The Antlion is a Badnik that appears only in a cutscene that is played during the credits of Sonic the Hedgehog CD. The Badnik attacks Sonic the Hedgehog after he falls into a pit from a break-away floor, who narrowly escapes the robot's huge jaws. The setting it appears in seems to be a ruinous one. This Badnik originally only appeared in the unlockable Pencil Test, but a colored animation was included in the credits sequence of Sonic Jam, Sonic Mega Collection and the 2011 digital re-release of Sonic CD.
There is the possibility that the ruinous setting this Badnik is located in is the missing R2, due to the fact that all rounds are shown in the credits. It is also possible that it is supposed to be a concept of Tidal Tempest, as that is the only round otherwise not represented in the roundup.
This Badnik is confirmed to have been considered for R2 or R8, according to assets released by Christian Whitehead. It is unknown if the Antlion would have been in both levels, or if it was planned for R8 after R2 was scrapped. Enemy graphics are one of the few things remaining from R2's original development.