The transition between theropod dinosaur and bird is exquisitely documented in the fossil record and it is now widely accepted that birds are descended from theropod dinosaurs. Birds also share many traits with their dinosaurian ancestors, including bipedalism (the basal form of locomotion in dinosaurs) and digitigrade movement. However, there are several functional differences in bipedalism between basal theropods and their bird descendants. Non-avian theropods were, largely, terrestrial bipeds (Gatesy and Middleton, 1997), with some exceptions, with the tail and hind limbs anatomically linked into a single locomotor module. Conversely, birds have three locomotor modules; the pelvic, caudal and pectoral modules. The former two are decoupled …show more content…
Conversely, bipedalism in non-avian theropods entails rotation of the pelvic limb and power input from large tail-based muscles; in particular, the caudofemoralis longus (CFL), which is attached to the fourth trochanter (a diagnostic feature of the majority of archosaurs, which maniraptorans and birds lack completely). This form of locomotion is often characterised as “hip-driven” and is seen in today’s crocodiles, with the caudofemoralis longus, attached on the fourth trochanter, serving as an important locomotor muscle. This is likely to be the mechanism of locomotion that the primitive archosaurs used, since the majority of limbed reptiles locomote in a similar manner. In birds, the caudofemoralis longus is either a very small muscle (as shown in our results, in which the caudofemoralis longus had the lowest mean muscle mass), or has disappeared …show more content…
This is supported by the fossil record, which shows gradual changes over time between the two locomotory styles, with more derived theropods carrying out a more knee-driven locomotory style; as the caudofemoralis longus reduced in theropod dinosaurs, they gradually transitioned from the ancestral mechanism to the knee-driven locomotion. Furthermore, the change in the centre of movement led to a change in the limb orientation; with the limbs of derived theropods becoming more crouched over time, as opposed to the upright limbs of basal
Ceratopsians and Pachycephalosaurs Around 144 million years ago, began the emergence of the Ornithischian dinosaurs during the Cretaceous period and diversified into North America and Asia. Ornithischians were classified as having a hip structure similar to that of birds, although they are not the descendants of birds. Marginocephalians, meaning "fringed heads" are a group of Ornithischians that have a distinctive skull structure, consisting of a slight shelf or bony frill on the back of the skull, a unique palate, and a short hip structure. These herbivores include two major groups: the Ceratopsians and the Pachcephalosaurians. These plant-eaters include the Ceratopsians, horned dinosaurs such as the Triceratops, Styrachosaurus, Pentaceratops, and the Protoceratops.
Paul, Gregory S. (2002). "Looking for the True Bird Ancestor". Dinosaurs of the Air: The Evolution and Loss of Flight in Dinosaurs and Birds. Baltimore: Johns Hopkins University Press. pp. 171–224. ISBN 0-8018-6763-0.
...nted muscles. The quadrupling of genes led to bigger animals such as elephants. The largest member of the chordate phylum that ever walked on Earth was dinosaurs. The closest animal relative to humans is great apes. Great apes can think, feel, nurture own kind, pass on social skills, mimic, and remember just like humans do. Human intelligence is greater than anything on Earth! This video enhanced my understanding on Chordates because it explains how some chordates are or are not vertebras and it showed how land animals evolved from fish. I always like to see different videos on how species originated, especially humans.
The results from the experiments supported the hypothesis that the batoid pelvic girdle shape correlated with the type of locomotion. They found that the form of locomotion utilized by the batoid had a greater determining factor on the shape of the pelvic girdle compared to the phylogeny. An important discovery of this experiment showed that the shape of the pelvic girdle of a batoid can be used to predict the swimming and punting mode, and the order to which the vertebrate
Dinosaurs are often compared to and resemble modern day reptiles. Scientists will study how these modern day reptiles behave, look, act, and move to draw conclusions on how the dinosaurs would behave, look, act, and move. They also look at the intern make-up of the modern reptiles to predict how the dinosaurs internal make up would be. However, a recent discovery in South Dakota is stirring up some controversy (Hesman). While Mike Hammer was walking around a ranch in South Dakota he stumbled across a “big-eyed” dinosaur that he now refers to as Willo. The thing that caught his eye was the chest cavity of the dinosaur, upon further investigation he found a rock that was preserved in the curve of the dinosaur’s ribs, he was convinced that this rock was once a heart. Hammer then went on to take the dinosaur fossil in for a medical X-ray scan, this X-ray showed evidence that could change how we think about dinosaurs.
