http://antimonite.blogsome.com/2009/01/21/two-cretaceous-fossils/ A blog about geology, geoscience, paleontology and related topics Thu, 03 Dec 2009 15:34:20 +0000 http://wordpress.org/?v=1.5.1-alpha http://antimonite.blogsome.com/2009/01/21/two-cretaceous-fossils/#comment-225 Thu, 22 Jan 2009 11:58:28 +0000 http://antimonite.blogsome.com/2009/01/21/two-cretaceous-fossils/#comment-225 Howard: Thanks a lot for your answer! I agree with your theories. Howard: Thanks a lot for your answer! I agree with your theories.

]]> http://antimonite.blogsome.com/2009/01/21/two-cretaceous-fossils/#comment-224 Thu, 22 Jan 2009 09:57:08 +0000 http://antimonite.blogsome.com/2009/01/21/two-cretaceous-fossils/#comment-224 Echinoid (sea urchin) spines. The second picture is for sure an echinoid spine; the first picture is a bit fuzzy due to the depth of focus, but it's probably also an echinoid spine. The flat surface on the broken end of the spine in the second photo is a dead giveaway. Echinoderm plates and spines are made of single crystals of calcite, therefore they tend to break along cleavage planes. The swollen end of the second spine is where it attached to the shell, in a ball-and-socket joint that allows it to pivot in all directions. Echinoid (sea urchin) spines. The second picture is for sure an echinoid spine; the first picture is a bit fuzzy due to the depth of focus, but it’s probably also an echinoid spine. The flat surface on the broken end of the spine in the second photo is a dead giveaway. Echinoderm plates and spines are made of single crystals of calcite, therefore they tend to break along cleavage planes. The swollen end of the second spine is where it attached to the shell, in a ball-and-socket joint that allows it to pivot in all directions.

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