Amphibia shut in4/18/2023 ![]() ![]() The vertebrae were complex and not particularly strong, consisting of numerous, often poorly ossified elements. The skull had prominent otic notches behind each eye and a parietal eye. The sole exception were the chisel-like teeth of some of the advanced herbivorous diadectomorphs. The teeth were replaced in waves that traveled from the front of the jaw to the back in such a way that every other tooth was mature, and the ones in between were young. Their jaws were lined with small, sharp, conical teeth and the roof of the mouth bore larger tusk-like teeth. The broad head and short neck may have been a result of respiratory constraints. With the exception of the snake-like aïstopods, the skulls of labyrinthodonts were massive. Reconstruction of Branchiosaurus, a temnospondyl tadpole or paedomorph form with external gills ![]() The relative development and shape of the elements is highly variable. Complex vertebrae made of multiple components: an intercentrum (wedge-shaped front lower piece), two pleurocentra (upper rear piece), and a vertebral arch/spine (upper projection).In later terrestrial forms such as Seymouria, it may possibly have held a tympanic membrane (eardrum). In earlier fully aquatic forms such as Ichthyostega, it may have formed an open spiracle. Otic notch behind each eye at the back edge of the skull.With the exception of the later more reptile-like forms, the skull was rather flat and strongly ornamented with presumably tough dermal covering, accounting for an older term for the group: "Stegocephalia". Massive skull roof, with openings only for the nostrils, eyes and a parietal eye, similar to the structure of the " anapsid" reptiles.The cross section resembles a classical labyrinth (or maze), hence the name of the group. Strongly folded tooth surface, involving infolding of the dentin and enamel of the teeth.Particularly the early forms exhibited a lot of variation, yet there are still a few basic anatomical traits that make their fossils very distinct and easily recognizable in the field: The labyrinthodonts flourished for more than 200 million years. Many authors prefer to simply use the term tetrapod, while others have re-defined the previously obsolete term Stegocephalia ("roof heads") as a cladistic alternative to "Labyrinthodontia" or "Tetrapoda". However, some have continued to use the group in their classifications, at least informally, pending more detailed study of their relationships. "Labyrinthodonts" generally have complex multi-part vertebrae, and several classification schemes have utilized vertebrae to define subgroups.īecause labyrinthodonts do not form a monophyletic group, many modern researchers have abandoned the term. They are also distinguished by a broad, strongly-built skull roof composed of many small heavily-textured skull bones. The name describes the pattern of infolding of the dentin and enamel of the teeth, which are often the only part of the creatures that fossilize. "Labyrinthodont" generally refers to extinct four-limbed tetrapods with a large body size and a crocodile-like lifestyle. "Labyrinthodont"-grade vertebrates evolved from lobe-finned fishes in the Devonian, though a formal boundary between fish and amphibian is difficult to define at this point in time. Instead, they consistute an evolutionary grade (a paraphyletic group), ancestral to living tetrapods such as lissamphibians (modern amphibians) and amniotes ( reptiles, mammals, and kin). Traditionally considered a subclass of the class Amphibia, modern classification systems recognize that labyrinthodonts are not a formal natural group ( clade) exclusive of other tetrapods. "Labyrinthodontia" ( Greek, 'maze-toothed') is an informal grouping of extinct predatory amphibians which were major components of ecosystems in the late Paleozoic and early Mesozoic eras (about 390 to 150 million years ago). Subclass Lissamphibia (modern amphibians).Subclass Lepospondyli † (possible ancestors of modern amphibians).Order Reptiliomorpha * (ancestors of amniotes)Ĭladistically included but traditionally excluded taxa.Order Temnospondyli † (possible ancestors of modern amphibians).Artist's conception of a Proterogyrinus, an anthracosaur ![]()
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