Despite significant recent improvements to our understanding of the early evolution of the Order Proboscidea (elephants and
their extinct relatives), geographic sampling of the group’s Paleogene fossil record remains strongly biased, with the first
~30 million years of proboscidean evolution documented solely in near-coastal deposits of northern Africa. The considerable
morphological disparity that is observable among the late Eocene and early Oligocene proboscideans of northern Africa suggests
that other, as yet unsampled, parts of Afro-Arabia might have served as important centers for the early diversification of
major proboscidean clades. Here we describe the oldest taxonomically diagnostic remains of a fossil proboscidean from the
Arabian Peninsula, a partial mandible of
Omanitherium dhofarensis (new genus and species), from near the base of the early Oligocene Shizar Member of the Ashawq Formation, in the Dhofar Governorate
of the Sultanate of Oman. The molars and premolars of
Omanitherium are morphologically intermediate between those of
Arcanotherium and
Barytherium from northern Africa, but its specialized lower incisors are unlike those of other known Paleogene proboscideans in being
greatly enlarged, high-crowned, conical, and tusk-like.
Omanitherium is consistently placed close to late Eocene
Barytherium in our phylogenetic analyses, and we place the new genus in the Family Barytheriidae. Some features of
Omanitherium, such as tusk-like lower second incisors, the possible loss of the lower central incisors, an enlarged anterior mental foramen,
and inferred elongate mandibular symphysis and diminutive P
2, suggest a possible phylogenetic link with Deinotheriidae, an extinct family of proboscideans whose origins have long been
mysterious.
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