One definition of Astropaleontology (or Astropaleobiology) is by Sherry L. Cady (Portland State University, USA), Malcolm R. Walter (Macquarie University, Australia) and David J. Des Marais (NASA Ames Research Center, USA) in their article: Astropaleobiology in the 21st Century .
The finding of objects resembling animal fossils in images of Mars rovers is a difficult thing. It is unbelievable, unexpected and even mind shaking discovery. Most scientists do not want to discuss about them and also NASA has been mostly silent about them or completely denied their existence. However off the record there has been discussions where these fossils are not completely ruled out. One good almost 'off the record' interview of John Grotzinger and Cristopher McKay by NBC News is James Oberg 2004: Avoiding the 'F Word' on Mars. . This is from year 2004 when Opportunity and Spirit had been in Mars only two months. In this interview McKay takes up the possible faster pathway for multicellular life on Mars. And in this NASA July 2014 publication we see a change in the attitude: D.J. Des Marais,NASA Ames Research Center 2014: Concepts Of Life In The Contexts Of Mars.
I think it is a mistake to ignore the fossils in Curiosity images. They can be the strongest proof for life on Mars. And they are extremely interesting to study. It is incredible to see that if life on Earth and Mars are based on same DNA, that the evolution process has had same kind of tracks on both planets, producing same kind of creatures. This has also philosophical consequences concerning what kind of life there may be in exoplanets in our Milky Way galaxy, especially if we assume that DNA molecule is the basis of life everywhere in the Universe. For researchers who have approached the extraterrestrial life from theoretical point of view, based on current knowledge of biochemistry and probabilities, it is difficult to accept these observations of fossils of complex multicellular life. For kids and common people the visual identification of these objects and accepting them is easy and strait forward.
Instead of ignoring and hiding the fossils I now do the opposite. I try to describe and analyze the fossil bones of John Klein images in Sol 173 and 186 in more detail. The fossil in Sol-109 image was one complete creature with all pieces in logical places( description in next chapter). But the bones in John Klein site are scattered around and looks like they do not directly fit together.
In figure below are the bones of John Klein site in images from A to L. The first 2 rows from A to G, I consider to be clearly bones. The last row from H to L are more unclear, with L being the most unclear. It may be that the bones here are not from one animal, but instead bones from several species.It may be that if we could dig the ground here we would find more bones fitting together.
The bone A has a complex structure, and for me it is the most convincing object to interpret as a fossil bone. It has such a complex structure that I cannot imagine how non-biological process could create this kind of structure to a stone. There is images A-1 and A-2 of this object, with different direction of Sun light.
The bone B (B-1, B-2 and B-3) could be part of a head. Does it have 2 eye holes? Note that in figure B-1 and B-2, left side there is a spiral shaped piece, which looks like it has dropped off from the skull piece. A horn? For what does a sea animal need a spiral shaped horn? In Earth some land animals have spiral shaped horns. Also observe that the surface of this B object has aligned lines from up to down. This is the only object having this kind of aligned surface lines among several thousands of rover images which I have gone through. I get the impression that this piece is not only the bone but maybe it has even the surface skin as fossilized. The B object is also very symmetric.
The C bone has hollow channel inside as the bones of Earth creatures have (bone marrow). The C bone is also very symmetric. It resembles a piece of backbone. Does bone C have two aligned scratches on its surface ? In Earth fossils aligned scratches on a bone can be interpreted so that the animal has been killed by a predator. And in that kind of cases the bones of the eaten creature may be scattered around (See Scientific American, Summer 2014 Special Issue Dinosaurs!, article by Raymond R.Rogers, David D.Crause: A 70-milloin Year-old Murder Mystery.).
The D-1 D-2 bone is also very symmetric. And in middle of it there is structure. Hollow bone marrow filled with debris ? The bone E is also symmetric, but looks like erosion has caused some destruction to it. The bone F has very interesting symmetric structure with large thin surface area on the right side.
The object G is such that if I would see this alone I would not recognize it as a bone. But because it is very close to other clear bones, and it has same color, it is easy to state that it is a bone. Note that in bone G, upper part there may be a white fungi-like object growing (at start phase ?) as we saw in beginning of this page,sol-173 white object.The object H has symmetry axis, but is not so clear.
The objects I, J and K are close to clear bones and color is same. The object L has a symmetry axis, but I consider this as most unclear.
In the first paragraph of this chapter I mentioned that it is even mind shaking to find fossils on Mars. The reason is: We see that Mars, once beautiful Earth like planet full of life has lost everything. Question arises: Will this happen to Earth? I handle this issue more in Appendix for Fermi paradox.
Description of the creature A in Sol-109 images. The A1 is the skull piece. It has a clear symmetry plane. There is eye holes, and at bottom of the holes there is small holes. Channels from eye to brains as Earth creatures have? The pieces from A2 to A7 are neck bones (cervical vertebrae). They are aligned and have a symmetry plane, which is especially clear in A2-A3 bone. The A5 bone seems to be turned into sideways. The formations A8 and A9 may belong to this creature, and if so may relate to food collection. The A10 and A11 pieces are the torso of the creature, also showing symmetry plane, which is clearer at A10 position. If A12 is part of this creature it could be a limb. The object C1 is more unclear. It is close to creature A. The C1 could be same kind of creature than A, but seen from behind.
The D creature has mainly the skull piece left. This creature is of different species than creature A. The D1 and D2 are eyeholes. The holes D3 and D4 are in the position where Earth creatures have holes related to breathing. The D5 piece is interesting arch going upwards in the face. The D7 and D8 look like arch shaped bones close to this creature.
The creature E may be of same species as creature D. The skull piece E is heavily eroded. Interestingly there seem to be the white material, which we have seen before, at the bottom of eye holes. Or alternatively do we see background objects trough the holes?
When images of Sol-109 creature A came to archive, then wild rumors started to spread in internet about it. When NASA observed it, NASA removed the images of creature A from the archive. But because the images were already circulating in web NASA decided to put the Sol 109 images back to archive. Do all Curiosity and Opportunity images go now to archive without pre censorship? There are a lot of gaps in rover image archives.
For this case we would really need an expert on paleontology, researcher of fossils. The image below is very sharp with a lot of details. A1 Head. Compare this to images of earth fossil heads. A2 and A3 Neck. A4 Torso. Note that it easy to set a symmetry plane for this A4 part. There is another small object B in this image. B1 Head. B2 torso. This fossil is just few meters from the first Sol 186 fossil case presented above.