Molecular and morphological baraminology of Xenarthra

There are 31 xenarthran species living today, made up of armadillos, anteaters, and sloths. These animals are characterized by a narrow, elongated skull and a unique vertebral process in the posterior trunk. Xenarthra represents an apobaramin within which several holobaramins may be discerned, using both mitochondrial DNA and morphological data.

The morphological results show that there are two armadillo holobaramins. The first group is made up of genera, such as Dasypus, Tolypeutes, Kuntinaru, Stegotherium, Priodontes, and Cabassous. The other group consists of the genera Peltephilus, Vassallia, Propalaeohoplophorus, Eutatus, Chlamyphorus, Zaedyus, Prozaedyus, Paleuphractus, Macroeuphractus, Doellotatus, Proeutatus, Euphractus, and Chaetophractus. The mitochondrial DNA show that Cabassous and Tolypeutes separate from Dasypus, however, this may be due to the fragmentary nature of the mitochondrial genome.

There appears to be only a single Vermilingua holobaramin, consisting of the genera Tamandua, Myrmecophaga, and Cyclopes. This can be seen based on the mitochondrial DNA results. However, Tamandua lacks continuity with armadillos based on morphological evidence, although it does not show clear discontinuity with them.

When looking at sloths, it appears that there may be one or several groups. The two extant genera, Bradypus and Choloepus are tree sloths, which might be separate from ground sloths due to their locomotion, although there is no decisive evidence for discontinuity between tree and ground sloths. On a molecular level, however, all sloths share a number of ‘sloth endogenized foamy-like retroviruses’, which unite them. Furthermore, the dental formula of 5+4 upper and lower teeth are generally characteristic of all sloths.