Coluber bicarinatus Wied, 1820: 179; Wied (1824: Vol. 8), (1825: 284). On a sand beach of Lagoa, near the Rio Jucú, within “5 legoas” (leagues) of Villa do Espírito Santo (currently Vila Velha), state of Espírito Santo, Brazil.

Natrix bicarinatus – Merrem (1820: 117)

Erpetodryas bicarinatus – Boie (1826: 237)

Herpetodryas bicarinatus – Wagler (1830: 180)

Herpetodryas bicarinata – Fitzinger (1843: 26)

Herpetodryas carinatus (not Linnaeus, 1758) – Schlegel (1837: 177, in part), Duméril et al. (1854: 207, in part), Jan (1863: 80, in part), Boulenger (1894: 73 [var. C], in part)

Herpetodryas carinatus var. bicarinata – Boettger (1898: 55, in part)

Chironius carinatus (not Linnaeus, 1758) – Amaral (1925: 4, in part)

Chironius bicarinatus – Bailey (1955: 8, in part), Peters and Orejas-Miranda (1970: 59, in part), Dixon et al. (1993: 59, in part), Entiauspe-Neto et al. (2020, in part)

Adult male, apparently lost in the American Museum of Natural History (Vanzolini and Myers 2015) from a locality near Lagoa Grande (20°30’08.3″S, 40°21’32.4″W; ~2 m above sea level; hereafter a.s.l.), municipality of Vila Velha, state of Espírito Santo, Brazil. The data reported by Wied in the original description and in later studies (Wied 1824: color plate, Vol. 8 plate 2; 1825: 284) are adequate for the recognition of the species and its type locality, with the designation of a neotype being deemed unnecessary (ICZN 1999).

Chironius bicarinatus is distinguished from all congeners by the following unique combination of morphological characters: (i) dorsal scale rows 12/12/10; (ii) cloacal plate divided; (iii) dorsal scale rows keeled usually two; (iv) ventrals 147–170 in females, 145–165 in males; (v) subcaudals 130–157 in females, 125–154 in males; (vi) apical pits often present only on the cervical region; (vii) three supralabials contacting orbit; (viii) temporal formula usually 1+2; (ix) after preservation, uniform olive, grayish olive or bluish dorsum with a light vertebral stripe; (x) after preservation, labials predominantly yellowish, except for the last two or three supralabials, which may present the same color of dorsal series or postocular stripe; gular region, first third of belly, and subcaudals yellowish; remainder of the belly yellowish or bluish; (xi) a medially positioned black zig-zag line between subcaudals, gradually fading to the tip of the tail; outer margins with a black outline; (xii) hemipenial body generally ornamented with papillate calyces gradually replaced by smooth calyces toward the apex; (xiii) hemipenial body with each longitudinal row presenting 14–22 spines and 5–7 spines along sulcus spermaticus; (xiv) ventral surface of the septomaxilla smooth; (xv) anteroventral surface of prefrontal lacrimal foramen smooth; (xvi) maxillary teeth 30–38; (xvii) palatine teeth 23–24; (xviii) quadrate-suspensorium articulation with posterior end of supratemporals straight.

Chironius bicarinatus differs from most congeners, except for C. multiventris Schmidt & Walker, 1943, C. foveatus, C. septentrionalisDixon et al., 1993, Chironius cf. exoletus, and C. gouveai, by having 12/12/10 dorsal scale rows, divided cloacal plate, two keeled dorsal scale rows, presence of apical pits, and a greenish or olive dorsal pattern. Chironius bicarinatus differs from C. multiventris, C. foveatus and C. septentrionalis in its number of subcaudals 125–157 [138.7–142.0; 95% confidence intervals, hereafter] (vs. 156–208 in C. multiventris, 156–169 in C. foveatus and 165–181 in C. septentrionalis) and ventrals 145–170 [156.2, 157.4] (vs. 161–196 in C. multiventris, 163–174 in C. foveatus and 161–174 in C. septentrionalis).

The Atlantic populations of Chironius cf. exoletus (in parentheses) are the only ones that can present the aforementioned characters and a color pattern similar to C. bicarinatus. Specimens of Chironius cf. exoletus that have 12/12/10 dorsal scale rows are seldom observed (2% in our sample, with 12/12/8 being more frequent). Still, C. bicarinatus can also be differentiated by the number of maxillary teeth 30–38 [33.8–34.4] (vs. 23–31); outer margins of subcaudals pigmented black (vs. black pigmentation absent); ventral color pattern of tail usually with a black zig-zag line medially between subcaudals, gradually fading to the tip of the tail (vs. black zig-zag line maintaining the same intensity up to the tip of the tail); and hemipenial body elongated covered with more concentrated spines (vs. hemipenial body short with lower concentration of spines; see an illustration of the hemipenes in the supplementary information S1 of Klackzo et al. 2014).

Chironius bicarinatus differs from C. gouveai (in parentheses) in the number of ventrals 147–170 [157.0–159.0] in females and 145–165 [155.1–156.6] in males (vs. 156–174 [162.8–164.8] in females and 151–167 [157.9–159.3] in males); maxillary teeth 30–38 [33.8–34.4] (vs. 27–36 [30.5–31.4]); color pattern in preservative with uniformly olive, grayish olive or bluish dorsum and a black zig-zag line medially between subcaudals, gradually fading to the tip of tail (vs. dorsum usually uniform light brown, grayish olive or bluish, and dorsal and ventral scales with black or brown edges without a zig-zag line; see Entiauspe-Neto et al. 2020: fig. 3 for an illustration of this character); temporal formula usually 1+2 (vs. 1+1); ventral surface of septomaxilla smooth (vs. presence of a conspicuous projection); anteroventral surface of prefrontal lacrimal foramen smooth (vs. presence of a conspicuous projection); and posterior end of supratemporals straight (vs. slightly laterally curved).

Adult specimens with uniformly olive, grayish olive or bluish dorsum and light vertebral and postocular stripes that may or may not be evident, sometimes with black outer margins bordering it, more visible on the anterior part of the body. Predominantly pale yellowish labials, except for the last two or three supralabials, which may present the same dorsal or postocular stripe color. Ventrally, gular region, first third of the belly, and subcaudals pale yellowish; the remainder of the belly pale yellowish or bluish. Most have outer subcaudal margins with a black outline and a medially positioned black zig-zag line between subcaudals (gradually fading to the tip of the tail), which may vary in intensity and may even be absent in some specimens. Juvenile specimens have the same color pattern variation as adults, but they can also have a uniform olive brown dorsum and light crossbands on dorsum. In our sample, the presence of light crossbands on dorsum was found in juvenile specimens with a maximum SVL of 373 mm (CHUFJF 523) and in only one adult specimen (MNRJ 1839, SVL 830 mm), collected in the municipality of Passa Quatro, state of Minas Gerais, Brazil.

The description of color pattern while alive is based on photographs of six adult specimens (MNRJ 19138, 22017, 23571, 24194, 24877, 26255), and a juvenile specimen (MNRJ 27463), all collected in several localities of the state of Rio de Janeiro, Brazil; as well as on photographic material of other unvouchered specimens (iNaturalist, n = 9; see Appendix 2). Adult specimens have a uniformly green, olive or grayish olive dorsum with a light vertebral, sometimes with black outer margins bordering it, more visible on the anterior part of the body, and a black postocular stripe. Predominantly yellowish supralabials, except for the last two or three, which may present the same dorsal or postocular stripe color. Infralabials and gular region mostly whitish or yellowish; the first third of belly and subcaudals yellowish; the remainder of the belly whitish yellow. As in preserved specimens, while alive juvenile specimens also have a uniform olive brown dorsum and light crossbands on dorsum.

We analyzed the hemipenes of 23 specimens of Chironius bicarinatus, five of which were extracted from the specimens and manually fully everted, rendering almost or virtually maximally expanded organs. The description of hemipenes is based on the fully everted and maximally expanded left organs of the specimens MNRJ 4008, 25558, and also on the partially expanded organs of specimens MNRJ 8717, 25434; and the maximally expanded right organ of the specimen MNRJ 18909. Hemipenis unilobed, unicalyculate, noncapitate; subcylindrical shape, with a simple sulcus spermaticus, running centripetally from the base to the apex (MNRJ 4008) or slightly more than half of the hemipenis (MNRJ 25434); apex may present a nude area (MNRJ 25558) or may not (MNRJ 18909), generally with papillate calyces, but can also present calyces with few papillae on the apex and medial region (MNRJ 18909, 25558); each longitudinal row presenting 21–29 calyces; the calyces towards the hemipenial body are replaced by spinulate calyces; hemipenial body represents more than half of the total length of the organ, and is covered in spines that gradually increase in size toward the base, reaching maximum size at just over half of hemipenial body; each longitudinal row presenting 14–22 spines and 5–7 spines along sulcus; base mostly nude, ornamented by spinules at the upper portion and also laterally distributed on the proximal region of sulcus spermaticus; a basal naked pocket is present on the medial region.

Chironius bicarinatus is distributed in the Ombrophilous Dense and Semideciduous Forests along the coast, from the São Francisco River, state of Sergipe, Northeastern Brazil (northernmost record in the municipality of Capela; 10°32′S, 37°03′W), to the Serra do Tabuleiro, state of Santa Catarina, Southern Brazil (southernmost record in the municipality of Florianópolis; 27°35′38.5″S, 48°32′54.0″W) between sea level to ~930 m a.s.l..

The records of Chironius bicarinatus (ZVC 1336, MNHN 3924) in Montevideo, Uruguay, can be explained by the accidental introduction of specimens into the agricultural market of Montevideo by banana shipments from the state of São Paulo, Brazil (Carreira and Maneyro 2013). Strangely, two records of C. bicarinatus (CHUFC 3604, MZFS 1279) were reported from the municipalities of Mulungu and Juazeiro, respectively in the states of Ceará and Bahia. Similarly, we believe it is more likely that these records are also due to accidental introduction by banana shipments from the Bahia coastal region than that the representation of small, well-established populations above the São Francisco River. Possible evidence of this would be the northernmost records of C. bicarinatus (NMB 1303, 1304) reported by Dixon et al. (1993), further inland in the state of Bahia, municipality of Andaraí. We verified these records in the Institution’s catalog, which contained the following data: “BRA Bahia Andarahy pequeno > Andahary pequeno” donated by “Massini, Hans, Rio de Janeiro”. Thus, we can conclude that it is more likely that these records are from a location in the state of Rio de Janeiro, known as Tijuca (formerly known as Andaraí Pequeno), since the donor was a resident of this neighborhood.

Chironius bicarinatus – Bailey (1955: 8, in part), Orejas-Miranda (1958: 1), Peters and Orejas-Miranda (1970: 59, in part), Williams and Francini (1991: 63), Cei (1993: 538), Dixon et al. (1993: 59, in part), Achaval and Olmos (1997: 68), Giraudo (2001: 42), Carreira et al. (2005: 267), Carreira and Maneyro (2013: 148), Entiauspe-Neto et al. (2020, in part)

Adult male, CHFURG 4394, from municipality of Tapes (30°28′46.7″S, 51°23′46.1″W; ~74 m a.s.l.), state of Rio Grande do Sul, Brazil. The holotype was not examined first-hand, but its identity has been confirmed through the information present in the original description (Entiauspe-Neto et al. 2020).

Seven specimens, all from the state of Rio Grande do Sul, Brazil: Adult male, ZUFSM 2908, from the municipality of Bagé; adult male, ZFMK 103132 (formerly CHFURG 1504), from the municipality of Rio Grande; adult female, MCP 2631, at Rodeio Bonito, municipality of São Francisco de Paula; adult male and female, respectively, CHFURG 4823–24, at Ilha da Torotama, municipality of Rio Grande; adult male, MCP 8968, at Gomercinda Dornelles Fountoura School, municipality of Encruzilhada do Sul; adult male, MCP 12762, municipality of Triunfo (Entiauspe-Neto et al. 2020). Only the specimen MCP 8968 was examined first-hand.

