Coryphopterus and Lythrypnus gobies of the Western Atlantic

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Introduction to Larval Gobies

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Western Atlantic Coryphopterus gobies

This large genus of gobies accounts for the vast majority of gobies one sees on and around Caribbean coral reefs. These fishes can be found perching on the bottom along the sandy edges of reefs, seemingly everywhere except in the most turbid or muddy environments. The genus contains numerous very similar-appearing species that can be a challenge to distinguish in the field. Those species that share meristics can be difficult, even when in hand or preserved in collections. The advent of DNA barcoding (identification with a standardized sequence of the COI gene of mtDNA) allows one to be certain of identifications and finally permits accurate diagnosis of indeterminate individuals. I have sequenced most of the species in the group as part of my larval identification studies with the Fish-Bol team at the Barcode of Life Project, with some surprising results (special thanks to Director Bob Hanner at the University of Guelph). On this webpage, I discuss the features useful for species IDs of adults, especially since most literature sources, including the keys of Bohlke and Chaplin and derivatives (and, especially, the line illustrations), depend on the wrong characters and are confusing or often plain incorrect.

Coryphopterus bol from Bonaire; pallid form, courtesy Brian Mayes

Coryphopterus

The gobies of Coryphopterus are particularly difficult to identify down to species. The sand-perching group, in particular, has been taxonomically troublesome as well, with some species boundaries still unclear. Using the characters I describe below, it is feasible (although not always simple) to identify preserved Coryphopterus specimens in collections where one can examine melanophore patterns closely. Live fishes, however, and especially photographs taken in the field, can sometimes be impossible to identify to species. It difficult to get pictures showing all of the diagnostic features for the species of fish, but the next generation of CCTV cameras working underwater should provide better resolution- especially continuous video monitoring with high quality closed circuit CCTV cameras.

Most of the sand gobies are distinguished only by combinations of characters, each of which by themselves is not sufficient and can occur in several of the species. As a result, any simple dichotomous key will be misleading, and would likely apply only to light or dark individuals, specific locations, and/or specific size classes. The results of my barcode mtDNA sequencing for this group show that the range of variation in morphology and markings within species is much greater than is described in the literature. In addition, a number of newly-recognized cryptic species are present within the region.

Cryptic species: A difficult problem when using the literature and field-guides for identifications is the presence of cryptic species (distinct genetic lineages with only subtle morphological differences) among the common 10/10 sand-perching bridled-goby group. These cryptic species appear very similar but can have remarkably divergent mtDNA sequences: I have found about 10% sequence divergence between some species (with little variation within species). My sequences are available on the public database of the Barcode of Life Project.

The traditional "bridled goby", C. glaucofraenum, splits up into a clade of five different species. Three of these species are abundant and widespread in the region and segregate by habitat, while two others, C. punctipectophorus and C. venezuelae, are more localized species at the temperate edges of the region. C. punctipectophorus is found in Florida and the Gulf of Mexico and C. venezuelae is restricted to NE Venezuela, an unusual region with many endemic goby and blennioid species.

The three widespread cryptic species of bridled goby comprise the originally described C. glaucofraenum, the "pallid" bridled goby C. tortugae, and the new species C. bol (Victor 2008). C. tortugae were originally described in 1902 and, as more data became available, recently twice redescribed more precisely (by Acero in 1990 and Victor 2008). C. bol is the more-offshore sibling species of C. tortugae and both have been lumped by most observers as variants of the bridled goby C. glaucofraenum. To avoid confusion, I propose that C. glaucofraenum retain the "inshore bridled goby" common name ("colon-tail goby" would be much more apt), while C. tortugae should be called the "patch-reef bridled goby" and C. bol should be called the "canyon bridled goby" after their distinctive habitats.

Markings: One of the primary causes of the difficulty in identifying Coryphopterus species in the western Atlantic is the extreme variability in the degree of their dark markings with habitat. All of the sand gobies have lightly marked forms on white sand in clear water and heavily marked forms on darker sediments in more turbid waters, particularly along continental coastlines. This variation can become extreme in several of the species, particularly C. tortugae, C. bol, C. eidolon, and C. thrix, with some individuals showing almost no markings at all. These occasional very pallid individuals can be impossible to identify to species without DNA sequencing. On the other hand, heavily marked populations of some typically pallid species, especially the "pallid goby" C. eidolon and C. tortugae, have not been recognized and are assigned to other species in museum collections.

The sand-goby clade share their basic marking patterns and differ mostly in the extent and orientation of the markings. Most marking differences are quite subtle and, unfortunately, overlap to some degree. Several sets of body markings diverge as juveniles develop and become diagnostic characters. The marking patterns of most utility are the spots, stripes, and bars on the top and sides of the head, around the eye, at the pectoral-fin base, and at the base of the caudal fin.

Live sand gobies have somewhat different markings from preserved fishes. The primary colors on living sand gobies are orange and iridescent blue/white. Black markings made up of melanophores are scattered over the body and typically outline and underlie the orange markings. The blue and white markings are rarely outlined or underlain by melanophores, with the notable exception of the white bridle stripe across the cheek which can have an underlying stripe of melanophores (probably accenting the reflectivity in live fishes). Upon preservation, the orange disappears rapidly. The blue and white markings fade to some degree, but can often be discerned in preserved fishes. Indeed, the white markings are still visible on the hundred-year-old holotype of C. tortugae. The dark markings, i.e. the melanophore patterns, are best preserved and most useful in the detailed descriptions discussed below.

Coryphopterus bol from Exuma, Bahamas; pallid form, courtesy Steve Roos

The process of identification is further complicated by a great deal of intraspecific variation in some markings, often in the very patterns that are typically used to identify species; for example, the characteristic round colon-like pectoral-fin base spots of the colon goby, C. dicrus, are often not round and often do not form the distinctive colon mark. Most markings and morphological characters that have been considered diagnostic for species in the literature are variably present, and can often be found on other species as well.

The sand gobies also show marked individual variation in morphology, with some specimens wider-bodied or with larger heads (note the paratypes of C. bol below). This variation interacts with marking variations; the diagnostic spots and stripes are variously moved and stretched with the shape changes, sometimes making a character no longer useful for distinguishing two species.

Fortunately, a few markings develop at transition and are, to coin a word, "taxognomonic", i.e. uniquely diagnostic- such as the mid-body bar and dorsal-fin base spot in C. alloides. Some are taxognomonic and appear early, for example the speckled upper eyeball in C. thrix. Nevertheless, most sand gobies are distinguished only by combinations of characters, each of which by themselves is not sufficient and can occur in a subset of species. This problem becomes acute for the bridled goby clade and several characters need to be examined closely to be certain of the species. Note, however, that this applies mostly to intermediate individuals- many specimens have unambiguous combinations of markings that can make identification straightforward. Unfortunately, some juveniles, most very pallid individuals, and some breeding males (often uniformly dusky), can be missing the diagnostic markings.

