Description of a cranial endocast from a fossil platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the relevance of endocranial characters to monotreme monophyly.
J Morphol. 2006 Aug; 267(8):1000-15.JM

Abstract

A digital cranial endocast of the Miocene platypus Obdurodon dicksoni was extracted from high-resolution X-ray computed tomography scans. This endocast represents the oldest from an unequivocal member of either extant monotreme lineage and is therefore important for inferring character support for Monotremata, a clade that is not well diagnosed. We describe the Obdurodon endocast with reference to endocasts extracted from skulls of the three species of extant monotremes, particularly Ornithorhynchus anatinus, the duckbill platypus. We consulted published descriptions and illustrations of whole and sectioned brains of monotremes to determine which external features of the nervous system are represented on the endocasts. Similar to Ornithorhynchus, well-developed parafloccular casts and reduced olfactory bulb casts are present in the Obdurodon endocast. Reduction of the olfactory bulbs in comparison with tachyglossids and therian mammals is a potential apomorphy for Ornithorhynchidae. The trigeminal nuclei, ganglia, and nerves (i.e., trigeminal complex) are enlarged in Obdurodon, as evidenced by their casts on the endocast, as is the case in the extant platypus. The visibility of enlarged trigeminal nucleus casts on the endocasts of Obdurodon and Ornithorhynchus is a possible synapomorphy of Ornithorhynchidae. Electroreception and enlargement of the trigeminal complex are possible synapomorphies for Monotremata.

Authors+Show Affiliations

Macrini TE

Jackson School of Geosciences and University of Texas High-Resolution X-ray Computed Tomography Facility, University of Texas at Austin, 78712, USA. tmacrini@mail.utexas.edu

Rowe T

No affiliation info available

Archer M

No affiliation info available

MeSH

AnimalsFossilsMonotremataPlatypusRadiographySkullSpecies Specificity

Pub Type(s)

Comparative Study

Journal Article

Research Support, Non-U.S. Gov't

Research Support, U.S. Gov't, Non-P.H.S.

Language

eng

PubMed ID

16710845

Citation

Macrini, Thomas E., et al. "Description of a Cranial Endocast From a Fossil Platypus, Obdurodon Dicksoni (Monotremata, Ornithorhynchidae), and the Relevance of Endocranial Characters to Monotreme Monophyly." Journal of Morphology, vol. 267, no. 8, 2006, pp. 1000-15.

Macrini TE, Rowe T, Archer M. Description of a cranial endocast from a fossil platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the relevance of endocranial characters to monotreme monophyly. J Morphol. 2006;267(8):1000-15.

Macrini, T. E., Rowe, T., & Archer, M. (2006). Description of a cranial endocast from a fossil platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the relevance of endocranial characters to monotreme monophyly. Journal of Morphology, 267(8), 1000-15.

Macrini TE, Rowe T, Archer M. Description of a Cranial Endocast From a Fossil Platypus, Obdurodon Dicksoni (Monotremata, Ornithorhynchidae), and the Relevance of Endocranial Characters to Monotreme Monophyly. J Morphol. 2006;267(8):1000-15. PubMed PMID: 16710845.

* Article titles in AMA citation format should be in sentence-case

TY - JOUR T1 - Description of a cranial endocast from a fossil platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the relevance of endocranial characters to monotreme monophyly. AU - Macrini,Thomas E, AU - Rowe,Timothy, AU - Archer,Michael, PY - 2006/5/20/pubmed PY - 2006/9/9/medline PY - 2006/5/20/entrez SP - 1000 EP - 15 JF - Journal of morphology JO - J Morphol VL - 267 IS - 8 N2 - A digital cranial endocast of the Miocene platypus Obdurodon dicksoni was extracted from high-resolution X-ray computed tomography scans. This endocast represents the oldest from an unequivocal member of either extant monotreme lineage and is therefore important for inferring character support for Monotremata, a clade that is not well diagnosed. We describe the Obdurodon endocast with reference to endocasts extracted from skulls of the three species of extant monotremes, particularly Ornithorhynchus anatinus, the duckbill platypus. We consulted published descriptions and illustrations of whole and sectioned brains of monotremes to determine which external features of the nervous system are represented on the endocasts. Similar to Ornithorhynchus, well-developed parafloccular casts and reduced olfactory bulb casts are present in the Obdurodon endocast. Reduction of the olfactory bulbs in comparison with tachyglossids and therian mammals is a potential apomorphy for Ornithorhynchidae. The trigeminal nuclei, ganglia, and nerves (i.e., trigeminal complex) are enlarged in Obdurodon, as evidenced by their casts on the endocast, as is the case in the extant platypus. The visibility of enlarged trigeminal nucleus casts on the endocasts of Obdurodon and Ornithorhynchus is a possible synapomorphy of Ornithorhynchidae. Electroreception and enlargement of the trigeminal complex are possible synapomorphies for Monotremata. SN - 0362-2525 UR - https://www.unboundmedicine.com/medline/citation/16710845/Description_of_a_cranial_endocast_from_a_fossil_platypus_Obdurodon_dicksoni__Monotremata_Ornithorhynchidae__and_the_relevance_of_endocranial_characters_to_monotreme_monophyly_ DB - PRIME DP - Unbound Medicine ER -

Tags

Description of a cranial endocast from a fossil platypus, Obdurodon dicksoni (Monotremata, Ornithorhynchidae), and the relevance of endocranial characters to monotreme monophyly.J Morphol. 2006 Aug; 267(8):1000-15.JM