Amphibia-Reptilia (2019) DOI:10.1163/15685381-20191279 brill.com/amre The enigmatic Amazonian genus Eutrachelophis: morphological evidence and description of new taxa (Serpentes: Dipsadidae: Xenodontini) Hussam Zaher1,∗ , Ana L.C. Prudente2 Abstract. Eutrachelophis contains two species – Eu. bassleri and Eu. steinbachi – that are known from the lowland rainforests of western Amazonia (Ecuador, Peru, and Bolivia). Due to their unusual hemipenial morphology, they have been considered to belong to a separate tribe – Eutrachelophiini – of dipsadids. Here, we describe a new species of Eutrachelophis that fills an important morphological gap in the hemipenial pattern known for this genus. Although highly modified, apical disks are recognizable in the hemipenes of both species, supporting their inclusion in the tribe Xenodontini. We further allocate Eu. steinbachi in a new genus, due to the contrasting morphological disparities and lack of uniquely derived features shared with the remaining species of Eutrachelophis. The new genus can be distinguished from all other genera of Dipsadidae by the presence of deeply divided lobes with lobular projections that expand beyond the tip of the sulci, the latter ending on the middle surface of the lobes where it opens at the base of a small nude area considered to be the remnant of the Xenodontini apical disks. The two remaining species of Eutrachelophis retain well-developed Xenodontini apical disks that are expanded throughout the lobular region reaching each other’s edges at midline due to the fusion of both lobes in one unique structure. The condition observed in the genus Lygophis is morphologically intermediate between the highly specialized condition present in Eutrachelophis and the one known to characterize other Xenodontini, supporting the allocation of this genus in the tribe. (Zoobank: www.zoobank.org/urn:lsid:zoobank.org:pub:96725BD0-D9E6-4A85-A4BD-D6BF988CFC5E) Keywords: color patterns, head glands, hemipenis, skull, taxonomy. Introduction The Dipsadidae corresponds to the most species-rich snake family known to date. With a widespread distribution in Asia and the Americas, the family reaches its highest diversity in the Neotropical region (Zaher et al., 2018), retaining only relictual lineages in North America and China (He et al., 2009; Wang et al., 2014; Zaher et al., 2019). Dipsadid monophyly is well-documented molecularly (e.g., Zaher et al., 2009; Grazziotin et al., 2012; Pyron et al., 2013; Wang et al., 2014; Zaher et al., 2019), being morphologically supported by two putative hemipenial synapomorphies – body calyces 1 - Museu de Zoologia da Universidade de São Paulo, Avenida Nazaré 481, Ipiranga, São Paulo, CEP 04263-000, São Paulo, Brazil 2 - Museu Paraense Emílio Goeldi, Laboratório de Herpetologia, Avenida Perimetral 1901, CP 399, CEP 66040-170, Belém, Pará, Brazil ∗ Corresponding author; e-mail: hussam.zaher@gmail.com © Koninklijke Brill NV, Leiden, 2019. on the asulcate surface of the lobes and lateral enlarged spines disposed on the sides of the hemipenial body (Zaher, 1999; Zaher et al., 2009). Recently, Myers and McDowell (2014) described the dipsadid tribe Eutrachelophiini and its only genus Eutrachelophis to accommodate two rare species – Eu. bassleri Myers and McDowell, 2014 and Eu. steinbachi (Boulenger, 1905) – known to occur in the lowland rain forests of western (Ecuador, Peru and Bolivia) and eastern Amazonia (Brazil). Myers and McDowell (2014: 42) compared Eu. bassleri and Eu. steinbachi to a number of dipsadids and other colubroidean snakes and concluded that, despite striking differences in hemipenial morphology, great similarity in “external coloration, skull, dentition, head muscles, glands, and visceral anatomy” warranted their allocation in the same genus. In the course of a series of surveys led by our institutions in the Brazilian states of Mato Grosso, Amazonas, and Acre, in the Amazonian DOI:10.1163/15685381-20191279 2 basin, we were able to secure one specimen of Eutrachelophis steinbachi and four specimens representing a new species more closely related to Eu. bassleri. Unfortunately, no tissue samples were available from these specimens, for which there is no molecular data available. However, the available material provided new morphological evidence that allowed us to evaluate their phylogenetic affinities within dipsadids. Here we describe the new species as a member of the genus Eutrachelophis and provide morphological support for the allocation of Eu. steinbachi in a new genus. Furthermore, hemipenial and osteological evidence support their inclusion in the tribe Xenodontini and the synonymy of Eutrachelophiini with the latter. Material and methods We examined specimens housed in the Museu Paraense Emílio Goeldi (MPEG), Belém, Pará, and Museu de Zoologia da Universidade de São Paulo (MZUSP), São Paulo, Brazil (Appendix). Data from additional specimens of Eutrachelophis can be found in Myers and McDowell (2014). Coordinates of localities from the literature or museum databases were obtained using the software Google Earth Pro 7.1.2 (Google, 2018). We constructed maps using QGIS version 2.4 (QGIS Development Team, 2017). We included in the map only geographic records based on specimens with collected vouchers (Myers and McDowell, 2014; Echevarría and Venegas, 2015). Terminology for cephalic shields followed Savage (1960), whereas ventral and subcaudal counts followed Dowling (1951). We retrieved the following meristic data: number of supralabial scales (SL) and number of scales in contact with the orbit (SLo); number of infralabial scales (IL); number of dorsal scales counted in three regions (anterior, middle, and posterior) of the body (DO); number of ventrals (VE) and subcaudals (SC). Morphometric data for the cephalic region were taken with a digital caliper (0.1 mm), while snout-vent length (SVL) and tail length (TL) were taken using a flexible ruler (1.0 mm). We measured the following head parameters: head length and head width; frontal length and width; parietal length and width; prefrontal length and width; internasal height and width; loreal length and height; rostral length and width; ocular diameter; and anterior and posterior chinshield length. Counts, measurements and descriptions of paired cephalic scales were systematically taken on the right side of the head. For the purpose of description, measures were converted to proportions. Images were taken with a digital camera and mounted in plates with the aid of Adobe Photoshop. Head and body color patterns followed Myers and McDowell (2014). The term “ocelli” refers to small (less than H. Zaher, A.L.C. Prudente two scales long and wide) marks throughout the dorsum or venter of the body, and “dot” refers to any mark smaller than a scale. Sex was determined on the basis of presence or absence of hemipenis verified through a ventral incision at the base of the tail. Preserved hemipenes were prepared following Pesantes (1994), observing the precautions highlighted by Zaher and Prudente (2003). Osteological descriptions followed Cundall and Irish (2008) while hemipenial terminology followed Zaher (1999). Observations on head glands and muscles were performed under a stereomicroscope equipped with a camera lucida, after the skin on one side of the head was removed. Terminology of the cephalic glands followed Kochva (1978) and Zaher (1997). CT-scanning procedures were conducted on a 300-kV µ-focus X-ray source micro computed tomography GE Phoenix v|tome|x M 300 (General Electric Measurement & Control Solutions, Wunstorf, Germany) at the Laboratório de Microtomografia of the Museu de Zoologia, Universidade de São Paulo. Scan parameters such as exposure time (ms), number of projections, kilovoltage (kV), and current strength (µA), were set for each individual specimen to obtain the maximized spatial resolution and better image contrast. The duration of the scanning varied according to the configuration chosen for each specimen. X-ray projection images were recorded between 333 to 1000 ms of time of exposure per image, with the images varying from 1000 to 1440 in one slow stepwise rotation of the sample. The tube voltage was set varying from 45 to 80 kV, 150 to 250 µA, and voxel size from 6 to 18 µm. The acquired scan data was processed on a high-end computer HP Z820 workstation with eight-core Intel Xeon E5-2660, 2.20 GHz (2 processors), 128 GB of memory. A Microsoft Windows 7 Ultimate 64 bit operating system was used, with a graphics-processing unit Cubix Elite Xpander (Cubix Corporation, Carson City, NV). Reconstruction of raw data was performed using the systemsupplied software phoenix datos|x reconstruction v. 2.3.0 (General Electric Measurement & Control Solutions, Wunstorf, Germany). Three-dimensional visualization, segmentation, as well as the analysis of the reconstructed data was performed using VGStudio MAX 2.2.3 64 bit (Volume Graphics GmbH, Heidelberg, Germany). Results The genus Eutrachelophis includes two species with very distinct hemipenial patterns – Eu. bassleri with an “unilobed” hemipenis and Eu. steinbachi with a deeply divided one. Despite significant hemipenial differences, Myers and McDowell (2014: 42) considered them to be congeneric due to similarities in their viscera, head glands, head muscles, color pattern, skull, and dentition. However, the authors recognized that these differences may not be so striking The enigmatic Amazonian genus Eutrachelophis and were, in many cases, common to the majority of dipsadids (e.g., absence of hypapophyses on posterior trunk vertebrae, tracheal lung extension confined to the membranous dorsal wall of the trachea, head muscle configuration). We will briefly comment on the morphological characters analyzed by Myers and McDowell (2014) and provide additional evidence based on the material available in our study. Our results strongly support the allocation of these species in the tribe Xenodontini, and we will thus concentrate our comparisons with members of this tribe. Head glands and muscles morphology Among the head glands mentioned by Myers and McDowell (2014), the only uncommon condition observed in both species is the “unusually large temporal extension” of the Harderian gland. The absence of a rictal gland or the presence of well-differentiated supralabial and Duvernoy’s glands are common features within Xenodontini. We analyzed the head glands and adductor muscles of a specimen belonging to the new species of Eutrachelophis described here (MPEG 19550). The Harderian gland is well-developed in this specimen, projecting posteriorly between the profundus and superficialis adductor muscles (sensu Zaher, 1994), as described by Myers and McDowell (2014). However, this condition is also known in Lygophis lineatus (Linnaeus, 1758) and Erythrolamprus aesculapii (Linnaeus, 1758) among Xenodontini, and does not represent a uniquely derived feature of Eutrachelophis (supplementary fig. S1). We failed to find a muscle levator anguli oris and a rictal gland in the specimen dissected (supplementary fig. S1). Only a weak, parallel-fibered adductor superficialis was observed at the level of the rictal corner of the mouth (supplementary fig. S1). Skull osteology Myers and McDowell (2014) suggested that Eutrachelophis bassleri and Eu. steinbachi have 3 virtually identical skulls that differ from the other species they compared with by the presence of “unusually short” supratemporals (their “tabulars”), the presence of venous (?) foramina dorsal to the trigeminal ganglion, and an exceptional pattern of the pituitary vein foramen. According to Myers and McDowell (2014: Figs. 10-11), the pituitary vein foramen lies either between the sphenoid and