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Found 5 results

  1. A Murder of Tridenticeras

    On Friday my mother and I went to the same rock pile where she found this as of yet unidentified heteromorph ammonite exactly 5 weeks prior. We had been there multiple times since she found it but every trip was a bust because we had surface picked it as much as we could the first time. But within the last few days the pile had been turned up again when part of it was used to level a flat surface to pour a driveway. Because this site is so rich in rare heteromorphs I decided that it would be wise to hunt around it again. It had indeed been rejuvenated and the hunt was an hour well spent! We had only been there a minute or two when I found my first Tridenticeras peramplum ammonite of the day. It was laying amongst the rocks used to level the ground a few feet away from the pile. It is only an external impression but very detailed. The ribs and tubercles are well defined all over the preserved specimen even on the tiny uppermost whorl as clearly shown in P1 - P3. This is the 9th T. peramplum specimen in my collection and the 2nd impression only specimen. It is also the second impression to preserve one of the whorls closest to the apex. It is in association with an inoceramid just above it. FIG 1 - FIG 6, Specimen 1: Total shell height is 29mm, total shell diameter is 15mm. Ruler is in millimeters. FIG 1: T. peramplum is trituberculate with the bottom two tubercles being closer together. FIG 2: FIG 3: This picture shows especially clearly the detail on the uppermost whorl. FIG 4: FIG 5: FIG 6: Continued in next post...
  2. I have been doing more research on my unidentified Middle/Upper Coniacian heteromorph ammonite that I posted pictures and information on here, and with lots of papers and information from Keith Minor I think that I have narrowed it down to two ammonite genera, Neocrioceras and Pseudoxybeloceras. He sent lots of very helpful papers including Kennedy and Cobban's 1991 paper Coniacian ammonite faunas from the United States Western Interior. It includes pictures and information on 3 species of Neocrioceras and one species of Pseudoxybeloceras from the Coniacian Western Interior. Keith also emailed me some information that I will show here. At first I thought that my specimen could be Smedaliceras durhami which is so far known only from the Campanian Burditt Formation of south Texas. That was way out there and Keith didn't even consider that possibility because of how out there that suggestion was. Then I saw pictures on the internet of an Allocrioceras hazzardi specimen from Utah that did look similar to mine. The main problem with that theory is that A. hazzardi doesn't have lateral tubercles, so scratch that. It was after exchanging emails with Keith that I came to my aforementioned conclusion, that my specimen is either of the genera Neocrioceras or Pseudoxybeloceras. After studying Kennedy and Cobban 1991 a bit further it seems to me that Neocrioceras (Schlueterella) sp. most closely resembles my specimen. N. sp. has one set of lateral and ventral tubercles on both sides of the specimen respectively. The tubercles connect groups of 2-3 ribs. Between the tuberculate groups there are up to 6 finer non-tuberculate ribs. At first I said that on my specimen there were 7 non-tuberculate ribs between the tuberculate ones but on closer examination the tuberculate ribs come in groups like N. sp. with one tubercle connecting two ribs. In reality my specimen has 6 non-tuberculate ribs between each tuberculate group consisting of two ribs. The main difference that I notice is that my specimen has much weaker lateral tubercles than N. sp. Interestingly, Neocrioceras is not known from the Austin Chalk but there are a couple Pseudoxybeloceras specimens reported from the Santonian stage of the Austin Chalk in central Texas. The main reason why I don't think my specimen is Pseudoxybeloceras is because the species P. dispar, the only species of this genus reported from the Coniacian Western Interior in Kennedy and Cobban 1991, is quadrituberculate on every rib with no ribs being non-tuberculate. But I will say that I have not seen nor read any detailed descriptions of the Pseudoxybeloceras species found in the Austin Chalk so I still consider it a very possible candidate, though my specimen is considerably older. @Wrangellian, I know that you have experience with this genus from the Santonian. What do you think? In this post I also include 3 pictures of 2 different inoceramid specimens I found along with my heteromorph specimen. I sent Keith these pictures to help pin point my heteromorph's stratigraphic position in the Coniacian. Anyone have any ideas on what species they are? From what I am hearing from Keith my ammonite specimen could be a bit older than the Prionocycloceras gabrielense zone if these inoceramids are in the Magadiceramus subquadratus group. I will update this thread when I receive more information. Here are the edited relevant emails from my exchange with Keith: ______________________________ Keith Minor, February 17. Hi Heteromorph, According to Kennedy et al., Phlycticrioceras douvillei and P. oregonensis are junior synonyms of P. trinodosum. P. trinodosum has been found in several areas around the