Lycodon rufozonatum Cantor, 1842

Lin, Chien-Hsiang, Lin, Si-Min, Chien, Chi-Wei, Lin, Te-En, Nazir, Haroon & Singh, Ningthoujam Premjit, 2025, First fossil frog and snake assemblage from southern Taiwan: a window into Pleistocene herpetofauna and palaeoenvironments in subtropical East Asia, Fossil Record 28 (2), pp. 293-308 : 293-308

Lycodon rufozonatum Cantor, 1842

Fig. 3 A, B

Material.

Two trunk vertebrae ( ASIZF 0101048 –1049).

Description.

In anterior view, the cotyle is rounded in outline. Paracotylar foramina are present on either side of the cotyle. The prezygapophyses are well-developed, and the prezygapophyseal accessory processes are laterally extended. The zygosphene roof is thin and dorsally convex. The zygosphenal articular facets of the zygosphene are inclined dorsally. The neural canal is tunnel-like, with a width approximately equal to that of the cotyle.

In posterior view, the condyle is circular in shape and proportionally similar in height and width. The neural arch is extremely depressed to depressed (vaulting ratio = 0.19–0.23). The zygantral area is deep and contains paired endozygantral foramina.

In ventral view, the centrum is triangular and relatively short. Small paired subcentral foramina are visible flanking a well-developed, oblanceolate haemal keel that extends nearly to the condyle. Subcentral grooves are deep and long. Postzygapophyseal articular facets are oval. Synapophyses are clearly divided into diapophyses and parapophyses, with the absence of parapophyseal processes.

In dorsal view, the vertebrae are slightly wider than long. The anterior margin of the zygosphene is straight with two blunt lobes on the lateral sides. The posterior median notch is distinct and deep. Prezygapophyseal articular facets are oval.

In lateral view, both interzygapophyseal and subcentral ridges are straight. The neural spine is high, with the posterior end protruding above its base and the anterior end overhanging. Lateral foramina are present.

Remarks.

The two trunk vertebrae differ from those of Ptyas by lacking epizygapophyseal spines ( Ikeda 2007; Nakamura et al. 2013). Additionally, several features, including the straight zygosphenal lip with two small blunt lobes on the lateral sides, exclude their allocation to Coronella , which possesses a crenate zygosphenal lip, and a wide haemal keel ( Ivanov et al. 2018). The fossils can also be distinguished from Texasophis and Telescopus by their relatively large size and distinct subcentral ridges ( Szyndlar 1987, 2005; Čerňanský et al. 2017).

The fossil vertebrae also closely resemble those of Elaphe and Lycodon , sharing characters including undeveloped parapophyseal process, well-developedprezygapophyseal accessory processes, and oval zygosphenal articular facets ( Chen 2020). However, in Elaphe , the trunk vertebrae generally exhibit less prominent subcentral ridges and indistinctly developed subcentral grooves ( Ratnikov 2004; Ivanov et al. 2018), which is not identical to the prominent subcentral ridges and deep subcentral grooves in the fossils, although Ratnikov (2022) noted that Elaphe trunk vertebrae show progressive morphological changes along the column, such as deepening of subcentral grooves, more distinct subcentral ridges, reduced haemal keel width, and increased neural spine height posteriorly.

Two extant species of Lycodon , Lycodon ruhstrati (Fischer, 1886) and Lycodon rufozonatus ( Cantor, 1842) , are found in Taiwan. The vertebrae of L. ruhstrati possess flat and very low neural spines, whereas in L. rufozonatus , these are substantially high as in our fossils (Fig. 3 C, D ).

Figures

Figure 3. A, B. Lycodon rufozonatum (ASIZF 0101048–1049) from the Middle Pleistocene Chiting Formation, southern Taiwan; C. Extant specimen of L. rufozonatum (ASIZRE 000007), 94 th trunk vertebra, 74.2 cm TL (total length), 55.6 cm SVL (snout – vent length), 102 g. D. Extant specimen of Lycodon ruhstrati (ASIZRE 000005), 31 st trunk vertebra, 71.8 cm TL, 53.2 cm SVL, 18 g. A 1 – D 1. Anterior view; A 2 – D 2. Posterior view; A 3 – D 3. Ventral view; A 4 – D 4. Dorsal view; A 5 – D 5. Lateral view. Scale bar: 5 mm.