Pumpkinhead Posted July 28, 2015 Share Posted July 28, 2015 This is from the Fossil Hill formation and Silurian in age. It does look somewhat like part of a rugose coral, but I also thought sponge because from the side view it is not symmetrical. The one side slopes downwards and the other upwards- I would expect a rugose coral to be much more uniform. Its structure just doesn't "feel" like a solitary coral to me and it is much larger than the colonial rugose I find there, which I believe to be arachnophyllum. Another difference between it and the colonial rugose I find is is that the columella is much less pronounced, which I don't think is due to poor preservation as the septal structures as they are fairly well pronounced. Incidentally, there are 60 septa present which is a multiple of four- so I think there's evidence on both sides. Thought I'd share it with all you. What does the fossil forum community think? Ill grab some examples of what I think are "typical" examples of rugose corals where I am for comparison as well when I'm out this afternoon. Thanks, Pumpkinhead Link to comment Share on other sites More sharing options...
FossilDAWG Posted July 28, 2015 Share Posted July 28, 2015 I believe it is a single corallite of an Arachnophyllum, broken off a larger colony. Don Link to comment Share on other sites More sharing options...
Guguita2104 Posted July 28, 2015 Share Posted July 28, 2015 (edited) I agree with FossilDAWG...A coralite of an Arachnophyllum.See this photos on TFF galery and compare with yours http://www.thefossilforum.com/index.php?/gallery/image/19949-arachnophyllum-sp-silurian-louisville-kentucky-usa/. The geological age matches with the age of the formation where do you found it. Edited July 28, 2015 by Guguita2104 Link to comment Share on other sites More sharing options...
Pumpkinhead Posted July 28, 2015 Author Share Posted July 28, 2015 I thought it looked similar, but what caused me to be suspicious was that its about five times as large as the largest corallite I've ever found on an arachnophyllum specimen. As I said earlier, it is also not symmetrical from a side view- in all of the colonial rugose corals I've ever found the septa slope upwards from the columella and if you were to cut a corallite in half you you would have more or less a mirror image on both sides. What do you guys think would cause these differences? Has anybody ever come across arachnophyllum specimens this large? Link to comment Share on other sites More sharing options...
Pumpkinhead Posted July 28, 2015 Author Share Posted July 28, 2015 Fossil with dime to scale- for comparison this is about the size of an american penny Link to comment Share on other sites More sharing options...
Guguita2104 Posted July 28, 2015 Share Posted July 28, 2015 The size depends of many factors (including the water "composition")...They absorb the elements they need from water, conjugating the water calcium and the carbonates to form aragonite (their exoskeleton is "made" of this mineral).If these and other elemnts weren't in the correct rate the growth will be limited.The irregularity can be derived of many factors. Link to comment Share on other sites More sharing options...
FossilDAWG Posted July 28, 2015 Share Posted July 28, 2015 There are two species of Arachnophyllum in the Fossil Hill, and one has much larger corallites. I'll have to check which is which when I get home later. Don Link to comment Share on other sites More sharing options...
Pumpkinhead Posted July 28, 2015 Author Share Posted July 28, 2015 Thanks, I've been trying to make a compendium of the common species there so if you wouldn't mind shooting me both of the species names that would be great Link to comment Share on other sites More sharing options...
Pumpkinhead Posted July 28, 2015 Author Share Posted July 28, 2015 Come to think of it, if anyone wants to help with it just send me a pm and I will send you the table so you know where it is needed to chip in. I still don't have anything at all for the molluscs there or the solitary rugose and a lot of the other groups need help as well. This would probably be helpful for collectors on the niagara escarpment if completed Link to comment Share on other sites More sharing options...
Guguita2104 Posted July 28, 2015 Share Posted July 28, 2015 Maybe an arachnophyllum pentagonum. Link to comment Share on other sites More sharing options...
Archimedes Posted July 29, 2015 Share Posted July 29, 2015 You might check Chonophyllum, I have afew of these from the middle Silurian in Tennessee Link to comment Share on other sites More sharing options...
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