Leptotyphlops dulcis (Fitzinger, 1843) extant, skull length ~4mm, commonly referred to as the Texas blind snake. Other species are called threadsnakes was derived from a sister to Uropeltis and was a sister to Anomochilus.
Distinct from Uropeltis, the skull of Leptotyphlops has further reduced the maxilla and dentary. The mandible hinge is used less and the intramandibular joints are used more, unlike any other tetrapod. Kley (2001) describes it like this: "bilaterally synchronous flexions of the lower jaw serve to ratchet prey into and through the mouth." In other words, they rake their prey (ant and termite larvae) in. The quadrates are suspended via sliding articulations with the stapedes and do not articulate directly with the braincase.
See Varanus for a local family tree or go here for the more inclusive reptile family tree.