Chironius gouveai is distinguished from all congeners by the following unique combination of morphological characters: (i) dorsal scale rows 12/12/10; (ii) cloacal plate divided; (iii) dorsal scale rows keeled usually two; (iv) ventrals 156–174 in females, 151–167 in males; (v) subcaudals 139–146 in females, 131–152 in males; (vi) apical pits often present only on the cervical region; (vii) three supralabials contacting orbit; (viii) temporal formula usually 1+1; (ix) after preservation, uniform light brown, grayish olive or bluish dorsum with a light vertebral stripe; and dorsals and ventrals with black or brown edges; (x) after preservation, labials predominantly yellowish or whitish, except for the last two or three supralabials, which may present the same color of dorsal series or postocular stripe; gular region, first third of belly, and subcaudals (which can also be whitish) yellowish; remainder of the belly can be yellowish, olive or bluish; (xi) subcaudals with black or brown edges; outer margins with a black outline; (xii) hemipenial body generally ornamented with papillate calyces gradually replaced by smooth calyces toward the apex; (xiii) hemipenial body with each longitudinal row presenting 14–19 spines and 5–6 spines along sulcus spermaticus; (xiv) ventral surface of the septomaxilla with a conspicuous projection; (xv) anteroventral surface of prefrontal lacrimal foramen with a conspicuous projection; (xvi) maxillary teeth 27–36; (xvii) palatine teeth 16–18; (xviii) quadrate-suspensorium articulation with posterior end of supratemporals slightly laterally curved.

Chironius gouveai differs from most congeners, except for C. multiventris, C. foveatus, C. septentrionalis, Chironius cf. exoletus, and C. bicarinatus, by having 12/12/10 dorsal scale rows, divided cloacal plate, two keeled dorsal scale rows, presence of apical pits, and a greenish or olive dorsal pattern. Chironius gouveai differs from C. multiventris, C. foveatus and C. septentrionalis in its number of subcaudals 131–152 [139.8–142.9; 95% confidence intervals] (vs. 156–208 in C. multiventris, 156–169 in C. foveatus and 165–181 in C. septentrionalis) and ventrals 151–174 [160.1–161.5] (vs. 161–196 in C. multiventris, 163–174 in C. foveatus and 161–174 in C. septentrionalis).

Chironius gouveai differs from Chironius cf. exoletus (in parentheses) in terms of number of maxillary teeth 27–36 [30.5–31.4] (vs. 23–31); outer margins of subcaudals with black pigmentation (vs. black pigmentation absent); ventral color pattern of tail usually with black or brown edges without a black zig-zag line medially (vs. a black zig-zag line medially between subcaudals); and hemipenial body elongated covered with more concentrated spines (vs. hemipenial body short with lower concentration of spines; see an illustration of the hemipenes in Klackzo et al. 2014).

Chironius gouveai differs from C. bicarinatus (in parentheses) in the number of ventrals 156–174 [162.8–164.8] in females and 151–167 [157.9–159.3] in males (vs. 147–170 [157.0–159.0] in females and 145–165 [155.1–156.6] in males); maxillary teeth 27–36 [30.5–31.4] (vs. 30–38 [33.8–34.4]); color pattern in preservative with dorsum usually uniform light brown, grayish olive or bluish, and dorsal and ventral scales with black or brown edges without a zig-zag line (vs. uniformly olive, grayish olive or bluish dorsum and a black zig-zag line medially between subcaudals, gradually fading to the tip of tail; see Entiauspe-Neto et al. 2020: fig. 3 for an illustration of this character); temporal formula usually 1+1 (vs. 1+2); ventral surface of septomaxilla with a conspicuous projection (vs. septomaxilla smooth); anteroventral surface of prefrontal lacrimal foramen with a conspicuous projection (vs. anteroventral surface of lacrimal foramen smooth); and posterior end of supratemporals slightly laterally curved (vs. straight).

Most adult specimens have a uniform light brown, grayish olive or bluish dorsum with a light vertebral stripe, that may or may not be evident, depending on the preserved condition, sometimes with black outer margins bordering it, more visible on the anterior part of the body. It is also possible to notice the presence of a black postocular stripe in better preserved specimens. Dorsals and ventrals with black or brown edges, more visible on the posterior part of the belly. Predominantly pale yellowish or whitish labials, except for the last two or three supralabials, which may present the same dorsal or postocular stripe color. Gular region, first third of belly, and subcaudals (which can also be whitish) pale yellowish; the remainder of the belly pale yellowish, olive or bluish. The outer margins of subcaudals have a black outline, which may vary in intensity and may even be absent in some specimens, and subcaudals have black or brown edges. Some specimens have remnants of black edges on subcaudals and only medially positioned black zig-zag line between subcaudals is evident.

The populations near Serra do Mar, in the states of Paraná and Santa Catarina (e.g., FML 1816, CHUFSC 244, 625, 788–90, 898, 1035, 1105, 2976–77), have a color pattern that is more similar to C. bicarinatus than those that occur in further inland locations. As with the C. bicarinatus specimens, they have a uniform olive or grayish olive dorsum; Gular region, first third of the belly, and subcaudals pale yellowish; the remainder of the belly pale yellowish or bluish; no black or brown edges on dorsals and ventrals; and the only distinguishable feature would be an evident black zig-zag line medially positioned between subcaudals with more intensity compared to C. bicarinatus, also gradually fading to the tip of the tail.

Juvenile specimens have the same color pattern variation as adults and juvenile specimens of C. bicarinatus, differing in the greater intensity of the black zig-zag line medially positioned between subcaudals or in the remnants of black or brown edges on dorsals and ventrals; neither may be evident in some preserved specimens, and it is therefore, only possible to distinguish juveniles of the related species by the combination of some meristic characters (e.g., temporal formula, number of subcaudals or maxillary teeth).

The description of color pattern while alive is based on photographs of an adult specimen (MACN 38879) collected in the province of Misiones, Argentina; a juvenile specimen (unvouchered specimen) from the municipality of Vacaria, state of Rio Grande do Sul, Brazil, as well as on photographic material of other unvouchered specimens (iNaturalist, n = 9; see Appendix 2).

