Parioglossus Regan
Creators: name: Rui Wang
name: Richard Winterbottom
Publisher: name: Zenodo
Year: 2006
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Perciformes
Microdesmidae
Parioglossus

description: [[Genus Parioglossus Regan]]  
Variation of Osteology and General Morphology Between Species  
The vertebral count of the genus: All species in the genus have 10+16 vertebrae with rare exceptions (e.g. Kim and Han, 1993, Table 1). According to the original description, males of P. neocaledonicus had 10+15 vertebrae versus 11+14 in females (although one female was reported with a vertebral count of 11+15). The vertebral count was used to distinguish P. neocaledonicus from other species in the genus, especially P. verticalis (which also has 13 vertical bars on the body - Dingerkus and Séret, 1992; Suzuki et al., 1994). However, it appears that, for males, the variation arises from different counting methods (Séret, per. comm.) since the compound ural centrum was excluded from the count by those authors. If true, then females should have a vertebral count of 11+15 (= 26) and males have 11+16 (= 27). Radiographs of the specimens available to us (4 adults, 3 males and 1 female) show that both females and males have 10+16 vertebrae, although the number of vertebrae in females needs further confirmation.   
Character List and Evolution  
The characters listed below correspond to the numbering in the data matrix (Appendix 2). For each character, the plesiomorphic and apomorphic state or states are described, and the consistency index (CI), retention index (RI) and rescaled consistency index (RC) (Farris, 1989a, 1989b) generated by PAUP* (Swofford, 2001) are included. MacClade 4.03 (Maddison and Maddison, 2001) was used to assemble the data matrix and to visualize character change on the cladograms through optimization on the strict consensus tree (Fig. 11). Since there is no reliable evidence available to permit the ordering of multistate characters, all such characters (characters 1, 2, 4, 5, 9, 14, 16 and 17) were run unordered to avoid imposing unjustified models of evolution on them. For the same reason, all characters are equally weighted (but see Farris, 1969). For species in which individual variability encompasses more than one of the character states utilized here, the any instance coding protocol of Campbell and Frost (1993) is used.  
(1). Number of branched caudal fin rays: (0) - branched caudal fin rays 7+6; (1) - branched caudal fin rays 6+6; (2) - branched caudal fin rays 6+5. Nemateleotris magnifica has 6+6 branched caudal fin rays; P. nudus and P. philippinus have 6+5 such rays; the character state was ambiguous for P. dotui, P. interruptus and P. neocaledonicus as they have 6-7+6 branched caudal fin rays; based on any instance coding, they were assigned state 1. All other taxa have state 0. Character state 2 evolved once for the ancestor of P. philippinus and P. nudus; character state 1 evolved twice for the ingroup: once for P. interruptus and once for P. dotui and P. neocaledonicus; and once independently for Nemateleotris magnifica. CI=0.50; RI=0.50; RC=0.25. Note, however, that an assignment of character state 0 to P. dotui, P. interruptus and P. neocaledonicus would result in congruence with the strict consensus tree.  
(2). Scales: (0) - All or most scales imbricate (overlapping each other); (1) - scales all non-imbricate; (2) - no scales. All species except Parioglossus nudus have scales; Nemateleotris magnifica, Ptereleotris microlepis, Parioglossus interruptus, P. palustris, P. taeniatus, and P. verticalis have imbricate scales, conditions for Ptereleotris hanae, Parioglossus marginalis, P. rainfordi, P. raoi and P. triquetrus are ambiguous, they may have both non-imbricated scales and imbricated scales in any given specimen. Based on any instance coding, they were assigned state 1. The remaining species of Parioglossus have non-imbricate scales. Character state 1 evolved once for the ingroup taxa and once independently for Ptereleotris hanae; there is one reversal to imbricated scales in the ancestor of Parioglossus palustris, which then evolved to state 1 after the ancestor of P. taeniatus had seperated. CI=0.40; RI=0.40; RC=0.16.  