parietal (Eu. bassleri) or is entirely enclosed in the sphenoid (Eu. steinbachi). Our specimen of Eu. steinbachi conforms with their description while the new species conforms to the condition seen in Eu. bassleri (fig. 1D, H). However, neither conditions seem to be unique to Eutrachelophis and are present in the Xenodontini Lygophis (with a pituitary foramen surrounded by the sphenoid; supplementary fig. S2) and Erythrolamprus (with a pituitary vein clasped by the sphenoid and parietal; supplementary fig. S3). We were unable to locate the venous (?) foramina mentioned by these authors in the specimens analyzed. Our new species presents a short and slender supratemporal, similar to the condition observed by Myers and McDowell (2014) in Eu. bassleri and Eu. steinbachi; likewise, a short supratemporal was also observed in Erythrolamprus pyburni (Markezich and Dixon, 1979) (supplementary fig. S3) and Erythrolamprus atraventer (Dixon and Thomas, 1985) (supplementary fig. S4). All other observed Xenodontini retain a long supratemporal that projects posteriorly from the lateral temporal wall of the braincase. Myers and McDowell (2014) pointed out that the only major difference between the skulls of Eu. bassleri and Eu. steinbachi was that the latter has a dorsal crest of the parasphenoid rostrum that is lacking in the former species. Similarly, our specimen of Eu. steinbachi retains a conspicuous dorsal crest (fig. 1C) of the parasphenoid rostrum while our new species lacks it (fig. 1G). Another previously unnoticed difference between these two species is the position of the mandibular trigeminal foramen with respect to the anterior border of the fenestra ovalis. In Eu. steinbachi, 4 H. Zaher, A.L.C. Prudente Figure 1. Skulls of Baliodryas steinbachi (MZUSP 23115) (A-D), and Eutrachelophis papilio sp. nov. (MZUSP 10530) (E-H), in dorsal (A, E), ventral (B, F), left lateral (C, G), and right lateral (D, H) views. Abbreviations: dc, dorsal crest of the parasphenoid rostrum; pvf, pituitary vein foramen. Arrow points to the anterior portion of the fenestra ovalis overlapping the posterior half of the mandibular trigeminal foramen in Eu. papilio. Scale bar = 1 mm. The enigmatic Amazonian genus Eutrachelophis the mandibular trigeminal foramen lies anteriorly to the fenestra ovalis whereas in Eu. bassleri the anterior portion of the fenestra ovalis overlaps the posterior half of the mandibular trigeminal foramen (see Myers and McDowell, 2014: Fig. 10). Our new species shares with Eu. bassleri the same partial overlap between the fenestra ovalis and the mandibular trigeminal foramen (fig. 1G, H), while the condition in our specimen of Eu. steinbachi conforms to the one illustrated by Myers and McDowell (2014: Fig. 11). A partial overlap between the fenestra ovalis and posterior trigeminal foramen is absent in all other Xenodontini studied (supplementary fig. S2–S4), suggesting that this character is a synapomorphy of Eu. bassleri and the new species described here. Hemipenial morphology According to Myers and McDowell (2014) the hemipenis of Eu. bassleri is unique among dipsadids “in having a spiny noncalyculate hemipenis with a well-formed noncapitate nude capitulum,” while the hemipenial morphology of Eu. steinbachi is more similar to those few endoglyptodont taxa with deeply divided spiny lobes like Xenodon suspectus and other unrelated taxa (e.g., the African Mehelya poensis). Although comparisons with elapoid taxa with superficially similar hemipenial morphologies seemed unnecessary, uncertainties regarding Eu. steinbachi affinities and hemipenial morphology were justified since the authors relied only on retracted organs that were dissected and pinned flat for study. The everted and maximally inflated hemipenis available in our study provided valuable additional information that is not visible in a dissected organ (fig. 2). We therefore provide below a revised description of the hemipenis of Eu. steinbachi, adding the new relevant information not visible to Myers and McDowell (2014). We further compare the similar hemipenial morphologies of Eu. bassleri and the new species. 5 The everted organ of Eu. steinbachi is long, deeply bilobed, with a bifurcated sulcus spermaticus, and only spinules and spines ornamenting it. The lobes are slender, tubular projections that are twice as long as the hemipenial body with tips that are only slightly narrower than the rest of the lobe. As predicted by Myers and McDowell (2014), the base of the organ is ornamented by sparce spinules and a shallow basal naked pocket. We were unable to locate a differentiated smooth terminal basin in the region of the lobular crotch, as suggested by Myers and McDowell (2014). Two rows of laterally enlarged spines are clearly present on both sides of the organ, supporting the allocation of Eu. steinbachi to the Dipsadidae (Zaher, 1999). The rows of lateral enlarged spines start proximally with two very large spines followed by six to seven much smaller, gradually reducing spines disposed on the lateral surface of the organ towards the lobes. The more basal and larger lateral enlarged spines are distantly disposed while the distal ones are more densely arranged. Distally to the more enlarged spines, at the level of the sulcus division, the hemipenial body shows a slight constriction that ressembles a semicalycular condition. The hemipenial body is mostly nude except for the enlarged lateral spines and a few dispersed spinules that tend to concentrate on the lateral border of the sulci. The asulcate surface distal to the slight body constriction and the intrasulcar region on the sulcate side are more densely packed with spinules. The intrasulcar surface bears two rows of enlarged intrasulcar spines with five to six aligned spines. Enlarged intrasulcar rows of spines are known to occur within dipsadids in the tribes Xenodontini, Pseudoboini, Alsophiini, and Tropidodryadini (Zaher, 1999; Zaher et al., 2019). The sulcus spermaticus divides at the proximal third of the hemipenial body, running centrolineally until it reaches the level of the lobular crotch where the branches diverge to take a centrifugal position on the lateral side of the lobes. The branches terminate on a slightly expanded nude and wrinkled area in the middle of the lobes. 