Caesoris, Sadlier & Bauer & Shea & Smith, 2015

Sadlier, Ross A., Bauer, Aaron M., Shea, Glenn M. & Smith, Sarah A., 2015, Taxonomic Resolution to the Problem of Polyphyly in the New Caledonian Scincid Lizard Genus Lioscincus (Squamata: Scincidae), Records of the Australian Museum 67 (7), pp. 207-224 : 220-221

Genus Caesoris gen. nov.

Type species. Lygosoma (Leiolopisma) novaecaledoniae Parker, 1926 , designated hereby.

Diagnosis. Maximum SVL 68 mm with a moderately elongate body, well developed limbs and digits, and relatively long tail (maximum tail length c. 200% of SVL).

Scalation ( Fig. 7 ): *no distinct supranasal; nasal scale lacking a prominent postnasal suture; frontonasal slightly broader than long; prefrontals large; frontal longer than broad; supraoculars four; *frontoparietals fused; interparietal distinct; parietals each bordered by a single nuchal and upper secondary temporal scale; primary temporal single; lower secondary temporal single; *tertiary temporals fused to form a single scale; nasals widely separated; supraciliaries usually seven; upper labials usually seven with the fifth subocular and contacting the lower eyelid; postmental contacting first and second lower labial; chinshields three, first pair in broad contact, all in contact laterally with the lower labial scales; *body scales with three moderately strong keels dorsally.

Osteology: premaxillary teeth 11; *atlantal arches of first cervical vertebrae fused to intercentrum; 29 presacral vertebrae; phalangeal formula for the manus of 2.3.4.5.3 and for the pes of 2.3.4.5.4; two pairs of mesosternal ribs.

Reproductive mode: egg laying.

Mouth lining and tongue colour: *deep blue.

The suite of apomorphic character states identified above will distinguish Caesoris gen. nov. from all other genera in the Eugongylus group of skinks, including the new genera described here. In particular, the exceptionally bright blue mouth colour of Caesoris is unique within the endemic New Caledonian skink radiation. The presence of a single large tertiary temporal scale will also serve to distinguish Caesoris from most other New Caledonian skink genera which have two tertiary temporal scales, except for Phasmasaurus (a single enlarged tertiary temporal scale occurs in most P. maruia ) and Lioscincus (a single enlarged tertiary temporal scale occurs in c. 50% of L. vivae ). The species also has an unusual toe morphology in the context of the Eugongylus group of skinks in which the basal lamellae of each toe are broadened laterally compared to those on the distal part of the toe ( Fig. 8 ), resembling the condition seen in some of the arboreal geckos in the genus Cyrtodactylus .

Etymology. Derived from the Latin for blue (caesius) and mouth (oris), in reference to the unique blue mouth colour of the type species. Gender of name based on “oris”, neuter (see Brown, 1956).

Intergeneric relationships. The study by Smith et al. (2007) was unable to identify any close relationship of the single species in Caesoris to any other genus within the Tasmantis group of skinks. In this scheme of relationships the Caesoris lineage lies outside a well-supported clade of most other endemic New Caledonian skink genera ( Nannoscincus ( Lioscincus group + Phoboscincus group + Caledoniscincus group), as does the New Caledonian Phasmasaurus lineage and the lineage that includes the New Zealand and Norfolk/Lord Howe Island genus Oligosoma . The most recent molecular phylogeny of Ineich et al. (2014) placed Caesoris as the sister to all other taxa in the Tasmantis Clade (= the endemic New Caledonian and New Zealand skinks combined), but with no support for this placement.

Among the morphological apomorphies that diagnose Caesoris , a single broad tertiary temporal scale and blue mouth lining and tongue are unique to the genus within the context of the taxa included in the endemic New Caledonian skink fauna. These two characters, in combination with a broader suite of apomorphies, serve to diagnose Caesoris from all other genera of skinks in the Tasmantis group, and support its recognition as a distinct evolutionary lineage as indicated by the genetic data.

Figures

Figure 7. Head scalation for Caesoris novaecaledoniae (adapted from Sadlier, 1987) showing the relatively plesiomorphic configuration of the majority of head scales except for the fused frontoparietal scales (FP) and single enlarged tertiary temporal scale (TT), compared to the plesiomorphic condition of paired frontoparietals seen in Epibator (Fig. 4) and two tertiary temporal scales seen inEpibator (see figure 4), Phasmasaurus (see figure 5) and Caesoris novaecaledoniae (Fig. 6).

Figure 8. Underside of the (a) manus and (b) pes of Caesoris novaecaledoniae (AMS R.90454 SVL 61 mm) showing the broad basal lamellae of all digits and markedly narrower terminal on the distal-most part of each digit, extending to approximately the junction of the 3rd and 4th plalange on the 4th toe of the pes, compared to the lamellae of the (c) manus and (d) pes of Epibator nigrofasciolatus (AMS R.177492 SVL 64 mm), also an arboreal species, which are only moderately broad basally and only extend to approximately the junction of the 1st and 2nd plalange on the 4th toe of the pes.