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Amphibians have soft bodies with thin skins, and lack claws, defensive armour, or spines. Nevertheless, they have evolved various defence mechanisms to keep themselves alive. The first line of defence in salamanders and frogs is the mucous secretion that they produce. This keeps their skin moist and makes them slippery and difficult to grip.
Sea urchin tube feet extended past the spines.. Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, such as the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on brittle stars, and have only a feeding function in feather stars.
Scientists found that members of the new species are smaller than their offshore common bottlenose counterparts, eat different fish and have spines adapted to navigating the tight spaces of rivers ...
They have a rigid, usually spherical body bearing moveable spines, which give the class the name Echinoidea (from the Greek ἐχῖνος ekhinos 'spine'). [5] The name urchin is an old word for hedgehog , which sea urchins resemble; they have archaically been called sea hedgehogs .
Jawless fish are limbless but may have preceded the evolution of vertebrate limbs, whereas numerous reptile and amphibian lineages – and some eels and eel-like fish – independently lost their limbs. Larval amphibians, tadpoles, are also often limbless. No mammals or birds are limbless, but some feature partial limb-loss or limb reduction.
All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this.
The use of the sail for thermoregulation, sexual dimorphism, and species identification are all hypotheses that have been applied to other sail-bearing taxa. [9] A speculation more specifically related to Platyhystrix is that these neural spines could have served to stiffen the vertebral column in order to adapt to a more terrestrial lifestyle ...
Temnospondyli (from Greek τέμνειν, temnein 'to cut' and σπόνδυλος, spondylos 'vertebra') or temnospondyls is a diverse ancient order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carboniferous, Permian and Triassic periods, with fossils being found on every continent.