Corresponding author: Yannis Schöneberg (
Academic editor: Johannes Penner
The aquatic snakes of the genus
Here, we present distribution maps (point records), an identification key and comments on identification for all species in this genus. We base our results on a comprehensive literature review of over 300 scientific publications and own examinations. Our examinations comprise 190 specimens of 10 of the 19 currently recognised species and one
Water snakes of the genus
We base our species assessment of the genus
The examined morphologic characters were: snout-vent length (SVL), tail length (TL), the ratio between tail length and snout-vent length (TL/SVL), number of ventral shields (VE), number of subcaudal scales (SC), presence of subcaudal keels (SCK), number of preoculars (PRO), number of postoculars (PSO), number of loreals (LO), number of anterior temporals (AT), number of posterior temporals (PT), number of supralabials (SL), number of supralabials in contact with the eye (SL+E), number of infralabials (IL), number of dorsal scale rows at mid-body (DSM), presence of dorsal keels at mid-body (DKM), number of dorsal scale rows approximately a head length prior to cloaca (DSP), presence of dorsal keels approximately a head length prior to cloaca (DKP), if cloacal plate is divided (CL), if nasal scale is divided, semi-divided or entire (NA) and presence of intergenials (IG). For male and female specimens, we recorded the number of ventral scales, number of subcaudal scales, snout-vent length, tail length and the ratio between snout vent length and tail length separately. Measurements were taken using a millimetric tape measure and ventrals were counted as proposed by
We base the species’ distribution summaries on locality data of the examined specimens and additionally on literature data. One further locality was detected by browsing through iNaturalist (https://www.inaturalist.org/observations/9053312). We could identify the species (
We created the distribution maps using QGIS 3.12.2 and maps freely available at naturalearthdata.com.
We created the identification key using the morphological data gathered by examining specimens and literature data. Literature references used for morphology are listed in Suppl. material
Suppl. materials
Suppl. material
The distribution of
According to the information given in
The only known specimens of
Regarding the number of dorsal scale roles at mid-body in
The distribution of
The distribution of
The distribution of
The examined specimens had smooth subcaudal scales on the anterior part of the tail, changing to weakly-keeled scales at the posterior tail, which contrasts with the examination results in
This species can be distinguished from all its congeners, except
ZSM 134/1947, a female, possesses 109 subcaudals (versus 53–88 in females of
The species is only known from the Tocantins-Araguaia River Basin in the Provinces Tocantins, Mato Grosso and Maranhão in northern Brazil (
This species can be distinguished from all its congeners, except
This species can be distinguished from all its congeners by its unique colour pattern, namely the combination of a uniform moss-green dorsum, laterally with a greenish-yellow stripe and a black and greenish-yellow banded venter (for information on references, see Suppl. material
This species can be distinguished from all congeners by the unique colour pattern, namely a combination of five narrow light stripes on the dorsum and a light venter with black semi-lunar markings, which extend on to the tail (for information on references, see Suppl. material
The presence of intergenials seems to be a reliable identification character in all other species of this genus, whereas in
In
The female specimen SMF 34035 is distinguished from all other congeners, except
The specimen originates from the Province Pernambuco in Brazil, no exact locality is available.