6 H. Zaher, A.L.C. Prudente Figure 2. Hemipenis of Eutrachelophis papilio sp. nov. (MPEG 25471) (A-C), and Baliodryas steinbachi (MZUSP 23115) (D-F), in sulcate (A, E), asulcate (B), apical (C), and lateral (D) views. Left lobe of B. steinbachi in close lateral view (F). Scale bar = 1 mm. 7 The enigmatic Amazonian genus Eutrachelophis A slight lobular constriction marks the end of the sulcus spermaticus at the base of the nude area, separating the lobes in two distinct halves in the everted organ. Both halves also bear distinct ornamentations, the distal half being covered with rows of sharp, enlarged and highly mineralized spines that gradually increase in length towards the tip of the lobes, while the proximal half is covered with spinules similar to the ones present in the intrasulcar and distal asulcate regions of the hemipenial body. The distal half of the lobe is thus a sulcusless projection that is not directly involved in sperm transport. The nude area is confined to the distal half of the lobe and is bordered by an expanded tissue fold. The hemipenis of Eu. steinbachi resembles strikingly with the one of Xenodon rabdocephalus illustrated by Zaher (1999: Fig. 82), with the only major difference being the lack of a sulcusless distal projection on the lobes. As in Eu. steinbachi, Xenodon rabdocephalus retains a vestigial nude area surrounded by an expanded fold at the end of the sulcus spermaticus. In both cases, a vestigial apical disk homologous to the one present in other Xenodontini is still recognizable. We suggest here that the small nude area present in the hemipenial lobes of Eu. steinbachi is homologous to the apical disks of the Xenodontini. Similarly, Eu. bassleri and the new species also retain apical disks in their hemipenis (fig. 2). However, differently from Eu. steinbachi, the apical disks remain well-developed on both sides of a single hemipenial lobe. This unusual condition results from the secondary loss of hemipenial bilobation in these two species, and more specifically from the fusion of both lobes into a unilobed condition with the lobular region still corresponding to onethird of the hemipenial length. Both intrasulcar and asulcate surfaces are still present as vestiges of an ancestral bilobed condition of the lobes (fig. 3). The apical disks show an inconspicuous tissue fold surrounding their nude surface. They are mainly laterally oriented on the hemipenial surface and contact each other along the midline of the lobe, being separated only by a vestigial string of lobular tissue. The same vestigial string of tissue that separates the two lobes is visible in the illustration of the hemipenis of Eu. bassleri provided by Myers and McDowell (2014: Fig. 3D). The loss of bilobation in both species resulted in a unique pattern of lobular ornamentation, with the proximal half of the lobe being covered with spinules while the distal half is covered by the two separate apical disks that meet each other on the midline. The sulcar branches run centrifugally on the lobes (fig. 3B, D), ending very close to each other on the distal tip of the lobe, near the distal edge of each apical disk. Although unusual, this sulcar condition also results from the loss of bilobation and can be easily compared to the sulcar condition found in other Xenodontini (fig. 4D, H). Both Eu. bassleri and the new species retain welldeveloped enlarged lateral spines arranged in three to four rows disposed on the lateral sides of the hemipenial body, from the proximal end to the base of the lobe. The rows of enlarged lateral spines meet on the asulcate surface, on the proximal half of the hemipenial body. The distal half of the hemipenial body is covered with spinules that extend onto the asulcate surface of the lobe, reaching the edge of the apical disk distally. Enlarged intrasulcar spines are visible on the intrasulcar surface of both species, being well-developed in Eu. bassleri and vestigial in the new species. The shape of the hemipenial lobe of Eu. bassleri is short and round (Myers and McDowell, 2014: Fig. 3) while in the new species it is long and tapering distally (fig. 3). Systematic account Our reinterpretation of the hemipenial morphology present in the two previously known species of Eutrachelophis and the new species described herein suggest that they belong to the tribe Xenodontini of the Dipsadidae (Zaher et al., 2009, 2019). All three species retain modified apical disks, a synapomorphy of Xenodontini, as small nude areas located in the middle of the lobe of Eu. steinbachi and large nude 8 H. Zaher, A.L.C. Prudente 9 The enigmatic Amazonian genus Eutrachelophis disks covering most of the distal half of the single lobe in Eu. bassleri and the new species. Therefore, we reallocate the genus Eutrachelophis in the tribe Xenodontini, and consider the tribe Eutrachelophiini Myers and McDowell, 2014 as a junior synonym of the latter. Furthermore, the discovery of a new species of Eutrachelophis, morphologically more closely related to Eu. bassleri, provided additional evidence reinforcing the significant morphological differences sustained between Eu. bassleri and Eu. steinbachi. We therefore allocate Eu. steinbachi in a new genus. Family Dipsadidae Bonaparte, 1838 Subfamily Xenodontinae Bonaparte, 1845 Tribe Xenodontini Bonaparte, 1845 Xenodontina Bonaparte, 1845 Eutrachelophiini Myers and McDowell, 2014 Diagnosis. Distinguished from other