Amerotyphlops illusorium, Graboski & Arredondo & Grazziotin & Guerra-Fuentes & Da Silva & Prudente & Pinto & Rodrigues & Bonatto & Zaher, 2023

Graboski, Roberta, Arredondo, Juan C., Grazziotin, Felipe G., Guerra-Fuentes, Ricardo Arturo, Da Silva, Ariane A. A., Prudente, Ana L. C., Pinto, Roberta R., Rodrigues, Miguel T., Bonatto, Sandro L. & Zaher, Hussam, 2023, Revealing the cryptic diversity of the widespread and poorly known South American blind snake genus Amerotyphlops (Typhlopidae: Scolecophidia) through integrative taxonomy, Zoological Journal of the Linnean Society 197, pp. 719-751 : 738-740

AMEROTYPHLOPS ILLUSORIUM SP. NOV.

( FIG. 14 ; SUPPORTING INFORMATION, FIGS S7 , S 8 )

Z o o b a n k r e g i s t r a t i o n: u r n: l s i d: z o o b a n k. org:act: AF7FA356-4412-4C70-AA6D-8C4D24D81966

Holotype: An adult female, MZUSP 18787 , (field number MTR 13542 ), collected by Miguel T. Rodrigues and collaborators on 26 March 2007 from Fazenda Nova Alegria (16° 31 ′ 50.7 ′′ S, 39° 07 ′ 06.7 ′′ W, c. 30 m a.s.l.), municipality of Trancoso , state of Bahia, Brazil ( Fig. 14 ; Supporting Information, Fig. S7 ).

Paratypes: Two male specimens, MNRJ 19614 and MNRJ 19613, collected by Tiago S. Soares between 6 and 15 June 2010 from Praia de Porto Seguro, municipality of Trancoso, state of Bahia, Brazil (Supporting Information, Fig. S8A–D ).

Diagnosis: This species is distinguished from all other South American congeneric species by the unique combination of the following of characters: (1) nasal suture incomplete; (2) rostral scale oval; (3) supralabial scales four; (4) infralabial scales three; (5) rows scales around the body 20/20/18; (6) mid-dorsal scales 221–230; (7) ventral scales 210–219; (8) rows of dorsal scales dark brown 13–15; (9) rows of ventral scales yellowish cream and immaculate five to seven; (10) caudal spine dark brown; (11) subcaudal scales ten to 12; (12) maximum TTL 229 mm; (13) maximum TL 6 mm; (14) nasal process of premaxilla contacting the vertical laminae of the nasals in the anterodorsal and posteroventral portions, with the central portion not in contact, leaving a large round canal between the olfactory chambers; (15) large palatine fossa on the lateral side of the maxilla; (16) maxilla with a straight medial border; (17) ventral pterygoid process of palatine straight; (18) ratio between length of ventral pterygoid process of palatine and skull length 0.06; (19) angle between mandibular condyle articulation and the retroarticular process of the compound bone close to 90°; and (20) dorsal surface of dentary bone with one to two evident foramina.

Amerotyphlops illusorium differs from A. costaricensis , A. lehneri , A. microstomus , A. stadelmani , A. tasymicris , A. tenuis , A. trinitatus and A. tycherus by having an incomplete nasal suture (vs. complete nasal suture); from A. arenensis , A. caetanoi , A. amoipira , A. minuisquamus , A. paucisquamus and A. yonenagae by having 20/20/18 rows scales around the body (vs. 18/16/14, 18/18/14, 20/18/14 or 20/18/ 15 in A. minuisquamus and 18/18/ 18 in A. arenensis , A. caetanoi , A. amoipira , A. paucisquamus and A. yonenagae ); from A. reticulatus by having highly pigmented cephalic scales with a dark brown dorsum and dorsum tail brown (vs. yellow and few pigmented cephalic scales, dorsum brown or black and dorsum tail black with cream or yellow spot); from A. montanum by having a smaller rostral width (RW1) at the dorsal portion, between 1.22 and 1.54 mm (vs. a larger rostral width at the dorsal portion 1.88 mm); from A. martis by having a largest number of mid-dorsal scales, between 221 and 230 (vs. fewer number of mid-dorsal scales, between 208 and 217); and from A. brongermianus by having the ventral portion of the pterygoid process of palatine straight (vs. ventral pterygoid process of palatine curved). Table 1 shows additional morphometric characters and scale patterns found in A. illusorium and morphologically similar species distributed in southern and north-eastern Brazil.

Description of the holotype: Adult female, TTL 229 mm, TL 6 mm, MBD/(SVL-HR) 0.037 mm and TL/SVL 37.16 mm. Head slightly depressed dorsoventrally, not wider than ‘neck’. Snout round in dorsal and ventral views. Rostral oval, longer than wide, narrow at anteroposterior region and wider at medial region; visible in dorsal view, extending ventrodorsally without reaching the imaginary transverse line between anterior borders of eyes. Rostral contacting nasal (anterior and posterior) dorsolaterally and first supralabial and anterior nasal scales ventrally. Nasal suture incomplete, only partially dividing the anterior and posterior portions of nasal scale. Suture begins in the upper edge of second supralabial, passes through nostril, but fails to reach rostral. Anterior nasal in contact with first infralabial and upper edge of second infralabial. Posterior nasal longer than wide, contacting upper margin of second supralabial and preocular. Supralabials four, fourth twice longer than third. Infralabials three, third largest. Eye diameter 0.77 mm; eyes not visible in ventral view, located dorsolaterally, close to suture between preocular and ocular scales, completely covered by ocular scale. Ocular scales contacting frontal. Body cylindrical and robust. Midbody diameter 8.28 mm. Dorsal and ventral scales cycloid, wider than long, highly imbricated and arranged in diagonal series; scale rows around the body 20/20/18. Mid-dorsal scales 221. Ventral scales 218. Cloacal plate rounded, bordered anteriorly by three rows of scales and posteriorly by five rows of scales. Subcaudal scales ten, excluding the terminal spine. Terminal spine large, stout base and dark brown.

Skull osteology (N = 2; MZUSP 18787 and MNRJ 19613): Length of the skull 7.03–8.22 mm, and skull width 3.46–3.99 mm. The snout region has a globular enlarged-shape and highly consolidated. The snout articulates with the braincase by the nasal and prefrontal sutures and with the frontal bone. The anteroventral region of the premaxilla has a short backward process. The midsagittal lamina separates both sides of the premaxilla ( Fig. 5 ). The lamina of the premaxilla is confluent with the mid-dorsal laminae of the nasals and with the mid-dorsal ridges of the vomeronasal cupola of the septomaxillae ( Fig. 5 ). The nasal process of premaxilla contacting the vertical laminae of the nasals in the anterodorsal and posteroventral portions, with the central portion not in contact, leaving a large round canal between the olfactory chambers ( Fig. 5A ). The medial side of the maxilla has a shallow depression (or fossa), where lodges the maxillary process of the palatine. The palatine fossa is on the lateral side of the maxilla, in the region of the articular fossa. The palatine fossa is large ( Fig. 6A ), with diameters between 0.24 and 0.29 mm long. The medial border of the maxilla is straight-shaped ( Fig. 6A ). The pterygoid process of the palatine is straight-shaped and ventrally directed ( Fig. 7A ). The retroarticular process projects in parallel to the horizontal plane of the articular. The angle between mandibular condyle articulation and the retroarticular process of the compound bone is close to 90° ( Fig. 8A ). The edentulous dentary is restricted to the distal end of the mandible, articulating mainly with the splenial. The dorsal side of the dentary is flat and pierced by one or two foramina ( Fig. 9A ).

Coloration of the holotype in preserƲatiƲe: Dorsum (13/13/13 rows scales) dark brown, venter (7/7/5 rows scales) yellowish cream ( Fig. S7A, B ). Dorsal portions of snout yellowish cream, with a dark brown spot, covering both rostral and nasal scales ( Fig. 14A, B ). Ventral portion of snout yellowish cream and immaculate ( Fig. 14C ). Symphysial region yellowish cream and immaculate ( Fig. 14C ). Dorsal head scales (supraoculars, frontal, postfrontal, parietals and occipitals) and dorsal portions of lateral head scales (ocular, nasal, and lower nasal) predominantly dark brown ( Fig. 14A, B ) and ventral portions yellowish cream ( Fig. 14C ). Cloacal plate pale yellowish cream and terminal spine dark brown ( Fig. S7B ).

Variation of paratypes: Number of subcaudal scales 11–12 (mean = 11.5, SD = 0.7, N = 2). Tail length 2.58– 3.0 % of TTL (N = 2). Largest male with 207 mm TTL. MBD 4.91–5.11 mm (mean = 5.01, SD = 0.13, N = 2); number of mid-dorsal scales 226–230 (mean = 228.0, SD = 2.82, N = 2); number of ventral scales 210–219 (mean = 214.0, SD = 6.36, N = 2); and number of scale rows around the body 20/20/18. The colour patterns of the paratypes are similar to that found in the holotype (Supporting Information, Fig. S8A–D ).

Etymology: The specific epithet is derived from the Latin adjective illusorius, illusory or ironic, in reference to the external morphology that challenges its identification when compared to Amerotyphlops brongersmianus .

Distribution and habitat: Amerotyphlops illusorium is known from Fazenda Nova Alegria, situated at 6 km from the municipality of Trancoso, in the state of Bahia, Brazil ( Fig. 10B ). This region is considered as part of the Atlantic Forest morphoclimatic domain, in the Bahia Coastal forest ecoregion, along the northeastern coast of Brazil ( Olson et al., 2001)

The prevalent phytophysiognomy in Trancoso presenting a restinga and ombrophilous dense lowland forests ( Veloso et al., 1991; Rizzini, 1997; Assis et al., 2011), with an elevational gradient ranging from sea level to 50 m a.s.l., with an annual average of temperature of 24.4 °C and rainfall between 1300 and 1600 mm, respectively ( Veloso et al., 1991; Rizzini, 1997; Assis et al., 2011; Santos, 2013). This region has several different levels of successional vegetation, with areas close to the sandplain with herbaceous, shrubs and arboreous forest and areas at the beginning of piedmont, with lowland forests, with medium height trees (approximately 20 m), with epiphytes and herbaceous understory ( Santos, 2013).

Figures

Figure 5. Three-dimensional cutaway views along the sagittal axis of the nasal cavity in Amerotyphlops species based on HRXCT data. A, Amerotyphlops brongersmianus (MZUSP 14689); B, Amerotyphlops caetanoi sp. nov. (MZUSP S-023380). Insert show a lateral profile of the skull of A. brongersmianus presenting in red the position of the detailed region. Scales bars equal to 5 mm. Abbreviations: pmx, premaxilla; smx, septomaxilla; vm, vomer; na, nasal.

Figure 6. Three-dimensional reconstruction of the lateral region of the skull in Amerotyphlops species based on HRXCT data. A, Amerotyphlops caetanoi sp. nov. (MZUSP S-023380); B, Amerotyphlops montanum sp. nov. (MZUSP 20065); C, Amerotyphlops brongersmianus (MZUSP 14674). Insert shows a lateral profile of the skull of A. brongersmianus presenting in red the position of the detailed region. Scales bars equal to 5 mm.Abbreviations:mx, maxilla; mxpalf, palatine articulation fossa of the maxilla.

Figure 7. Three-dimensional reconstruction of the lateroventral region of the skull in Amerotyphlops species based on HRXCT data. A, Amerotyphlops caetanoi sp. nov. (MZUSP S-023380); B, Amerotyphlops brongersmianus (MZUSP 14674). Insert shows a lateral profile of the skull of A. brongersmianus presenting in red the position of the detailed region. Scales bars equal to 5 mm. Abbreviations: mx, maxilla; palmx, palatine maxillary process; palptv, palatine pterygoid ventral process; pt, pterygoid.

Figure 8. Three-dimensional reconstruction of the posterior region of the left mandible in Amerotyphlops speciesbased on HRXCTdata.A,Amerotyphlops caetanoisp. nov. (MZUSP S-023380); B, Amerotyphlops brongersmianus (MZUSP 14674). Insert shows a lateral profile of the skull of A. brongersmianus presenting in red the position of the detailed region. Scales bars equal to 5 mm. Abbreviations: cb, compound bone; q, quadrate; rp, retroarticular process.

Figure 9. Three-dimensional reconstruction of the anterior region of the left mandible in Amerotyphlops species based on HRXCT data. A, Amerotyphlops caetanoi sp. nov. (MZUSP S-023380); B, Amerotyphlops montanum sp. nov. (MZUSP 20065). Insert shows a lateral profile of the skull of A. brongersmianus presenting in red the position of the detailed region. Scales bars equal to 5 mm. Abbreviations: cb, compound bone; co, coronoid; d, dentary; sp, splenial.

Figure 10. Geographical distribution of nine species belonging to the genus Amerotyphlops from South America.A, zoomed map of species distributed in the north-eastern Brazil; B, zoomed map of four new species described in this work. Symbols: A. arenensis (black pentagons); A. amoipira (black diamonds); A. brongersmianus (black circles); A. yonenagae (black squares); A. pauciquamus (black inverted triangles); A. martis sp. nov. (black star); A. montanum sp. nov. (black triangles); A. illusorium sp. nov. (black cross); Amerotyphlops caetanoi sp. nov. (black asterisk).

Figure 14. Holotype of Amerotyphlops illusorium sp. nov. (MZUSP 18787). Head in left lateral (A), dorsal (B) and ventral (C) views. TTL = 229 mm. Scale bar equal to 5 mm.