Adult specimens with uniform light brown, grayish olive or olive dorsum and a light vertebral stripe, sometimes with black outer margins bordering it, more visible on the anterior part of the body. Dorsals and ventrals with black edges, more visible on the posterior part of the belly. Predominantly yellowish or whitish supralabials, except for the last two or three, which may present the same dorsal or postocular stripe color. Infralabials and gular region mostly yellowish or whitish; the first third of the belly (can also be whitish) and subcaudals yellowish or brownish yellow; the remainder of the belly whitish yellow or brownish yellow. For most specimens, the outer margins of subcaudals have a black outline and subcaudals have black edges.

We analyzed the hemipenes of 19 specimens, 13 of which were extracted from the specimens and prepared, rendering a fully everted and almost or virtually maximally expanded organs. The description is based on the fully everted and maximally expanded left organs of the specimens MCP 17282, MHNCI 12369, UFMT 1600, partially expanded organ of the specimen MHNCI 1529, and non-maximally expanded organs of the specimens MHNCI 7134, ZVC 2041, ZVC 3681; and on the fully everted and maximally expanded right organ of the specimen MCP 2423, and partially expanded organs of the specimens MCN 3144, MCN 14090. Retracted organs extend to the level of the twelfth subcaudal (n = 3). Hemipenis unilobed, unicalyculate, noncapitate, subcylindrical shape, with a simple sulcus spermaticus, running centripetally from the base to the apex (MCN 3144) or slightly more than half of the hemipenis (MHNCI 12369, UFMT 1600); no nude area on the apex, ornamented with papillate calyces in the sulcate side and with spinulate calyces in the middle of the asulcate side; hemipenis eventually showing calyces with few papillae on the apex and medial region (MHNCI 12369, UFMT 1600); each longitudinal row presenting 24–27 calyces; calyces towards hemipenial body replaced by spinulate calyces; hemipenial body with approximately more than half of the total length of the organ, and is covered in spines that gradually increase in size towards the base, reaching maximum size at just over half of the hemipenial body; with each longitudinal row presenting 14–19 spines and 5–6 spines along the sulcus spermaticus; base mostly nude, ornamented by spinules at the upper portion and also laterally distributed on the proximal region of the sulcus spermaticus; a basal naked pocket present on the medial region.

Chironius gouveai is widely distributed across inland Serra do Mar at higher altitudes in the Mixed and Semideciduous Forests, from the Paranapanema River (northernmost record in the municipality of Londrina; 23°18′34.6″S, 51°10′26.4″W) to the Uruguayan pampas (southernmost record in the province of Río Negro, M’Bopicua Port; 33°06′38.7″S, 58°11′31.6″W), with its western limit by the Paraná River (westernmost record in the province of Corrientes, Itá Ibaté, Argentina; 27°25′43.8″S, 57°20′17.0″W), between sea level to ~1030 m a.s.l..

The records of Chironius gouveai (ZVC 2041, 2956, 3681, 3727, MNHN 78, 1730, 1794, 5707) in the departments of Artigas, Río Negro and Salto, western Uruguay, can be explained by the attempt of specimens to cross the Uruguay River and their transportation by vegetation rafts along the river bed to the La Plata River (see Achaval et al. 1979). The record of C. gouveai (MHNCI 6028) from Montevideo needs to be clarified to confirm the occurrence of the species in southern Uruguay.

Chironius carinatus carinatus – Dixon et al. (1993: 73 [MZUSP 3633], in part)

Chironius bicarinatus – Borges-Nojosa (2007: 236), Guedes et al. (2014: 27, in part), Roberto and Loebmann (2016: 142), Entiauspe-Neto et al. (2020: 102, in part)

Adult male, MNRJ 27716 (formerly CHUFC 3304), collected by Clécio Aragão on January 11, 1998 at Horto Florestal (4°13′23.9″S, 38°55′28.1″W; ~800 m a.s.l.), Granja neighborhood, municipality of Pacoti, state of Ceará, Brazil.

Seventeen specimens, all from Baturité Massif, state of Ceará, Brazil: juvenile female, CHUFC 1389, collected by P. Cascon on April 27, 1989 at Mata do Remanso (4°14′34.1″S, 38°55′46.6″W), municipality of Guaramiranga; adult female, CHUFC 1414, collected by R. Otoch on September 28, 1989 at Sítio Abreu (4°15′23.3″S, 38°56′59.7″W), municipality of Guaramiranga; adult female, CHUFC 2383, collected by D.M. Borges-Nojosa on January 28, 2000 in the municipality of Pacoti; adult male, CHUFC 2747, collected by D.M. Borges-Nojosa on November 02, 1997 at Sítio Olho D’Água dos Tangarás (4°14′16.4″S, 38°54′56.7″W), municipality of Pacoti; adult male, CHUFC 2751, collected by D.M. Borges-Nojosa on August 15, 1998 at Horto Florestal, Granja (4°13′23.9″S, 38°55′28.1″W), municipality of Pacoti; adult female, CHUFC 2759, collected by D.M. Borges-Nojosa on January 11, 1998 at Horto Florestal, Granja, municipality of Pacoti; adult female, CHUFC 2840, collected by W.C. Luz on June 27, 2006 in the municipality of Pacoti; adult female, CHUFC 3305, collected by C. Aragão on December 16, 1997 at Linha da Serra community (4°13′53.8″S, 38°59′18.7″W), municipality of Guaramiranga; adult male, CHUFPB 17304, from APA da Serra de Baturité (4°16′35.7″S, 38°56′26.7″W), municipality of Guaramiranga; adult male, FUNED 1012, collected by E.O. Barros on May 22, 1988 at Sítio Macapá (4°15′53″S, 38°56′0.1″W), municipality of Guaramiranga; adult female, MHNCE-R 59, collected by D.C. Lima on October 18, 2019 at Museu de História Natural do Ceará Prof. Dias da Rocha (4°13′35.5″S, 38°55′21.9″W), municipality of Pacoti; adult female, MNRJ 27803, collected by S.V. Mendonça and L. Tavares on November 28, 2020 at Museu de História Natural do Ceará Prof. Dias da Rocha; adult male, MNRJ 27804, collected by T. Cavalcante, L. Lima, V.L.M. Rodrigues and L. Silva on May 29, 2022 at Pernambuquinho (4°13′21.6″S, 38°58′10.9″W), municipality of Guaramiranga; subadult female, MHNCE-R 577, collected by J.A. Oliveira on July 18, 2022 at Museu de História Natural do Ceará Prof. Dias da Rocha; adult male, MHNCE-R 616, collected by J.A. Oliveira on November 30, 2022 at Museu de História Natural do Ceará Prof. Dias da Rocha; adult male, MNRJ 27717, collected by D.M. Borges-Nojosa on January 03, 1999 at Sítio Olho D’Água dos Tangarás, municipality of Pacoti; adult male, MNRJ 27718, collected by C. Aragão on December 18, 1997 at Sítio Pau D›Alho (4°13′32.2″S, 38°55′34.8″W), municipality of Pacoti.

