Liotyphlops sousai, Santos & Reis, 2018

Entiauspe-Neto, Omar M., Franco, Francisco L., Koch, Claudia, Tiutenko, Arthur, Wingert, Juliana M. & Borges-Martins, Márcio, 2023, More than meets no eyes: Taxonomic status of a Liotyphlops Peters, 1881 (Serpentes: Anomalepididae) blindsnake from the Atlantic Rainforest, Zoologischer Anzeiger 303, pp. 10-25 : 14-17

3.2. Identity of Liotyphlops sousai

In the description of L. sousai , no information is given regarding the sex of the type specimen ( Santos & Reis, 2018:507). We were unable to visually verify the presence of an hemipenis in the holotype of L. sousai . Examination of its scale counts (particularly, the number of subcaudals and ventrals to subcaudals ratio) and manual probing also corroborate that the holotype of L. sousai is actually a female specimen. According to the diagnosis of Santos & Reis (2018), L. sousai “ is distinguished from all other Liotyphlops , except Liotyphlops anops , Liotyphlops argaleus , and L. trefauti , by having four scales contacting the posterior edge of the prefrontal (vs. three scales contacting posterior edge of prefrontal) ( Santos & Reis, 2018:507). According to the authors, the contact of four scales to the posterior edge of the prefrontal appears to be the sole diagnostic character of L. sousai against L. beui . As mentioned before, individual contact states among head scales in Liotyphlops are considered as highly variable, and other authors suggest not describing new species using small series due to this ( Dixon and Kofron, 1983). The “ four scales contacting the posterior edge of prefrontal ” are defined by Dixon and Kofron (1983) as being postfrontals, and regarded as variable to their size and number in all species of Liotyphlops .

Closer examination of the holotype ( UFRGS 6274 ) reveals that the contact of four postfrontal scales to the posterior edge of prefrontal is actually absent, with a seemingly aberrant ocular scale, that produces a proximal ridge, which was misinterpreted as a projection of a postfrontal scale (Supplementary Fig. 2 ); the left side of the head on the holotype also has three postfrontal scales contacting the prefrontal. Therefore, the diagnostic of four postfrontal scales in contact with the prefrontal scale is considered herein as unreliable and erroneous .

Of the holotype of L. sousai , there are CT scan images of the skull in Santos & Reis (2018). No description or raw data were made available on request to the authors. Therefore, we can only compare the skulls from the three paratypes of L. beui with the images from the holotype of L. sousai presented in Santos & Reis (2018), drawing limited conclusions regarding similarities and differences. One of the most striking differences in the skull of the holotype of L. sousai compared to that of L. beui , is the fact that there is still a rather large fontanelle between the parietal bones of L. sousai and there are also rather large distances between most of the other cranial bones. Although possible to constitute an artifact of the CT scan method, these are typical features for a juvenile blind snake in which the ossification of the skull is not yet completed due to ontogenetic variation of dermal bones ( Cundall & Irish, 2008). Since the paratypes of L. beui are adult specimens, we cannot compare aspects related to bone distances and sizes of foramina between these specimens and the holotype of L. sousai . As a further difference, in L. sousai the anterior surface of the nasal is not rugose thickened, as the anterior end of the nasal does not appear pointed in the dorsal view. Instead, it exhibits foramina on both sides of the midline. As similarities of L. sousai and L. beui and shared differences to L. albirostris can be noted the absence of a supraoccipital bone, as well as a more pronounced and longer projection of the lateral flange of the nasal.

The only noteworthy difference in L. sousai is the presence of a supratemporal bone, which is absent in the analyzed paratypes of L. beui and present in the holotype of L. ternetzii . According to Santos (2018), this would represent an intraspecifically variable character, considering that of four specimens of L. beui examined by this author (MCP 10853, MCP 16362, MCZ-R 16702, MCZ-R 17842), the two paratypes also lacked the supratemporal bone, whereas the other two specimens had it. Therefore, together with our additionally examined paratype (BMNH 1946.1.11.12), this bone was absent in three specimens and present in two. Rage (1984) describes the supratemporal as a thin and minute, rudimentary bone in Anomalepididae and Leptotyphlopidae , lacking its functional articulation with the skull. In Leptotyphlopidae, Kley (2006) reports a non-ossified ligament that is displaced between the lateral surface of the exoccipital and dorsomedial aspect of the proximal quadrate head, in accordance with the interpretation of Rage (1984), homologous to the supratemporal bone. Kley (2006) raises the possibility of the transformation of dermal bones into ligamentous tissues for the supratemporal, which could be prone to ontogenetic and intraspecific variation, and also would not be visible in the osteological analyses, requiring histological analyses for their visualization. Furthermore, Rieppel et al. (2009) reports different degrees in ossification for the supratemporal in anomalepidids, ranging from the much reduced supratemporal of Typhlophis squamosus (Schlegel, 1839) to absent in Anomalepis aspinosus Taylor, 1939 . Palci (2014) also reports a variable presence of supratemporal bones in the genus Anomalepis , that was previously reported as lacking a supratemporal bone ( McDowell and Bogert, 1954; Haas, 1968; Rieppel et al., 2009). Rieppel (1979) suggests that neoteny, paedomorphosis in ontogenetic ossification, can be attributable for the disappearance of the lateral wing of the basisphenoid in Scolecophidia. Therefore, we find it likely that the visualization of the supratemporal bone in scolecophids, possibly related to different degrees in ossification, demineralization due to exposure to formalin, or even visualization technique artifacts, is prone to intraspecific variation.

