Mexico include Heterenchelyidae, Derichthyidae, Muraenesocidae, Cyematidae, Saccopharyngidae, Monognathidae, Radiicephalidae, Parabrotulidae, Caulophrynidae, Neoceratiidae, Gigantactinidae, Megalomycteridae, and Oreosomatidae (W. J. Richards and M. Leiby, pers. comm., December 2001). The sill depths of the Straits of Yucatán (2,040 m) and the Straits of Florida (800 m) and, more importantly, the deepest sill depths between the Caribbean Sea and the Atlantic Ocean, which are the Windward (1,540 m), the Jungfern (1,815 m), and the Anegada (1,910) Passages, may exclude some of these families.
Temperate fishes known from the western Central Atlantic but not from the Gulf of Mexico include Anotopteridae, Psychrolutidae, Cyclopteridae, Ammodytidae, and Scophthalmidae (W. J. Richards and M. Leiby, pers. comm., December 2001). These families are rare south of Cape Hatteras.
Tropical families known from the Caribbean Sea but not from the Gulf of Mexico include Anomalopidae and Synbranchidae. There is only one species of anomalopid in the western Atlantic, and most species of synbranchids are limited to freshwater or brackish water.
Most of the species (in families represented in the Gulf) occurring in the western Central Atlantic but not in the Gulf of Mexico are distributed either south of the Gulf of Mexico or in the insular regions to the east (the Bahamas, the Greater Antilles, and the Lesser Antilles). These species may be excluded by a variety of factors, including environmental parameters, habitat availability, and dispersal abilities of the fishes. The Gulf of Mexico has greater seasonal temperature changes than regions to the south or east (Backus et al. 1977), and this greater variation may exclude some stenothermal species. The Gulf of Mexico lacks extensive reef habitats, unlike the Caribbean coast of Central and South America, and the Bahamas and the Antilles, and this deficiency may exclude some reef-dependent species. Secretive reef-dwelling or reef-associated species of the western Central Atlantic, such as Grammatidae (with 2 of 11 species in the Gulf), Opistognathidae (with 7 of 17 species), Dactyloscopidae (with 4 of 17 species), Labrisomidae (with 19 of 41 species), Chaenopsidae (with 11 of 40 species), Gobiesocidae (with 2 of 25 species), and Gobiidae (with 57 of 124 species), are relatively less diversely represented and/or widely distributed in the Gulf than the larger and more conspicuous reef dwellers, such as Chaetodontidae (with 6 of 8 species in the Gulf), Labridae (with 17 of 19 species), Scaridae (with 14 of 14 species), Acanthuridae (with 3 of 3 species), and Balistidae (with 6 of 6 species). Pomacentridae (with 14 of 20 species in the Gulf) often occupy small ranges on coral reefs, but they have pelagic eggs and larvae that widely disperse, unlike many of the secretive reef dwellers that either have benthic eggs or are mouth brooders. Many species of Engraulidae (with 8 of 29 species in the Gulf), Ariidae (with 7 of 21 species), Batrachoididae (with 5 of 20 species), and Sciaenidae (with 26 of 59 species) are distributed along the continental coast of the Caribbean, from northern South America to Honduras or Belize, and may be limited by relatively greater seasonal temperature changes in the Gulf than in the areas of the Caribbean. Clupeidae (with 16 of 21 species in the Gulf), Macrouridae (with 30 of 35 species), Holocentridae (with 11 of 11 species), Triglidae (with 14 of 19 species), Serranidae (with 61 of 89 species), Carangidae (with 28 of 32 species), Lutjanidae (with 16 of 18 species), Gerreidae (with 12 of 12 species), Haemulidae (with 18 of 23 species), and Sparidae (with 16 of 19 species) are well represented in the Gulf. These taxa generally are wide-ranging pelagic or demersal/benthic species, occur on a variety of substrates, or are common on soft bottoms that are widely distributed in the Gulf.
Alternatively, historical factors may be responsible for the absence of species from the continental shelves and slopes of Central and South America in the Gulf of Mexico. Robins (1971) stated that shore fishes of the western central Atlantic are divided into three assemblages: a northern continental assemblage, a central insular assemblage, and a southern continental assemblage. Continental assemblages are typical of continental shelves where water temperatures, salinities, and turbidity levels vary with terrestrial weather patterns and terrigenous substrates predominate. Many species of the continental assemblage are associated with estuaries and areas where rivers meet the coast. Insular assemblages are typical of insular shelves where oceanic water masses buffer the aquatic habitat from terrestrial weather patterns, turbidity is low, and carbonate substrates predominate. Many species of the insular assemblage are associated with coral reefs. The northern continental assemblage extends from Cape Canaveral on the east coast of Florida, around the tip of Florida, and westward throughout the Gulf of Mexico. The southern continental assemblage extends from northern Brazil to Nicaragua. The insular assemblage extends throughout the Bahamas, the Greater and Lesser Antilles, and barrier reefs off Belize and Quintana Roo. Components of the northern and southern continental assemblages are interspersed with the insular assemblage around Cuba, Hispaniola, and Jamaica in areas where rivers discharge into the sea and terrigenous substrates predominate. Correspondingly, components of the insular assemblage are interspersed with the northern and southern continental assemblages along continental shelves where hard substrates predominate and river mouths are lacking.
