Medullary bone in an Early Cretaceous enantiornithine bird and discussion regarding its identification in fossils
Open accessAbstract
Medullary bone is an ephemeral type of bone tissue, today found only in sexually mature female birds, that provides a calcium reservoir for eggshell formation. The presence of medullary bone-like tissues in extant birds, pterosaurs, and dinosaurs distantly related to birds shows that caution must be exercised before concluding that fossils bear medullary bone. Here we describe a new specimen of pengornithid enantiornithine from the Lower Cretaceous Jiufotang Formation. Consisting of an isolated left hindlimb, the three-dimensional preservation contrasts with the crushed preservation characteristic of most Jehol specimens. Histological examinations suggest this resulted from the presence of a thick layer of highly vascular bone spanning the medullary cavities of the femur and tibiotarsus, consistent with expectations for medullary bone in extant birds. Micro-computed tomographic scans reveal small amounts of the same tissue extending into the pedal phalanges. We consider the tissue to be homologous to the medullary bone of Neornithines.
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Integrity signals
Registry
Cites
Statistics
Claims the paper makes
The claims and statistics of this paper haven’t been checked yet.
Run the check — free, no account needed. It reads the open-access text and checks the sources it cites.
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
There is no strong evidence of molt in Archaeopteryx.
“Contra some reports, there is no strong evidence of molt [109].”
From The ecology of Archaeopteryx (2026) · cites this paper as [109]
The Results (Identification; page unavailable) mention weakly preserved feathers in a pengornithid specimen, while the Discussion concerns medullary bone and reproductive maturity. Searches for Archaeopteryx, molt, and molting found no passage assessing evidence of molt in Archaeopteryx. (LLM, conf=0.75)
Experimental — accuracy not yet measured
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
The self-check needs the paper’s full text.
Cites
Archaeopteryx and the origin of birds
OSTROM, J. H. (1976) · Biological Journal of the Linnean Society · doi:10.1111/j.1095-8312.1976.tb00244.x · Cited by 361 · see citing works
Was Dinosaurian Physiology Inherited by Birds? Reconciling Slow Growth in Archaeopteryx
Erickson, G. M., Rauhut, O. W. M., Zhou, Z., Turner, A. H., Inouye, B. D., Hu, D., & Norell, M. A. (2009) · PLoS ONE · doi:10.1371/journal.pone.0007390 · Cited by 195 · see citing works
Self-citationAvian Evolution: The Fossil Record of Birds and Its Paleobiological Significance
Mayr, G. (2016) · doi:10.1002/9781119020677 · Cited by 102 · see citing works
Flagged first, then by citations
Research works printed but not linked: 33
- [1]Bloom W Bloom MA McLean FC Calcification and ossification. Medullary bone changes in the reproductive cycle of female pigeons Anat. Rec. 1941 81 443 475 10.1002/ar.1090810404 · DOI
- [2]Taylor TG Moore JH Avian medullary bone Nature 1953 172 504 505 10.1038/172504a0 · DOI
- [4]Yamamoto T Nakamura H Tsuji T Hirata A Ultracytochemical study of medullary bone calcification in estrogen injected male Japanese quail Anat. Rec. 2001 264 25 31 10.1002/ar.1101 11505368 · DOI
- [5]Schweitzer MH Elsey RM Dacke CG Horner JR Lamm ET Do egg-laying crocodilian (Alligator mississippiensis) archosaurs form medullary bone? Bone 2007 40 1152 1158 10.1016/j.bone.2006.10.029 17223615 · DOI
- [6]Schweitzer MH Wittmeyer JL Horner JR Gender-specific reproductive tissue in ratites and Tyrannosaurus rex Science 2005 308 1456 1460 10.1126/science.1112158 15933198 · DOI
- [8]Ostrom, J. H. in Problèmes Actuels de Paléontologie (Évolution des Vertébrés) Vol. 218 Colloque International C.N.R.S. (Lehman, J. P. ed) 519-532 (Centre National de la Recherche Scientifique, Paris, France, 1975).