Fin-ray counts can be very useful in separating species of sand gobies and are much less variable than morphology or markings. However, many of the more difficult species share the 10/10 fin ray formula.

The reported fin-ray counts for the genus Coryphopterus in the literature:

format= Species: #dorsal/#anal-fin elements #pectoral rays (pelvic-fin state)

The Sand Gobies

10/10 group
(widespread and abundant species)

C. glaucofraenum: Randall: 10/10 pect 17-20 Bohlke: 10/10, rare 9 pect 17-20 usu 19

C. tortugae: Acero: 10/10 pect 18-20

C. bol: Victor 2008: 10/10 pect 18-20

C. eidolon: Randall: 10 (11 was a typo)/9-10, mode 10 pect 19-20, rare 18 Bohlke: 10/10, rare 9 pect 19-20

C. thrix: Bohlke: 9-10/10 pect 17-19

C. dicrus: Randall: 10/10 pect 18-20 Bohlke: 10/10 pect 18-20

11 group
(localized endemics)

C. punctipectophorus: Bohlke: 11/10 pect 18-20 (South Carolina to the Gulf of Mexico)

C. venezuelae: Cervigon: 11/11 pect 18-20 (NE Venezuela: limted to the Gulf of Cariaco (Cumana), Isla Cubagua, Isla Margarita, & the Mochima region)

fewer than 10

C. kuna: 9/9 pect 14-15 (widespread Caribbean and Florida)

C. alloides: 10/9 Bohlke: 10, rare 9/9 pect 16-17 (divided pelvic fins) widespread

The Reef Gobies

C. lipernes: 10/10 pect 16-18 (divided pelvic fins)

C. hyalinus: 10/10 pect 14-16 (divided pelvic fins)

C. personatus: Randall: 11/11 pect 14-16 (occ. 10/10) Bohlke: 10-11, mode 11/10-11, mode 11 pect 14-16 (divided pelvic fins)

Note: fin-ray counts for the second dorsal fin and the anal fin are total elements (spines plus rays)

Coryphopterus glaucofraenum

Diagnosis: Coryphopterus glaucofraenum, or the bridled goby, is one of several 10/10 sand gobies. Several other sand gobies have the same white under-eye bridle stripe, thus a more apt common name would be the colon-tail goby, the most obvious character of C. glaucofraenum (or perhaps the "inshore bridled goby"). This species is typically found in inshore habitats: it accounts for virtually all the sand gobies in silty mangrove or turbid-water shallows, many of the sand gobies in shallow bays with mixed reef/sand habitat, and only occasionally on offshore patch reefs or deeper habitats. Populations in mangrove areas and silty shallows are heavily-marked and relatively simple to identify, while those living in clear-water sandy bays and shallow patch reefs are lightly-marked and can be difficult to separate from other sand gobies.

The suite of characters that distinguish adult C. glaucofraenum comprise (in order of usefulness):

	two colon-like spots at the caudal-fin base, distinctly-rounded and mostly separate on lightly-marked fish, joined by a constricted bridge on darker fish, but with distinctly rounded end-spots -present at all sizes, darker fish can have extensive bridging	vs. most other sand gobies, which have a bar -except C. venezuelae which shares the colon-like spots and some light C. tortugae in which the bar breaks into two segments - some dark C. bol can have a thick dumbell bar -C. punctipectophorus have colon spots, but not conspicuous, same intensity as body spots
	two-pronged wide dark dorsal projection on the mid eye-stripe over the mid-opercle, prongs split around a white spot elevated above its row (bridging black is raised over stripe level), anterior prong lower than posterior -develops on mature adults; useful when present, smaller adults can have no projections	vs. C. tortugae, C. bol, and C. venezuelae, which have a simple triangle (they can have a very small anterior spike); white spot behind the triangle usually not much elevated- if the spot is bracketed by black, then anterior triangle larger than posterior -other sand gobies have no dark projections in that location
	the melanophore component of the orange lower eye-stripe continues as a straight dark stripe forward across the suborbital to the tip of the jaw; even light fish have a dark edge at the crossing of the suborbital at mid-maxilla- i.e. above the fleshy lip (premaxilla) and just above the white bridle and its melanophore stripe -on juveniles the stripe can be interrupted by the eyeball, on larger and lighter adults the dark-on-orange stripe curves down, but still above the white bridle	vs. C. tortugae and C. bol, with no dark stripe on the anterior orange segment of under-eye stripe: instead the dark stripe merges down to the white bridle and its melanophore stripe, leaving the 8 o'clock suborbital region unmarked; no dark edge at the crossing of the suborbital at mid-maxilla (behind the lip, at the end of the orange stripe); on light fish a simple patch or bar of melanophores under the eye at 6-7 o'clock -C. venezuelae shares the straight-line stripe
	no discrete outlined dark spot on the lower pectoral-fin base on pale fish (can be sparsely speckled); some dark fish can have a diffuse patch of melanophores (not sharply-outlined), sometimes trailing up to meet the upper fin base markings -small juveniles can have no marks or a cluster of 3-4 solitary central melanophores	vs. C. bol, C. dicrus, and C. venezuelae, which have a sharply-outlined dark spot, usually round or a long oval or an upward-facing crescent (however, small juveniles and pallid fish can have no marks or just a few central melanophores) -C. eidolon and C. thrix also have variable shading, speckling, and spots.
	upper eye-stripe complete or broken into segments, not round spots	vs. C. dicrus (and sometimes C. eidolon and C. thrix), which have rounded spots instead of an upper eye-stripe
	dorsal midline head spots with chain link loops	vs. C. tortugae and C. dicrus, which have no complete loops or rounded spots (respectively)
	pelvic fin fused, frenum well-developed	vs. C. alloides with divided pelvic fins and C. dicrus with no frenum
	innermost pelvic-fin rays usually about equal to next (many exceptions)	vs. C. dicrus, C. eidolon, C. alloides, many C. thrix, and occasional individuals of other sand gobies, which have shorter innermost rays

Coryphopterus glaucofraenum

colon spot tail, dark on orange anterior under-eye stripe (curves down on large fish), elevated second white spot on mid-eye stripe, no lower pectoral base spot

Florida,courtesy Paul Osmond

Coryphopterus glaucofraenum light

colon spot tail, dark on orange anterior under-eye stripe (curves down on large fish), no lower pectoral spot

