The canonical Wnt (cWnt) signaling pathway plays a prominent role in establishing the anteroposterior (AP) body axis in many bilaterians. Later, this pathway typically interacts with the Notch signaling pathway and the transcription factor Caudal to regulate posterior growth. Tardigrades have lost posterior growth and the mid-trunk region that develop by this process. Nonetheless, caudal is still expressed in the posteriormost region of the developing AP axis in the tardigrade Hypsibius exemplaris. We aimed to determine the roles, if any, of the cWnt and Notch signaling pathways during establishment of the highly compact AP axis of Tardigrada. Unlike in many bilaterians, notch and Delta, components of the Notch signaling pathway, are not expressed in a posterior domain immediately after establishment of the AP axis in H. exemplaris. These results argue against a role of the Notch signaling pathway in regulating growth of the AP axis in Tardigrada. Nonetheless, our data are consistent with a role of these genes in regulating nervous system development. However, expression of orthologs of wnt2, wnt4, and wnt16, which code for cWnt signaling ligands, are restricted to posterior regions during the earliest stage of AP axis establishment. We present a model in which the compact body plan of tardigrades evolved by conservation of the AP axis establishment function of the cWnt signaling pathway, with loss of the later acting posterior growth functions of the cWnt and Notch signaling pathways. Therefore, the AP establishment role of the cWnt signaling pathway, which operates before posterior growth intercalates a relatively large mid-trunk region in many bilaterians, may establish the entire AP axis in Tardigrada.