Research Article |
Corresponding author: Vinícius Sudré ( viniciussudre@gmail.com ) Academic editor: Uwe Fritz
© 2024 Vinícius Sudré, Albedi Andrade-Junior, Manuella Folly, Josué A. R. Azevedo, Robson Waldemar Ávila, Felipe Franco Curcio, Pedro M. Sales Nunes, Paulo Passos.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Sudré V, Andrade-Junior A, Folly M, Azevedo JAR, Ávila RW, Curcio FF, Nunes PMS, Passos P (2024) Revision of the Chironius bicarinatus complex (Serpentes: Colubridae): Redefined species boundaries and description of a new species. Vertebrate Zoology 74: 85-120. https://doi.org/10.3897/vz.74.e106238
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Abstract
Currently, the proposed diagnoses for the Chironius bicarinatus complex reflect a wide variation in color pattern and pholidosis. Herein, we review the Chironius bicarinatus complex based on morphological and molecular data from a sample of 485 specimens covering the species distribution. Our results corroborate the recognition of C. bicarinatus and C. gouveai, and diagnose a distinct lineage without an available name. Thus, here we describe this new species restricted to the Baturité Massif, a relictual rainforest isolated in the Caatinga xerophytic domain, in the state of Ceará, northeastern Brazil. The new species can be distinguished from its congeners by its unique combination of qualitative and quantitative morphological characters (scale counts, morphometric, color pattern), and is also supported by molecular and ecological evidence. Additionally, we rectify data on the distribution and morphological variability of C. gouveai to accurately infer the boundaries between this taxon and C. bicarinatus, which was not properly addressed. Finally, we discuss our results in the light of previous studies that suggest diversification hypotheses in the Atlantic Forest already detected for other taxa, highlighting the importance of conserving the areas of “Brejos de Altitude”, in northeastern Brazil, and the southern limit of Serra do Mar up to Serra do Tabuleiro, in southern Brazil.
Brejos de Altitude, ecological niche modeling, geographical variation, hemipenial morphology, integrative taxonomy, molecular phylogeny, osteology, species delimitation
The snake genus Chironius Fitzinger, 1826 currently comprises 23 species of mostly terrestrial and semi-arboreal colubrid snakes that are widespread across Central and South America, ranging from northern Honduras to northeastern Argentina and northwestern Uruguay (
Chironius bicarinatus is widely distributed throughout the Atlantic Forest and northern Pampas, from northeastern to southern regions of Brazil, northeastern Argentina, eastern Paraguay, as well as some records in northwestern Uruguay; inhabiting the coastal tropical forests, semideciduous forests, grasslands and the Araucaria Forest formations (
Currently, the proposed diagnoses for Chironius bicarinatus reflect a wide variability in color pattern and pholidosis (
We examined 485 specimens from 227 localities currently attributable to the Chironius bicarinatus complex (C. bicarinatus, C. gouveai, and Baturité Massif sample) housed in 35 scientific collections covering the species’ distribution to assess the variability in morphological characters (see Appendix 1). The comparisons supporting our taxonomic decisions are based mainly on the examined specimens, but also on the original descriptions of all valid congeners, including information on the holotype of C. gouveai (
We retrieved the geographic coordinates (datum WGS84) based on institutional catalogs or databases (Appendix 1) and, whenever possible, they were refined with the aid of Gazetteers (e.g.,
The meristic characters mostly follow those used by
The morphometric characters used in this study were: head height (at highest point), head width (at widest point), head length (from snout tip to quadrate mandibular articulation), orbit diameter (on right side only), nostril-orbit distance, snout length (from snout tip to anterior border of right orbit), distance between nostrils, and snout width (at loreals level). All of the aforementioned characters were measured with a dial caliper to the nearest 0.01 mm, except for snout–vent length (SVL) and caudal length (CL) measured using a tapeline to the nearest 1.0 mm. Sex was determined based on the presence/absence of hemipenes. When the organs were not evident, we performed a small incision on the midventral surface of the tail (
Hemipenes preparations followed a combination of techniques proposed by
Herein, the term “species” refers to separately evolving metapopulation lineages (sensu
The delimitation of operational taxonomic units (a definition used prior to data analysis for ordering groups that share a given set of observed characters;
Chironius bicarinatus.—Comprised specimens from coastal forests from the south of the São Francisco River (in the state of Sergipe, northeastern region of Brazil) to the Serra do Tabuleiro (in the state of Santa Catarina, southern region of Brazil).
Chironius gouveai.—Contained specimens from inland Serra do Mar at higher elevations in Pampas, Mixed and Semideciduous Forests, below the Paranapanema River and bounded to the west by the Paraná River.
