PDF (Lo-Res) - Smithsonian Institution Libraries
Share Embed Flag
Download ePaper

PDF (Lo-Res) - Smithsonian Institution Libraries

PDF (Lo-Res) - Smithsonian Institution Libraries PDF (Lo-Res) - Smithsonian Institution Libraries

sil.si.edu
03.04.2013 Views

340 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY the Lower Cretaceous of China. Science, 255:845-848. Shubin, N.H. 1994. The Phylogeny of Development and the Origin of Homology. In L. Grande and O. Rieppel, Interpreting the Hierarchy of Nature, pages 201-225. New York: Academic Press. Smith, P.E., N.M. Evensen, D. York, S. Cumbaa, and D. Russell 1996. 40 Ar- 39 Ar Laser-Probe Dating of the Yixian Formation, Northeast China and the Early Evolution of Birds. Journal of Vertebrate Paleontology, 16(3):67A. Smith, P.E., N.M. Evensen, D. York, C. Mee-Mann, J. Fan, L. Jin-Ling, S. Cumbaa, and D. Russell 1995. Dates and Rates in Ancient Lakes 40 Ar- 39 Ar Evidence for an Early Cretaceous Age for the Jehol Group, Northeast China. Canadian Journal of Earth Sciences, 32:1426-1431. Steadman, D. 1983. Commentary on "The Origin and Early Radiation of Birds" (L. Martin). In A.H. Brush and G.A. Clark, Jr., editors, Perspectives in Ornithology, pages 338-344. Cambridge: Cambridge University Press. Varricchio, D.J., and L.M. Chiappe 1995. A New Bird from the Cretaceous Two Medicine Formation of Montana. Journal of Vertebrate Paleontology, 15( 1 ):201 -204. Walker, CA. 1981. New Subclass of Birds from the Cretaceous of South America. Nature, 292:51-53. Wellnhofer, P. 1994. New Data on the Origin and Early Evolution of Birds. Compte Rendus de I 'Academie des Sciences, Paris, 319(2):299-308. Zhou, Z. 1995a. Is Mononykus a Bird? Auk, 112(4):958-963. 1995b. The Discovery of Early Cretaceous Birds in China. In D. Stefan Peters, editor, Acta Palaeomithologica: 3 Symposium SAPE; 5 Internationale Senckenberg-Konferenze, 22-26 Juni 1992. Courier Forschungsinstitut Senckenberg, 181:9-22.

The Origin of Bird Flight: Roundtable Report Introduction Our charge during this roundtable disussion was to consider evidence, old and new, regarding the origin of flight in birds. This topic, one that many of us approach with what seems to be a genetically programmed fascination, had been broached numerous times in both the morning contributed paper session and during the previous two roundtables. To initiate discussion, Sankar Chatterjee kindly agreed to share an illustration summarizing several competing hypotheses regarding the transition from nonflying to flying forms. The ensuing hour focused on four general questions/themes: (1) were theropods capable of climbing; (2) what can claws tell us; (3) what are the limitations of the cursorial theory; and (4) do we have the right perspective? My first priority in this record is to reproduce the ideas and thoughts expressed by the participants and, whenever possible, to do so by reporting the conversation verbatim (from audioand videotapes made with the knowledge and cooperation of the participants). In some instances for clarity, I made editorial alterations that are not intended to change the meaning of what was said. I took the liberty to rearrange the order of some comments to group them within logical topical headings. The Roundtable Discussion 1. WERE THEROPODS CAPABLE OF CLIMBING?—Pondering the various scenarios for the origin of flight, Larry Martin asked Gregory Paul, "Do you think these (theropod) dinosaurs were good climbers or not? I would not have thought so from some of your reconstructions." Paul responded, "A good analogy would be a jaguar. If I were being chased by a jaguar, the jag could catch me on the ground. If I ran to a tree, the jag could climb the tree and catch me there as well. Jags are about the same size as the dromaeosaurs. The jaguar scenario suggests the situation for dromaeosaurs. I think they were very good mnners, but I also think they were good climbers, as is tme for many of these small theropods. My theory is that there G.E. Goslow, Jr., Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island 02912, United States. G.E. Goslow, Jr. 341 exists a group of small arboreal theropods from the Triassic or perhaps Jurassic that we have not found yet, because they will be very hard to find, that were good climbers. That's where you get Archaeopteryx from as well as some of the Cretaceous theropods. I agree with Sankar Chatterjee that overlapping fields of vision and large brains are not necessary for flight because pterosaurs do not have large brains, nor do insects. Nor do pterosaurs have overlapping binocular vision, but primates evolved these things in trees. [There] are other suggestions [that] these theropods were climbing; they had raptorial hands and three-toed feet with reversed hallux trackways, which suggests they could wrap this stucrure around. Even Tyrannosaurus has a reversed hallux trackway, so yes, I would agree that many of these small theropods could be semiarboreal forms." "So you do not have any problem with these forms being arboreal?" asked Martin. "No, I would agree, the arboreal hypothesis is far superior," responded Paul. Steve Gatesy raised a cautionary note regarding tracks and a reversed hallux by adding, "We are finding in the Triassic Greenland forms what we are calling a tetradactyl trackway, where we have shown that a 'reversed-hallux' trackway can actually be made by a form without a reversed hallux by plunging the foot into the substrate in a certain way that the toe is not really reversed anatomically. We must be careful about looking for perching feet in Triassic forms from trackways." Paul expanded further about theropod design by commenting on their shoulder architecture and by referring to a set of reconstructive drawings he provided for the participants. "There have been some misconceptions about the shoulder girdles of dinosaurs. Quadmpedal forms, of course, walked with forelimbs outstretched to the ground and the limbs under the body. In a lot of the theropods, for example Syntarsus and other Cretaceous forms, the shoulder glenoid faces laterally so that the humems can be brought out laterally. When I manipulate the humems in the shoulder of Syntarsus, I can extend the humems laterally and slightly dorsally as I have illustrated. The range of motion in these theropods is very similar to that of Archaeopteryx; there is very little difference. Not until later birds do we see the glenoid facing dorsally so that the wing can be brought higher up over the back. This ability to position the humems

