分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： A unique canal (calcaneal canal) running diagonally through the calcaneus was commonly considered as characteristic for lagomorphs, both extant and fossil, but absent in rodents and other pertinent lagomorph relatives. However, our investigation of a calcaneus from the Middle Paleocene of Qianshan, Anhui Province and specimens previously grouped in Mimotonidae also shows presence of canals on calcaneus bones. To further explore the unique character, we scanned calcanei of Ordolagus, Mimolagus, Gomphos, Rhombomylus, and Oryctolagus using micro CT and investigated the calcanei of some other related taxa under microscope. Three-dimensional reconstructions of the calcanei based on CT data of these taxa confirmed the presence of apertures traversing the large medullary cavity. The diagonally oriented calcaneal canal is present not only in lagomorphs, but also in non-lagomorph duplicidentates, such as Mimotona, Gomophos, and simplicidentates, such as Rhombomylus, though smaller in size. Hence, the presence of calcaneal canal may be one of the synapomophic characters for Glires, not only for the order Lagomorpha. The shared calcaneus character confirms the close relationship between Simplicidentata and Duplicidentata.
分类： 生物学 >> 动物学 提交时间： 2017-11-07 合作期刊: 《古脊椎动物学报》
摘要： The mammalian fossils (Mimolagus and Anagalopsis) from Shanmacheng in the Jiuxi Basin described by Bohlin in 1951 have long been enigmatic in systematics and controversial in the geological age. New survey in this area suggests the fossils were discovered from the Shanmacheng member of the Huoshaogou Formation. Comparisons of the Shanmacheng fossils with new specimens of Mimolagus from the Irdin Mahan Formation, and Anagale from the Late Eocene Ulan Gochu Formation, Nei Mongol, suggest an Eocene age for the Shanmacheng fossils. Reinterpretation of the fossil horizon and the paleomagnetic data of Dai et al. (2005) indicates the polarity zones from Huoshaogou section can be correlated to GPTS Chrons 13−18. Therefore, the Huoshaogou Formation may cover late Middle Eocene to Late Eocene and Bohlin’s fossil horizon can roughly be correlated to Chron18n (~39−40 Ma) of late Middle Eocene. The late Middle Eocene age of Mimolagus rodens narrows the time gap with its close relative Gomphos that have been recorded from Early to Middle Eocene. The archaic group Anagalidae may have become extinct before Oligocene.
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