Helicops angulatus can be distinguished from all its congeners, except H. scalaris and H. apiaka by having subcaudal keels, 17–20 dorsal scale rows at mid-body (compared to 19 in H. gomesi; 21–27 in H. hagmanni; 23–25 in H. pastazae) and 103–123 ventrals (compared to 125–132 in H. gomesi; 117–138 in H. hagmanni). From H. scalaris, it differs in having no intergenials (for information on references, see Suppl. material 3; for summarised pholidosis information of the examined specimens, see Tables 1, 2). For differentiation from H. apiaka, see identification of H. apiaka.

The distribution of H. angulatus extends over nearly the complete northern part of South America. As shown in Fig. 1a, the distribution range extends from Columbia to the east coast of Brazil and from Venezuela and offshore islands to the Brazilian Province of Sao Paulo and Bolivia.

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Figure 1.

Distribution maps of A Helicops angulatus; B H. apiaka; C H. boitata; D H. carinicaudus; E H. danieli; F H. gomesi. Black circles show examined specimens, white circles literature reports and grey circles show literature reports with ambiguous references. For coordinates and references of the point records, see Suppl. material 2.

According to the information given in Kawashita-Ribeiro et al. (2013), H. apiaka can be distinguished from all its congeners, except H. angulatus by the following combination of characteristics: absent intergenials, subcaudal keels present and 21–22 dorsal scale rows at mid-body (compared to 19 in H. gomesi). From H. angulatus, it differs by having 21–24 dorsal scale rows at anterior body, 21–22 at mid-body and 17–19 at posterior body (versus 19–21/19–20/17–19 in H. angulatus) and by having 118–127 ventral scales in males and 124–132 in females (versus 105–123 in male and 109–123 in female H. angulatus), as well as hemipenes morphology. The specimens examined in Kawashita-Ribeiro et al. (2013) originated from neighbouring areas to the H. apiaka locations. Our own examinations revealed that males of H. angulatus possess 103–119 ventrals in males and 104–125 in females. There is considerable overlap, especially between female specimens of the two species, thus excluding this character for identification. Besides that, we detected two specimens displaying morphology characters of H. angulatus (colouration, subcaudal keels, remaining pholidosis), but showing considerably more ventrals than other specimens of H. angulatus (SMF 17819, a female, with 156 ventrals and ZSM 0595/2003, female, with 130 ventrals). There is no locality information available for SMF 17819. ZSM 0595/2003 was collected at the Rio Parana in Porto Tibiriça, Sao Paulo, Brazil. This is approximately 1300 km distant from the distribution range of H. apiaka. The origin of a speciemen is probably an important feature in order to assign it to one of the two species (for information on references, see Suppl. material 3).

The only known specimens of H. apiaka are from northern Mato Grosso and southern Pará (Fig. 1b).

Regarding the number of dorsal scale roles at mid-body in H. apiaka, there is contradictory information. Moraes-da-Silva et al. (2019) states that H. apiaka has 19–21 dorsal scale rows at mid-body, which would eliminate this character as a diagnostic character to distinguish it from H. angulatus. This would leave only the number of ventrals in females as a sure diagnostic trait. However, in the original species description, Kawashita-Ribeiro et al. (2013) report 21–22 scale rows. At this point, we trust the data given by Kawashita-Ribeiro et al. (2013), as both publications examined the same specimens.

Helicops boitata differs from all its congeners by the combination of an entire nasal scale and 25 dorsal scale rows at mid-body, reducing to 21 anterior to cloaca (versus 17/15 in H. nentur; 28–28/18–20 in H. yacu) (for information on references, see Suppl. material 3).

Helicops boitata is only known from the Pantanal at Transpantaneira Road in the Municipality of Pocone, Mato Grosso, Brazil (Fig. 1c).

Helicops carinicaudus can be distinguished from all its congeners, except H. danieli, H. infrataeniatus, H. leopardinus and H. phantasma by the following combination of characteristics: 17–19 dorsal scale rows at mid-body, reducing to 17 anterior to cloaca (versus 17–20/17–19 in H. angulatus; 21–22/17–19 in H. apiaka; 25/21 in H. boitata; 19/19 in H. gomesi; 21–29/19–23 in H. hagmanni; 17–20/15–19 in H. modestus; 17/15 in H. nentur; 23–25/16–19 in H. pastazae; 21–23/16 in H. petersi; 23–26/17–21 in H. polylepis; 19–21/16–19 in H. scalaris; 19/17 in H. tapajonicus; 20–23/16–19 in H. trivittatus; 25–28/18–20 in H. yacu), 128–141 ventrals in males and 128–148 ventrals in females (versus ♂103–123♀104–125 in H. angulatus; ♂112–125♀112–124 in H. modestus; ♂110–119♀113–125 in H. scalaris; ♂118♀121–123 in H. tapajonicus). From H. danieli and H. leopardinus, it differs in having a striped or uniform dorsum versus blotched pattern in H. danieli and H. leopardinus. From H. infrataeniatus and H. phantasma, it differs in having a yellow or cream venter with two series of black semi-lunar marks, between these small, irregular black spots (for information on references, see Suppl. material 3).

The distribution of H. carinicaudus extends from the Estuary of the Rio de La Plata along the shoreline of Brazil to the Province Pernambuco (Fig. 1d).

Helicops danieli is readily distinguished from its congeners by its unique colour pattern, namely a spotted dorsum in combination with a ventral pattern consisting of two rows of semi-lunar marks on a light background (for information on references see, Suppl. material 3).

Helicops danieli is only occurring in Colombia, where it seems to be found mainly west of the Andes. There is a report from the lowland in the east near the Brazilian border (Yuki and Castano 1998, Fig. 1e). Specimen ZMB 9490 has the country-level locality Brazil without further precision.

Helicops gomesi is distinguished from all its congeners, except H. angulatus by having subcaudal keels, no intergenials, and 19 dorsal scale rows throughout its body (compared to 21–24/21–22/17–19 in H. apiaka). From H. angulatus, it differs in having 125–132 ventrals in males and 128–132 in females (versus 103–119 in males and 104–125 in females of H. angulatus); (for information on references, see Suppl. material 3).

The distribution of H. gomesi extends from the Brazilian Province Sao Paulo to the Provinces Mato Grosso, Mato Grosso do Sul and Goias (Fig. 1f).

Helicops hagmanni is distinguished from all its congeners by having subcaudal keels, 21–29 dorsal scale rows at mid-body (versus 17–20 in H. angulatus; 21–22 in H. apiaka; 19 in H. gomesi; 23–25 in H. pastazae) and 50–59 subcaudals (compared to 79–103 in H. apiaka; 72–117 in H. pastazae); (for information on references, see Suppl. material 3).

The distribution of H. hagmanni ranges from the Estuary of the Amazonas to the Brazilian Provinces Amazonas, Acre, Rondônia and the Venezuelan Province Amazonas. There is also one record from south-western Colombia (Rossman 1975, Fig. 2a).

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Figure 2.

Distribution maps of A Helicops hagmanni; B H. infrataeniatus; C H. leopardinus; D H. modestus; E H. nentur; F H. pastazae. Black circles show examined specimens, white circles literature reports and grey circles show literature reports with ambiguous references. For the coordinates and references of the distribution points from literature, see Suppl. material 2.

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 Moraes-da-Silva et al. (2019) who reported them to be absent, without further notes on methodology for this character (see also Tables 1, 2).

This species can be distinguished from all its congeners, except H. carinicaudus, H. nentur and H. tapajonicus by the combination of a uniform or longitudinally striped dorsum, a cream or red venter with 1–3 dark stripes or darkly checkered and 17–20 dorsal scale rows at mid-body (versus 20–23 in H. trivittatus). From H. nentur, it differs in having a semi-divided nasal scale, whereas H. nentur has an entire nasal scale. From H. carinicaudus, it differs in having a cream or red venter with 1–3 dark stripes or darkly checkered or black with light spots (versus two series of dark semi-lunar marks in H. carinicaudus). In some specimens, intermediate patterns are observed. From H. tapajonicus, it differs in having strongly keeled dorsal scales, whereas H. tapajonicus has only a weak dorsal keeling. Additionally, H. tapajonicus possesses a ventrolateral greenish stripe, which is absent in H. infrataeniatus (for information on references, see Suppl. material 3). Furthermore, H. tapajonicus and H. infrataeniatus have allopatric distribution ranges.

