symplesiomorphy

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symplesiomorphy

the sharing of ancestral characters by different species.
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We now recognize that unsclerotized sigilla are symplesiomorphic for Arbanitinae, and therefore of no diagnostic or phylogenetic value in most taxa.
Because of the high resemblance of such pairs in the three Acanthurus species, they are supposed to share a common origin before the differentiation of each lineage, thereby indicating a symplesiomorphic trait.
Because the symplesiomorphic conditions of all of these were considered statistically linked, Bailey and his co-workers considered that any one of the symplesiomorphic character states (e.g., diffuse axial parenchyma, more numerous bars per perforation plate) could be substituted for vessel element length as a "measuring stick" for phyletic advancement.
The presence of short scutellum is symplesiomorphic among Procleticini, and does not support the grouping proposed by Rider (1994).
A particularly interesting question in the evolution of stork behavior is whether solitary or colonial nesting, and the presumably associated wealth of courtship display behaviors, is symplesiomorphic. The well-supported basal bifurcation in the storks splits the family into two equally sized clades with contrasting nesting habits: the Mycteria-Leptoptilos-Anastomus group includes only highly colonial species that share a number of characteristic courtship displays, and the Ephippiorhynchus-Jabiru-Ciconia group includes species with a variety of nesting habits, ranging from highly colonial (C.
The extensive occurrence of multiple NORs present in two or three chromosome pairs seems to indicate that this is a symplesiomorphic condition for the family.
One might argue that these style characters are symplesiomorphic, however primitive and advanced states recognition for these features depends on the choice of the outgroup (Calyceraceae, Goodeniaceae, Menyanthaceae).
The "missing" gain is a symplesiomorphic (shared primitive) instance of the character retained from the base of the tree, hence cases with zero gains of tristyly in Table 1a,b.
Since the two cotyledons of dicots do not appear to be homologous to the next-developed leaves of the same stem and are very likely the product of an independent genetic program, it is possible that they are also not homologous with the two cotyledons found in most other seed plants, and that dicotyledonous seeds in more-distant gymnosperm lineages may prove to be convergent character states, rather than a single shared symplesiomorphic trait among all seed plants.
Similarly, the observation that biparental care is symplesiomorphic in a clade of fishes would not invalidate the hypothesis of its selective maintenance in any given species within the clade.