EDIT (30/5/2017): The Dinosaur Expeditions centre, where the fossil will be displayed, have offered the following equally likely explanation for this footprint-like impression:
"Localised compression fractures, deformation of surface & underlying cancellous bone matches a tridactyl print. Parsimonious explanation." (via this tweet).
A dinosaur footprint has been found embedded on the surface of dinosaur backbone, according to the Isle of Wight County Press.
"Localised compression fractures, deformation of surface & underlying cancellous bone matches a tridactyl print. Parsimonious explanation." (via this tweet).
A dinosaur footprint has been found embedded on the surface of dinosaur backbone, according to the Isle of Wight County Press.
The sauropod dinosaur backbone (vertebra) with what appears to be a footprint pressed right in to the centrum (outlined in red). Image from the Isle of Wight County Press.
It seems extremely improbable, but it isn't impossible. In taphonomy, we always consider the effect of trampling on decomposing bodies: if a body is laying near a lake or other water source, then it is likely that many other animals will be passing through that area and accidentally walk over the body. This can crush and scatter bone, but I've never heard of a foot landing precisely on the body (centrum) of a vertebrae and leaving a footprint behind.
In this case, it seems a small theropod (meat-eating) dinosaur has walked over the top of a decaying sauropod (long-necked) dinosaur carcass, at one point stepping precisely on a vertebra.
From what I can see in the photograph, it appears that there is still some mudstone covering the centrum. I thought perhaps the footprint was in the mud layer covering the bone, but the articles I've read suggest that the theropod foot crushed the bone. The rest of the vertebrae has been preserved quite well. This sauropod must have been decayed enough so that the vertebrae had disarticulated and lay centrum-side up, with the centrum and bone marrow softening and rotting while the rest of the bone remained fairly solid before it was trodden on. Again, improbable, but not outside the realm of possibility.
I also considered whether the footprint was pressed into a muddy bank first, and the bone later laid on top of it, 'sticking' the two together. However for this to be the case, the footprint on the bone would have to be a cast of the original print and would appear raised off the surface of the bone, rather than sunken in like a mold.
I look forward to seeing a thorough examination of this specimen, as if this impression is a theropod footprint, it shows direct evidence of this small theropod and large sauropod co-existing in the same part of the ancient Wealden landscape.
In this case, it seems a small theropod (meat-eating) dinosaur has walked over the top of a decaying sauropod (long-necked) dinosaur carcass, at one point stepping precisely on a vertebra.
From what I can see in the photograph, it appears that there is still some mudstone covering the centrum. I thought perhaps the footprint was in the mud layer covering the bone, but the articles I've read suggest that the theropod foot crushed the bone. The rest of the vertebrae has been preserved quite well. This sauropod must have been decayed enough so that the vertebrae had disarticulated and lay centrum-side up, with the centrum and bone marrow softening and rotting while the rest of the bone remained fairly solid before it was trodden on. Again, improbable, but not outside the realm of possibility.
I also considered whether the footprint was pressed into a muddy bank first, and the bone later laid on top of it, 'sticking' the two together. However for this to be the case, the footprint on the bone would have to be a cast of the original print and would appear raised off the surface of the bone, rather than sunken in like a mold.
I look forward to seeing a thorough examination of this specimen, as if this impression is a theropod footprint, it shows direct evidence of this small theropod and large sauropod co-existing in the same part of the ancient Wealden landscape.
The entire sauropod vertebra. You can faintly see the footprint shape on the centrum.
Image from the Isle of Wight County Press.
Image from the Isle of Wight County Press.
References
County Press reporter, 2017. "Unprecedented dinosaur discovery made on the Isle of Wight". Isle of Wight County Press. URL: http://www.iwcp.co.uk/news/news/unprecedented-dinosaur-discovery-made-on-the-isle-of-wight-315188.aspx Accessed Sunday 28th May, 2017.
Dinosaur Expeditions (DinosaurInfo). "Localised compression fractures, deformation of surface & underlying cancellous bone matches a tridactyl print. Parsimonious explanation." 29th May 2017, 5:48pm. Tweet.
County Press reporter, 2017. "Unprecedented dinosaur discovery made on the Isle of Wight". Isle of Wight County Press. URL: http://www.iwcp.co.uk/news/news/unprecedented-dinosaur-discovery-made-on-the-isle-of-wight-315188.aspx Accessed Sunday 28th May, 2017.
Dinosaur Expeditions (DinosaurInfo). "Localised compression fractures, deformation of surface & underlying cancellous bone matches a tridactyl print. Parsimonious explanation." 29th May 2017, 5:48pm. Tweet.
