相关概念视频
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...
01:12Carbon Skeletons
Life on Earth is carbon-based, as all macromolecules that make up living organisms contain carbon atoms. All organic compounds have a carbon backbone. Each carbon atom is tetravalent and can bond with four other atoms, making it an extraordinarily flexible component of biological molecules. Because carbon’s valence electrons are stable, it rarely becomes an ion. As the carbon chain increases in length, structural modifications such as ring structures, double bonds, and branching side chains...
01:26Bone Markings
Bones have various surface features that help form joints and attach to other soft tissues. Depending on the function, bone markings are categorized into articulating projections, processes for attachment, depressions, and openings.
Articulating Projections
Articulating projections are found where two bones meet to form a joint. These structures are usually found at the ends of bones. The largest articulation is a rounded projection called the head, supported by a narrow neck at the ends of...
Articulating Projections
Articulating projections are found where two bones meet to form a joint. These structures are usually found at the ends of bones. The largest articulation is a rounded projection called the head, supported by a narrow neck at the ends of...
01:21Tooth Anatomy
The human tooth enables us to eat a variety of foods, speak clearly, and even aid in shaping our faces. Teeth are composed of various elements that work together. Here's a detailed look at the anatomy of a human tooth.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
The Crown, Neck, and Root
The visible part of the tooth is referred to as the crown. It's covered by enamel, the hardest substance in the human body. The crown is uniquely shaped for each type of tooth, allowing for different functions such as cutting, tearing, or grinding food.
01:12The Hyoid Bone
The hyoid bone is a small U-shaped bone located in the upper neck at the level of the inferior mandible, with its tips pointing posteriorly. It does not directly articulate with any other bone in the body. The hyoid acts as the attachment site for the tongue, the larynx, and the pharynx. It is held in position by a series of small muscles attached from above or below. These muscles help to move the hyoid up/down or forward/back in coordination with movements of the tongue, larynx, and pharynx...
01:19Bones of the Upper Limb: Humerus
The upper limb consists of the arm, forearm, wrist, and hand bones. The humerus is the single bone of the upper arm region. Proximally, it has a large, spherical, smooth head that articulates with the glenoid cavity of the scapula to form the glenohumeral or shoulder joint. The margin of the head is the anatomical neck, a residual epiphyseal plate. Laterally it extends to form bony projections called the greater tubercle and the lesser tubercle. Next to the tubercles is the surgical neck, a...
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Paleotribological models using preserved fossil tissue properties reveal functional significance of Eurasian mammoth dental evolution.
Acta biomaterialia·2026
在恐龙Velociraptor的羽毛羽毛旋.
Alan H Turner1, Peter J Makovicky, Mark A Norell
1Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192, USA. turner@amnh.org
Science (New York, N.Y.)
|September 22, 2007
概括
已知有羽毛的恐龙,如Velociraptor mongoliensis,但较大的物种的证据很少. 新的发现揭示了Velociraptor前臂上的羽毛旋,证实了这种更大,无法飞行的热足类恐龙的羽毛.
科学领域:
- 古生物学的古生物学
- 进化生物学 进化生物学
- 恐龙古生物学 恐龙古生物学
背景情况:
- 已知有羽毛的非鸟类类类恐龙,但化石证据倾向于在特定的化石 lagerstätten 保存的小体物种.
- 由于保护偏见,对较大的热足类恐龙的羽毛分布的理解是有限的.
研究的目的:
- 为了提供羽毛存在的直接证据,在更大的体型,衍生和无法飞行的热足类恐龙Velociraptormongoliensis.
- 扩大关于非鸟类类类类的羽毛分布和进化方面的知识.
主要方法:
- 对Velociraptor mongoliensis标本后侧前臂的检查.
- 羽毛旋的识别,这表明羽毛的固定点很大.
主要成果:
- 在Velociraptor mongoliensis中发现了羽毛的直接证据.
- 在前臂后部发现了羽毛旋,表明存在二次羽毛.
结论:
- 这一发现证实了在一个更大,不能飞行的类成员中存在羽毛.
- 这些发现对了解非鸟类恐龙的羽毛进化和分布作出了重大贡献.