tribes of the Xenodontinae by the lack of hemipenial calyces and capitular grooves, presence of nude apical disks on the hemipenis, and horizontal neck flattening behavior (Myers, 1986; Zaher et al., 2009). Content. Erythrolamprus Boie, 1826; Lygophis Fitzinger, 1843; Xenodon Boie, 1826; Eutrachelophis Myers and McDowell, 2014; Baliodryas gen. nov. Eutrachelophis Myers and McDowell, 2014 Type species. Eutrachelophis bassleri Myers and McDowell, 2014 Diagnosis. Eutrachelophis can be distinguished from the other genera of Xenodontini by the combination of the following characters: partial overlap between the edges of the fenestra ovalis and mandibular trigeminal foramen on the prootic; 15 dorsal scale rows; less than 150 ventrals; cloacal plate divided; less than 90 subcaudals; unilobed hemipenis with large apical disks contacting each other on the midline; presence of a single expanded ocellus or two pairs of ocelli on the nape behind the parietal scales and a second less defined pair of ocelli on the neck region; presence of a postocular wedge of pale color extending dorsally from the lip; and dorsum with dark stripes or spots anteriorly, becoming nearly uniform posteriorly. Contents. Eutrachelophis papilio sp. nov. and Eutrachelophis bassleri Myers and McDowell, 2014. Eutrachelophis papilio sp. nov. Taeniophallus occipitalis – Avila-Pires et al., 2009 Eutrachelophis undescribed species – Myers and McDowell, 2014 Holotype. MPEG 25471, from Fazenda Scheffer (8°20′ S, 65°43′ W), Ituxi River, Municipality of Labrea, state of Amazonas, Brazil, collected by Teresa Cristina Sauer de AvilaPires on February 14, 1997 (fig. 6) (Zoobank: urn:lsid:zoobank.org:act:D1638968-18994ABD-95AE-3CC79CBB2ECB). Paratypes. MPEG 18250, from Km 2 of BR 3041 (9°45′ S, 67°39′ W), Municipality of Rio Branco, state of Acre, Brazil, collected by Marinus Hoogmoed and Teresa Cristina Sauer Avila-Pires on January 1, 1990. MPEG 19950, Municipality of Careiro da Varzea (3°13′ S, 59°49′ W), state of Amazonas, Brazil, collected by Shawn S. Sartorius on December 22, 1998. MPEG 23862, Municipality of Coari (4°53′ S, 65°21′ W), state of Amazonas, Brazil, collected by Gleomar Maschio and Alessandra Travasso on November 19, 2009. MZUSP 10530, Urucu River (Locality roughly at 05°S, 65°W), state of Amazonas, Brazil, collector and date unknown. Figure 3. Hemipenis of Eutrachelophis papilio sp. nov. (MPEG 25471), sulcate and asulcate sides (A), and apical view (B); Eu. bassleri (modified from Myers and McDowell, 2014: Fig. 3), sulcate and lateral sides (C) and apical view (D); Baliodryas steinbachi (MZUSP 23115), lateral and sulcate sides (E) and distal sulcate view of the lobe (F). Scale bar = 1 mm. Abbreviations: ad, apical disk; as, asulcate side; eis, enlarged intrasulcar spines; is, intrasulcar area; lc, lobular constriction; rc, reduced area of contact between apical disks; ss, sulcus spermaticus. Scale bar = 1 mm. 10 Diagnosis. Eutrachelophis papilio is distinguished from all other species by the following combination of characters: 15-15-15 number of dorsal scale rows; three gular scale rows, wider than long; 8 supralabials, 2-3 contacting loreal and 3-5 in orbit; 9 infralabials, 1–5 contacting anterior chinshields and 5-6 posterior chinshields; 139-145 ventrals; 68-76 subcaudals; conspicuous white butterfly-shaped ocellus on the nape; hemipenis slightly bilobed with apical disks; and 22-25 maxillary teeth subequal in size and recurved, followed by diastema and two ungrooved fangs. Comparisons. Eutrachelophis papilio differs from Eu. bassleri by having a single laterally expanded, butterfly-shaped and black-rimmed white ocellus on the nape (vs. a pair of distinct round-shaped, black-rimmed white ocelli on the neck in Eu. bassleri), a higher number of ventrals (139-145 vs. 128-139 in Eu. bassleri), and a longer hemipenial lobe that tapers distally (rounded distally in Eu. bassleri). Description of the holotype (fig. 5). Adult male, SVL 266 mm, TL 49 mm (incomplete). Head distinct from body (length 11.17 mm, width 3.93 mm). Snout slightly acuminate in lateral view, round in dorsal view. Eye large, ocular diameter (2.54 mm) greater than distance from its anterior edge to nostril. Rostral subtriangular in frontal view (2.51 mm wide, 1.31 mm high), poorly visible in dorsal view. Internasal paired, as wide as long (1.42 mm wide, 1.46 mm high). Prefrontals paired (1.63 mm wide, 1.50 mm long), in contact with nasal, loreal, and preocular. Supraocular sub-trapezoidal, about twice as long as wide. Frontal slightly hexagonal (2.0 mm wide, 3.4 mm long), slightly longer than distance to snout. Parietal longer (4.40 mm) than wide (2.52 mm). Nasal divided. Loreal (0.74 mm long, 1.12 mm high) tipped slightly forward and rectangular. One preocular. Two postoculars, the lower one distinctly smaller than upper. Temporals 1 + 2, the upper one in second row elongated nearly to end of parietal. H. Zaher, A.L.C. Prudente Eight supralabials, 2nd and 3rd touching loreal and 3rd to 5th bordering eye. First three supralabials subequal in height and smaller than fourth, sixth and seventh higher than remaining supralabials. Nine infralabials, 1st to 5th touching anterior chinshields and 5th and 6th contacting posterior chinshields. First pair of infralabials in contact behind symphysial. Anterior chinshields smaller (2.46 mm long) than posterior (3.09 mm long). Inconspicuous tubercles on head plates and chin. Three gular scale rows, wider than long. Three preventrals. Dorsal scales smooth, in 15-15-15 rows. Apical pits more visible on anterior region of body. Ventrals 145. Cloacal plate divided. Subcaudals 28 pairs (incomplete tail). Maxillary teeth (25) subequal in size and recurved, followed by a diastema and two ungrooved fangs. Color pattern of the holotype in preservative (fig. 5). Head and neck brown darker than body, reaching