Classification Construct : The Second Lineage Of Terrestrial Vertebrates ( Amniote Tetrapods )

A dinosaur has an antorbital fenestra with an open hole hip socket. The definition differs from the term used informally because it helped understand how the dinosaur moved and how they were categorized as species. There are four general characteristics that dinosaurs have as a result of their synapomorphies which are permeated acetabulum, ball-shaped head on proximal femur, the Cnemial crest on the proximial tibia, and an ascending process on astragalus. These four dinosaur synapomorphies are related to vertical limb support.

During the middle to late Eocene and into the Oligocene epoch several other members of the equids, with distinct evolutionary changes, existed including the Orohippus, Epihippus, Mesohippus, and Miohippus. The Orohippus developed from the Hyracotherium and shared many of the same traits. One major change was that the first and second toes disappeared. Another significant change occurred in the teeth. The last premolar changed to become like a grinding molar. Also the crests were more defined showing that the Orohippus’s diet had changed to a tougher plant material. During the middle Eocene a descendant of Orohippus appeared. The Epihippus still resembled a dog-like animal. It had four padded toes on the front leg, and three on the back leg. However, the teeth changed more drastically with two of the premolars changing to grinding molars. Now there were five grinding cheek teeth with low crowns. As

Amphibians skin is moist and they do not consist of scales. The skin of an amphibian is also permeable. Permeable means that gases can pass through their skin. A reptiles’ scales provide them with a protective layer of skin that is tough and dry. The scales help to minimize the loss of body moisture, the reptilian scales consists of a protein called keratin. The scale structure of a reptile are not individual like those of a fish, but are a continuous sheet of epidermal tissue. Hard-shelled eggs provide a protective environment in which the embryo can develop and enables reptiles to lay their eggs in dry environments. On the other hand, amphibians must lay their eggs in or near water. The reptilian skeleton differs from other vertebrates in many ways. For example, reptiles have many bones in their lower jaw to enable them a greater bite mobility, but mammals only have one bone in their lower jaw called the mandible. Mammals ears consist of three bones(the malleus, incus, and stapes) while reptiles have just one bone(stapes). Reptiles also have only one occipital condyle(a protrusion on the skull that forms a joint that enables movement of the head) mammals on the other hand consist of two occipital condyles (Laura Klappenbach 2014).

Recent evidence suggests that whales may not have always inhabited the oceans. Bones of an ancient ancestor of modern day whales, the Basilosaurus, were discovered in Pakistan that suggest whales evolved from a wolf-like creature. This genus of an early whale lived 34-40 million years ago in the late Eocene. These fossils show many different features in common with both modern day whales and modern day land mammals. Since the discovery of these bones, many other evidences show that whales are a likely descendant of the Basilosaurus through many different ways, such as embryologic comparison and DNA testing. Whales aren’t the only suspected descendants

Lemuroids are prosimians dating back to as early as 65 million years ago (Larsen). They were the primates present during the Paleocene epoch of the Cenozoic era (Larsen). Having many attributes that pertain to the early primates they help give an insight to the evolution of dentition within early primates (Doyle). This helps understand the fore coming other grades of primates dentition; for example, tarsiers, monkeys, apes and hominids.

Our arches are the beginnings of gills in most fish, and shark species, but in humans they usually will close and form the usual structures. In most animals these same four arches can also be found, further showing their similarity to sharks. Also the arches create the same or similar structures in sharks and humans, the first arch creates the jaw, and trigeminal nerve in both humans, and sharks. The second arch creates one of the bones in the ear, but also the hyoid, a bone at the base of the skull. In sharks the second arch will create a similar bone that supports their jaws. All of these show how our heads, and many other animals heads, are all created from a similar structure.

Fossils provide a record of how organisms have evolved overtime, as they contain the remains of life trapped in sediment, ice or amber and preserved for over millions of years. Transitional fossils, which provide evidence for evolutionary change, have features that show the transition of characteristics of organisms from ancestors to descendents. An example is Archaeopteryx, which featured reptilian features, including teeth and skeleton, however, also had feathers and a wishbone sternum (used to attach muscles for flying). The evidence of the fossil shows the evolutionary transition between dinosaurs and

Mary Anning’s contribution to the development of the understanding of how reptiles contributed to evolution and to the understanding of fossils as extinct life forms was important.

The fossil of Tiktaalik confirmed a major prediction of paleontology in that it showed characteristics of both aquatic animals, such as fish, and land animals, such as reptiles and amphibians. While it had fins and scales, it also had a flexible neck, a flat head, and complex bone structure in its fins that correspond with the structure of the legs of terrestrial animals. Thus, it demonstrates the evolutionary transition between aquatic and terrestrial life.

The detractors of “Nonavian Feathers in a Late Triassic Archosaur” believe that the feather-like impressions in the fossil are not even feathers at all. Based on the angle and shape of the imprints, many paleontologists believe that they were left by ‘highly modified scales’, or possibly even ferns that had fallen on the animal’s body after death.4

Females for the nourishment of the young could define a mammal as a warm-blooded vertebrate animal of a class that is distinguished by the possession of hair or fur, the secretion of milk. The roots of the mammalian line reach back almost 300 million years. Some of the very early mammal relatives dominated the landscape millions of years before dinosaurs appeared, and most of these species became extinct. During the age of dinosaurs, most mammals were not much bigger than small rodents. It was after the extinction of the large dinosaurs that the great diversity of mammals arose. The timeline in this hall displays the development of such key mammalian physical features as the synapsid opening in the skull, a large hole behind the eye socket

The epoch is considered one of the essential time because of the major transition earth went through; the development of tropical forests and grasslands that expanded globally. Apidiums and aegyptopithecus lived during this epoch. Apidiums are around the size of a squirrel and their dental formulae suggest that they were frugivores and possibly seed eaters. There is also a significant difference in size between male and female apidiums, which suggest a strong sexual dimorphism. Apidiums’ limb remains also show that they excel in leaping and jumping. Aegyptopithecus share a similar dental formula as apidiums which means they possibly have the same diet. According to R. Jurmain and other authors (1979), aegyptopithecus “was likely a short-limbed, heavily muscled, slow-moving arboreal quadruped” and “was long viewed as the best candidate from the Fayum to have given rise to Old World monkeys, apes, and

Any lift that would come out of the winged features would generate drag causing a loss in acceleration. 1 However, just as the Arobreal theory was supported by Archaeopteryx, the Cursorial theory is also strongly supported by this specimen. Archaeopteryx demonstrates a complete set of conical teeth and claws that were sharp and resembling the specimens relative Ornitholestes, a known predaceous animal.3 The Archaeopteryx also resembles therapods with a reversed hallux, hindlimb, and pelvis.3 Even though this theory is supported using fossil evidence, it does have some problems which have lead to the development of theories such as the WAIR

The author suggest that mammals existed during the dinosaurs' era and had relied on eggs of dinosaurs. As a result, this might had also contributed dinosaur

My outside source for questions 3 and 4 is a journal by Pat Shipman titled Fossils. This journal was published in The New Scientist Vol. 215, Issue 2876, p. 8-16.