The typical mammalian wrist includes an elongated pisiform located between the triquetral and ulna that is formed from two ossification centers and an associated growth plate. Great apes are unusual in that the pisiform is shifted distally to articulate solely with the palmar surface of the triquetral. Humans and orangutans have also undergone pisiform reduction. In orangutans, this occurs through reduced growth preserving the secondary center, while humans have lost the primary center of ossification and growth plate entirely. Two-toed sloths, three-toed sloths, and giant anteaters (Xenarthra) have also distally shifted the pisiform to the palmar surface of the triquetral. The pisiforms of two- and three-toed sloths are also reduced similarly to humans. Using museum skeletal collections, we confirm the pisiform articulation and morphology in both families of sloths. We conducted a photographic and uCT analysis of an ontogenetic Xenarthran sample to determine the mechanisms of pisiform reduction in sloths compared to humans and orangutans. Giant anteater pisiforms follow the typical mammalian pattern of an elongate pisiform forming from two ossification centers. Both families of extant sloth form primary pisiform ossification centers, but we found no evidence of secondary ossification in either group. Instead, juvenile sloth pisiforms display an irregular subchondral surface suggesting an obliterated growth plate that allows the primary center of ossification to invade the secondary center directly. Our results further highlight the diversity of developmental pathways that can be utilized to achieve similar skeletal morphologies.