If you were to live during the tertiary period, this would be one of the things you would often see. All of the mammals that existed during that time period were terrestrial. They all were land dwelling mammals. Before J. G. M. Thewissen and colleagues’ discovery in Pakistan, many scientists believed, since the constant new discoveries twenty years ago, in what the numerous fossils from North America, Pakistan, and Egypt have revealed, “…these early cetaceans had mobile elbows and external hind limbs with articulated knees. However, they were fully aquatic, except for Ambulocetus, which was amphibious-much like sea lions” (Walking with Whales).
In an article entitled Tyrannosaurus was not a fast runner, those experts, John R. Hutchison and Mariano Garcia provide us with a detailed account of a recent study they did. Their study is described in an article entitled Biomechanics: Walking with tyrannosaurs by Andrew A. Biewener. Biewener states that Hutchinson and Garcia, “introduce a new biomechanical approach,” to the question of dinosaur movement and provide an, “a...
2. Fossils of its pelvis, legs, and feet indicate that it was bipedal, like humans.
Bipedalism had many advantages, but it also had many disadvantages and provided dangers to early hominids. Some of these disadvantages included i...
The Hall of Saurischian Dinosaurs and the Hall of Ornithischian Dinosaurs are more examples of evolution within vertebrates. However, these two halls do not have much in common with our line of ancestry except for the fact that a backbone and brain case are present; any other things in common with our lineage are but minor details. That is why the AMNH has another hall called Mammals and Extinct Relatives.
Retrieved 14 May 2014, from http://www.teachpe.com/a_level_analysis/movement_analysis_webpage.html. Thibodeau, G., & Patton, K. (1993). "The Species of the World. " Chapter ten: Anatomy of the muscular system. In Anatomy and Physiology (1st ed., p. 252).
Several models have been proposed to explain why might Archaeopteryx or its decedents develop the ability to fly. The “pouncing proavis” or “trees-down” model was proposed by J.P. Garner and colleagues in 1999. They theorize that birds evolved to the ability to fly by first living in trees and then gliding down to ambush prey. Natural selection favoured individuals that could glide the furthest to catch prey and eventually led to the origin of flight. Garner and colleagues (1999) believed that this theory explained three aspects of early flight: the model matches observed secession in flight evolution based on fossil records, it predicts a primitive bird-like animal had few adaptions to flapping but very complex aerodynamic feathers, and it explains the origin of rachis in feathers.
The debate of whether dinosaurs were cold blooded or warm blooded has been ongoing since the beginning of the century. At the turn of the century scientists believed that dinosaurs had long limbs and were fairly slim, supporting the idea of a cold blooded reptile. Recently, however, the bone structure, number or predators to prey, and limb position have suggested a warm blooded species. In addition, the recent discovery of a fossilized dinosaur heart has supported the idea that dinosaurs were a warm blooded species. In this essay, I am going to give supporting evidence of dinosaurs being both warm and cold blooded. I will provide background information on the dinosaur that was discovered and what information it provides scientists.
One of the most important and pivotal physical and biological adaptations that separate humans from other mammals is habitual bipedalism. According to Darwin, as restated by Daniel Lieberman, “It was bipedalism rather than big brains, language, or tool use that first set th...
The fossil record of horses extends back to an odd-toed ungulate mammal belonging to the taxonomic family Equidae, a dog-like ancestor 55 to 42 million years ago in the genus Hyracotherium in North America. Hyracotherium had a primitively little face , four-toed forefeet, three-toed hind feet, an arched back, small brain, and higher hindquarters than forehand. Later genus has increased in body size, brain complexity, the size of cheek teeth, lengthening of the face, and reduction of toe number. However, even though horses got larger over time but these trends are not seen in all of the horse lines. Genus such as Hipparion existed from 23 to 2 million years ago, showed gains in size, But some later genus such as Archeohippus, and Calippus got smaller again (Boundless, 2016),(Encyclopedia of Life,2015), (equineworld.co.uk, 2014), (Molen, M.