A recent biogeographical study of the fishes of the western Central Atlantic offers support for Robins' categorization of the region and suggests that faunal differences between the northern and southern continental shelf assemblages are historical (Smith et al. 2002). Smith et al. (2002) mapped the distribution of 987 fish species occurring in the western Central Atlantic and found areas of highest diversity in waters around southern Florida, the eastern Bahamas, northern Cuba, and to a slightly lesser degree, continental waters of South America, Central America, and the northern Gulf of Mexico. They found the highest levels of endemism to be in southern Florida, the coast of South America off Venezuela and Colombia, and the northern Gulf of Mexico. The fishes around southern Florida, eastern Bahamas, and northern Cuba are mostly components of Robins' insular fish assemblage, and the fishes from northern South America, Central America, and the northern Gulf of Mexico are components of Robins' southern and northern continental shelf assemblages. Smith et al. (2002) also found that the continental shelf fishes could be placed in four categories: ubiquitous species (found throughout the area; 10 species), species restricted to very small regions of the area (86 species), species that enter the area from the east coast of North America (northern component comprising 49 species), and species that enter the area from the east coast of South America (southern component comprising 67 species). The latter two categories are biogeographically informative. Members of the first category are universally present, thus they do not provide any information. Members of the second category occupy very small ranges that in composite do not reflect obvious vicariant patterns. Only 18 percent of the northern component extends south of Cape Catoche, and only 19 percent of the southern assemblage extends north of Nicaragua. Thus the third and the fourth categories support the presence of two distinct continental faunal assemblages: a warm temperate one that enters the area from the north, and a tropical component that enters the area from the south. These two components represent Robins' northern and southern continental assemblages, respectively.
This pattern suggests that the northern and southern continental assemblages had separate evolutionary patterns, and this hypothesis is supported by tectonic history of the western Central Atlantic. An inter-American seaway existed between North and South America for much of the history of the Caribbean Basin (Smith et al. 2002). The seaway opened with the breakup of Pangaea and Gondwanaland in the early Mesozoic and late Mesozoic (see "Geological History of the Gulf of Mexico" in volume 1: 5-6). The seaway was open at all depths until the mid Miocene, thus until the mid Miocene it probably served as a barrier to continental shelf and coastal fishes on either side of the seaway. The seaway was partially closed by submarine ridges between the mid and late Miocene and was completely closed by the Panamanian Isthmus in the late Pliocene (2.76 to 2.51 Ma). Thus the deep-sea barrier between South America and North America ended between the mid to late Miocene and the late Pliocene, depending on the depth ranges of the fish species on either side. These geological events may explain many of the faunal differences between the two continental shelf assemblages in the western Central Atlantic and why a number of fish species abundant on the Caribbean continental shelf are lacking from the Gulf of Mexico.
Considering its size, the Gulf of Mexico has a relatively rich fish fauna (Table 1). The Gulf has about 200 more species and 36 more genera than occur in the eastern Atlantic Ocean between the Arctic and the southern coast of Morocco, including the Mediterranean (Whitehead et al. 1984-1986), and within 118 species and 76 genera of the number that occur in the eastern Atlantic from the coast of Morocco to southern Namibia (Quéro et al. 1990). Nearly 10 percent of the world's known marine fish species occur in the Gulf of Mexico (Nelson 1994).
The uniqueness of the Gulf of Mexico stems more from the richness of its fish fauna than from a high percentage of endemic species. Only 66 species of the total 1,443 species (4.6%) can be considered endemic to the Gulf of Mexico (Table 2). Endemicity as used here is liberally defined: species are considered to be endemic if they are largely limited to the Gulf, even if they also occur along the southeastern coast of Florida, the eastern coast of Yucatán, or the Florida Keys. Excluding species along the east coasts of Florida and Yucatán would greatly reduce the percentage of endemic species. Also, Dorosoma petenense is considered endemic despite the fact that only adults are found in brackish to low-salinity waters of the Gulf, with younger life stages limited to freshwater. The majority of the endemic species are limited to one or two of the three subregions (eastern, northwestern, or southern, described below) and display several distributional patterns. Only 9 endemic species occur throughout the Gulf. Eleven species endemic to the northern or western Gulf have either a sister species or a phenotypically similar species that occurs along the eastern seaboard of the United States (e.g., Leucoraja lentiginosa, Brevoortia gunteri, B. patronis, Alosa alabamae, A. chrysochloris, Prionotus martis, Cynoscion arenarius, Chasmodes longimaxilla, Peprilus burti, Gymnarchirus texae, and Sphoeroides parvus). The east-coast putative sisters of these species are Leucoraja garmani, Brevoortia smithi, B. tyrannus, Alosa sapidissima, A. mediocris, Prionotus carolinus, Cynoscion regalis, Chasmodes bosquianus, Peprilus triacanthus, Gymnachirus melas, and Sphoeroides maculatus, respectively. The emergence of the Florida Peninsula between the end of the Pliocene and the middle of the Pleistocene (Bowen and Avis 1990) may have been the vicariant event leading to speciation in these cases. Five species that