Baturité Massif sample.—Included specimens restricted to the “Brejo de Altitude” of the Baturité Massif (state of Ceará, northeastern Brazil), above the São Francisco River.
Statistical tests were performed based on meristic and morphometric characters to assess sexual dimorphism (ANOVA test) and other possible differences between operational taxonomic groups (Tukey HSD test). We used Shapiro-Wilk and Levene tests to assess assumptions of normality and homoscedasticity, respectively, for the original variables. Confirming these assumptions (p > 0.05), sexual dimorphism was evaluated using an ANOVA test, applied individually to each operational taxonomic group. In the case of sexual dimorphism, males and females were treated separately in subsequent statistical tests. Then, we applied the Tukey HSD test to report differences between the groups, comparing distinct groups and we posteriorly evaluated which pairs of groups showed differences. When the tests refuted assumptions of normality and/or homoscedasticity, we employed nonparametric procedures to compare means (Mann-Whitney U, Kruskal-Wallis, Games-Howell) (
In order to avoid analytical noise due to ontogenetic allometry, the analyses involving morphometric characters only included supposedly mature specimens. We established the maturity cut-off based on an ongoing reproductive study of the Chironius bicarinatus complex (G.S. Araújo and S. Almeida-Santos, pers. comm. on August 16, 2022), where the size of the smallest mature individual was 580 mm SVL for males and 630 mm SVL for females considering both, C. bicarinatus and C. gouveai. As the specimens restricted to Baturité Massif are significantly smaller in body size, regarding the first two species, and since we aimed to reach a reasonable maturity cut-off for this sample, we opted to follow the results presented in
Based on the results of the variance analyses, we performed a Discriminant Function Analysis (DFA) using a subset of specimens containing no missing data for the following 11 log-transformed exploratory variables:
,ventral (VEN),
,maxillary teeth (MT),
,snout-vent length (SVL),
,head height (HH),
,head width (HW),
,head length (WL),
,orbit diameter (OD),
,nostril-orbit distance (NOD),
,snout length (SL),
,distance between nostrils (DN), and
,snout width (SW). Missing values were only replaced with group mean for
,maxillary teeth (MT). These variables were selected according to their distribution identified during data collection, using those whose variation proved to be potentially informative for comparisons between the groups. Although
,subcaudal (SUB) and
,caudal length (CL) proved to be potentially informative variables for discrimination, they were not incorporated into the multivariate analyses because of the limited number of specimens that still had their entire tail due to the high proportion of excised tails (see
Aiming to assess the phylogenetic relationships within the Chironius bicarinatus complex and the phylogenetic position of Baturité Massif sample within the genus, we included all representatives of the genus Chironius currently available on GenBank and representatives of the eight other Colubridae genera (Dendrophidion Fitzinger, 1843, Drymarchon Fitzinger, 1843, Drymobius Fitzinger, 1843, Drymoluber Amaral, 1930, Leptophis Bell, 1825, Mastigodryas Amaral, 1934, Oxybelis Wagler, 1830, and Spilotes Wagler, 1830). The tree was rooted with Dipsas catesbyi (Sentzen, 1796). We selected specific outgroup terminals in order to maximize character coverage (i.e., homologous sequences available from GenBank) and phylogenetic structure according to the trees of the four most densely sampled Chironius phylogenies (
We generated new DNA sequences for species of the Chironius bicarinatus complex, including three mitochondrial gene segments (12S rRNA, 16S rRNA, ND4) and one nuclear gene segment (c-mos). In total, 12S rRNA, 16S rRNA and c-mos sequences were generated for nine specimens of C. bicarinatus, three of C. gouveai, and four of Baturité Massif sample, while ND4 sequences were generated for two C. bicarinatus specimens and two specimens from the Baturité Massif sample. Localities and voucher information are provided in Appendix 3. We performed PCRs using a PCR Master Mix and a pair of primers for each segment (Appendix 4). Thermocycling for DNA amplification for the first partition is provided in Appendix 4. The size and quality of the resulting PCR products were confirmed by electrophoresis through a 1% agarose gel, stained and visualized under a UV Image capture and analysis system. PCR products were purified and sent to the Centro de Estudos do Genoma Humano e Células-Tronco from Universidade de São Paulo and Rede de Plataformas Tecnológicas da Fundação Oswaldo Cruz, both in Brazil. The resulting electropherograms for both DNA strands were analyzed using CHROMAS LITE 2.01 (Technelysium Pty Ltd), edited using MEGA X (
We performed a partitioned Bayesian Inference (BI) using MrBayes 3.2.2 (
We generated model projections for Chironius bicarinatus and C. gouveai to predict species distribution over time, in addition to testing the degree of niche overlap in the environmental space for each pair of species of the C. bicarinatus complex. We downloaded 19 bioclimatic variables for the current climate from the CHELSA database (
We used the ENMeval R package (
We used the ecospat R package and the functions niche.overlap, niche.equivalency.test, niche.similarity.test for measuring and testing niche overlap between species (
For the Chironius bicarinatus complex, 48 new sequences for 16 specimens were generated, with 15 sequences for each 12S and 16S fragment, 14 for c-mos and 4 for ND4 (see Appendix 3). The total aligned length of the dataset was 2,166 base pairs (bp). We retrieved a tree topology based on BI recovering at least twelve species within Chironius (C. bicarinatus complex, C. brazili, C. flavolineatus, C. multiventris, C. exoletus, C. flavopictus, C. monticola, C. laevicollis, C. scurrulus, C. fuscus, C. grandisquamis and C. challenger) as monophyletic (pp = 1). Additionally, we recovered Baturité Massif sample, nested within the Chironius bicarinatus clade, strongly supported (pp = 1) as the sister-group of the clade C. bicarinatus + C. gouveai (Fig.
