Jeholornis compared to Archaeopteryx, with a new understanding of the earliest avian evolution

Zhou, Zhonghe; Zhang, Fucheng

doi:10.1007/s00114-003-0416-5

Cited by 110 publications

(99 citation statements)

References 16 publications

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“…These differences in morphology as well as ossification suggest the observed similarities represent parallelisms within the ornithothoracines. This is also documented in another basal clade of birds, the Jeholornithiformes 24,25 , and at least one dromaeosaurid also preserves an elongate pair of 'caudal trabeculae' (Linheraptor- Fig. 4a).…”

Section: Discussionmentioning

confidence: 59%

Insight into the early evolution of the avian sternum from juvenile enantiornithines

et al. 2012

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The sternum is one of the most important and characteristic skeletal elements in living birds, highly adapted for flight and showing a diverse range of morphologies. new exceptional material of young juvenile specimens from the Early Cretaceous Jehol Group in northeastern China reveals the unique sequence of development in the sternum of Enantiornithes, the dominant clade of Cretaceous birds. We recognize six ossifications that together form the sternum, three of which were previously unknown. Here we show that although basal living birds apparently have retained the dinosaurian condition in which the sternum develops from a bilateral pair of ossifications (present in paravian dinosaurs and basal birds), the enantiornithine sternal body primarily develops from two unilateral proximo-distally arranged ossifications. This indicates that although superficially similar, the sternum formed very differently in enantiornithines and ornithuromorphs, suggesting that several ornithothoracine sternal features may represent parallelism. This highlights the importance of ontogenetic studies for understanding homology and the evolution of skeletal features in palaeontology.

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Section: Discussionmentioning

confidence: 59%

Insight into the early evolution of the avian sternum from juvenile enantiornithines

et al. 2012

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“…S3A) and is inferred to have articulated on the lateral surface, functioning as lateral trabeculae although in no specimen are the "lateral trabeculae" fused to the sternum (20), and their in vivo articulation with the sternal body is unknown (20,21). Four to five pairs of sternal ribs articulated with the sternum; costal facets appear not to be developed (present in some nonavian theropods, the basal bird Confuciusornis, and ornithuromorphs) (22)(23)(24).…”

Section: Resultsmentioning

confidence: 99%

On the absence of sternal elements inAnchiornis(Paraves) andSapeornis(Aves) and the complex early evolution of the avian sternum

Zheng

O’Connor

Wang

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Anchiornis (Deinonychosauria: Troodontidae), the earliest known feathered dinosaur, and Sapeornis (Aves: Pygostylia), one of the basalmost Cretaceous birds, are both known from hundreds of specimens, although remarkably not one specimen preserves any sternal ossifications. We use histological analysis to confirm the absence of this element in adult specimens. Furthermore, the excellent preservation of soft-tissue structures in some specimens suggests that no chondrified sternum was present. Archaeopteryx, the oldest and most basal known bird, is known from only 10 specimens and the presence of a sternum is controversial; a chondrified sternum is widely considered to have been present. However, data from Anchiornis and Sapeornis suggest that a sternum may also have been completely absent in this important taxon, suggesting that the absence of a sternum could represent the plesiomorphic avian condition. Our discovery reveals an unexpected level of complexity in the early evolution of the avian sternum; the large amount of observable homoplasy is probably a direct result of the high degree of inherent developmental plasticity of the sternum compared with observations in other skeletal elements.Maniraptora | Mesozoic | Jehol | flight | histology

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“…Furthermore, radiographs of at least one specimen show that the vertebrae are dense and solidly constructed, which is more consistent with apneumatic bone than with pneumaticity (Mayr et al, 2007). However, PSP was present in other basal birds (e.g., Ichthyornis, Jeholornis; Marsh, 1880;Zhou and Zhang, 2003), and many other basal birds have humeral and vertebral fossae that may have been pneumatic (Sanz et al,'95). Therefore, it is not clear if PSP in nonavian theropods is taxically homologous (sensu Patterson, '82) with that of birds.…”

Section: Shared Developmental Pathways and The Origin(s) Of Air Sacs mentioning

confidence: 94%

Evidence for bird‐like air sacs in saurischian dinosaurs

2009

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Among extant tetrapods, pneumatic postcranial bones are only present in birds, and they are osteological correlates of the diverticular lungs and pulmonary air sacs. The presence of postcranial pneumaticity in sauropod and theropod dinosaurs suggests that some form of air sac system was also present in the dinosaurian ancestors of birds. In particular, anatomical and evolutionary patterns of pneumatization in nonavian saurischian dinosaurs are diagnostic for specific air sacs, including the cervical, clavicular, and abdominal air sacs. Pneumatic hiatuses are gaps in the pneumatization of the vertebral column and indicate pneumatization from multiple sources. A pneumatic hiatus in Haplocanthosaurus provides additional support for the presence of abdominal air sacs in sauropods. The origins of postcranial pneumaticity in archosaurs are enigmatic because the earliest putative traces of pneumaticity are difficult to distinguish from skeletal imprints of other soft tissues. Nevertheless, several lines of evidence suggest that air sac-driven lung ventilation was primitive for Saurischia.

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Jeholornis compared to Archaeopteryx, with a new understanding of the earliest avian evolution

Cited by 110 publications

References 16 publications

Insight into the early evolution of the avian sternum from juvenile enantiornithines

Insight into the early evolution of the avian sternum from juvenile enantiornithines

On the absence of sternal elements inAnchiornis(Paraves) andSapeornis(Aves) and the complex early evolution of the avian sternum

Evidence for bird‐like air sacs in saurischian dinosaurs

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