| Secondarily flightless birds or Cretaceous non-avian theropods? | |
| | |
MedLine Citation:
|
PMID: 19800747 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
|
Recent studies by Varricchio et al. reveal that males cared for the eggs of troodontids and oviraptorids, so-called "non-avian theropods" of the Cretaceous, just as do those of most Paleognathic birds (ratites and tinamous) today. Further, the clutches of both groups have large relative volumes, and consist of many eggs of relatively large size. By comparison, clutch care by most extant birds is biparental and the clutches are of small relative volume, and consist of but few small eggs. Varricchio et al. propose that troodontids and oviraptorids were pre-avian and that paternal egg care preceded the origin of birds. On the contrary, unmentioned by them is that abundant paleontological evidence has led several workers to conclude that troodontids and oviraptorids were secondary flightless birds. This evidence ranges from bird-like bodies and bone designs, adapted for climbing, perching, gliding, and ultimately flight, to relatively large, highly developed brains, poor sense of smell, and their feeding habits. Because ratites also are secondarily flightless and tinamous are reluctant, clumsy fliers, the new evidence strengthens the view that troodontids and oviraptorids were secondarily flightless. Although secondary flightlessness apparently favors paternal care of clutches of large, abundant eggs, such care is not likely to have been primitive. There are a suite of previously unknown independent findings that point to the evolution of, first, maternal, followed by biparental egg care in earliest ancestors of birds. This follows from the discovery of remarkable relict avian reproductive behaviors preserved by virtue of the highly conservative nature of vertebrate brain evolution. These behaviors can be elicited readily by exposing breeding birds to appropriate conditions, both environmental and with respect to their eggs and chicks. They give significant new clues for a coherent theory of avian origin and early evolution. |
| | |
Authors:
|
J Lee Kavanau |
Related Documents
:
|
17217007 - The ecological characteristics of anopheles mosquitoes associated with low malaria tran... 21846407 - The time burden of overweight and obesity in primary care. 11761057 - Down the tube: pollinators, predators, and the evolution of flower shape in the alpine ... 9989867 - Intracytoplasmic sperm injection in the treatment of male subfertility. 7979787 - The role of outcomes data in health care reform. 22510517 - Gender differences in care home admission risk: partner's age explains the higher risk ... |
Publication Detail:
|
Type: Journal Article Date: 2009-10-02 |
Journal Detail:
|
Title: Medical hypotheses Volume: 74 ISSN: 1532-2777 ISO Abbreviation: Med. Hypotheses Publication Date: 2010 Feb |
Date Detail:
|
Created Date: 2010-02-01 Completed Date: 2010-04-15 Revised Date: - |
Medline Journal Info:
|
Nlm Unique ID: 7505668 Medline TA: Med Hypotheses Country: United States |
Other Details:
|
Languages: eng Pagination: 275-6 Citation Subset: IM |
Affiliation:
|
Department of Ecology and Evolutionary Biology, University of California, Los Angeles, CA 90095-1606, USA. lkavanau@biology.ucla.edu |
Export Citation:
|
APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
|
Animals Birds / genetics* Evolution* Flight, Animal / physiology* Models, Genetic* |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
Previous Document: Breathing strategy to preserve exercising cardiac function in patients with heart failure.
Next Document: Benefits of donor human milk for preterm infants: Current evidence.