are widely distributed along the eastern coast of the United States, Ascipenser oxyrhynchus (Ascipenseridae), Morone saxatilis (Moronidae), Centropristis striata (Serranidae), Larimus fasciatus (Sciaenidae), Etropus cyclosquamus (Paralichthyidae), have or had isolated populations in the northern Gulf of Mexico, suggesting that the Gulf populations are or were remnants of western extremes of once continuous populations (Smith et al. 2002). Apparently the time interval of 300,000 to 1,000,000 years since the emergence of the Florida Peninsula was insufficient for the Gulf and east-coast populations of these two species to have formed separate species (Bowen and Avis 1990; Galloway et al. 1991). The Gulf population of Morone saxatilis may no longer exist because of the introduction of specimens of the east-coast population into the Gulf that may have swamped their genome. Two of the northern and western Gulf endemics with sister species in the Atlantic, Chasmodes longimaxilla and Sphoeroides parvus, have another congener (C. saburrae and S. nephelus, respectively) distributed in the eastern Gulf of Mexico and along the Florida Peninsula (Springer 1959; Shipp and Yerger 1969a,b; Williams 1983). In both cases, the peninsular species is likely the sister of the species pair allopatrically distributed along the east coast of the United States and in the northern or western Gulf of Mexico. Florida consisted of one or more islands during the Miocene (Riggs 1984; Galloway et al. 1991; Riggs et al. 1991; Salvador 1991), and the peninsular form may have undergone speciation from the ancestral species of the present-day east-coast and Gulf species during this time. The relationships of the other 55 endemic species are not sufficiently known to comment on their evolutionary patterns. Some of these 55 species are known from very few specimens (e.g., Paramaturus campechiensis, Raja ackleyi, Eustomias leptobolus, Stemonosudis bullisi, Uncisudis advena, and Oreirodes bradburyae), and many or all may ultimately be known from areas outside the Gulf.
The Gulf of Mexico as a BioGeographical Region
According to Briggs (1974), a cohesive biogeographic region or biogeographic province is defined by the percentage of endemic species. Areas have to have at least 10 percent endemic species to be considered provinces. Based on endemicity, the Gulf of Mexico cannot be considered a province. However, based on its high diversity of fish species and its unique warm temperate and tropical components of species, the Gulf of Mexico is a unique biogeographical region. Its uniqueness may, in part, be due to a combination of physical factors. Its mouth straddles the Tropic of Cancer, and it has rather deep sills in the Straits of Yucatán (2,040 m) and in the Straits of Florida (800 m), thus it is accessible to warm temperate and tropical shore fishes and to most deep-sea pelagic and benthic fishes. It is surrounded on three sides by large landmasses, and the proximity of land may be responsible for the significant winter cooling of the water column, compared to the Tropical Atlantic region. Furthermore, the eastern Gulf of Mexico is dominated by the Florida Loop Current, which enters the Gulf through the Yucatán Straits, extends variably westward and occasionally to the mouth of the Mississippi River, and exits through the Florida Straits (McEachran and Fechhelm 1998 and references therein). The current is a regular source of tropical pelagic fauna for the Gulf. Warm-core rings that spin off the Florida Loop Current can transport pelagic organisms into the western Gulf of Mexico.
The fishes of the Gulf of Mexico display a number of distributional patterns (see Table 3) but support the conclusions of Briggs (1974) and Backus et al. (1977) that the species assemblages of the Gulf include both warm temperate and tropical components. The Gulf of Mexico shares 812 species with the southeastern United States (Cape Hatteras to Cape Canaveral), and many of these species are in the families Triglidae, Sparidae, Sciaenidae, Blenniidae, and Paralichthyidae. The Gulf shares 1,037 species with the Caribbean coast of Central and South America, and many of these fishes are in the families Ophichthidae, Congridae, Scorpaenidae, Centropomidae, Pomacentridae, Labridae, Scaridae, Labrisomidae, Chaenopsidae, and Bothidae. Gulf of Mexico species of Serranidae, Carangidae, and Lutjanidae appear to be more or less equally distributed along the Atlantic coasts north and south of the Gulf of Mexico. The Gulf shares 563 species with the Bahamas, 848 species with the Greater Antilles, and 770 species with the Lesser Antilles. The majority of these fishes are wide ranging throughout the western Central Atlantic (Scorpaenidae, Serranidae, Apogonidae, Carangidae, Lutjanidae, Haemulidae, Chaetodontidae, Pomacanthidae, Pomacentridae, Labridae, Scaridae, Balistidae, Monacanthidae, Ostraciidae, Tetraodontidae, and Diodontidae). Other species, representing Tripterygiidae, Chaenopsidae, Labrisomidae, and Gobiidae, are more restricted in their distributions and mostly limited to islands and barrier-reef habitats of the Caribbean Sea. These reef-associated species are generally best represented in the eastern and southern Gulf of Mexico.
About half (48.8%) of the 1,443 species occur throughout the Gulf and may, in a broad sense, be considered ubiquitous within their respective depth ranges. A majority of the ubiquitous species are wide-ranging epipelagic fishes (Carcharhinidae, Clupeidae, Belonidae, Exocoetidae, Hemiramphidae, Carangidae, and Scombridae), wide-ranging mesopelagic fishes (Gonostomatidae, Sternoptychidae, Phosichthyidae, and Myctophidae), wide-ranging benthic fishes of the continental shelf (Holocentridae, Serranidae, Lutjanidae, and Sciaenidae), and benthic slope or rise fishes (Ipnopidae, Macrouridae, and Moridae). The ubiquitous species are also widely distributed in other regions of the western Central Atlantic and, in some cases, in other regions of the Atlantic, Pacific, and Indian Oceans.