- [9]Lee AH Werning S Sexual maturity in growing dinosaurs does not fit reptilian growth models Proc. Natl Acad. Sci. USA 2008 105 582 587 10.1073/pnas.0708903105 18195356 PMC2206579 · DOI
- [10]Hübner TR Bone histology in Dysalotosaurus lettowvorbecki (Ornithischia: Iguanodontia)—variation, growth, and implications PLoS ONE 2012 7 e29958 10.1371/journal.pone.0029958 22238683 PMC3253128 · DOI
- [13]Chinsamy A Cerda IA Powell JE Vascularised endosteal bone tissue in armoured sauropod dinosaurs Sci. Rep. 2016 6 1 9 10.1038/srep24858 27112710 PMC4845056 · DOI
- [14]Chinsamy A Codorniu L Chiappe LM Palaeobiological implications of the bone histology of Pterodaustro guinazui Anat. Rec. 2009 292 1462 1477 10.1002/ar.20990 19711478 · DOI
- [17]Carter, D. R. & Beaupre, G. Skeletal function and form: mechanobiology of skeletal development, aging, and regeneration. (Cambridge University Press, Cambridge, 2001).
- [18]Chinsamy A Tumarkin-Deratzian A Pathologic bone tissues in a turkey vulture and a nonavian dinosaur: implications for interpreting endosteal bone and radial fibrolamellar bone in fossil dinosaurs Anat. Rec. 2009 292 1478 1848 10.1002/ar.20991 19711479 · DOI
- [19]Prondvai E Medullary bone in fossils: function, evolution and significance in growth curve reconstructions of extinct vertebrates J. Evol. Biol. 2016 30 440 460 10.1111/jeb.13019 27862520 · DOI
- [20]Cerda IA Chinsamy A Pol D Unusual endosteally formed bone tissue in a Patagonian basal sauropodomorph dinosaur Anat. Rec. 2014 297 1385 1391 10.1002/ar.22954 24863550 · DOI
- [21]Schweitzer MH Zheng WX Zanno LE Werning S Sugiyama T Chemistry supports the identification of gender specific reproductive tissue in Tyrannosaurus rex Sci. Rep. 2016 6 1 10 10.1038/srep23099 26975806 PMC4791554 · DOI
- [25]Pan YH Sha JG Zhou ZH Fürsich FT The Jehol Biota: definition and distribution of exceptionally preserved relicts of a continental Early Cretaceous ecosystem. Cretaceous Res. 2008 44 30 38 10.1016/j.cretres.2013.03.007 · DOI
- [27]Hu H O’Connor JK Zhou ZH A new species of Pengornithidae (Aves: Enantiornithes) from the Lower Cretaceous of China suggests a specialized scansorial habitat previously unknown in early birds PLoS ONE 2015 10 e0126791 10.1371/journal.pone.0126791 26039693 PMC4454694 · DOI
- [28]Zhou Z Clarke J Zhang F Insight into diversity, body size and morphological evolution from the largest Early Cretaceous enantiornithine bird. J. Anat. 2008 212 565 577 10.1111/j.1469-7580.2008.00880.x 18397240 PMC2409080 · DOI
- [30]Chinsamy A Chiappe LM Dodson P Mesozoic avian bone microstructure: physiological implications Paleobiology 1995 21 561 574 10.1017/S0094837300013543 · DOI
- [31]Baumel, J. J. & Witmer, L. M. in Handbook of Avian Anatomy: Nomina Anatomica Avium, Second Edition Vol. 23 Publications of the Nuttall Ornithological Club (J. J. Baumel et al eds) 45-132 (Nuttall Ornithological Club, Cambridge, MA, 1993).
- [32]Hutchinson JR The evolution of femoral osteology and soft tissues on the line to extant birds (Neornithes) Zool. J. Linn. Soc. 2001 131 169 197 10.1111/j.1096-3642.2001.tb01314.x · DOI
- [34]Teitelbaum SL Bone resorption by osteoclasts Science 2000 289 1504 1508 10.1126/science.289.5484.1504 10968780 · DOI · Paper page
- [35]Ascenzi A François C Bocciarelli DS On the bone induced by estrogens in birds J. Ultrastruct. Res. 1963 8 491 505 10.1016/S0022-5320(63)80051-9 13965115 · DOI
- [36]Kerschnitzki M Rapid alterations of avian medullary bone material during the daily egg-laying cycle Bone 2014 69 109 117 10.1016/j.bone.2014.08.019 25204794 · DOI
- [37]Chinsamy A Chiappe LM Marugán-Lobón J Gao CH Zhang FJ Gender identification of the Mesozoic bird Confuciusornis sanctus Nat. Commun. 2013 4 1 5 10.1038/ncomms2377 23340421 · DOI
- [39]Erickson GM Rogers KC Varricchio DJ Norell MA Xu X Growth patterns in brooding dinosaurs reveals the timing of sexual maturity in non-avian dinosaurs and genesis of the avian condition Biol. Lett. 2007 3 558 561 10.1098/rsbl.2007.0254 17638674 PMC2396186 · DOI
- [40]Gill, F. B. Ornithology, 3rd Edition. (W.H. Freeman and Company, New York, 2007).