340 SMITHSONIAN CONTRIBUTIONS TO PALEOBIOLOGY<br />

the <strong>Lo</strong>wer Cretaceous of China. Science, 255:845-848.<br />

Shubin, N.H.<br />

1994. The Phylogeny of Development and the Origin of Homology. In L.<br />

Grande and O. Rieppel, Interpreting the Hierarchy of Nature, pages<br />

201-225. New York: Academic Press.<br />

Smith, P.E., N.M. Evensen, D. York, S. Cumbaa, and D. Russell<br />

1996. 40 Ar- 39 Ar Laser-Probe Dating of the Yixian Formation, Northeast<br />

China and the Early Evolution of Birds. Journal of Vertebrate Paleontology,<br />

16(3):67A.<br />

Smith, P.E., N.M. Evensen, D. York, C. Mee-Mann, J. Fan, L. Jin-Ling, S.<br />

Cumbaa, and D. Russell<br />

1995. Dates and Rates in Ancient Lakes 40 Ar- 39 Ar Evidence for an Early<br />

Cretaceous Age for the Jehol Group, Northeast China. Canadian<br />

Journal of Earth Sciences, 32:1426-1431.<br />

Steadman, D.<br />

1983. Commentary on "The Origin and Early Radiation of Birds" (L.<br />

Martin). In A.H. Brush and G.A. Clark, Jr., editors, Perspectives in<br />

Ornithology, pages 338-344. Cambridge: Cambridge University<br />

Press.<br />

Varricchio, D.J., and L.M. Chiappe<br />

1995. A New Bird from the Cretaceous Two Medicine Formation of Montana.<br />

Journal of Vertebrate Paleontology, 15( 1 ):201 -204.<br />

Walker, CA.<br />

1981. New Subclass of Birds from the Cretaceous of South America. Nature,<br />

292:51-53.<br />

Wellnhofer, P.<br />

1994. New Data on the Origin and Early Evolution of Birds. Compte Rendus<br />

de I 'Academie des Sciences, Paris, 319(2):299-308.<br />

Zhou, Z.<br />

1995a. Is Mononykus a Bird? Auk, 112(4):958-963.<br />

1995b. The Discovery of Early Cretaceous Birds in China. In D. Stefan Peters,<br />

editor, Acta Palaeomithologica: 3 Symposium SAPE; 5 Internationale<br />

Senckenberg-Konferenze, 22-26 Juni 1992. Courier<br />

Forschungsinstitut Senckenberg, 181:9-22.

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!