What is chordate phylogeny?
Traditional metazoan phylogeny classifies the Vertebrata as a subphylum of the phylum Chordata, together with two other subphyla, the Urochordata (Tunicata) and the Cephalochordata. The Chordata, together with the phyla Echinodermata and Hemichordata, comprise a major group, the Deuterostomia.
What is the origin of chordates?
Chordates evolved from some deuterostome ancestor (echinoderms, hemichordates, pogonophorans etc.) as they have similarities in embryonic development, type of coelom and larval stages. Fossils of the earliest vertebrates are known from the Silurian-Devonian period, about 400 million years ago.
What is the phylogeny of vertebrates?
Vertebrates (backboned animals) are part of the wider group Chordata (see Phylogeny and Evolution of Chordates), characterized by the possession of an axial stiffening rod (notochord), a perforated pharynx, a dorsal hollow nerve cord, and a post-anal tail.
What is the origin and history of vertebrate animals?
Vertebrates originated about 525 million years ago during the Cambrian explosion, which saw rise in organism diversity. The earliest known vertebrate is believed to be Myllokunmingia. One of many early vertebrates are Haikouichthys ercaicunensis.
Who introduced the term chordate?
Although the name Chordata is attributed to William Bateson (1885), it was already in prevalent use by 1880. Ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866.
What is the echinoderm theory of origin of chordates?
ECHINODERM – HEMICHORDATE THEORY: This theory infers origin of chordates, hemichordates and echinoderms from a common ancestor. This theory is based on the following evidences. a) EMBRYOLOGICAL EVIDENCE : Both echinoderms and chordates have enterocoelic coelome, mesoderm and deuterostomous mouth.
Who created phylum Chordata?
Where did jaws evolve from?
Jaws probably originated in the pharyngeal arches supporting the gills of jawless fish. The earliest jaws appeared in now extinct placoderms and spiny sharks during the Silurian, about 430 million years ago.
What is the origin of mammals?
Mammals were derived in the Triassic Period (about 252 million to 201 million years ago) from members of the reptilian order Therapsida. The therapsids, members of the subclass Synapsida (sometimes called the mammal-like reptiles), generally were unimpressive in relation to other reptiles of their time.
Where do the vertebrates come from?
Amphibians, reptiles, mammals, and birds evolved after fish. The first amphibians evolved from a lobe-finned fish ancestor about 365 million years ago. They were the first vertebrates to live on land, but they had to return to water to reproduce. This meant they had to live near bodies of water.
What was the first vertebrate?
jawless fish
In fact, jawless fish are the planet’s first vertebrates and they probably evolved from a creature similar to sea squirts. That’s according to Earth’s calendar year, where 144 years equals one second.
What are the origins and evolution of chordates?
Chordate Origins and Evolution: The Molecular Evolutionary Road to Vertebrates focuses on echinoderms (starfish, sea urchins, and others), hemichordates (acorn worms, etc.), cephalochordates (lancelets), urochordates or tunicates (ascidians, larvaceans and others), and vertebrates.
What are the three major groups of chordates?
Chordates consist of three distinct animal groups: cephalochordates, urochordates (tunicates) and vertebrates. This review starts with a brief description of how the Phylum Chordata and its three subphyla were originally defined, and then discusses how we should reclassify the major chordate groups.
Why is the Chordata called the Vertebrata?
Balfour [ 32] renamed Lankester’s Vertebrata ‘Chordata’, and called the Craniata ‘Vertebrata’. This system has been retained for more than a century due to robustness of the shared character set (notochord, dorsal nerve cord and pharyngeal slits) that Lankester defined.
What kind of gills does a chordate have?
This book discusses the origin and evolution of chordates. Chordates are animals characterized by the possession of a notochord, a dorsal neural tube, somites, pharyngeal gills, an endostyle, and a postanal tail.