トライアス紀末期のアーコサウルスのノナヴィア人の羽毛
T D Jones1, J A Ruben, L D Martin
1Department of Zoology, Oregon State University, Corvallis, OR 97331, USA. tdjones@sfasu.edu
Science (New York, N.Y.)
|June 24, 2000
まとめ
ロンジスクワマ・インギニス (Longisquama insignis) はトライアス紀後半のアーコサウルで,羽毛のような構造を持ち,鳥の羽毛と同型である可能性がある. これらの発見は,羽毛は,最も古い鳥よりも古いかもしれないことを示唆しています.
科学分野:
- パレオントロジー・パレオントロジー
- 進化生物学の進化生物学について
- 脊椎動物学 脊椎動物学
背景:
- ロンジスクワマ・インギニス (Longisquama insignis) は,中央アジアにおけるトライアシク後期から絶滅したアーコサウルスの種である.
- この恐竜は,背面に沿って独特のペアリングされた全身の付属体を持っていた.
研究 の 目的:
- ロンジスクワマの全身付属体の形状を分析するために.
- これらの構造と鳥羽の間の潜在的な同質性を決定する.
- 羽毛の進化的起源を調査するために.
主な方法:
- ロンジスクワマの付属体の比較解剖分析.
- 基礎領域の構造を調べ,現代の鳥羽の解剖学と比較した.
主要な成果:
- ロンジスクワマの付属体は,鳥の羽毛と,特に底部で,重要な解剖学的類似性を共有しています.
- 基礎構造は,鳥の羽根カラミのような発達過程 (形質変異) を示唆しています.
- ロンジスクワマの鳥に対する正確な系統遺伝的位置は不明である.
結論:
- ロンジスクワマの全身の付属体は,非鳥の羽と解釈されている.
- これらの構造は,鳥の羽とホモロゴスである可能性が高い.
- ホモログである場合,これらの羽は,知られている最も古い鳥であるアーカイオプテリクスの羽より前のものです.
関連する概念動画
01:23Phylogeny
Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon (singular). Taxa (plural) can span different levels of the evolutionary hierarchy. For instance, the group containing all birds is a taxon (comprising the class Aves), and the group of all species of daisies (the genus Bellis) is a taxon. Phylogenies can likewise include just one genus (i.e., depict species relationships) or span an entire...
01:38Limits to Natural Selection
Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly adapted organisms. Several factors constrain natural selection.For one, natural selection can only act upon existing genetic variation. Hypothetically, redtusks may enhance elephant survival by deterring ivory-seeking poachers. However, if there are no gene variants—or alleles—for redtusks, natural selection cannot increase the prevalence of...
02:55The Evidence for Evolution
Genetic variations accumulating within populations over generations give rise to biological evolution. Evolutionary changes can result in the formation of novel varieties and entire new species. These changes are responsible for the diverse forms of life inhabiting the planet. The evidence for evolution suggests that all living organisms descended from common ancestors.The collection of fossils within sedimentary rocks give a record of common ancestry and often depicts the history of evolution.
02:56The Fossil Record
The fossil record documents only a small fraction of all organisms that have ever inhabited Earth. Fossilization is a rare process, and most organisms never become fossils. Moreover, the fossil record only exhibits fossils that have been discovered. Nevertheless, sedimentary rock fossils of long-lived, abundant, hard-bodied organisms dominate the fossil record. These fossils offer valuable information, such as an organism's physical form, behavior, and age. Studying the fossil record helps...
01:54Convergent Evolution
Evolution shapes the features of organisms over time, ensuring that they are suited for the environments in which they live. Sometimes, selection pressure leads to the rise of similar but unrelated adaptations in organisms with no recent common ancestors, a process known as convergent evolution.The structures that arise from convergent evolution are called analogous structures. They are similar in function even if they are dissimilar in structure. Further, structures can be analogous while also...
01:27Diversity of Protists III
Rhizaria are a diverse group of unicellular protists characterized by their threadlike cytoplasmic extensions known as pseudopodia. These structures aid in both locomotion and feeding, giving Rhizaria an amoeboid appearance. Their amoeboid morphology once led to taxonomic confusion, but molecular phylogenetics has clarified their evolutionary placement and emphasized their shared use of pseudopodia despite divergent lineages.This clade comprises diverse lineages such as Chlorarachniophyta,...