Scientists use the fossil record and structural and molecular comparisons to construct phylogenetic trees. This answer came straight from my freshman Biology book.
The description of synapomorphies (A derived trait shared by two or more species that is believed to reflect their shared ancestry) is important in the work of systematics (taxonomy) because then the systematists can know how the two or more species is related.
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WOLF!
evolutionary
Systematics
Systematics is the science dedicated to inventorying and describing biodiversity and understanding the phylogenetic relationships between organisms.
The answer depends on the time period, and what is meant by systematics. In it's broadest definition, the study of diversification in organisms and their relationships through time, I think that Carl Linnaeus is the most obvious contributor from early naturalists. Willi Hennig, German biologist, also comes to mind, for more recent phylogenetic systematics.
Xiaoming Wang has written: 'Phylogenetic systematics of the Hesperocyoninae (Carnivora:Canidae)' -- subject(s): Canidae, Fossil, Fossil Canidae, Paleontology
Aaron M. Bauer has written: 'Phylogenetic systematics and biogeography of the Carphodactylini (reptilia: Gekkonidae)' -- subject(s): Classification, Geckos, Geographical distribution
Phylogenetic classification groups animals based on their evolutionary relationships and genetic similarities. This form of classification organizes animals into groups based on their shared ancestry and common descent.
Phylogenetic
Systematics try to figure out their evolutionary relationships.
unda
what is classical systamatics
Taxonomic
Systematics and taxonomy.