TY - JOUR T1 - New information about the skull and dentary of the Miocene platypus Obdurodon dicksoni, and a discussion of ornithorhynchid relationships. AU - Musser,A M, AU - Archer,M, PY - 1998/8/28/pubmed PY - 1998/8/28/medline PY - 1998/8/28/entrez SP - 1063 EP - 79 JF - Philosophical transactions of the Royal Society of London. Series B, Biological sciences JO - Philos Trans R Soc Lond B Biol Sci VL - 353 IS - 1372 N2 - A reconstruction of the skull, dentary and dentition of the middle Miocene ornithorhynchid Obdurodon dicksoni has been made possible by acquisition of nearly complete cranial and dental material. Access to new anatomical work on the living platypus, Ornithorhynchus anatinus, and the present comparative study of the cranial foramina of Ob. dicksoni and Or. anatinus have provided new insights into the evolution of the ornithorhynchid skull. The hypertrophied bill in Ob. dicksoni is seen here as possibly apomorphic, although evidence from ontogenetic studies of Or. anatinus suggests that the basic form of the bill in Ob. dicksoni (where the rostral crura meet at the midline) may be ancestral to the form of the bill in Or. anatinus (where the rostral crura meet at the midline in the embryonic platypus but diverge in the adult). Differences in the relative positions of cranial structures, and in the relationships of certain cranial foramina, indicate that the cranium may have become secondarily shortened in Or. anatinus, possibly evolving from a more elongate skull type such as that of Ob. dicksoni. The plesiomorphic dentary of Ob. dicksoni, with well-developed coronoid and angular processes, contrasts with the dentary of Or. anatinus, in which the processes are almost vestigial, as well as with the dentary of the late Oligocene, congeneric Ob. insignis, in which the angular process appears to be reduced (the coronoid process is missing). In this regard the dentary of Ob. insignis seems to be morphologically closer to Or. anatinus than is the dentary of the younger Ob. dicksoni. Phylogenetic conclusions differ from previous analyses in viewing the northern Australian Ob. dicksoni as possibly derived in possessing a hypertrophied bill and dorsoventrally flattened skull and dentary, perhaps being a specialized branch of the Obdurodon line rather than ancestral to species of Ornithorhynchus. The presence of functional teeth and the robust, flattened skull and dentary in Ob. dicksoni argue for differences in diet and lifestyle between this extinct ornithorhynchid and the living Ornithorhynchus. SN - 0962-8436 UR - https://www.unboundmedicine.com/medline/citation/9720105/New_information_about_the_skull_and_dentary_of_the_Miocene_platypus_Obdurodon_dicksoni_and_a_discussion_of_ornithorhynchid_relationships_ L2 - https://royalsocietypublishing.org/doi/10.1098/rstb.1998.0266?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -