Knightia alta

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Knightia is at the bottom of the predatory food chain in the Green River Shales of Wyoming, USA.  Going back over 50 million years and covering an exposure area of about 2,5000 miles to a thickness of about 2000 feet, these rocks are full of fossil fish.  This specimen is 5cm long and it is difficult to determine whether it is Knightia oceana or Knightia alta, the two most common species that make up about 95% of fossil fish finds in this part of the world.
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Many of these specimens are damaged or distorted when the rock is fractured.  In this one, the jaw and lower head is damaged.  There is also fragments of another fish below its belly.  This is typical of many specimens that are sold as beginners collection specimens for a few pence.
2012-Dec28-Fish3However, with so many fossils available there is a good chance that one will be complete.  This is a specimen of Knightia alta and the fish is preserved in its entirety, showing the skeleton and soft tissues, fins and jaws, all in their original position as the fossil was preserved.  This wealth of fresh water herrings has allowed study of the population dynamics and ecology of these fossil fish, which show that they were living in a world that is essentially the same as the world we are living in today (without the impact of human activity).

Skull

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Visualizing pterosaur skulls can be difficult, especially from drawings and photographs.  It is much easier to see the representation in solid form.  This model is a work in progress, to model the skull of the Rhamphorhynchoid pterosaur, Cacibupteryx carabensis from the Jagua Formation of western Cuba.
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The original skull was well-preserved, but incomplete, missing the anterior maxilla.  As a result, the tooth structure at the tip of the jaw is not known.  The model is a best guess in that respect.
2012-Dec25-Skull-3The overall shape is very solid for a pterosaur and it is characteristically similar to many of the more primitive species.  The lower jaw is not known as only the skull and part of the wing have been found.

Size Variation

2012-Dec24-CylindroteuthisThe above fossils are all specimens of Cylindroteuthis puzociana from the Oxford Clay near Peterborough.  The specimens are all from the same locality and show differences in size (due to maturity) and texture (due to preservation).  This species was one of the main staples of large marine reptiles.  The fossils are found in abundance with ammonites, rock oysters and reptile bones.

Variation in Belemnites

2012-Dec23-NeohibolitesThe Red Chalk, near Scunthorpe is full of interesting fossils.  These are belemnites which are found to have a number of variations to the basic form  the ones shown represent Neohibolites minimus minimus; Neohibolites minimus rubusta and Neohibolites minimus hastata, which are all found in the same horizons.  These same belemnites are also found in the Red Chalk horizons at Hunstanton, about 90 miles away.  These fossils are of Gault Clay age from the Middle Cretaceous.

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Bivalve

2012-Dec22This bivalve is another unusual fossil perspective.  It has been sectioned in a polished limestone slab and the top of the valve has been ground off.  The dimensions suggest that it is a type of pectin shell.

Problem fossil

2012-Dec21This very small fossil looks a bit jaw like.  it is tiny at only 2mm long.  I have no idea what it is, but whatever I imagine, it is sure to be something else!