Amphisbaena silvestrii BOULENGER, 1902
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Amphisbaena silvestrii
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| Higher Taxa | Amphisbaenidae, Amphisbaenia, Lacertoidea, Squamata (lizards) |
| Subspecies | |
| Common Names | E: Silvestri's Worm Lizard Portuguese: Cobra-de-Duas-Cabeças-Cuiabana |
| Synonym | Amphisbaena silvestrii BOULENGER 1902 Amphisbaena silvestrii — DIRKSEN & DE LA RIVA 2000 Amphisbaena silvestrii — GANS 2005: 19 |
| Distribution | Brazil (Mato Grosso), Bolivia (Santa Cruz) Type locality: Brazil; Mato Grosso, Cuyaba (= Cuiaba) (15°36’S, 56°05’W). |
| Reproduction | oviparous |
| Types | Holotype: MSNG 28308 |
| Diagnosis | Diagnosis. A form of Amphisbaena with the postrostral head shields paired, the midventral segments of each annulus broadened to twice their length and with a single pair of round precloacal pores. Specimens have 179 to 181 body annuli; 20 to 21 caudal annuli; an autotomy constriction at the 4th and 6th postcloacal annulus; 10 to 12 dorsal and 10 to 12 ventral segments to a midbody annulus; and 4 precloacal segments. Most of each animal is colored a dark brown set off by a lighter edge around each segment, the width of the edge becoming greater ventrally. The intersegmental raphes are light. The dark color drops out by segments along the chin, cloacal region, and the anterior portion of the ventral surface (Gans 1962). Notes on the type.-The specimen is well preserved with only slight fading of the color, but appears to have been cut into two pieces prior to preservation. The jagged edges of the skin fit, suggesting that nothing was lost. The agreement with the original description confirms the status of the specimen (Gans 1962). Description: Meristic characters are summarized in Table 1. Figure 3 shows views of the head, Figure 5 of the cloaca and tail, and Figure 7 photographs of the color pattern. The preserved specimens are a dark chocolate brown with the segmental margins, intersegmental raphes and anterior ventral segments completely bleached. The color is densest on the dorsal surfaces of the head and tail. The dorsal region is darker than the ventral because of the narrower light margins. The rostral tip, the chin , region, and the anterior quarter of the ventral surface are bleached. In the type the dark color also encroaches onto the ventral surface thereafter, while the Xingi6 specimen shows a more gradual invasion with occasional light colored segments or groups of segments along the midline. The Xingu specimen also has a light area around and including the cloaca. The head scalation is characterized by lack of major fusions. The first two body annuli correspond to two dorsal half-annuli. The segments of the first are commonly referred to as temporal and postocular and abut middorsally on the frontals. The second body annulus culminates dorsally in the pair of enlarged parietals. The third annulus ascends in a plane normal to the long axis and is only differentiated by a wider than normal pair of middorsal segments. The Xingu specimen shows the temporal and postlabial fused to the corresponding segments of the second body annulus, which is distinct both dorsally and ventrally to this point. The next three annuli are slightly narrowed, more so in the Cuiaba, than in the Xingui specimen. The chin is characterized by a small symphysial, very large second infralabials, large malars, two rows of postgenials, and no postmalars. The fourth, fifth, and sixth body annuli are slightly narrowed, more so in the Cuiaba than in the Xingi specimens. The body annuli are characterized by a complete lack of asymmetries so that the numbers of dorsal and ventral half-annuli are identical. The lateral sulci are clearly marked from four lengths behind the head to the cloaca. The dorsal and ventral sulci are indicated only by aligned raphes, with the ventral sulcus a common site of folding. The cloaca is preceded by four large segments. The tail is elongate, cylindrical, and terminally rounded. The autotomy constriction is expressed by a narrowed annulus of reduced diameter, posterior to which autotomy takes place. The middorsal segments are slightly longer than wide, those along the midventral line two to three times as wide as long, with considerable change from front to rear (Gans 1962). |
| Comment | Distribution: map in HOOGMOED & AVILA-PIRES 1991. Partly sympatric with A. vermicularis. Morphology: This species is one of ~20 species of Amphisbaena with two precloacal pores (Ribeiro et al. 2019). |
| Etymology | Named after Professor Dr. Filippo Silvestri (1873-1949), zoologist and entomologist. |
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