Chironius bicarinatus (Wied, 1820)
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https://dx.doi.org/10.3897/vz.74.e106238 |
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publication LSID |
lsid:zoobank.org:pub:D576F215-864F-4961-BA1E-01824BB54B36 |
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persistent identifier |
https://treatment.plazi.org/id/37172144-230E-53B5-8F7D-FB44D92587C0 |
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scientific name |
Chironius bicarinatus (Wied, 1820) |
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Chironius bicarinatus (Wied, 1820) View in CoL
Figures 6A, B View Figure 6 , 7A View Figure 7 , 8 View Figure 8
Chresonymy.
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)
Holotype.
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).
Diagnosis.
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.
Comparisons.
Chironius bicarinatus differs from most congeners, except for C. multiventris Schmidt & Walker, 1943, C. foveatus , C. septentrionalis Dixon 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).
Color pattern variation in preservative.
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.
Color pattern while alive (Fig. 6A, B).
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.
Hemipenial morphology (Fig. 7A).
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.
Distribution (Fig. 8).
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..
Remarks.
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.
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