Harpagolestes uintensis is a mesonychid. Harpagolestes macrocephalus is not.

Welcome to the wonderful world of convergence!
Harpagolestes uintensis (Fig. 2) and H. macrocephalus (Fig. 1) look similar enough to be considered similar, but they are not congeneric in the LRT. One of them needs a new generic name.

Of the several heresies
recovered by the large reptile tree (LRT, 1120 taxa) the latest is the separation of some former mesonychids (Fig. 1, Andrewsarchus, Sinonyx, Hapalodectes) from current and traditional mesonychids (Fig. 2, Mesonyx and Harpagolestes uintensis). The clade of former mesonychids now nests as giant tenrecs. This clade produced odontocete whales and transitional taxa. The latter group of true mesonychids gave rise to mysticete (baleen) whales and the following transitional taxa: hippos, anthrobunids and desmostylians.

Figure 1. Harpagolestes macrocephalus compared to sisters Sinonyx and Andrewsarchus to scale.

Figure 1. Harpagolestes macrocephalus compared to sisters Sinonyx and Andrewsarchus to scale.

Today the addition of Harpagolestes macrocephalus
(Fig. 1) to the LRT nests it not congenerically with Harpagolestes uintensis (Fig. 2), but between Andrewsarchus and Sinonyx. So the two are not congeneric.

Figure 1. Andrewsarchus, Sinonyx, Mesonyx and Harpagolestes to scale for direct comparison of these two tenrecs with these two mesonychids.

Figure 1. Andrewsarchus, Sinonyx, Mesonyx and Harpagolestes to scale for direct comparison of these two tenrecs with these two mesonychids.

We’ve seen convergence many times
in the LRT. This is just one more example of convergence that has been traditionally overlooked.

Deleting nine tenrecs
on either side of Sinonyx + Andrewsarchus + H. macrocephalus changes nothing in the LRT. The above taxa still nest with odontocetes far from mesonychids through mysticetes, though some loss of resolution occurs in the mammal subset of the LRT.

Deleting hippos and anthracobunids
from the mesonychid clade changes nothing.

References
O’Leary MA and Rose KD 1995. Postcranial skeleton of the early Eocene mesonychid Pachyaena (Mammalia: Mesonychia). Journal of Vertebrate Paleontology 15(2):401-430.

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