Chironius dracomaris can be distinguished from all congeners by the following unique combination of morphological characters: (i) dorsal scale rows 12/12/10; (ii) cloacal plate divided; (iii) two or more keeled dorsal scale rows (2^nd–11^th dorsal rows); (iv) ventrals 154–162 in females, 149–159 in males; (v) subcaudals 124–135 in females, 132–138 in males; (vi) apical pits present on the cervical and in at least one other region of the body (paravertebral rows, cloacal region, and/or tail); (vii) three or two supralabials contacting orbit; (viii) temporal formula usually 1+2; (ix) after preservation, uniform grayish olive or bluish dorsum with a light vertebral stripe and two black stripes visible from neck to midbody; (x) after preservation, the snout (rostral, nasals and internasals) can be light brown or have the same dorsal color; labials predominantly whitish, except for the last two supralabials, which may present the same color of dorsal series or postocular stripe; gular region, first third of belly, near cloacal region and subcaudals whitish; remainder of the belly olive or bluish; (xi) subcaudals have slightly black edges; (xii) hemipenial body generally ornamented with papillate calyces gradually replaced by a small concentration of smooth calyces on the proximal region at the end of the sulcus spermaticus; (xiii) each longitudinal row of hemipenial body has 15–22 spines and 5–8 spines along sulcus spermaticus; (xiv) ventral surface of the septomaxilla smooth; (xv) anteroventral surface of prefrontal lacrimal foramen smooth; (xvi) 34–39 maxillary teeth; (xvii) palatine teeth 24; (xviii) quadrate-suspensorium articulation with posterior end of supratemporals straight.

The new species differs from most congeners, except for Chironius bicarinatus, C. gouveai, C. multiventris, C. foveatus, and C. septentrionalis, by having 12/12/10 dorsal scale rows, divided cloacal plate, two or more keeled dorsal scale rows, the presence of apical pits, and a greenish or olive dorsal pattern. Regarding the species of the C. multiventris complex (C. multiventris, C. foveatus, and C. septentrionalis), Chironius dracomaris can be easily distinguished by the number of subcaudals 124–138 [129.1–132.2; 95% confidence intervals] (vs. 156–208 in C. multiventris, 156–169 in C. foveatus and 165–181 in C. septentrionalis) and ventrals 149–162 [154.7–156.1] (vs. 161–196 in C. multiventris, 163–174 in C. foveatus and 161–174 in C. septentrionalis).

Chironius dracomaris differs from C. gouveai (in parentheses) in the number of subcaudals 124–135 [127.7–130.9] in females and 132–138 [131.3–136.0] in males (vs. 139–146 [140.2–143.4] females and 131–152 [139.1–143.4] males); maxillary teeth 34–39 [35.3–36.0] (vs. 27–36 [30.5–31.4); temporals usually 1+2 (vs. 1+1); apical pits present on the cervical and in at least one other region of the body [e.g., paravertebral rows, cloacal region, and/or tail] (vs. usually only on the neck); color pattern in preservative: uniform grayish olive or bluish dorsum and two black dorsolateral stripes visible from neck to midbody (vs. usually a uniform light brown, grayish olive or bluish dorsum; dorsal and ventral scales with black or brown edges); subcaudals with slightly black edges, outer margins without a black outline or a black zig-zag line medially positioned between subcaudals (vs. outer margins with a black outline and subcaudals with black or brown edges; see Fig. 9 and Entiauspe-Neto et al. 2020: fig. 3 for an illustration of this character); ventral surface of the septomaxilla smooth (vs. presence of conspicuous projection); anteroventral surface of prefrontal lacrimal foramen smooth (vs. presence of a conspicuous projection); and posterior end of supratemporals straight (vs. slightly laterally curved).

Chironius dracomaris differs from C. bicarinatus (in parentheses), in the number of subcaudals 124–135 [127.7–130.9] in females and 132–138 [131.3–136.0] in males (vs. 130–157 [137.8–142.9] in females and 125–154 [138.1–142.6] in males); maxillary teeth 34–39 [35.3–36.0] (vs. 30–38 [33.8–34.4]); color pattern in preservative: uniform grayish olive or bluish dorsum and two black dorsolateral stripes visible from neck to midbody (vs. a uniform olive, grayish olive or bluish dorsum); and subcaudals with slightly black edges, outer margins without a black outline or a black zig-zag line medially positioned between subcaudals (vs. outer margins with a black outline and a medially positioned black zig-zag line between subcaudals, gradually fading to the tip of the tail; see Fig. 9).

