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7423785 
Journal Article 
Medullary bone-like tissue in the mandibular symphyses of a pterosaur suggests non-reproductive significance 
Prondvai, E; Stein, KHW; , 
2014 
1 
Scientific Reports
EISSN: 2045-2322 
NATURE PUBLISHING GROUP 
LONDON 
WOS:000341933200001 
Medullary bone is a special bone tissue forming on the endosteal surface of the medullary cavity in the bones of female birds prior to and during egg-laying to serve as a calcium reservoir for building the hard eggshell. It has also been identified in non-avian dinosaurs, where its presence is considered as a reliable indicator of a sexually mature female. Here, we reveal that multiple mandibular symphyses of the azhdarchid pterosaur Bakonydraco galaczi possess a special bone tissue that shows all microanatomical, histological, and developmental characteristics of medullary bone, despite its unusual location. Its frequent occurrence in the sample renders a pathologic origin unlikely. Our findings as well as the extremely thin-shelled eggs of pterosaurs suggest that this medullary bone-like tissue probably had a non-reproductive role in these animals. Although the non-reproductive significance and the anatomical location of this medullary bone-like tissue in Bakonydraco suggest independent evolutionary appearance from dinosaurian medullary bone, a common origin and later diverging function and physiological regulation is an equally viable phylogenetic hypothesis.