Jump to content

Leaderboard

  1. Fossildude19

    Fossildude19

    Administrator


    • Informative Content

      132

    • Content count

      19,188


  2. ynot

    ynot

    Regular Members


    • Informative Content

      105

    • Content count

      9,890


  3. piranha

    piranha

    Editing Members


    • Informative Content

      85

    • Content count

      6,459


  4. doushantuo

    doushantuo

    Regular Members


    • Informative Content

      81

    • Content count

      4,366



Popular Content

Showing most informative content since 08/19/2017 in all areas

  1. 9 likes
    PART 2. So there are some adverse effects that I have noticed to using potassium hydroxide. The first is that it can bleach fossils. In one plate, I had a small brachiopod that had a flake put atop it. After about four hours the flake had dissolved, and revealed that the brachiopod underneath had lost its color, going from black to a milky clear color. Another effect is that this reaction can produce a white residue atop some fossils that is almost impossible to wash off. Superficially, it looks like the fossil is bleached, as was the case with a few trilobites I had tried this on, however it seems like it is a salt that is produced as a byproduct of the reaction. I don't really know what causes it to be honest, but there is a way to fix it. Out of curiosity I put some hydrochloric acid on the "bleached" trilobites to see what it would do, and interestingly, it removed the residue. The trilobites went from a flour white to a chocolate brown again. Pictured below is another Pentremites conoideus which has the white residue coating it. Depending on what the sediment contains in terms of siliciclastics or pyrite, there can also be some interesting effects. The plate that had the trilobites I experimented on was actually the counterpart, or underside of a plate that had a crinoid holdfast that grew on the trilobite molts. This plate had a bryozoan growing over the holdfast, and atop of it, a pyrite mat. Like the organics in the shales, the KOH will also oxidize pyrite and any other iron bearing minerals in a rock. Pictured below is the holdfast, showing the deterioration of pyrite evidenced by red/orange staining. The photo isn't the best, but illustrates the point. Also, just to show it off, here is the trilobite plate that attaches to the underside of the holdfast: The last thing I have noticed is that a KOH treatment can discolor sediment. This effect is really inconsistent, in some cases it is clear that the sediment has been oxidized, and will show more red or yellow that presumably can be abraded off. In other specimens however, the effect is the opposite of brightening the sediment, and it will in fact darken the matrix up. This may be due to the removal of a weathered surface, but it is hard to say. I hope this post has helped anyone. Potassium hydroxide can be bought easily off of amazon or other places online. I got a 1Ib container for roughly 20 USD.
  2. 9 likes
    The fossil is coiled not symmetrically circular, which rules out a coral. A worn ammonite impression seems the most likely ID. However this raises the issue that such a fossil is far out of place on a Massachusetts beach. To answer this mystery I think we have to recall that ships from Europe used to arrive loaded with beach rock as ballast, which was dumped when they arrived in port in the US and loaded up with cargo. Such rock was widely used for road construction (producing a cobblestone effect) in Charleston in the 1700s and early 1800s as there was no local source of rock. Elsewhere, such as in Massachusetts where abundant local rock was available for construction, the ballast was simply dumped along the shore. So this fossil may be a part of an ammonite-containing nodule that was loaded as ballast on a ship in an English port, and later dumped on a Massachusetts shore. Don C
  3. 8 likes
    I'm sure many of you are aware of the issue concerning discerning between a croc tooth and a gator tooth. So this is my attempt to answer it, now that I've attained a varied collection. First, I will start with the popular generalizations, then I will list each of my crocodile and gator teeth and assess each one. With said data, I will hopefully deduce the best method for discernment. Though this is not meant to be comprehensive, I hope it can be used as a general guideline for identifying crocodylian teeth. The answer is not as clear-cut as you might surmise... Generalizations: -Croc teeth are more curved; gator teeth are more straight (possibly as a result of eating more fish, whereas gators eat more turtles?). This is why you can see a croc's teeth when its mouth is closed (the teeth curve around the outside of the snout and jaw) and not a gator's. -Gators have two 'seams' (carinae) 180° from each other, whereas crocs either have multiples or none. -croc teeth are more conical and sharp; gator teeth are generally blunt. Observations: Pallimnarchus pollens (crocodile) from the Pleistocene of Australia (images 1-3): -two carinae 180° from each other -sharp/pointy -curved -ovoid base Pallimnarchus pollens (crocodile) from the Pliocene of Australia (images 4-5): -two carinae 180° from each other -sharp/pointy -slightly curved -conical base Goniopholis sp. (crocodile) from Torres Vedras, Jurassic of Portugal (image 6): -multiple striations -sharp/pointy -slightly curved -conical base Alligator mississipiensis (gator) from northern Florida, Pleistocene (images 9-11): -two carinae 180° from each other -blunt (it may have been sharp at one point) -curved -conical base Alligator mississipiensis (gator) from Marion Co., Florida, Pleistocene (images 12-15): -two carinae 180° from each other -sharp/pointy -straight (not including the root) -ovoid base Alligator mississipiensis (gator) from the Pleistocene of Florida (images 16-17): -two carinae 180° from each other -sharp but rotund -straight -ovoid base Alligator mississipiensis (gator) from the Pleistocene of Florida (image 18): -two carinae 180° from each other -sharp/pointy -slightly curved -conical base Alligator mississipiensis (gator) from Bone Valley, Florida, Late Miocene (images 7-8): -two carinae 180° from each other -blunt (from wear, but was likely never sharp/pointy due to the amount of force it was using [blunt teeth would have been better for such force distribution and would have minimized wear over sharp teeth]) -straight -conical base Edit note: I have changed the identification of this tooth to Alligator mississipiensis as a result of reading this paper and deducing that Alligator would be more plausible than Thecachampsa or a posterior Gavialosuchus: https://drive.google.com/file/d/0B1HtUwlDORQ0UXZVRGJncGhwVGc/view Deinosuchus rugosus (alligatoroid/crocodylian) from the Ripley Fm., Bullock County, Alabama, Cretaceous (images 19-21): -two carinae with crenulations 180° from each other; some evidence of 'proto-seams' along the base -sharp but rotund -slightly curved -conical base Deinosuchus rugosus (alligatoroid/crocodylian) from the Ripley Fm., Bullock County, Alabama, Cretaceous (images 22-25): -two carinae with crenulations 180° from each other -sharp but rotund -straight -ovoid base Discussion: While croc teeth may generally be more slender and curved, this is not a sure-fire way to identify a crocodylian tooth as being crocodile. Crocodiles do have blunt/rotund, straight, 'stubby' teeth posteriorly (towards the back of their jaw) and these look just like an Alligator's (unfortunately, I don't have any images of the 'button-looking teeth of a crocodile, but image 16 is one of an Alligator 's). Likewise, young Alligators are known to have sharp, pointy, curved teeth (see image 18; I've seen some even more curved). Carinae/striations seem to vary for crocodiles, ranging from none (I have no such specimen to provide a photo of, unfortunately), to a consistent two, to multiple striations. I would say it's a safe bet to assume a tooth is crocodile if it has no carinae or multiple striations, as this is not seen with Alligators (which always have two carinae). In those cases where a tooth has two carinae, further deduction could be done based on the rate of rarity of each per the location, robustness, and curvature if it isn't small. It is also of note that per the paper above (kindly provided by @Plax), the ratio of height to diameter in Alligator mississipiensis teeth did not exceed 1.6. However, do bear in mind that teeth with two carinae that are small, slender, and curved could be either a crocodile or young gator, just as a robust, straight, 'button'-like tooth with two carinae could be either a posterior crocodile's or Alligator 's. Again, such deductions should be taken into account with the rarity of each per a locality. Most importantly, keep in mind that form determines function -blunt, robust teeth indicate a diet of hard-shelled prey; sharp, pointy teeth indicate a diet of slippery prey. Ask yourself if the form better indicates the lifestyle of a crocodile or Alligator found in your area (get to know your specific species!). Then take the above into account. You should be reasonably able to deduce whether you'll see the owner of your tooth later or in awhile To summarize: 1. If the tooth has no carinae or has multiple 'ridges'/seams (striations), it's crocodile. 2. If the tooth has exactly two carinae 180° apart, is small, sharp/pointy, slender, and curves, it could be a small crocodile tooth or young Alligator's. Use the above tips to help you deduce which it is (curvature, robustness, form, lifestyle, rarity of either per the locale, etc.). If it is rather robust and curves, it may likely be Alligator, given its predominance in localities such as Florida. If it is slender and curves and the locale is known for croc teeth over gator, it is likely crocodile and so on and so forth, for example. If you are within the U.S., measuring the height to diameter ratio could help rule out Alligator if it exceeds 1.6. 3. If the tooth has exactly two carinae 180° apart and is straight and rotund, it could either be an Alligator tooth or posterior crocodile's. Use the above tips to help you deduce which it is (curvature, robustness, form, lifestyle, rarity of either per the locale, etc.). Generally speaking, unless you live outside the U.S., posterior crocodile teeth will be more uncommon, especially small ones. If it is large, rotund, and straight (or only curves slightly if it isn't 'button'-like), it's probably gator unless a crocodile with a diet for hard-shelled prey is common in the area. You can also use the height to diameter ratio for this one as well. 4. If you can't tell from these deductions, it's probably a Crocogator or Allidile tooth