- [41]Bourdon E Bone growth marks reveal protracted growth in New Zealand kiwi (Aves, Apterygidae) Biol. Lett. 2009 5 1 4 10.1098/rsbl.2009.0310 PMC2781955 19515655 · DOI
- [42]Hu H O’Connor JK First species of Enantiornithes from Sihedang elucidates skeletal development in Early Cretaceous enantiornithines J. Syst. Palaeontol. 2017 15 909 926 10.1080/14772019.2016.1246111 · DOI
- [43]Mayr Gerald Avian Evolution 2016 Chichester, UK John Wiley & Sons, Ltd
- [44]Zheng XT Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour Nature 2013 495 507 511 10.1038/nature11985 23503663 · DOI
- [45]O’Connor JK Zheng XT Wang XL Wang Y Zhou ZH Ovarian follicles shed new light on dinosaur reproduction during the transition towards birds Natl. Sci. Rev. 2014 1 15 17 10.1093/nsr/nwt012 · DOI
- [46]Wang Y A new Jehol enantiornithine bird with three- dimensional preservation and ovarian follicles J. Vertebr. Paleontol. 2016 36 e1054496 10.1080/02724634.2015.1054496 · DOI
Cited by
Sorted by citations
A high-resolution growth series of Tyrannosaurus rex obtained from multiple lines of evidence
Carr, T. D. (2020) · PeerJ · doi:10.7717/peerj.9192 · Cited by 93 · see citing works
“This test is not dependent upon MOR 1125 being a female (O’Connor et al., 2018); if in actuality it is a male, then the set of shared characters would be evidence of that sex.”
BackgroundDinosaur paleohistology: review, trends and new avenues of investigation
Bailleul, A. M., O'Connor, J., & Schweitzer, M. (2019) · PeerJ · doi:10.7717/peerj.7764/fig-1 · Cited by 50
“…that unambiguous identification of fossil tissues as reproductive MB requires more than just morphological similarity, particularly with increasing phylogenetic distance from the avian lineage, and/ or when it appears in patterns different from those seen in extant birds (O’Connor et al., 2018).”
BackgroundInfluentialSelf-citationCanoville, A., Schweitzer, M. H., & Zanno, L. E. (2019) · BMC Evolutionary Biology · doi:10.1186/s12862-019-1402-7 · Cited by 64 · see citing works
“The purported nature and reproductive function of some of these endosteal tissues were also challenged based, in part, on their unusual anatomical locations (such as within the mandibular symphyses of pterosaur specimens [19, 23]; see also [27, 33, 34]).”
BackgroundAn Early Cretaceous enantiornithine (Aves) preserving an unlaid egg and probable medullary bone
Bailleul, A. M., O'Connor, J., Zhang, S.-K., Li, Z.-H., Wang, Q., Lamanna, M., Zhu, X., & Zhou, Z.-H. (2019) · Nature Communications · doi:10.1038/s41467-019-09259-x · Cited by 42 · see citing works
Self-citationOsteohistology and Life History of the Basal Pygostylian, Confuciusornis sanctus
Chinsamy, A., Marugán‐Lobón, J., Serrano, F. J., & Chiappe, L. M. (2019) · The Anatomical Record · doi:10.1002/ar.24282 · Cited by 42 · see citing works
Wang, M., O'Connor, J. K., Bailleul, A. M., & Li, Z. (2019) · National Science Review · doi:10.1093/nsr/nwz214 · Cited by 35 · see citing works
Self-citationPalaeoecological deductions from osteohistology
Chinsamy, A. (2023) · Biology Letters · doi:10.1098/rsbl.2023.0245 · Cited by 31 · see citing works
“The identification of medullary bone in Mesozoic birds began with the tissue first being recognized in Confuciusornis [118], and has since been identified in a few other enantiornithine taxa (a pengornithid [119], Miruavis [120]) and Avimaia [121]).”
