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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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Las perillas de plumas en el dinosaurio Velociraptor.
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
Resumen
Se conocen dinosaurios emplumados, como el Velociraptor mongoliensis, pero la evidencia en especies más grandes es escasa. Nuevos hallazgos revelan perillas de plumas en los antebrazos de Velociraptor, lo que confirma las plumas en este dinosaurio terópodo más grande y no volador.
Área de la Ciencia:
- Paleontología Paleontología.
- Biología evolutiva Biología evolutiva.
- Paleobiología de dinosaurios Paleobiología de dinosaurios.
Sus antecedentes:
- Se conocen dinosaurios terópodos no aviares emplumados, pero la evidencia fósil está sesgada hacia las especies de cuerpo pequeño preservadas en lugares fósiles específicos.
- La comprensión de la distribución de las plumas en los dinosaurios terópodos más grandes es limitada debido a sesgos de preservación.
Objetivo del estudio:
- Para proporcionar evidencia directa de la presencia de plumas en el dinosaurio terópodo de cuerpo más grande, derivado y no volador Velociraptor mongoliensis.
- Ampliar el conocimiento sobre la distribución y evolución de las plumas dentro de los clados de terópodos no aviares.
Principales métodos:
- Examen del antebrazo posterior de ejemplares de Velociraptor mongoliensis.
- Identificación de las perillas de las plumas, que son indicativas de grandes puntos de fijación de plumas.
Principales resultados:
- Se encontró evidencia directa de plumas en el Velociraptor mongoliensis.
- Se identificaron perillas de pluma en el antebrazo posterior, lo que indica la presencia de plumas secundarias.
Conclusiones:
- Este descubrimiento confirma la presencia de plumas en un miembro más grande y no volador de un clado de terópodos.
- Los hallazgos contribuyen significativamente a la comprensión de la evolución y distribución de las plumas en los dinosaurios no aviares con teropruro.