Cretaceous Tethys Sea. According to Walaszczyk, The Trinodosum Zone is middle Coniacian, which is consistent with the level that you are finding your specimens. Cremnoceramus ranges up into the middle Coniacian. However, I think that the clams that you have are probably Magadiceramus, probably M. subquadratus group. So the heteromorphs are slightly lower than the Prionocycloceras gabrielense's that you are finding, and your Texanitine could actually be Protexanites shoshonense, which would be about the right level. Also, I didn't put two and two together, but that big piece of a heteromorph that you showed me may actually be Neocrioceras, which doesn't have tubercles, or Pseudoxybeloceras, with small tubercles that fade on the body chamber. I hope this helps! Keith ______________________________ Heteromorph, February 22. Here are two websites with the pictures of the alleged Allocrioceras hazzardi specimen that I found pictures of online. The more I look at the pictures the less I think that the specimen is really A. hazzardi. I have never seen another A. hazzardi specimen that looks like it and all the descriptions that I have read on the species don't indicate this kind of variation. I now believe that it was misidentified, but I wonder what you think. http://www.ammonoid.com/coniacian.htm https://www.tonmo.com/threads/heteromorphs.11130/page-4#post-156740 So, do you have an opinion as to what species my specimen is? For me I am having trouble deciding between Pseudoxybeloceras (Pseudoxybeloceras) dispar or Neocrioceras sp. What I do know is that the alleged A. hazzardi specimen from Utah very much resembles mine. Thank you for all your help! ______________________________ Keith Minor, February 22. Hi Heteromorph, I see the images. Yes, that is definitely Allocrioceras hazzardi. It ranges from the Upper Turonian (Prionocyclus hyatti Zone) to the Upper Coniacian (Prionocycloceras gabrielense Zone). I don't know of any Santonian species. Hazzardi is probably the descendant of Allocrioceras annulatum from the Upper Cenomanian. Kennedy also described A. conlini, but I'm not sure that this is a separate species. I attached (as a Google Drive link) Kennedy's review of Eagle Ford ammonites (Texas). You can see that the ribs are all the same size in annulatum, but in hazzardi, the the spine-bearing ribs are bigger, and also hazzardi is a larger species. I double checked to see if Hamites and Anisoceras ranges up into the Coniacian, but they disappear in the Cenomanian (as far as I can tell), so these genera can be ruled out. However, Neocrioceras and Pseudoxybeloceras are genera that need to be considered. I have some papers on these, I think from South Africa. I'll find those when I have time. There's a couple of Pseudoxybeloceras specimens from the Austin Chalk from central Texas (Santonian). Kind regards, Keith Late Cenomanian and Turonian Ammonite faunas from north-east and central Texas ______________________________ P1 - Inoceramid oyster P2 - Same inoceramid oyster showing more clearly the perpendicular ribbing.
  3. On November 27 of this year my mother and I went hunting in a new housing development exposing the Austin Chalk in North Texas. The first and only site that we got to was covered in this rock that has been brought in from somewhere else. It was odd in that it looked like someone had just poured a bunch of it in an empty lot in no particular pattern. It was all next to a man made hole in the ground in the middle of the lot, but I don't see how that could be related. We have seen bags of this matrix in drainage ditches before and had also seen it variously thrown about at different Austin Chalk sites. I had found a few things in it that were intriguing, but for some reason I had largely (and very incorrectly) assumed that there was probably not much that one could find in it, so I never seriously hunted it. But my mother proved me very wrong! When we got to the site and I saw that much of it was covered in this stuff, I was somewhat annoyed since it was covering up some of the Austin Chalk. But we both got out anyways and began hunting. I went off towards the ditch where more of the Austin Chalk was exposed while she was looking around in the foreign matrix. I wasn't having much luck and she was commenting on how she was seeing some layered patterns in the matrix, pictured in F31. I didn't think much of it and kept hunting away from the pile of unknown matrix. Then less than a minute later my mother let out something along the lines of, "Hey! Hey! Hey! What is this?!" When she does that, I know she is not kidding around! So I went over there and saw her pick this up off of the ground. We both immediately knew that it was an echinoid. What made this specimen really special are the facts that this is the largest or at least second largest echinoid that we have ever found, the first echinoid from a formation other than the Austin Chalk, and our first regular echinoid all in one. Its a sad thing that it is so beat up, but then again its not surprising since it was probably hauled in a bag in the back of some guy's pickup for possibly hundreds of miles. Only two tubercles that have not been knocked off are visible, though perhaps there are one or two more buried under the chunk of matrix stuck to the side of the