Evolution of the Tetrapods A1

Eusthenopteron

genus of extinct lobe-finned fishes Eusthenopteron was near the main line of evolution leading to the first terrestrial vertebrates, the tetrapods a lobe finned fish from 385 MYA They're one of the Devonian lobe-finned prehistoric fishes that have limbs that are much like the first amphibian Ichthyostega Class=Sarcopterygii

Tetrapod

a tetrapod is a fish with 4 legs Tetrapoda contains 4 limbed vertebrates including terrestrial vertebrates like amphibians, reptiles, and mammals, birds tetrapods evolved from Sarcopterygii

The Diapsids

infra and supra orbital fenestra The lepidosaurs (scaly lizard) The Archosaurs (the ruling lizards) -Antorbital opening Sauropterygia (Plesiosaurs) Ichthyosaurs

Gymnophiona (Apoda)

Cecilians Caecilians are a group of limbless, serpentine amphibians. They mostly live hidden in the ground. All modern caecilians and their closest fossil relatives are grouped as a clade, Apoda, within the larger group Gymnophiona 165 species Annular rings Sensory tentacles Skull reduction/ fusion Collagenous scales Eyes reduced Left lung reduced Male phallodium

Diapsids ("two arches") are a group of amniote tetrapods that developed two holes (temporal fenestra) in each side of their skulls

The diapsids are extremely diverse, and include all crocodiles, lizards, snakes, tuatara, turtles, and dinosaurs (both avian and non-avian)

Tiktaalik

Tiktaalik is a monospecific genus of extinct sarcopterygian (lobe-finned fish) from the late Devonian period, about 375 MYA, having many features akin to those of tetrapods Tiktaalik has a possibility of being a representative of the evolutionary transition from fish to amphibians. discovery sheds light on a pivotal point in the history of life on Earth: when the very first fish ventured out onto land. Tiktaalik has a mix of fish and amphibian traits

Synapsid jaw

A single temporal opening around which jaw muscles attach is a feature shared by all synapsids

Diapsid

All members of the group called the Reptilia (see below), except for the anapsids (turtles and their ilk), and a few extinct groups, are diapsids. The main diagnostic physical character for a diapsid is the presence of two openings on each side of the skull; the upper and lower temporal openings

Anura

Frogs and toads The order Anura includes the frogs and toads. Anurans represent, by far, the most speciose, diverse, and widespread of the three extant amphibian orders. Ubiquitous geographic distribution Habitat types include many counter- intuitive places ie arid desert regions, to mountainous regions, to swamps to tropical rainforests

Sarcopterygii

Lobe finned Fish Sarcopterygii are the lobe-finned fish and the tetrapods given rise to terrestrial vertebrates (mammals, reptiles, amphibians, birds) fleshy, lobed fins that characterize the class Sarcopterygii (lobe-finned fish) contains only a few living representatives coelacanth, lungfish

Lissamphibia

Modern Amphibians Lissamphibia (20% of Tetrapods) comprised of 3 groups: Gymnophiona = caecilians Urodela (Caudata) = salamanders Anura = frogs The Lissamphibia are a group of tetrapods that includes all modern amphibians Lissamphibians consist of three living groups: the Salientia (frogs, toads, and their extinct relatives), the Caudata or Urodela (salamanders, newts, and their extinct relatives), and the Gymnophiona (the limbless caecilians and their extinct relatives).

Actinopterygii

Ray finned Fish ray-finned fishes are so called because their fins are webs of skin supported by bony or horny spines ("rays") Ray-finned fishes are the dominant aquatic vertebrates today, making up about half of all vertebrate species known tarpon, herring, perch, sturgeon

Urodela

Salamanders 415 species Costal grooves Reduced skull bones numbers but no fusion Lack tympanum Mucus, Mental, cheek, cloacal glands, Granular glands Spermatophores(Usually) Direct development common Paedomorphosis common

Synapsid

Synapsids, is a taxonomic class of tetrapods. This class includes mammals and earlier groups related to mammals. Synapsids are one of the two major groups of amniotes.

Zygopophyses

articulation points on vertebrae that link vertebrate to each other zygapophyses of a vertebra, are projections of the vertebra that serve the purpose of fitting with an adjacent vertebra

Mesozoic

begins 251 MYA The Mesozoic Era is an interval of geological time from about 251 to 66 million years ago. It is also called the Age of Reptiles, dominated by diapsids era is subdivided into three major periods: the Triassic, Jurassic, and Cretaceous Dinosaurs appeared in the Late Triassic and became the dominant terrestrial vertebrates early in the Jurassic, their demise at the end of the Cretaceous Birds first appeared in the Jurassic first mammals also appeared during the Mesozoic

Permian

begins 299 MYA The Permian is a geologic period and system which spans from the end of the Carboniferous Period 299 million years ago (Mya), to the beginning of the Triassic Period 251 Mya diversification of the early amniotes into the ancestral groups of the mammals, turtles, lepidosaurs, and archosaurs The Permian ended with the Permian-Triassic extinction event, the largest mass extinction in Earth's history

Carboniferous

begins 359 MYA The Carboniferous is a geologic period and system that spans from the end of the Devonian Period 359 million years ago (Mya), to the beginning of the Permian Period, 299 Mya Amphibians were the dominant land vertebrates, of which one branch would eventually evolve into amniotes, the first solely terrestrial vertebrates

Devonian

begins 416 MYA The Devonian is a geologic period and system of the Paleozoic, from the end of the Silurian, 416 million years ago (Mya), to the beginning of the Carboniferous, 359 Mya first significant adaptive radiation of life on dry land occurred during the Devonian Devonian to often be dubbed the "Age of Fish". The first ray-finned and lobe-finned bony fish appeared!

Silurian

begins 443 MYA The Silurian is a geologic period and system from the end of the Ordovician Period, at 443 million years ago, to the beginning of the Devonian Period, 416 Mya evolutionary milestone during the Silurian was the diversification of jawed and bony fish

Ichthyostega

early tetrapod genus that lived at the end of the Upper Devonian period Ichthyostega possessed lungs and limbs that helped it navigate through shallow water in swamps Of amphibian build and habit, it is not considered a true member of the group in the narrow sense

Amniote tetrapods (i.e., those terrestrial vertebrates that produce eggs in which the embryo is surrounded by a series of extra-embryonic membranes) in the modern world can be divided into two great lines of descent

the Reptilia and the Synapsida The reptile and synapsid lineages both descend from a common ancestor, but that divergence is ancient