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Showing results for tags 'staithes sandstone formation'.
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Fossil of the Month, January 2015. Prepping details here: Jan 2015 finds of the month A partial, extremely rare, many armed starfish, the genus was assigned to a new family Plumasteridae in 2011: A. S. Gale. 2011. Asteroidea (Echinodermata) from the Oxfordian (Late Jurassic) of Savigna, Départment du Jura, France. Swiss Journal of Palaeontology130:69-89 This is from the same area and formation as the holotype of its species. The distinctive ossicles are common as disarticulated elements in sieved samples from Pliensbachian to Oxfordian. Excerpt from the above paper: Family Plumasteridae nov. Diagnosis: Multiarmed (12–22 arms) asteroids with broad adambulacrals which occupy the entire actinal sur- face of the arm and V distally: adambulacrals concavo- convex, 5–8 specialised interlocking articulation ridges and grooves articulate with ridges on adjacent adambulacral (modified ada2-3); abactinal ossicles with numerous lateral projections and embayments, and each carries a central large convex boss with which long, glassy, ridged spines articulate. Type genus: Plumaster Wright 1863, is the only genus included. It ranges from the Pliensbachian to the Oxfordian. Discussion: The Plumasteridae is established for the distinctive multiarmed genus Plumaster. This is distinguished from other multiarmed spinulosans such as solas- terids by the unusual boss-like spine articulations of the abactinal ossicles, and the highly modified adambulacral ossicles, which articulate by means of ridges and grooves.
An unusually complete specimen although crowns are well known from this location. It is an early comatulid (feather star) and has a very short stem consisting of only six or seven columnals, all of which bear cirri. Reference: Simms, M.J. 1989. British Lower Jurassic Crinoids. Monograph of the Palaeontographical Society, London:1-103, pls.1-15 (No. 581) This was Invertebrate/Plant Fossil of the Month March 2015
As often the case with brittle stars and other starfish, this shows the oral surface and is on the underside of the sandstone bed. The bed below it is a shale and the base of the sandstone represents a sudden influx of sediment which preserved the brittle star nearly intact. This was Invertebrate/Plant Fossil of the Month Sept 2014 and Fossil of the Year 2014.