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Went hunting in the Arundel formation an east coast US early cretaceous terrestrial/lacustrine facies and found this odd rock. My first thought was that it was a broken piece of machinery . It is not magnetic, though it is heavy for its size ,a flat bottomed triangular piece 2 cm on its longest axis. I have shown it to a number of people, one suggested lungfish tooth plate and several just felt that it seems to be ironstone and therefore cannt be a fossil. Lungfish toothplates have been (rarely) found in this formation. I would appreciate any help in understanding this. The last photo is a picture of my rock on a photo of a palatal lungfish toothplate.

I found a nice exposure of the Arundel Clay recently. For those who don't know, the Arundel is an early Cretaceous unit known for it's dinosaur, plant, and other fossils, and is the only source of early Cretaceous dinosaurs east of the Mississippi River. I've been hitting the sites a fair bit over the past several weeks, finding a lot of really nice lignified and fossil wood and even some leaf imprints, amber, and what might be the imprint of a piece of bone or shell in a lump of clay. However, I recently found this specimen which has perplexed me. To start off; I'm fairly certain these are fossils. I just can't tell what of. They look similar to petrified wood, however I have not seen such fossilization of the other wood fossils from this site (or elsewhere from this unit). It appears to be silicified/agatized. I know dinosaur remains have been claimed to have been found near this site, including pieces of a leg bone that the finder originally mistook for wood (I can't verify if that's true or not, however). The Arundel is also well known as a dinosaur bearing unit, however I haven't heard/seen of agatized remains from it. After a quick search online it is possible, and my specimen at least bears a superficial resemblance to pieces of agatized bone from the Morrison Formation. Unfortunately my piece is too weathered to really see any features typical of bone in cross section, like a "sponge texture" or "webbing." Along the edge of the piece there is a bumpy, almost crystalline (for lack of a better word) texture, but nothing specific. I've included an image of a typical fossil wood specimen from this locality to compare this piece with the fossil wood.

two unknowns that i would like help with from early cretaceous arundel formation in maryland one large one small. The large piece is ironstone that looks like it formed around a series of reeds or stems. The photo shows it sitting on a 8 by 10 inch notepad. It itself is approximately 12 by 4 inches. The smaller piece is a thin section of ironstone with a oval section of stone/tooth/bone 1.5 cm by 1 cm with a dense cortex and a web like internal structure . ID, Ideas and suggestions are welcome

Dinosaur Park in Laurel, MD, is a tiny, 7.5-acre tract of county parkland surrounded by a business park in bustling, suburban Maryland. Nevertheless, it is the most prolific dinosaur and plant site east of the Mississippi. The first fossils there were found in the 18th century by slaves in the siderite (bog iron ore) mine that was there at the time. It wasn’t until 1858 that the bones turning up in the mine were identified as dinosaur remains. The bones found that year were from what would have been, if they a had done all the paperwork, the second dinosaur identified in the US, Astrodon johnstoni, which is now Maryland’s State Dinosaur[1] . Since then dinosaurs, turtles, small mammals, crocodilians, gastropods, clams, and tons of fossil plant material have been found there, all of it now at the Smithsonian. The site is part of the Arundel Formation, dating to the Lower Cretaceous, 115 mya, when the place was an oxbow lake. Tributaries were strong enough to wash dino bones into the lake. The fossils there are disarticulated wash-out. Whole skeletons are not generally found or expected here. The exposed hillside consists of a mix of fine grey soil, siderite bog iron and lignite (coalified fossil wood the consistency of charcoal). The lignite and siderite form a thin, dense gravel layer. The challenge for visitors and paleontology volunteers alike is to find the pale blue bones and shiny teeth in the cacophony of black and orange. Collection is done almost exclusively by surface scanning. If something large turns up by way of erosion, then they cordon it off and dig it out. Anything other than the wood is documented with the finder’s name and sent to the Smithsonian. Visitors may keep one palm-sized piece of fossil wood if they like. My husband and I met a friend and her two daughters there today. It was cold, but sunny. There were harsh shadows on the ground, which are supposed to make it easier to pick out shiny teeth. I find the contrast too harsh to see details. The park is open from noon to 4 every other Saturday. We got there close to 1 and spent a couple hours there, despite the chill in the air. I didn’t expect to find any exciting fauna. That’s usually our daughter’s job, and she was at work. I was engrossed in the lignite and the siderite plant impressions, hoping maybe to find a seed cone or two for their collection. Apparently, a handful in a day is not unusual there. I had no luck on either score. I did find a nice plant impression in the siderite. Looks like tree bark. I asked if that could be the one I took home. The volunteer looked at me sternly and asked, "Do you now what it is?" "Tree bark impression in siderite, but I don't know from which tree." “What do you do for a living?” “Artist.” “What do you do that will prove to me that this will be used for educational or scientific purposes?” I told him about my fossil blog and the homeschool paleontology series I just ran at my local library. He was convinced. Now I have it at home, but I may offer it to the Delaware Museum of Natural History, where I volunteer. Each of the girls also found something nice, albeit smaller, to bring home. Unsurprisingly, most of the other kids were disappointed because they didn’t find dinosaur teeth. There was a list at the registration table of maybe a dozen interesting things found today. As far as I know, no one found anything interesting while we were there. Some days go like that, but I was not disappointed. It was a good afternoon to see someplace new. [1] Maryland has both a State Dinosaur and a State Fossil. The State Fossil is a gastropod, Ecphora gardenera.

Found this little item in my rock bar that has me stumped. Has too much form to be a "concretion", but not enough to try to get a bone ID. It came from a Maryland Creek in the Arundel "formation" Potomac "group".