Distribution and identification of the species in the genus Helicops Wagler, 1830 (Serpentes, Colubridae, Xenodontinae)

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Introduction
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 midbody (DSM), presence of dorsal keels at midbody (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, semidivided or entire (NA), presence of intergenials (IG). The number of ventral scales, number of subcaudal scales, snout-vent length, tail length and the ratio between snout vent length and tail length were recorded separately for male and female specimens. Measurements were taken using a tape measure with the accuracy of 0.1 cm. Ventrals were counted as proposed by Dowling (1951). The sex of the specimens was determined by exterior examination of the shape of the base of tail (tail bulge caused by presence of hemipenes in males, such bulge absent in females). The results of our examinations are available in Suppl. material 1. For specimens with a damaged tail, no tail measurements were done. The head scutellation was recorded for each side seperately.
The presented information on the species distribution is based on the locality data of the specimens examined and on literature data. One species locality was found browsing iNaturalist, the identification was made on the unique coloration of that species. Only records were included for which a reliable description of the locality or coordinates were available. All information on the literature references to the respective distribution point is listed in Suppl. material 2.
The distribution maps were created using QGIS 3.12.2 (Bucureşti) and the maps freely available at naturalearthdata.com.
The identification key was created using the morphological data gathered by specimens of Helicops examined by Y.S. and literature data. The literature references used for morphology are listed in Suppl. material 3.

Data resources
The Suppl. materials 2, 1 are tables in a tab delimited text format. Suppl. material 1contains the examination results for each specimen. It has columns with following headers: Species; Catalog numb.; Sex; Snout-venth length [mm]; Tail  Suppl. material 3 is a plain text file containing all the references used for the morphological assessment. It contains each reference in a seperate line.

Distribution
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 Sao Paulo.

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

Morphology remark
Moraes-da- Silva et al. (2019) states that H. apiaka has 19-21 dorsal scale rows at midbody, 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 diagnostic trait. However, the before mentioned publication examined the same specimens for H. apiaka as in the original species description (Kawashita-Ribeiro et al. 2013). Therefore, at this point we trust the data given in the original species description.

Diagnosis
Helicops boitata differs from all its congeners by the presence of an entire nasal scale and 25 dorsal scale rows at midbody, reducing to 21 anterior to cloaca (for information on references see Suppl. material 3).

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

Distribution
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).

Diagnosis
Helicops danieli is readily distinguished from its congeners by its spotted dorsum in combination with a ventral pattern consisting of 2 rows of semilunar marks on a light background (for information on references see Suppl. material 3).

Distribution
Helicops danieli is only present in Colombia. In Colombia it seems to range 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 a precise locality given.

Diagnosis
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. From H. angulatus it differs in having 125-132 ventrals in males and 128-132 in females (for information on references see Suppl. material 3).

Distribution
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).

Distribution
The distribution of H. hagmanni ranges from the estuary of the Amazonas to the Brazilian province Amazonas and the Venezuelan province Amazonas. There is also one record from northern Rondônia (Silva Jr 1993, Fig. 2a).

Morphologic remark
The examined specimens had smooth subcaudal scales on the anterior part of the tail, changing to weakly keeled scales at posterior tail (see also

Distribution
Helicops leopardinus is present from the northwest of Argentina to the estuary of the Amazon and from Ecuador to the Brazilian state Bahia. There are no records of this species in the central Amazon Basin (Fig. 2c).

Distribution
Helicops modestus is present 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 specimen from the southern shore of Uruguay and one literature report from Volta Grande do Xingu in the Brazilian province Para, near its estuary into the Amazon (Vaz- Silva et al. 2015, Fig. 2d).

Diagnosis
Helicops nentur differs from all its congeners by the combination of an entire nasal scale, and 17 dorsal scale rows at midbody (for information on references see Suppl. material 3).

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

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

Helicops petersi Rossman, 1976
Diagnosis Helicops petersi can be distinguished from all its congeners except H. pastazae by the combination of 21-23 dorsal scale rows at midbody, reducing to 16 anterior to cloaca, and 135-150 ventrals (for information on references see Suppl. material 3).

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

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

Diagnosis
Helicops polylepis can be distinguished from all its congeners by the combination of 23-26 dorsal scale rows at midbody, the absence of intergenials, and a semidivided nasal scale (for information on references see Suppl. material 3).

Distribution
Helicops polylepis is present from southern Bolivia to the Amazon estuary and from southeastern Peru to the Brazilian province Bahia (Fig. 3c).

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

Helicops tapajonicus da Frota, 2005
Diagnosis This species can be distinguished from all its congeners by 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).

Distribution
Helicops tapajonicus is known only from two localities at the river Tapajos close to its confluence with the Amazon in the Brazilian state Pará (Fig. 3e).

Diagnosis
This species can be distinguished from all congeners by the combination of having five narrow light stripes on the dorsum and a light venter with black semilunar markings, which extend onto the tail (for information on references see Suppl. material 3).

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

Morphology remark
The presence of intergenials seems to be a reliable identification character in the remaining species in this genus, whereas in H. trivittatus this character shows considerable variation. Intergenials are sometimes present, and there is no geographical pattern perceivable (pers. Com. Antonio Moraes).

Helicops yacu Rossman & Dixon, 1975
Diagnosis 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).

Distribution
Helicops yacu is known only from the Isla Yanamono in the Peruvian province Loreto (Rossman and Dixon 1975, Fig. 4).

Taxonomic remark
In Rossman and Abe (1979) Table 2; for information on references see Suppl. material 3).

Distribution
The specimen originates from the province Pernambuco in Brazil, no exact locality given.

Identification keys
Identification key to the species of Helicops Wagler, 1830 Dichotomous identification key created based on own examinations and literature listed in Suppl. material 3.  (Flores et al. 2010). Furthermore, we report the first specimen from the province Chuquisaca in Bolivia. The specimen ZMB 26215 was collected in Chaco, Chuquisaca, Bolivia. This extends the known distribution range over 800 km to the southwest from the nearest record by Griffin (1916) in southern Mato Grosso. The last range extension we report for this species is to the province Bahia in Brazil. The specimen ZMB 17428 was collected there, but no exact locality description is available.
The number of range extensions we report here is a sign, that the distribution range of the species in this genus is not well known. To get a better knowledge about the distribution a comprehensive examination of collection material on an international level and especially field work in the aquatic habitat of this genus is required.