posterior region of parietals. Anterior region of snout paler than posterior cephalic scales and body (rostral and anterior part of nasal white). A single laterally expanded, butterfly-shaped and black-rimmed white ocellus on the nape, immediately behind the parietals, occupying several dorsal scales (4–5 complete scales on each side). Most of rostral and supralabials immaculate white, this color extending dorsally as a triangular wedge just behind each eye; a black streak across tops of anterior supralabials, extending narrowly under and up behind eye, then becoming less distinct and wider and dropping obliquely along the white postocular wedge to lower side of neck. Farther back, at about the level of ventrals 4–5, there are two white ocelli, separated medially by a space of three dorsal scales. These white marks extend to the belly. The dorsal body color is uniform brown, turning grayish on lower sides. A barely discernible lateral line of white dashes or dots along scale row 4; these pale markings are detectable anteriorly and posteriorly on body but do not extend noticeably onto the tail. Dark body color encroaching slightly onto ventrolateral ends of ventrals and subcaudals. The ventral The enigmatic Amazonian genus Eutrachelophis 11 Figure 4. Hemipenis of Lygophis lineatus (MZUSP 9775) in sulcate (A) asulcate (B), lateral (C), and apical (D) views; and Lygophis meridionalis (MZUSP 14762) in sulcate (E), asulcate (F), lateral (G), and apical (H) views. Scale bar = 1 mm. region of the body, including underside of head, immaculate pale white. Variation of paratypes (supplementary table S1). Female, MPEG 18250, 128 mm in SVL, 45 mm in TL, sexually immature juvenile as evidenced by visible umbilical scar. Male, MPEG 19550, 102 mm in SVL, 35 mm in TL, sexually immature as evidenced by visible umbilical scar. Female, MPEG 23860, 295 mm in SVL, 107 mm in TL, even destroyed, probably it is sexually mature as evidenced by total length. Female, MZUSP 10530, 235 mm in SVL, 92 mm in TL, sexually mature as evidenced by the size of the oviducts (2 mm in length). The measurements of the cephalic shields are summarized in supplementary table S1. Color pattern similar to holotype: head and neck black, encompassing a black-rimmed white nuchal ocelli (butterfly-shaped), anterior body turning blackish brown then brown posteriorly, with several ill-defined narrow whitish or pale brown crossbands in precaudal region; tail blackish brown above; a distinct lateral line of white dashes accentuated by black pigmentation along lower edges, extending along scale row 4, from neck onto tail; and pale white ventral surface. Hemipenis morphology (fig. 2). Hemipenis unilobed, noncapitate, with two laterally expanded apical disks. Spermatic sulcus divides into proximal portion of hemipenial body, with two branches running centrifugally on lateral surfaces of organ, ending very close to each other at the distal tip of lobe, near distal edge of each apical disk. Margins of sulcus spermaticus stout and bordered by spinules on basal to most of distal portion of lobe. Apical disks show a tissue fold surrounding their nude surface. They 12 H. Zaher, A.L.C. Prudente Figure 5. Holotype of Eutrachelophis papilio sp. nov. from Ituxi river, state of Amazonas, Brazil (MPEG 25471). Body in dorsal view (A), head in dorsal (B) and lateral views (C). Scale bar = 1 mm. contact each other along the midline of lobe, being separated by a vestigial of lobular tissue. Proximal half of the lobe being covered with spinules. Lobe tapering distally. Intrasulcar region with moderate hooked spines. Hemipenial body elliptical, covered by spines on both sides of organ. Lateral region of body with transversal series of enlarge spines, arranged in three to four rows from the proximal end to the base of lobe. Basal region ornamented with small disperse spines. Etymology. The specific epithet is derived from the Latin word “papilio”, gender masculine, and noun in apposition, in reference to the butterfly-shaped white ocellus on the nape. Distribution (fig. 6). Eutrachelophis papilio occurs in lowland rainforest in central Amazonia south of the Amazon River, in the states of Acre and Amazonas, Brazil. The type locality consists of a mixture of forest of varzea and Terra Firme, and is located near the Ituxi River (640 km long), one of the tributaries of the Purus River, in the state of Amazonas, Brazil (Avila-Pires et al., 2009). Two other specimens (MPEG 23862, MZUSP 10530) were collected in the Urucu River basin, located in the interfluve Purus-Juruá, region primarily composed of upland and dense Terra Firme forest, representing 80-85% of plant cover, and floodplain forest (Prudente et al., 2013). The fourth specimen was collected in Careiro da Várzea (MPEG 19950), a municipality typically of varzea (95%), the rest of the area being composed of Terra Firme forest. The fifth specimen (MPEG 18250) was also collected near a floodplain area on the banks of the Acre River, the largest tributary of the Purus River. Eutrachelophis bassleri Myers and McDowell, 2014 Diagnosis. Eutrachelophis bassleri is distinguished from all other species by the following combination of characters: 15-15-15 number of dorsal scale rows; 8 supralabials, 2nd and 3rd contacting loreal and 3rd to 5th bordering eyes; 8-9 infralabials, 1st to 4th or 1st to 5th 13 The enigmatic Amazonian genus Eutrachelophis Figure 6. Distribution of Eutrachelophis papilio sp. nov. (triangle), Eu. bassleri (circle), and Baliodryas steinbachi (lozenge). Black symbols represent type localities. contacting anterior chinshields and 4th and 5th or 5th and 6th posterior chinshields; 128-139 ventrals; 62-70 subcaudals; dorsolateral lines of vague dark spots (or fused crossbars) rather than dark anterior stripes; a lateral line of pale dashes or dots lies on scale row 4; hemipenis slightly