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Many forum members are familiar with Cookiecutter Creek in South Florida. This is a small creek that well-known forum member Jeff @jcbshark was kind enough to share with me a little over 3 years ago. Jeff had posted photos of the tiny Cookiecutter Shark (Isistius triangulus) teeth that he had found picking through micro-matrix from this creek and that started my quest to obtain a tooth from this very unusual little shark. After picking through many gallons of micro-matrix from the Peace River and some of its feeder creeks without once laying eyes upon a single Isistius tooth (but finding tons of other micro fossils), Jeff informed me that he didn't think Cookiecutters could be found anywhere other than one special little creek and agreed to take me and Tammy to collect some micro-matrix there in mid-December 2014. It didn't take long for me to find my first complete Isistius. Several more soon followed including some from the positionally rare symphyseal spot in the middle of the lower jaw. It is possible to identify a symphyseal as the thinner area where each tooth overlaps the adjoining tooth is usually found with one overlap area seen on the inner and one on the outer surface of each tooth but not symphyseals. Since these teeth overlap BOTH the tooth to the left and right (like the top row of shingles on the ridge of a roof) the overlap marks are both found on the inner (lingual) surface of the tooth and no marks are found on the outer (labial) surface. Once you know how the teeth of the lower jaw overlap and how to identify the outer (labial) side of the tooth (the enamel does not stop at a well defined line but extends down from the triangular crown and onto the square root), you can also tell which side of the jaw (left or right) that the tooth came from. Aside from the symphyseal position most of the other teeth cannot be identified to position other than the last one or two posterior positions. These teeth have the crown angled with respect to the root. Here are some of my old posts showing Cookiecutter Creek and the micro-fossils that have come from this unique locality in Florida: http://www.thefossilforum.com/index.php?/topic/51286-collecting-cookiecutter-shark-micro-matrix/ http://www.thefossilforum.com/index.php?/topic/55298-more-micros-from-the-peace-river-and-cookiecutter-creek/ http://www.thefossilforum.com/index.php?/topic/71406-optimizing-micro-matrix-sorting/ Recently, I've been working on a project with a PhD student from the University of Florida which was initiated when it was realized that the Isistius triangulus teeth that I donated to the FLMNH were not yet recognized as occurring in Florida. Additional research revealed that specimens of Squatina (Angelshark) teeth from this creek were also not known from Florida (though I've also found this genus in micro-matrix from the Peace River). I made another collection of micro-matrix from Cookiecutter Creek as I had exhausted my supplies. A couple of flat-rate boxes of this material made their way into the hands of a couple of forum members--who I hope are having fun with this unique micro-matrix. Tony @ynot had sent me photos of another interesting find from Cookiecutter Creek. Jeff had collected some additional micro-matrix on the day that he introduced me to this site. Some of that collection was later made available to Tony as an auction to benefit the forum. While looking through this micro-matrix, Tony discovered a small specimen of what appears to be a Catshark (Scyliorhinidae) tooth. Tony is graciously sending that tooth to me so that I can pass it along to be added to the collection at the Florida Museum of Natural History (FLMNH) as this is the first record of this shark family in the Florida fossil record (and another first for Cookiecutter Creek). Tony's photo if this micro beauty: Since learning of the possibility of this taxon being found in the micro-matrix of Cookiecutter Creek, I've been searching through my remaining stash from this locality hoping to find a second Catshark tooth (no luck yet). While I've (so far) struck out in duplicating Tony's amazing find, I did have a bit of luck last week with something else new from my searching. While picking through the micro-matrix I came across an elongated item just about 10mm in length. If I'd not been familiar with this type of highly unusual shark tooth before I might have passed it by thinking it was just some unidentifiable fragment of bone. Experience and knowledge (even just a small amount) allowed me to recognize this as a tooth type that is reasonable common in another type of wonderful micro-matrix--Shark Tooth Hill (Bakersfield, CA). The unusual tooth from Cookiecutter Creek is actually quite common in STH micro-matrix. It comes from a Horn Shark (Heterodontidae). Since there is currently only a single genus described for this small family of small sharks, it can actually be identified down to the genus Heterodontus. These are placid little sharks that I remember seeing resting on the bottom during the few dives I did among the kelp forests in southern California's Channel Islands. They have distinctive ridges over the eyes and a single spike at the leading edge of their two dorsal fins. They feed mainly on hard-shelled invertebrates (crustaceans, molluscs, and echinoderms). Their name "Heterodontus" derives from the Greek meaning "different teeth" and referring to the fact that the front teeth are pointy with larger central cusp flanked by a smaller cusp on either side. The back teeth elongated with a long ridge running the length of the tooth and are adapted to crushing the hard shells of their prey items. https://en.wikipedia.org/wiki/Horn_shark Currently, most members of this family are found in the Indo-Pacific--like the well-known Port Jackson Shark (Heterodontus portusjacksoni) and only the Californian Horn Shark (Heterodontus francisci), the Galapagos Bullhead Shark (Heterodontus quoyi), and the Mexican Hornshark (Heterodontus mexicanus) are found in the eastern Pacific off the west coasts of North and South America. It's difficult to make any firm conclusions from the scant images available online but the rear teeth of the Mexican species to have a reasonable resemblance to the specimen that turned up in Cookiecutter Creek. Today, there are no species from this family inhabiting the Atlantic (or the Caribbean or Gulf of Mexico regions). Devoid of any factual information but attempting a modestly educated guess, I'm thinking that one of the species of Bullhead Sharks must have extended over into the waters surrounding Florida some time before the Isthmus of Panama formed some 2.8 mya separating the Atlantic and Pacific Oceans and separating the fauna on either side to either develop into distinct species (or to go extinct regionally). Since this family is not currently known from the Atlantic (eastern or western extents) it seems more reasonable to assume that the Florida specimen derived from an eastern Pacific species given the (geologically) recent connection to those waters. Fun to speculate and if Marco Sr @MarcoSr has jaw samples of extant eastern Pacific members of this family, perhaps a better comparison to the anterior teeth might be possible. Both this tiny Heterodontus tooth and Tony's find of the Scyliorhinidae will soon be headed toward Gainesville. I'm hoping to get up to volunteer at Montbrook in the next couple of weeks and plan on dropping off a few donations to expand the museum's diversity of shark teeth from Florida. Cookiecutter Creek is a special little creek and is best known for its relative abundance of Isistius triangulus teeth. The more we investigate this locality and the more micro-matrix we pick through from there the more unusual taxa seem to turn up. Seeing a perfect little Cookiecutter tooth appear from the micro-matrix is always a thrill but this creek is no longer a one-trick pony. It seems to have hidden depths (for a creek that is only knee high ) and I'm looking forward to seeing what else might appear out of the gravel in the future. Cheers. -Ken

