Leiocephalus roquetus, Bochaton & Charles & Lenoble, 2021

Bochaton, Corentin, Charles, Laurent & Lenoble, Arnaud, 2021, Historical and fossil evidence of an extinct endemic species of Leiocephalus (Squamata: Leiocephalidae) from the Guadeloupe Islands, Zootaxa 4927 (3), pp. 383-409 : 386-389

Leiocephalus roquetus sp. nov.

Fig. 2 , 3 , 4 , 5 , 6 , 7

Diagnosis. Leiocephalus roquetus differs from all other congeners by the morphology of its parietal bone that bears adductor crests fused into a single crest in the posterior area of the bone in large specimens. In addition of this character, L. roquetus presents a unique combination of characters: absence of enlarged snout scales, and occurrence of five scales in contact with the first pair of enlarged frontal scales (pattern of type I of Pregill (1992)), the occurrence of three internasal scales, a prominent dorsal body crest, absence of keeled ventral scales, frontal bone exposed dorsally between the nasal and prefrontal bones, skull rugosities on the frontal bone, premaxillary spine constricted just above the dentigerous process, a well-developed posterior process of the septomaxilla, a distinct dorsal process of the squamosal, a well-developed angular process of the dentary, and transition from bicuspid to tricuspid teeth occurs between the height and sixth most anterior dental position of the dentary. This new taxon also presents several differences with other known Lesser Antillean Leiocephalus specimens (see below).

Derivatio nominis: The species is named in reference to the first common name “roquet” attributed by Du Tertre (1654) and de Rochefort (1658) to the leiocephalid lizards of Guadeloupe. As pointed out by Breuil (2002), this name was latter erroneously attributed to Anolis lizards and, as the Amerindian name of Leiocephalus is unknown, we choose to retain the original name given to these squamates. The English name of this lizard would be “Curlytail roquet” and the French name “Léiocéphale roquet”.

Type locality: Guadeloupe,? La Désirade Island , Lesser Antilles .

General description of the holotype. The holotype is a complete, dry taxidermy specimen (labeled MHNBx 2002.1871) preserved in the Natural History Museum of Bordeaux ( France). This specimen has a snout-vent length (SVL) of 10.8 cm and measures 26.5 cm in total length ( Fig. 2 ). Microtomography reveals the skull to be fully preserved ( Fig. 3 ). The key morphological features of the holotype are as follows: enlarged nasal bones, the narrow nasal process of the premaxilla is triangular, the dorsal part of the premaxilla is fully enclosed by the nasal bones, the premaxilla lacks lateral spines and bears 7 tooth positions, the nasal-maxillary suture is arched toward the midline of the snout, the nasal process of the frontal bone is dorsally exposed between the nasal and prefrontal bones, the pterygoid bears teeth but palatine teeth are absent, lacrimal and postfrontal bones are present, the septomaxilla bears a quadrangular lateral wing with a thin posteriorly oriented process, the frontal is narrow with dermal ornamentation, the parietal foramen is on the fronto-parietal suture, the adductor crests of the parietal table converge but do not touch and are posteriorly separated by a depressed area, the anterior part of the parietal table presents a dermal ornamentation, the supratemporal bone is on the lateral side of the supratemporal process of the parietal, the supratemporal process of the squamosal is distinct, splenial and angular bones are present, the angular process of the dentary is well-developed, most of the teeth are tricuspid and distinctively flared, the transition from monocuspid/bicuspid to tricuspid teeth occurs at the seventh dental position on the dentary and at the fourth dental position on the maxilla. Head scales are large, the specimen presents four rows of snout scales of sub-equal size between the internasal and the anterior pair of frontal scales, there are four moderately-sized parietal scales and the most lateral scales are smaller than the median scales, two rows of post parietal scales are present, there is no enlarged lateral post-parietal scale, there are three internasal scales, there are four lorilabial scales anterior to the first lorilabial contacting the elongated sub-ocular scale, the cephalic scales lack ridges, the temporal scales are of sub-equal size and no elongated temporal scales are present, the lateral nuchal scales are smaller than surrounding body scales, the lateral body scales are the same size as dorsal and ventral scales, a prominent middorsal body crest formed by overlapping scales is present, the dorsal crest (occiput to vent) is composed of 53 scales, the tricarnate scales at the base of the first and second toes grow into comb-like fringes but are not prominent, the venter is dull and patternless, there is no scapular patch, no suprascapular blotches, no facial band, and the base of tail is laterally compressed.

Description of paratype fossil bones and corresponding bones of the holotype. In addition to the holotype dry specimen, we associate, as paratypes, several fossil bones collected from the Pointe Gros Rempart 6 deposit to the type series of L. roquetus . These bones are described below in association with corresponding bones of the holotype specimen in order to demonstrate that both modern and fossil materials correspond to the same taxon.

Figures

FIGURE 2. Dorsal (A) and ventral (B) views of the complete holotype specimen of Leiocephalus roquetus sp. nov. (MHNBx 2002.1871). Scale bar= 5 mm.

FIGURE 3. Head and skull of the Holotype of Leiocephalus roquetus sp. nov. (MHNBx 2002.1871).A, B: Picture and drawing of the dorsal scales of the head of the Holotype; C, D: Picture and drawing of the lateral scales of the head of the Holotype; E, F: Dorsal and lateral views of the 3D model of the skull of the holotype; G: Labial and lingual views of the 3D model of the right mandible of the holotype. Scale bars= 3 mm.

FIGURE 4. Premaxilla and maxilla of Leiocephalus roquetus sp. nov. A: 3D Model of the premaxilla of the holotype (MHNBx 2002.1871); B: Paratype “PGR6. square C11c. décapage 14.XII” collected in PGR6 deposit. C: 3D Model of the right maxilla of the holotype (MHNBx 2002.1871); D: Paratype “PGR6. square B10d. décapage 22.III” (right) collected in PGR6 deposit. Abbreviations: c. i. p. p.: crest of the internal premaxillary process, e. p. p.: external premaxillary process, f. p.: facial process, f. t. t.: first most anterior tricuspid tooth, i. m.: imprint of the maxilla, i. n.: imprint of the nasal bone, i. p.: incisive process, i. p. p.: internal premaxillary process, m. p.: maxillary process, n. p.: nasal process, p. f.: premaxillary fenestra, s. s.: supradental shelf, z. p.: zygomatic process. Scale bars= 2mm.

FIGURE 5. Frontal and parietal bones of Leiocephalus roquetus sp. nov. A: 3D Model of the frontal bone of the holotype (MHNBx 2002.1871); B: Paratype frontal bone “PGR6. square B10d. décapage 13.IV” collected in PGR6 deposit; C: Paratype frontal bone “PGR6. square B10d. décapage 13.V” collected in PGR6 deposit; D: 3D Model of the parietal bone of the holotype (MHNBx 2002.1871); E: Paratype parietal bone “PGR6. square C11d. décapage 12.VI” collected in PGR6 deposit; F: Paratype parietal bone “PGR6. square B9b. décapage 22.VII” collected in PGR6 deposit.Abbreviations: a. c.: adductor crest, c. c.: cranial crest, d. o.: dermal ornamentation, f-p. s.: fronto-parietal suture, i. n.: imprint of the nasal bone, i. pr.: imprint of the prefrontal bone, i. ps.: imprint of the postfrontal bone, i. s.: imprint of the supratemporal bone, n. c.: nasal process crest, n. f.: nuchal fossa, pa. f.: parietal fossa, p. d.: postero-medial depression, p. f.: parietal foramen, s. p.: supratemporal process. Scale bars= 2mm.

FIGURE 6. Pterygoid, squamosal and quadrate bones of Leiocephalus roquetus sp. nov. A: 3D Model of the right pterygoid of the holotype (MHNBx 2002.1871); B: Paratype left pterygoid bone “PGR6. square C11d. décapage 14.X” collected PGR6 deposit; C: 3D Model of the right squamosal of the holotype (MHNBx 2002.1871); D: Paratype left squamosal bone “PGR6. square B9b. décapage 22.IX” collected in PGR6 deposit; E: 3D Model of the left quadrate of the holotype (MHNBx 2002.1871); F: Paratype left quadrate bone “PGR6. square C11c. décapage 15.XI” collected in PGR6 deposit. Abbreviations: a.-d. d.: antero dorsal depression, a. e.: articular surface with the ectopterygoid bone, a. p.: articular surface with the palatine bone, a. r.: anterior ramus, c.: conch, d. p.: dorsal process, p. c.: posterior crest, p. e.: pit for the insertion of the epipterygoid, p. l.: pterygoid lamina, p. t.: pterygoid teeth?, pa. p.: palatine process, po. p.: posterior process, t. c.: tympanic crest, t. p.: transverse process, t. s.: tooth socket, v. p.: ventral process. Scale bars= 2mm.

FIGURE 7. Dentary, articular bones and vertebrae of Leiocephalus roquetus sp. nov. A: 3D Model of the right dentary of the holotype (MHNBx 2002.1871); B: Paratype dentary “PGR6. square C11d. décapage 16.I” (left) collected in PGR6 deposit; C: Paratype dentary “PGR6. square C11c. décapage 11.II” (left) collected in PGR6 deposit; D: 3D Model of the right articular of the holotype (MHNBx 2002.1871); E: Paratype articular “PGR6. square B9b. décapage 17.VIII” (rigth) collected in PGR6 deposit; F: Anterior trunk vertebra collected in the layer 4 of PGR6 (square B10d, décapage 20); G: Caudal vertebra collected in the layer 2/3 of PGR6 (square B10d, décapage 10). Abbreviations: a. p.: angular process, c. p.: coronoid process, f. t. t.: first most anterior tricuspid tooth, hy.: hypapophysis, i. c.: lateral imprint of the coronoid bone, i. s.: intra-mandibular septum, m. s.: medial spine, n. s.: neural spine, o. M. g.: anterior opening of the Meckelian groove, r. p.: retroarticular process, s.: symphysis, sy.: synapophysis, s. p.: surangular process. Scale bars=2 mm.