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Epipubic
Epipubic bones are a pair of bones projecting forward from the pelvic bones of modern marsupials, monotremes and fossil mammals like multituberculates, and even basal eutherians (the ancestors of placental mammals, who lack them). They first occur in non-mammalian cynodonts such as tritylodontids, suggesting that they are a synapomorphy between them and Mammaliformes. They were first described as early as 1698, but to date, their function(s) remain unresolved. Epipubic bones are often called ''marsupial bones'' because they support the mother's pouch in modern marsupials ("''marsupium''" is Latin for "pouch"). Function Some writers have suggested that the epipubic bones are a part of a kinetic link stretching from the femur on one side, to the ribs on the opposite side. This linkage is formed by a series of muscles: Each epipubic bone is connected to the femur by the pectineus muscle, and to the ribs and vertebrae by the pyramidalis, rectus abdominis, and external and in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution Of Mammals
The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synapsid species that looked like mammals. The lineage leading to today's mammals split up in the Jurassic; synapsids from this period include '' Dryolestes'', more closely related to extant placentals and marsupials than to monotremes, as well as '' Ambondro'', more closely related to monotremes. Later on, the eutherian and metatherian lineages separated; the metatherians are the animals more closely related to the marsupials, while the eutherians are those more closely related to the placentals. Since '' Juramaia'', the earliest known eutherian, lived 160 million years ago in the Jurassic, this divergence must have occurred in the same period. After the Cretaceous–Paleogene extinction event wiped out the non-avian dinosaurs (birds being the only surviving dinosaurs ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proximodorsal Process
The proximodorsal process is a feature of the skeleton of archosaurs. It may be a pair of tabs or blade - shaped flanges on the pelvis, and serves as an anchor point for the attachment of leg muscles. This process is of particular importance in the anatomy and comparative morphology of Mesozoic birds and advanced maniraptoran dinosaurs. The pelvis is made up of three paired bones and a sacrum. The three paired bones are called the ilium, the ischium, and the pubis. On the ischium there may be an obturator process and/or a proximodorsal process. The more primitive condition is for there to be no proximodorsal process, but a large obturator process. In primitive birds the ischia are complex, usually with a small or even absent obturator process and a large, rectangular, proximodorsal process extending up toward the ilium. This is the condition in ''Archaeopteryx'', Confuciusornis, and enantiornithines. Witmer, Lawrence M. (2002) "The Debate on Avian Ancestry: Phylogeny, Functio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eutheria
Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic traits of the feet, ankles, jaws and teeth. All extant eutherians lack epipubic bones, which are present in all other living mammals (marsupials and monotremes). This allows for expansion of the abdomen during pregnancy. The oldest-known eutherian species is ''Juramaia sinensis'', dated at from the early Late Jurassic ( Oxfordian) of China. Eutheria was named in 1872 by Theodore Gill; in 1880 Thomas Henry Huxley defined it to encompass a more broadly defined group than Placentalia. Characteristics Distinguishing features are: *an enlarged malleolus ("little hammer") at the bottom of the tibia, the larger of the two shin bones *the joint between the first metatarsal bone and the entocuneiform bone (the innermost of the three cuneiform ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammaliformes
Mammaliaformes ("mammalian forms") is a clade that contains the crown group mammals and their closest extinct relatives; the group radiated from earlier probainognathian cynodonts. It is defined as the clade originating from the most recent common ancestor of Morganucodonta and the crown group mammals; the latter is the clade originating with the most recent common ancestor of extant Monotremata, Marsupialia, and Placentalia. Besides Morganucodonta and the crown group mammals, Mammaliaformes includes Docodonta and '' Hadrocodium'' as well as the Triassic '' Tikitherium'', the earliest known member of the group. Mammaliaformes is a term of phylogenetic nomenclature. In contrast, the assignment of organisms to Mammalia has traditionally been founded on traits and, on this basis, Mammalia is slightly more inclusive than Mammaliaformes. In particular, trait-based taxonomy generally includes '' Adelobasileus'' and ''Sinoconodon'' in Mammalia, though they fall outside the Ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Macropus Major Hind Legs
''Macropus'' is a marsupial genus in the family Macropodidae. It has two extant species of large terrestrial kangaroos. The term is derived from the Ancient Greek μάκρος, ''makros'' "long" and πους, ''pous'' "foot". Thirteen known extinct species are recognised. The type species is the eastern grey kangaroo. Taxonomy In 2019, a reassessment of macropod taxonomy determined that ''Osphranter'' and '' Notamacropus'', formerly considered subgenera, should be moved to the genus level. This change was accepted by the Australian Faunal Directory in 2020. Extant Species Fossils A currently-unnamed Pleistocene ''Macropus'' species from Australia was the largest kangaroo ever, with an estimated mass of around 274 kg (~604 lb). * †''Macropus dryas'' * †''Macropus gouldi'' * †''Macropus narada'' * †''Macropus piltonensis'' * †''Macropus rama'' * †''Macropus woodsi'' * †''Macropus pavana'' * †''Macropus thor'' * †''Macropus ferragus'' * †''Macropus m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Erythrotherium
''Erythrotherium'' (meaning "red beast") is an extinct genus of basal mammaliaforms from the Late Triassic to Lower Jurassic. It is related to ''Morganucodon''. Only one species is recorded, ''Erythrotherium parringtoni'', from Red Beds, Stormberg Group, Mafeteng, Upper Elliot and Clarens Formations, from Lesotho and South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun .... The single jaw of ''Erythrotherium'' was found in the matrix surrounding a dinosaur fossil, by the person preparing the dinosaur, Mr C. Gow. References Morganucodonts Triassic synapsids of Africa Jurassic synapsids of Africa Triassic South Africa Jurassic South Africa Fossils of South Africa Fossil taxa described in 1964 Taxa named by Alfred W. Crompton Prehistoric cynodont genera {{P ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Obturator Process
The obturator process is an anatomical feature on the pelvis of archosaurs. It is a raised area of the ischium bone of the pelvis.Romer, Alfred S. (1923) "The Pelvic Musculature of Saurischian Dinosaurs" "Bulletin of the American Museum of Natural History" Vol. XLVIII 48:605-617 It is the origin of muscles that attach to the femur and aid in running. These muscles are called M. pubo-ischio-femoralis externus 1 and 2 in crocodylians. In birds the muscles are called the M. obturatorius lateralis and M. obturatorius medialis. They insert on the greater trochanter of the femur.Hutchinson, John R.(2001) "The evolution of femoral osteology and soft tissues on the line to extant birds (Neornithes)" "Zoological Journal of the Linnean Society" 131:169-197 See proximodorsal process The proximodorsal process is a feature of the skeleton of archosaurs. It may be a pair of tabs or blade - shaped flanges on the pelvis, and serves as an anchor point for the attachment of leg muscles. This proce ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Baculum
The baculum (also penis bone, penile bone, or ''os penis'', ''os genitale'' or ''os priapi'') is a bone found in the penis of many placental mammals. It is absent from the human penis, but present in the penises of some primates, such as the gorilla and chimpanzee. The os penis arises from primordial cells within soft tissues of the penis, and its formation is largely under the influence of androgens. The bone is located above the male urethra, and it aids sexual reproduction by maintaining sufficient stiffness during sexual penetration. The homologue to the baculum in female mammals is known as the baubellum or '' os clitoridis'' (also ''os clitoris''), a bone in the clitoris. Etymology The word ''baculum'' meant "stick" or "staff" in Latin and originated from el, βάκλον, ''baklon'' "stick". Function The baculum is used for copulation and varies in size and shape by species. Its evolution may be influenced by sexual selection, and its characteristics are sometim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kayentatherium
''Kayentatherium'' is an extinct genus of tritylodontid cynodonts that lived during the Early Jurassic. It is one of two tritylodonts from the Kayenta Formation of northern Arizona, United States. ''Kayentatherium'' means "Kayenta Beast", and is named for the geological formation in which it was found, the Kayenta Formation. ''Kayentatherium'' is known from several specimens.Kermack, D. 1982. A new tritylodont from the Kayenta Formation of Arizona. Zoological Journal of the Linnean Society, 76. 1-17.Sues, Hans-Dieter & F. A. Jenkins. 2006. The Postcranial Skeleton of Kayentatherium Wellesi from the Lower Jurassic Kayenta Formation of Arizona and the Phylogenetic Significance of Postcranial Features in Tritylodontid Cynodonts in: Carrano, Matthew T., Gaudin, T. J., Blob, R. W. and Wible, J. R., Amniote Paleobiology: Perspectives on the Evolution of Mammals, Birds, and Reptiles: The University of Chicago Press. pp. 114-152. The specific name honors paleontologist Samuel Welles, who ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate maternal and fetal circulations, and is an important endocrine organ, producing hormones that regulate both maternal and fetal physiology during pregnancy. The placenta connects to the fetus via the umbilical cord, and on the opposite aspect to the maternal uterus in a species-dependent manner. In humans, a thin layer of maternal decidual ( endometrial) tissue comes away with the placenta when it is expelled from the uterus following birth (sometimes incorrectly referred to as the 'maternal part' of the placenta). Placentas are a defining characteristic of placental mammals, but are also found in marsupials and some non-mammals with varying levels of development. Mammalian placentas probably first evolved about 150 million to 200 millio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Flexion
Motion, the process of movement, is described using specific anatomical terms. Motion includes movement of organs, joints, limbs, and specific sections of the body. The terminology used describes this motion according to its direction relative to the anatomical position of the body parts involved. Anatomists and others use a unified set of terms to describe most of the movements, although other, more specialized terms are necessary for describing unique movements such as those of the hands, feet, and eyes. In general, motion is classified according to the anatomical plane it occurs in. ''Flexion'' and ''extension'' are examples of ''angular'' motions, in which two axes of a joint are brought closer together or moved further apart. ''Rotational'' motion may occur at other joints, for example the shoulder, and are described as ''internal'' or ''external''. Other terms, such as ''elevation'' and ''depression'', describe movement above or below the horizontal plane. Many anatomic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Respiration (physiology)
In physiology, respiration is the movement of oxygen from the outside environment to the cells within tissues, and the removal of carbon dioxide in the opposite direction that's to the environment. The physiological definition of respiration differs from the biochemical definition, which refers to a metabolic process by which an organism obtains energy (in the form of ATP and NADPH) by oxidizing nutrients and releasing waste products. Although physiologic respiration is necessary to sustain cellular respiration and thus life in animals, the processes are distinct: cellular respiration takes place in individual cells of the organism, while physiologic respiration concerns the diffusion and transport of metabolites between the organism and the external environment. Gas exchanges in the lung occurs by ventilation and perfusion. Ventilation refers to the in and out movement of air of the lungs and perfusion is the circulation of blood in the pulmonary capillaries. In mammals, physi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
