Evolution and Characteristics of later vertebrates: Tetrapods and Mammals

Tetrapods

Group where fins evolved into the limbs and feet. These have four limbs, and feet with digits; neck, which allows separate movement of the head; fusion of the pelvic girdle to the backbone; absence of gills (except some aquatic species); ears for detecting airborne sounds

Origin of Tetrapods

Tiktaalik has both fish and tetrapod characteristics. It had fins, gills, lungs, and scales; ribs to breathe air and support the body; neck and shoulders; and fins with the bone patterns of a tetrapod limb

Tiktaalik

It had fins, gills, lungs, and scales; ribs to breathe air and support the body; neck and shoulders; and fins with the bone patterns of a tetrapod limb. It could not walk. Arrived in the devonian era..

Devonian Era

Period when first tetrapods appeared, 365 mya.

Amniotes

The amniotic egg, which contains membranes that protect the embryo. The extraembryonic membranes are the amnion, chorion, yolk sac, and allantois. Diverged about 350 mya. The living members are the reptiles, including birds, and mammals

Amniotic Egg

Egg with protective membranes for embryo development.

Amphibians

ectothermic, an amniotic, four-limbed vertebrate animal. Can be broken down into three clades: Urodela (salamanders), Anura (frogs), & Apoda (caecilians).

Urodela

Clade of amphibians including salamanders. Amphibians with tails. Some are aquatic, but others live on land as adults or throughout life and undergo paedomorphosis.

Anura

Clade of amphibians including frogs.lack tails and have powerful hind legs for locomotion on land

Caecilians

Amphibian clade, including apoda. legless, nearly blind, and resemble earthworms. The absence of legs is a secondary adaptation

Paedomorphosis

Retention of juvenile traits in adult organisms.

Ectothermic

Organisms that regulate body temperature externally.

Endothermic

Organisms that maintain body temperature metabolically.

Reptiles

Ectothermic tetrapods with amniotic development and scales.

Parareptiles

Emerged about 310 mya and were large, stocky quadrupedal herbivores

Diapsids

Reptiles with two temporal fenestrae in skull. From the main lineages: the lepidosaurs and the archosaurs

Lepidosaurs

Reptiles with limbs sticking out; includes lizards and snakes

Snakes

carnivorous legless lepidosaurs that evolved from lizards. Some have adaptations to aid in capture and consumption of prey including: Chemical sensors, heat-detecting organs, venom & loosely articulated jawbones and elastic skin

Archosaurs

Ruling reptiles, including dinosaurs and crocodilians.

Pterosaurs

First flying tetrapods, related to dinosaurs.

Crocodilians

Archosaurs from late Triassic, live in warm regions.

Turtle

A boxlike shell made of upper and lower shields that are fused to the vertebrae, clavicles, and ribs. Phylogenetic position of turtles remains uncertain

Birds

Endothermic archosaurs adapted for flight.

Archaeopteryx

Oldest known bird, dating to 160 mya.

Mammals

Amniotes with mammary glands and hair.

Derived characteristics of mammals

Mammary glands, which produce milk, Hair, a high metabolic rate, due to endothermy, a larger brain than other vertebrates of equivalent size, & differentiated teeth

Lineages of mammals

Emerged in the early Cretaceous with three living lineages: monotremes, marsupials, and eutherians

Synapsids

Amniotes with a single temporal opening in skull.

Monotremes

Egg-laying mammals like echidnas and platypus.

Marsupials

The embryo develops within a placenta in the mother's uterus and completes its embryonic development while nursing in a maternal pouch called a marsupium. It is born very early in its development

Eutherians

Mammals with complex placenta for fetal development.

Primates

Order of mammals with grasping hands and flat nails.

Derived characteristics of primates

A large brain and short jaws; forward-looking eyes close together on the face, providing depth perception; complex social behaviour and parental care; a fully opposable thumb

Bipedalism

Locomotion using two legs for walking.

Hominins

Members of tribe Hominini, including modern humans.

Australopiths

4 and 2 million years ago. Some species, such as Australopithecus afarensis walked fully erect. Terrestrial bipedal ape-like animals that had large chewing teeth with thick enamel caps, but whose brains were only very slightly larger than those of great ape. Most famous named Lucy.

Tool usage

Oldest evidence are cut marks on animal bones is 2.5 million years old. Fossil evidence indicates usage may have originated prior to the evolution of large brains

Homo habilis

earliest fossils placed in our genus Homo, ranging in age from about 2.4 to 1.6 million years. Stone tools have been found with them, giving this species its name, which means "handy man."

Homo ergaster

The first fully bipedal, large-brained hominid. The species existed between 1.9 and 1.5 million years ago; shows a significant decrease in sexual dimorphism

Homo erectus

First hominin to leave Africa, 1.8 mya.

Homo neanderthalensis

Thick-boned hominins with a larger brain, they buried their dead, and they made hunting tools. from Europe, 350,000 to 28,000 years ago.

Homo sapiens

Appeared in Africa 195,000 years ago. Upright posture and bipedal locomotion; Larger brains capable of language; symbolic thought; artistic expression; the manufacture and use of complex tools; Reduced jawbones and jaw muscles; Shorter digestive tract

The first monkeys evolved

Old World (Africa and Asia)

New World Monkeys

Found in the Americas, have flat noses with outward-facing nostrils, and some species possess prehensile tails

Old world monkeys

native to Africa, Asia, and Europe, have downward-pointing noses with nostrils closer together, and lack prehensile tails.