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A tetrapod is a form of wave-dissipating concrete block used to prevent erosion caused by weather and longshore drift, primarily to enforce coastal structures such as seawalls and breakwaters. Tetrapods are made of concrete , and use a tetrahedral shape to dissipate the force of incoming waves by allowing water to flow around rather than ...
However, most tetrapod species today are amniotes, most of which are terrestrial tetrapods whose branch evolved from earlier tetrapods early in the Late Carboniferous. The key innovation in amniotes over amphibians is the amnion , which enables the eggs to retain their aqueous contents on land, rather than needing to stay in water.
Marine tetrapods are tetrapods that returned from land back to the sea again. The first returns to the ocean may have occurred as early as the Carboniferous Period [ 20 ] whereas other returns occurred as recently as the Cenozoic , as in cetaceans, pinnipeds , [ 21 ] and several modern amphibians .
Several groups of tetrapods have undergone secondary aquatic adaptation, an evolutionary transition from being purely terrestrial to living at least part of the time in water. These animals are called "secondarily aquatic" because although their ancestors lived on land for hundreds of millions of years, they all originally descended from ...
The water-based lateral line system was used substantially by these aquatic tetrapods to detect danger from predators. [2] Within the Osteichthyan diversification, there were no changes related to respiration in the transition as can be seen by the nasal region and palatal morphology in elpistostegalid fishes.
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
Bathymetric surveys and charts are associated with the science of oceanography, particularly marine geology, and underwater engineering or other specialized purposes. Bathymetric map of Medicine Lake, California. Bathymetric data used to produce charts can also be converted to bathymetric profiles which are vertical sections through a feature.
Tetrapodomorpha (also known as Choanata [3]) is a clade of vertebrates consisting of tetrapods (four-limbed vertebrates) and their closest sarcopterygian relatives that are more closely related to living tetrapods than to living lungfish.