bilobed with apical disks; and mean of 27.4 maxillary teeth subequal in size and recurved, followed by diastema and two ungrooved fangs (Myers and McDowell, 2014). Comparisons. Eutrachelophis bassleri differs from Eu. papilio by having a pair of blackrimmed white ocelli on the nape (vs. a single laterally expanded, butterfly-shaped, blackrimmed white ocelli in Eu. papilio), lower number of ventrals (128-139 vs 139-145 in Eu. papilio), and shorter hemipenial lobe that is rounded distally (longer hemipenial lobe tapering distally in Eu. papilio). Distribution (fig. 6). Eutrachelophis bassleri occurs in the Ecuadorian and Peruvian rainforests in the western portion of the Amazonian basin, from east-central Ecuador to northeast and central Peru (Myers and McDowell, 2014). Baliodryas gen. nov. Type-species. Baliodryas steinbachi, new combination (Zoobank: urn:lsid:zoobank.org:act:CE 1732D8-35CB-4D80-B3D3-3D8F980E5C75). Diagnosis. This new genus can be distinguished from other genera of the Dipsadidae by the presence of deeply divided hemipenial lobes with lobular projections that expand beyond the tip of the sulci, the latter ending on the middle of the lobes and opening at the base of a small vestigial apical disk. Etymology. Baliodryas is a masculine noun from the Greek βᾰλιóς, spotted, dappled, and 14 δρυάς, a kind of snake (Heitsch, 1963; Leigh, 2016). Baliodryas steinbachi new combination Rhadineae steinbachi Boulenger, 1905 Aporophis melanocephalus Griffin, 1916 Liophis steinbachi – Amaral, 1930 Eutrachelophis steinbachi – Myers and McDowell, 2014 Diagnosis. Baliodryas steinbachi is distinguished from all other species by the following combination of morphological characters: dorsal scales smooth, 15-15-15 scale rows; 134-140 ventrals; 66-81 subcaudals; hemipenis deepely bilobed; long lobes with a small nude area considered to be a remnant of the apical disks; intrasulcar region with small spines and two rows of larger spines; asulcate side with two large spines extend nearly to the proximal end of the hemipenis body; conspicuous pair of ocellar markings on the nape and a pair of oblique pale markings touching the upper anterior and upper posterior edges of the eye; dark head color extends onto the neck as unbroken dorsal and lateral stripes; and 24 maxillary teeth subequal in size and recurved, followed by diastema and two ungrooved fangs. Comparison. Baliodryas steinbachi differs from Eutrachelophis papilio and Eu. bassleri by hemipenis deeply bifurcate, with long lobes (vs. hemipenis slightly bilobed with short lobes), apical disks elliptical and small (vs. apical disks expanded and fused in the middle region), dark head color with two pairs of oblique markings touching the upper anterior and upper posterior edges of the eyes (vs. preocular region and top of the head brown, without markings), and lower part of the supralabials white and underside of the head white (vs. lower part of supralabials white with a triangular wedge just behind eyes). Differs from Eu. papilio by having one pair of white ocelli not fused on the dorsum (vs. white butterfly-shaped ocellus on the nape), and from Eu. bassleri by presence of conspicuous lateral line of pale dashes or dots on scale row 6 (vs. barely discernible lateral line of white dashes or dots along scale row 4). H. Zaher, A.L.C. Prudente Hemipenis morphology (fig. 2). Hemipenis deeply bilobed, noncapitate, sulcus spermaticus divides at proximal third of hemipenial body and runs centrolineally until it reaches the level of lobular crotch, where the branches diverge to take a centrifugal position laterally in the lobe. Branches terminate in a slightly expanded nude and wrinkle area in the middle of the lobes. Slender lobes, tubular projections, twice as long as the hemipenial body, with slightly narrower tips. Presence of a slight lobular constriction, marking the end of the sulcus spermaticus, defines two areas in the lobes, distal half covered by rows of sharp, enlarged and high spines, and proximal half covered by irregularly distributed spinules. Body covered by enlarged lateral spines and a few dispersed spinules that tend to concentrate on the lateral border of the sulci. Intrasulcar region ornamented by two rows of enlarged spines with five to six spines arranged along the branches of the sulcus spermaticus. In the rows of spines, two are very large followed by six to seven smaller ones, gradually reducing the spines arranged on the lateral surface of the organ towards the lobes. Distally to the more enlarged spines, at the level of the sulcus division, hemipenial body shows a slight constriction that ressembles a semicalycular condition. On asulcate side, base of the organ with a sparse distribution of spinules and two large spines extend nearly to the proximal end of the hemipenis. Distribution (fig. 6). Baliodryas steinbachi is known from central Bolivia, near the eastern base of the Cordillera Oriental (Myers and McDowell, 2014). We expand the distribution of the species to southwestern Brazil, where a specimen was found in the municipality of Colíder (10°48′ 19′′ S, 55°27′ 18′′ W), state of Mato Grosso, in the vicinity of the hydroelectric power station Teles Pires. Discussion Myers and McDowell (2014: 47) considered a close affinity between Eutrachelophis and the The enigmatic Amazonian genus Eutrachelophis Xenodontini due to the “total absence of epithelial ornamentation” in the former (except for spines and spinules) a condition approached only by the Xenodontini among dipsadid tribes “whose only ornamentation is the apical disk”. However, they did not recognize the presence of apical disks or any rudimentary or modified condition in Eutrachelophis that could suggest its inclusion in the Xenodontini. According to these authors, the hemipenis of Eu. bassleri lacks hemipenial lobes while the one of