Tetrapodophis amplectus

Palci, Alessandro, Hutchinson, Mark N., Caldwell, Michael W., Smith, Krister T. & Lee, Michael S. Y., 2020, The homologies and evolutionary reduction of the pelvis and hindlimbs in snakes, with the first report of ossified pelvic vestiges in an anomalepidid (Liotyphlops beui), Zoological Journal of the Linnean Society 188, pp. 630-652 : 635

Tetrapodophis amplectus ( Fig. 2B)

This elongate squamate was described as the most basal snake ( Martill et al., 2015), but this has been disputed ( Caldwell et al., 2016; Paparella et al., 2018). Regardless of its precise phylogenetic position, it still represents a close outgroup to snakes (whether a stem snake or a dolichosaur). The pelvic region is not well preserved, but it has a slender, curved ilium and appears also to possess the other two pelvic elements. The hindlimbs are small but fully pentadactyl and consist of femur, tibia, fibula, two tarsal elements and five metatarsals and digits (digital formula 2-3-3-3-3). The long bones lack ossified epiphyses, and it is unclear whether this is attributable to young age or aquatic adaptation ( Lee et al., 2016).