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  2. Placoderm - Wikipedia

    en.wikipedia.org/wiki/Placoderm

    Placoderms (from Greek πλάξ (plax, plakos) 'plate' and δέρμα (derma) 'skin') [1] are vertebrate animals of the class Placodermi, an extinct group of ...

  3. Arthrodira - Wikipedia

    en.wikipedia.org/wiki/Arthrodira

    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]

  4. Ptyctodontida - Wikipedia

    en.wikipedia.org/wiki/Ptyctodontida

    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 ...

  5. Sociology - Wikipedia

    en.wikipedia.org/wiki/Sociology

    Sociology is the scientific study of human society that focuses on society, human social behavior, patterns of social relationships, social interaction, ...

  6. Pterichthyodes - Wikipedia

    en.wikipedia.org/wiki/Pterichthyodes

    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.

  7. Gnathostomata - Wikipedia

    en.wikipedia.org/wiki/Gnathostomata

    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]

  8. Social system - Wikipedia

    en.wikipedia.org/wiki/Social_system

    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]

  9. Social interface - Wikipedia

    en.wikipedia.org/wiki/Social_interface

    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: