Chordata

## Range

Rimunian - Today (Liaopingian - Holocene) 509 - 0 Ma

## Families

* †Liaopingichthyidae
* †Pingshuichthyidae
* Vertebrata

Chordates are a type of deuterostome that are characterized by their five synapomorphies, or primary characteristics, at some point during their larval or adulthood stages that distinguish them from all other taxa. These five synapomorphies include a notochord, dorsal hollow nerve cord, endostyle or thyroid, pharyngeal slits, and a post-anal tail. They are the most diverse member of the deuterostomes. Chordates are bilaterally symmetrical, have a coelom, possess a circulatory system, and exhibit metameric segmentation.

## Anatomy

Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features.

* A notochord, a stiff rod of cartilage that extends along the inside of the body. This notochord develops into the spine, which in wholly aquatic species helps the animal swim by flexing its tail.
* A dorsal neural tube. This evolved into the spinal cord, the main communication trunk of the nervous system.
* Pharyngeal slits. The pharynx is the part of the throat immediately behind the mouth. In fish the slits are modified to form gills, but in some other chordates is used to filter-feed.
* Post-anal tail. A muscular tail that extends behind the anus. In some chordates this is only present in the embryonic stage.
* An endostyle. This is a groove in the ventral wall of the pharynx. In filter-feeding species it produces a mucus to gather food particles, which help in transporting to the esophagus. It also stores iodine and may be a precursor to the thyroid gland.

## Classification

* Superphylum Deuterostomia
	+ Phylum **Chordata**
		- †Pingshuichthyidae
		- †Liaopingichthyidae
		- Vertebrata
			* Agnatha
				+ †Gnathodidae
				+ †Fuqiuichthyidae
				+ †Haleichthyidae
				+ Cyclostomata
				+ Ostracocephalia
					- Seijaspidae
						* †Patoaspida
						* †Domuaspida
							+ †Pteroaspina
						* Cephalaspia
							+ †Quinichthyida
								- †Palaeoceratoichthoidea
									* †Palaeoceratoichthyidae
										+ †Palaeoceratoichthyinae
											- †Akouwalepini
							+ Cephalaspoidea
								- †Eocephaloichthyidae
								- †Cephaloichthyidae
								- †Cephalspidae
									* †Cephalaspinae
									* †Leniscephalinae
										+ †Platycephalini
								- †Pseudosteoichthyidae
								- Gnathostoma
									* Placodermi
										+ †Pterichthyida
											- †Rericalepidae
										+ †Baryaspidae
										+ Arthrodira
											- †Titanichthyidae
											- †Kapikosteidae
											- †Omuvasteidae
											- Neenorasteidae
												* Haplopsopodamorpha
													+ Euhaplopsopoda
														- †Mianjingcephalidae
														- Haplopsopoda
									* Eugnathostoma
										+ †Compspinodia
											- †Compspinodoidea
												* †Compspinodidae
													+ †Compspinodinae
										+ Chondrichthyes
											- †Pectopteryxidae
											- †Waysonidae
											- Carcharia
												* Pseudosqualidae
												* Eucarcharia
										+ Osteichthyes
											- Sarcopterygii
												* Actinistia
												* Pulmoichthyiformes
													+ Pulmoichthyia
														- Tetrapodamorpha
															* †Meidongidae
															* Eubennastegalia
																+ ?†Tapazaherpeton
																+ Bennastegalia
																	- Tetrapoda
												* †Aputodontidae
											- Actinopterygii
												* †Paleoactinopterygii
													+ †Mianxingichthyidae
													+ †Donolaichthyidae
													+ †Chiboichthyidae
												* Saldobiidae