Foth Christian, Rauhut Oliver W M
Department of Geosciences, Université de Fribourg, Chemin du Musée 6, 1700, Fribourg, Switzerland.
Current address: Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1, 70191, Stuttgart, Germany.
BMC Evol Biol. 2017 Dec 2;17(1):236. doi: 10.1186/s12862-017-1076-y.
Archaeopteryx is an iconic fossil that has long been pivotal for our understanding of the origin of birds. Remains of this important taxon have only been found in the Late Jurassic lithographic limestones of Bavaria, Germany. Twelve skeletal specimens are reported so far. Archaeopteryx was long the only pre-Cretaceous paravian theropod known, but recent discoveries from the Tiaojishan Formation, China, yielded a remarkable diversity of this clade, including the possibly oldest and most basal known clade of avialan, here named Anchiornithidae. However, Archaeopteryx remains the only Jurassic paravian theropod based on diagnostic material reported outside China.
Re-examination of the incomplete Haarlem Archaeopteryx specimen did not find any diagnostic features of this genus. In contrast, the specimen markedly differs in proportions from other Archaeopteryx specimens and shares two distinct characters with anchiornithids. Phylogenetic analysis confirms it as the first anchiornithid recorded outside the Tiaojushan Formation of China, for which the new generic name Ostromia is proposed here.
In combination with a biogeographic analysis of coelurosaurian theropods and palaeogeographic and stratigraphic data, our results indicate an explosive radiation of maniraptoran coelurosaurs probably in isolation in eastern Asia in the late Middle Jurassic and a rapid, at least Laurasian dispersal of the different subclades in the Late Jurassic. Small body size and, possibly, a multiple origin of flight capabilities enhanced dispersal capabilities of paravian theropods and might thus have been crucial for their evolutionary success.
始祖鸟是一种标志性化石，长期以来对于我们理解鸟类的起源至关重要。这一重要分类单元的化石仅在德国巴伐利亚州晚侏罗世的印板石灰岩中被发现。迄今为止已报道了12具骨骼标本。始祖鸟长期以来是已知的唯一一种白垩纪之前的近鸟类兽脚亚目恐龙，但中国髫髻山组的最新发现揭示了这一演化支的显著多样性，包括可能是已知最古老、最基干的鸟翼类演化支，在此命名为近鸟科。然而，始祖鸟仍然是中国以外地区基于诊断性材料报道的唯一侏罗纪近鸟类兽脚亚目恐龙。
对不完整的哈勒姆始祖鸟标本重新检查后，未发现该属的任何诊断特征。相反，该标本在比例上与其他始祖鸟标本明显不同，并且与近鸟科共有两个独特特征。系统发育分析证实它是中国髫髻山组以外地区记录的首个近鸟科物种，为此这里提出新属名奥氏鸟。
结合虚骨龙类兽脚亚目恐龙的生物地理学分析以及古地理和地层数据，我们的结果表明，手盗龙类虚骨龙可能在中侏罗世晚期于东亚孤立地经历了一次爆发性辐射，并在晚侏罗世迅速（至少在劳亚大陆范围内）扩散到不同的演化支。体型较小以及飞行能力可能的多次起源增强了近鸟类兽脚亚目恐龙的扩散能力，因此可能对它们的演化成功至关重要。
