New materials of Exallerix pustulatus (Erinaceidae, Eulipotyphla) from Nei Mongol and other Brachyericinae of China

LI Lu, LI Qiang, WANG Xiao-Ming

Vertebrata Palasiatica 2025, 63 (4): 335-349. DOI: 10.19615/j.cnki.2096-9899.250910

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This article describes new fossil material of Exallerix pustulatus from the early Late Oligocene of Nei Mongol, China. The specimens supplement and clarify certain mandibular and lower dental morphological features of this species, allowing for further comparisons with other short-faced hedgehogs. Previously, E. pustulatus had only been recorded from the Hsanda Gol Formation at Taatsiin Gol, in the Valley of Lakes, Mongolia. This discovery of new material from Sonid Left Banner marks the first occurrence of the genus Exallerix in China. In addition, discussions of other short-faced hedgehog fossils from Chinese localities confirm the validity of Metexallerix gaolanshanensis, which lived during the late Late Oligocene, approximately 25 Ma. Furthermore, the short-faced hedgehog specimens from locality Damiao 16 in Nei Mongol are tentatively referred to Synexallerix junggarensis, rather than M. gaolanshanensis.

As noted by Lopatin and Zazhigin (2003), Asian short-faced hedgehogs, including Synexallerix, Posterallerix, and Exallerix, exhibit a more derived dental morphology, specifically: 1) a narrower and more elongated m1 trigonid (Fig. 4); 2) a relatively shorter talonid on the m1 (Fig. 5); and 3) a smaller ratio of m2 length to m1 length (Fig. 6). In contrast, the dental features of Exallerix pustulatus show closer resemblance to those of North American short-faced hedgehogs.

Furthermore, the evolutionary trends in m1 morphology differ significantly between Asian and North American short-faced hedgehogs. In the former group, the trigonid tends to become increasingly elongated anteroposteriorly over time, whereas in the latter, the opposite trend is observed (Figs. 4, 5). The m2 appears to be relatively stable in both lineages (Fig. 6). However, due to the limited sample size and scarcity of comparative data, further analysis is not feasible.