The remaining 51.2 percent of the 1,443 species are restricted to subregions of the Gulf, such as the eastern subregion (Dry Tortugas and Florida Bay to Pensacola, FL, or Mobile Bay, AL), the northwestern subregion (Pensacola, FL, or Mobile, AL, to Cape Rojo, Veracruz), the southern subregion (Cape Rojo to Cape Catoche, Yucatán), or to combinations of these subregions. A total of 14.6 percent (211 species) occur only in the eastern subregion. A large percentage of these species are in the families Ophichthidae, Alepocephalidae, Melanostomiidae, Notosudidae, Paralepididae, Syngnathidae, Opistognathidae, Apogonidae, Chaenopsidae, and Gobiidae. The high diversity of mesopelagic fishes in the eastern subregion may reflect sampling bias or intrusion of the Loop Current into the eastern Gulf of Mexico (Sutton and Hopkins 1996). Thomas Hopkins, of the University of South Florida, has maintained a meso-bathypelagic sampling station on the west coast of Florida for 19 years (Sutton and Hopkins 1996), and this water column by far is the best sampled in the Gulf of Mexico. The high diversity of reef-associated fishes (Opistognathidae, Apogonidae, Chaenopsidae, and Gobiidae) is probably related to the predominance of calcareous substrata along the west coast of Florida and the proximity to the Florida Keys. A number of reef-associated species have been reported only from the Dry Tortugas (Longley and Hildebrand 1941). About 3.6 percent of the Gulf species are limited to the northwestern subsection. A number of these species are either endemic to the Gulf of Mexico or also occur along the southeastern United States. Others such as Harriotta raleighana, Odontapsis noronhai, Aplatophis chauliodus, Labichthys carinatus, Asquamiceps caeruleus, Talismania antillarum, Brotulotaenia brevicauda, Bellotia atra, Kuma sp., Oneirodes bradburyae, Chiasmodon subniger, Pseudoscopelus obtusifrons, and P. scriptus are deep-sea fishes known from relatively few specimens, and they may turn up in other subregions of the Gulf. About 6.4 percent of the species are limited to the southern Gulf of Mexico, and the majority of these species also occur in the Caribbean Sea. Very few species that are restricted to the southern subregion are endemic to the Gulf of Mexico, suggesting that, unlike the Florida Peninsula, the Yucatán Peninsula has not served as a biogeographic barrier (Smith et al. 2002). About 17.5 percent of the species are restricted to the northern Gulf (eastern and northwestern subregions), and the majority of these species are also distributed along the eastern seaboard of the United States. About 3 percent of the species are restricted to the western Gulf (northwestern and southern subregions), and some of these species have disjunct populations along the eastern seaboard of the United States. About 5.3 percent of the species are restricted to the eastern and southern Gulf of Mexico, and many of these species are associated with reefs and also occur in the Florida Keys, the Bahamas, and the Greater and Lesser Antilles.
All of these distributional patterns appear to reflect geological and oceanographic conditions in combination with habitat factors. Benthic species associated with terrigenous substrates occur in the northern and western sections of the Gulf, and benthic fishes associated with calcareous substrates are associated with the calcareous shelves of Florida and Yucatán. Species with warm temperate affinities are generally found in the northern Gulf, and those with tropical affinities are generally found in the southern Gulf. The highest diversity of species (1,259) occurs in the eastern Gulf (Florida Bay to Pensacola or Mobile). The western Gulf (Pensacola or Mobile to Cape Rojo has slightly fewer species (1,056), and the southern Gulf (Cape Rojo to Cape Catoche) has the lowest number of species (916). These differences may partially reflect sampling or survey intensity, since the northern Gulf has been more intensely sampled than has the southern Gulf. Most of the deepwater-column surveys have taken place off northern Florida, and this may account for the larger number of midwater fishes occurring in the eastern Gulf of Mexico. However, it is possible that a number of the midwater fishes captured in the eastern Gulf were collected in the Loop Current, and thus they may not be part of the midwater fauna of the Gulf of Mexico.
The Gulf of Mexico shares 512 species with the eastern Central Atlantic, 364 species with the eastern North Atlantic, and 308 species with South Africa. The majority of the amphi-Atlantic fishes are neritic coastal species; epipelagic, mesopelagic, or bathypelagic oceanic species; or deep-sea benthic species, including members of Echeneidae, Exocoetidae, Coryphaenidae, and Carangidae (neritic coastal fishes); Scombridae, Xiphiidae, Nomeidae, Ariommatidae, and Molidae (epipelagic fishes); and Stomiiformes, Aulopiformes, Myctophidae, Ceratioidei, Bramidae, Chiasmodontidae, and Gempylidae (meso- and bathypelagic fishes). Benthic continental-shelf species make up about 16 percent of the amphi-Atlantic species and include several species each from the following families: Muraenidae, Congridae, Serranidae, Lutjanidae, and Labridae, and a single species each from the following families: Ophichthidae, Gerreidae, Sparidae, Pomacanthidae, Scaridae, and Bothidae. The majority of these demersal species appear to have achieved their amphi-Atlantic distributions by chance dispersal of eggs and larvae. All of the species have pelagic eggs and larvae that apparently can occasionally survive transatlantic dispersal events. The relatively high percentages of amphi-Atlantic species of Muraenidae, Congridae, and Acanthuridae may be due to their long-lived pelagic larval stages (Leis and Rennis 1983). The high percentage of amphi-Atlantic species of Balistidae, Monacanthidae, Tetraodontidae, and Diodontidae may be due to their extended pelagic juvenile stages (Leis and Rennis 1983; Aboussouan and Leis 1984; Leis 1984) and their association with pelagic sargassum (Dooley 1972). Sargassum passively drifts around the North and South Atlantic water gyres, and a diverse fauna of larval and juvenile fishes is associated with the sargassum.