Helicops infrataeniatus is recorded from the southern Brazilian States Mato Grosso do Sul, Sao Paulo, Parana, Santa Catarina and Rio Grande do Sul and from Paraguay, Uruguay and north-western Argentina Carreira Vidal et al. (2005) (Fig. 2b).

Kawashita-Ribeiro et al. (2013) reported subcaudal keels in H. infrataeniatus. In contrast, 57 of the 58 examined specimens during this study showed smooth subcaudal scales. Only SMNS 3065 had subcaudal keels (see Tables 1, 2).

Helicops leopardinus is distinguished from all its congeners, except H. danieli and H. gomesi by the combination of a greyish-olive to greyish-brown dorsum with 4–5 series of alternating dark spots, absent intergenials and 18–22 dorsal scale rows at mid-body (versus 23–26 in H. polylepis). From H. danieli, it differs in having a cream, yellow or red venter, checkered or banded black or both (versus cream venter with two medial rows of black semi-lunar marks). From H. gomesi, it differs in having no subcaudal keels; (for information on references, see Suppl. material 3).

Helicops leopardinus records range from north-western Argentina to the Estuary of the Amazon and from Ecuador to the Brazilian State Bahia. There are nearly no records in the south-eastern provinces of Brazil (Fig. 2c).

ZSM 134/1947, a female, possesses 109 subcaudals (versus 53–88 in females of H. leopardinus). We interpret this as an abnormality (see also Tables 1, 2).

Helicops modestus differs from all its congeners, except H. carinicaudus, H. danieli, H. infrataeniatus, H. leopardinus, H. phantasma and H. tapajonicus by the absence of subcaudal keels and having 19 dorsal scale rows at anterior body. From the remaining species, it differs in having a black to dark green dorsum with indistinct longitudinal stripes and a nearly uniform light cream venter, sometimes with faint flecks; (for information on references, see Suppl. material 3).

Helicops modestus is occurring from the Brazilian Province Bahia to the Province Paraná and seems to range from the east shore of Brazil to the south of Mato Grosso. There is also one literature record from Volta Grande do Xingu in the Brazilian Province Para, near its estuary into the Amazon (Vaz-Silva et al. 2015, Fig. 2d).

Helicops nentur differs from all its congeners by the combination of an entire nasal scale and 17 dorsal scale rows at mid-body (versus 25 in H. boitata; 25–28 in H. yacu); (for information on references, see Suppl. material 3).

Helicops nentur is known only from the eastern part of the Brazilian Province Minas Gerais (Fig. 2e).

Helicops pastazae can be distinguished from all other congeners, except H. hagmanni and H. yacu by the combination of having subcaudal keels and intergenials present. From H. hagmanni, it differs in having 72–117 subcaudal scales (versus 50–59 in H. hagmanni). From H. yacu, it differs in having a semi-divided nasal scale (entire in H. yacu); (for information on references, see Suppl. material 3).

Helicops pastazae is found in the northern part of Ecuador and the eastern part of Venezuela. There are no reports from Colombia (Fig. 2f).

Helicops petersi can be distinguished from all its congeners, except H. yacu by the combination of present intergenials, absent subcaudal keels and 135–150 ventrals (versus 110–125 in H. scalaris; 114–130 in H. trivittatus). From H. yacu, it differs in having a semi-divided nasal scale (versus entire in H. yacu); (for information on references, see Suppl. material 3).

Helicops petersi is known only from a very small area in the Ecuadorian Province Napo (Fig. 3a).

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Figure 3.

Distribution maps of A Helicops petersi; B H. phantasma; C H. polylepis; D H. scalaris; E H. tapajonicus; F H. trivittatus. Black circles show examined specimens, white circles literature reports and grey circles show literature reports with ambiguous references. For coordinates and references of the distribution records, see Suppl. material 2.

Helicops phantasma can be distinguished from all other congeners by having a dorsal pattern of dark spots fusing to irregular black bands, absent intergenials and 19/19/17–19 dorsal scale rows with moderate keels (versus 25/25/21 in H. boitata; 19–21/18–20/16–19 in H. danieli; 19/19/19 in H. gomesi; 15–22/18–22/16–19 in H. leopardinus; 23–25/23–26/17–21 in H. polylepis) and hemipenial morphology (for information on references, see Suppl. material 3).