Phylogenetic relationships of the Chironius bicarinatus complex estimated under Bayesian Inference based on four molecular markers (12S, 16S, ND4, c-mos) concatenated from a final matrix of 2,166 bp. Only posterior probabilities above 0.95 are shown for the sake of clarity as black squares at nodes. Chironius bicarinatus: blue; C. gouveai: purple; Chironius sp. nov. (= Baturité Massif sample): orange. The detailed phylogenetic tree is provided as Supplementary Material (Fig. S1). Photos by S. Marques-Souza (C. bicarinatus), M. Borges-Martins (C. gouveai), and J.A. Oliveira (Chironius sp. nov.).
Table
Comparisons of quantitative characters between the three determined groups of the Chironius bicarinatus complex. Descriptive data reflect “minimum–maximum ([95% confidence intervals] ± SD, n = sample size)”. Abbreviations: ventrals (VEN), subcaudals (SUB), maxillary teeth (MT), snout-vent length (SVL), caudal length (CL), head height (HH), head width (HW), head length (HL), orbit diameter (OD), nostril-orbit distance (NOD), snout length (SL), distance between nostrils (DN), and snout width (SW).
Females | Males | |||||
C. bicarinatus | C. gouveai | Baturité Massif sample | C. bicarinatus | C. gouveai | Baturité Massif sample | |
VEN | 147–170 (158.0 [157.0, 159.0] ± 5.0, 103) |
156–174 (163.8 [162.8, 164.8] ± 3.7, 60) |
154–162 (156.7 [155.9, 157.4] ± 2.2, 34) |
145–165 (155.8 [155.1, 156.6] ± 4.5, 130) |
151–167 (158.6 [157.9, 159.3] ± 3.3, 80) |
149–159 (153.6 [152.9, 154.7] ± 2.1, 27) |
SUB | 130–157 (140.4 [137.8, 142.9] ± 6.8, 30) |
139–146 (141.8 [140.2, 143.4] ± 2.2, 10) |
124–135 (129.3 [127.7, 130.9] ± 2.7, 14) |
125–154 (140.3 [138.1, 142.6] ± 7.6, 45) |
131–152 (141.2 [139.1, 143.4] ± 5.0, 23) |
132–138 (133.6 [131.3, 136.0] ± 2.2, 6) |
MT | 31–38 (34.3 [33.8, 34.8] ± 1.7, 45) |
28–36 (31.8 [31.0, 32.6] ± 1.9, 25) |
35–39 (36.0 [35.4, 36.6] ± 1.3, 21) |
30–37 (33.9 [33.6, 34.3] ± 1.5, 63) |
27–34 (30.4 [29.9, 30.9] ± 1.5, 39) |
34–36 (35.1 [34.8, 35.4] ± 0.5, 16) |
SVL | 632.0–1170.0 (789.4 [758.6, 820.2] ± 112.8, 54) |
662.0–955.0 (797.6 [775.5, 819.7] ± 66.3, 37) |
460.0–658.0 (566.0 [548.5, 584.2] ± 47.7, 29) |
585.0–1162.0 (849.9 [821.9, 878.0] ± 135.5, 92) |
606.0–1010.0 (774.9 [747.2, 802.6] ± 102.5, 55) |
470.0–739.0 (593.7 [552.8, 634.5] ± 84.7, 19) |
CL | 350.0–610.0 (440.1 [405.0, 475.1] ± 65.7, 16) |
430.0–525.0 (472.5 [439.8, 505.2] ± 31.2, 6) |