(3). Gill opening: (0) - moderate; (1) - narrow. A moderate gill opening, extending anteroventrally in front of the posterior limit of the branchiostegal membrane, appears to be the plesiomorphic character state. All outgroup taxa as well as P. aporos, P. dotui, P. galzini, P. marginalis, P. neocaledonicus, P. triquetrus and P. verticalis have a moderate gill opening. The other ingroup taxa have a narrow gill opening (extending anteroventrally to below the posteriormost tip of the branchiostegal membrane). It appears that character state 1 evolved twice in this group, once for P. lineatus and once after the ancestor of P. aporos separated. CI=0.50; RI=0.89; RC=0.44.  
(4). Number of circumorbital pores (terminology follows Rennis and Hoese, 1985): (0) - 3 circumorbital pores (no posterior nasal or anterior interorbital pores); (1) - 4 circumorbital pores (no posterior nasal pore); (2) - 5 circumorbital pores; (3) - no circumorbital pore. Ptereleotris hanae and P. microlepis have three circumorbital pores, Nemateleotris magnifica, Parioglossus interruptus, P. sinensis, and P. taeniatus have four circumorbital pores; P. raoi adults have none to four circumorbital pores (varies intraspecifically and apparently both ontogenetically and geographically; none in very small (ca. 11 mm SL), two pores only in some individuals, and not found elsewhere in the ingroup or outgroup - this state not coded; see Rennis and Hoese, 1985, Table 2 for details); P. aporos and P. nudus do not have any circumorbital pores. All other species of Parioglossus have five circumorbital pores. It seems that from optimization that P. aporos and P. nudus lost head pores independently. Character state 2 evolved only once for the ingroup, and is a potential synapomorphy for Parioglossus; character state 1 evolved once in the ancestor of P. interruptus and then reversed to state 2 for P. formosus. Head pores usually exhibit a constant pattern within a species, and are used as an important character to distinguish species in other gobioids (Miller, 1973). However, as shown above, in P. raoi the head pore pattern is highly variable. Individuals ascribed to this species exhibiting a variable number of pores have been taken in a single collection (consisting of 105 specimens). They are identical in all character states except the pattern of head pores (see also character 5), and they have therefore considered to be the same species (Rennis and Hoese, 1985). CI=0.50; RI=0.50; RC=0.25.  
(5). Number of preopercular pores: (0) - 3 preopercular pores; (1) - 2 preopercular pores; (2) - no preopercular pores. All outgroup taxa have 3 preopercular pores, and since this state does not occur in the ingroup, polarization is a posteriori. Parioglossus formosus, P. interruptus, P. palustris, P. rainfordi and P. taeniatus have 2 preopercular pores; the character state for P. raoi is ambiguous as it may have no or 2 preopercular pores (see Rennis and Hoese, 1985, Table 2; coded as 2 based on any instance coding); other ingroup taxa have no preopercular pores. When optimized on the cladogram, it seems that character state 2 evolved twice in the ingroup taxa (once in the ancestor of the ingroup, another time in P. sinensis and P. raoi clad), with character state 1 evolved once after the ancestor of (P. nudus, P. philippinus) separated. Two or fewer preopercular pores is a potential character supporting the monophyly of Parioglossus. CI=0.67; RI=0.83; RC=0.56.  
(6). Rostral cartilage ossification: (0) - rostral cartilaginous; (1) - rostral cartilage replaced, at least in part, by bone. Outgroup taxa and Parioglossus dotui, P. lineatus, P. marginalis, P. neocaledonicus, P. philippinus, P. sinensis and P. triquetrus possess a cartilaginous rostral. The character state for P. verticalis is unknown (based on the optimization, it probably has a cartilaginous rostral); other ingroup taxa have the rostral partially ossified. Character state 1 evolved once for the ingroup before the ancestor of P. galzini had separated, and reversed to a cartilaginous rostral in P. sinensis and P. philippinus independently. CI=0.33; RI=0.75; RC=0.25.  
