Cranial osteology and palaeobiology of Jeholornis prima (1 Viewer)

[Fred Ruhe]

Han Hu, Yan Wang, Matteo Fabbri, Jingmai K O’Connor, Paul G Mcdonald, Stephen Wroe, Xuwei Yin, Xiaoting Zheng, Zhonghe Zhou & Roger B J Benson 2022,

Cranial osteology and palaeobiology of the Early Cretaceous bird Jeholornis prima (Aves: Jeholornithiformes)

Zoological Journal of the Linnean Society, zlac089

doi: https://doi.org/10.1093/zoolinnean/zlac089

https://academic.oup.com/zoolinnean/advance-article/doi/10.1093/zoolinnean/zlac089/6768673

Abstract

Jeholornis is a representative of the earliest-diverging bird lineages, providing important evidence of anatomical transitions involved in bird origins. Although ~100 specimens have been reported, its cranial morphology remains poorly documented owing to poor two-dimensional preservation, limiting our understanding of the morphology and ecology of the key avian lineage Jeholornithiformes, in addition to cranial evolution during the origin and early evolution of birds. Here, we provide a detailed description of the cranial osteology of Jeholornis prima, based primarily on high-quality, three-dimensional data of a recently reported specimen. New anatomical information confirms the overall plesiomorphic morphology of the skull, with the exception of the more specialized rostrum. Data from a large sample size of specimens reveal the dental formula of J. prima to be 0–2–3 (premaxillary–maxillary–dentary tooth counts), contrary to previous suggestions that the presence of maxillary teeth is diagnostic of a separate species, Jeholornis palmapenis. We also present evidence of sensory adaptation, including relatively large olfactory bulbs in comparison to other known stem birds, suggesting that olfaction was an important aspect of Jeholornis ecology. The digitally reconstructed scleral ring suggests a strongly diurnal habit, supporting the hypothesis that early-diverging birds were predominantly active during the day.

Enjoy,

Fred

 

[Fred Ruhe]

Data from a large sample size of specimens reveal the dental formula of J. prima to be 0–2–3 (premaxillary–maxillary–dentary tooth counts), contrary to previous suggestions that the presence of maxillary teeth is diagnostic of a separate species, Jeholornapenis.

On this remark the authors write: "The dentition and potential variation of the dentition of Jeholornis have previously been unclear. Among most previously published specimens of Jeholornis, the dentition is described as having zero to three dentary teeth and lacking teeth in the upper jaw (Supporting Information, Table S1; Ji et al., 2002b; Zhou & Zhang, 2002, 2003; Lefèvre et al., 2014; Wang et al., 2020a) or ambiguously, with ‘a few small, blunt teeth on the back of the upper jaw’ (Chiappe & Meng, 2016). Therefore, the presence of maxillary teeth was used as one of the diagnostic features of a new species of Jeholornis, J. palmapenis (O’Connor et al., 2012). The 3D scans of Jeholornis STM 3-8 allow assessment of the number of alveoli present, revealing that the dental formula in this individual is 0–2–3, which is confirmed to be the complete dentition of Jeholornis based on our observation of a large sample size of this lineage. The presence of maxillary dentition is thus not considered to be diagnostic of J. palmapenis. Other purported interspecific differences currently used to support different species of jeholornithiforms are also subtle (Zhou & Zhang, 2002; O’Connor et al., 2012; Lefèvre et al., 2014; Wang et al., 2020a). However, a detailed investigation of the taxonomy of the Jeholornithiformes is beyond the scope of the present study of cranial anatomy."

Fred