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The event is well-documented [1] and important [2] [3] academically as a demonstration of transitional forms and exaptation, the re-purposing of existing structures during evolution. [ 4 ] The ossicles evolved from skull bones present in most tetrapods , including amphibians , sauropsids (which include extant reptiles and birds ) and early ...
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.
Seymouria is an extinct genus of seymouriamorph from the Early Permian of North America and Europe. [1] Although they were amphibians (in a biological sense), Seymouria were well-adapted to life on land, with many reptilian features—so many, in fact, that Seymouria was first thought to be a primitive reptile.
The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus) [41] but this is a great deal smaller than the largest amphibian that ever existed—the extinct 9 m (30 ft) Prionosuchus, a crocodile-like temnospondyl dating to 270 million years ago from the middle Permian of Brazil. [42]
Most scientists have concluded that all of the primary groups of modern amphibians—frogs, salamanders and caecilians—are closely related. Some writers have argued that the early Permian dissorophoid Gerobatrachus hottoni is a lissamphibian. [ 2 ]
While most labyrinthodonts remained aquatic or semi-aquatic, some of the reptile-like amphibians adapted to explore the terrestrial ecological niches as small or medium-sized predators. They evolved increasingly terrestrial adaptions during the Carboniferous, including stronger vertebrae and slender limbs, and a deeper skull with laterally ...
Amphibians are in decline worldwide, with 2 out of every 5 species threatened by extinction, according to a paper published Wednesday in the scientific journal Nature. More than 2,000 species of ...
Gastrulation in frogs commences in the marginal zone— the region encircling the blastula's equator where the animal and vegetal hemispheres meet—differing from sea urchins where it begins in the most vegetal part. In contrast to the vegetal blastomeres, the endodermal cells in the marginal zone of frogs are smaller and contain less yolk. [2]