(7). Ventral postcleithrum: (0) - ventral postcleithrum present; (1) - ventral postcleithrum absent. A ventral postcleithrum is absent in P. dotui, P. lineatus, P. marginalis, P. neocaledonicus, P. nudus and P. triquestrus; the state for this character is unknown for P. galzini and P. verticalis. Based on the optimization, P. verticalis probably does not have a ventral postcleithrum (state 1) while the character state of P. galzini is difficult to ascertain (information was only available from radiographs). Character state 1 evolved twice independently in the ingroup: once in the ancestor of the unresolved clade Parioglossus triquetrus to P. dotui (Fig. 11) and once for the ancestor of P. nudus. CI=0.50; RI=0.80; RC=0.40.  
(8). Surrounding anus in females: (0) - anal region pale; (1) - a dark ring around the anus. Parioglossus dotui, P. marginalis and P. neocaledonicus have a dark ring around the anus of females. It seems that character state 1 evolved once for the ingroup taxa and is a synapomorphy that supports the grouping of Parioglossus dotui and P. neocaledonicus in the consensus tree. The presence of the derived state of this character in P. marginalis suggests that it forms the sister group of these two species, as was found in three of the five equally most parsimonious trees, but this relationship collapsed into the polytomy in the consensus tree. Character state for P. verticalis is unknown. CI=1; RI=1; RC=1 if one assumes that P. marginalis forms a clade with P. dotui and P. neocaledonicus.  
(9). Number of gill rakers on ceratobranchial 1 and epibranchial 1: (0) - the number of gill rakers more than 21; (1) - gill rakers range from 15 to 20; (2) - gill rakers range from 12 to 15 (15 gill rakers could be coded as 1 or 2, depending on those numbers of other specimens of the species). Outgroup taxa have more gill rakers than ingroup taxa, with more than 21 gill rakers (no species has 21 gill rakers); Parioglossus nudus and P. aporos have 12-15 gill rakers; other ingroup taxa have 15-20 gill rakers. Since the outgroup does not share any of the states found in the ingroup, evidence for phylogenetic reconstruction based on this character is a posteriori. Optimization of this character suggests that character state 2 may have evolved twice independently (in P. aporos and P. nudus). Character state 1 is optimized as a potential autapomorphy for Parioglossus. CI=0.67; RI=0.67; RC=0.44.  
(10). Ossification of pelvis: (0) - bone; (1) - cartilage. Parioglossus dotui, P. interruptus, P. neocaledonicus, P. nudus, P. philippinus and P. sinensis have a cartilaginous pelvis (condition for P. verticalis is unknown). In all the outgroup taxa and the other ingroup taxa it is ossified. The condition here (and for characters 19-22) for P. galzini is inferred from the apparent density of these structures in the radiographs. Optimization of this character suggests that character state 1 evolved four times for the ingroup taxa: P. interruptus, P. sinensis, the ancestor of P. philippinus and P. nudus, and the ancestor of P. dotui and P. neocaledonicus. 0=0.25; RI=0.40; RC=0.10.  
(11). Shape of anterior nasal opening: (0) - short tube; (1) - simple pore. The anterior nasal opening of Parioglossus aporos, P. galzini, P. lineatus, P. nudus, P. philippinus, P. rainfordi, P. triquetrus, and P. verticalis is a simple pore whereas all outgroup taxa and the other ingroup taxa have a tubular anterior nasal opening. 0=0.50; RI=0.86; RC=0.43.  
(12). Shape of procurrent cartilage: (0) - cylindrical; (1) - more or less irregular in shape (Fig. 11). Nemateleotris magnifica, Ptereleotris hanae, Parioglossus aporos, P. nudus, P. philippinus and P. triquetrus have a cylindrical procurrent cartilage (condition for P. galzini and P. verticalis is unknown, based on the optimization, P. galzini probably has the character state 0). The remaining ingroup taxa and Ptereleotris microlepis have an irregular procurrent cartilage. Character state 1 evolved once in Ptereleotris microlepis and once for the P. rainfordi group. This state is also present in all the species represented in the unresolved basal polytomy except P. triquetrus and possibly P. verticalis (in which the state is equivocal). CI=0.33; RI=0.60; RC=0.20.  