The Gulf of Mexico shares 146 species with the eastern Central Pacific and 82 species with the eastern North Pacific. The majority of these are epipelagic, mesopelagic, and bathypelagic oceanic species that are circumtropical. A few are wide-ranging neritic species, such as Coryphaena equisetus, C. hipurus, and Pomatomus saltatrix, and wide-ranging demersal fishes with juvenile stages that are associated with sargassum.
The Gulf of Mexico shares 463 (68%) genera and 190 families (86%) with the eastern Central Atlantic, 358 (52.6%) genera and 172 (90.5%) families with the eastern North Atlantic, and 421 (61.8%) genera and 200 (90.5%) families with South Africa (eastern South Atlantic/southwestern Indian Ocean; Table 3). Most of these genera and families consist of neritic coastal species; epipelagic, mesopelagic, or bathypelagic oceanic species; or deep-sea benthic species. Few clupeid or engraulid genera are amphi-Atlantic, possibly because many of the species in the Gulf of Mexico are coastal pelagics that are associated with estuaries. Among the demersal continental-shelf taxa, a majority to all of the muraenid, ophichthid, congrid, pomocentrid, labrid, and scarid genera are amphi-Atlantic, but the majority of the triglid, serranid, haemulid, sparid, sciaenid, labrisomid, and gobiid genera are not.
The Gulf of Mexico shares 390 (57.3%) genera and 180 (81.5%) families with the eastern Central Pacific and 242 (35.5%) genera and 152 (68.8%) families with the eastern North Pacific (see Table 3). Most of these genera and families are neritic coastal; epipelagic, mesopelagic, or bathypelagic oceanic species; or deep-sea benthic species. More genera of Clupeidae and Engraulidae are shared between the eastern Central Pacific and the Gulf of Mexico than between the eastern Atlantic and the Gulf of Mexico. Amphi-American distribution patterns are common in several demersal continental-shelf families: Ophichthidae, Syngnathidae, Triglidae, Serranidae, Haemulidae, Sciaenidae, Dactyloscopidae, Chaenopsidae, Labrisomidae, Eleotridae, Gobiidae, and Paralichthyidae. In all cases, the amphi-American genera are endemic to the New World. The families Dactyloscopidae, Chaenopsidae, and Achiridae are also endemic to the New World. The amphi-American genera and families diverged from their ancestral taxa as the Central and South Atlantic Ocean formed and created a barrier between the New World and the source faunas in the eastern Atlantic and Indo-Pacific. Most of these amphi-American taxa are associated with shore zones and have limited means of dispersal. The ophichthyid genera, with pelagic leptocephalous larvae, may be exceptions, but little is known of their early life history.
Based on this analysis, the Gulf of Mexico is a diverse subregion of the western Central Atlantic but not a biogeographic province. The high diversity of fish taxa is a function of the range of habitat diversity and access to fauna of the western Central Atlantic. Over most of the geological history of the Gulf, the Florida and Yucatan Peninsulas were submerged (Salvador 1991) and did not serve as vicariant mechanisms.
Appendix: New Records and Emendations to Fishes Included in Volume 1 of Fishes of the Gulf of Mexico
Between the times of submission of the first and second volumes, a number of discrepancies were noted in the taxa treated in the first volume. These discrepancies are the result of overlooking literature records of fishes reported from the Gulf, overlooking museum specimens from the Gulf, or becoming aware of new literature sources that were not available before the first volume went to press. For these reasons, an appendix is added at the end of the introduction to provide an annotated list of these new records. The species records include distributional information, a designation of where the new record goes in the key to the species of the Gulf of Mexico published in the first volume, and diagnostic characters distinguishing the new record from the species diagnosed by the couplet. Literature records and museum catalog numbers are provided where appropriate.
New record: Harriotta raleighana (Goode and Bean, 1894)
This record is based on a video recording of a live specimen taken off the coast of Louisiana, in Mississippi Canyon (ca. 27°30'N, 88°50'W) at 1,920 m. Previously it was known from the western Atlantic between Chesapeake Bay and Nova Scotia, the eastern Atlantic, the southwestern Atlantic, and the Pacific Ocean (Stehmann and Bürkel 1984). This species is distinguished from the only other species of rhynochimaerid known from the Gulf of Mexico (Rhinochimaera atlantica) by possessing a series of large denticles on dorsal margin of the caudal fin (Bigelow and Schroeder 1953).
