Theropod dinosaurs were relatively scarce in the Late Cretaceous ecosystems of southeast Brazil. Instead, hypercarnivorous crocodyliforms known as baurusuchids were abundant and probably occupied the ecological role of apex predators. Baurusuchids exhibited a series of morphological adaptations hypothesised to be associated with this ecological role, but quantitative biomechanical analyses of their morphology have so far been lacking. Here, we employ a biomechanical modelling approach, applying finite element analysis (FEA) to models of the skull and mandibles of a baurusuchid specimen. This allowed us to characterise the craniomandibular apparatus of baurusuchids, as well as to compare the functional morphology of the group to that of other archosaurian carnivores, such as theropods and crocodylians. Our results support the ecological role of baurusuchids as specialised apex predators in the continental Late Cretaceous ecosystems of South America. With a relatively weak bite force (∼600 N), baurusuchids’ predation strategies likely relied on other morphological specializations, such as ziphodont dentition and strong cervical musculature. Comparative assessments of the stress distribution and magnitude of scaled models of other predators (the theropod Allosaurus fragilis and the living crocodylian Alligator mississippiensis) consistently show different responses to loadings under the same functional scenarios, suggesting distinct predatory behaviours for these animals. The unique selective pressures in the arid to semi-arid Late Cretaceous ecosystems of southeast Brazil, which were dominated by crocodyliforms, possibly drove the emergence and evolution of the biomechanical features seen in baurusuchids, which are distinct from those previously reported for other predatory taxa.

中文翻译：

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独特生态系统中的独特捕食者：根据巴西晚白垩世鳄类动物为主的动物对先端捕食者进行建模

在巴西东南部的晚白垩世生态系统中，兽脚亚目恐龙相对稀少。取而代之的是，被称为baurusuchids的肉食性鳄形鳄很丰富，并可能占据了先端捕食者的生态角色。据推测，鲍鲁氏类动物表现出一系列形态学适应性，推测与这种生态作用有关，但是迄今为止，还缺乏对其形态学的定量生物力学分析。在这里，我们采用生物力学建模方法，将有限元分析（FEA）应用于鲍鲁氏类动物标本的头骨和下颌骨模型。这使我们能够表征鲍氏鳄类的颅下颌装置，并将该组的功能形态与其他食肉动物和鳄类食肉动物相比较。我们的研究结果支持了南美白垩纪大陆生态系统中作为特殊先天掠食者的baurusuchids的生态作用。由于咬合力相对较弱（〜600 N），鲍鲁氏类动物的捕食策略可能依赖于其他形态学特征，例如齿牙列和强壮的宫颈肌肉组织。对其他食肉动物（兽脚类动物）的应力分布和比例模型的大小的比较评估脆弱的异特龙和活的鳄鳄密西西比州）在相同的功能情况下始终显示出对负荷的不同反应，表明这些动物的捕食行为不同。在巴西东南部干旱至半干旱的晚白垩纪生态系统中，独特的选择压力主要由鳄形动物主导，可能推动了鲍鲁氏类动物中生物力学特征的出现和演变，这与先前报道的其他掠夺性分类群不同。