(13). Presence of lateral stripe: (0) - no lateral stripe; (1) - distinct lateral stripe present (Fig. 1). Parioglossus formosus, P. interruptus, P. lineatus, P. neocaledonicus, P. raoi, P. sinensis and P. taeniatus posses a distinct lateral stripe. The outgroup taxa and other ingroup taxa do not have such a stripe as adults, and only in a few species as juveniles. Character state 1 evolved three times independently among members of the ingroup: once for the ancestor of P. interruptus group; once for P. neocaledonicus (DELTRAN) and once for P. lineatus. CI=0.33; RI=0.67; RC=0.22.  
(14). Presence of black spot or stripe on caudal fin: (0) - no black spot or stripe on the caudal fin; (1) - black stripe on caudal fin (Fig. 1); (2) - a black spot on caudal fin. The outgroup taxa and P. nudus lack a black spot on caudal fin; P. aporos, P. dotui, P. formosus, P. raoi, P. sinensis, P. taeniatus and P. verticalis have a black stripe on the caudal fin, while in other ingroup taxa a black spot is present. The condition for P. marginalis is coded as “1", although the stripe in females is broken up into a series of dark spots in a longitudinal row. Character state 1 evolved three times among the ingroup taxa: once each in P. verticalis, P. dotui (DELTRAN), P. aporos and the ancestor of the P. taeniatus group. Character state 2 evolved once among the ingroup taxa, however, based on the information currently available, it is hard to tell when character state 2 evolved, and further outgroups together with phylogenies for the other pterleotrine genera are needed to properly polarize the character states. CI=0.33; RI=0.60; RC=0.20.  
(15). Elongation of spines of male first dorsal fin: (0) - dorsal fin elongate; (1) - no elongation (Fig. 1). Parioglossus dotui, P. neocaledonicus, P. nudus, P. verticalis and Ptereleotris hanae do not have the first dorsal fin elongated, while all other taxa have state 0. Character state 1 evolved three times in the ingroup taxa, in P. verticalis, in the ancestor of P. dotui and P. neocaledonicus, and in the ancestor of P. nudus. It evolved independently in Ptereleotris hanae. CI=0.33; RI=0.50; RC=0.17.  
(16). Number of second dorsal-fin rays: (0) - more than 20; (1) - 15-19; (2) - 15 or fewer (15 rays could be coded as either 1 or 2, depending on the number in other specimens of the same species). All the outgroup taxa have more than 20 soft fin rays (see character 5 for comment regarding analysis). Parioglossus aporos, P. formosus and P. sinensis have character state 2; the character state for P. neocaledonicus, P. rainfordi, P. raoi and P. taeniatus is ambiguous (individual specimens may have character state 1 or 2), other taxa have character state 1. It is possible that character state 1 evolved once in this group and it is optimized as a potential synapomorphy for Parioglossus. Character state 2 evolved at least twice for this group: once in the ancestor of P. aporos, and once in the ancestor of P. taeniatus group or once for the ingroup taxa after P. taeniatus had separated. Character state 1 is also optimized as one of the potential synapomorphies for Parioglossus. CI=0.67; RI=0.75; RC=0.50.  
(17). Number of anal-fin rays: (0) - over 20; (1) - 15-20; (2) - 15 or fewer. (15 rays could be coded as either 1 or 2, depending on the count from individual specimens of the same species). Outgroup taxa have more rays (more than 20 - see comment under character 5); P. aporos, P. formosus and P. sinensis have the fewest fin rays (state 2), while the character states for P. rainfordi and P. raoi are ambiguous (it could be either state 1 or 2). All other ingroup taxa have character state 1. Character state 1 evolved once in the ingroup and was optimized as the potential synapomorphy for the ingroup taxa. Correlation between the numbers of dorsal and anal fin rays should not be assumed to be true unless it has been tested, and the null hypothesis is that they are not correlated. CI=0.67; RI=0.75; RC=0.50.  
(18). Dorsal fin pterygiophore formula: (0) - 3(22110); (1) - 3(32010). Only the species in Ptereleotris have pterygiophore formula of 3 (32010). It is a presumptive synapomorphy shared by members of Ptereleotris, and was used as such by Rennis and Hoese (1987) to defeine Ptereletris as monophyletic. CI=RI=RC=1.  
(19). Ossification of pterygiophores of the first dorsal fin: (0) - pterygiophores ossified; (1) - pterygiophores cartilaginous. Parioglossus dotui, P. neocaledonicus and P. nudus have cartilaginous pterygiophores; all the outgroup taxa and other ingroup taxa have ossified pterygiophores (condition for P. verticalis is unknown). Character state 1 evolved twice for the ingroup taxa: once in the ancestor of P. dotui and P. neocaledonicus and once in P. nudus. CI=0.50; RI=0.5; RC=0.25.  
(20). Ossification of pterygiophores of second dorsal fin: (0) - pterygiophores ossified; (1) - pterygiophores cartilaginous. All species except Parioglossus neocaledonicus and P. nudus have the pterygiophores of the second dorsal fin ossified. Character state 1 evolved independently in these two species. 0=0.50; RI=RC=0.  
(21). Ossification of pterygiophores of the anal fin: (0) - pterygiophores ossified. (1) - pterygiophores cartilaginous. All species except P. neocaledonicus and P. nudus have the pterygiophores of anal fin ossified. Character state 1 evolved twice independently for these two species. CI=0.50; RI=RC=0.  
(22). Proximal radials of pectoral fin: (0) - ossified; (1) - cartilaginous. Parioglossus dotui, P. neocaledonicus and P. nudus have cartilaginous radials; character state for P. philippinus is ambiguous, it could be 0 or 1, based on any instance coding, it was assigned state 1; condition for P. verticalis is unknown. All outgroup taxa and other ingroup taxa have ossified proximal radials. Character state 1 evolved twice among the ingroup taxa: once in the ancestor of P. dotui and P. neocaledonicus, and once in the ancestor of P. philippinus and P. nudus. 0=0.50; RI=0.67; RC=0.33.  
(23). Elongation of anterodorsal process of preopercle (Fig. 3): (0) - does not reach symplectic; (1) - reaches the anteroventral process of symplectic. Three species have an elongated anterodorsal process of preopercle, i.e. Ptereleotris hanae, Parioglossus philippinus and P. rainfordi. Other ingroup and outgroup taxa share the plesiomorphic condition (condition for P. galzini and P. verticalis unknown, based on optimization, they probably have character state 0). Optimization suggests that the elongated process evolved twice for the ingroup and once independently for P. hanae. CI=0.33; RI=RC=0.  
(24). Branching of posterior anal-fin rays: (0) - about 10 rays branched; (1) - unbranched. Parioglossus aporos, P. interruptus, P. nudus, P. palustris and P. philippinus possess character state 1, while all outgroup taxa and the remaining ingroup taxa have character state zero. Optimization suggests that character state 1 evolved once for the ingroup taxa after the ancestor of P.galzini had separated with two reversals to character state 0, once in the ancestor of P. taeniatus group and once in the ancestor of P. rainfordi. CI=0.33; RI=0.50; RC=0.17.  
Discussion  
Five most parsimonious trees were generated with a tree length of 74 steps with a CI = 0.4459; Retention Index (RI) = 0.6168; Rescaled Consistency Index (RC) = 0.2751. The results supported the monophyly of Parioglossus. The strict consensus tree of the five most equally parsimonious trees (Fig. 11) shows the following relationships: a monophyletic Parioglossus; a group containing P. dotui and P. neocaledonicus; and a large, fully resolved group of (P. galzini (P. aporos (P. nudus, P. philippinus,) (P. rainfordi (P. palustris (P. interruptus (P. taeniatus (P. formosus (P. raoi, P. sinensis)))))))). Ptereleotris microlepis and P. hanae are most closely related to each other among the outgroup taxa; however, their relationship with Nemateleotris magnifica and the genus Parioglossus was not resolved by this study. The monophyly of Parioglossus was supported by the following character states: 4(2), 5(2), 9(1),16(1) and 17(1). All these characters exhibited some degree of homoplasy.  
