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Higher TaxaTyphlopidae (Typhlopinae), Typhlopoidea, Serpentes, Squamata (snakes)
Common Names 
DistributionBrazil (Bahia: Fazenda Nova Alegria)

Type locality: 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.  
TypesHolotype: MZUSP 18787, adult female (field number MTR 13542), collected by Miguel T. Rodrigues and collaborators on 26 March 2007 (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). 
DiagnosisDiagnosis: “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.” (Graboski et al. 2022)

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.” (Graboski et al. 2022)

Coloration of the holotype in preservative: “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).” (Graboski et al. 2022)

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).” (Graboski et al. 2022) 
CommentDistribution: for a map see Graboski et al. 2022: 16 (Fig. 10). 
EtymologyThe 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. 
  • Graboski, Roberta; Juan C Arredondo, Felipe G Grazziotin, Ricardo Arturo Guerra-Fuentes, Ariane A A Da Silva, Ana L C Prudente, Roberta R Pinto, Miguel T Rodrigues, Sandro L Bonatto, Hussam Zaher 2022. 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, zlac059 - get paper here
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