  4. 8 likes
    We have read many posts of members wanting to know the age of a bone found in a river because it looks really old, only to be shot down with the news that it is a modern bone. So I decided to conduct an experiment to see just how long it would take for a bone to take on an aged look enough to look like fossil bone. This past winter, we had some tremendous storms that our shores haven't experienced in a long time which deposited many things upon the beach including a bloated beached whale and many dead cattle along with their bones. As I was walking the beach I came across several cow bones and gathered a few. I took a nice white vertebra and wanted to do the experiment on it. All it took was a small plastic tub filled with water and a handful of dead leaves. The vert was placed in the tub, along with the leaves and water. It was then sealed with the lid, left sit for a month and shabam! An instant fossil. So the purpose of these little test was to prove that it doesn't take very long for tannic acid to do its thing and change the look of modern bone. Hope you enjoyed this project, I did. The last picture has another leg bone showing what the vertebra looked like originally.
  5. 7 likes
    PART 1. Greetings all, it has been quite a while since I've posted here. I recently purchased some potassium hydroxide (KOH) flakes from Amazon for fossil preparation purposes. I was told about this chemical as a substitute as Quaternary-O by my friend Gabe Ward. This stuff is basically a really strong base that works (I think) through oxidizing ogranic compounds in a rock. This makes it particularly effective on shales and siltstones, but not so much with most limestones, especially crystalline varieties. I wanted to write a post about this stuff because it seems like it has the potential to be a cheap alternative to air abrasion or scribing in some cases. Safety: The first thing to know about KOH is that it is a pretty powerful base, meaning this stuff is pretty hydroscopic and reacts readily with water. It is very toxic, and eye-wear and gloves should be worn when handling. Don't allow this stuff to make contact with your skin. I am a bit lax with how I handle it, and have gotten it on my arms on one occasion. You don't feel it at first, but after several minutes you will feel it burn and blisters will develop. It seems to have even burned off some of the hairs off where it made contact. This was pretty minor, seeing as I caught it, all burning and blisters went away about half an hour after washing it, but this should give you an idea of what it can do. The container on my KOH says that it produces fumes. I've noticed no ill effects, but it's something to keep in mind. This is all I wanted to do regarding safety, just give an idea of what this stuff can do. Usage: The potassium hydroxide I purchased came in the form of pellets. I apply it by taking tweezers and placing the flakes on the matrix covering the fossil. When left out, the KOH will react with water in the air and start to dissolve. During this time it reacts with the matrix, and you may depending on the lithology, see some evidence of the reaction during this time. Depending on the reaction speed, I may leave the fossils out for one to eight hours. Here is one example, a set of Pentremites conoideus from the Somerset shale fm. of Kentucky. The photos aren't great, but hopefully illustrate what this stuff can do. These are separate specimens, but the one on the left illustrates a very similar "before" condition, that the one on the right was in. My next reply will address some adverse effects, and some other thoughts.
  6. 7 likes
    The holotype of Anisopyge cooperi Brezinski 1992 Brezinski, D.K. (1992) Permian trilobites from west Texas. Journal of Paleontology, 66(6):924-943 Öpik, A.A. (1967) The Mindyallan Fauna of north-western Queensland. Bureau of Mineral Resources, Geology and Geophysics, Bulletin, 74(1):1-404 PDF TEXT 74(2):1-167 PDF PLATES Öpik, A.A. (1970) Nepeid trilobites of the Middle Cambrian of northern Australia. Bureau of Mineral Resources, Geology and Geophysics, Bulletin, 113:1-47 PDF
  7. 6 likes
    Not ear bones, but I recognize the texture! These are all pieces of ray/skate dermal bucklers.
  8. 6 likes
    SAND-CALCITE CONCRETIONS FROM SALTON, CALIFORNIA. by Henry Windsor Nichols THE SAND SPIKES FROM MOUNT SIGNAL by WILLIAM B. SANBORN
  9. 6 likes
    I have used this technique and it does work in some cases. One thing to be aware of is that you will be using lots of water to wash the specimen. So the matrix better be able to stand up to water. You should not use this technique on Arkona Shale (Fm.) fossils. I wouldn't use it on Silica Shale or Rochester Shale unless you want the specimen free of matrix. Like cleaning a Paraspirifer. Works great on loose specimens but think about it if you are going to try this on matrix specimens. Also, this technique may require many repeats of applying KOH before you start seeing results. I have been applying KOH to one plate of crinoids I have for about a years (once a week). IT is showing results but they have been slow in coming. Why use this technique? NO damage due to abrasion. It is good if you are trying to preserve some fine detail. Joe