SVL 652 mm; midbody diameter 13.88 mm (2.1% SVL); CL 332 mm (tail tip broken); head distinct from the neck; head length 19.26 mm (2.9% SVL); head width 10.25 mm (53.2% head length); head height 9.11 mm. Head arched in lateral view; snout rounded in dorsal view; canthus rostralis slightly defined. Interocular distance 8.30 mm; snout width (at loreals level) 6.68 mm; distance between nostrils 4.99 mm; snout length 7.53 mm; nostril-orbit distance 4.31 mm; rostral subtriangular, twice as long as high, 2.05 mm high, 4.32 mm wide, slightly visible in dorsal view; internasal 2.7 mm long, 2.7 mm wide, in frontal view, internasal suture slightly straight with respect to prefrontal suture; prefrontal 3.2 mm long, 3.9 mm wide; supraocular subtrapezoidal, 6.8 mm long, 2.9 mm wide; frontal subpentagonal, 6.4 mm long, 4.5 mm wide; parietal 8.1 mm long, 5.2 mm wide; nasal divided, nostril restricted to anterior nasal; anterior nasal 2.4 mm long, 1.7 mm high; posterior nasal 1.2 mm long, 1.7 mm high; loreal longer than higher (2.2 x 1.2 mm); second and third supralabial contacting loreal; preocular (1.5 mm long, 3 mm high); orbit diameter 5.6 mm; pupil rounded; two postoculars, the upper one higher than the lower (2.1 x 1.3 mm); temporals 1+2 (1+1 on the left side); anterior temporal 3.9 mm long, 2.6 mm high; anterior temporal in contact with parietal, postoculars, and seventh–ninth supralabial; upper posterior temporal higher than lower posterior temporal; upper posterior temporal 2.7 mm long, 1.9 mm high; lower posterior temporal 2.7 mm long, 1.3 mm high; supralabials 9, fifth–sixth with orbit; first to third supralabial similar in size and higher than fourth supralabial (longer than first supralabial); the remaining supralabial (fifth–ninth) longer and higher than first four supralabials; symphysial triangular; infralabials 10, first five infralabials contacting the first pair of chinshields and fifth–sixth with the second one; the first pair of chinshields 5 mm long, 2.3 mm wide; the second pair of chinshields 6.8 mm long, 2 mm wide; ventrals 152; subcaudals 127/127 (tail tip broken); cloacal plate divided; dorsal scale in 12/12/10 rows; the anterior part of the body has two rows of keeled dorsal scales (6^th, 7^th) with low intensity on neck region and remnants of keeled scales (2^nd–11^th dorsal rows), which increase in intensity towards midbody; in the midbody, all scales (2^nd–11^th dorsal rows) have a strong keel intensity; in the posterior region up to the cloaca, there are remnants of keeled scales (1^st, 12^th dorsal rows), some weak keeled scales (2^nd–9^th dorsal rows), and the paravertebral rows (6^th, 7^th) still with strong intensity, being the only keeled rows that reach the tail; apical pits on the neck, paravertebral rows and tail; maxillary teeth 35/34.

Uniform grayish olive dorsum with a light vertebral stripe and two black dorsolateral stripes on each side visible from neck to midbody (until the 75^th ventral); presence of a black postocular stripe; snout (rostral, nasals and internasals) light brown; predominantly whitish labials, except for the last supralabial, which presents the same postocular stripe color. Gular region, the first third of the belly, near cloacal region and subcaudals whitish; the remainder of the belly olive; subcaudals with slightly black edges.

Adult specimens have a uniform bluish dorsum with a light vertebral stripe and two dorsolateral black stripes, laterally visible from neck to midbody, which may or may not be evident, depending on the preserved condition, as well as the presence of a black postocular stripe. The snout can have the same dorsal color; predominantly whitish labials, except for the last two supralabials, which may present the same dorsal or postocular stripe color. Gular region, the first third of the belly, near cloacal region and subcaudals whitish; the remainder of the belly may be bluish. Juvenile specimens have the same color pattern variation present in adults, but they have a uniform olive brown dorsum and light crossbands along the dorsum. In our sample, the presence of light crossbands on the dorsum was found in juvenile specimens with a maximum SVL of 257 mm (CHUFC 3226) from Sítio São José, Pacoti, Ceará.

The description of color pattern while alive is based on photographs of adult specimens MNRJ 27803 and MHNCE-R 577 from Pacoti and IBSP 76994 or 76995 from Sítio Álvaro, Guaramiranga, both in Ceará state. The latter specimens were destroyed in a fire on May 15, 2010, only leaving photographic material of one of the specimens while alive. Adult specimens of Chironius dracomaris have a uniform green or olive dorsum; snout and first supralabials without contact with the orbit light brown; other labial scales and gular region whitish; the first third of the belly, near cloacal region and subcaudals yellowish; the remainder of the belly greenish.

Based on the fully everted and maximally expanded left organ of the specimens MNRJ 27717 and MNRJ 27804, partially expanded organ of the specimen MNRJ 27718; and on the fully everted and maximally expanded right organ of the specimen MNRJ 27716, and partially everted organ of the specimen CHUFPB 17304 (n = 5). Retracted organs extend to level of eighth or ninth subcaudal (n = 3). Hemipenis unilobed, unicalyculate, noncapitate, subcylindrical shape, with a simple sulcus spermaticus, running centripetally from the base to slightly more than half of the hemipenis, not reaching the apex (MNRJ 27717); no nude area on the apex, which is ornamented with papillate calyces on the sulcate side and with spinulate calyces in the middle of the asulcate side; hemipenis also presenting calyces with few papillae on proximal region of the end of sulcus; each longitudinal row has 23–29 calyces; calyces towards hemipenial body replaced by spinulate calyces; hemipenial body represents approximately more than half of the total length of the organ, and is covered in spines that gradually increase in size toward the base, reaching maximum size at just over half of the body; each longitudinal row has 15–22 spines and 5–8 spines along sulcus spermaticus; base mostly nude, ornamented by spinules on the upper portion and also laterally distributed on the proximal region of sulcus spermaticus; a basal naked pocket present on the medial region.