The Bremer support indices suggest that the cladogram for the ingroup is not a robust one. Nodal support showed that one conflicting step would collapse most nodes except the group of (P. nudus, P. philippinus), two more step will collapse all branches except for the monophyly of Parioglossus. There are several reasons for this. One is that it was not always easy to identify morphological characters that contained phylogenetic information, since “gobioid fishes have undergone both morphological specialization and degeneration” (Akihito et al., 2000: 14). Another line of argument is that the high levels of homoplasy may reflect inadequate character description. A better understanding of the ontogeny of the characters (and the their distribution throughout ontogenetic series) might clarify character interpretation, leading to better resolved/supported relationships, as pointed out to us by Gill (pers.comm.). Character optimization also suggests that subsequent character evolution and reversal occur commonly. The current study has a low Consistency Index, which suggests there is a lot of homoplasy present. Other possible reasons include such factors as the early evolution of species in geological time, which makes the tracing of their relationship very difficult (Murphy, per. comm.); or the clade may have speciated very rapidly within a short time frame, which would usually result in a polytomy. The study of Akihito et al. (2000) suggests that the gobioid fish may have evolved rapidly and relatively recently. The current study demonstrated that the osteology of Parioglossus is relatively conservative, except the caudal skeleton, and many putatively informative characters show homoplasy. This makes it more difficult to interpret relationships; other methods may have to be employed to satisfactorily solve the phylogeny of the genus.  
Despite these caveats, it should be noted that the monophyly of Parioglossus, the sister group status of P. dotui and P. neocaledonicus, and the fully resolved relationships of a monophyletic subgroup of 11 species were recovered in all five most equally parsimonious trees.  
Key to the adults of species of Parioglossus  
1. No head pores................................................................................................................2  
- Head pores present........................................................................................................3  
2. Branched caudal rays 7+6; body scaled; anal I 13-14 (usually I 14) (Indonesia).................................................................................................................................... P. aporos  
- Branched caudal rays 6+5; body naked; anal I 16-17 (Fiji, Solomon Islands, Papua New Guinea, Palau, Philippines)....................................................................... P. nudus  
3. 12-14 vertical bars on side below second dorsal fin.................................................... 4  
- No vertical bars on body...............................................................................................5  
4. Scales non-imbricate; black coloration around the anus of female (but not in males), freshwater (New Caledonia).............................................................. P. neocaledonicus  
- Scales imbricate; dark ring around anus of male holotype - only known specimen, marine (Caroline Islands)............................................................................. P. verticalis  
5. Distinct, dark lateral stripe present on body..................................................................6  
- Lateral stripe absent or diffuse stripe present without distinct dorsal and ventral margins.....................................................................................................................................11  
6. Posterior nasal pore absent; scales imbricate or non-imbricate....................................7  
- Posterior nasal pore present; scales non-imbricate.....................................................10  
7. Dorsal and anal fins usually I 17-18 (rarely I 16); posterior dorsal and anal rays unbranched (Papua New Guinea, Irian Jaya, Japan)................................. P. interruptus  
- Second dorsal fin usually I 14-15 (rarely I 16); posterior dorsal and anal rays branched.......................................................................................................................................8  
8. Dorsal edge of lateral stripe below midline of side of body; black spot at base of dorsal spines 5 and 6; circumorbital pores 2-4; (Fiji, Caroline Islands, Irian Jaya, Indonesia, Philippines, Japan, Andaman Islands, Singapore)................................................ P. raoi  
- Dorsal edge of lateral stripe along midline; no black spot at base of dorsal spines 5 and 6; four circumorbital pores............................................................................................ 9  
