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The oldest platypus and its bearing on divergence timing of the platypus and echidna clades.
Proc Natl Acad Sci U S A. 2008 Jan 29; 105(4):1238-42.PN

Abstract

Monotremes have left a poor fossil record, and paleontology has been virtually mute during two decades of discussion about molecular clock estimates of the timing of divergence between the platypus and echidna clades. We describe evidence from high-resolution x-ray computed tomography indicating that Teinolophos, an Early Cretaceous fossil from Australia's Flat Rocks locality (121-112.5 Ma), lies within the crown clade Monotremata, as a basal platypus. Strict molecular clock estimates of the divergence between platypus and echidnas range from 17 to 80 Ma, but Teinolophos suggests that the two monotreme clades were already distinct in the Early Cretaceous, and that their divergence may predate even the oldest strict molecular estimates by at least 50%. We generated relaxed molecular clock models using three different data sets, but only one yielded a date overlapping with the age of Teinolophos. Morphology suggests that Teinolophos is a platypus in both phylogenetic and ecological aspects, and tends to contradict the popular view of rapid Cenozoic monotreme diversification. Whereas the monotreme fossil record is still sparse and open to interpretation, the new data are consistent with much slower ecological, morphological, and taxonomic diversification rates for monotremes than in their sister taxon, the therian mammals. This alternative view of a deep geological history for monotremes suggests that rate heterogeneities may have affected mammalian evolution in such a way as to defeat strict molecular clock models and to challenge even relaxed molecular clock models when applied to mammalian history at a deep temporal scale.

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Authors+Show Affiliations

Rowe T
Jackson School of Geosciences, University of Texas, C1100, Austin, TX 78712, USA.
Rich TH
No affiliation info available
Vickers-Rich P
No affiliation info available
Springer M
No affiliation info available
Woodburne MO
No affiliation info available

MeSH

AnimalsAustraliaEvolution, MolecularFossilsPhylogenyPlatypusTachyglossidaeTimeTomography, X-Ray Computed

Pub Type(s)

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

Language

eng

PubMed ID

18216270

Citation

Rowe, Timothy, et al. "The Oldest Platypus and Its Bearing On Divergence Timing of the Platypus and Echidna Clades." Proceedings of the National Academy of Sciences of the United States of America, vol. 105, no. 4, 2008, pp. 1238-42.
Rowe T, Rich TH, Vickers-Rich P, et al. The oldest platypus and its bearing on divergence timing of the platypus and echidna clades. Proc Natl Acad Sci U S A. 2008;105(4):1238-42.
Rowe, T., Rich, T. H., Vickers-Rich, P., Springer, M., & Woodburne, M. O. (2008). The oldest platypus and its bearing on divergence timing of the platypus and echidna clades. Proceedings of the National Academy of Sciences of the United States of America, 105(4), 1238-42. https://doi.org/10.1073/pnas.0706385105
Rowe T, et al. The Oldest Platypus and Its Bearing On Divergence Timing of the Platypus and Echidna Clades. Proc Natl Acad Sci U S A. 2008 Jan 29;105(4):1238-42. PubMed PMID: 18216270.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - The oldest platypus and its bearing on divergence timing of the platypus and echidna clades. AU - Rowe,Timothy, AU - Rich,Thomas H, AU - Vickers-Rich,Patricia, AU - Springer,Mark, AU - Woodburne,Michael O, Y1 - 2008/01/23/ PY - 2008/1/25/pubmed PY - 2008/2/26/medline PY - 2008/1/25/entrez SP - 1238 EP - 42 JF - Proceedings of the National Academy of Sciences of the United States of America JO - Proc Natl Acad Sci U S A VL - 105 IS - 4 N2 - Monotremes have left a poor fossil record, and paleontology has been virtually mute during two decades of discussion about molecular clock estimates of the timing of divergence between the platypus and echidna clades. We describe evidence from high-resolution x-ray computed tomography indicating that Teinolophos, an Early Cretaceous fossil from Australia's Flat Rocks locality (121-112.5 Ma), lies within the crown clade Monotremata, as a basal platypus. Strict molecular clock estimates of the divergence between platypus and echidnas range from 17 to 80 Ma, but Teinolophos suggests that the two monotreme clades were already distinct in the Early Cretaceous, and that their divergence may predate even the oldest strict molecular estimates by at least 50%. We generated relaxed molecular clock models using three different data sets, but only one yielded a date overlapping with the age of Teinolophos. Morphology suggests that Teinolophos is a platypus in both phylogenetic and ecological aspects, and tends to contradict the popular view of rapid Cenozoic monotreme diversification. Whereas the monotreme fossil record is still sparse and open to interpretation, the new data are consistent with much slower ecological, morphological, and taxonomic diversification rates for monotremes than in their sister taxon, the therian mammals. This alternative view of a deep geological history for monotremes suggests that rate heterogeneities may have affected mammalian evolution in such a way as to defeat strict molecular clock models and to challenge even relaxed molecular clock models when applied to mammalian history at a deep temporal scale. SN - 1091-6490 UR - https://www.unboundmedicine.com/medline/citation/18216270/The_oldest_platypus_and_its_bearing_on_divergence_timing_of_the_platypus_and_echidna_clades_ DB - PRIME DP - Unbound Medicine ER -