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Placoderms (from Greek πλάξ (plax, plakos) 'plate' and δέρμα (derma) 'skin') [1] are vertebrate animals of the class Placodermi, an extinct group of ...
Arthrodira (Greek for "jointed neck") is an order of extinct armored, jawed fishes of the class Placodermi that flourished in the Devonian period before their sudden extinction, surviving for about 50 million years and penetrating most marine ecological niches. Arthrodires were the largest and most diverse of all groups of placoderms. [1]
On account of their radically reduced armor, some paleontologists have suggested that the Ptyctodontida were not actually placoderms, but actual holocephalians, some primitive group of elasmobranch fish, or even were the ancestors of the holocephalians, including the chimaeras. Thorough anatomical examinations of whole fossil specimens reveal ...
Sociology is the scientific study of human society that focuses on society, human social behavior, patterns of social relationships, social interaction, ...
Pterichthyodes is a genus of antiarch placoderm fishes from the Devonian period. Its fossils have been discovered in Scotland. [1] They were one of the first species recognized for what they were, as their fossils are common in the Old Red Sandstone formation studied by geologists in the early 19th century.
The fossil findings of primitive bony fishes such as Guiyu oneiros and Psarolepis, which lived contemporaneously with Entelognathus and had pelvic girdles more in common with placoderms than with other bony fish, show that it was a relative rather than a direct ancestor of the extant gnathostomes. [13]
In sociology, a social system is the patterned network of relationships constituting a coherent whole that exist between individuals, groups, and institutions. [1] It is the formal structure of role and status that can form in a small, stable group. [1]
Social interface is a concept from social science (particularly, media ecology (Marshall McLuhan) and sociology of technology). It can be approached from a theoretical or a practical perspective. As a concept of social interface theory, social interface is defined by Norman Long (1989, 2001). In 2001 his revised definition was: