I have posted some pictures of a fossil I found in the boulder clay at
Mappleton, south of the MOD ramp. It certainly looks like vertebrate
bone material and has a number of quite significant features. It is
roundish in section, about 9" long but obviously part of something
much bigger. It is slightly curved along the long axis, the top side
has a pronounced crest or ridge that terminates about half way along
(seen in section in one of the photos). The underside is slightly
concave with two small "mounds" in the middle - but these are not very
clear in the pictures. I presume these may represent muscle attachment
points. It is certainly fossil - very heavy - not recent material -it
is solid rock. It also appears to have been hollow originally (and
quite thin walled) and is now infilled with hard matrix that contains
some shelly material.

It was eroding out of the boulder clay at beach level and within a few
feet where some ammonite fragments which I recognise as from Speeton.
In my experience material tends to stay together in the boulder clay
so I would guess that this fossil came from Speeton also. I believe
Iguanodon remains have been found at Speeton hence my speculation of
that genus. As far as I can tell it doesn't resemble any bones from a
marine reptile. As to which bone, I have no idea - possibly rib? ,
humerus? (could the crest be the deltopectoral ridge?) or pelvic
structure?. I am pretty sure the the fossil has enough characteristics
for it to be diagnosed. I guess it needs looking at by a professional.

Anyone got any ideas?