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The coccyx, or tailbone, is the remnant of a lost tail. [19] All mammals have a tail at some point in their development; in humans, it is present for a period of 4 weeks, during stages 14 to 22 of human embryogenesis. [20] This tail is most prominent in human embryos 31–35 days old. [21]
Atavism. Reappearance of a genetic trait once thought extinct. Early embryos of various species display some ancestral features, like the tail on this human embryo. These features normally disappear in later development, but it may not happen if the animal has an atavism. [1][2] In biology, an atavism is a modification of a biological structure ...
The tail is the elongated section at the rear end of a bilaterian animal 's body; in general, the term refers to a distinct, flexible appendage extending backwards from the midline of the torso. In vertebrate animals that evolved to lose their tails (e.g. frogs and hominid primates), the coccyx is the homologous vestigial of the tail.
Specialty. Medical genetics. Polymelia is a birth defect in which an affected individual has more than the usual number of limbs. It is a type of dysmelia. In humans and most land-dwelling vertebrates, this means having five or more limbs. The extra limb is most commonly shrunken and/or deformed. The term is from Greek πολυ- "many ...
While most breeds are born with tails, there are some that are born with very short tails or no tail at all. "Most dogs have tails, however there are a small number of breeds that are born without ...
I) all bones of thigh and lower leg present. II) fused fibula. III) fibula absent. IV) partially fused femur, fused fibula. V) partially fused femur. VI) fused femur, fused tibia. VII) fused femur, tibia absent. Sirenomelia is classified by the skeletal structure of the lower limb, ranging from class I, where all bones are present and only the ...
Tail wagging has long been associated with a pup's mood, but the fascinating -- and often telling -- things about the appendage don't stop there. Here are 10 things you didn't know about dogs' tails.
Small Potatoes (. The X-Files. ) A baby born with a tail. This effect was added in post-production with CGI technology. " Small Potatoes " is the twentieth episode of the fourth season of the American science fiction television series The X-Files. It premiered on the Fox network in the United States appropriately on April 20, 1997 (4/20, also ...