272.0–347.0 (301.9 [287.3, 316.5] ± 24.1, 13) |
350.0–640.0 (459.9 [430.4, 489.5] ± 81.9, 32) |
388.0–535.0 (465.3 [443.3, 487.3] ± 41.2, 16) |
260.0–352.0 (310.6 [275.9, 345.4] ± 33.1, 6) |
HH | 7.6–13.5 (10.2 [9.5, 10.9] ± 1.5, 23) |
8.0–12.7 (10.2 [9.6, 10.8] ± 1.3, 21) |
6.3–8.4 (7.4 [7.0, 7.8] ± 0.5, 11) |
8.1–14.2 (10.9 [10.4, 11.4] ± 1.7, 44) |
7.1–13.1 (10.2 [9.6, 10.8] ± 1.5, 26) |
6.3–9.1 (7.9 [7.1, 8.8] ± 0.9, 7) |
HW | 9.3–16.9 (12.7 [12.1, 13.5] ± 1.6, 23) |
10.8–15.1 (13.0 [12.5, 13.5] ± 1.2, 21) |
8.0–10.3 (9.3 [8.7, 9.8] ± 0.8, 11) |
9.7–18.7 (13.7 [13.0, 14.4] ± 2.3, 44) |
9.4–16.2 (12.9 [12.1, 13.6] ± 1.8, 26) |
8.6–10.9 (10.0 [9.3, 10.6] ± 0.7, 7) |
HL | 19.8–30.3 (23.4 [22.3, 24.6] ± 2.6, 23) |
19.0–27.6 (23.6 [22.8, 24.5] ± 1.8, 21) |
17.3–20.8 (18.7 [17.9, 19.5] ± 1.2, 11) |
19.6–28.8 (24.5 [23.6, 25.4] ± 2.8, 44) |
17.7–28.4 (23.4 [22.3, 24.5] ± 2.7, 26) |
16.4–20.4 (19.3 [17.9, 20.6] ± 1.4, 7) |
OD | 5.4–8.3 (6.4 [6.1, 6.7] ± 0.7, 23) |
5.7–7.8 (6.6 [6.4, 6.8] ± 0.5, 21) |
4.6–6.0 (5.2 [4.9, 5.4] ± 0.3, 11) |
5.6–8.2 (6.7 [6.5, 6.9] ± 0.7, 44) |
5.4–7.7 (6.5 [6.3, 6.8] ± 0.6, 26) |
5.0–6.3 (5.7 [5.3, 6.1] ± 0.4, 7) |
NOD | 4.1–6.2 (4.9 [4.7, 5.2] ± 0.5, 23) |
3.7–6.1 (4.8 [4.5, 5.1] ± 0.6, 21) |
3.6–4.5 (4.1 [3.9, 4.3] ± 0.3, 11) |
4.1–6.6 (5.3 [5.1, 5.5] ± 0.6, 44) |
3.2–6.2 (4.8 [4.5, 5.1] ± 0.7, 26) |
3.6–4.5 (4.0 [3.7, 4.4] ± 0.3, 7) |
SL | 7.1–11.6 (8.9 [8.4, 9.4] ± 1.2, 23) |
6.8–11.1 (9.0 [8.6, 9.4] ± 0.9, 21) |
6.1–7.8 (6.9 [6.5, 7.2] ± 0.5, 11) |
7.2–11.8 (9.5 [9.2, 9.9] ± 1.3, 44) |
5.9–11.1 (9.1 [8.6, 9.7] ± 1.3, 26) |
6.1–7.7 (7.1 [6.6, 7.6] ± 0.5, 7) |
DN | 4.5–6.6 (5.3 [5.1, 5.5] ± 0.5, 23) |
3.8–6.7 (5.4 [5.1, 5.8] ± 0.8, 21) |
3.6–4.8 (4.2 [4.0, 4.4] ± 0.3, 11) |
4.2–7.4 (5.7 [5.5, 6.0] ± 0.8, 44) |
4.1–7.0 (5.6 [5.3, 5.9] ± 0.8, 26) |
3.5–5.3 (4.5 [4.0, 5.0] ± 0.6, 7) |
SW | 6.0–10.2 (8.3 [7.9, 8.7] ± 1.0, 23) |
6.6–10.1 (8.5 [8.1, 9.0] ± 0.9, 21) |
5.3–7.0 (6.1 [5.8, 6.5] ± 0.5, 11) |
5.6–11.3 (8.9 [8.5, 9.3] ± 1.4, 44) |
6.2–10.7 (8.6 [8.2, 9.1] ± 1.2, 26) |
5.5–7.3 (6.7 [5.9, 7.4] ± 0.8, 7) |
Differences for females and males from the three determined groups of the Chironius bicarinatus complex (Group 1: C. bicarinatus, Group 2: C. gouveai, Group 3: Baturité Massif sample) for ventral (VEN) and subcaudal (SUB) counts, caudal length/total length ratio (CL/TL) and number of maxillary teeth (MT).
