Over the last few decades there have been many discoveries of mammals dating to the Cretaceous and Jurassic periods, and partly in the Mesozoic age. They have based this belief on the Jurassic mammals teeth. The mammals or animals from this Mesozoic age, were very small in size, similar to that of a chipmunk.
Evolutionists thought that because these mammals have been so old, they must have had time to evolve from many different directions of time. Later they thought that their state of evolving must have occurred in the early Triassic, or even the Permian. There has been some recent discoveries of Jurassic and early Cretaceous types of mammals that had been considered just a sample that is coming in the still discoveries of the Mesozoic age. But this has also brought up question in evolutionists, that these mammals must have been very complex to live in the same time as the dinosaurs, and could evolution really have been in the making of these types of mammals. 
Paleontologists recently found a beaver-like mammal from the middle Jurassic in the Jiulongshan Formation of Northeast China. It was given the name Castorocauda lutrasimilis meaning it has a tail like a beaver and is similar to an otter (castor = beaver, cauda = tail, lutra = otter, similis=similar). They had many similarities with modern mammals, but was placed in the taxonomic class Synapsida (rather than mammalia) because of evolutionary paradigms which prevents it from being identified as a true mammal given the period in which it was found. It is instead officially known as a mammaliaform or a basal mammal. It was further placed in the taxonomic order Docodonta because of their relatively sophisticated set of molars.
Castorocauda lutrasimills was a well preserved fossil dated at 164 millions years old, and was found with fur still on its body. The fossil also had it’s middle ear intact, and well preserved teeth (incisors, canines, premolars, and molars). The finding pushed the history of aquatic mammals back a hundred million years. Up until now the oldest known mammal was the Eomaia scansoria, age is about 125 million years old. 
Young earth creation scientist, Dr. Kurt Wise has commented on the implications of this find. He defines the water-proofing hair, vertebrae designed for swimming, a broad tail, and webbed hind feet as evidence of divine design. Wise says that finding a well-designed mammal "among the dinosaurs is not a great surprise to creationists." And he also says that this finding is a challenge for evolution theory. As proof, he offers the fact that it has no known living descendants, thus evolutionists must believe that features, a finding of a beaver -like tail and others, developed on two different creatures millions of years apart.
This old furry animal, they say is about 200 million years old. They say this animal only weighs about the size of a paper clip. Fossil finders were looking; they say that this animal may include one of your relatives- a distante of distant mammals. This was an animal that was classified as a very new species, of the living mammals, the hadrocodium displays mammal features- a large brain, and detached ear bones. But this mammal is forty million years older then any of the mammals discovered. 
There was a team of U.S and Chinese researchers, the research was lead by Zhe-Xi Lou, he is from the museum of natural history; this museum is classified as “Early Jurassic fossil" as a new species” The fossil was really discovered in 1995, in the rich beds in china. But the fossil was found under a big pile of sediment covering the skull. When all was pulled away and cleaned was different from any other fossil they have found before. The fossil of this Hadrocodiums have been well preserved, they are great examples of mammal features, that have been evolving year by year.
This mammal was discovered, and said to be 165 million years old. Discovered by Chinese and American scientists. The main scientists Zhe-Xi Luo. This mammal had a very diverse set of teeth. Lots of mammals are known by there teeth, they are distinguished by the set of teeth they are given. This discovery opened many doors to suggesting that mammals were much more rapidly in their early evolution than was known, and that they have made more complex dentition.
This animal was a worm and incest feeder. The skeleton is estimated to be about 12 centimeters long. They say that it was about the weight of 20-30 grams. Even though this animal was very small it had strong limbs, and was able to do a type of digging, called “power digging”
The teeth are a much more diverse, this animal can be more specificity classified by its type of teeth and that has helped out more and more scientists. The mammals teeth was meant for more then just cutting, but it also had the ability for grinding. It had a combination of being able shear food and grinds them the way it was made, it was made more vestal, and this helped it stay alive longer in its environment.
The Pseudotribos was discovered in 2004 in the Ningcheng County of Inner Mongolia Region in the country of china, it has been transported to the Institute of Geology, this is a Chinese academy of Geological Science in the heart of Beijing The scientists Zhe-Xi Luo, he is one of the scientists of the Carnegie Museum of Natural History. He said that “the cutter is in front of the grinder” Early mammal is al about their teeth.
