A TRITYLODONTID SYNAPSID FROM THE MIDDLE JURASSIC OF SIBERIA AND THE TAXONOMY OF DERIVED TRITYLODONTIDS
A TRITYLODONTID SYNAPSID FROM THE MIDDLE JURASSIC OF SIBERIA AND THE TAXONOMY OF DERIVED TRITYLODONTIDS
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DOI：
10.1080/02724634.2017.1363767
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发表时间：
2017-01-01
影响因子：
1.4
通讯作者：
Krasnolutskii, Sergei A.
中科院分区：
文献类型：
--
作者：
Averianov, Alexander O.;Martin, Thomas;Krasnolutskii, Sergei A.
俄罗斯克拉斯诺亚尔斯克地区别列佐夫斯克煤矿中侏罗世(巴吞纪)地层中的上、下三齿后犬齿被称为Stereogna sp.。Stereognaus Charlesworth，1855(Polistodon He and Cai，1984，Xenocretosuchus Tatarinov and Mashenko，1999，和Montirictus Matsuoka et al.，2016为新异名)，与Bocatherium相似，但不同于所有其他三齿类，其上后尖公式为2：2：2，不同于Bocatherium的上后尖齿的四边形形状。立体齿龙与所有其他三齿龙的不同之处还在于，在上后犬齿中有一个更精细的联锁系统，每个齿上都有一个近中扣带连接杯B0、M0和L0。Stereogna与Bientheroids共享单根下部犬齿，这两个属关系密切。在ITAT组中发现的Stereogna表明，该地层单位的脊椎动物组合与西伯利亚Ilek组的英国巴索尼亚脊椎动物组合和早白垩世脊椎动物群相似。在西伯利亚，在大约40 Ma的时间间隔内，Stereogna的存在表明该地区脊椎动物群的演化处于长期停滞状态。
Upper and lower tritylodontid postcanine teeth from the Middle Jurassic (Bathonian) Itat Formation of the Berezovsk coal mine, Krasnoyarsk Territory, Russia, are referred to Stereognathus sp. The genus Stereognathus Charlesworth, 1855 (Polistodon He and Cai, 1984, Xenocretosuchus Tatarinov and Mashenko, 1999, and Montirictus Matsuoka et al., 2016, are new synonyms), is similar to Bocatherium and differs from all other tritylodontids in having an upper postcanine cusp formula of 2:2:2. It differs from Bocatherium in the quadrangular shape of the upper postcanine teeth. Stereognathus also differs from all other tritylodontids in having a more elaborate interlocking system in the upper postcanine teeth, each of which bears a mesial cingulum connecting cups B0, M0, and L0. Stereognathus shares with Bienotheroides single-rooted lower postcanine teeth, and these two genera are closely related. Discovery of Stereognathus in the Itat Formation underlines the similarity of the vertebrate assemblage from this stratigraphic unit to the British Bathonian vertebrate assemblages and the Early Cretaceous vertebrate fauna from the Ilek Formation in Siberia. The presence of Stereognathus during an similar to 40 Ma time interval in Siberia suggests a long stasis in the evolution of the vertebrate faunas of this region.