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Cenaspis aenigma CAMPBELL, SMITH & HALL, 2018

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Higher TaxaColubridae (Dipsadinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)
Common Names 
SynonymCenaspis aenigma CAMPBELL, SMITH & HALL 2018 
DistributionMexico (Chiapas)

Type locality: ‘‘La Loma,’’ located some 20–25 km (by road) W-NW of Rizo de Oro (sometimes known as Nueva Tenochtitlán), Chiapas, Mexico. Access is gained into this region by means of a logging road connecting Rizo de Oro with Colonia Rodulfo Figueroa; the latter is a small settlement very near the border with Oaxaca. The type locality lies to the N-NW of Colonia Rodulfo Figueroa on the western slopes of Cerro El Baúl, the highest peak in the region, rising to an elevation of 2,050 m  
TypesHolotype. UTA R-10544, an adult male. Collected by the late Julio Ornelas-Mart ́ınez on 6 July 1976. 
DiagnosisDiagnosis (Genus): This genus differs from all other New World dipsadids by two unique features: 1) all subcaudals undivided and 2) hemipenis single, noncapitate, hemipenial body and apical region completely covered with calyces, and sulcus spermaticus simple. Rhinocheilus is the only other American colubroid north of Panama having undivided sub- caudals, distinguished from Cenaspis in always having at least a few divided subcaudals, preocular present, dorsals in 23 rows at mid-body and reduced to 19 posteriorly, and a reddish and black pattern with dorsal blotches or bands. Although some other New World genera have single hemipenes, in every case of which we are aware, the hemipenial body bears spines or spinules (vs. calyces), there usually is distinct capitation, and the sulcus spermaticus is bifurcate for much of the length of the capitulum (Tables 1, 2).

Diagnosis. Differs from other Middle American genera of dipsadids except Adelphicos, Atractus, Chapinophis, Chersodromus, Geophis, Ninia, some Sibon in having prefrontal enter orbit. Chersodromus and Ninia (characters for Cenaspis aenigma in parentheses) have keeled (vs. smooth) dorsal scales; Adelphicos and Sibon have ? 15 (vs. 17) dorsal scale rows at mid-body; Atractus, Chersodromus, Geophis, and Sibon have 1 + 2 or 0 + 1 (vs. 1 + 1) temporals; Adelphicos, Chapinophis, and Geophis usually have ? 7 (vs. 8) supralabials; and Adelphicos, Chapinophis, and Trimetopon have a divided cloacal scute (vs. undivided) (Tables 1, 2). For additional characteristics see diagnosis for genus.

