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Order Pterocliformes, sandgrouse (this enigmatic group was traditionally treated as a family in any of three different orders: Charadriiformes, Ciconiiformes, and Columbiformes) Order Columbiformes, doves, pigeons and dodos; Order Psittaciformes, parrots and allies; Order Cuculiformes, cuckoos; Order Strigiformes, owls
A chordate (/ ˈ k ɔːr d eɪ t / KOR-dayt) is a deuterostomal bilaterian animal belonging to the phylum Chordata (/ k ɔːr ˈ d eɪ t ə / kor-DAY-tə). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies ) that distinguish them from other taxa .
Chordate genomics is the study of the evolution of the chordate clade based on a comparison of the genomes of several species within the clade. The field depends on whole genome data (the entire DNA sequence ) of organisms.
Molecular studies by molecular systematists, based on DNA analysis, in the early 21st century have revealed new relationships among mammal families. Classification systems based on molecular studies reveal three major groups or lineages of placental mammals, Afrotheria, Xenarthra, and Boreoeutheria. which diverged from early common ancestors in the Cretaceous.
Imaginary cladogram. [2] The yellow mask is a plesiomorphy for each living masked species, because it is ancestral. [2] It is also a symplesiomorphy for them. But for the four living species as a whole, it is an apomorphy because it is not ancestral for all of them. The yellow tail is a plesiomorphy and symplesiomorphy for all living species.
The calcichordate family tree in its original incarnation, with all chordates originating from a soft bodied ancestor. Later versions of the theory had each chordate group having a mitrate ancestor each, requiring three episodes of loss of stereom. Mitrates are assumed to have evolved from the cornutes. [6]
They resembled sharks and were ancestral to them. Spiny sharks, class Acanthodii, are extinct fish that share features with both bony and cartilaginous fish, though ultimately more closely related to and ancestral to the latter. Despite being called "spiny sharks", acanthodians predate sharks, though they gave rise to them.
Harvard University palaeontologist Stephen Jay Gould popularised Pikaia as an ancestral species of chordates in his 1989 book Wonderful Life: The Burgess Shale and the Nature of History, [13] from which Pikaia became known as the "most famous early chordate fossil," [14] or the earliest chordate, [15] or the oldest ancestor of humans. [16] [17]