  10. 6 likes
    "Microconchids are tiny encrusters (Fig. 1A) that appeared in the Late Ordovician and lasted nearly up to the end of the Middle Jurassic (e.g. Taylor & Vinn 2006; Vinn & Mutvei 2009; Vinn 2010). They possessed calcitic, spirally coiled tubes that made them similar to the Recent polychaete genus Spirorbis (Fig. 1B). Critically, for decades microconchids were treated by palaeontologists and geologists as representatives of spirorbine (Spirorbis or Neomicrorbis= Spirorbula; e.g. Palmer & Fu¨rsich 1981; Palmer & Wilson 1990) polychaetes. However, the investigations of Weedon (1991) and thorough studies (e.g. Taylor & Vinn 2006; Vinn & Taylor 2007; Vinn & Mutvei 2009; Vinn 2010) have definitely shown, on the basis of microstructural observations, that microconchids belonged to the extinct tentaculitoids (Class Tentaculita Boucˇek 1964), and that phylogenetically they are closer to Recent lophophorates such as brachiopods and phoronids. In the past, microconchids occupied many different environments, from marine to brackish and freshwater habitats (see Taylor & Vinn 2006; Vinn 2010). Therefore, their affiliation with polychaetes had sometimes a dramatic effect on palaeoenvironmental interpretations." - as it is stated here
  11. 5 likes
    I'm wondering, if they can't be platycrinitid crinoid columnals, similar to Platycrinites, considering their shape, structure and dimension. picture from
  12. 5 likes
    The first one is a strongly pyritized ammonite sitting on a pyrite concretion. The second one looks geological. I can't see anything obviously fossiliferous about it. It looks like a water worn block composed of various sediments.
  13. 5 likes
    I thought I would share this with everyone. I was thinking about a way to display some of my fossils in a manner that all different views were possible with multiple fossils. I did not want to do it with the expense of riker mounts. Also, riker mounts would not be deep enough to put an echinoid in profile view. Then I thought about what people use for displaying sports memorabilia. Baseball cubes, maybe. Football and basketball cases, too big. So what about hockey puck holders? So I went on Amazon and found 2 hockey puck holders for about 5 bucks. They are 3 by 3 by 1 1/4. I bought them. Then I bought a pack of poly foam from Hobby Lobby, 1 inch thick. I trimmed a piece of foam to fit into one of the holders. In it I put 3 echinoid, Eurhodia rugosa ideali. Showing top, bottom and side profile. Bingo. Works great. I can order a dozen of these for $12.97 including shipping and the foam was $3.80 for two 12 by 12 pieces which will make 32 pieces for the cases. So for $16.77 I get 12 cases. You cannot buy 12 riker mounts for that price. This will work for smaller echinoids, shark teeth, shells, ammonites, and many other items. This is the end result.
  14. 5 likes
    Now here is a summary taken from all the figures in Arambourg 1952 that should be a helpful starting place for ID. What I would like for this thread is to eventually have nice photographs to replace all of the originals from Arambourg. In this image, all teeth are to scale and have their current valid names. There is a scale bar that is 20 mm high. I have sampled examples of important tooth positions to give an idea of tooth variation. Cusps are enlarged. Note that Striatolamia and sometimes Brachycarcharias atlasi have striations (grooves) on the lingual (sometimes called display side) and this can be a helpful feature for ID.
  15. 4 likes
    Hi Coco, It still looks rather typically like a fish from the Romualdo member of the Santana formation, I would suggest it may be the somewhat less common Branerion. Please compare, what do you think? What is really cool about the limestone nodules from this unit (assuming it is from where I think it is) by the way, is that they are - I believe - the youngest known occurrence of Orsten-type exceptional preservation; its to be expected that there are tissues softer than bone and scales, once belonging to this fish, that may have been replaced by solid fluorapatite. Its not unreasonable to expect preservation of muscles, tendons, and perhaps even some organs. Every nodule from this place is a potential treasure trove for science! kind regards, Mark
  16. 4 likes
    Although it has been generally accepted since Jell 1975, that there are three types of trilobite eyes, more recently it has been suggested that there are only two types of eyes; holochroal and schizochroal. The abathochroal eye described only from eodiscid trilobites, is most likely a paedomorphic holochroal eye. text from: Zhang, X-G., & Clarkson, E.N.K. (2012) Phosphatized eodiscoid trilobites from the Cambrian of China. Palaeontographica Abteilung A., 297(1-4):1-121 PDF LINK The eyes of eodiscoids were described as abathochroal by JELL (1975b), who considered them to be distinct from holochroal eyes since the lenses were somewhat separated from one another, along with a summary that the eyes of eodiscoids resemble holochroal eyes in five respects, and there are eight differences from the schizochroal type. Of these, two key features for establishing these eyes as a separate type are the lenses not being in contact with any of the surrounding lenses, and each lens possessing its own corneal membrane. However, with more and more phospatized material being documented, and especially with the more fully detailed morphological examination of the visual surface of the eodiscid Pagetides, our new observations do not support the view that abathochroal eyes are distinct from the other two well-known types. For instance, JELL (1975b) believed that each of the individual lenses carried its own corneal cap, but the fact that the outermost thin layer of the visual surface can flake off, taking with it many lenses together, rather than just a single one, casts doubt on this interpretation. Actually, the internal surfaces of some librigenae with the visual surface attached show that some of the fine lenses are polygonal in outline (Plate 16, Fig. 7), rather than circular as seen from the external surface. This is because these lenses remained in close contact as they grew towards a centre point of the visual system, and this has led to the deformation of the outline of lenses from circular to mostly hexagonal, as well as a few pentagonal and quadrilateral (also see ZHANG & CLARKSON 1990, pl. 2, figs 2-6). Moreover, it is now known that the juveniles of holochroal-eyed trilobites have separated lenses (CLARKSON & ZHANG 1991, CLARKSON & TAYLOR 1995), and that they are likewise separated in the paedomorphic Ctenopyge ceciliae (CLARKSON & AHLBERG 2002). If eodiscoids are indeed paedomorphic derivatives of holochroal-eyed polymerid trilobites, is it not likely that they would have separated lenses too? It may be, therefore that the concept of abathochroal eyes as a separate eye type, though adopted earlier (CLARKSON 1997) is no longer sustainable, for the moment we leave the question open. In the descriptive part of the text, accordingly, we describe the eyes of eodiscids as abathochroal, because this term to date remains absolute as only known from eodiscoid trilobites.
  17. 4 likes
    When iron rust it will form a concretion in the surrounding material. I think this is an example of that process. Notice the pebbles embedded into the piece, very typical of a modern concretion of this type.
  18. 4 likes
    Rhaptagnostus cf. clarki maximus figures from: Zhu, X.J. (2005) Trilobite Faunas from Cambrian Upper Furongian of Guangxi with special notes on malformation, dimorphism, and function of eye ridges. PhD Thesis, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, 224 pp.
  19. 4 likes
    The first photo shows two partial bullas from baleen whales. More angles of the fossils in the second picture are needed to identify them. I think the object in the middle is a steinkern of a clam.
  20. 4 likes
    They are trace fossils. This one looks like an arthrophycid, possibly Arthrophycus isp. Seilacher, A. 2007. Trace Fossil Analysis. Springer-Verlag Berlin Or, they might be asterosomids, like Asterosoma.
  21. 4 likes
    Oh, my enthusiasm for speculation is still strong! Musing over 'possible improbabilities' is my outlet for curiosity. I am also a sucker for unexpected historical trivia (Colonial-era ship's ballast, for crying out loud!). But here, in the name of science, anecdote should be labeled as such, lest it takes on a life of its own. These free-wheeling, off-the-cuff topic digressions are a shining hallmark of our Forum, and I would never want to stifle them! Think of them as 'serendipitous education', but caution the less scientifically wired readers that they are not to be taken as conclusions.
  22. 4 likes
    I have to respectfully disagree with the ID of a rugose coral. The interior shows no structures resembling septa, tabulae, dissepiments, etc that would be expected of a coral. Rather, the fossil seems to me to be a portion of the siphuncle of an actinocerid nautiloid; Huronia is a likely candidate. Don C
  23. 4 likes
    The pics are blurry and the fossil is laterally compressed so the ID is tough on this one. Based on the size I would initially guess Grammysioidea sp. but there does not appear to be the wavy surface features which mark that genera. Instead it has what appears to be fine concentric growth lines which look similar to Nuculoidea sp. but that genera is much smaller than the specimen appears in the photo. I don't have any good references in front of me but I'll try to look again when I get home.
  24. 4 likes
    Based on the Poster's location (lacking a more detailed collecting site location) and some of the structure in the "matrix" , I'd suspect that its a metamorphic - shistose- formation, perhaps from a transitional area between sedimentary/metamorphic. According to the PA geologic Survey maps and my own collecting in the area this is a tightly folded area so a fraction of mile can make a big difference in basic rock type. Perhaps exposing the underside (by breaking off a piece) of the "coating/fossil" might reveal structures to clarify mineral or biologic origin.
