In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to have evolved in their most recent common ancestor.
In cladistics, synapomorphy implies homology.
Asparagales (asparagoid lilies) are a diverse order of flowering plants in the monocots. Under the APG IV system of flowering plant classification, Asparagales are the largest order of monocots with 14 families, 1,122 genera, and about 36,000 species, with members as varied as asparaguses, orchids, yuccas, irises, onions, garlics, leeks, and other alliums, daffodils, snowdrops, amaryllis, agaves, butcher's broom, agapanthuses, Solomon's seal, hyacinths, bluebells, spider plants, grasstrees, aloes, freesias, gladioli, crocuses, and saffrons.
Most species of Asparagales are herbaceous perennials, although some are climbers and some are trees or shrubs. The order also contains many geophytes (bulbs, corms, and various kinds of tuber). The leaves of almost all species form a tight rosette, either at the base of the plant or at the end of the stem, but occasionally along the stem. The flowers are not particularly distinctive, being 'lily type', with six tepals and up to six stamens. One of the defining characteristics (synapomorphies) of the order is the presence of phytomelanin, a black pigment present in the seed coat, creating a dark crust. Phytomelanin is found in most families of the Asparagales (although not in Orchidaceae, thought to be the sister-group of the rest of the order).
Cladistics (/kləˈdɪstɪks/ klə-DIST-iks; from Ancient Greek κλάδος kládos 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived characteristics (synapomorphies) that are not present in more distant groups and ancestors. However, from an empirical perspective, common ancestors are inferences based on a cladistic hypothesis of relationships of taxa whose character states can be observed. Theoretically, a last common ancestor and all its descendants constitute a (minimal) clade. Importantly, all descendants stay in their overarching ancestral clade. For example, if the terms worms or fishes were used within a strict cladistic framework, these terms would include humans. Many of these terms are normally used paraphyletically, outside of cladistics, e.g. as a 'grade', which are fruitless to precisely delineate, especially when including extinct species. Radiation results in the generation of new subclades by bifurcation, but in practice sexual hybridization may blur very closely related groupings.
As a hypothesis, a clade can be rejected only if some groupings were explicitly excluded. It may then be found that the excluded group did actually descend from the last common ancestor of the group, and thus emerged within the group. ("Evolved from" is misleading, because in cladistics all descendants stay in the ancestral group). To keep only valid clades, upon finding that the group is paraphyletic this way, either such excluded groups should be granted to the clade, or the group should be abolished.
The Rhizaria are a diverse and species-rich clade of mostly unicellular eukaryotes. Except for the chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthetic, but many Foraminifera and Radiolaria have a symbiotic relationship with unicellular algae. A multicellular form, Guttulinopsis vulgaris, a cellular slime mold, has been described. This group was used by Cavalier-Smith in 2002, although the term "Rhizaria" had been long used for clades within the currently recognized taxon.
Being described mainly from rDNA sequences, they vary considerably in form, having no clear morphological distinctive characters (synapomorphies), but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods. In the absence of an apomorphy, the group is ill-defined, and its composition has been very fluid. Some Rhizaria possess mineral exoskeletons (thecae or loricas), which are in different clades within Rhizaria made out of opal (SiO2), celestite (SrSO4), or calcite (CaCO3).
The Brachiosauridae ("arm lizards", from Greek brachion (βραχίων) = "arm" and sauros = "lizard") are a family or clade of herbivorous, quadrupedal sauropod dinosaurs. Brachiosaurids had long necks that enabled them to access the leaves of tall trees that other sauropods would have been unable to reach. In addition, they possessed thick spoon-shaped teeth which helped them to consume tough plants more efficiently than other sauropods. They have also been characterized by a few unique traits or synapomorphies; dorsal vertebrae with 'rod-like' transverse processes and an ischium with an abbreviated pubic peduncle.
Brachiosaurus is one of the best-known members of the Brachiosauridae, and was once thought to be the largest land animal to ever live. Brachiosaurids thrived in the regions which are now North and South America, Africa, Europe and Asia. They first appear in the fossil record in the Late Jurassic period (possibly even earlier in the Middle Jurassic) and disappear in the late Early Cretaceous period. The broad distribution of Brachiosauridae in both northern and southern continents suggests that the group originated prior to the breakup of Pangaea. In the Early Cretaceous the distribution of the group is dramatically reduced. It is still unclear whether this reduction is due to local extinctions or to the limited nature of the Early Cretaceous fossil record.
Halecomorphi is a taxon of ray-finned bony fish in the clade Neopterygii. The only extant Halecomorph species are the bowfin (Amia calva) and eyespot bowfin (Amia ocellicauda), but the group contains many extinct species in several families (including Amiidae, Caturidae, Liodesmidae, Sinamiidae) in the order Amiiformes, as well as the extinct orders Ionoscopiformes, Ophiopsiformes, Panxianichthyiformes, and Parasemionotiformes. The fossil record of halecomorphs goes back at least to the Early Triassic epoch.
The Halecomorphi exhibit a combination of ancestral features, such as most heavily mineralized scales, but also by more derived or "modern" features, particularly in the structure of the skull (e.g. position and shape of preopercles). Unique derived traits (synapomorphies) of the Halecomorphi include:
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic with respect to the excluded subgroups. In contrast, a monophyletic grouping (a clade) includes a common ancestor and all of its descendants.
The terms are commonly used in phylogenetics (a subfield of biology) and in the tree model of historical linguistics. Paraphyletic groups are identified by a combination of synapomorphies and symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic.