Key Laboratory of Evolutionary Systematics of Vertebrates, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, Beijing 100044, People's Republic of China.
Proc Biol Sci. 2010 Jan 22;277(1679):285-92. doi: 10.1098/rspb.2009.0883. Epub 2009 Jul 29.
A new well-preserved basal therapsid skull from the Xidagou Formation, Middle Permian of China, is identified as Biseridens qilianicus. The following synapomorphies distinguish Biseridens as an anomodont and not an eotitanosuchian as previously described: short snout; dorsally elevated zygomatic arch and septomaxilla lacking elongated posterodorsal process between nasal and maxilla. The presence of a differentiated tooth row; denticles on vomer, palatine and pterygoid; contact between tabular and opisthotic; lateral process of transverse flange of pterygoid free of posterior ramus and absence of mandibular foramen exclude it from other anomodonts. Our cladistic analysis indicates Biseridens to be the most basal anomodont, highlights separate Laurasian and Gondwanan basal anomodont clades and suggests that dicynodonts had their origins in the Gondwanan clade. The co-occurrence of the most basal anomodont (Biseridens) together with the most basal therapsid (Raranimus), basal anteosaurid dinocephalians, bolosaurids and dissorophids suggests that the earliest therapsid faunas are from China.
一个新的保存完好的基干兽孔目头骨来自中国中二叠统的西格道组，被鉴定为奇异栉龙。以下的共有衍征将奇异栉龙归类为似哺乳爬行动物而非以前描述的原鳄类：短吻；颧骨和上颌骨在背侧升高，在鼻骨和上颌骨之间没有长的背侧后突。存在分化的齿列；犁骨、腭骨和翼骨上有齿质小尖；方骨和后耳骨接触；翼骨横突的外侧突游离于后支且没有下颌孔，将其排除在其他似哺乳爬行动物之外。我们的分支分析表明奇异栉龙是最基干的似哺乳爬行动物，突出了分开的劳亚古陆和冈瓦纳古陆基干似哺乳爬行动物的分支，并表明二齿兽类起源于冈瓦纳古陆分支。最基干的似哺乳爬行动物（奇异栉龙）与最基干的兽孔目（瑞钦龙）、基干兽头亚目恐龙、Bolosauridae 和盘舌蟾目一起出现，表明最早的兽孔目动物群来自中国。