Variable | Group | Significance | Variable | Group | Significance | ||||
VEN | Females | Males | SUB | Females | Males | ||||
1 | 2 | < 0.0001 | < 0.02 | 1 | 2 | < 0.01 | |||
1 | 3 | < 0.0001 | < 0.0001 | 1 | 3 | < 0.0001 | < 0.0001 | ||
2 | 3 | < 0.0001 | < 0.0001 | 2 | 3 | < 0.0001 | < 0.0001 | ||
CL/TL | MT | Females and Males | |||||||
1 | 2 | 1 | 2 | < 0.0001 | |||||
1 | 3 | < 0.0001 | < 0.0001 | 1 | 3 | < 0.0001 | |||
2 | 3 | < 0.0001 | < 0.0001 | 2 | 3 | < 0.0001 |
The DFA variables showed statistical significance in group discrimination (Fig.
Values (%) of the correct reclassification rate and cross validation analysis (in parentheses) for females and males from the three determined groups of the Chironius bicarinatus complex (Group 1: C. bicarinatus, Group 2: C. gouveai, Group 3: Baturité Massif sample).
Predicted Group Membership | |||||
Group | 1 | 2 | 3 | ||
Females | % | 1 | 82.6 (65.2) | 13.0 (21.7) | 4.3 (13.0) |
2 | 33.3 (38.1) | 66.7 (61.9) | 0.0 (0.0) | ||
3 | 0.0 (9.1) | 0.0 (0.0) | 100 (90.9) | ||
Males | % | 1 | 95.5 (93.2) | 4.5 (4.5) | 0.0 (2.3) |
2 | 11.5 (11.5) | 88.5 (88.5) | 0.0 (0.0) | ||
3 | 14.3 (14.3) | 0.0 (0.0) | 85.7 (85.7) |
We performed cumulative frequency analyses between the groups with respect to the temporal formula, number of keeled dorsal rows, presence of apical pits along the body and supralabials contacting orbit. For the temporal formula, we observed a higher frequency of temporals 1+1 in Chironius gouveai (n = 93, 62%), and temporals 1+2 in Baturité Massif sample (n = 48, 69%) and C. bicarinatus (n = 167, 66%). Regarding the number of keeled dorsal rows, in C. bicarinatus and C. gouveai the keels are usually restricted to two dorsal scale rows (n = 211 and 137, 92% and 100%, respectively), while Baturité Massif sample had two (n = 38, 67%) or more (n = 19, 33%) dorsal keeled rows (2nd–11th dorsal rows). Regarding the presence of apical pits along the body, C. gouveai only presents this feature on the neck (n = 125, 98%), while Baturité Massif sample has a higher frequency on the neck and in at least one other region of the body (n = 54, 98%). On the other hand, C. bicarinatus shows closer frequencies, with apical pits only observed on the neck (n = 99, 45%) or on the neck, “paravertebrals”, and tail (n = 116, 52%). Finally, we observed a higher frequency of three supralabials in contact with the orbit in C. bicarinatus (n = 220, 96%) and C. gouveai (n = 136, 96%), while Baturité Massif sample had three (n = 40, 62%) or two (n = 26, 38%) supralabials contacting the orbit.
For skull analyses, we used four specimens that were previously dry prepared (two of Chironius bicarinatus and two of C. gouveai) and three scanned specimens representing each of the groups (Fig.
Micro-computed tomography images of the skull for the groups of the Chironius bicarinatus complex. Dorsal, lateral, and ventral views of the skulls (A–I) followed by the respective cutaway views (J–R). Chironius bicarinatus: A–C, J–L; C. gouveai: D–F, M–O; and Baturité Massif sample: G–I, P–R. Scale bar = 5 mm. Abbreviations: AN, angular; BO, basioccipital; CB, compound bone; DE, dentary; ECP, ectopterygoid; EO, exoccipital; F, frontal; MA, maxilla; N, nasal; P, parietal; PAL, palatine; PBS, Parabasisphenoid complex; PF, prefrontal; PM, premaxilla; PO, postorbital; PR, prootic; PT, pterygoid; QD, quadrate; SM, septomaxilla; SO, supraoccipital; SP, splenial; ST, supratemporal; VO, vomer.
