Not Quite Sure Here Two Shots

[Nenando]

Not quite sure what this one is, found North of Dallas in what I beleive is the Grayson Formation from the Cretaceous period. Any help on this one fellow fossil hunters?

[FossilDAWG]

I'm thinking it's a fragment of a Turrilites or Mariella, which are heteromorph ammonites.

Don

[Uncle Siphuncle]

looks like a fragment of the heteromorphic ammonite mariella brazoensis, an index fossil of the grayson and overlying mainstreet formations. if this came from massive, hard limestone, its mainstreet. if from nodular limestone bedded in greenish gray clay, its grayson. i suspect the latter. a complete specimen can have 4-5 whorls in a tapered helix, ornamented with rows of tubercles all the way up, very attractive! tip: in the grayson, you'll find more complete specimens by focusing in the limestone nodules for smaller specimens 2-4 inches tall, rather than whole adult specimens free of matrix. the limestone doesn't weather out in big blocks, making it hard to find unbroken adult specimens. my biggest adults are from the mainstreet and its equivalents around the state, as the harder lithology tends to result in large, unbroken beds that lend to better preservation of larger specimens. getting them out however can be complicated at times. happy huntin'!

[BobWill]

Thanks for the clarification, Dan. Years ago someone told me these were Turrilites sp. Now I've told other people the same thing. That'll teach me to take a closer look when I look stuff up

I see where several species of Mariella have been found in the Grayson of Denton (he's at R. Ranch). M. worthensis, M. graysonensis & M. rhacioformis.

The last two show to have a band between the double rows of tubercles like all of mine but then so does M. brazoensis, so Nenando, you may have to clean some of the matrix to tell which species...or just label them Mariella sp.

Edited September 18, 2013 by BobWill

[Uncle Siphuncle]

sp. works for me. in fact, the more i learn, the more often i only attempt to name genus, rather than pidgeonhole a specimen into a species i'm unsure of, for whatever reason (poor preservation, ensconcing matrix, overdescription, poor understanding of subtle diagnostic differences, laziness regarding retrieval of description, etc).

if memory serves, older references may have called this genus turrilites, then when i got in the game they were called plesioturrilites, then i was corrected to mariella, probably by the now defunct cretaceousfossils.com site, as i tend to trust keith minor's ammonite acumen more so than my own.

Edited September 18, 2013 by danwoehr

[BobWill]

The Houston book by HGMS shows M. brazoensis going though all three genus names but still lists three species of Turrilites so maybe we can't count them out yet. None of them found in Grayson or Mainstreet formations though. Of course this is information from 1994 so it could have all changed to Spiralylooking notasnaili by now

[Uncle Siphuncle]

i recall some turrilites from the upper K of TX, but since i've not encountered them afield, i don't know much about them.

[Nenando]

Wow you guys are awesome. I appreciate the responses as I learn a little bit more everyday I can see the reasoning behind the id now! I was just happy to find something different for a change. I was surprised to not find any shark teeth at all though. I'm on the hunt for shark teeth and trilobites next to add to my many ammonites (crowned myself king o'the broken ammonites recently lol)

[sward]

I would agree on id as turrilite / mariella (whatever they're called these days).

I've found many similar examples on the hillside I used to hunt in the Dallas/Ft. Worth area, which was Grayson formation. On this hillside, there was a thicker layer of "crumbly" limestone near the top of the hill. The more complete specimens I recovered came from this thicker, crumbly layer of limestone. Further downhill in the clay area, I would find pieces very similar to your specimen. Note the "crumbly" limestone layer and the clay in the lower right corner.

looks like a fragment of the heteromorphic ammonite mariella brazoensis, an index fossil of the grayson and overlying mainstreet formations. if this came from massive, hard limestone, its mainstreet. if from nodular limestone bedded in greenish gray clay, its grayson.

As Dan mentioned, if the area you're hunting has loose "chunks" of limestone in clay, it's probably the Grayson formation. If this is the case, keep an eye out for the shark teeth you're looking for. They're probably there. I found many shark teeth on this hillside. You may need to get down on your hands and knees and search for them.

Good luck and keep us posted.

Edited September 19, 2013 by sward