Paikwaophis, Kok & Means, 2024

Kok, Philippe J. R. & Means, D. Bruce, 2024, Hiding in the mists: molecular phylogenetic position and description of a new genus and species of snake (Dipsadidae: Xenodontinae) from the remote cloud forest of the Lost World, Zoological Journal of the Linnean Society (Zool. J. Linn. Soc.) 200 (2), pp. 505-531 : 509-514

Paikwaophis gen. nov.

( Figs 4–13)

Zoobank registration: urn:lsid:zoobank.org:act:FF55996A-80A3-4189-838F-269A47BBD9F0 .

Type species: Paikwaophis kruki sp. nov.

Etymology: The generic name is derived from the river name ‘Paikwa’ (referring to the type locality) and the Greek ‘ ophis ’ (meaning snake).

Generic diagnosis: Paikwaophis can be differentiated from all other Xenodontinae (and Dipsadidae ) by the combination of the following morphological characters:head poorly distinct from neck; body robust, slightly wider than high; tail short, ~13% of total length in female; snout short and blunt; rostral wider than high, visible from above; undivided nasal; paired internasals; paired prefrontals; subtriangular frontal; absence of loreal; presence of minute cephalic sensory pits; eye medium in size, with vertically oval pupil, iris dark reddish orange; single supraocular; one preocular, two postoculars; three rows of temporals; chinshields medium in size, anterior chinshields projecting frontolaterally; body scales rhomboid, smooth, lacking keels or apical pits, 17 dorsal scale rows without reduction; subcaudals paired; anal entire; aglyphous, presence of a diastema; low number of teeth: 7 prediastemal maxillary teeth, 2 enlarged postdiastemal maxillary teeth, 8 pterygoid teeth, 5 palatine teeth, 12 dentary teeth; neural spines smooth, ungrooved and not laterally expanded; 175 trunk vertebrae; absence of hypapophyses on posterior vertebrae; caudal vertebrae with distinct haemapophyses; lacrimal foramen large and vertically ovoid; and postorbital bone highly reduced, free from the frontal bone.

Comparisons with known genera of Xenodontinae not included in our phylogenetic analyses: Paikwaophis is distinguished from Amnesteophis (assigned to the monotypic tribe Amnestophiini ; Myers 2011) by, inter alia, the dentition: syncranterian (absence of a diastema), 25 maxillary teeth and 30 pterygoid teeth in Amnesteophis vs. diacranterian (presence of a diastema), 9 maxillary teeth and 8 pterygoid teeth in Paikwaophis .

Paikwaophis is distinguished from Baliodryas (assigned to the tribe Eutrachelophiini ; Myers and McDowell 2014, Moraes et al. 2021) by, inter alia, the dentition: 25–28 maxillary teeth and 35–36 pterygoid teeth in Baliodryas vs. 9 maxillary teeth and 8 pterygoid teeth in Paikwaophis .

Paikwaophis is distinguished from the genus Cenaspis [unassigned to any tribe, seemingly endemic to the isolated highlands of western Chiapas in Mexico; the only known specimen has been found in the stomach of a Micrurus nigrocinctus (Girard, 1854) ; Campbell et al. 2018] by, inter alia, the state of the subcaudals and the maxillary dentition: single subcaudals in Cenaspis vs. divided subcaudals in Paikwaophis , and 10–15 maxillary teeth in Cenaspis vs. 9 maxillary teeth in Paikwaophis .

Paikwaophis is distinguished from Cercophis (unassigned to any tribe) by, inter alia, a short tail (13% of total length) vs. a long tail (42–54% of total length; Cunha and Nascimento 1982, Hoogmoed 2019) in Cercophis , and the maxillary dentition: 22 maxillary teeth in Cercophis vs. 9 maxillary teeth in Paikwaophis .

Paikwaophis is distinguished from Coronelaps (assigned to the tribe Elapomorphini ; Lema and Hofstadler Deiques 2010) and Ditaxodon (assigned to the tribe Phylodryadini ; Arredondo et al. 2020) by, inter alia, the dentition: opisthoglyphous (grooved fangs) in Coronelaps and Ditaxodon vs. aglyphous opisthodont (ungrooved fangs) in Paikwaophis .

Paikwaophis is distinguished from Incaspis (assigned to the tribe Incaspidini ; Arredondo et al. 2020) by, inter alia, the dentition: 10–15 maxillary teeth in Incaspis vs. 9 maxillary teeth in Paikwaophis and the absence of apical pits in Paikwaophis (vs. one or two consistently present in Incaspis ).

Paikwaophis is distinguished from Lioheterophis (unassigned to any tribe, monotypic, known only from the holotype collected in Campina Grande in north-eastern Brazil; Amaral 1935, Wallach et al. 2014) by, inter alia, the maxillary dentition: 17 maxillary teeth in Lioheterophis vs. 9 maxillary teeth in Paikwaophis ; and a distinct difference in the number of dorsal scale rows: 21 with reduction in Lioheterophis vs. 17 without reduction in Paikwaophis .

Paikwaophis is distinguished from Saphenophis (assigned to the tribe Saphenophiini ; Zaher et al. 1999) by, inter alia, the dentition: 19–22 maxillary teeth and 24–26 pterygoid teeth in Saphenophis ( Myers 1973) vs. 9 maxillary teeth and 8 pterygoid teeth in Paikwaophis .

Comparisons with the sister genus ( Xenopholis ): Although recovered as sister taxa with high support, Paikwaophis and Xenopholis ( Figs 12–15) are strikingly different both morphologically and osteologically. Both genera are easily distinguished by, inter alia (non-exhaustive):

(i) The shape of the head and neck: marked neck and proportionally flatter/longer head in Xenopholis vs. neck poorly marked and short head in Paikwaophis ( Figs 3, 4).

(ii) The presence of numerous minute cephalic sensory pits in Paikwaophis (absent in the Xenopholis specimens examined and not reported by Gomes et al. 2020).

(iii) The number of trunk vertebrae: 128–129 in Xenopholis vs. 175 in Paikwaophis .

(iv) The shape of the vertebrae:neural spines are expanded laterally, forming rugose shields divided by a median groove in Xenopholis ( Hoge and Federsoni 1974) vs. smooth, ungrooved and not laterally expanded in Paikwaophis ( Fig. 12); and hypapophyses on posterior vertebrae are absent in Paikwaophis (present in Xenopholis ; Hoge and Federsoni 1974).

(v) The shape of the caudal vertebrae: caudal vertebrae have distinct haemapophyses in Paikwaophis (absent in Xenopholis ).

(vi) The dentition: opisthoglyphous (grooved fangs) in Xenopholis ( Gomes et al. 2020) vs. aglyphous opisthodont (ungrooved fangs) in Paikwaophis ( Fig. 12), and a much higher number of teeth in Xenopholis (13–15 prediastemal maxillary teeth, 14–28 pterygoid teeth, 7–10 palatine teeth and 23–24 dentary teeth; Gomes et al. 2020) than in Paikwaophis (7 prediastemal maxillary teeth, 8 pterygoid teeth, 5 palatine teeth and 12 dentary teeth; Figs 7, 9, 10, 11, 15).

(vii) The shape and size of the lacrimal foramen: small and horizontally ovoid in Xenopholis vs. large and vertically ovoid in Paikwaophis ( Fig. 13).

(viii) The shape and size of the postorbital bone: large and projecting ventrolaterally in Xenopholis vs. highly reduced, crescent-shaped in Paikwaophis ( Figs 7, 15).

Comparisons with (near-) sympatric dipsadid genera with superficially similar morphology: In the Pantepui region (and northern Brazil) and based on superficial morphology/body plan and fossorial/semi-fossorial habits, Paikwaophis could be confused only with Atractus Wagler, 1828 (to which it keys out in the paper by Cole et al. 2013) and Apostolepis Cope, 1862 . In the field, Paikwaophis is easily distinguished from Atractus (assigned to the subfamily Dipsadinae ; Zaher 1999) by the absence of a loreal (present in Atractus ; e.g. Hoogmoed 1980, Kok 2006) and two pairs of chinshields (single pair in Atractus ; e.g. Hoogmoed 1980, Kok 2006); and from Apostolepis (assigned to the tribe Elapomorphini ; see Zaher et al. 2009) by having 17 dorsal scale rows (15 in Apostolepis ; e.g. Entiauspe-Neto et al. 2021) and paired nasals (nasal plate undivided in Apostolepis ; e.g. Entiauspe-Neto et al. 2021). It should be stressed that outside the family Dipsadidae , Paikwaophis could possibly be confused with the colubrid genus Tantilla Baird and Girard, 1853 , from which it is distinguished immediately by having 17 dorsal scale rows (15 in Tantilla ; e.g. Koch and Venegas 2016).

Content: Currently monotypic, containing only Paikwaophis kruki .

Distribution: Known only from the type locality (see ‘Holotype’ below).