Salvadora paleolineata Holman, 1973

Jacisin Iii, John J. & Lawing, A. Michelle, 2024, Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America, Palaeontologia Electronica (a 2) 27 (1), pp. 1-42 : 16-18

Salvadora paleolineata Holman, 1973 †

Figure 8

Material. UNSM 139984 (8 pre-cloacal trunk vertebrae).

Description. The description is similar to Holman (2000) unless otherwise noted. In anterior view, the cotyle is a slightly depressed oval bookmarked by relatively large paracotylar foramen to each side. The neural canal is similar in size to the cotyle and is an inverted U-shape with medially convex sides to the neural arch. The zygosphene is dorsally convex in this view. The prezygapophyses are tilted slightly upward, and the prezygapophyseal accessory processes are well developed.

In dorsal view, the vertebra is approximately as wide as it is long. The neural spine is thin and slightly overhangs the neural arch posteriorly. The zygosphene is slightly convex anteriorly. The prezygapophyseal articular facets are subrounded, and the prezygapophyseal accessory processes are approximately two-thirds as long as the width of the prezygapophyseal articular facets and are well-developed and moderately pointed. The diapophyses are only somewhat directed laterally and are barely visible from this orientation.

In lateral view, the neural spine is delicate and is low, over three times as long as it is tall, with a slight anterior and posterior overhang. The subcentral groove is relatively deep, with dorsally convex subcentral ridges and a clear, uniform hemal keel. The condyle is tilted somewhat postero-dorsally, while the cotyle is oriented slightly antero-ventrally. The lateral foramen is positioned near the center of the vertebrae in this orientation, just below the interzygapophyseal ridge. Epizygapophyseal spines are absent.

In posterior view, the subcentral ridges are well-developed and narrow, and the hemal keel is strongly developed and uniformly thin. The postzygapophyseal articular facets are subrounded. The condyle is a slightly depressed oval. Epizygapophyseal spines are absent, as also seen in the lateral orientation.

In ventral view, the zygosphene is slightly convex anteriorly. The prezygapophyseal accessory processes are well developed. The hemal keel is uniformly thin. Both the cotyle and the condyle are oval in shape and the condyle extends to be approximately even with the postzygapophyseal articular facets.

Remarks. According to Holman (2000) and our own comparisons, the vertebrae from Penny Creek assigned to S. paleolineata are primarily from the middle trunk region, as noted by neural spines somewhat taller than in the type specimen and the larger condylar-cotylar articulation. As in Holman’s description, none of the specimens appear to have epizygapophyseal spines; as such, taxonomic assignment to S. paleolineata is possible. S. paleolineata is suggested as an ancestral species to modern Salvadora species, which differ only in possessing obsolete epizygapophyseal spines (see description of genus above; Holman, 1973). S. paleolineata also differs from Coluber and Masticophis in vertebral proportions, where the former has proportionally shorter, wider vertebrae and less dorsally convex subcentral ridges, as well as in the complete absence of epizygapophyseal spines ( Holman, 2000). Dakotaophis greeni possesses smaller zygapophyseal articular facets than S. paleolineata , and the articular facets are more elongate or oval in shape and oriented less laterally ( Holman, 2000). It is possible that, as in Heterodon /Paleoheterodon, there may be greater morphological differences in the elements of the skull, should they ever be found for this species.

Figures

FIGURE 8. Posterior trunk vertebra of Salvadora paleolineata from the Penny Creek local fauna. From top left: dorsal, ventral, anterior, posterior, and left lateral views. Scale bar equals 1 mm.