New record: Scyliorhinus meadi Springer, 1966
Espinosa Pérez and Huidobro-Campos (1995) reported this species from the southern Gulf of Mexico at three localities: 22°32'N, 90°54'W, 413 m; 22°30'N, 91°03'W, 431 m; and 22°29'N, 91°04'W, 451 m. Previously it was known from North Carolina to the east coast of Florida and from the Bahamas to northern Cuba (Compagno 1984). This species keys to couplet 3a in the scyliorhinid key (McEachran and Fechhelm 1998: 61). It is distinguished from S. retifer by its lack of a color pattern of black lines; instead, it is patterned with seven or eight dusky saddle markings on upper body (Compagno 1984).
New record: Mustelus higmani Springer and Lowe, 1963
Heemstra (1997) reported this species from DeSoto Canyon (29°11'N, 87°17'W) at 1,281 m. Previously it was known from the Gulf of Venezuela and Trinidad to Santos, Brazil (Heemstra 1997). This species is distinguished from the other three species of Mustelus in the Gulf of Mexico by the following combination of characters: denticles are tridentate between first dorsal fin and pectoral fin origins; orbit diameter is 2.2% to 3.4% of TL; upper labial fold is about equal to lower labial fold; and snout is 6.9% to 10% of TL (Heemstra 1997).
New record: Mustelus sinusmexicanus Heemstra, 1997
Heemstra described this species from the Gulf of Mexico, from Panama City to Campeche Bay, between 36 and 229 m. Previously it was confused with M. canis or possibly with M. norrisi. This species is distinguished from the other three Mustelus species in the Gulf of Mexico by the following combination of characters: Denticles are tridentate between first dorsal fin and pectoral fin origins; orbit diameter is 2.2% to 3.4% of TL; upper labial fold is distinctly longer than lower labial fold; and snout is 5.4% to 6.3% of TL (Heemstra 1997).
Replacement name: Etmopterus robinsi Schofield and Burgess, 1997
Schofield and Burgess (1997) described this species for specimens that had previously been recognized as E. hillianus (Poey, 1861) from the Gulf of Mexico and off Nicaragua, and for some of the specimens from the Lesser Antilles at 225 to 430 m. Thus, E. hillianus in the first volume is now recognized as E. robinsi.
New record: Oxynotus caribbaeus Cervigón, 1961
Espinosa Pérez and Huidobro-Campos (1995) listed this species from the southern Gulf of Mexico (22°32'N, 90°54'W) at 413 m. Previously it was known from Venezuela (Compagno 1984). This family keys to couplet 1b in the squaliform key (McEachran and Fechhelm 1998: 102). It is distinguished from Squalidae by possessing a very high and compressed body, with very high dorsal fins, rather than a low and cylindrical body and low dorsal fins as in Squalidae. Oxynotus caribbaeus is the only species of Oxynotidae in the western Atlantic (Compagno 1984).
New record: Mitsukurina owstoni Jordan, 1898
Glen Parsons et al. (2002) reported the capture of this species off Mississippi (28°44.62'N, 88°34.13'W) at 919 to 1,099 m. This species, the sole member of Mitsukurinidae, was previously known from the Pacific, Indian, and Atlantic Oceans, and in the Atlantic only off French Guiana. This family is distinguished from the other families of lamniform sharks by the following combination of characters: Snout is elongated and flattened into a daggerlike blade; precaudal pits are absent; and ventral caudal fin lobe is absent (Compagno 1984).
Incorrect record: Benthobatis marcida Bean and Weed, 1909
This species was incorrectly listed from the Gulf of Mexico. It has been recorded from the Straits of Florida but not the Gulf of Mexico (Marcelo de Carvalho, pers. comm., 1998).
Replacement name: Narcine bancrofti (Griffith, 1834)
McEachran and de Carvalho (2002) elevated this species from synonymy with N. brasiliensis for populations from North Carolina to the Gulf of Mexico, including the Greater and Lesser Antilles, between the shoreline and 37 m. Thus, Narcine bancrofti replaces N. brasiliensis in the first volume.
New record: Rhinoptera brasiliensis
Castro-Aguirre and Espinosa Pérez (1996) list this species from Tuxpan, Veracruz (20°58'25"N, 97°17'15"W). Previously it was known from the southern Caribbean off Colombia (McEachran and de Carvalho 2002). This species is distinguished from the other species in the Gulf of Mexico (R. bonasus) by the following combination of characters: Series of tooth plates in each jaw number 8 to 10 (usually 9), and median series of tooth plates is about 5 times as long as it is high (Bigelow and Schroeder 1953; McEachran and de Carvalho 2002).
New record: Acromycter perturbator (Parr, 1932)
Three lots of specimens of this species were discovered in the Texas Cooperative Wildlife Collection (TCWC) from the northern Gulf of Mexico off Louisiana and Florida between 896 and 1,170 m. Previously it was known from New Jersey, the Straits of Florida, the Bahamas, and Jamaica (Smith 1989). This species keys to couplet 13b of the congrid key (McEachran and Fechhelm 1998: 292). It is distinguished from Pseudophichthys splendens in that the posterior naris is opposite the upper margin of eye rather than at midlevel of eye (Smith 1989).
New record: Eurypharynx pelecanoides
A specimen of this species was discovered in the National Museum of Natural History (USNM) from Louisiana, 29°10'N, 87°57'W between 658 and 732 m, R/V Oregon, Station 3660. It is a cosmopolitan species and is distinguished from the other species in the Gulf of Mexico by the following combination of characters: Upper jaw is present; pharynx is highly distensible; gill opening is closer to anus than to tip of snout; and pectoral fin is minute (Böhlke 1966).