Identifying medullary bone in extinct avemetatarsalians: challenges, implications and perspectives
Canoville, A., Schweitzer, M. H., & Zanno, L. E. (2020) · Philosophical Transactions of the Royal Society B Biological Sciences · doi:10.1098/rstb.2019.0133 · Cited by 27 · see citing works
An oviraptorosaur adult-egg association from the Cretaceous of Jiangxi Province, China
Jin, X., Varricchio, D. J., Poust, A. W., & He, T. (2019) · Journal of Vertebrate Paleontology · doi:10.1080/02724634.2019.1739060 · Cited by 22 · see citing works
“, 2005; Lee and Werning, 2008; Hübner, 2012), enantiornithine birds (O’Connor et al., 2018; Bailleul et al., 2019), and possibly two pterosaurs (Chinsamy et al.”
The Evolution of Feathers: From Their Origin to the Present
Rauhut, O. (2020) · doi:10.1007/978-3-030-27223-4 · Cited by 21
O'Connor, J. K. (2020) · Fascinating life sciences · doi:10.1007/978-3-030-27223-4_9 · Cited by 19 · see citing works
Self-citationWu, Q., Bailleul, A. M., Li, Z., O’Connor, J., & Zhou, Z. (2021) · Frontiers in Earth Science · doi:10.3389/feart.2021.617124 · Cited by 16 · see citing works
Self-citationChinzorig, T., Beguesse, K. A., Canoville, A., Phillips, G. E., & Zanno, L. E. (2022) · The Anatomical Record · doi:10.1002/ar.25069 · Cited by 15 · see citing works
Wang, X., Cau, A., Luo, X., Kundrát, M., Wu, W., Ju, S., Guo, Z., Liu, Y.-C., & Ji, Q. (2022) · Journal of Paleontology · doi:10.1017/jpa.2022.12 · Cited by 14
Chinsamy, A., Handley, W. D., & Worthy, T. H. (2022) · The Anatomical Record · doi:10.1002/ar.25047 · Cited by 10 · see citing works
“Over the past two decades there have been several studies on the bone histology of extinct birds (e.g., Atterholt et al., 2021; Canoville et al., 2022; Chinsamy, 1994, 2002; Chinsamy et al., 2013, 2019, 2020; Chinsamy & Worthy, 2021; de Ricqlès et al., 2001; O'Connor et al., 2018; Wang et al., 2020).”
BackgroundA new theropod dinosaur from the Callovian Balabansai Formation of Kyrgyzstan
Rauhut, O. W. M., Bakirov, A. A., Wings, O., Fernandes, A. E., & Hübner, T. (2024) · Zoological Journal of the Linnean Society · doi:10.1093/zoolinnean/zlae090 · Cited by 12 · see citing works
Osteohistological description of ostrich and emu long bones, with comments on markers of growth
Ong, N., Hart-Farrar, B., Tremaine, K., & Woodward, H. N. (2022) · Journal of Anatomy · doi:10.1111/joa.13665 · Cited by 9 · see citing works
O'Connor, J., Stidham, T., Harris, J., Lamanna, M., Bailleul, A. M., Hu, H., Wang, M., & You, H. (2021) · Journal of Systematics and Evolution · doi:10.1111/jse.12823 · Cited by 7 · see citing works
“In fact, such three‐ dimensional preservation, when reported in Jehol specimens (including one from Sihedang), is usually the result of the preservation of medullary bone (O'Connor et al., 2018; Wang et al., 2020a).”
BackgroundSelf-citationO’Connor, J. K., Atterholt, J., Bailleul, A. M., Wang, M., Kuo, P.-C., & Zhou, Z. (2025) · Geobios · doi:10.1016/j.geobios.2024.05.004 · Cited by 6 · see citing works
Self-citationde Andrade, R. C. L. P., Sena, M. V. D. A., Brum, A. S., Campos, D. D. A., Kellner, A. W. A., Bantim, R. A. M., & Sayão, J. M. (2023) · Journal of South American Earth Sciences · doi:10.1016/j.jsames.2023.104363 · Cited by 8 · see citing works
Keratan sulfate as a marker for medullary bone in fossil vertebrates
Canoville, A., Zanno, L. E., Zheng, W., & Schweitzer, M. (2021) · Journal of Anatomy · doi:10.1111/joa.13388 · Cited by 5 · see citing works
Osteohistology of Enantiornithine Birds from the Lower Cretaceous Xiagou Formation
Atterholt, J., O'Connor, J., & You, H. (2025) · Geobios · doi:10.1016/j.geobios.2024.08.020 · Cited by 3 · see citing works
“…Pterygornis dapingfangensis (IVPP V16363; Wang et al., 2017a), Cruralispennia multidonta (IVPP V21711; Wang et al., 2017b), indeterminate pengornithid (IVPP V15576A; O’Connor et al., 2018), Mirusavis parvus (IVPP V18692; Wang et al., 2020), and Musiavis amabilis (MHGU-3000; Wang et al., 2022).”
