Not so. There are marsupials in the Americas.
Lack of evidence is not evidence of lack.
What alleged evolutionary advantage would placental mammals have that would allow them to edge out marsupials? And if that was the case, why the success of marsupials in succeeding in some places and not others?
The fossil record is clear that during the age of the dinosaurs there were only small and mostly marsupial mammals.
Then after the dinosaurs there was an expansion of placental mammalian species that edged out marsupials everywhere except Australia where none made it across the ocean.
What “alleged” advantage could there be for an animal to directly feed blood and nutrients through a direct connection in the womb? For a person with “mom” in their name you sure drew a blank on that one!
"The striking superficial resemblance between the bones of the theropod dinosaurs (the so-called "bird-like" dinosaurs) and Archaeopteryx (one of the most ancient birds - which lived roughly 150 millions years ago) has led scientists to hypothesize that birds are descendants of these dinosaurs. The bones of the wing of Archaeopteryx look very much like the bones of the theropod dinosaur, Deinonychus. Indeed, the resemblance is so striking that it convinced a very large percentage of the scientific community that birds are descended from the theropod dinosaurs."
"This "Birds are Dinosaurs" theory has become one of the dominant theories of evolution, since its introduction 20 years ago by John Ostrom. The theory is in real trouble now, since a recent study has demonstrated that the bones that make up the wings and feet of birds and the theropod dinosaurs are not derived from the same digits.1"
"What does it matter if birds are descended from theropod dinosaurs? If birds are not descended from theropods, they are not descended from any other known species. Here is a quote from the University of California, Berkeley website:
"The opponents of the theropod hypothesis refuse to propose an alternative hypothesis that is falsifiable. This is probably because there are no other suitable candidates for avian ancestors".2
This is quite an admission, and demonstrates the dogmatism of Darwinism. The paradigm takes precedence over the data, since falsification of descent of birds from theropods would falsify all of evolutionary theory."
The First Study
The wings of birds develop from digits II, and III, and IVThe paleontological evidence for the derivation of the wings and feet of birds is completely lacking, since there is no known predecessor of Archaeopteryx. Therefore, the fossil record cannot answer this question. However an ingenious idea by Alan Feduccia (an expert in the study of bird evolution) led to the study of the embryology of reptiles and birds to determine from which digits the wings and feet of birds are derived. The authors of the study showed that during the development of the hand (or wing) of the bird, there was a transient appearance of digit V, which did not occur in the alligator and turtle, which develop all five digits. These results clearly indicate that the bird's wing is derived from digits II, III, and IV.
The Second Study4-5
BackgroundThe lungs of birds, mammals, and reptiles are vastly different in terms of morphology and function. The lungs of mammals and birds are far more efficient than those of reptiles, which allows for prolonged periods of intensive physical activity. The lungs of mammals consists of millions of alveoli, which are highly vascularized air sacs. The degree of vascularization (the capillary blood supply surrounding the alveoli) and the large surface area allow for efficient exchange of oxygen and carbon dioxide, which allow for mammals' high metabolic rate. The lungs of reptiles are termed "septate," consisting of the equivalent of a large single alveolus divided by vascularized ingrowths, or septae. The bellows-like septate lung of the reptile is poorly vascularized, which prohibits endothermic ("warm-blooded") metabolism. The avian (bird) lung is also a septate lung, but consists of a series of extensive, highly vascularized air sacs, which extend into both the thoracic (chest) and abdominal cavities.
Evidence 1: The structure of the pelvis and ribs of the theropod dinosaurs is incompatible with the breathing apparatus of Archaeopteryx or modern birds
Evidence 2: The structure of the lungs of the theropod dinosaurs is indistinguishable from that of modern reptiles
According to an article by Alan Feduccia:
"Despite the popularity of the dinosaurian origin of birds, many ornithologists and physiologists, in particular, have hadtremendous difficulty with the theory (8, 10, 11) becauseof a huge and growing body of contrary evidence and the fact thata ground-up origin of avian flight is considered a near biophysicalimpossibility (12). Aside from criticism concerning the cursorialorigin of avian flight, there are problems related to the geologic,temporal occurrence of putative dinosaurian ancestors, which occursome 30 to 80 million years after the appearance of the earliestknown bird Archaeopteryx, and these forms become more and moresuperficially birdlike as one approaches the latest Cretaceous.There is also the fact that virtually all of the anatomical featuresused to ally birds and dinosaurs have beendisputed."9 [LINK: GodandScience]