Paraphyletic
In biological taxonomy, a grouping of organisms is said to be paraphyletic if all the members of the group have a common ancestor but the group doesn't include all the descendants of the common ancestor. Groups which include all the descendants of a common ancestor are commonly termed monophyletic, although this term is sometimes taken to apply to paraphyletic groups, in which case they are called holophyletic.Many of the older classifications contain paraphyletic groups, especially the traditional 2-6 kingdom systems and the classic division of the vertebrates. For example, the class Reptilia as traditionally defined is paraphyletic because that class doesn't include one group of its descendants, birds (in class Aves). Paraphyletic groups are often erected on the basis of plesiomorphies (ancestral similarities) instead of upon apomorphies (derived similarities).
In most cladistics-based schools of taxonomy, the existence of paraphyletic groups in a classification are regarded as errors. Some groups in currently accepted taxonomies may later turn out to be paraphyletic, in which case the classifications may be revised to eliminate them. Some, however, feel that having paraphyletic groups is an acceptable sacrifice if it makes the taxonomy more understandable. Others argue that paraphyletic groups are necessary to have a comprehensive classification including extinct groups, since each species, genus, and so forth necessarily originates from part of another.
found the hat.html">hat of the unfortunate Ichabod, and close beside it a
not to be discovered. Hans Van Ripper as executor of his estate,
consisted of two shirts and a half; two stocks for the neck; a
clothes; a rusty razor; a book.html">book of psalm tunes full of dog's-ears;
schoolhouse, they belonged to the community, excepting Cotton
a book of dreams and fortune-telling; in which last was a sheet of
to make a copy of verses in honor of the heiress of Van Tassel.
to the flames by Hans Van Ripper; who, from that time forward,
he never knew any good come of this same reading and writing.
his quarter's pay but a day or two before, he must have had about
on the following Sunday. Knots of gazers and gossips were
the hat and pumpkin.html">pumpkin had been found. The stories of Brouwer, of
they had diligently considered them all, and compared them with
came to the conclusion that Ichabod had been carried off by the
nobody troubled his head any more about him; the school was
pedagogue reigned in his stead.
It is true, an old farmer, who had been down to New York on
ghostly adventure was received, brought home the intelligence
neighborhood partly through fear of the goblin and Hans Van
dismissed by the heiress; that he had changed his quarters to a
the same time; had been admitted to the bar; turned politician;
made a justice of the Ten Pound Court. Brom Bones, too, who,
Katrina in triumph to the altar, was observed to look exceedingly
burst into a hearty laugh at the mention of the pumpkin; which
chose to tell.
The old country wives, however, who are the best judges of
.
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