We found the following differences in the skull comparing Chironius bicarinatus with C. gouveai (in parentheses): ventral surface of the septomaxilla smooth, n = 3
Micro-computed tomography images of the skull showing in detail the diagnostic characters comparing Chironius bicarinatus (A, B) and C. gouveai (C, D): posterior portion of supratemporal (ST) straight (A) and slightly curved (C); ventral surface of the septomaxilla (SM) smooth (B) and with the presence of a conspicuous projection (D); anteroventral surface of prefrontal lacrimal foramen (PF) smooth (B) and with the presence of a conspicuous projection (D). Scale bar = 5 mm.
We did not find differences between the skulls of Chironius bicarinatus and Baturité Massif sample. On the other hand, we found four differences comparing Baturité Massif sample with C. gouveai (in parentheses): ventral surface of the septomaxilla smooth (vs. presence of a conspicuous projection); anteroventral surface of prefrontal lacrimal foramen smooth (vs. presence of a conspicuous projection); posterior end of supratemporals straight (vs. slightly laterally curved); and palatine teeth 24 (vs. 16–18).
The model selection of the Maxent parameters for Chironius bicarinatus provided three models with delta-AICc lower than 10 (Table S3). The averaged model presented an AUC = 0.976 and TSS = 0.85, indicating excellent performance. Areas of high suitability for the current climate closely matched the presence records across lowland Atlantic Forest in the Ombrophilous Dense Forests of southern Bahia and Espírito Santo, Rio de Janeiro and São Paulo States. Model projection to the Last Glacial Maximum showed a potential retraction of suitable areas along the coast of southeastern Brazil and a potential expansion of suitable areas across central regions of Bahia and Pernambuco States. Model projection to the Last Interglacial showed a potential retraction of suitable areas across central regions of Bahia and Pernambuco and a potential expansion of suitable areas along the coast of southern Bahia, Espírito Santo, Rio de Janeiro, São Paulo and Paraná States, as well as small areas of the northeastern Brazilian coast (Fig.
For Chironius gouveai, we obtained four models with delta-AICc lower than 10 (Table S5). The averaged model had AUC = 0.950 and TSS = 0.801, also indicating excellent performance of the modeling procedure. Areas of high suitability in the current climate closely matched the presence records across inland Atlantic Forest in the Mixed Forests of central Paraná and Santa Catarina, and northern Rio Grande do Sul States. Model projection to the Last Glacial Maximum showed practically the same potential distribution and suitable areas in the current climate. Model projection to the Last Interglacial only showed a potential expansion of suitable areas across small areas along São Paulo coast (Fig.
Niche overlap was low or zero between all pairs of groups (D < 0.08) and the null tests showed nonequivalence or niche similarity, indicating that all three species occupy significantly distinctive environmental niches across the exact species occurrences, as well as their respective ranges (Table
Results of niche overlap (D metric) and null tests of equivalence and similarity. The niche overlap was low or zero for all comparisons, and the null tests showed nonequivalence or similarity of the niches.
Species Pair | D metric | Equivalance | Similarity 1-2 | Similarity 2-1 |
C. bicarinatus – C. gouveai | 0.083 | 1 | 0.33 | 0.32 |
C. bicarinatus – Baturité Massif sample | 0 | 1 | 0.55 | 0.51 |
Baturité Massif sample – C. gouveai | 0 | 1 | 0.46 | 0.50 |
The data gathered from a geographically representative sample covering most of the variability in the traditional external morphological characters of the Chironius bicarinatus complex, in addition to the clades retrieved in molecular phylogeny and unique niches found by ecological evidence, make it possible to recognize and objectively attribute, two species with available names (C. bicarinatus and C. gouveai), and diagnose a distinct lineage without an available name (Baturité Massif sample). Herein, we first redefined C. bicarinatus, inferring its morphological limits with C. gouveai and then, we formally describe the Baturité Massif sample as a new species.
Coluber bicarinatus
Wied, 1820: 179;
Natrix bicarinatus
–
Erpetodryas bicarinatus
–
Herpetodryas bicarinatus
–
Herpetodryas bicarinata
–
Herpetodryas carinatus
(not Linnaeus, 1758) –
Herpetodryas carinatus var. bicarinata
–
Chironius carinatus
(not Linnaeus, 1758) –
Chironius bicarinatus
–
Adult male, apparently lost in the American Museum of Natural History (
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. 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
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 (
The description of color pattern while alive is based on photographs of six adult specimens (
General view while alive of Chironius bicarinatus and Chironius gouveai: A an adult of C. bicarinatus (
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
Hemipenial morphology of Chironius bicarinatus and Chironius gouveai: A asulcate (left) and sulcate (right) views of the hemipenis of C. bicarinatus (
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..
Distribution of the Chironius bicarinatus complex (A), based on first-hand examined and photographic records with locality data: C. bicarinatus: blue circles; C. gouveai: purple circles; C. dracomaris sp. nov.: orange circles. The stars represent their respective type localities; B zoomed map of the Baturité Massif, an area of distribution of Chironius dracomaris sp. nov.; B, C zoomed maps of molecular sampling localities, with the new sequences obtained in this study (highlighted in red) and sequences selected from GenBank.
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 (
Chironius bicarinatus
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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 (
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 (
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
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 (
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
Chironius carinatus carinatus
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Chironius bicarinatus
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Adult male,
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,
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 (2nd–11th 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.
Color pattern of subcaudal scales comparing (A) Chironius dracomaris sp. nov. (
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.
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 (6th, 7th) with low intensity on neck region and remnants of keeled scales (2nd–11th dorsal rows), which increase in intensity towards midbody; in the midbody, all scales (2nd–11th dorsal rows) have a strong keel intensity; in the posterior region up to the cloaca, there are remnants of keeled scales (1st, 12th dorsal rows), some weak keeled scales (2nd–9th dorsal rows), and the paravertebral rows (6th, 7th) 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.
Dorsal and ventral views of the whole specimen (A); detailed dorsal, ventral (B), and lateral (C) views of head of the holotype of Chironius dracomaris sp. nov. (
Uniform grayish olive dorsum with a light vertebral stripe and two black dorsolateral stripes on each side visible from neck to midbody (until the 75th 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
General view while alive of Chironius dracomaris sp. nov.: A, B a specimen (IBSP 76994 or 76995) from Sítio Álvaro, municipality of Guaramiranga, state of Ceará, Brazil. These two vouchers were destroyed in a fire on May 15, 2010, leaving only photographic records of one of the specimens while alive; C–F paratypes of Chironius dracomaris sp. nov. (
Based on the fully everted and maximally expanded left organ of the specimens
Asulcate (above) and sulcate (below) views of the hemipenis of: A the holotype of Chironius dracomaris sp. nov. (
The description of the skull of Chironius dracomaris is based on a scanned specimen
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
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
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 (
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..
The main taxonomic reviews that have addressed the name Chironius bicarinatus (
Comparisons of the most frequent diagnostic characters (qualitative, osteological) among Chironius bicarinatus, C. gouveai and C. dracomaris sp. nov.
Characters | C. bicarinatus | C. gouveai | C. dracomaris sp. nov. |
Dorsal color pattern | Uniformly green, olive or grayish olive dorsum | Uniformly light brown, grayish olive or olive dorsum with black or brown edge in the scales | Uniform green or olive dorsum with two black dorsolateral stripes |
Belly color pattern | The first third of the belly and subcaudals yellowish; the remainder of the belly whitish yellow | 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; ventrals with black or brown edges | The first third of the belly, near cloacal region and subcaudals whitish; the remainder of the belly olive or greenish |
Subcaudals color pattern | A medially positioned black zig-zag line between subcaudals, gradually fading to the tip of the tail; outer margins with a black outline | Subcaudals with black or brown edges; outer margins with a black outline | Subcaudals with slightly black edges; outer margins without a black outline or a black zig-zag line medially positioned between subcaudals |
Temporals | Usually 1+2 | Usually 1+1 | Usually 1+2 |
Apical pits | Usually only on the neck region of the body | Only on the neck region of the body | On the neck and in at least one other region of the body |
Conspicuous projection on ventral surface of the septomaxilla | Absent | Present | Absent |
Conspicuous projection on anteroventral surface of prefrontal lacrimal foramen | Absent | Present | Absent |
Quadrate-suspensorium articulation with posterior end of supratemporals | Straight | Slightly curved | Straight |
Some information (diagnosis, geographical distribution, and material examined) present in the original description of Chironius gouveai (
Comparisons between character frequencies and specimen identifications in the sample examined by
Character frequencies |
|
This study (n = 434) |
Chironius bicarinatus | ||
Temporals | 1+1 (79%) | 1+2 (66%; n = 167) |
Supralabials | eight (61%) | nine (92%; n = 174) |
Infralabials | eight (72%) | ten (73%; n = 136) |
Dorsal scale rows | 12/12/10 (56%) | 12/12/10 (100%; n = 229) |
Chironius gouveai | ||
Subcaudal range in females | 103–146 | 139–146 (n = 10) |
Infralabials | eight (74.2%) | ten (71%; n = 98) |
Specimen identifications | ||
CHUFC 1389, 2103, 2597, 3249, 3300 | Chironius bicarinatus | Chironius dracomaris sp. nov. |
IBSP 10908, 21568, 64234 | Chironius bicarinatus | Vouchers destroyed in a fire accident that hit the Instituto Butantan on May 15, 2010. Probably not be specimens of C. bicarinatus, as there is no additional voucher for Mato Grosso do Sul State. |
MCP 4134, 4283, 4199, 4244, 17291, MHNCI 1662, 5328, 8428, 10502 | Chironius bicarinatus | Chironius gouveai |
MZUFV 45, 145, 168, 642 | Chironius bicarinatus | Chironius quadricarinatus Boie, 1827 |
UFMG 86 (field number: 1610) | Chironius bicarinatus | Chironius brazili Hamdan & Fernandes, 2015 |
UFPB 77 | Chironius bicarinatus | Leptophis dibernardoi Albuquerque, Santos, Borges-Nojosa & Ávila, 2022 |
MCP 312, 1711, 3724, 15530 | Chironius foveatus | Chironius gouveai |
MHNCI 12369, MCP 2423 | Chironius cf. exoletus | Chironius gouveai |
Regarding the geographical distribution presented by
Many endemic reptile and amphibian species have been described in the “Brejos de Altitude” (i.e., isolated remnants of rainforest restricted to highlands throughout the xerophytic Caatinga domain), mostly from the Baturité Massif in Ceará State (e.g.,
Furthermore, the São Francisco River seems to act as a physical barrier (
The molecular phylogeny recovered Chironius dracomaris sp. nov. as a sister-group of the clade C. bicarinatus + C. gouveai (Fig.
