Ungaliophis Mueller , 1880

Szyndlar, Zbigniew & Georgalis, Georgios L., 2023, An illustrated atlas of the vertebral morphology of extant non-caenophidian snakes, with special emphasis on the cloacal and caudal portions of the column, Vertebrate Zoology 73, pp. 717-886 : 717

Ungaliophis Mueller, 1880

Material examined.

Ungaliophis continentalis Müller, 1880 (UMMZ 190698).

Description (Figs 124-127).

Trunk vertebrae. Centrum as long as wide (but probably due to the juvenile / subadult ontogenetic stage of the individual); cotyle and condyle slightly depressed; neural arch slightly depressed; posterior median notch of the neural arch deep; neural spine of medium height, located at the posterior half of the neural arch; prezygapophyseal accessory processes vestigial to short; hypapophyses disappearing posteriorly to V 50; haemal keel indistinct (but probably due to the juvenile stage of the specimen); paracotylar foramina absent.

Note that the skeleton described above belonged (as indicated among other features by its very small absolute dimensions and relatively broad neural canal) to a subadult specimen and this is the reason of the relative shortness of its vertebrae. Nevertheless, the few published figures of Ungaliophis vertebrae already attest the dependence of the elongation of the centrum to ontogeny: the trunk vertebrae of Ungaliophis continentalis and Ungaliophis panamensis Schmidt, 1933, illustrated by Bogert (1968a: figs 9B and 8A, respectively), that are characterized by elongate centra, apparently represented adult snakes. Indeed, a juvenile female of U. panamensis figured by Bogert (1968b: fig. 7A) possesses a shorter centrum. Furthermore, according again to Bogert (1968a), the shape and prominence of the haemal keel of the trunk vertebrae of Ungaliophis spp. is also subjected to variation: it can be discernible in large (>600 mm in total length) individuals but almost invisible in smaller individuals of U. panamensis , and it was almost absent in one adult individual of U. continentalis . In any case, caution should be paid when interpreting these terminologies, as Bogert (1968a) could have a different sense of the term haemal keel, confined perhaps solely to dorsoventrally high structures, judging from a posterior trunk vertebra with a wide haemal keel ( Bogert 1968a: fig. 11) that in the caption he described as showing the "absence of any trace of the haemal keel".

Trunk / caudal transition. A short hypapophysis is present in the last trunk and (gradually diminishing in size) in cloacal vertebrae. In caudal vertebrae, this is replaced by a distinct (although moderately developed) haemal keel; the keel disappears in the last caudal vertebrae.

Number of vertebrae. Ungaliophis continentalis (UMMZ 190698): 275 (224+3+48) including a final fusion.

Data from literature and unpublished data from personal communications: Ungaliophis continentalis : 238 trunk vertebrae plus 50 cloacal and caudal vertebrae plus a final fusion (NMNH 344819; Krister Smith, unpublished data, personal communication to GLG); Ungaliophis panamensis : 255 trunk vertebrae plus 49 cloacal and caudal vertebrae plus a final fusion (NMNH 209215; Krister Smith, unpublished data, personal communication to GLG).