1 | Dorsum uniform or with longitudinal stripes |
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– | Dorsum with blotches, spots or transverse bars |
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2 | Dorsum tan to dark brown with five rows of narrow light stripes, ventral cream with two uniform rows of dark brown to black semi-lunar marks |
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– | Colouration not as above |
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3 | Venter cream or yellow with 2–3 rows of black semi-lunar marks, 9–10 infralabials, 128–141 ventrals in males and 128–148 ventrals in females |
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– | Colouration and pholidosis not as above |
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4 | Nasal entire |
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– | Nasal semi-divided |
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5 | Ventral body cream, with or without faint brown flecks |
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– | Venter contrastingly checkered or with dark longitudinal stripes |
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6 | Dorsum uniform moss green, dorsal weakly keeled |
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– | Venter cream or red with 1–3 dark stripes or darkly checkered or black with light spots or intermediate forms; dorsal strongly keeled; dorsum dark brown with pale brown stripes |
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7 | Dorsal scale rows at mid-body 17, reducing to 15 anterior to cloaca; 56 subcaudals in the single known male, 41–52 in females; dorsum uniform dark olive, dark brown or dark grey |
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– | Dorsal scale rows at mid-body 25, reducing to 21 anterior to cloaca; 68 subcaudals in the single known male, unknown in females; dorsum greenish-copper brown with three longitudinal rows of dark, rectangular spots, venter light greyish-brown with two lateral rows of light orange spots |
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8 | Intergenials present |
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– | Intergenials absent |
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9 | Nasal entire; 85–96 subcaudals in females, unknown in males; 25–28 dorsal scale rows at mid-body, reducing to 18–20 anterior to cloaca; dorsum light to medium grey brown with 4 alternating rows of relatively small dark spots |
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– | Nasal semi-divided; 55–117 subcaudals in males, 51–97 in females; 19–29 dorsal scale rows at mid-body, reducing to 16–23 anterior to cloaca; colouration variable |
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10 | 55–67 subcaudals in males, 50–53 in females; dorsum grey brown with alternating light and dark circular blotches; northern South America |
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– | 83–117 subcaudals in males, 50–97 in females; colouration variable |
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11 | 110–119 ventrals in males, 113–125 in females; subcaudal keels absent; dorsum greyish-tan with 3–5 rows of irregular dark blotches, the vertebral blotches larger than laterals, all 3 usually fused longitudinally; northern South America |
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– | 121–142 subcaudals in males, 130–150 in females; subcaudal keels present; colouration variable |
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12 | Weak subcaudal keels present, 121–134 ventrals in males, 130–145 in females; 93–117 subcaudals in males, 72–97 in females; 23–25 dorsal scale rows at mid-body, reducing to 16–19 anterior to cloaca; ventral colouration cream with a series of dark crossbands or alternating checks, light ventral colour extending on to several dorsal scale rows; northern South America |
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– | Subcaudal keels absent, 135–142 ventrals in males, 137–150 in females; 85–91 subcaudals in males, 67–73 in females; 21–23 dorsal scale rows at mid-body, reducing to 16 anterior to cloaca; ventral colouration cream with a lateral series of dark checks; eastern Andean foothills of Ecuador |
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13 | Subcaudal keels present |
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– | Subcaudal keels absent |
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14 | 103–123 ventrals in males, 104–125 in females; 17–20 dorsal scale rows at mid-body |
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– | 118–132 ventrals in males, 124–132 in females or, if fewer than 124 ventrals in males, then 21–22 dorsal scale rows at mid-body |
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15 | 19 dorsal scale rows at mid-body; dorsum with dark blotches; one anterior temporal; 71–86 subcaudals in males, 67–73 in females; 125–132 ventrals in males, 128–132 in females |
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– | 21–24 dorsal scale rows at mid-body; dorsum with dark transverse bands; 2–3 anterior temporals; 79–103 subcaudals in males, 80–84 in females; 118–127 ventrals in males, 124–132 in females; northern Mato Grosso, Brazil |
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16 | Dorsum scale rows at mid-body 23–26, reducing to 17–21 anterior to cloaca; 71–101 subcaudals in males, 71–88 in females; 10–13 infralabials; venter dark with pale spots |
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– | Dorsum scale rows at mid-body 19–22, reducing to 16–19 anterior to cloaca; 64–89 subcaudals in males, 53–76 in females; 8–11 infralabials; venter checkered or banded black and red or cream with two medial rows of black semi-lunar marks, sometimes fused mid-ventrally |
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17 | 19 dorsal scale rows at anterior and mid-body and 17–19 dorsal scale rows anterior to cloaca; dorsal scales with moderate keels; dark dorsal spots fusing to transversal bands |
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– | Number of dorsal scale rows different |
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18 | Venter checkered or banded black and red; 108–129 ventrals in males, 108–138 in females |
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– | Venter cream with two medial rows of black semi-lunar marks, sometimes fused mid-ventrally; 125–135 ventrals in males, 130–141 in females |
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Dichotomous identification key, based on our own examinations and literature (listed in Suppl. material
The last published identification key by
Regarding the head scutellation, we found that only the presence of intergenial scales is a stable diagnostic character s in all species, except
Colouration seems to be a rather good character for distinguishing some species (e.g.
