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Showing results for tags 'thelodont'.
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I have read in multiple papers that there are three theories to the preservation of thelodont scales. First, a rapid burial when the thelodonts have died under still circumstances, e. g., in a lagoon or other still body of water. This results in associated scales. Second, the thelodonts die and disintegrate in the open ocean, leaving behind disassociated scales. Third, the thelodonts were eaten, and deposited as coprolites. Now, I have just found an array of thelodont scales in a single small spot. The stone they are preserved in is a lighter color than the rest of the shale. The majority of the scales are Phlebolepis elegans, with one being of a Thelodus parvidens. I was wondering if it could be an example of a coprolite? It is from the Leighton Formation, Maine; which is Pridoli, Silurian. The pictures below first show the cross section of the specimen, and then the top of it. I will take pictures of the individual scales as soon as possible. It is rather hard to see the cross sections in the pictures, but the bluish pieces are thelodont scales. Unfortunately, I don't think it will be able to be prepped without destroying some of the details. Thanks in advance for your help! @GeschWhat @Rockwood @jdp
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From the album: Harding Sandstone
Possible early shark or shark-like denticles. Magnification 40x. -
From the album: Harding Sandstone
Possible early shark or shark-like denticles. Magnification 40x + iPhone zoom. -
Originally described as Thelodus scoticus Traquair, 1898. Taxonomy from Märss & Ritchie 1997. Revised diagnosis from Märss & Ritchie 1997, p. 150: "Scales medium-sized (up to 0-6 mm long), made up of crown, neck and base. Rostral scales not distinct. Crowns of cephalo-pectoral scales are rounded to rhomboidal with notches around the crown margin or only anteriorly; postpectoral and precaudal scales rhomboidal becoming more elongated posteriorly, median crown plate flat, smooth or with a notch anteriorly which becomes a furrow on the posteriorly situated scales. Beneath the median plate, the longitudinal ridges on the postero-lateral portions of the crown converge in the posterior crown apex. There are two types of pinnal scales. The scale crowns of the leading edges of all fins are flat, smooth and with two notches antero-laterally. The scales of the trailing edges of lateral and caudal fins are cuneiform. Neck of the scales is as a shallow groove, base rhomboidal with moderate spur anteriorly." Traquair's original reconstruction in dorsal view: Identified by oilshale. References: Traquair, R. H. (1898) Report on fossil fishes. Summary of Progress of the Geological Survey of the United Kingdom for 1897, 72-6. Volume 16: Fossil Fishes of Great Britain. Chapter 2: Silurian fossil fishes sites of Scotland. Site: BIRK KNOWES (GCR ID: 359). Žigaite· Ž. & Goujet D. (2012) New observations on the squamation patterns of articulated specimens of Loganellia scotica (Traquair, 1898) (Vertebrata: Thelodonti) from the Lower Silurian of Scotland. Geodiversitas 34 (2): 253-270. Märss, T., & Ritchie, A. (1997) Articulated thelodonts (Agnatha) of Scotland. Transactions of the Royal Society of Edinburgh: Earth Sciences, 88(03), 143–195. doi:10.1017/s026359330000691x