The description of the skull of Chironius dracomaris is based on a scanned specimen MNRJ 27717 (paratype, SVL 680 mm). Snout Complex. Premaxilla: subtriangular in frontal view, with the ascending process oriented posterodorsally without contacting anterior end of nasals; in lateral view, anterior edge of the ascending process straight; transverse process elongated and projected laterally, slightly shorter than ascending process (sensu Klaczko et al. 2014); in ventral view, vomerine processes long (sensu Klaczko et al. 2014), posteriorly oriented, does not contact anterior end of vomers; septomaxillae: strongly convex dorsomedially, with long ascending conchal process extending anterolaterally, does not reach the ends of nasals; slightly separated from each other; prominent projection on the posterolateral edge of vomeronasal cupola of the septomaxilla, approaching frontals posteriorly, one side in contact with the frontal and the other slightly separated; posterior portion contacts vomers ventrally; absence of a conspicuous extension in the medial portion of septomaxilla ventrally oriented; nasals: in contact medially, with anterior processes tapered; no contact with premaxilla; oval anterolateral processes (sensu Klaczko et al. 2014); posterior processes almost contact anterior part of frontals; vertical lamina do not contact septomaxillae; vomers: with globular mesoventral portion with rounded opening corresponding to exochoanal fenestra; in this region, vomers approach medially and almost contact anterior region of the palatine laterally; large vertical posteromedial laminae with a large circular fenestra; also presents foramina in vertical laminae in the antero and mesoposterior portions; vomeronasal cupula with a tapered process projected posterodorsally above circular fenestra.

Prefrontals: in contact with frontals dorsally, and approaching the maxillary process of palatine making little contact on only one side ventrally; in anterodorsal view, they present a process directed medially in basal portion; in lateral view, lacrimal foramen visible in basal portion; broad and rounded anterior process; posterior portion concave, forming anterior border of orbital cavity; large lacrimal foramen without a conspicuous projection on the anteroventral surface; frontals: in dorsal view, frontals in contact, with a straight medial suture; anterior margin rounded; anterolateral margins oblique and in contact with prefrontals; posterolateral margins slightly curved, forming the dorsal margin of orbital cavity; suture contacting parietals oblique, with the presence of foramina in the posterolateral region of frontals; vertical laminae in contact with parabasisphenoid ventrally and septomaxilla anteriorly; parietal: in dorsal view, almost rounded, as long as broad, with depressions on the mesoanterior and lateral margins, forming ridges on the lateral margins; anterior margins oblique in contact with frontals; also form posterodorsal border of orbital cavity; it contacts postorbital anterolaterally; posterior margins rounded in contact with supraoccipital medially; in lateral and ventral views, contacts posterior portion of parasphenoid rostrum anteriorly and basisphenoid lateromedially; posterolaterally contacting anterior margin of prootics and supratemporals; postorbitals: long, slightly curved, forming the posterolateral margin of the orbital cavity; they contact lateral process of parietal dorsomedially, but do not make contact in the basal region; no contact with frontals and broadly separated from ectopterygoid; supraoccipital: in dorsal view, subpentagonal, broader than long, oblique anterior and posterior margins, in contact with parietal anteriorly, with prootics laterally and exoccipitals posteriorly positioned; a constriction in the mesolateral region creates a depression with a foramen in the posterior part; conspicuous medial crests, between these crests emerges a pronounced medial crest perpendicularly in the posterior region, separating two depressions, each one presenting a foramen in basal region; exoccipitals: with a medial constriction and continuing lateral ridges; contact supraoccipital anteriorly, prootics and supratemporals laterally, and basioccipital ventrally; in lateral view, form posterior margin of fenestrae ovalis in contact with prootic anteriorly; presence of foramina ventrally and laterally on posterior margin; also forms the dorsal, lateral, and lateroventral margins of the foramen magnum; columella directed to the inner surface of quadrate; basioccipital: hexagonal, contacting parabasisphenoid complex anteriorly, prootics and exoccipitals, anterolaterally and posterolaterally, respectively; also forms ventral margin of foramen magnum posteriorly; with two conspicuous medial ridges; a larger perpendicular crest emerges between these ridges that extends to the posterior region; prootics: overlain by supratemporals in dorsal region; contacts parietal dorsally and anterolaterally, parabasisphenoid complex and basioccipital ventrally, supraoccipital dorsoposteriorly, and exoccipital posterolaterally; in lateral view, each with two large and three small foramina (two below the large foramina and one above); posteriorly, form anterior margin of fenestrae ovalis in contact with exoccipitals; parabasisphenoid complex: basisphenoid and parasphenoid fused in ventral view, but separate in dorsal view; in dorsal view, basisphenoid trapezoidal shaped, with a large median cavity, and spear shaped parasphenoid, tapering from the level of anterior margin of ectopterygoid, surpassing the palatine choanal process; basisphenoid contacts basioccipital posteriorly, prootic and parietal posterodorsally; parasphenoid contacts frontal dorsoanteriorly, and approaches, but does not contact posterior vomers and choanal process of palatine anteroventrally; in dorsal view, parasphenoid rostrum with lateral groove on each side along its length, with extension on medial part; in ventral view, posterior part of parasphenoid rostrum presents an extension laterally; in ventral view, basisphenoid has two lateral ridges, one extending to suture of prootic and the other to the half where two foramina are present; two further foramina are present on each side of basisphenoid anterior to the ridges.

Maxillae: elongated (sensu Klaczko et al. 2014), extends to the level of vomerine premaxilla processes to posterior border of postorbital, surpassing the palatine medially; in dorsal view, arched towards premaxilla in anterior portion, with a constriction at the level of prefrontal, which present a lateral extension approaching palatine; presence of a foramen anteriorly to the lateral extension; posterior portion with a lateral extension with a slight overlap with ectopterygoid, but without contact, forming the inferior margin of orbital cavity; ventral surface with 34–36 subequal, curved, and rear facing teeth, increasing in size towards the last five teeth; ectopterygoids: narrow, slightly curved; semicircle-shaped anterior margin with a rectangular lateral process, that overlaps maxilla; slightly curved posterior process; ventral surface of posterior portion in contact with dorsolateral surface of pterygoid medially; pterygoids: elongated, corresponding approximately to slightly more than half the size of braincase; ventral surface with 30–31 subequal, curved, and rear facing teeth; anterior portion tapered, presenting a slight overlap with posterior portion of palatine and gradually widening from the region of contact with ectopterygoid in anteroposterior direction, tapering again near the rounded posterior end, where both move away in curvature approaching quadrate-compound bone joint laterally; dorsal surface with a lateral longitudinal ridge from the posterior level of contact with ectopterygoid, extending almost to the end of the broad posterior region; palatines: slender, almost straight; ventral surface with 24 subequal, slightly curved, and rear facing teeth; in dorsal view, almost contacting globular portion of vomers in anterior portion; choanal process dorsomedially directed toward parasphenoid rostrum, but without contact; short maxillary process situated at level of anterior border of choanal process on lateral surface of palatine, directed posterolaterally, contacting small portion of prefrontal ventromedial surface, but no contact with palatine process of maxilla; presence of a foramen in the medial region of maxillary process; a short bifurcation before the pterygoid contact zone in posterior portion, with medial branch longer than lateral branch; the medial branch overlaps and contacts the anterior border of pterygoid.

