Lampropeltis similis Holman 1964

Lampropeltis similis Holman, 1964 †

Figure 6

Material. UNSM 139982 (14 pre-cloacal trunk vertebrae).

Description. In anterior view, the neural arch is moderately vaulted. The cotyle is a depressed oval bordered by deeply excavated pits, and is slightly larger than the ventrally restricted, inverted Ushaped neural canal. The zygosphene curves dorsally, and the prezygapophyseal articular facets tilt slightly upward. The diapophyses and parapophyses are distinct elements of the parapophyses, with the latter portion more distally pointed than the former; however, they are not as clearly separated as in most other colubrids.

In dorsal view, the vertebrae are approximately as long as they are wide at the prezygapophyses, and the width at the well-developed, rounded prezygapophyseal accessory processes is greater than it is long through the zygapophyses. The neural spine tilts slightly ventrally in its anterior portion. The prezygapophyseal articular facets are oval to ovoid and slightly tilted upward. The epizygapophyseal spines are absent. The anterior edge of the zygosphene is slightly convex to slightly sinuate; the posterior notch of the zygosphene is Vshaped.

In lateral view, the neural spine is significantly longer than it is tall, and dips slightly downward cranially. The hemal keel is visible and quite strong.

In posterior view, the neural arch is moderately vaulted, and the condyle is a dorso-ventrally depressed oval.

In ventral view, the strong hemal keel is spatulate or oblong in shape, but not wide throughout most of its length. Subcentral ridges are present and concave from below, but not exceptionally developed. The postzygapophyseal articular facets are ovoid.

Remarks. These vertebrae in particular appear to be more similar to the general morphology of the milksnakes of the Lampropeltis triangulum complex or the kingsnake Lampropeltis calligaster as opposed to the L. alterna or L. pyromelana-zonata groupings. They possess long neural spines, moderately depressed neural arches, distinct hemal keels with deep subcentral grooves, and robust, distinct subcentral ridges (Parmley, 1990; Parmley and Hunter, 2010). More specifically, L. similis has previously been described as similar in appearance to L. triangulum; however, L. similis possesses a less depressed neural arch in the trunk region (more similar to that of L. calligaster) with an inverse U-shaped rather than depressed ovoidshaped neural canal, a thinner hemal keel. Holman (2000) also stated a centrum that “is not as triangular from below” as an additional apomorphy for L. similis, but we are unable to confirm this as a consistent character throughout the vertebral column of the species.