Bermuda, courtesy George Lin

Dark form, inshore silty and mangrove habitat:

Coryphopterus glaucofraenum dark

11.5 mm SL, juvenile, 10/10

Mochima, Venezuela, GCRL 15947

Coryphopterus glaucofraenum dark

21.3 mm SL, 10/10

note under-eye stripe straight to tip

lower pectoral patch without sharp edges

Mochima, Venezuela, GCRL 15947

identification of coryphopterus glaucofraenum

Coryphopterus glaucofraenum dark

24.5 mm SL, DNA confirmed ID

note under-eye dark stripe across to tip

lower pectoral patch without sharp edges

Colon, Panama N7531a

Coryphopterus glaucofraenum dark

30.1 mm SL, female, DNA confirmed ID

note under-eye stripe curves down

no pectoral spot, two prong projection

Colon, Panama N7527b

Light form, shallow sandy bays and patch reefs:

Coryphopterus glaucofraenum light

13.1 mm SL, juvenile, DNA confirmed ID

lower eye-stripe and 8 o'clock spots

St. Thomas, USVI, ST307a

Coryphopterus glaucofraenum light

28.8 mm SL, DNA confirmed ID

note dark edge at crossing mid-maxilla

two pronged projection, no pectoral spot

upper eye-stripe variable, chain-link loops

St. Thomas, ST307

Coryphopterus glaucofraenum light

32.3 mm SL male, DNA confirmed ID

note dark edge at crossing mid-maxilla

two pronged projection, no pectoral spot

colon tail spots, notched pelvic fin

St. Thomas, ST307

Coryphopterus tortugae

Diagnosis: Coryphopterus tortugae, or the patch-reef goby, is one of several 10/10 sand gobies. This species is typically found in shallow patch reef environments: it accounts for most of the sand gobies on mid-shelf reefs and around patch reefs in clear water (less than 30 feet deep) and many of the sand gobies in shallow bays with mixed reef/sand habitat. Many populations are pallid, some with very few markings (these cannot always be easily separated from very pallid individuals of similar species, especially C. bol, C. thrix, and C. eidolon). There is no single diagnostic feature of C. tortugae: a combination of characters, and, in particular, the absence of diagnostic features of other species, is critical.

The suite of characters that distinguish adult C. tortugae comprise (in order of usefulness):

	simple triangular dark dorsal projection (point-up) on the mid eye-stripe over the mid-opercle (sometimes with a very small anterior spike); white spot behind the triangle usually not elevated; if the spot is followed by another dark triangle, anterior triangle larger than posterior -develops on large juveniles and adults	vs. C. glaucofraenum, which have a wide two-pronged dorsal projection split around a white spot elevated above its row (bridging black is raised over stripe level), anterior prong lower than posterior -other sand gobies have no such dark marks -C. bol and C. venezuelae share the triangles
	no dark lower pectoral-fin base markings; on some breeding adults there can be fine speckling continuous with thoracic speckling	vs. C. bol, C. dicrus, and C. venezuelae, which have a sharply-outlined dark spot; dark C. eidolon and C. alloides, which have a variable spot or stripe; and C. glaucofraenum, which have speckling or shading (note that pallid individuals of all species can have no markings)
	on lighter fish a simple patch or bar of melanophores under the eye at 6-7 o'clock; no dark stripe at the anterior orange segment of the under-eye stripe: instead the dark lower-eye stripe merges with the white bridle and its melanophore stripe, leaving the 8 o'clock suborbital region unmarked (dark fish can have a speckling in that region); no dark edge of the suborbital at mid-maxilla (behind the lip, at the end of the orange stripe, above the white bridle) -present at all sizes	vs. C. glaucofraenum and C. venezuelae, on which the melanophore component of the orange lower eye-stripe continues as a straight dark stripe forward across the suborbital to the tip of the jaw (even light fish have a dark edge of the suborbital at mid-maxilla, behind the lip, just above the white bridle and its melanophore stripe) -C. bol share the pattern; C. dicrus variable; C. eidolon and C. thrix have no under-eye stripe
	upper eye-stripe broken into linear segments, midline head spots discrete with no connecting chain-link loops -rare dark fish with complete upper eye-stripe, and incomplete chain links	vs. C. glaucofraenum and C. venezuelae, which have chain-link loops; C. bol, which have a both a complete upper eye-stripe and chain link loops; and C. dicrus (and sometimes C. eidolon and C. thrix) which have rows of rounded spots on top of the head
	basicaudal bar usually a simple bar, some light fish have the bar broken into two segments, often with bridging melanophores, not usually obviously rounded	vs. C. glaucofraenum and C. venezuelae, which have two rounded colon-like spots at the caudal-fin base, separate on light fish, joined by a constricted bridge on darker fish, but with distinctly rounded end-spots -other species share a variable bar
	innermost pelvic-fin rays usually about equal to next	vs. C. dicrus , C. alloides, and many C. thrix, as well as occasional individuals of other sand gobies, which have shorter innermost rays
	innermost pelvic-fin rays usually about equal to next	vs. C. dicrus, C. eidolon, C. alloides, many C. thrix, and occasional individuals of other sand gobies, which have shorter innermost rays

Coryphopterus tortugae

mid-eye stripe with dark triangle; no black on anterior orange segment of under-eye stripe; no lower pectoral-fin base spot; broken upper-eye stripe, no loops

belize, courtesy Paddy Ryan

Coryphopterus tortugae

basicaudal bar broken into two, but not rounded spots

Belize, courtesy Paddy Ryan

Coryphopterus tortugae

36.8 mm SL, DNA confirmed ID

La Parguera, Puerto Rico pr789

Coryphopterus tortugae

36.8 mm SL, DNA confirmed ID

no lower pectoral-fin base spot,
broken upper eye-stripe
no stripe to tip of jaw or 8 o'clock bar

La Parguera, Puerto Rico pr789

Coryphopterus tortugae

32.0 mm SL, DNA confirmed ID

most heavily-marked form, with:
no lower pectoral-fin base spot,
complete upper eye-stripe but no links,
no stripe to tip of jaw or 8 o'clock bar

La Parguera, Puerto Rico pr7811

Coryphopterus tortugae

27.0 mm SL, DNA confirmed ID

midline spots, no upper eye-stripe

La Parguera, Puerto Rico pr784b

Coryphopterus tortugae

28.5 mm SL, DNA confirmed ID

midline spots, broken upper eye-stripe

La Parguera, Puerto Rico pr784b

Coryphopterus tortugae

23.8 mm SL, DNA confirmed ID

midline spots, broken upper eye-stripe

La Parguera, Puerto Rico pr7811

Coryphopterus tortugae

25.1 mm SL, DNA confirmed ID

midline spots, broken upper eye-stripe

La Parguera, Puerto Rico pr7811

Coryphopterus tortugae dark

32.0 mm SL, DNA confirmed ID

midline spots, not clearly linked to
mostly complete upper eye-stripe

La Parguera, Puerto Rico pr7811

Ctenogobius transparentus holotype, 1958

synonym of Coryphopterus tortugae

triangle mark, no discrete pectoral spot

courtesy H. Zetzsche, Sencken. Museum

Coryphopterus tortugae holotype (1902)

triangle projection, broken upper eye-stripe

courtesy D. Catania and J. Fong, CAS

Coryphopterus bol

Diagnosis: Coryphopterus bol, or the sand-canyon goby, is one of several 10/10 sand gobies. This recently-described species is typically found on deeper offshore reefs: it accounts for most of the sand gobies in offshore buttress-canyon habitats and around rocky points with strong currents. It is the abundant sand goby found in sand channels around dropoffs on continental coastlines with strong currents. Many populations are pallid, some with very few markings (these cannot always be easily separated from very pallid individuals of similar species, especially C. tortugae, C. thrix, and C. eidolon).

The suite of characters that distinguish adult C. bol comprise (in order of usefulness):

	simple triangular dark dorsal projection (point-up) on the mid eye-stripe over the mid-opercle (sometimes with a very small anterior spike); white spot behind the triangle usually not elevated; if the spot is followed by another dark triangle, anterior triangle larger than posterior -develops on large juveniles and adults	vs. C. glaucofraenum, which have a wide two-pronged dorsal projection split around a white spot elevated above its row (bridging black is raised over stripe level), anterior prong lower than posterior -other sand gobies have no such dark marks -C. tortugae and C. venezuelae share the triangles
	on lighter fish a simple patch or bar of melanophores under the eye at 6-7 o'clock; no dark stripe at the anterior orange segment of the under-eye stripe: instead the dark lower-eye stripe merges with the white bridle and its melanophore stripe, leaving the 8 o'clock suborbital region unmarked (dark fish can have a speckling in that region); no dark edge of the suborbital at mid-maxilla (behind the lip, at the end of the orange stripe, above the white bridle) -present at all sizes	vs. C. glaucofraenum and C. venezuelae, on which the melanophore component of the orange lower eye-stripe continues as a straight dark stripe forward across the suborbital to the tip of the jaw (even light fish have a dark edge of the suborbital at mid-maxilla, behind the lip, just above the white bridle and its melanophore stripe) -C. tortugae share the pattern; C. dicrus variable -C. eidolon and C. thrix have no under-eye stripe
	sharply-outlined dark spot at the lower pectoral-fin base, usually a long upward-facing crescent or oval -can be absent on new recruits and very pallid individuals	vs. C. glaucofraenum, C. tortugae, and C. thrix, which are variously unmarked, have a broad stripe or unshaped speckling on the lower pectoral-fin base -C. venezuelae share the same-shaped spot, C. dicrus have a round or oval spot, dark C. eidolon have a variable spot, and C. alloides have a stripe
	complete upper eye-stripe with short and linear midline head spots (often bracketing the exact midline), some fish develop adjacent lyre-like curves, on dark fish they form loops of melanophores in a chain-link pattern -can be absent on light fish or broken on small juveniles	vs. C. tortugae, which have a broken upper eye-stripe with round midline head spots and no chain-link loops (partial on the darkest fish); and C. dicrus, which have rounded spots instead of an upper eye-stripe -C. glaucofraenum and C. venezuelae can share the pattern, C. eidolon and C. thrix are variable
	basicaudal bar usually a simple bar on lighter fish, some light fish have two segments with some bridging melanophores (not distinctly rounded); darker fish have a thick C-shape or a thick dumbell shape.	vs. C. glaucofraenum and C. venezuelae, which have two rounded colon-like spots at the caudal-fin base, separate on light fish, joined by a constricted bridge on darker fish, but with distinctly rounded end-spots -other species share a variable bar
	pelvic fin fused, frenum well-developed	vs. C. alloides with divided pelvic fins and C. dicrus with no frenum
	innermost pelvic-fin rays usually about equal to next	vs. C. dicrus, C. eidolon, C. alloides, many C. thrix, and occasional individuals of other sand gobies, which have shorter innermost rays

Coryphopterus bol

mid-eye stripe with dark triangle; no black on anterior orange segment of under-eye stripe; lower pectoral base spot sharply-outlined; complete upper-eye stripe

Bonaire, courtesy Les Wilk

Coryphopterus bol juvenile

22.5 mm SL, DNA confirmed ID

lower pectoral base spot, no 8 o'clock bar

or stripe, complete upper eye-stripe

Colon, Panama n7530a

Coryphopterus bol

holotype (top)

paratypes(three below)

Coryphopterus bol holotype

26.8 mm SL, DNA confirmed ID

pallid type: few head melanophores, but
spot developing at lower pectoral-fin base

La Parguera, Puerto Rico, pr785a

Coryphopterus bol

Exuma, Bahamas

courtesy Steve Roos

Coryphopterus bol paratype

32.1 mm SL, DNA confirmed ID

long-oval lower pectoral-fin base spot,
complete upper eye-stripe
no stripe to tip of jaw or 8 o'clock bar

La Parguera, Puerto Rico, pr7811

Coryphopterus bol paratype

28.0 mm SL, DNA confirmed ID

long oval pectoral base spot, triangle projection, complete upper eye-stripe
but under-eye stripe indeterminate

Colon, Panama N7530a

Coryphopterus bol paratype

24.5 mm SL, DNA confirmed ID

long oval pectoral base spot, triangle projection, complete upper eye-stripe,
under-eye stripe not straight to tip

St. Thomas, USVI ST80629

Coryphopterus bol?

definite bar at tail, not colon spots

Florida, photo by P. Leahy

Coryphopterus bol

with variant markings?

i.e. upper eye-stripe broken, under-eye stripe indeterminate, lower pectoral base dark spot not sharply outlined
but good triangle projection and tail bar, rules out C. glaucofraenum

Florida, photo by P. Leahy

Coryphopterus bol holotype

26.8 mm SL, DNA confirmed ID

upper eye-stripe developing,
while midline bare

La Parguera, Puerto Rico, pr785a

Coryphopterus bol paratype

24.5 mm SL, DNA confirmed ID

upper eye-stripe complete
midline with only short lines off-center

La Parguera, Puerto Rico, pr785

Coryphopterus bol paratype

23.7 mm SL, DNA confirmed ID

upper eye-stripe complete, fine
loops connecting midline off-center lines

La Parguera, Puerto Rico, pr785

Coryphopterus bol paratype

32.1 mm SL, DNA confirmed ID

upper eye-stripe mostly complete
loops forming chain links

La Parguera, Puerto Rico, pr789

Coryphopterus bol paratype

22.5 mm SL, DNA confirmed ID

upper eye-stripe complete
off-center lyre-like lines starting loops

Colon, Panama N7530a

Coryphopterus bol paratype

28.0 mm SL, DNA confirmed ID

upper eye-stripe complete, connecting
at ends with chain link pattern

Colon, Panama N7530a

Coryphopterus bol paratype

24.5 mm SL, DNA confirmed ID

upper eye-stripe complete
full chain link pattern

St. Thomas, USVI, 307

Coryphopterus dicrus

Diagnosis: Coryphopterus dicrus, or the colon goby, is one of several 10/10 sand gobies. This species is found in a variety of habitats, although rarely in inshore silty or mangrove sites.

Unfortunately, the diagnostic colon-like marks on the pectoral-fin base are often not present, and then the identification is based on a combination of features. The suite of characters that distinguish adult C. dicrus comprise (in order of usefulness):

	irregular rows of rounded spots (at the surface) instead of an upper eye-stripe, evenly distributed on the top of the head -on live fish there is usually a short subsurface upper eye-stripe (halfway back to the dorsal fin) -present on juveniles and adults	vs. C. glaucofraenum, C. tortugae, C. bol, and C. venezuelae, which have an upper eye-stripe (complete or segments) and chain-link loops -C. thrix and C. eidolon can sometimes also have the upper eye-stripe broken into rounded spots
	body freckled with numerous discrete small dark spots between larger spots and X-marks (sized from a tenth to a fifth of a pupil diameter) -present on juveniles and adults	vs. other sand gobies, with larger dark spots and X-marks, few intervening freckles -C. thrix and C. eidolon can have medium dark spots (from a fifth to a third of pupil diameter)
	sharply-outlined round or oval dark spot on the upper pectoral-fin base -only on some adults (then is diagnostic); but many have only a broad stripe	vs. all other sand gobies, which have a broad stripe on the upper base; C. thrix and C. eidolon often have a large uniform dark patch covering the upper pectoral-fin base
	sharply-outlined round or oval dark spot at the lower pectoral-fin base -on most adults	vs. most other sand gobies which are variously unmarked, have a broad stripe or unshaped speckling on the lower pectoral-fin base -C. punctipectophorus, C. venezuelae and C. bol also have an outlined spot, oval or round
	lower eye-stripe usually continues below the eye	vs. C. thrix and C. eidolon, in which the lower eye-stripe does not run under the eye
	lower cheek stripe extends straight across the cheek to the opercle, pointing towards the pectoral-fin base	vs. C. thrix and C. eidolon, which often have a short lower cheek stripe angled sharply-upward, pointing forward of the dorsal-fin origin
	pelvic fin fused, but frenum absent in adults	vs. all other sand gobies, which have an obvious frenum -except C. alloides with no pelvic frenum
	innermost pelvic-fin rays shorter than the next ray -develops after about 20 mm SL	-C. eidolon, C. alloides, many C. thrix, and occasional individuals of other sand gobies have shorter innermost rays
	no dark projection on the mid eye-stripe above the opercle (can have a small triangle just behind the eye, above the preopercle)	vs. C. glaucofraenum, C. tortugae, C. bol, and C. venezuelae, which have triangular or oblong dark dorsal projections on the mid eye-stripe (on larger juveniles and adults)

Coryphopterus dicrus

rounded spots over the top of the head

round spot only on lower pectoral-fin base

US Virgin Islands

courtesy Nathan Lovas, nathanlovas.com

Coryphopterus dicrus

Holbox, Yucatan (edge of Gulf of Mexico)

courtesy Hilario Itriago, letsseatv.com

Coryphopterus dicrus

20.0 mm SL, DNA confirmed ID

round spots on top and side of head

round colon-like spots on pectoral-fin base

St. Thomas, USVI, st307a

Coryphopterus eidolon

Diagnosis: Coryphopterus eidolon, or the pallid goby, is one of several 10/10 sand gobies. Its common name is a misnomer: there are heavily-marked populations of this species (usually misidentified in collections) and pallid versions of some other sand goby species, especially C. tortugae, C. bol, and C. thrix. A more apt common name would be the wall sand-goby, since this species has no unique morphological character, but is found mostly occupying deeper wall habitats. C. eidolon is typically found in sand channels draining through the dropoffs in deep clear water without strong currents. At most locations, specimens are pallid and have only orange markings in the place of dark markings, although often outlined in tiny melanophores. When preserved, these fishes can be almost completely white. Heavily-marked fish are characteristic of continental coastlines.

The suite of characters that distinguish adult C. eidolon comprise (in order of usefulness):

	discrete oblique line of melanophores from the orbital rim at 7-8 o'clock to the mid-maxilla on darker fish, not continuing onto the lip (premaxilla); just a few deeper melanophores on the most pallid fish -develops after transition, about 10 mm SL	vs. C. tortugae and C. bol (variable in C. dicrus), which have an unmarked area at 7-8 o'clock on the orbital rim; not a slanted line on C. glaucofraenum and C. venezuelae, on which it is part of the under-eye stripe -C. thrix have the same oblique line, but it continues onto the lip (premaxilla)
	lower eye-stripe (orange or black) not running below the eye level (can have a white bridle); mid eye-stripe with no dark dorsal projections, on pallid individuals only an orange stripe outlined with tiny melanophores; upper eye-stripe variable, can become a few rounded spots; no chain link loops connecting midline spots -eye-stripes develop on darker fish after about 15 mm SL	vs. most other sand gobies, on which the lower orange or black eye-stripe runs under the eye on adults (except C. thrix and C. alloides) vs. C. bol, C. tortugae, C. glaucofraenum and C. venezuelae, which have triangular or oblong dark dorsal projections on the mid eye-stripe -C. thrix share the pattern; C. dicrus have more rounded spots on the upper head
	stripe on the lower cheek from the corner of the jaw usually short and angled sharply-upward (pointing forward of the dorsal-fin origin) -angles upward on adults after about 20 mm SL	vs. most the other sand gobies, on which the stripe points toward the mid or upper pectoral-fin base, often long, extending across to the preopercle -some larger C. thrix have the same pattern
	variable spot at the lower pectoral-fin base (none on pallid fish), often a broad patch or stripe or oval -only on darker fish after about 25 mm SL	vs. dark C. tortugae, which have no markings at the lower pectoral-fin base -other sand gobies share a variable spot or markings on darker individuals
	a short extended second-dorsal-fin spine -develops uncommonly after about 18 mm SL	vs. C. thrix, which often have a much longer extension (many exceptions that overlap)
	few large round and comma-shaped black patches over the dorsal aspect of the eye (4-6) -from transition	vs. C. thrix, which have a speckling of mixed large and small irregular black spots (>10) over the dorsal aspect of the eye
	basicaudal bar short and simple	vs. C. glaucofraenum and C. venezuelae, which have two rounded colon-like spots
	innermost pelvic-fin rays often shorter than the next ray -develops after about 20 mm SL, highly variable	-C. dicrus, C. alloides, many C. thrix, and occasional individuals of other sand gobies share the short innermost rays
	pelvic fin fused, frenum well-developed	vs. C. alloides with divided pelvic fins and C. dicrus with no frenum