  25. 4 likes
    Both are Rhinocerotidae. The first skull with the black teeth appears to be Subhyracodon. Probably Subhyracodon occidentalis. The second one, with the brown teeth, is Hyracodon. Very likely Hyracodon nebrascensis. Both are out of the Oligocene period, 25 MYA
  26. 4 likes
    This looks like 1/2 of a nodule from the Early Cretaceous Santana formation, in Brazil. Probably Rhacolepis buccalis . The fish looks like it was flattenened dorso ventrally, and you have the imprint of the bottom of the fish. Neat fossil. Regards,
  27. 4 likes
  28. 4 likes
    Here are a great white (Carcharodon carcharias) and an Aetobatus tooth from a site other than the main one(s) around Sacaco from which we have seen teeth (or perhaps an example of what was found on the surface). This Aetobatus tooth might be the coolest-looking one I have - rather large with deep color and some apparent microfossils embedded within the patch of attached matrix. I am starting this thread because there was a question in another thread about the range of preservation seen in fossils from the Pisco Formation, Sacaco area, Peru. We tend to see mostly lighter-colored (blue or pink or blue and pink), well-preserved great white teeth with great serrations but there were also some teeth on the market that were more worn and duller in color yet shiny from that wear. They appear to be more mineralized too. If you have similar Peruvian shark teeth, feel free to post your photos. You can't get them anymore but we can look at some of what was allowed to go before the export ban. I tried to pick up the widest variety of fossils while available. Jess
  29. 4 likes
    text from: Holdaway, H.K., & Clayton, C.J. (1982) Preservation of shell microstructure in silicified brachiopods from the Upper Cretaceous Wilmington Sands of Devon. Geological Magazine, 119(4):371-382 3.b. Beekite Ring Structure The most characteristic and intriguing type of replacement of calcite is by concentric rings of silica known as 'beekite' (after the Rev. Beek of Bristol who first drew attention to it; Hughs, 1889). It is seen on most bivalve shells, especially Exogyra (PI. 2 A) and pectenids, prior to etching, but in brachiopods the rings are not usually visible until a surface layer of calcite is dissolved away. Beekitized shells, from which all matrix and unsilicified material has been removed, are steely grey to white in colour, hard and brittle. The rings (PI. 2 A) appear as a series of ridges arranged around a central papilla. Where two or more ring systems meet, they do not produce complex interference patterns but abruptly truncate each other. This implies that individual rings of each ring 'nest' have grown sequentially rather than simultaneously. In three dimensions they comprise ellipsoidal to spherical layered systems, rather like the layers of an onion, truncated by the thickness of the shell. In coarse beekite, each layer can be up to 1 mm thick and well rounded where it meets the shell surface. Away from the centre of each system, the rings are usually finer and may coalesce. Since the number of rings in each group on a shell is not constant, the time of initiation and / or the rate of growth was not uniform. Where a shell is not completely replaced by beekite, the boundary is never adjacent to a beekite ring. The test at the edge of a ring is either more solidly silicified than the beekite area or passes into a milky white nodular material which grades into a white crust, similar to that described above (section 3.a). This distribution would indicate either that the white crust was the precursor of beekite or that replacement was too poorly developed for beekite to have formed here. In thin section the structure is complex. Silica shows a morphological sequence starting with radiating bundles and sheaths of length-fast chalcedony which exhibit straight, or rarely oblique, extinction up to 20°. This grades into quartzine (length-slow chalcedony with straight extinction), then to lutecite (also length-slow but with oblique extinction up to 30°), and finally indistinct, anhedral grains exhibiting extreme undulose extinction which resemble coalesced bundles of silica fibres (PI. 1B). All phases are usually clear in plane polarized light but may have areas of brown colorization and anomalous optical properties compared with quartz. This was ascribed, by Folk & Weaver (1952), to microscopic, water-filled pores, and by Pelto (1956) to a strained condition of the material with misorientation of the crystallites from fibre to fibre with regions of bad fit, and associated water, between bundles of fibres. Such a sequence of morphologies has been reported many times before (Jacka, 1974; Orme, 1974; Wilson, 1966; Chowns & Elkins, 1974; Rio & Chalamet, 1980; etc.). Length-fast chalcedony in the form of radiating bundles and sheaths is the usual form of fibrous quartz which occurs as a replacement of skeletal fragments or as chalcedonic overlays or crusts. Quartzine also occurs as colloform overlays or as a replacement of evaporite