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Boldnor Fm -Isle of Wight
 
Searching for mammal and crocodile remains in the Hamstead Mbr

There are surely few localities more hellishly muddy than the "beaches" at Boldnor Cliff on the north coast of the Isle of Wight. Many an abandoned wellington boot can be found firmly stuck in the abundant flows of "blue slipper": a self-explanatory local name for the smectite-rich clays found across the island. As if the ground underfoot were not treacherous enough, the beach abounds with dozens of felled trees, inhibiting your progress with woody malice. Boldnor's position on the southern margin of the Solent valley assures you of a miserably damp day's collecting, even in summer.

Nevertheless, should you succumb to its sticky allure, the terrestrial Boldnor Fm (Hooker et al, 2004) yields a rich diversity of important vertebrate fossils, which frequently smell of rotting seaweed (and worse)..

 

The Bembridge Marls Mbr exposed during low tide at Boldnor Cliff


Selection of anterior teeth, from the anthracothere Bothriodon. coin diameter =27.3mm

I concentrate my collecting in the Bembridge Marls and Hamstead Mbrs, at Boldnor Cliff itself. The Eocene-Oligocene boundary (~34Ma) occurs a little way up from the base of the Bembridge Marls Mbr, and shortly after that occurs the Grande Coupure: an extinction in the northern hemisphere, especially of large terrestrial vertebrates. Since both events occur within a short interval at the base of the unit (literally, only a few metres in thickness), it is very important to keep record of the stratigraphic position where you find fossils.

For the most part I collect just above the Grande Coupure extinction, although in 2000 I found the right metatarsal II of an Anoplotherium skeleton just below the event bed. This skeleton has been collected since 1967 from the slowly eroding cliffs, and was the subject of a recent study (Hooker, 2007)

 

 

Exposure of the Bembridge Marls Mbr just above the Grande Coupure event bed


Three left maxillae of the alligatorid Diplocynodon hantoniensis


A selection of limb bones from Bothriodon


An assortment of teeth from Diplocynodon hantoniensis


Scutes from Diplocynodon hantoniensis


Distal end of a humerus from a rhinocerotid: probably Ronzotherium
(Hooker, pers. comm. 2008)

Pathological Diplocynodon scute with necrotizing dermatitis (probable bacterial or fungal infection).See how the normal pitted ornamentation has been eaten away by the infection. This specimen was published in Historical Biology by myself and coauthors (Wolff et al, 2007)


mammalian microverts: insectivore dentary fragment (left) & isolated tooth (right)
(scale=mm)

In recent years I have been collecting samples of the microvertebrate-rich clay lenses that you can find here, just after the Grande Coupure. I send all of my useful material to the expert on these deposits: Dr Jerry Hooker at the Natural History Museum, London .

Hooker , J.J., Collinson , M.E. & Sille, N.P. (2004) Eocene-Oligocene mammalian faunal turnover in the Hampshire Basin, UK: calibration to the global timescale and the major cooling event. J. Geol. Soc. Lon., 161: 161-172.

Hooker, J.J. (2007) Bipedal browsing adaptations of the unusual Late Eocene-earliest Oligocene tylopod Anoplotherium (Artiodactyl, Mammalia), Zool. J. Linn. Soc. 151: 609-659

On the way to the beach you pass through a small field which in good years is bursting with thousands of wild orchids. This species blooms early in the year, around April-May. Through the summer different species bloom in the same field.

The route down to the beach also runs through Boldnor forest, which aside from being very pretty, is one of the strongholds of the red squirrel in southern UK