Coryphopterus eidolon juvenile, pallid

13.9 mm SL, DNA confirmed ID

head and basicaudal bar markings only

La Parguera, Puerto Rico, PR784a

Coryphopterus eidolon juvenile

14.0 mm SL, DNA confirmed ID

heavily-marked form

Colon, Panama, N7530b

Coryphopterus eidolon juvenile, pallid

13.9 mm SL, DNA confirmed ID

8 o'clock bar, no head stripes

La Parguera, Puerto Rico, PR784a

Coryphopterus eidolon juvenile

14.0 mm SL, DNA confirmed ID

heavily-marked form

Colon, Panama, N7530b

Coryphopterus eidolon juvenile, pallid

13.9 mm SL, DNA confirmed ID

evenly-sized head melanophores

La Parguera, Puerto Rico, PR784a

Coryphopterus eidolon juvenile

14.0 mm SL, DNA confirmed ID

heavily-marked form

Colon, Panama, N7530b

Coryphopterus eidolon super-pallid

36.5 mm SL, DNA confirmed ID

La Parguera, Puerto Rico, PR784a

Coryphopterus eidolon pallid

33.3 mm SL, male, DNA confirmed ID

no under-eye stripe, 8 o'clock oblique line

mid eye-stripe with thin outline

La Parguera, Puerto Rico PR784a

Coryphopterus eidolon dark

30.0 mm SL, male, DNA confirmed ID

no under-eye stripe, 8 o'clock oblique line

no dark projection on mid eye-stripe

Colon, Panama N7531a

Coryphopterus eidolon

33.5 mm SL, DNA confirmed ID

no under-eye stripe, 8 o'clock oblique line

no dark projection on mid eye-stripe

Colon, Panama N7530b

Coryphopterus thrix

Diagnosis: Coryphopterus thrix, or the inaptly-named bartail goby (most congeners share the bar on the tail), is one of several 10/10 sand gobies. A more helpful common name would be the speckled-eye goby, since this is often the only distinctive character of these gobies, especially on live fish. This species is typically found in offshore sand channels and around patch reefs near dropoffs in deep clear water. Most populations are pallid, some with very few markings (the speckled eye is then the only character separating them from very pallid individuals of similar species, especially C. tortugae, C. bol, and C. eidolon). Some C. thrix from continental coastlines can be heavily-marked.

The suite of characters that distinguish adult C. thrix comprise (in order of usefulness):

	speckling of mixed large and small black spots (>10) over the dorsal aspect of the eye, irregular, sometimes reticulated -develops after about 12 mm SL	vs. other sand gobies, which have a few large round and comma-shaped black patches over the dorsal aspect of the eye (5-8); very distinct on fish from deeper waters, obscured by shading in shallow areas
	discrete oblique line of melanophores from the orbital rim at 7-8 o'clock to the mid-premaxilla, i.e. continues onto the lip; on pallid fish the line is typically present, although sometimes deep and inconspicuous -develops after transition, about 10 mm SL	vs. C. tortugae and C. bol (variable in C. dicrus), which have an unmarked area at 7-8 o'clock on the orbital rim; line not discrete on C. glaucofraenum and C. venezuelae, on which it is part of the under-eye stripe -C. eidolon have the same oblique line, but it does not extend onto the lip (premaxilla)
	lower eye-stripe (orange or black) not running below the eye level; mid eye-stripe with no prominent dark dorsal projections; upper eye-stripe variable, can become spots; no chain link loops connecting midline spots -eye-stripes develop on darker fish after about 15 mm SL	vs. most other sand gobies, on which the lower eye-stripe runs under the eye on adults (except C. eidolon and C. alloides) vs. C. bol, C. tortugae, C. glaucofraenum and C. venezuelae, which have triangular or oblong dark dorsal projections on the mid eye-stripe -C. dicrus and sometimes C. eidolon also have rows of round spots behind the upper eye
	prominent black area uniformly covering upper third of the pectoral-fin base, sometimes present on pallid fish (not a stripe or central oval spot) -develops after about 18 mm SL, but variably present	vs. most other sand gobies, which have a short stripe across the upper pectoral-fin base; C. dicrus adults, which can have a central rounded sharply-outlined spot on the upper pectoral-fin base -dark C. eidolon can share a similar black area to lighter C. thrix
	extended second-dorsal-fin spine, usually back to the level of the mid or rear soft dorsal fin -develops after about 18 mm SL, but variably present; longest on adult males	vs. most other sand gobies, with no extension -short extension on some C. eidolon (often to the base of the fifth soft dorsal ray), can overlap in length with many C. thrix
	stripe on the lower cheek from the corner of the jaw usually short and angled sharply-upward (pointing forward of the dorsal-fin origin) -angles upward on adults after about 20 mm SL	vs. most the other sand gobies, on which the stripe points toward the mid or upper pectoral-fin base, often long, extending across to the preopercle -C. eidolon and some light C. tortugae have the same pattern
	basicaudal bar short and simple	vs. C. glaucofraenum and C. venezuelae, which have two rounded colon-like spots
	innermost pelvic-fin rays often shorter than the next ray -develops after about 20 mm SL	-C. dicrus , C. alloides, C. eidolon, and occasional individuals of other sand gobies share the short innermost rays
	pelvic fin fused, frenum well-developed	vs. C. alloides with divided pelvic fins and C. dicrus with no frenum

Coryphopterus thrix

speckled upper eye, extended second dorsal spine, pectoral-fin base spot,
8 o'clock bar from eye

Florida, photo by pipehorse

Coryphopterus thrix

speckled upper eye,
note isopod parasite on the head

photo courtesy Paul Osmond

Coryphopterus thrix juvenile, pallid

14.1 mm SL, DNA confirmed ID

speckled upper eye, extended second dorsal spine, variably-sized head spots

La Parguera, Puerto Rico, PR784a

Coryphopterus thrix pallid

22.8 mm SL, DNA confirmed ID

speckled upper eye, extended second dorsal spine, upper pectoral base spot

La Parguera, Puerto Rico, PR785a

Coryphopterus thrix, male, dark

27.0 mm SL, DNA confirmed ID

speckled upper eye, extended second dorsal spine, upper pectoral base spot

Colon, Panama n7531a

Coryphopterus punctipectophorus

Diagnosis: Coryphopterus punctipectophorus, or the spotted goby, is distinctive among the sand gobies for having 11 second-dorsal-fin elements and 10 anal-fin elements. This temperate species is found along the cooler northern and central coasts of Florida and in the Gulf of Mexico, usually in deeper waters. The suite of characters (in addition to the unique fin-ray count) that distinguish adult C. punctipectophorus comprise (in order of usefulness):

a sharply-delineated round or oval dark spot on the lower pectoral-fin base
no dorsal projection on the mid eye-stripe
large round colon spots on the base of the tail, not conspicuous
a long dark streak along the midline of the head behind the eyes
often an 8:30 o'clock dark line from the eye to the maxilla (under the white)
mostly complete upper eye-stripe and top of the head with a chain-link pattern
fused pelvic fin with a frenum, innermost rays about equal to next ray

Coryphopterus punctipectophorus

Destin, Florida (panhandle)

photo courtesy James Garin

Coryphopterus venezuelae

Diagnosis: Coryphopterus venezuelae, or the Venezuelan sand goby, is distinctive among the sand gobies for having 11 second-dorsal-fin and anal-fin elements. Although there is some variation, over 90% of specimens I have examined have 11/11, a count that has not been recorded for either C. bol (to which it is closely related) or C. glaucofraenum (which it closely resembles). It is found only in the NE part of Venezuela, around the Gulf of Cariaco and the offshore islands of Cubagua and Margarita, an area known for unusual water conditions and a number of endemic species. In that region, C. venezuelae is found in a variety of habitats, including shallow inshore and mangrove habitats, where it replaces the widespread Caribbean inshore bridled goby C. glaucofraenum. Around the periphery of its endemic zone, for example at Mochima, to the south of Cumana, both C. venezuelae and C. glaucofraenum are found in collections (e.g. GCRL 15947). After separation by dorsal fin counts, differing marking patterns are quite evident.

Note: Recruits and juveniles are only slightly different from C. glaucofraenum. The earliest difference is in the length of the melanophore row underlying the base of the first few anal-fin rays: it extends over 5 or 6 rays in C. venezuelae and about 3 in C. glaucofraenum (this difference is visible on fishes from transition up to about 30 mm SL). Starting around 12-15 mm SL, C. venezuelae develop an oval lower pectoral-fin base spot, becoming a sharply-outlined dark long oval at larger sizes. On C. glaucofraenum, there is either no spot, a group of 3-5 single melanophores, or, at most a speckling of melanophores in an amorphous cluster, often extending up to meet the upper pectoral-fin base markings. Interestingly, the first 3-5 central melanophores often remain the darkest in the center of the amorphous cluster. At all sizes, the colon spots at the caudal-fin base in C. glaucofraenum are more rounded and more isolated than in C. venezuelae, although the differences are not sufficiently reliable to separate all individuals. In the direct comparison of fish from the same collection, C. glaucofraenum have additional rows of small markings below the lower-body row of X-markings, while on C. venezuelae that area above the anal-fin base is mostly unmarked. Given the variation in the intensity of markings in sand gobies, it is unlikely that this will prove to be a consistent character across habitats.

Other than the diagnostic D-VI,11 A-11 and being present only in NE Venezuela, the suite of characters that distinguish adult C. venezuelae comprise (in order of usefulness):

	two colon-like spots at the caudal-fin base, joined by a constricted bridge, but with distinctly rounded end-spots -present at all sizes, darker fish can have extensive bridging	vs. most other sand gobies, which have a bar -except C. glaucofraenum, which shares the colon-like spots and some light C. tortugae and C. bol, which can have a dumbell bar of two spots with bridging melanophores
	simple triangular dark dorsal projection (point-up) on the mid eye-stripe over the mid-opercle (sometimes with a very small anterior spike); white spot behind the triangle usually not elevated; if the spot is followed by another dark triangle, anterior triangle darker and/or larger than posterior -develops on large juveniles and adults	vs. C. glaucofraenum, which develop a wide two-pronged dorsal projection split around a white spot elevated above its row (bridging black is raised over stripe level), anterior prong lower than posterior -C. tortugae and C. bol share the triangles -other sand gobies have no such dark triangles
	the melanophore component of the orange lower eye-stripe continues as a straight dark stripe forward across the suborbital to the tip of the jaw; even light fish have a dark edge at the crossing of the suborbital at mid-maxilla- i.e. above the fleshy lip (premaxilla) and just above the white bridle and its melanophore stripe -on juveniles the stripe can be interrupted by the eyeball, on larger and lighter adults the dark-on-orange stripe curves down, but still above the white bridle	vs. C. tortugae and C. bol, with no dark stripe on the anterior orange segment of under-eye stripe: instead the dark stripe merges down to the white bridle and its melanophore stripe, leaving the 8 o'clock suborbital region unmarked; no dark edge at the crossing of the suborbital at mid-maxilla (behind the lip, at the end of the orange stripe); on light fish a simple patch or bar of melanophores under the eye at 6-7 o'clock -C. glaucofraenum shares the straight-line stripe
	sharply-outlined black spot at the lower pectoral-fin base, usually a long upward-facing crescent or oval -can be absent on new recruits and very pallid individuals	vs. C. glaucofraenum, C. tortugae, and C. thrix, which are variously unmarked, have a broad stripe or unshaped speckling on the lower pectoral-fin base -C. bol share the same-shaped spot, C. dicrus have a round or oval spot, dark C. eidolon have a variable spot, and C. alloides have a stripe
	upper eye-stripe usually complete, not round spots	vs. C. dicrus (and sometimes C. eidolon and C. thrix), which have rounded spots instead of an upper eye-stripe
	dorsal midline head spots with chain link loops	vs. C. tortugae and C. dicrus, which have no complete loops or rounded spots (respectively)
	pelvic fin fused, frenum well-developed	vs. C. dicrus with no frenum and C. alloides with divided pelvic fins
	innermost pelvic-fin rays usually about equal to next (many exceptions)	vs. C. eidolon, C. dicrus, and C. alloides which have consistently shorter innermost rays