9. Preopercular pores absent; scales non-imbricate; longitudinal scale count 97-107 (China)........................................................................................................................ P. sinensis  
- Preopercular pores present; scales imbricate; longitudinal scale count 76-86 (Fiji, Palau, Philippines, Aldabra, Japan, Ryukyu Islands)................................... P. taeniatus  
10. Dorsal stripe on caudal fin present, extending obliquely downward to tips of rays above middle of fin; no dark vertical bar at base of caudal fin; preopercular pores present in specimens greater than 20 mm; dorsal and anal fins I 13-15, usually I 14; pectoral fin 15-17; dorsal spines 3 and 4 longest in males; anterior nasal opening a short tube (Fiji, Palau, Japan, Ryukyu Islands, Taiwan, Gulf of Thailand, Australia, Papua New Guinea, Indonesia, Philippines)................................................ P. formosus  
- No dark stripe on caudal fin; dark vertical bar at base of caudal rays; preopercular pores absent; dorsal and anal fins I 15-16; pectoral fin 18-20; dorsal spines 4 and 5 longest in males; anterior nasal opening a simple pore (Palau, Solomon Islands, Japan)......................................................................................................................... P. lineatus  
11. Branched caudal rays 6+5, dorsal spine 5 elongate in males over 20 mm, not elongated in females; gill opening narrow, ending ventrally just below lower pectoral base; posterior dorsal and anal rays usually unbranched, occasionally branched but rarely are all rays branched (Australia, Papua New Guinea, Philippines, Gulf of Thailand, India, Madagascar, Japan)................................................................................... P. philippinus  
- Branched caudal rays usually 7+6, rarely 6+6............................................................ 12  
12. Large, round spot on base of ventral caudal rays (usually rays 9-15); posterior dorsal and anal rays unbranched; preopercular pores present in specimens greater than 20 mm (Australia, Papua New Guinea, Borneo, Philippines, Japan)................. P. palustris  
- No large round spot confined to base of ventral caudal rays (if spot present, extending above midline); posterior dorsal and anal rays branched in specimens greater than 22 mm; preopercular pores present or absent................................................................... 13  
13. Gill opening narrow; lower attachment of branchiostegal membrane just below pectoral base; preopercular pores present (sometime absent in specimens less than 19 mm); five circumorbital pores; mouth angle 85-90° to longitudinal axis of body; anterior nasal opening a simple pore; males with a vertical bar at base of caudal rays, ventral portion of bar extending posteriorly towards tips; females with a round spot on rays 4- 12 (Australia, Papua New Guinea, Irian Jaya, Caroline Islands, Palau, Indonesia, Philippines, Japan).............................................................................................. P. rainfordi  
- Gill opening moderate; lower attachment of branchiostegal membrane below middle of operculum; preopercular pores absent.................................................................... 14  
14. Anterior nasal opening a simple pore; females with pale anus; caudal fin with a triangular to rectangular spot on base of caudal rays......................................................... 15  
- Anterior nasal opening a short tube; females with black ring around anus, caudal fin with a stripe, a round to elongate spot, or several vertical bars..................................16  
15. Scales imbricate, longitudinal scale count 83-85, the two dorsal fins not connected by membrane (Fiji).......................................................................................... P. triquestrus  
- Scales non-imbricate, longitudinal scale count 100-112, the two dorsal fins connected by membrane (Rapa)........................................................................................ P. galzini  
16. No dark stripe posterior to eye; dorsal spine 5 elongate in males; males and females without distinct round to horizontally elongate spot on middle caudal rays, males with stripe on middle rays of caudal fin extending to tips of rays, females with 3-4 vertical bars on middle rays; second dorsal and anal fins usually I 17-18 (New South Wales, Australia).................................................................................................... P. marginalis  
- Dark stripe posterior to eye; no dorsal spines elongate in males; males and females with distinct round to horizontally elongate spot on middle caudal rays, sometimes extending to tips of middle caudal rays; second dorsal and anal fins usually I 16-17 (Japan)............................................................................................................................. P. dotui
description: Published as part of Rui Wang & Richard Winterbottom, 2006, Osteology and phylogeny of Parioglossus (Teleostei, Gobioidei), with a revised key to the species., pp. 1-32 in Zootaxa 1131 on pages 15-26