In
The presence versus the absence of subcaudal keels seems to be a stable character in most species. However, we found conflicting reports for this character in
We think it is possible that some species with supposedly large geographical distributions actually comprise species complexes. For example,
When comparing distribution data from our examined specimens with literature records, we discovered range extensions for five species. For
The number of range extensions we report shows that the distribution ranges of the species in this genus are not yet well known. In order to change that, a comprehensive examination of collected material at an international level and additional fieldwork are required.
We particularly want to thank Linda Mogk, Martin Jansen, Marcel Nebenführ and Joseph Vargas (all SMF), who always provided an honest opinion and friendly support. Furthermore, we thank Antonio Moraes-da-Silva, Rafaela França, Ricardo Alexandre Kawashita-Ribeiro, Omar Entiauspe, Santiago Carreira and Pier Cacciali for corresponding with us and sharing their knowledge. We thank the curators and collection managers permitting us access to their collections and providing additional information: Raffael Ernst (MTKD), Markus Auer (MTKD), Alexander Kupfer (SMNS), Mark Oliver Rödel (ZMB), Frank Tillack (ZMB), Claudia Koch (ZFMK), Morris Flecks (ZFMK), Frank Glaw (ZSM) and Michael Franzen (ZSM).
YS conducted the literature research, examined the specimens and wrote the first manuscript draft. GK was the academic supervisor and revised the manuscript.
Distribution maps of
Distribution maps of
Distribution maps of
Distribution of
Summarised results of the morphologic examination of 190 specimens. Abbreviations: N: Number of examined individuals; SVL: snout-vent length; TL: tail length; VE: ventrals; SC: subcaudals; SCK: presence of subcaudal keels; LO: loreals; PRO: preoculars; PSO: postoculars; AT: anterior temporals; PT: posterior temporals; SL: supralabials; SL+E: supralabials in contact with the eye; IL: infralabials; DSM: dorsal scale rows at mid-body; DKM: dorsal keels at mid-body; DSP: dorsal scale rows at posterior body; DKP: dorsal keels at posterior body; CL: cloacal plate; div: divided; IG: intergenials; NA: if nasal is divided; sdiv: semi-divided.; values in brackets show observations we rate as natural abnormalities, which are discussed in the respective species account. We rounded values to the third decimal place, lengths are in millimetres. See Suppl. material
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N | 47 | 11 | 5 | 2 | 57 |
SVL ♂ | 229–420 | 414–570 | 409 | 460 | 157–489 |
SVL ♀ | 145–680 | 280–810 | 163–620 | 575 | 136–600 |
TL ♂ | 128–275 | 160–190 | 194 | 174 | 66–174 |
TL ♀ | 30–325 | 90–203 | 62–185 | 185 | 45–194 |
TL/SVL ♂ | 0.417–0.696 | 0.330–0.387 | 0.474 | 0.378 | 0.311–0.526 |
TL/SVL ♀ | 0.185–0.922 | 0.235–0.321 | 0.271–0.380 | 0.323 | 0.209–0.462 |
VE ♂ | 103–119 | 139–141 | 128 | 123 | 114–128 |
VE ♀ | 104–125 |
128–146 | 131–139 | 131 | 113–130 |
SC ♂ | 69–100 | 64–71 | 79 | 59 | 58–88 |
SC ♀ | 58–92 | 51–59 | 60–81 | 50 | 49–74 |
SCK | present | absent | absent | present | absent |
LO | 1 | 1–2 | 1 | 1 | 0–3 |
PRO | 1–2 | 1–2 | 1 | 1 | 1–2 |
PSO | 2–3 | 2 | 2 | 1–2 | 2 |
AT | 1–3 | 1 | 1 | 1 | 1–2 |
PT | 2–4 | 1–2 | 2–3 | 3 | 1–3 |
