Abstract
The middle Eocene in Nei Mongol (China) was an interval of profound faunal changes as regards the basal Glires and gliriform mammals in general. A major diversification of rodent lineages (ctenodactyloids) and more modern small-sized lagomorphs was accompanied by a decline of mimotonids (Gomphos and Mimolagus) and anagalids. The latter was an enigmatic group of basal Euarchontoglires endemic to China and Mongolia. Here, we describe the first anagalid tooth (a P4) from the Huheboerhe classic site in the Erlian Basin. The tooth, characterized by its unique morphology intermediate between mimotonids and anagalids is semihypsodont, has a single buccal root typical of mimotonids, a large paracone located anteriorly, and a nascent hypocone, characteristic of advanced anagalids. The new finding of neither an abundant nor speciose group suggests a greater diversity of anagalids in the Eocene of China. This discovery is important because it demonstrates the convergent adaptations in anagalids, possibly of ecological significance.
Highlights
Glires is the most numerous clade of Euarchontoglires which, in turn, is one of the four main clades of placental mammals, recognized on the basis of molecular and morphological data—e.g., [1,2,3]
Since the middle Eocene onward, mammalian faunas in central Asia experienced major faunal turnovers coupled with climate cooling and aridification [31,32,33,34]
After the middle Eocene the number of known anagalids dropped to three monotypic genera
Summary
Glires (rodents and lagomorphs) is the most numerous clade of Euarchontoglires which, in turn, is one of the four main clades of placental mammals, recognized on the basis of molecular and morphological data—e.g., [1,2,3]. The “basal Glires” is an operational term for a paraphyletic group of primitive members of the clade, which do not display clear rodent or lagomorph synapomorphies. This group can be partitioned into simplicidentates (Eurymylidae) and duplicidentates (Mimotonidae), based on the number of incisors [4,5,6].
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