Coryphopterus venezuelae recruit

11.6 mm SL, 11/11

Mochima, Venezuela, GCRL 15947

vs. Coryphopterus glaucofraenum recruit

11.5 mm SL, 10/10

Mochima, Venezuela, GCRL 15947

Coryphopterus venezuelae recruit

11.6 mm SL, 11/11

Mochima, Venezuela, GCRL 15947

Coryphopterus glaucofraenum juvenile

vs. Coryphopterus venezuelae juvenile

14.0 mm SL, 10/10, above

14.9 mm SL, 11/11, below

Mochima, Venezuela, GCRL 15947

vs. Coryphopterus bol paratype

24.5 mm SL, DNA confirmed ID, 10/10

note under-eye stripe not straight to tip

St. Thomas, USVI ST80629

Coryphopterus venezuelae

22.8 mm SL, 11/11

note under-eye stripe straight to tip

lower pectoral spot oval with sharp edges

Mochima, Venezuela, GCRL 15947

vs. Coryphopterus glaucofraenum

21.3 mm SL, 10/10

note under-eye stripe straight to tip

lower pectoral spot without sharp edges

Mochima, Venezuela, GCRL 15947

Coryphopterus venezuelae (above)
Coryphopterus glaucofraenum (below)

Coryphopterus kuna

Diagnosis: Coryphopterus kuna, or the kuna goby, is distinctive among the sand gobies for having only 9 second dorsal and anal-fin elements. This recently-described species is found widely in the tropical Western Atlantic: so far sighted in Florida, Yucatan (Xcalak and Banco Chinchorro), Belize, Honduras (Utila), Panama, San Andres, Dominica, and Guadeloupe. It lives on sand and fine-gravel substrates, usually in deeper water and sandy slopes, and often among more numerous bridled gobies and Ctenogobius spp.. Adult C. kuna are tiny, less than an inch long, and distinguished from other sand gobies by the absence of head stripes and the presence of two rows of small but distinct black spots over the upper aspect of the eyeball, with 4-6 on the outer row and 2 on the inner. The spots can be particularly prominent on live fish. The species is notable for being very short-lived; in fact, the pelagic larval duration (about 2 months) is typically longer than the post-settlement life span.

Coryphopterus kuna adult female

10.9 mm SL

Utila, Honduras

Coryphopterus kuna adult male

13.3 mm SL

Utila, Honduras

Coryphopterus kuna adult male

15.2 mm SL

Utila, Honduras

Coryphopterus kuna adult male, holotype

17.6 mm SL

San Blas, Panama, SB82-098

Coryphopterus kuna

Palm Beach, Florida

courtesy Suzan Meldonian

Coryphopterus alloides

Diagnosis: Coryphopterus alloides, or the barfin goby, is distinctive among the sand gobies for having mostly divided pelvic fins, 10 second-dorsal-fin elements and only 9 anal-fin elements. The barfin appellation refers to the internal dark bar at midbody, visible in living fish, that extends to the base of the spinous dorsal fin. The suite of characters that distinguish adult C. alloides comprise (in order of usefulness):

internal dark bar in live fish
dark spot at the base of the second dorsal spine membrane
mostly-divided pelvic fins
D-VI,10 A-9

Juveniles develop the internal mid-body bar and dorsal-fin spot at transition. The divided pelvic fins do not develop until after about 12 mm SL.

Coryphopterus

7.7 mm SL

spe

San Blas, Panama, SB86-825

Coryphopterus lipernes

Diagnosis: Coryphopterus lipernes, or the peppermint goby, is a colorful coral-perching goby found throughout the region. Adults of the three non-sand Coryphopterus gobies have divided pelvic fins and a characteristic black patch at the vent. C. lipernes is distinguished by iridescent blue and yellow stripes, most obvious behind the mid eye. In addition, the scales on the upper body are typically outlined in a cross-hatch pattern.

Juveniles develop the characteristic light and dark stripe behind the mid eye (yellow and blue, respectively, in life) by 10 mm SL, about the same time that the dark ring around the vent expands (it is not well-developed on new recruits). The pelvic fins are fused in small juveniles and divide only after about 12 mm SL.

Coryphopterus lipernes juvenile

12.2 mm SL

mid eye-stripe

St. Thomas, USVI, ST806

Coryphopterus lipernes (below) juvenile

Coryphopterus hyalinus (above) juvenile

12.2 mm SL

mid eye-stripe

St. Thomas, USVI, ST806

Coryphopterus personatus

Diagnosis: Coryphopterus personatus, or the masked goby, is a colorful hovering goby found throughout the region. Adults of the three non-sand Coryphopterus gobies have divided pelvic fins and a characteristic black patch at the vent. C. personatus is very common in shallow-water where it hovers over coral heads in large groups, while C. hyalinus takes its place on coral walls and in deeper water. The two species can look quite similar underwater. On close examination, C. personatus has a single midline anterior dorsal interorbital pore, while C. hyalinus has a pair of pores side-by-side. In addition, C. personatus adults (over 12 mm SL; it is not true for juveniles) can be distinguished by an unmarked central patch on top of the head vs. a mostly uniform scattering of melanophores on adult C. hyalinus and the obvious stripe behind the mid eye in adult C. lipernes.

Juveniles develop the single interorbital pore by about 10 mm SL. The pelvic fins are fused in small juveniles and divide only after about 12 mm SL. The location of the vent within the black spot is an unreliable character on juveniles and small adults.

Coryphopterus personatus juvenile

12.4 mm SL

San Blas, Panama, SB82-086

C. personatus transitional recruit

10.0 mm SL, DNA confirmed ID

single anterior interorbital pore

St. Thomas, USVI, ST-506

Coryphopterus hyalinus

Diagnosis: Coryphopterus hyalinus, or the glass goby, is a colorful hovering goby found throughout the region. Adults of the three non-sand Coryphopterus gobies have divided pelvic fins and a characteristic black patch at the vent. C. hyalinus is quite similar to C. personatus and has the same habits, but is found on coral-reef walls and in deeper water. It has a pair of anterior dorsal interorbital pores side-by-side, while C. personatus and C. lipernes have a single midline anterior pore. In addition, C. hyalinus adults have a mostly uniform scattering of melanophores on top of the head and a dark line along the posterior lateral midline vs. an unmarked central region on top of the head in C. personatus and an obvious stripe behind the eye in C. lipernes (and no obvious line at the lateral midline of the body).

Juveniles develop the paired interorbital pores by about 10 mm SL. The pelvic fins are fused in small juveniles and divide only after about 12 mm SL. The location of the vent within the black spot is unreliable on small juveniles.

Coryphopterus hyalinus juvenile

12.2 mm SL

side-by-side interorbital pores

Utila, Honduras, U8703