minerals. Lutecite commonly occurs as a replacement of evaporites (Folk & Pitman, 1971) but may also occur as a replacement of skeletal fragments (Wilson, 1966; Jacka, 1974; Orme, 1974). Anhedral gains similar to those in the Wilmington material were described by Chowns & Elkins (1974), who also reported a transition to quartzine, and as 'megaquartz' by Jacka (1974) who suggested that this is a solution-precipitation inversion from a metastable silica precursor. This morphology is more usually described as a finer grain size replacement, variously referred to as 'novaculite texture' (Folk & Weaver, 1952), 'granular microcrystalline quartz' (Wilson, 1966; Knauth & Epstein, 1976, and others), and 'silice en petit cristaux polygonaux' (Rio & Chalamet, 1980) and has been found by one of us (C.J.C.) to form a common replacement of opal-CT lepispheres. Indeed, a complete maturation sequence of spherulitic chalcedony to lutecite to quartz was suggested by Orme (1974). Tarr (1938) postulated that microfibrous chalcedony may, in time, pass over into quartz, and White & Corwin (1961) suggested a similar maturation sequence (glass-cristobalitekeatite-chalcedony-quartz) to explain experimental results on the synthesis of chalcedony. A morphological sequence, however, is not evidence of a maturation sequence. In most sedimentary rocks, including the material examined here, there is no clear growth sequence visible, and though some secondary ordering and recrystallization of the material occurs the observed variations in mineral form are probably more a reflection of the original form as precipitated rather than a series of intermediates in a full maturation sequence of opal to quartz. Beekite replacement almost invariably starts at the thickest part of the shell, in the umbones of brachiopods and bivalves, and spreads outwards, which results in characteristically shaped insoluble residues of partially replaced specimens. This is thought to be the result of two factors, one stochastic and the other mechanistic. Since the beekite is replacing calcite, it is most likely that it will be found where there is most calcite, i.e. at thickest part of the shell. In addition it is possible that partial pressure of carbon dioxide, which is believed to cause replacement (see below, section 5) might build up to a sufficiently high level to initiate silica dissolution more rapidly where the shell is thickest.
  30. 4 likes
    It is the front part of a catfish skull.
  31. 4 likes
    The preservation is not perfect, but the extremely long dorsal fin is conclusive. I would guess it is Istieus macrocephalus Agassiz. At least this is the only fish with such a long dorsal fin I know from Baumberge / Sendenhorst. Thomas
  32. 4 likes
    After visiting my crew out in Placitas (short drive from ABQ), I decided to stop at a BLM open space at the roadside. There is a supposed Upper Cretaceous section exposed here and I figured I would eat my lunch and go for a short walk. If there was an K section, it did not look the part... ...the surface of the slopes are covered with Carboniferous (Pennsylvanian) rocks. I mosied along the trail, munching on a granola bar when I spotted some concretions and shale up a gully... ...and upon further inspection, an ammonite! I quickly marched my coiled companion to the truck...back to work! There is definitely some Upper Cretaceous rocks here and well worth a return trip. Planned or impromptu...happy hunting! -P.
  33. 4 likes
    This thread is a good example of why we should strongly discourage using links to outside image storage sites such as photobucket: they links often quickly die, leaving a thread stripped of images. People should instead upload their images to the Fossil Forum so they can be permanently be associated with the thread. While googling for info about local trilobites, images from the thread came up in the search page, though they can no longer be accessed by clicking on the images themselves in Google, or through the Forum. In order to restore this thread to some semblance of its original self, I copied and saved the images I was able to find. As they are from the image search page they may be degraded compared to the originals. Don C
  34. 4 likes
    Here are a couple pictures that I had posted in the past to show how the re-planting of the are has changed the landscape of Pit 11 (Tipple Area) since the Strip Mining was going on. The following 3 pictures are of the same exact area, just years apart: 1971 1993 2012 And since 2012, the vegetation has just increased and limited the weathering process, thus locking up concretions in the ground, maybe never to see the light of day. Hope you enjoyed this quick post.
  35. 3 likes
    Hello Coco, Mark was correct. This is a Brannerion sp. The formation information sounds correct. This is one of the nicer ones I've ever seen. Regards,
  36. 3 likes