Eu. steinbachi, although with well-developed lobes, retains sulci spermatici that fall short of the tip of the lobes, thus lacking the portion in which an apical disk develops (Myers and McDowell, 2014: 47). Our study revealed the presence of apical disks as modified structures in both species of Eutrachelophis and in Baliodryas steinbachi. The loss of bilobation in Eutrachelophis resulted in the fusion of both disks into a single nude lobular surface. However, important anatomical marks, such as the ill-defined edges (or lips) of the apical disks, their lateral position on the lobe and the opening of the sulcus spermaticus, allow their identification. Similarly, small nude areas receiving the tip of the sulcus spermaticus on each lobe of the hemipenis of Baliodryas correspond to highly reduced apical disks. The lack of body calyces, capitula, capitular grooves, or any other microornamentation other than spines and spinules in the lobes, are additional derived characteristics shared only with Xenodontini (Myers and McDowell, 2014: 47). Although the hemipenial morphology of Eutrachelophis and Baliodryas provided compelling evidence for their allocation in the Xenodontini, their phylogenetic affinities within the tribe remain uncertain. Within the Xenodontini, only the genus Lygophis (fig. 4) approaches the hemipenial condition seen in Eutrachelophis, with very reduced lobes that correspond to an intermediate state between a fully bilobed and 15 an unilobed hemipenis. Their apical disks, although still separated and well-defined by expanded lips, are nevertheless restricted to the distal portion of the hemipenis, as in Eutrachelophis. A hypothetical closer affinity between Eutrachelophis and Lygophis is not discarded, being supported by a shared tendency to hemipenial unilobation. There is therefore no need for complex developmental explanations to cope with the unusual hemipenial morphology of Eutrachelophis. On the other hand, Baliodryas retains a very peculiar hemipenial morphology, with an “apical tuff covered with differential spines” (Myers and McDowell, 2014: 45) projecting distally to the end of the sulcus spermaticus and reduced apical disk area. This morphology is unique to this genus and does not seem to be approached by any other taxon of the Xenodontini or Dipsadidae. Baliodryas steinbachi was previously known to occur only in the central region of Bolivia, near the eastern slopes of the Cordillera Oriental (Myers and McDowell, 2014). Our new specimen collected in the municipality of Colider in the northern part of the state of Mato Grosso in Brazil, expands the distribution of the species in more than 1000 km towards central Brazil. Acknowledgements. We are grateful to the following curators and staff for allowing us to examine specimens under their care: A. Resetar (FMNH), C. Spencer and D. Wake (MVZ), C. W. Myers, D. Frost, D. Kizirian, and R. Pascocello (AMNH), G. Schneider (UMMZ), P. Passos (MNRJ). We are deeply indebted to W. Wosiacki and Ricardo Guerra Fuentes for the photographs of preserved specimens. We thank G. Shepard for English review. This research received grant supports from the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), and Fundação Amazônia de Amparo à Estudos e Pesquisas (FAPESPA) to ALC. Prudente (PQ-CNPq 302611/2018-5, PROTAX 440413/2015-0, FAPESPA 2016/111449) and H. Zaher (BIOTA FAPESP 2011/50206-9, FAPESP 2018/11902-9; PQ-CNPq 301298/94-7). Supplementary material. Supplementary material is available online at: https://doi.org/10.6084/m9.figshare.11347481 16 References Amaral, A. (1930): Estudos sobre ophidios neotropicos XVIII. Lista remissiva dos ophidios da região neotropica. Memórias do Instituto Butantan 4: 126-271 [1929]. Avila-Pires, T.C.S., Vitt, L.J., Sartorius, S.S., Zani, P.A. (2009): Squamata (Reptilia) from four sites in southern Amazonia, with a biogeographic analysis of Amazonian lizards. Boletim do Museu Paraense Emilio Goeldi, Ciências Naturais 4: 99-118. Boie, F. 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Associate Editor: David Jandzik. 23862, MZUSP 10530), Farancia abacura (KU 214419), Farancia erythrogramma (KU 197245), Geophis hoffmanni (AMNH 113561), Helicops pastazae (AMNH 49143), Heterodon nasicus (MNHN 1993.1625, MNHN 3636), Appendix: Material examined Lygophis anomalus (MZUSP 7464), Lygophis dilepis Dipsadidae: Apostolepis cf. nelsonjorgei (MZUSP 20636), (MZUSP 7127, MNHN 1967.147), Lygophis lineatus Atractus maculatus (IB 40003), Baliodryas steinbachi (MZUSP 9775, MZUSP 20502), Lygophis meridionalis (MZUSP 23115), Carphophis amoenus (AMNH 99112), Conophis pulcher (AMNH 117934, MNHN 5981), Con- (MZUSP 14762), Oxyrhopus occipitalis (AMNH 129255), tia tenuis (UMMZ 133519-1, UMMZ 133370), Diadophis Philodryas mattogrossensis (AMNH 141377), Philodryas dugesi (MNHN 1975.171), Diadophis punctatus (AMNH olfersii (IBSP 63455), Sibon sartorii (LSUMZ 23243), 3711, MNHN 1897.170), Erythrolamprus almadensis Tachymenis chilensis (MZUSP 8239), Tachymenis peru- (AMNH 22458; IB 53445), Erythrolamprus atraventer (MZUSP 4912), Erythrolamprus viana (KU 135193), Urotheca decipiens (KU 103892), aesculapii (MZUSP 22848, MPEG 26329, MNHN 1990.4326), Ery- Urotheca multilineata (AMNH 98284), Xenodon dor- throlamprus bizona (AMNH 35576), Erythrolamprus co- bignyi (MZUSP uncatalogued specimen), Xenodon histri- bella (AMNH 81468), Erythrolamprus juliae (MNHN cus (MNRJ 4615), Xenodon merremi (AMNH 140198, 1977.1617), Erythrolamprus mimus (AMNH 12697), Erythrolamprus pyburni (AMNH 143811), Erythrolamprus poecilogyrus (MZUSP 10006, MNHN 1993.1624), Ery- MNRJ 3236, MNRJ 4496), Xenodon neuwiedii (MNRJ 2880, MNRJ 4782), Xenodon rabdocephalus (AMNH throlamprus reginae (MZUSP 12557), Eutrachelophis pa- 140265), Xenodon severus (AMNH 142634, IB 51997), pilio (MPEG 18250, MPEG 25471, MPEG 19950, MPEG Xenopholis scalaris (AMNH 60799).