Member of the phylum Chordata, animals that at some point during their development have a notochord; a dorsal, hollow nerve cord; pharyngeal slits or clefts; and a muscular, post-anal tail.
A chordate animal with a backbone, including sharks and rays, ray-finned fishes, coelacanths, lungfishes, amphibians, reptiles, and mammals.
A longitudinal, flexible rod made of tightly packed mesodermal cells that runs along the anterior-posterior axis of a chordate in the dorsal part of the body.
In chordate embryos, one of the grooves that separate a series of pouches along the sides of the pharynx and may develop into a pharyngeal slit.
In chordate embryos, one of the slits that form from the pharyngeal clefts and communicate to the outside, later developing into gill slits in many vertebrates.
Member of the clade Cephalochordata, small blade-shaped marine chordates that lack a backbone.
Member of the clade Urochordata, sessile marine chordates that lack a backbone.
A chordate with a head.
In vertebrates, a region located along the sides of the neural tube where it pinches off from the ectoderm. Neural crest cells migrate to various parts of the embryo and form pigment cells in the skin and parts of the skull, teeth, adrenal glands, and peripheral nervous system.
An early, soft-bodied vertebrate with prominent eyes and dental elements.
Member of the vertebrate subgroup possessing jaws.
lateral line system
A mechanoreceptor system consisting of a series of pores and receptor units along the sides of the body in fishes and aquatic amphibians; detects water movements made by the animal itself and by other moving objects.
A member of an extinct group of fishlike vertebrates that had jaws and were enclosed in a tough outer armor.
Any of a group of ancient jawed aquatic vertebrates from the Silurian and Devonian periods.
Member of the class Chondrichthyes, vertebrates with skeletons made mostly of cartilage, such as sharks and rays.
Referring to a type of development in which young hatch from eggs laid outside the mother’s body.
Referring to a type of development in which young hatch from eggs that are retained in the mother’s uterus.
Referring to a type of development in which the young are born alive after having been nourished in the uterus by blood from the placenta.
A common opening for the digestive, urinary, and reproductive tracts found in many nonmammalian vertebrates but in few mammals.
Member of a vertebrate clade with jaws and mostly bony skeletons.
In aquatic osteichthyans, a protective bony flap that covers and protects the gills.
In aquatic osteichthyans, an air sac that enables the animal to control its buoyancy in the water.
Member of the class Actinopterygii, aquatic osteichthyans with fins supported by long, flexible rays, including tuna, bass, and herring.
Member of the vertebrate clade Sarcopterygii, osteichthyans with rodshaped muscular fins, including coelacanths, lungfishes, and tetrapods.
A vertebrate clade whose members have limbs with digits. Include mammals, amphibians, and birds and other reptiles.
Member of the tetrapod class Amphibia, including salamanders, frogs, and caecilians.
Member of a clade of tetrapods named for a key derived character, the amniotic egg, which contains specialized membranes, including the fluid-filled amnion, that protect the embryo. Include mammals as well as birds and other reptiles.
An egg that contains specialized membranes that function in protection, nourishment, and gas exchange. It was a major evolutionary innovation, allowing embryos to develop on land in a fluid-filled sac, thus reducing the dependence of tetrapods on water for reproduction.
Member of the clade of amniotes that includes tuataras, lizards, snakes, turtles, crocodilians, and birds.
Referring to organisms for which external sources provide most of the heat for temperature regulation.
Referring to organisms that are warmed by heat generated by their own metabolism. This heat usually maintains a relatively stable body temperature higher than that of the external environment.
A basal group of reptiles, consisting mostly of large, stocky quadrupedal herbivores. They died out in the late Triassic period.
Member of an amniote clade distinguished by a pair of holes on each side of the skull. Diapsids include the lepidosaurs and archosaurs.
Member of the reptilian group that includes lizards, snakes, and two species of New Zealand animals called tuataras.
Member of the reptilian group that includes crocodiles, alligators and dinosaurs, including birds.
Winged reptile that lived during the Mesozoic era.
Member of an extremely diverse clade of reptiles varying in body shape, size, and habitat. Birds are the only extant dinosaurs.
Member of a group of dinosaurs that were bipedal carnivores.
Member of the group of flightless birds.
Member of the class Mammalia, amniotes that have hair and mammary glands (glands that produce milk).
Member of an amniote clade distinguished by a single hole on each side of the skull. Include the mammals.
An egg-laying mammal, such as a platypus or echidna. Like all mammals, they have hair and produce milk, but they lack nipples.
A mammal, such as a koala, kangaroo, or opossum, whose young complete their embryonic development inside a maternal pouch called the marsupium.
A structure in the pregnant uterus for nourishing a viviparous fetus with the mother’s blood supply; formed from the uterine lining and embryonic membranes.
Placental mammal; mammal whose young complete their embryonic development within the uterus, joined to the mother by the placenta.
A thumb that can touch the ventral surface of the fingertips of all four fingers.
Member of a primate group made up of the monkeys and the apes (gibbons, orangutans, gorillas, chimpanzees, bonobos, and humans).
The study of human origins and evolution.
A member of the human branch of the evolutionary tree. Include Homo sapiens and our ancestors, a group of extinct species that are more closely related to us than to chimpanzees.
Basal chordates; marine suspension feeders that exhibit four key derived characters of chordates
Marine suspension feeders; larvae display the derived traits of chordates
Myxini (Chordates --> Craniates)
(hagfishes and relatives)
Jawless marine organisms; have head that includes a skull and brain, eyes, and other sensory organs
Petromyzontida (Chordates --> Craniates --> Vertebrates)
Jawless vertebrates; typically feed by attaching to a live fish and ingesting its blood
Chondrichthyes (Chordates --> Craniates --> Vertebrate --> Gnathostomes)
(sharks, rays, skates, ratfishes)
Aquatic gnathostomes; have cartilaginous skeleton, a derived trait formed by the reduction of an ancestral mineralized skeleton
Actinopterygii (Chordates --> Craniates --> Vertebrate --> Gnathostomes --> Osteichthyans)
Aquatic gnathostomes; have bony skeleton and maneuverable fins supported by rays
Actinistia (Chordates --> Craniates --> Vertebrate --> Gnathostomes --> Osteichthyans --> Lobe-fins)
Ancient lineage of aquatic lobe-fins still surviving in Indian Ocean
Dipnoi (Chordates --> Craniates --> Vertebrate --> Gnathostomes --> Osteichthyans --> Lobe-fins)
Freshwater lobe-fins with both lungs and gills; sister group of tetrapods
Amphibia (Chordates --> Craniates --> Vertebrate --> Gnathostomes --> Osteichthyans --> Lobe-fins --> Tetrapods)
(salamanders, frogs, caecilians)
Have four limbs descended from modified fins; most have moist skin that functions in gas exchange; many live both in water (as larvae) and on land (as adults)
Reptilia (Chordates --> Craniates --> Vertebrate --> Gnathostomes --> Osteichthyans --> Lobe-fins --> Tetrapods --> Amniotes)
(tuataras, lizards and snakes, turtles, crocodilians, birds)
One of two groups of living amniotes; have amniotic eggs and rib cage ventilation, key adaptations for life on land
Mammalia (Chordates --> Craniates --> Vertebrate --> Gnathostomes --> Osteichthyans --> Lobe-fins --> Tetrapods --> Amniotes)
(monotremes, marsupials, eutherians)
Evolved from synapsid ancestors; include egg-laying monotremes (echidnas, platypus); pouched marsupials (such as kangaroos, opossums); and eutherians (placental mammals, such as rodents, primates)