    How far you have to go to find fossils depends totally on where you are. There are many exposures with no fossils at all. If there are public waterways or road cuts that expose rock in your area that is a place to start but often the best way to be sure you're not wasting time on a barren formation is to look for the closest rock and fossil organization for help. They know which places to collect and which to avoid. Sometimes they even make arrangements to collect on private property. Here in Texas there are even rock quarries that let groups in. They ask you to sign a hold-harmless agreement and wear a hard hat to appease their insurance companies but that's understandable. Many groups are a combination of gem & mineral fans and artifact hunters and amateur paleontologists but even these have field trips that might appeal to your interests or even information about public sites on a website or brochure. Maybe a forum member in your area will know of one to check out or a site they will share information on.
  37. 3 likes
    These fossils are actually the siphuncle by the way. I don't think the whole shell (with camerae, exterior, or living chamber) has ever been described (or found). Don
  38. 3 likes
    Neat collection so far! Your fish is a Diplomystus dentatus, rather than an Knightia eocaena. The large anal fin is the main distinguishing feature - Knightia doesn't have that large of an anal fin. Thanks for sharing with us. Regards,
  39. 3 likes
    I just saw this post. I hesitate to open an old topic, but this is quite interesting.This is a shark tooth file. It resembles Helodus coxanus, but is not identical. The teeth are much broader. These are photos of the type specimen of Helodus coxanus in the Smithsonian. This might be something new.
  40. 3 likes
    It is indeed a coral, looks like a Devonian tabulate one. Thamnopora is a strong likelihood - a 5 pence piece is about 18mm across making the corallites 1.5mm+ .
  41. 3 likes
    This post is prompted by finding a near complete specimen of Cornuella cf. ornata, Brigantian, (Mississippian) shale above the Four Fathom Limestone. Co. Durham, UK. Apart from one fragment from the early 19th century I can find nothing comparable in the UK literature.. Fine specimens have been found in Russia from the Serpukhovian Stage (upper Mississippian, slightly later than this one). See at the end of the post for both of these. I previously had just a single, small fragment which was a mystery. A friend then gave me another fine 3D fragment from Scotland and this was kindly identified by a Russian collector on another forum (@valh on here, thank you Valerij!). Details on TFF here: ornamented orthocone, scotland Here's my new specimen which was in a wet, disintegrating mudstone. I held it together in the field with cyanoacrylate then dried it for a few days. Prepping was with a scalpel under a 20x microscope, consolidating the matrix and shell with 5-10% paraloid as I went along. (Took about 25 hours I think.) It's too fragile to risk air abrading - the shell was already gone from the living chamber and barely attached to the rest of it. As collected: The first UK reference is Orthocera rugosa, Fleming 1828, a fragmentary specimen with a description only. This was figured in 1835 in Phillips "Illustrations of the Geology of Yorkshire" Vol. 2, plate 21, no. 16 naming it as Orthoceras rugosum Fleming. I can't find another figured specimen in UK literature. (Phillips simply gives "Northumberland" as the locality - the next county up from Durham.) Below is the plate of Russian Cornuella ornata (Eichwald) from Shimansky, 1968. (Shimansky, V. N., 1968: Kamennougolniye Orthoceratida, Oncoceratida, Actinoceratida i Bactritida (Carboniferous Orthoceratida, Oncocerida, Actinoceratida and Bactritida). Akademiia Nauk SSSR, Trudy Paleontologicheskogo Instituta, vol. 117, p. 1–151, pls. 1–20. (in Russian). And here's my original mystery fragment:
  42. 3 likes
    This looks like imprinted slag, to me.
  43. 3 likes
    The long slender pygidial spines belong to: Bellacartwrightia sp.
  44. 3 likes
    It looks like an oyster valve with predation marks on the inner surface of the shell.
  45. 3 likes
    Marine transgressions rework ("erode &/or transport")previously deposited strata(and their fossils).Reworking is not unknown in the Appalachian Basin.
  46. 3 likes
    I would say no...they share the same order but are from different clades/suborders.
  47. 3 likes
    Rustdee is correct about #3. It is a sawfish rostral tooth. This one is from Anoxypristis and is most likely Oligocene.
  48. 3 likes
    @Monica is correct on #5. Top is a Galocerdo (Tiger) and bottom is a Hemipristis serra. @WhodamanHD is correct on #4, croc or gator. #3 You need to post photos from all sides. Might be fish tooth.
  49. 3 likes
    I believe you have found two specimens of Astrocystites ottawaensis. Here is a link to a photo of one from Crinus's web site. This is an edrioblastoid, a cystoid that was once thought to be ancestral to the blastoids, though it now is thought that blastoids evolved through a different lineage. Astrocystites is one of the rarest of the Ordovician echinoderms, most collectors never see even an isolated plate of one of these. Congratulations on an exceptionally rare find! Don C
  50. 3 likes
    These Bonnington pygidia match well with: Conophillipsia subtriangularis Engel, B.A., & Morris, N. (1984) Conophillipsia (Trilobita) in the early Carboniferous of eastern Australia. Alcheringa, 8(1):23-63
×