specimen. It is also missing most of its adoral side and most of its apical disc, with bits of the disc still in the depression that is left. Its test is pretty scuffed up in general, but at least most of it is still left and I don't think that it is too beat up to be identifiable. I took pictures of the site while I was there (pictures in F1-F4) and brought home a lot of matrix to experiment with and to photograph later to aide in identifying the formation from which it came. When I got home I consulted @Bill Thompson's book on Texas echinoids and I have been able to narrow this specimen down to the genus Temnocidaris for sure. I am hoping that you guys can help me find out what formation the matrix came from, which would greatly help to narrow down the species possibilities. Out of the four species of Temnocidaris listed in Thompson's book as being reported from Texas only two of them have there tests pictured, T. borachoensis and T. hudspethensis, with the other two species only described from their spines. Now I am not an echinoid expert by an stretch of the imagination, but I am personally leaning towards this being T. borachoensis from the Boracho Formation of Upton county or a nearby county in West Texas. My reasoning is twofold: First, to me its test much more resembles T. borachoensis than T. hudspethensis in two ways. They are that the interabulacrum tubercles are closer together than T. hudspethensis and that its test is a bit more squat than T. hudspethensis, even if it still had its base. Coincidently, just a little over a month ago @KimTexan posted for identification a Temnocidaris specimen from the Edwards Formation of Johnson county that very much resembles mine, though I can't say for sure it is the same species as mine since her specimen is missing much of its aboral side while mine is missing much of its adoral side, making a comparison between them a bit difficult. Second, from what I have seen the matrix most closely resembles the San Martine member of the Boracho Formation. If I want to learn a bit about Texas paleontology that I didn't know before I will usually look up one of @Uncle Siphuncle's Fossil hunting reports. Here is one which contains pictures of a lot of matrix and a few fossils from the Boracho formation, starting with Figure 91. The most striking resemblance I see is that the matrix has a lot of red/orange matrix streaks running through it like mine does. But because I have never hunted in the Boracho Formation other than possibly this brought in matrix, I don't know for sure. I also noticed what appears to be the same layered fossil shown in F31 in Figures 136-138. After seeing this post, I tend to think that it is oyster related material. This matrix is a lot more dense than the Austin Chalk that I am used to, making it noticeably heavier. It bubbles when I put vinegar on it indicating that it is limestone, though perhaps not as vigorously as vinegar on the Austin Chalk. I scraped some matrix with a dentist's pick in the places weakened by vinegar and places I didn't treat with vinegar, and while it did scratch the limestone matrix, the untreated matrix was harder than untreated Austin Chalk. I have tried to see if the sandy red/orange matrix bubbles, but my experiments were inconclusive because the limestone is always nearby, skewing the results. I would assume that it does not bubble on its own. After cleaning the echinoid, a few other fossils, and chunks of matrix, the toothbrush fibers had turned orange indicating that the sandstone it is not that hard, at least when wet. Also the limestone matrix is just packed full of calcite crystals, which is very noticeable in direct sunlight! The specimen its self, excluding any matrix, is 53mm in diameter by 36mm in height, though it would be taller if it still had its base. It appears to me that it is only infilled with the sandstone while there is an actual limestone chunk stuck to the side of it, shown specifically in F12. Notice the red patch on the matrix, a characteristic not unique to this chunk but seen on another chunk of matrix shown in F32. All of the pictures were taken in sunlight, so the color that you see is how it really looks. Thanks for any help in advance. F1-F4. On site photos. F2 F3
  4. I have recently been getting into the world of fossil preparation. The only tools that I have so far are a dental pick given to me by Roger Farish, and a few other picks of about the same tip size that I bought at Home Depot. They are doing well for me now with the kind of basic preparation that I am doing with the Austin Chalk. The problem that I have is trying to clear away the dust and small rock bits while I am preparing the fossil. So far I have been just blowing it away with my mouth, but in the process it is hard not to breath in some dust, which I know is not good for me. I have tried wearing a dust mask and then taking it off momentarily to blow away the debis, but that is annoying to deal with and I usually still breath in dust. I know that many of those on here who prepare fossils use air abrasive systems where the dust is blown away by the exhaust from the front of the pen. I am wondering what I can do with my setup. Compressed air? Vacuum? Any and all ideas are appreciated.
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