Comparison with Other Middle American Taxa.—About half of the genera of Dipsadidae have a preocular contacting the supra-ocular, precluding contact of the prefrontal with the orbit (Table 1). When the preocular is absent as in Cenaspis, Adelphicos, Atractus, Chapinophis, Chersodromus, Enuliophis, Enulius, Geophis, Ninia, Omoadipsas, and some Sibon, the prefrontal enters the eye. Associated with this trait is a single, horizontally elongate loreal between the nasal(s) and orbit. Most often small burrowing or terrestrial Dipsadidae have 15 to 17 rows of smooth dorsal scales at mid-body and these are unreduced posteriorly; exceptions are Chersodromus and Ninia, which have keeled scales. Genera with 19 or more scale rows at mid-body (Coniophanes, Cryophis, Eridaphas, Hypsiglena, Leptodeira, Pseudoleptodeira, Rhadinophanes, and Tretanorhinus) generally have scale-row reductions on the posterior of the body.
Few other Middle American snakes possess a ventral pattern resembling that of Cenaspis aenigma. The venter is immaculate in most species, although colors may grade into different hues from anterior to posterior of body, and often the dorsal coloration encroaches on the lateral edges of ventrals. Con- iophanes quinquevittatus and Coniophanes bipunctatus have dis- tinct dark round spots near the outer edge of each ventral and the midventer is unmarked. Ninia diademata frequently has three regular series of dark markings on the ventrals: a series is present on the lateral portion of each ventral and a large well- formed roundish to triangular spot midventrally. Unlike Cenaspis aenigma, in which the markings in all series are approximately the same size and shape, in N. diademata the midventral series is conspicuously larger and differently shaped from the lateral series (Burger and Werler, 1954). Ninia maculata and Ninia psephota usually have dark ventral markings that may variably be in a single midventral series, two series near lateral edges of ventrals, or as an irregular checkerboard, but rarely dark markings are arranged in more-or-less three series (lateral and midventral), although in irregular lines (Smith and Camp- bell, 1996; Savage, 2002).
Many genera of the Dipsadidae have two enlarged teeth on the posterior of the maxilla that may be grooved and often set off from more anterior teeth by a diastema (e.g., Amastridium, Coniophanes, Imantodes, Leptodeira, Tantalophis; Table 2). In Cenaspis 14–15 maxillary teeth appear to decrease in size posteriorly (on the basis of tooth socket size) and no diastema or enlarged grooved teeth are present (Figs. 5, 6). Fewer maxillary teeth characterize Adelphicos (7–11), Atractus (5–11), Chapinophis (12), and Chersodromus (7–9), whereas more teeth are present in Ninia (15–18) and Tretanorhinus (27–30). Species of Geophis differ by having relatively longer, sharper, more slender teeth in contrast to the short, stout, and blunt teeth in Cenaspis.
The ectopterygoid is slenderer in Geophis than in Cenaspis and usually less forked; only in some species in the Geophis mutitorques group does bifurcation of the anterior end with lateral anterior branch of the ectopterygoid approach the condition seen in Cenaspis.
Numerous other osteological features distinguish various species of dipsadids from C. aenigma. In Adelphicos latifasciatus, the prefrontal has two (middle and lower) distinctive forward processes, a more strongly defined dorsolateral parietal ridge, no foramen in the quadrate, and 10–11 short, stout maxillary teeth. Adelphicos quadrivirgata (Figs. 6D,E,F) is similar to A. latifasciatus except there is only a single middle forward prefrontal process (middle; Fig. 5E). In Amastridium veliferum the braincase is shorter; the postocular is narrow dorsally, becoming heavy at midlength, continuing to ventral end; and there are 13–14 + 2 maxillary teeth (enlarged, diastema present). Atractus lancini and A. univittatus have 11–14 long, sharp maxillary teeth, becoming smaller posteriorly; the prefrontal has an anteriorly projecting flange. There are 11 long, robust maxillary teeth, becoming smaller posteriorly in Chapinophis xanthocheilus; the postocular is stout, the prefrontal has a middle anterior projection, the anterior edge of frontal has median projections, and the prefrontal distinctly curves over the dorsum of skull. Chersodromus liebmanni has a relatively short braincase, a strong dorsolateral ridge is present on parietals, postoculars are absent, the prefrontal has three forward projections, and almost the anterior third of the maxilla is edentate, followed by about nine long needlelike teeth. Coniophanes imperialis has a short braincase, the prefontals have a large forward flange, the dorsolateral ridge on parietal is well developed, the supra- temporal extends forward to almost the parietal, and the maxilla has 11–12 + 2 teeth that are posteriorly enlarged and grooved, separated by a diastema from more anterior teeth. Conophis vittatus has a short braincase; a postocular is present but not contacting frontal, the quadrate is relatively long and slender, the prefrontal has a forward-projecting flange, the maxilla bears 10 + 3 teeth with posterior teeth greatly enlarged and grooved, and a diastema is present. In Cryophis hallbergi the premaxilla does not reach the nasals, the prefrontals have a broad forward projecting flange, the postorbital does not reach the frontal, the supratabular extends forward to the parietal, the maxilla bears 21 + 2 teeth with posterior teeth enlarged and grooved, and a narrow diastema is present. Diadophis punctatus has a prefrontal with a middle forward-projecting process, the dorsolateral ridge of the parietal is well developed, the supratabular extends forward on to the parietal, the maxilla bears 8–9 + 2 teeth with posterior teeth enlarged, and a diastema is present. In Ficimia publia, the premaxilla is distinctly forward projecting, the prefrontal has single large anterior projection, and the maxilla bears 12–13 short stout teeth. In Geagras redimitus, (a small burrowing Mexican colubrid), the premaxillary is produced forward with a knoblike process that projects upward and forward; the nasal, frontal, and parietal bones have no or little space between them with mostly tight sutures; the quadrate is exceptionally broad, and the maxillary bears 10–11 short, stout teeth. In Geophis anocularis, the premaxilla slopes forward; the nasals, frontals, and parietals are in tight juxtaposition, with no dorsolateral parietal ridge; the frontal forms only a small portion of the orbital socket; no postorbital is present; the quadrate relatively small but expanded dorsally, and the nasals are roughly triangular. In G. laticinctus, the premaxillary is rounded in lateral view; the nasals and frontals are widely separated; the parietal ridge is laterally located; and the maxillary teeth moderately long and stout, decreasing in size posteriorly. In Rhadinaea, the nasals are small, widely separated from the frontals; the postorbital does not contact prefrontals, and the prefrontal is distinctly higher than long. In Sibon and Tropidodipsas, the nasals are widely separated from the frontals, the prefrontal is distinctly higher than long, the postorbital is long and delicate, the dorsolateral ridge of the parietal is well developed, and the quadrate is well developed and robust, with a broadly expanded superior end.
Hemipenes in species of dipsadids often are single or bilobed with a bifurcate sulcus spermaticus, capitate calyculate orna- mention on distal portion of lobes, and spines or spinules on hemipenial body and sometimes basal portion of lobes (Fig. 7A,C,D). Genera having a single subcyindrical organ include Adelphicos, Amastridium, Cryophis, Imantodes, Leptodeira, Ninia, Rhadinaea, Tropidodipsas, and others (see Table 2), but most of these genera are characterized by a distinctive calyculate apical portion of the hemipenis, which is usually differentiated into a distinct capitulum with a bifurcate sulcus spermaticus. Besides having a single organ, Adelphicos (Fig. 7), Eridiphas, Hypsiglena, Imantodes, Leptodeira, and Pseudoleptodeira have a simple (not bifurcate) sulcus spermaticus, but these genera differ from Cenaspis by having a spinous hemipenial body and some capitation evident. 
CommentAbundance: only known from the holotype, which was found in the stomach of a Micrurus nigrocinctus.

Type species: Cenaspis aenigma CAMPBELL, SMITH & HALL 2018 is the type species of the genus Cenaspis CAMPBELL, SMITH & HALL 2018. 
EtymologyThe generic name is derived from the Latin cena, meaning dinner, and aspis, meaning a kind of snake, in reference to predation on the single known individual of this snake. The name taken literally means ‘‘dinner snake.’’
The species name is derived from the Latin “aenigma” meaning a riddle or mystery. 
  • Aguilar-López JL, Luría-Manzano R, Pineda E, Canseco-Márquez L 2021. Selva Zoque, Mexico: an important Mesoamerican tropical region for reptile species diversity and conservation. ZooKeys 1054: 127-153 - get paper here
  • Campbell, Jonathan A.; Eric N. Smith, and Alexander S. Hall 2018. Caudals and Calyces: The Curious Case of a Consumed Chiapan Colubroid. Journal of Herpetology 52 (4): 458-471. - get paper here
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