Finally managed to get out on a Florida fossil hunting trip for the 2014/15 season here in South Florida. Instead of going to the Peace River (where the water level is still dropping from a huge spike due to heavy rains nearly a month ago around Thanksgiving) I contacted Jeff (jcbshark) and we planned an outing at the creek where he collects his world famous cookiecutter shark micro-matrix. Earlier this year I had searched--cup by cup--through nearly a 5-gallon bucket of micro-matrix I had collected from the Peace River looking for cookiecutter shark teeth (to no avail). It seems that cookiecutter shark fossils are absent (or incredibly rare) in the deposits that the Peace cuts through. I've been fascinated with cookiecutter sharks since I learned about them as a kid (yup, I was a fish geek even then). The odd hole-saw-like fused lower dentition of this shark has been on my fossil bucket list since I first saw the images on this forum. Many of these images were posted by people searching through samples of the micro-matrix that Jeff had sent out to TFF members. It was high time I got in on the fun. I met up with Jeff and a few of his wife's relatives (who were new to fossil hunting) on the creek early Saturday morning. We were later joined by Chris (Search4) who came along to try his luck. The air temps were still climbing out of the low 60's but the skies were clear and the temps would later top out in the upper 70's so the chilly water (likely somewhere in the mid 50's) was actually quite bearable once you got used to it (read that as "numb"). The creek was mostly pretty shallow and I didn't get any deeper than about knee-deep all morning. My wife Tammy (always the more practical) was wise enough to bring her waders for comfort (and style). Jeff led us to the location he had previously collected his cookiecutter micro-matrix though he mentioned that there was likely nothing special about this spot and that the same sort of matrix could likely be gathered from anywhere along the creek. The creek which is the source of the cookiecutter micro-matrix. I had brought my micro-matrix collecting gear and soon got to work. I have sifting screens that I've made for searching the gravel beds of the Peace River and its tributaries. I've previously described how I make my sifting screen (and my probe) here: http://www.thefossilforum.com/index.php?/topic/42992-end-of-year-peace-river-trip/#entry467550 I've since converted one of my sifters from 1/4" mesh to 1/2" mesh for when I work areas with coarser gravel or when I want to work through larger amounts of gravel quickly while looking for larger items. I brought my 1/2" sifter along with one of my 1/4" sifters as well as some 1/16" window screen mesh cut to size so that it fits comfortably into the sifting screens. The technique I use to collect micro-matrix is to double sift using a stacked pair of sifting screens. I place the fine window screen mesh inside the sifter with the 1/2" mesh. On top of this sifting screen I stack my sifter with the 1/4" mesh. The arrangement can be seen below: Loose window screen mesh fits inside one sifter and a second sifter fits on top of the first. The stacked sifters efficiently sort out the micro-matrix.

Here are a few of the micro fossils I've been having fun with recently. I've gathered some micro-matrix from Jeff's magic cookiecutter shark creek as well as some from the Peace River where John and I had good success with large mammal fossils (Proboscideans in particular). I've gone through a couple of plastic Solo cups of the cookiecutter micro-matrix in search of additional specimens of Isistius shark teeth to add to my small but growing collection. In my last batch of micro-matrix from this spot I've found a few nice ones including an unbelievable number of midline (symphyseal) teeth. This batch has already given up two Isistius and they've been nice complete teeth and not the more common fragments. Apparently, I must be some sort of Pied Piper of Isistius or possibly a symphyseal savant as one of these two is a really nice looking tooth with the two overlap notches on the same side marking this tooth as yet another symphyseal--I think this makes 3 or 4 now. A nice complete symphyseal Isistius and a more common non-symphyseal with a bit of a chip on one corner: Cheers. -Ken

Here is the summary of my finds from the Florida matrix sent to me by TFF member jcbshark. It is his famous Cookie Cutter matrix! It contains fossils from the Miocene thru Pleistocene. Thanks again Jeff for this great matrix. I was very pleased to find these three Isistius teeth. Here is a selection of the shark teeth from this matrix. continued in the next reply