Definition of synapsid in English:



  • A fossil reptile of a Permian and Triassic group, the members of which show increasingly mammalian characteristics and include the ancestors of mammals.

    Subclass Synapsida; includes the pelycosaurs and the therapsids

    • ‘Indeed, most workers recognized a geographical and temporal gap between Permo-Carboniferous ‘pelycosaurs’ and therapsid synapsids.’
    • ‘The hypothesis that disparate groups of synapsids independently acquired mammallike characteristics has a long pedigree.’
    • ‘In the dry late Permian environment many types of synapsids and reptiles flourished.’
    • ‘The amniotes in turn have two main groups: the synapsids (including mammals) and the sauropsids (including reptiles and their fossil relatives).’
    • ‘The early tetrapods of this time were amphibian-like animals that eventually gave rise to the reptiles and synapsids by the end of the Paleozoic.’
    • ‘The earliest occurring and phylogenetically most primitive synapsids are the ‘pelycosaurs’ of traditional terminology.’
    • ‘It has therefore been suggested that the mammalian class II gene clusters arose after the separation of the synapsids and the therapsids.’
    • ‘In reptiles and primitive synapsids, the right and left lower jaws are each made up of a number of bones, one of which is the dentary, or tooth-bearing, bone.’
    • ‘Tall neural spines are also a characteristic of early synapsids.’
    • ‘The second major group of reptiles, the synapsids, have only a single temporal opening.’
    • ‘Dimetrodon is neither a reptile nor a mammal, but a basal synapsid - that is, an early relative of the ancestors of mammals.’
    • ‘As Rowe points out, the early cynodonts were the first synapsids in which the brain filled the endocranial cavity.’
    • ‘Paleozoic synapsids have been the focus of many large-scale treatments over the past century and their anatomy and interrelationships are well known.’
    • ‘This is an example of convergent evolution; synapsids and archosaurs evolved these features independently.’
    • ‘Conversely, if the fossil record does not accurately portray the first appearances of synapsids because preservation rates vary widely, then phylogenetic measures might yield a more reliable sequence of branching events.’
    • ‘These creatures succeeded the pelycosaurian synapsids as the rulers of the land, until they in turn were supplanted by the archosaurs during the early Triassic.’
    • ‘Land amniotes continued to diversify, and by the middle Pennsylvanian had split into several taxa, two of which would go on to dominate the Mesozoic and Cenozoic: the diapsids and the synapsids.’
    • ‘Assuming (likely, but not certain) that turtles diverged from Eureptilia after synapsids, there remains the problem of whether turtles have turbinals.’
    • ‘The possible parallel evolution of a jaw joint that allows extensive sliding in anomodonts is not unprecedented, because other synapsids independently evolved similar features.’
    • ‘The temporal openings at the back of the skull that are shared by all synapsids were greatly enlarged, so that the remaining bone formed long arches.’


Early 20th century from modern Latin Synapsida, from Greek sun- ‘together’ + apsis, apsid- ‘arch’.



/sʌɪˈnapsɪd/ /sɪˈnapsɪd/