{ "abstract": "The enantiornithes, a group of Mesozoic birds, have morphological features suggesting a precocial mode of development; however, their detailed physiological characteristics, particularly hatchling metabolic rates, have yet to be explored. Here, we retrodicted metabolic rates for four Lower Cretaceous enantiornithines: one hatchling, one adult from Las Hoyas, one early post-hatching juvenile and one post-juvenile individual from the Jehol Biota, using phylogenetic comparative analyses and a comprehensive dataset of extant birds spanning the altricial–precocial spectrum. By examining vascular density (related to resting metabolic rate (RMR)) and nutrient foraminal size (proportional to blood flow rate) as proxies, we inferred the metabolic scope of the hatchling enantiornithine and determined that it fell toward the precocial end of the altricial–precocial spectrum. The RMR values of the two enantiornithine chicks were retrodicted as 0.67 mlO2 h–1 g–0.93. The peak metabolic rate (PMR) retrodicted is twice the resting metabolism for the Las Hoyas hatchling. These results are consistent with a semi-precocial/precocial development characterized by independent locomotion by climbing using the wing claws soon after hatching. However, flapping flight may have been delayed, owing to incomplete ossification of the sternum, as observed in one hatchling specimen.", "abstract_shown": true, "affiliations": [ "Sorbonne Université, Muséum national d'Histoire naturelle, CNRS, Centre de Recherche en Paléontologie—Paris (CR2P, UMR 7207) 1 , 4 Place Jussieu, 75005 Paris, Île-de-France, France", "Morton K. Blaustein Department of Earth & Planetary Sciences, Johns Hopkins University 2 , Baltimore, ML, USA", "Departamento de Paleobiología, Museo Nacional de Ciencias Naturales—CSIC, Madrid, Spain 3", "Frisian Museum of Natural History, Leeuwarden, The Netherlands 4", "European Synchrotron Radiation Facility 5 , Grenoble, Auvergne-Rhône-Alpes, France", "Department of Organismal Biology, Subdepartment of Evolution and Development, Uppsala University, Uppsala, Uppsala County 6 , Sweden", "Key Laboratory of Vertebrate Evolution and Human Origins, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences 7 , Beijing, People's Republic of China", "Université Lyon 1, ENS de Lyon, Université Jean Monnet, CNRS, LGL TPE 8 , UMR 5276, Villeurbanne, Auvergne-Rhône-Alpes, France", "Laboratório de Sistemática e Tafonomia de Vertebrados Fósseis (LAPUG), Departamento de Geologia e Paleontologia, Museu Nacional, Universidade Federal do Rio de Janeiro 9 , Brazil", "Dinosaur Institute, Natural History Museum of Los Angeles County 10 , Los Angeles, CA, USA", "Departamento de Ecología y Geología, Facultad de Ciencias, Universidad de Málaga 11 , Málaga, Spain", "Unidad de Paleontología, Dpto. Biología, Universidad Autónoma de Madrid 12 , Madrid, Spain" ], "article_type": "research article", "arxiv": null, "author_total": 11, "authors": [ { "affs": [ 0, 1 ], "name": "Mariana V. Haase", "orcid": "0000-0003-4708-999X" }, { "affs": [ 2 ], "name": "Fabien Knoll", "orcid": "0000-0001-7822-8740" }, { "affs": [ 3, 4 ], "name": "Dennis Voeten", "orcid": "0000-0002-2090-2824" }, { "affs": [ 5 ], "name": "Sophie Sanchez", "orcid": "0000-0002-3611-6836" }, { "affs": [ 6 ], "name": "Zhiheng Li", "orcid": "0000-0002-6968-6982" }, { "affs": [ 7 ], "name": "Hugo Bert", "orcid": "0009-0003-0016-5702" }, { "affs": [ 8 ], "name": "Esaú V. de Araújo", "orcid": "0000-0003-3459-4495" }, { "affs": [ 9, 10 ], "name": "Francisco J. Serrano", "orcid": "0000-0003-2527-617X" }, { "affs": [ 10 ], "name": "Javier C. Terol", "orcid": "0009-0003-2225-4917" }, { "affs": [ 11 ], "name": "Jesús Marugán-Lobón", "orcid": "0000-0002-3766-8560" }, { "affs": [ 0 ], "name": "Jorge Cubo", "orcid": "0000-0002-8160-779X" } ], "bibtex": "https://research.draconitic.com/paper/6dzptjys6jpnc.bib", "cited_by": 0, "doi": "10.1098/rsos.260574", "fulltext_url": "https://europepmc.org/articles/PMC13682901", "id": "6dzptjys6jpnc", "issns": [ "2054-5703" ], "landing_url": "https://royalsocietypublishing.org/rsos/article/13/10/260574/483760/Metabolic-features-of-enantiornithines-Avialae", "language": "en", "licence": "CC-BY-4.0", "licence_label": "CC BY 4.0", "licence_source": "article", "licence_url": "https://creativecommons.org/licenses/by/4.0/", "metadata_licence": null, "native_subjects": [ [ "hal", "0.sde" ] ], "openalex": "W7140301490", "pdf_url": "https://royalsocietypublishing.org/rsos/article-pdf/doi/10.1098/rsos.260574/6171948/rsos.260574.pdf", "pmcid": "PMC13682901", "pmid": "42904298", "published": "2026-10-07", "publisher": "The Royal Society", "ris": "https://research.draconitic.com/paper/6dzptjys6jpnc.ris", "sources": [ { "first_seen": "2026-10-30T12:17:45Z", "native_id": "10.1098/rsos.260574", "source": "crossref", "url": "https://royalsocietypublishing.org/rsos/article/13/10/260574/483760/Metabolic-features-of-enantiornithines-Avialae" }, { "first_seen": "2026-10-30T12:18:01Z", "native_id": "hal-05835629", "source": "hal", "url": "https://hal.science/hal-05835629v1" }, { "first_seen": "2026-10-30T12:19:53Z", "native_id": "MED:42904298", "source": "europepmc", "url": "https://europepmc.org/article/MED/42904298" } ], "subjects": [ { "field": "earth", "origin": "hal:0.sde", "subfield": "environmental-science" } ], "title": "Metabolic features of enantiornithines (Avialae: Ornithothoraces): evidence supporting a semi-precocial/precocial developmental trajectory", "title_text": "Metabolic features of enantiornithines (Avialae: Ornithothoraces): evidence supporting a semi-precocial/precocial developmental trajectory", "type": "peer-reviewed", "updated_at": "2026-10-30T12:19:53Z", "url": "https://research.draconitic.com/paper/6dzptjys6jpnc", "venue": "Royal Society Open Science", "versions": [] }