The species is only known from the Tocantins-Araguaia River Basin in the Provinces Tocantins, Mato Grosso and Maranhão in northern Brazil (Moraes-da-Silva et al. 2021, Fig. 3b).

Helicops polylepis can be distinguished from all its congeners by the combination of absent intergenials, a semi-divided nasal scale and 23–26 dorsal scale rows at mid-body (versus 17–20 in H. angulatus; 21–22 in H. apiaka; 17–19 in H. carinidaudus; 17–20 in H. infrataeniatus and H. modestus; 18–20 in H. danieli; 19 in H. gomesi; 18–22 in H. leopardinus; 19 in H. phantasma; 23–26 in H. polylepis; 19 in H. tapajonicus; (for information on references, see Suppl. material 3).

Helicops polylepis is recorded from southern Bolivia to the Amazon Estuary and from Peru to the east of the Brazilian Province Para. There are also two reports from Colombia (Fig. 3c).

This species can be distinguished from all its congeners, except H. trivittatus by the combination of having intergenials, 110–119 ventrals in males and 113–125 in females (versus ♂117–127♀130–138 in H. hagmanni; ♂121–134♀130–145 in H. pastazae; ♂135–142♀137–150 in H. petersi; ♂124♀129–136 in H. yacu) and 67–95 subcaudals (versus 55–59 in H. hagmanni). From H. trivittatus, it differs in having a blotched dorsum, versus striped in H. trivittatus (for information on references, see Suppl. material 3).

Helicops scalaris is known only from the northern border area between Colombia and Venezuela, western and north of Lake Maracaibo in Venezuela (Fig. 3d).

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 3).

Helicops tapajonicus is only known from two localities at the River Tapajos close to its confluence with the Amazon in the Brazilian State Para (Fig. 3e).

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 3).

Helicops trivittatus is present from the eastern part of the Brazilian Province Para to approximately its borders with Maranhao, Tocantins and northern Mato Grosso. There are no reports of this species from western Para (Fig. 3f).

The presence of intergenials seems to be a reliable identification character in all other species of this genus, whereas in H. trivittatus, this character shows considerable variation. Intergenials are sometimes present. In our dataset, there were two specimens with and two without intergenials. There is no obvious biogeographical pattern perceiveable (pers. Comm. Antonio Moraes-da-Silva).

Helicops yacu can be distinguished from all congeners by the combination of having an entire nasal scale and intergenials present (for information on references, see Suppl. material 3).

Helicops yacu is known only from north-eastern of the Province Loreto, Peru and one locality in north-western Acre, Brazil (Rossman and Dixon 1975, Nogueira et al. 2019, Fig. 4).

Figure 4.  

Distribution of Helicops yacu. White circles represent literature reports. For the coordinates and references of the distribution points from literature, see Suppl. material 2.

In Rossman and Abe (1979), the authors express their doubt that H. yacu represents a valid species. They state the possibility that individuals assigned to H. yacu might represent a subspecies of H. pastazae. However, they state that further specimens are needed for an accurate assessment. No further verification of this hypothesis has been made since then.

The female specimen SMF 34035 is distinguished from all other congeners, except H. angulatus, H. infrataeniatus and H. modestus by having 17 dorsal scale rows at mid-body and posterior body and 124 ventrals (compared to 111-117 in H. nentur). From the rest, it differs in having a black venter with cream, narrow transversal bands, which are approximately a ventral scale wide, often left and right halves are shifted one ventral scale, forming a pattern resembling a chessboard. Helicops angulatus has a banded venter, Helicops infrataeniatus has a venter either with three black stripes on a cream background or checkered black and cream, sometimes red, H. modestus has a uniform cream venter. Additionally, the specimen can be distinguished from H. infrataeniatus by its distribution. It originates from the Brazilian Province Pernambuco, whereas H. infrataeniatus occurs no further north than Mato Grosso do Sul in Brazil (Pholidosis of specimen 34035, see Table 3; for information on references, see Suppl. material 3).

The specimen originates from the Province Pernambuco in Brazil, no exact locality is available.