We believe that the continental shelf in the LGM, an area currently submerged along the Brazilian coastline, possibly during periods of climatic oscillations and marine regressions (see Leite et al. 2016), could have sheltered an extensive and suitable area for the Chironius bicarinatus lineage. This hypothesis perhaps made it possible for ancestral populations to expand their distribution vertically to the northern limits of the Atlantic Forest. The projection models support the expansion of suitable areas in the LGM with the distention of the continental shelf, suggesting that previous Holocene events may have favored a bottleneck effect related to the consolidation of the speciation process previously initiated between C. bicarinatus and C. gouveai. On the other hand, although some coastal populations may have speciated prior to the LGM, other snake species likely diverged within the last 11,000 years (see
Similarly, it would also be extremely important to conserve the areas of “Brejos de Altitude” (
We are indebted to all curators, technicians and researchers for allowing access to specimens under their care and the assistance received during the visits to their respective institutions, as well as helping to provide specimen data and loans requested: S. Bogan (CFA), D.M. Borges-Nojosa, C.H. Bezerra (CHUFC), B.M. Sousa, R.H. Carvalho (CHUFJF), D. Matos, R.G. Faria (CHUFS), S. Neckel-Oliveira, S.D. Weihermann-Oliveira (CHUFSC), D.O. Mesquita, F.R. Delfim (CHUFPB), G. Colli, P.P.U. Aquino (CHUNB), S. Kretzschmar (FML), F.C. Resende, G.A. Cotta (FUNED), F.G. Grazziotin, F.L. Franco, L.M. Correa, V.J. Germano (IBSP), M.T. Rodrigues (IB/USP), J. Faivovich, S.J. Nenda (
Figure S1
Data type: .pdf
Explanation note: Phylogenetic relationships of the Chironius bicarinatus complex estimated under Bayesian Inference based on four molecular markers (12S, 16S, ND4, c-mos) concatenated from a final matrix of 2,166 bp.
Table S1
Data type: .xlsx
Explanation note: Genetic differences among and within species of Chironius calculated from the uncorrected pairwise genetic distances (p-distance; %) for sequences of 16S rRNA.
Table S2
Data type: .xlsx
Explanation note: Morphological data of examined specimens of the Chironius bicarinatus complex.
Tables S3–S6
Data type: .docx
Explanation notes: Table S3. Selected models based on delta-AICc lower than 10 for model projection of Chironius bicarinatus and respective parameters: Feature Classes (FC), Regularization Multipliers (RM). — Table S4. Variable importance results for Chironius bicarinatus derived from the MaxEnt model. Notice that we preselected variables with low VIF prior the modeling. — Table S5. Selected models based on delta-AICc lower than 10 for model projection of Chironius gouveai and respective parameters: Feature Classes (FC), Regularization Multipliers (RM). — Table S6. Variable importance results for Chironius gouveai derived from the MaxEnt model. Notice that we preselected variables with low VIF prior the modeling.
Appendix 1
Data type: .pdf
Explanation notes: Examined specimens (n = 949) with their respective localities.
Appendix 2
Data type: .pdf
Explanation note: Photographic material of specimens while alive obtained from iNaturalist observations.
Appendix 3
Data type: .pdf
Explanation notes: GenBank accession numbers of species of Chironius and outgroup taxa included in the molecular analysis. Specimens in bold refer to the new sequences generated in this study.
Appendix 4
Data type: .pdf
Explanation note: Primer sequences and PCR protocols.