Asia

An extraordinary wealth of fossil vertebrates has been collected from the Lufeng Basin, Yunnan Province, southern China (figure 2.4). The systematics, assemblages, and stratigraphic and geologic occurrences of the small tetrapods have recently been reviewed by Luo and Wu (1994). The most productive localities are northeast of Lufeng, in the Dachong-Dawa area, in the lower Lufeng Formation, which is about 400 m thick in this region. The lower Lufeng Formation is divided into two distinct litho-logic bodies, each characterized by a distinct fauna (Sun et al., 1985). The Dull Purplish Beds, below, contain mostly saurischian dinosaurs and the therapsid Bienotherium. The overlying Dark Red Beds are of greater interest in the current context: they have yielded a fauna comprised mainly of ornithischians, a diversified assemblage of ther-apsids (but not Bienotherium), and early mammals (table 2.2). The vertebrate fauna, most importantly some of the mammals and tritylodontid therapsids, is similar to those of the Welsh fissure fills and the Kayenta Formation, United States, indicating an Early Jurassic age (Luo and Wu, 1994; see also Sigogneau-Russell and Sun, 1981; Sun et al., 1985), with biochronologic constraints suggesting that the mammals are no older than Sinemurian and possibly extend into the Pliensbachian (Luo and Wu, 1995). The Dark Red Beds include mainly fluvial and overbank deposits made up of mudstones and siltstones; most of the small vertebrate fossils, including the mammals, are found in calcareous nodules that probably represent paleosols. The fossils are well preserved, usually consisting of partial or complete skulls, sometimes with associated skeletal material. Major localities in the Dark Red Beds of the Lufeng Basin are Dahuangtian, Dadi, Dawa, Heiguopeng, and Zhangjiawa (figure 2.4).

The first mammal to be described from the lower Lufeng Formation is Sinoconodon rigneyi (see Patterson and Olson, 1961). Sinoconodon is similar to Morganu-codon in many ways, but differs from the latter and other ta b l e 2.2. Early Jurassic Mammals of the Lower Lufeng Formation, Yunnan, China (see figure 2.4)

Mammalia incertae sedis Hadrocodium wui Kunminia minima Sinoconodontidae Sinoconodon rigneyi Morganucodonta Morganucodontidae Morganucodon oehleri Morganucodon heikuopengensis figure 2.4. Jurassic (China) and Cretaceous (Japan) mammal localities. Asterisks, Early (black; localities 1-5), Middle-Late (gray; localities 6-9), and Late (white; locality 10) Jurassic; diamonds, Early (black; locality 11) and Late (gray; locality 12) Cretaceous. Localities or local faunas: 1, Dahuangtian; 2, Dawa; 3, Heiguopeng; 4, Zhangjiawa; 5, Dadi (Dark Red Beds, lower Lufeng Formation; Early Jurassic, Yunnan Province); 6, Luchang (lower Yimen Formation; Early Jurassic, Sichuan Province); 7, Fangshen (Haifanggou Formation; ?Middle or Late Jurassic, Liaoning Province); 8, Zha-zy-ao Mine (Wa-fang-dian Formation; ?Middle Jurassic-Early Cretaceous, Liaoning Province); 9, Shilongzhai (Shaximiao Formation; ?Middle-Late Jurassic, Sichuan Province); 10, Jianshan Wash (Shishuguo Formation; Late Jurassic, Xinjiang Province); 11, Kaseki-kabe (Kuwajima Formation; late Hauterivian, Ishikawa Prefecture, Japan); 12, Amagimi Dam ("Upper Formation" of the Miiune Group; late Cenomanian-early Turonian, Kumamoto Prefecture, Japan).

figure 2.4. Jurassic (China) and Cretaceous (Japan) mammal localities. Asterisks, Early (black; localities 1-5), Middle-Late (gray; localities 6-9), and Late (white; locality 10) Jurassic; diamonds, Early (black; locality 11) and Late (gray; locality 12) Cretaceous. Localities or local faunas: 1, Dahuangtian; 2, Dawa; 3, Heiguopeng; 4, Zhangjiawa; 5, Dadi (Dark Red Beds, lower Lufeng Formation; Early Jurassic, Yunnan Province); 6, Luchang (lower Yimen Formation; Early Jurassic, Sichuan Province); 7, Fangshen (Haifanggou Formation; ?Middle or Late Jurassic, Liaoning Province); 8, Zha-zy-ao Mine (Wa-fang-dian Formation; ?Middle Jurassic-Early Cretaceous, Liaoning Province); 9, Shilongzhai (Shaximiao Formation; ?Middle-Late Jurassic, Sichuan Province); 10, Jianshan Wash (Shishuguo Formation; Late Jurassic, Xinjiang Province); 11, Kaseki-kabe (Kuwajima Formation; late Hauterivian, Ishikawa Prefecture, Japan); 12, Amagimi Dam ("Upper Formation" of the Miiune Group; late Cenomanian-early Turonian, Kumamoto Prefecture, Japan).

Late Triassic-Early Jurassic mammals in its dentition: upper and lower molars do not have a one-to-one correspondence, the postcanines do not develop occlusal wear facets, and some of the teeth, at least, were replaced continuously (Crompton and Luo, 1993, see chapter 4). Sinoconodon is now known by a number of skulls. Several other taxa subsequently described from the lower Lufeng Formation, "S. parringtoni," "S. yangi," and "Lufengocon-odon changchiawaensis" (see Young, 1982a; Zhang and Cui, 1983), are thought to be synonyms of Sinoconodon rigneyi, which evidently has a broad range of ontogenetic variation (Crompton and Luo, 1993; Luo and Wu, 1994). The lower Lufeng Formation has also yielded several skulls of Morganucodon, with two species, M. ohleri and M. heikuo-pengensis, currently recognized (see Rigney, 1963; Young, 1978). These fine specimens have provided the basis for a detailed understanding of the cranial anatomy of this im portant early mammal (Kermack et al., 1981; Crompton and Luo, 1993). Kunminia minima, earlier thought to be a therapsid (Young, 1947), is probably a mammal, though its affinities are uncertain. Hadrocodium wui is the most recently described mammal from the lower Lufeng Formation (Luo, Crompton, and Sun, 2001). Hadrocodium is known by a nearly complete skull and articulated mandible, and appears to be structurally intermediate between stem mammals (e.g., morganucodontids, docodon-tans) and monotremes (see chapter 4).

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