New record: Arius assimilis (Günther, 1864)
This species is reported from the southern Gulf of Mexico from Veracruz, Tabasco, and Campeche (Castro-Aguirre et al. 1999, as Ariopsis assimilis). It was previously known from Yucatán to Honduras along the coast and in estuaries, lagoons, and fresh waters (Taylor and Menezes 1978). It keys to couplet 2a of the ariid key (McEachran and Fechhelm 1998: 360) and is distinguished from A. felis by the following combination of characters: Longitudinal fleshy groove on top of head does not extend anteriorly to level of eyes; gill rakers on outer surface of first gill arch number 16 to 18; and gill rakers on outer surface of second gill arch number 18 to 22 (in A. felis, the longitudinal fleshy groove on top of head extends anteriorly to level of eyes; gill rakers on outer surface of first gill arch number 13 to 16; and gill rakers on outer surface of second arch number 13 to 17; Taylor and Menezes 1978).
New record: Cathorops aguadulce (Meek, 1904)
This species is recorded from Veracruz to Guatemala in estuaries, lagoons, and fresh waters by Castro-Aguirre et al. (1999) and replaces (in part) Cathorops sp. in McEachran and Fechhelm (1998: 363). It was previously known from Venezuela to Panama. It is distinguished from the other species of the genus in the Gulf of Mexico by the following combination of characters: Axillary pore is much smaller than nasal opening; internal surface of pectoral and pelvic fins is gray to grayish brown; first gill arch has 14 to 17 gill rakers; second gill arch has 14 to 19 gill rakers; and serrations on inner aspect of pectoral spine are straight and well developed (Castro-Aguirre et al. 1999).
New record: Cathorops melanopus (Günther, 1864)
This species is reported from Tamaulipas to Honduras in estuaries, lagoons, and fresh waters by Castro-Aguirre et al. (1999) and replaces (in part) Cathorops sp. in McEachran and Fechhelm (1998: 363). This species was previously known from Tamaulipas, Mexico, to Honduras. It is distinguished from the other species of the genus in the Gulf of Mexico by the following combination of characters: Axillary pore is as large as nasal opening, and internal surface of pectoral and pelvic fins is darkly pigmented (Castro-Aguirre et al. 1999).
New record: Cathorops spixi (Agassiz, 1829)
This species is reported from Tabasco, Campeche, and Yucatán in estuaries, lagoons, and fresh waters by Castro-Aguirre et al. (1999) and replaces (in part) Cathorops sp. in McEachran and Fechhelm (1998: 363). This species was previously known from the northern coast of South America from Colombia to Rio de Janeiro. It is distinguished from the other species of Cathorops by the following combination of characters: Axillary pore is much smaller than nasal opening; internal surface of pectoral and pelvic fins is gray to grayish brown; first gill arch has 18 to 22 gill rakers; second gill arch has 17 to 21 gill rakers; serrations on inner aspect of pectoral fin spine are weak and oblique (Castro-Aguirre et al. 1999).
New record: Alepocephalus australie Barnhard, 1923
Two lots of specimens of this species were discovered in the Texas Cooperative Wildlife Collection (TCWC) that were collected off Texas and Florida at depths from 752 to 936 m. Previously this species was known from the western Atlantic between 10° and 39° and the eastern Atlantic from South Africa to southeastern Ireland (Markle and Quéro 1984). It keys to couplet 10b in the alepocephalid key (McEachran and Fechhelm 1998: 382) and is distinguished from A. productus by the following combination of characters: Transverse scale rows from dorsal fin origin to first lateral line scale number fewer than 30, and posterior margin of eye is slightly nearer to tip of snout than to posterior margin of operculum (Markle and Quéro 1984).
New record: Eustomias achirus Parin and Pokhilskaya, 1974
Clarke (1998) recorded this species from four localities in the northern Gulf of Mexico: 27°00'N, 86°00'W; 29°14'N, 87°40'W; 29°00'N, 88°02'W; and 28°33'N, 88°48'W. It also occurs between 20°C and 40°C in the Atlantic and in the Coral Sea in the Pacific. It keys to couplet 33a in McEachran and Fechhelm (1998: 479) and is distinguished from E. lipochirus by the following combination of characters: Chin barbel is short, with three branches off stem that extend beyond tip of barbel and bear internal ovoid bodies; ovoid bodies are about the same diameter as stem and are spaced about three ovoid body diameters apart; branches are lightly pigmented or unpigmented between bodies (Clarke 1998).
Replacement name: Eustomias monoclonus Regan and Trewavas, 1930
Clarke (1999) reclassified E. dendriticus Regan and Trewavas, 1930, as E. monoclonus Regan and Trewavas, 1930, in the western Atlantic, including the Gulf of Mexico.
Replacement name: Aulopus filamentosus (Bloch, 1792)
According to B. A. Thompson, S. W. Ross, and K. Sulak (pers. comm., April 1998; in Smith-Vaniz et al. 1999), Aulopus filamentosus is the senior synonym of A. nanae.
Replacement name: Barathrites parri Nybelin, 1957
This species replaces Barathrites sp. in McEachran and Fechhelm (1998: 705). It is distinguished from the other species of the genus by the following combination of characters: Branchiostegal rays number seven, and basibranchial tooth plate is single. The other species, B. iris, has six branchiostegal rays and no basibranchial tooth plate (Nielsen et al. 1999).
