Platyspondylia Rage 1974
Makaleler > Tam Makale · 2021
Yazarlar: Georgalis, Georgios L., Čerňanský, Andrej, Serdar MAYDA
, Uluslararası, 2021
Özet
Genus Platyspondylia Rage, 1974 cf. Platyspondylia sp. (Fig. 12) MATERIAL. — Turkey. Kargi 2: a cloacal vertebra (EUNMH PV 14070). DESCRIPTION The vertebra EUNMH PV 14070 is almost complete but misses most of its lymphapophyses and the posteroventral portion of its centrum (Fig. 12). The vertebra is small, with a neural arch width of 1.9 mm and an approximate centrum length of at least 1.3 mm (the posterior ventral portion of the centrum is damaged). In anterior view (Fig. 12A), the zygosphene is thin and slightly convex. Its width is larger than that of the cotyle. The neural canal is moderately large and trapezoidal. The prezygapophyses are only slightly dorsally inclined, with their dorsalmost edges slightly exceeding the dorsal level of the cotyle. The cotyle is rather small and almost totally circular. There are no paracotylar foramina. Large and relatively deep paracotylar fossae are located at each side of the cotyle. From the lymphapophyses, only their bases are preserved, but still it can be observed that they were broad and directed ventrolaterally. In posterior view (Fig. 12B), the neural spine is thick and rather short. The neural arch is relatively vaulted and is distinctly upswept above the zygantrum, with a prominent angle occurring at about mid-length of each postzygapophysis. The condyle is much eroded, though it seems that, similarly to the cotyle, it was rather small and distinctly circular. In dorsal view (Fig. 12D), the base of the neural spine is developed only at the posterior half of the neural arch; its thickness augments gradually towards its posterior direction. The zygosphene is trilobate, with all three lobes being rather prominent. The interzygapophyseal constriction is deep. The prezygapophyses face anterolaterally. The prezygapophyseal articular facets are slender and elongated. The posterior median notch of the neural arch is shallow. In ventral view (Fig. 12E), the centrum is much wider than long. A thin, salient structure is developed in the (preserved) midline of the centrum that probably corresponds to the remains of a hypapophysis. The postzygapophyseal articular facets are broad and oval. In lateral view (Fig. 12C, F), the vertebra is distinctly higher than long. The neural spine develops only at the posterior portion of the neural arch; it is relatively short and is distinctly posteriorly inclined. The zygosphenal facets are broad. The (probable) hypapophysis slightly projects ventrally. COMMENTS The vertebra can be tentatively referred to Platyspondylia on the basis of its very tiny size, the distinctly thin zygosphene, the low neural spine commencing well posteriorly from the level of the zygosphene and developed mostly at the posterior portion of the neural arch, the deep interzygapophyseal constriction, the very slender prezygapophyses, the tiny and circular cotyle and condyle, the shallow posterior median notch, and not well developed prezygapophyseal accessory processes (see figures in Rage 1974; Szyndlar & Rage 2003; Vianey-Liaud et al. 2014). Furthermore, the presence of lymphapophyses, the absence of haemapophyses and the probable presence of a hypapophysis, and the relatively vaulted neural arch, denote that the vertebra originates from the cloacal region (Szyndlar & Rage 2003; Vianey-Liaud et al. 2014). In fact, this specimen bears resemblance with the sole other known cloacal vertebra of that genus that has been figured so far, i.e., a referred specimen of Platyspondylia lepta Rage, 1974, from the late Oligocene (MP 28) of Pech Desse, Quercy, France (see Szyndlar & Rage 2003: fig. 37i-m), though still it possesses a much more posteriorly inclined neural spine in lateral view and a more vaulted neural arch. As for the probable presence of the hypapophysis, it is known that several extinct and extant constrictors are known to possess such structure in their anterior cloacal vertebrae, such as Bavarioboa and the Neotropical ungaliophiines (Szyndlar & Rage 2003; Smith 2013). Compared to cloacal vertebrae of Falseryx, the Kargi 2 specimen EUNMH PV 14070 is distinct in the vaultness of the neural arch with a distinctive upswept above the zygantrum, the neural spine developing more posteriorly on the neural arch, the broader and anteroposteriorly shorter centrum, and the wider and more prominent zygosphene (see figures in Szyndlar & Rage 2003; Szyndlar et al. 2008; Syromyatnikova et al. 2019a). Finally, compared with cloacal vertebrae of Bavarioboa Szyndlar & Schleich, 1993, a genus from Western and Central Europe (see figures in Szyndlar & Rage 2003), that has been recently recovered also from Anatolia (Szyndlar & Hoşgör 2012; Syromyatnikova et al. 2019a), EUNMH PV 14070 is much smaller, has no paracotylar foramina, and neural spine commencing well posteriorly on the neural arch (see figures in Szyndlar & Rage 2003). Taking the above notices in consideration, we choose to treat EUNMH PV 14070 as pertaining to a second “tropidophiid” taxon, with more close probable affinities with Platyspondylia than Falseryx. Whether it truly belongs to the otherwise western and central European genus Platyspondylia or represents a totally novel taxon, is a question that certainly requires more material recovered from the Anatolian Oligocene.