Martin Jeremy E, Rabi Márton, Csiki Zoltán
Département de Géologie, Université de Corse, UMR SPE 6134, 20250, Corté, France.
Naturwissenschaften. 2010 Sep;97(9):845-54. doi: 10.1007/s00114-010-0702-y. Epub 2010 Aug 14.
Small terrestrial non-eusuchian mesoeucrocodylians are common components of Cretaceous assemblages of Gondwanan provinces with notosuchians and araripesuchids as flagship taxa in South America, Africa and Madagascar, well into the Late Cretaceous. On the other hand, these are exceedingly rare in Laurasian landmasses during the Late Cretaceous. Small terrestrial mesoeucrocodylians from Europe were often referred to the genus Theriosuchus, a taxon with stratigraphic range extending from the Late Jurassic to the late Early Cretaceous. Theriosuchus is abundantly reported from various European localities, although Asiatic and possibly North American members are also known. It has often been closely associated with the first modern crocodilians, members of the Eusuchia, because of the presence of procoelous vertebrae, a widespread key character diagnosing the Eusuchia. Nevertheless, the relationships of Theriosuchus have not been explored in detail although one species, Theriosuchus pusillus, has been extensively described and referred in numerous works. Here, we describe a new basal mesoeucrocodylian, Theriosuchus sympiestodon sp. nov. from the Maastrichtian of the Haţeg Basin, Romania, suggesting a large temporal gap (about 58 myr) in the fossil record of the genus. Inclusion of the new taxon, along with Theriosuchus guimarotae, in a phylogenetic analysis confirms its referral to the genus Theriosuchus, within a monophyletic atoposaurid clade. Although phylogenetic resolution within this clade is still poor, the new taxon appears, on morphological grounds, to be most closely related to T. pusillus. The relationships of Atoposauridae within Mesoeucrocodylia and especially to Neosuchia are discussed in light of the results of the present contribution as well as from recent work. Our results raise the possibility that Atoposauridae might not be regarded as a derived neosuchian clade anymore, although further investigation of the neosuchian interrelationships is needed. Reports of isolated teeth referable to a closely related taxon from the Upper Cretaceous of Romania and France, together with the presence of Doratodon and Ischyrochampsa, indicate a previously unsuspected diverse assemblage of non-eusuchian mesoeucrocodylians in the Late Cretaceous European archipelago.
小型陆栖非真鳄类中真鳄类是冈瓦纳大陆白垩纪组合的常见组成部分，在南美洲、非洲和马达加斯加，诺托鳄类和阿拉里皮鳄类是旗舰类群，一直延续到晚白垩世。另一方面，在晚白垩世的劳亚大陆上，这些却极为罕见。欧洲的小型陆栖中真鳄类常被归入坚蜥鳄属，该类群的地层范围从晚侏罗世延伸至早白垩世晚期。坚蜥鳄在欧洲各地有大量报道，尽管亚洲及可能还有北美洲的成员也为人所知。由于存在前凹型椎体，这一广泛存在的关键特征可用于诊断真鳄类，它常与最早的现代鳄类——真鳄类成员密切相关。然而，尽管坚蜥鳄的一个物种——细小坚蜥鳄已在众多著作中被广泛描述和提及，但坚蜥鳄的系统发育关系尚未得到详细探究。在此，我们描述了一种新的基干中真鳄类——共生坚蜥鳄，它来自罗马尼亚哈采格盆地的马斯特里赫特阶，这表明该属的化石记录存在一个较大的时间间隔（约5800万年）。将这个新分类单元与吉马罗塔坚蜥鳄一起纳入系统发育分析，证实了它被归入坚蜥鳄属，位于一个单系的阿托波龙科分支内。尽管该分支内的系统发育分辨率仍然很低，但从形态学角度来看，这个新分类单元似乎与细小坚蜥鳄关系最为密切。根据本研究以及近期工作的结果，讨论了阿托波龙科在中真鳄类中的关系，尤其是与新鳄类的关系。我们的结果提出了一种可能性，即阿托波龙科可能不再被视为一个衍生的新鳄类分支，尽管还需要对新鳄类的相互关系进行进一步研究。来自罗马尼亚和法国上白垩统的与一个近缘分类单元相关的孤立牙齿报告，以及多拉图鳄和伊斯奇罗鳄的存在，表明在晚白垩世欧洲群岛存在一个此前未被怀疑的多样化的非真鳄类中真鳄类组合。