New record: Bassozetus normalis Gill, 1884
J. G. Nielsen and N. G. Merritt (2000) record this species from throughout the Gulf of Mexico at depths from 1,775 to 3,843 m. It was previously known from the tropical Atlantic Ocean between 1,760 and 5,062 m (Nielsen and Merrett 2000). This species is distinguished from the other two congeners in the Gulf of Mexico by the following combination of characters: Long gill rakers on first arch number 13 to 20; scales in oblique row between dorsal fin origin and anus number 25 to 35; and body depth is 8.4% to 11% of SL. In B. compressus, long gill rakers on first arch number 11 to 14; scales in oblique row between dorsal fin origin and anus number 15 to 20; and body depth is 8% to 14% of SL. In B. robustus, long gill rakers on first arch number 13 to 16; scales in oblique row between dorsal fin origin and anus number 30 to 40; and body depth is 10% to 19% of SL (Nielsen and Merritt 2000).
Replacement name: Ophidion holbrooki (Putnam, 1874)
J. G. Nielsen et al. (1999) consider Ophidion beani a junior synonym of O. holbrooki.
New record: Ophidion josephi Girard, 1859
J. G. Nielson et al. (1999) consider this species valid but provide no characters to distinguish it from the other species of the genus. It occurs from Georgia to the northern Gulf of Mexico.
New record: Ophidion selenops Robins and Böhlke, 1959
J. G. Nielsen et al. (1999) list this species from South Carolina to the southeastern Gulf of Mexico. It is distinguished from the other species of Ophidion in the Gulf of Mexico by the following combination of characters: Tip of snout has prominent spine, and body is silvery.
New record: Bellottia apoda Giglioli, 1883
Several specimens of this species were captured in the northern Gulf of Mexico at 27°47'N, 91°30.5'W in 540 to 580 m and at 27°44.7'N, 91°13.3'W in 540 m. It was previously known from the tropical Atlantic and the Mediterranean Sea. This species keys to 3b of the bythitid key (McEachran and Fechhelm 1998: 742) and is distinguished from Cataetyx laticeps by lacking pelvic fins and possessing several sharp-pointed spines on the preoperculum (Cohen and Nielsen 1978).
New record: Caelorinchus ventilux Marshall and Iwamoto, 1973
A single specimen of this species was discovered in the Texas Cooperative Wildlife Collection (TCWC 4490.02) from Campeche Bay (21°07'30"N, 86°17'12"W, depth unknown). Previously it was known from the West Indies. This species is distinguished from the other species of Caelorinchus from the Gulf of Mexico by the following combination of characters: Ventral side of snout is scaled except for naked broad band anterior to premaxilla, and black band is present between dorsal fins. The other species either lack scales on ventral side of snout (C. occa) or have fully scaled ventral snouts, and lack black bands between dorsal fins (Marshall and Iwamoto 1973).
Replacement name: Laemonema goodebeanorum Meléndez and Markle, 1997
This species replaces Laemonema sp. in volume 1 (McEachran and Fechhelm 1998: 806). It occurs from Canada to Brazil, including the Gulf of Mexico, between 180 and 792 m.
New record: Batrachoides surinamensis (Bloch and Schneider, 1801)
Castro-Aguirre et al. (1999) report this species from Campeche to Brazil in coastal waters and estuaries. It is distinguished from the other batrachoidids in the Gulf of Mexico in possessing embedded scales; the other species are naked.
New record: Opsanus dichrostomus Collette, 2001
This species occurs in the southern Gulf of Mexico at Tampico, Veracruz, and along the west coast of the Yucatán Peninsula. It is also known from Cuba, the east coast of the Yucatán Peninsula, and Belize (Collette 2001). It is distinguished from the other batrachoidid species in the Gulf of Mexico by the following combination of characters: Second dorsal fin rays number 23 to 25; pectoral fin rays number 17 or 19; interorbital distance is less than orbit diameter (Collette 2001).
Incorrect record: Mugil gaimardianus Desmarest, 1831
This species is included in volume 1 but is a junior synonym of M. curema, according to Harrison (2002).
New record: Joturus pichardi Poey, 1860
This species occurs in the Gulf of Mexico, from the mouth of the Rio Grande to Yucatán, along the Caribbean coast of Central America and Colombia, and in the Bahamas and the Antilles. Adults inhabit freshwater streams but spawn in brackish water or the ocean (Harrison 2002). This species is distinguished from the other species of mugilids in the Gulf of Mexico in possessing a subterminal mouth (Harrison 2002).
New record: Cosmocampus brachycephalus (Poey, 1868)
This species is recorded from the eastern Gulf of Mexico at the Dry Tortugas. It ranges from the southern coast of Florida and the Bahamas to Venezuela, including the Greater and Lesser Antilles (Dawson 1982).
This species keys to couplet 16b in the syngnathid key (McEachran and Fechhelm 1998: 1049) and is distinguished from C. albirostris in having a snout length 26.3% to 34.5% of head length and a snout depth 45.5% to 71.4% of snout length rather than a snout length 35.7% to 45.5% of head length and a snout depth 25% to 38.5% of snout length as in C. albirostris.