Supratemporals: sub-rectangular, elongated, slightly curved lateromedially; anterior portion does not surpass parietal–prootic suture; overlapping and contacting prootic and exoccipital laterally, with half of supratemporal articulating with quadrate laterally; posterior end straight, surpassing the posterior portion of exoccipital; quadrates: flattened and broad dorsally, tapering and slightly curving dorsoventrally; dorsal portion contacting supratemporal laterally; medial portion with short process, near columella auris; ventral portion articulates with compound bone; ventromedial portion approaching, but not in contact with pterygoid; dentaries: medially curved anteriorly; dorsal surface with 35–36 subequal, slightly curved, rear facing teeth, decreasing in size posteriorly; lateral face convex with a mental foramen medially on one side and ventrally on the other; posterior to this foramen, a bifurcation of dorsal and ventral processes laid over the compound bones in anterior part, with dorsal process longer than ventral; again, dorsal process bifurcates a short medial process, with presence of dentition only in the longer process; ventral process contacts splenial and angular, in addition to compound bone; Meckelian fossa is delimited by the dentary and splenial; splenials: elongated, tapered anteriorly, in the region of contact with dentary; posterior part in contact with anterior region of angular; anterior mylohyoid foramen situated below dorsal extension; angulars: elongated, tapered posteriorly, contacting compound bone laterally, and dentary and splenial anteroventrally; posterior mylohyoid foramen near suture with splenial; in ventral view, angular˗splenial joint visible on one side; compound bones: elongated, approximately two-thirds length of mandible; in lateral view, tapers anteriorly; in contact with dentary posteriorly; presence of a foramen laterally to the posterior tip of angular; prearticular crest prominent, distinctly higher than surangular crest; a rounded depression where it articulates with the quadrate; retroarticular process medially directed.

The largest specimen was a male CHUFC 2626 (TL = 991 mm, SVL = 639 mm, CL = 352 mm); the largest female was CHUFC 3305 (TL = 951 mm, SVL = 604 mm, CL = 347 mm); tail 50–57% SVL (53 ± 2, 13) in females, 54–56% SVL (55 ± 0.7, 6) in males; ventrals 154–162 (156.7 [155.9, 157.4] ± 2.2, 34) in females, 149–159 (153.6 [152.9, 154.7] ± 2.1, 27) in males; subcaudals 124–135 (129.3 [127.7, 130.9] ± 2.7, 13) in females, 132–138 (133.6 [131.3, 136.0] ± 2.2, 6) in males; cloacal plate divided and 12/12/10 dorsal scale rows in both sexes (n = 59, 100% of the sample); two postoculars (n = 53, 91%; one postocular: n = 3, asymmetric variants with 1/2 postoculars: n = 2); nine supralabials (n = 52, 88%; eight supralabials: n = 3, asymmetric variants with supralabials 9/8 or 10/9: n = 4); infralabials 10 (n = 34, 59%; infralabials 9: n = 5, infralabials 11: n = 2; asymmetric variants with infralabials 9/10 or 11/10: n = 17, 29%). Additional meristic and morphometric variation of characters for Chironius dracomaris are in Table 1.

The specific epithet dracomaris is the conjunction of two nouns “draco” (nominative) and “maris” (genitive), used in apposition with the Latinized nickname “Dragão do Mar” (= Dragon of the Sea, in English), as Francisco José do Nascimento (1839–1914) became historically known. He was a popular leader of the harbor pilots in Ceará, who became a symbol of Northeastern resistance against slavery in Brazil. In 1881, “Dragão do Mar” led one of the main port stoppage movements, refusing to transport slaves to the ships, thus preventing interprovincial trafficking. The successive closures of the port accelerated abolitionism in the region, which made Ceará the first Brazilian province to banish slavery, on March 25, 1884, four years before the signing of the Lei Aurea (Morel 1967). The recent worldwide manifestations (Black Lives Matter movement) are proof that we need to change and repair social and historical injustices (see Subbaraman 2020). The fight against modern slavery and structural racism still permeates in Brazil. For example, in the city where “Dragão do Mar” was born (Aracati, Ceará), there are social-environmental conflicts over the traditional use of the territory, as well as in several other areas (Nascimento 2018; Quilombola community of Cumbe). In 2019, the winning Samba of Rio de Janeiro’s Carnival—História Para Ninar Gente Grande from the school Estação Primeira de Mangueira—honored “Dragão do Mar”, as well as other symbols of black and peripheral resistance against exploitation in Brazil, for example the councilor Marielle Franco, who was brutally murdered by the Rio de Janeiro militia on March 14, 2018. We dedicate this species to Francisco José do Nascimento “Dragão do Mar” and these leaders who inspire the daily struggle of restoring a democratic environment in Brazil.

Based on the current evidence, Chironius dracomaris is restricted to the “Brejo de altitude” from Baturité Massif (known records in the municipalities of Baturité, Guaramiranga, and Pacoti), enclaves of remaining rainforests in the dry Caatinga domain of northeastern Brazil, state of Ceará, between 500–800 m a.s.l..

Loebmann and Haddad (2010) recorded a specimen tentatively identified as Chironius bicarinatus (IBSP 77076) from the Ibiapaba Plateau, the westernmost rainforest fragments of the “Brejo de Altitude” in the state of Ceará. Unfortunately, the voucher was destroyed in a fire on May 15, 2010 (Franco 2012), and it was therefore, not possible to check the accuracy of its identification and thus confirm the occurrence of C. dracomaris also in the Ibiapaba Plateau.