Distributed under Creative Commons Cc-by 4.0 the Phylogenetic Affinities of the Bizarre Late Cretaceous Romanian Theropod Balaur Bondoc (dinosauria, Maniraptora): Dromaeosaurid or Flightless Bird?
Distributed under Creative Commons Cc-by 4.0 the Phylogenetic Affinities of the Bizarre Late Cretaceous Romanian Theropod Balaur Bondoc (dinosauria, Maniraptora): Dromaeosaurid or Flightless Bird?
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通讯作者：
A. Cau;Tom Brougham;D. Naish
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作者：
A. Cau;Tom Brougham;D. Naish
保存异常完好的罗马尼亚恐龙巴劳尔邦多克（Balaur bondoc）是迄今为止欧洲上白垩纪已知最完整的兽脚亚目恐龙。先前对这一非凡分类群的研究包括将其系统发育解释为具有迅猛龙亲和力的异常驰龙科。然而，巴劳尔表现出明显的类形和衍生的鸟类特征的结合。在这里，我们在系统发育修订中分析了这些特征，并展示了它们如何挑战其归属驰龙科的地位。我们对两个不同的系统发育数据集的重新分析，重点是基础近鸟类类群，支持将巴拉尔重新解释为比始祖鸟更冠冕但位于尾柱纲之外的鸟类，并且是长尾鸟类并系群内的不会飞的分类群。我们将 Balaur 在 Avialae 中的位置并没有因角色权重而产生偏差。驰龙科的放置导致了一个次优的替代方案，根据现有的数据不能拒绝该替代方案。巴拉乌尔被解释为驰龙科动物，被认为是超级肉食性和掠食性的，表现出受岛屿特有现象影响的特殊形态。然而，类似驰龙科的生态学与巴拉尔形态的几个细节相矛盾，包括失去第三个功能性手指、第二跖骨的非牙龈状远端，以及第二足趾上的非镰状爪，缺乏突出的屈肌结节。相反，杂食性生态学更能得到 Balaur 形态的支持，并且与其在 Avialae 中的系统发育位置一致。我们对巴拉尔的重新解释表明，表面上类似驰龙科的分类群代表了体型较小、可能会飞翔的祖先的放大的、陆地化的后代。
The exceptionally well-preserved Romanian dinosaur Balaur bondoc is the most complete theropod known to date from the Upper Cretaceous of Europe. Previous studies of this remarkable taxon have included its phylogenetic interpretation as an aberrant dromaeosaurid with velociraptorine affinities. However, Balaur displays a combination of both apparently plesiomorphic and derived bird-like characters. Here, we analyse those features in a phylogenetic revision and show how they challenge its referral to Dromaeosauridae. Our reanalysis of two distinct phylogenetic datasets focusing on basal paravian taxa supports the reinterpretation of Balaur as an avialan more crownward than Archaeopteryx but outside of Pygostylia, and as a flightless taxon within a paraphyletic assemblage of long-tailed birds. Our placement of Balaur within Avialae is not biased by character weighting. The placement among dromaeosaurids resulted in a suboptimal alternative that cannot be rejected based on the data to hand. Interpreted as a dromaeosaurid, Balaur has been assumed to be hypercarnivorous and predatory, exhibiting a peculiar morphology influenced by island endemism. However, a dromaeosaurid-like ecology is contradicted by several details of Balaur's morphology, including the loss of a third functional manual digit, the non-ginglymoid distal end of metatarsal II, and a non-falciform ungual on the second pedal digit that lacks a prominent flexor tubercle. Conversely, an omnivorous ecology is better supported by Balaur's morphology and is consistent with its phylogenetic placement within Avialae. Our reinterpretation of Balaur implies that a superficially dromaeosaurid-like taxon represents the enlarged, terrestrialised descendant of smaller and probably volant ancestors.