Dinosaur eating mammal
Species name (Repenomamus giganticus) There was a recent discovery that scientists had discovered that there was some remains of a dinosaur in a mammal’s stomach. Scientists have come to a conclusion that this is proof that mammals hunted dinosaurs 130 million years ago. But some people have challenged this theory, and they say that there is no way an early mammal could not possibly kill, or attack a dinosaur. Well creationist says that the mammal must be very small to attack and kill dinosaurs. The dinosaur must have been about 5 inches long, not a very big dinosaur. Another mammal fossil was found where the other fossil was found, they say this mammal was one of the biggest mammal fossil of the early year. Its size was said to be the size of a modern dog,
- Dinosaur Fossil Found in Mammal's Stomach Scientists have identified the fossilized remains of a tiny dinosaur in the stomach of a mammal. January 12, 2005
- Main Article: Jurassic
The Jurassic term comes from Jura Mountains on the border of France and Switzerland.  The wealth of fossils in Jurassic sediments of Britain meant that biostratigraphic zonation was more advanced than during other periods. Jurassic period is generally divided into early, middle and late.
The Jurassic period is believed to have occurred prior to the breakup of the supercontinent Pangea.The Jurassic period oceans where far more widespread then they were during the Triassic. The Jurassic sea level is believed to have rose and flooded, some of the portions of the contents. When the epi-continental sea spilled out, the Tethys Proto-Atlantic and spread across Europe. This left rich sediment on the lands after the flooding, and also limestone all over the land. The shallow warm seas where home to many life’s the ocean that had animal life across Russia and into what is now the Arctic Sea before retreating at the end of the period. Much of North America was flooded by wide sea that extended into Utah. The continent-wide embayment was doubled by a Sundance Sea, and was fringed by strips of continental land on three sides. 
Gymnosperm plants/ palm-like Cycadophyta were huge in the Jurassic period. They where called "the Age of Cycads" Some cycads were tall palm-like trees with rough branches marked by leaf scars and pinnate (fern-like) leaf fronds. Other Bennettitales Where another big type of tree. They had short and stubby trunks that held the tree in its position with tree fronds coming out from the top of the tree. Conifers where the most significant amount of trees in that time, they included representatives of the extant (still living) families Araucariaceae, Cephalotaxaceae, Pinaceae, Podocarpaceae, Taxaceae, and Taxodiaceae, Ginkgos. In the Sea there was a large amount of invertebrates sponges, corals, bryozoa, gastropods, bivalves, and ammonoid. All of these flourished in their growth.
Jurassic and Cretaceous lived in a warmer climate then today on. Global records have indicated this climate change. At a global scale evaporates predominated in low latitudes and cools in mid- to high latitudes. These conditions can change rapidly between the equator and the poles. Most dinosaurs that remain are known from low-latitude to regions where plant fossils are generally sparse and evaporate common. Few Dinosaurs remain from mid- to high altitudes. This could change the whole way we thought the dinosaur food change worked, because of the way they where affected by the weather chain.
- Jurassic mammals—more surprisingly diverse by Michael Oard. Journal of Creation. 21(1):7–8, 2007
- Beaver-like mammal from the middle Jurassic of China by Andrew Sibley. Creation Science Movement. September 20 2006.
- Jurassic "Beaver" Found; Rewrites History of Mammals by Nicholas Bakalar. National Geographic News. February 23, 2006
- Swimming with the dinosaurs by Dr. Kurt P. Wise, Answers in Genesis. March 8, 2006
-  by Based on an American Association for the Advancement of Science press release, Jurassic Spark: Early Ancestor of Mammals Found, Friday, June 08, 2001
- Science: Dinosaur count reveals surprisingly few species. Nonscientist 01 December 1990 by ROGER LEWIN
- The JurassicThe Jurassic Period of the Mesozoic Era: 200 to 146 million years ago Schlagintweit (2004)
- Late Jurassic Climates, Vegetation, and Dinosaur Distributions 2004 by The University of Chicago
- The Cretaceous Period - 1 Damsté et al. (2002).
- Early Cretaceous II (Aptian-Albian) Damsté et al. (2002).
- The High Cretaceous: Late Cretaceous I M. Alan Kazlev 2002
- TINY JURASSIC MAMMAL FOUND © 2000 firstname.lastname@example.org
- Jurassic period mammal teeth found; prevailing theories challenged Nicholas Bakalar for National Geographic News February 23, 2006