InfluentialSelf-citationCrane, A. H., Baldry, C., Rankin, K. E., Clarkin, C. E., Williams, K. A., & Gostling, N. J. (2025) · Developmental Biology · doi:10.1016/j.ydbio.2025.02.007 · Cited by 1 · see citing works
Kundrát, M., Horváth, D., Wang, Z., & Wang, X. (2024) · Cretaceous Research · doi:10.1016/j.cretres.2024.105839 · Cited by 1 · see citing works
O’Connor, J. K., & Clark, A. D. (2026) · Discover Ecology · doi:10.1007/s44396-026-00026-z
Self-citationProgress and future directions in dinosaur palaeontology
Xu, X., Upchurch, P., Zanno, L. E., McNamara, M. E., Qin, Z., & Benton, M. (2026) · Nature Reviews Biodiversity · doi:10.1038/s44358-026-00191-9
Evidence of male anatomy in a mid-Cretaceous Burmese miniaturised amber gecko
Daza, J. D., Stelling, E. G., Jenkins, K. M., Stanley, E., Doucet, D., Fotanarrosa, G., & Bauer, A. M. (2026) · Swiss Journal of Palaeontology · doi:10.3897/sjp.145.188227
Teryak, G. M., Elbakry, A. M., Abuelsaad, A., Mohamed, A. E., Abo-Eleneen, R. E. H., & Mohamed, T. (2026) · Zoology · doi:10.1016/j.zool.2026.126339
Pasnichenko, O., Sobek, Z., Tkachuk, S., Yatsenko, I., & Bokotko, R. (2022) · Ukrainian journal of veterinary sciences · doi:10.31548/ujvs.13(2).2022.35-45
Ksepka, D. T. (2021) · Elsevier eBooks · doi:10.1016/b978-0-12-819770-7.00009-8 · Cited by 3 · see citing works
- Authors
- O’Connor, J., Erickson, G. M., Norell, M., Bailleul, A. M., Hu, H., & Zhou, Z.
- Affiliations
- Florida State University (US)
- American Museum of Natural History (US)
- Chinese Academy of Sciences (CN)
- University of New England (AU)
- Venue
- Nature Communications
- Published
- 2018-12-05
- Volume
- 9
- Issue
- 1
- Pages
- 5169-5169
- ISSN
- 2041-1723 (ISSN-L)
- PMC
- PMC6281594
- OpenAlex
- W2903405620
- Cited by
- 36
- References
- 44
- Citations by year
- 2026: 3 · 2025: 2 · 2024: 4 · 2023: 3 · 2022: 5 · 2021: 4 · 2020: 9 · 2019: 6
- FWCI
- 3.50
- Type
- journal article
- Language
- en
- Open access
- gold
- doi.org
- Locations
- Nature Communications (publishedVersion, cc-by)
- Europe PMC (PubMed Central) (publishedVersion, other-oa)
- PubMed Central (publishedVersion, cc-by)
- PubMed (publishedVersion)
- RePEc: Research Papers in Economics (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
- DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
- RUNE (Research UNE) (submittedVersion, cc-by)
- Funders
- National Science Foundation (0207744)
- National Natural Science Foundation of China (grant number 41688103, #41688103)
- Topics
- Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Evolutionary Biology
- Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Fossil Insects in Amber
- Health Sciences › Medicine › Urology › Comparative Animal Anatomy Studies
- Keywords
- medullary bone, Enantiornithes, Early Cretaceous birds, Jiufotang Formation, femur, tibiotarsus, pedal phalanges, bone histology, eggshell formation, fossil identification, three-dimensional preservation
- MeSH terms
- Animals, Birds, Biological Evolution, Female, Fossils, Hindlimb, History, Ancient
About these checks
Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.
Statistics and arithmetic are recomputed, not judged.
Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.
What counts as a claim ›How we measure confidence ›How we check this ›
Are you an author, or do you see a problem with this page? Request a review
