The Mesozoic and Cenozoic track record of large birds (avian theropods) with footprint lengths (FL) > 10.0 cm is quite limited, whereas small tracks (FL < 10.0 cm) are abundant from the Early Cretaceous onwards. This large versus small threshold value is consistent with the track record of extant birds among which only ˜10% are large, and so is scaled appropriately to Class Aves. The proportion of large pachydactylous (thick-toed) or robust non-avian theropod ichnotaxa reported from the Mesozoic considerably exceeds the few large leptodactylous (thin-toed) or gracile forms such as Archaeornithipus and Magnoavipes, named, albeit controversially, to suggest avian affinity. The Cenozoic record of large avian tracks is quite different, with large pachydactylous tracks limited to a few Eocene-Oligocene (Palaeogene) ichnogenera (Ornithoformipes and Rivavipes), and rare unnamed Neogene and Holocene dinornithiform tracks. Thus, large flightless species are less well represented by tracks than body fossils. This suggests probable preservational bias in favour of waterbird or shorebird-like tracks in shoreline facies. However, the Cenozoic record of large leptodactylous tracks attributable to cranes, herons and related trackmakers is quite extensive, mostly confined to the Neogene and formally named to suggest representatives of extant avian clades capable of flight. These distribution patterns apparently reflect the dominance of large pachydactylous non-avian and avian theropods in the Mesozoic and early Palaeogene, and contrast with the rise of large, as well ongoing diversification of smaller leptodactylous Aequornithes in the Neogene. These distribution patterns in space and time likely reflect changing selection pressures as today's modern avifauna evolved.

中文翻译：

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中生代和新生代的大型无网鸟类和类鸟足迹：鱼类分类学和追踪者亲和力的回顾

足印长度 (FL) > 10.0 cm 的大型鸟类（禽兽脚亚目）的中生代和新生代足迹记录非常有限，而从白垩纪早期开始，小型足迹（FL < 10.0 cm）就很丰富。这个大小阈值与现存鸟类的记录一致，其中只有约 10% 是大的，因此被适当地缩放到 Aves 类。中生代报告的大型厚趾（厚趾）或健壮的非鸟类兽脚亚目 ichnotaxa 的比例大大超过了少数大型的细趾（细趾）或纤细的形式，如古鸟嘴龙和Magnoavipes，命名，尽管有争议，以暗示鸟类的亲和力。新生代大型鸟类足迹的记录则截然不同，大型厚趾足迹仅限于少数始新世-渐新世（Palaeogene） ichnogenera（Ornithoformipes和Rivavipes ）)，以及罕见的未命名的新近纪和全新世二鸟形轨道。因此，大型不会飞的物种的足迹不如身体化石那么好。这表明在海岸线相中可能存在有利于水鸟或类似鸻鹬踪迹的保护偏见。然而，可归因于鹤、苍鹭和相关追踪者的大型细爪足迹的新生代记录相当广泛，主要局限于新近纪，并正式命名以暗示现存的能够飞行的鸟类进化枝的代表。这些分布模式显然反映了中生代和古近纪早期大型厚趾非鸟类和鸟类兽脚类动物的优势，并与新近纪中大型和持续多样化的小型细趾水母的崛起形成鲜明对比。