2022年11月30日，英国剑桥大学Daniel J. Field等研究人员合作《自然》杂志发表论文。该研究发现，白垩纪鸟类支持一个新颌型冠鸟祖先。

研究人员报告了一个新的白垩纪晚期鸟类的分类群，其翼状肌与现存的今鸟类鸡雁小纲（水禽+陆禽）的非常相似。Janavis finalidens, gen. et sp. nov.，在整体形态上与著名的中生代鸟类Ichthyornis相似，但Janavis要大得多，并表现出相当程度的颅后气腔。研究人员发现Janavis是Ichthyornithes中除Ichthyornis之外的第一个有充分代表性的成员，清楚地证实了该支系在最新白垩纪的持续存在。Janavis证实了至少在一些中生代非冠鸟类中存在解剖学上的新腭，表明与现存的鸡雁小纲相似的翼状肌可能是冠鸟类的多形性。

这项研究结果加上最近关于ichthyornithine腭骨的证据，推翻了长期以来关于冠鸟祖先腭骨的假设，并应促使人们重新评价几个被认为是奇特的新生代早期鸡雁小纲群体，如“假齿鸟”（Pelagornithidae）。

据了解，骨腭诊断了现存鸟类的两个最深的支系：今颌总目和古颚总目。今颌类表现出未融合的腭骨和一般的运动型头骨，而古颚类拥有相对坚硬的头骨，而翼骨和腭骨融合成一个元素，这种情况长期以来被认为是冠鸟（今颌类）的祖先。然而，接近今颌类起源类群的腭部遗体化石证据很少，阻碍了对今颌类腭部祖先状况的有力推断。

附：英文原文

Title: Cretaceous ornithurine supports a neognathous crown bird ancestor

Author: Benito, Juan, Kuo, Pei-Chen, Widrig, Klara E., Jagt, John W. M., Field, Daniel J.

Issue&Volume: 2022-11-30

Abstract: The bony palate diagnoses the two deepest clades of extant birds: Neognathae and Palaeognathae1,2,3,4,5. Neognaths exhibit unfused palate bones and generally kinetic skulls, whereas palaeognaths possess comparatively rigid skulls with the pterygoid and palatine fused into a single element, a condition long considered ancestral for crown birds (Neornithes)3,5,6,7,8. However, fossil evidence of palatal remains from taxa close to the origin of Neornithes is scarce, hindering strong inferences regarding the ancestral condition of the neornithine palate. Here we report a new taxon of toothed Late Cretaceous ornithurine bearing a pterygoid that is remarkably similar to those of the extant neognath clade Galloanserae (waterfowl + landfowl). Janavis finalidens, gen. et sp. nov., is generally similar to the well-known Mesozoic ornithurine Ichthyornis in its overall morphology, although Janavis is much larger and exhibits a substantially greater degree of postcranial pneumaticity. We recovered Janavis as the first-known well-represented member of Ichthyornithes other than Ichthyornis, clearly substantiating the persistence of the clade into the latest Cretaceous9. Janavis confirms the presence of an anatomically neognathous palate in at least some Mesozoic non-crown ornithurines10,11,12, suggesting that pterygoids similar to those of extant Galloanserae may be plesiomorphic for crown birds. Our results, combined with recent evidence on the ichthyornithine palatine12, overturn longstanding assumptions about the ancestral crown bird palate, and should prompt reevaluation of the purported galloanseran affinities of several bizarre early Cenozoic groups such as the ‘pseudotoothed birds’ (Pelagornithidae)13,14,15.

DOI: 10.1038/s41586-022-05445-y

Source: https://www.nature.com/articles/s41586-022-05445-y