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Science 19 December 2008:
Vol. 322. no. 5909, pp. 1826 - 1828
DOI: 10.1126/science.1163245
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Reports

Avian Paternal Care Had Dinosaur Origin

David J. Varricchio1*, Jason R. Moore2, Gregory M. Erickson3, Mark A. Norell4, Frankie D. Jackson1 and John J. Borkowski5

1 Department of Earth Sciences, Montana State University, Bozeman, MT 59717, USA.
2 Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA.
3 Department of Biological Science, Florida State University, Tallahassee, FL 32306, USA.
4 Division of Paleontology, American Museum of Natural History, New York, NY 10024, USA.
5 Department of Mathematical Sciences, Montana State University, Bozeman, MT 59717, USA.


Figure 1 Fig. 1. Clutch volume versus adult body mass for extant archosaurs, divided into four taxon/care models (7). Species data points and corresponding regression lines are plotted together (A) or separately by model (B). Color code for all graphs: green, crocodile-maternal; black, bird-biparental; orange, bird-maternal; blue, bird-paternal; red diamonds, non-avian maniraptoran dinosaurs (Troodon, Oviraptor, and Citipati); red stars, other non-avian dinosaurs. No dinosaurs were included in the fitting of any regression lines. The three avian models (biparental, maternal, and paternal) are statistically distinct from each other (table S2). For birds, paternal care is associated with relatively larger clutch volumes than either biparental or maternal care over most body sizes; biparental care is associated with the smallest relative clutch volumes. The bird-paternal regression most likely accounts for the clutch volume–body mass relationship in Troodon and the two oviraptorids. [View Larger Version of this Image (20K GIF file)]
 

Figure 2 Fig. 2. Bone histology of clutch-associated Troodon formosus and Citipati osmolskae adults. (A) Troodon (Museum of the Rockies, MOR 748) right femur, tibia, and metatarsus (from left to right). Histologic examinations were conducted on an incomplete left leg. Color bars indicate relative position of thin-section microscope samples (blue, Troodon; yellow, equivalent position of Citipati sample) and fracture planes (red, Troodon) examined with dissecting scope. Scale bar, 10 cm. (B) Cross section of Citipati (Institute of Geology, Mongolia, IGM 100/979) femur from endosteum to periosteum (at top) showing fibrolamellar bone with lines of arrested growth, an external fundamental system, and no reproductive-associated tissues. Fractured zone with matrix and bone shards marks the middle of the section. Scale bar, 1 mm. (C and D) Troodon (MOR 748) tibia (C) and femur (D) composite cross sections consisting predominantly of fibrolamellar bone with minor amounts of endosteal lamellar bone. Both lack medullary bone and cortical erosion rooms. Fossil root or fungal traces (r) invade both bones; branching systems with largely micritic fill penetrate the exterior cortex, producing peripheral bands of irregular erosion and dark staining. Root damage, limited in the femur (right side), extends as a nearly complete circumferential band in the tibia. Scale bar, 10 mm. (E) Distribution of parental care systems (green, maternal; blue, paternal; black, biparental; gray, equivocal) in modern archosaurs and three clades of non-avian theropod dinosaurs. [View Larger Version of this Image (56K GIF file)]
 

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