Our final alignment totalized 490 base pairs of the 16S rRNA partial gene fragment, for 24 Scolecophidia terminals and two outgroups (Supplementary File 1). Our maximum likelihood phylogenetic inference recovers a final tree topology with a score InL = 2336.628103, supporting the monophyly of the genera Liotyphlops , Typhlops , and Epictia , with a strongly supported clade (bootstrap support> 90) containing L. sousai (UFRGS 6274) from Santa Catarina and L. beui (KR815891.1, UFRGS 6494) from S˜ao Paulo and Rio Grande do Sul ( Fig. 3A ). The observed uncorrected p -distances also provide no support for genetic divergence among these taxa, ranging from 0 to 1% ( Fig. 3B ). Similarly, intraspecific genetic variation for Typhlops biminiensis (Richmond, 1955) are also recovered as ranging from 0 to 1%, in Epictia tenella Klauber, 1939 as 0%, and in L. albirostris ( Peters, 1858) as ranging from 0 to 2%. Our ASAP, GMYC, PTP, and bPTP species delimitation analyses also support a single evolutionary entity between L. sousai and L. beui . Our Bayesian inference also recovers a single clade with L. sousai and L. beui , with terminals likely diverging during the early Pleistocene, an interspecific divergence similar to what is observed in L. albirostris ( Fig. 4 ). These results consistently support a conspecific relationship between L. sousai and L. beui .

Another issue is raised by the sympatry of L. sousai and L. beui . Although there is no explicit mention to this in the work of Santos & Reis (2018), another specimen of Liotyphlops was also found in the same locality as the type of L. sousai , the Usina Hidrel´etrica Passos Maia, at Passos Maia municipality, Santa Catarina , Brazil, as indicated by the appendix of examined material. The single mentioned specimen (UFRGS 6275), also from Usina Hidrel´etrica Passos Maia, was identified by Santos & Reis (2018) as L. beui . Further examination in the same collection revealed additional specimens from the same locality, and that these would represent a series (UFRGS 6272, 6273, 6274 [holotype of L. sousai ], 6275) collected on the same day.

Direct examination of the series of Liotyphlops specimens from Usina Hidrel´etrica Passos Maia (UFRGS 6272, 6273, 6274 [holotype of L. sousai ], 6275) reveals no consistent character for its interspecific diagnosis. A comparison of size and coloration between the holotype of L. sousai (UFRGS 6274) and a sympatric L. beui (UFRGS 6275) ( Figs. 5–6 ) reveals identical phenotypes. Furthermore, a comparison between morphological diagnostic characters reveals a complete overlap in pholidosis between L. sousai and L. beui ( Table 1). Therefore, we propose to allocate L. sousai as a junior synonym of L. beui . We also provide a redescription for a topotypical specimen of L. beui below.

Figures

Fig. 2. Principal Component Analysis (PCA) for females (left) and males (right) of the six OTUs analyzed in this work.

Fig. 3. Phylogenetic inferences and uncorrected p-distances for Scolecophidia terminals, based on the small subunit ribosomal RNA (16S rRNA) gene fragment. A) Maximum likelihood (RAxML) phylogenetic tree inference and geographic distribution of evaluated samples (white circles = L. beui literature records; black and white circles = L. beui examined records); B) Pairwise uncorrected p-distances for Scolecophidia terminals.

Fig. 4. Maximum clade credibility Bayesian tree, based on the small subunit ribosomal RNA (16S rRNA) gene fragment, highlighting the divergence time of terminals. Bars represent the 95% Highest Posterior Density (HPD) interval for divergence dates. Scale indicates million years ago (Myr). Full topology and posterior probability support of nodes are provided as supplementary material. Analyses of species delimitation are: Bayesian Poisson Tree Process (bPTP); Poisson Tree Process (PTP); Assemble Species by Automatic Partitioning (ASAP); Generalized Mixed Yule Coalescent (GMYC). Inset photograph: Liotyphlops aff. wilderi from Minas Gerais, Brazil. Photograph credits: Henrique C. Costa.

Fig. 5. Head scalation of Liotyphlops beui (A, MCZ-R 17842, paratype) from Instituto Butantan, S˜ao Paulo, S˜ao Paulo state, southeastern Brazil, and Liotyphlops sousai (B, UFRGS 6274, holotype), from Passos Maia, Santa Catarina state, southern Brazil.

Fig. 6. Specimens of Liotyphlops from Passos Maia, Santa Catarina state, southern Brazil. A) Dorsal and ventral views of UFRGS 6274, juvenile female holotype of Liotyphlops sousai; B) Dorsal and ventral views of UFRGS 6275, juvenile male identified as Liotyphlops beui by Santos and Reis (2018). Scale bar = 5 mm.