SL | 8–9 | 7–8 | 7–8 | 8 | 7–8 |
SL+E | IV | IV, III–IV | IV, |
IV | III, III–IV, |
IL | 9–11 | 9–10 | 9–12 | 11–12 | 9–12 |
DSM | 17–20 | 17–19 | 18–19 | 25–27 | 17–20 |
DSM | present | present | present | present | present |
DSP | 16-17 | 17 | 17 | 21 | 15–17 |
DKP | present | present | present | present | present |
CL | div | div | div | div | div |
IG | absent | absent | absent | present | absent |
NA | sdiv | sdiv | sdiv | sdiv | sdiv |
See description Table
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N | 44 | 12 | 1 | 7 | 4 |
SVL ♂ | 217–495 | 165–305 | 415 | 170–235 | 328 |
SVL ♀ | 139–620 | 98–438 | 149–407 | 195–356 | |
TL ♂ | 114–194 | 68–125 | 250 | 86–98 | 118 |
TL |
53–235 | 33–129 | 58–69 | 118–134 | |
TL/SVL ♂ | 0.333–0.547 | 0.410–0.412 | 0.602 | 0.417–0.506 | 0,360 |
TL/SVL ♀ | 0.313–0.557 | 0.295–0.432 | 0.219–0.463 | 0.376–0.400 | |
VE ♂ | 110–129 | 114–116 | 130 | 123–126 | 122 |
VE ♀ | 109–127 | 112–124 | 122–128 | 116–119 | |
SC ♂ | 53–88 | 64–67 | 108 | 72–101 | 53 |
SC ♀ | 56–88 |
49–70 | 78–88 | 62–67 | |
SCK | absent | absent | present | absent | absent |
LO | 0–2 | 0–2 | 1 | 1 | 1 |
PRO | 1–2 | 1–2 | 1 | 1 | 2 |
PSO | 1–2 | 2 | 2 | 2 | 2 |
AT | 1–2 | 1 | 1 | 1–2 | 1 |
PT | 1–3 | 2 | 2 | 2–4 | 2 |
SL | 7–9 | 7–8 | 7 | 7–8 | 8 |
SL+E | III–IV, IV, IV-V | III–IV, IV | IV | III–IV, IV | IV |
IL | 9–11 | 9–11 | 10–11 | 10–13 | 11–14 |
DSM | 18–19 | 17–20 | 23 | 23 | 23 |
DSM | present | present | present | present | present |
DSP | 16–19 | 15–19 | 16 | 19–21 | 19 |
DKP | present | present | present | present | present |
CL | div | div | div | div | div |
IG | absent | absent | present | absent | variable |
NA | sdiv | sdiv | sdiv | sdiv | sdiv |
Pholidosis characters of the female specimen SMF 34035. Abbreviations: SVL: snout-vent length; TL: tail length; VE: ventrals; SC: subcaudals; presence of subcaudal keels (SCK); PRO: preoculars; PSO: postoculars; LO: loreal; AT: anterior temporals; NA: nasal; PT: posterior temporals; SL: supralabials; SL+E: supralabials in contact with the eye; IL: infralabials; DSM: dorsal scale rows at mid-body; DKM: dorsal keels at mid-body; DSP: dorsal scale rows at posterior body; DKP: dorsal keels at posterior body; CL: cloacal plate; IG: presence of Intergenials; Decimal values were rounded to the third decimal place, lengths are in millimetres. See Suppl. material
SVL | 365 | PT right | 2 |
TL | 189 | PT left | 2 |
TL/SVL | 0,518 | SL right | 8 |
VE | 124 | SL left | 8 |
SC | 75 | SL+E right | IV |
SCK | absent | SL+E left | IV |
PRO right | 1 | IL right | 10 |
PRO left | 1 | IL left | 10 |
LO right | 1 | DSM | 17 |
LO left | 1 | DKM | present |
PSO right | 2 | DSP | 17 |
PSO left | 2 | DKP | present |
AT right | 1 | CL | divided |
AT left | 1 | IG | absent |
NA | semi-divided |
Examination results
morphological
Examination results of all 190 specimens examined in this study.
File: oo_531784.tsv
References for all locality records extracted from literature
occurences
This table contains the description, coordinates and the reference of all used distribution points, which were extracted from literature.
File: oo_597917.tsv
References for the morphological data
morphological
This file contains all references used for the assessment of the morphological traits.
File: oo_531786.txt