Zhangheotherium, Feredocodon, Anebodon, Maotherium and Origolestes

Zhangheotherium quinquecuspidens (Hu et al. 1997; Earliest Cretaceous, 145-125mya, dentary length 3cm; IVPP V7466) was originally described as a symmetrodont mammal. Hu et al. thought Zhangheotherium radiated before the divergence of living marsupials and placentals. In the large reptile tree Zhangheotherium nests with Maotherium.

The dentary condylar process curves dorsally and all post-dentary bones are middle ear bones. That dorsal curve removes most of the ability to resist jaw dislocation often caused by struggling large prey and or small pieces of even larger prey are working against large canines, which were also not present in Zhangheotherium. These traits point to a tiny prey diet, likely of insects, just like pangolins. A mobile clavicle–interclavicle allows a wide range of movement, as in bats.

Maotherium sinensis (Rougier et al., 2003; NGMC 97415; Early Cretaceous, 125 mya; is a symmetrodont cynodont pre-mammal. Another species M. asiaticus is shown below. Derived from a sister to Yanoconodon, tiny Maotherium has a short tail without chevrons. The ilium is long and at least four sacrals were present, indicating both a strong hind limb and a reinforced sacrum, both possible leaping structures. Both humeri are broken at mid shaft in the fossil. Like members of Glires, like Mus, the anterior teeth were procumbent and a diastema separted the canine from the premolars.

Anebodon luoi (Bi et al. 2016; STM 38-4; Early Cretaceous) is a zhangheotheriid symmetrodont pre-mammal. The canines were no larger than the other teeth. The molars were replaced. The nasals are parallel, not wider posteriorly.

Feredocodon chowi (Mao et al. 2024a; IMMNH-PV01035; Early Jurassic) is a tiny shuotheriid symmetrodont pre-mammal. The canines were no larger than the other teeth and multi-cusped. The molars were replaced. The nasals were wider posteriorly. Five molars and five premolars were present in adults.

Origolestes lii (Mao et al. 2019; Early Cretaceous, 120mya) nests with the coeval Maotherium. The skeleton is more complete and includes posterior ear/jaw bones.

Bi S-D, heng X-T, Meng J, Wang X-L, Robinson N and Davis B 2016. A new symmetrodont mammal (Trechnotheria: Zhangheotheriidae) from the Early Cretaceous of China and trechnotherian character evolution. Nature Scientific Reports 6:26668 DOI: 10.1038/srep26668

Hu Y-M, Wang YQ, Luo Z and Li CK 1997. A new symmetrodont mammal from China and its implications for mammalian evolution. Nature 390:137-142.

Ji Q, Luo Z-X, Zhang X-L, Yuan C-X and Xu L 2009. Evolutionary development of the middle ear in Mesozoic therian mammals. Science 326 (5950): 278–281. doi:10.1126/science.1178501. PMID 19815774.

Kielan-Jaworowska Z 2013. In pursuit of early mammals. Indiana University Press 272 pp.

Mao F, Hu Y-M, Li C-K, Wang YQ, Chase MH, Smith AK and Meng J 2019. Integrated hearing and chewing modules decoupled in a Cretaceous stem therian mammal. Science (2019). https://science.sciencemag.org/content/early/2019/12/04/science.aay9220

Mao F et al (6 co-authors) 2024a. Jurasssic shuotheriids show earliest dental diversification of mammaliaforms. Nature 782(260) online.

Rougier GW, Qiang J, Novacek MJ 2003. A New Symmetrodont Mammal with Fur Impressions from the Mesozoic of China. Acta Geologica Sinica 77 (1): 7–14. doi:10.1111/j.1755-6724.2003.tb00104.x.

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