LifeArtEarth

Aragonite is a common mineral in the skeletons of marine organisms (Cusack & Freer 2008), but is not typically well preserved in the fossil record due to its tendency to recrystallise as its more stable polymorph calcite. Certain circumstances however can enhance the preservation of the original aragonite, including reducing conditions (Jordan et al. 2015), low temperatures (associated with limited burial depths), and burial in impermeable sediments (Hall 1967, Vendrasco et al. 2018).  Four Middle to Lower Jurassic examples of preservation of aragonite shells, consisting of two belemnoids and two ammonites, are illustrated here below. Consideration of these examples also leads to a discussion on preservation of soft parts in fossil cephalopods. Middle Jurassic Oxford Clay of Christian Malford The Middle Jurassic of Christian Malford (Wiltshire) is celebrated for the exceptionally preserved fauna it contains (Pearce 1842, Wilby et al. 2004, 2008). J. Chaning Pearce read his pape...

A distinctive type of 19th/early 20th century pipe from Gabon (shown here below) is constructed of wood with an iron bowl, a brass stem and bindings of brass and copper wire. Dealers readily attribute this form to the Kota, without specifying if this is "Kota" in the sense of the Kota people (Guthrie code B25 in the Kele group) or the much broader careless ragbag and much criticised terms "Kuta"/"Kota" of the art world (e.g. Andersson (1953) and Perrois (1970); Perrois (1985, pg 37) offered a weak defence). But is this correct? Examination of 19th century texts and museum collections suggests not. A distinctive pipe from Gabon, made of wood, with brass stem and wrapping and an iron bowl, 44 cm long, offered as "Kota", but is it? Here below (at left) is a very similar example, but with more precise provenance, from the Ndasa village of Mapinda (Andersson 1953). Inspecting the Musée du Quai Branly collection online reveals 11 pieces in this style. ...

Replacement of fossils by silica can preserve fine-scale features (e.g. Roniewicz 1970, and see Butts 2014). Perhaps the most famous instance is that of the Permian Vidrio Formation in the Glass Mountains of West Texas (e.g. King 1930). Sowerby (1809, p. 181) provided an early illustration of another such case from the Jurassic of England (his TAB. CCXCI), shown below. Sowerby named the specimen ' S I L E X Quartzum coralliformis. Coralliform Flint. Div. 2. Imitative. ' and wrote: ' This is one of the most beautiful, and perhaps local, of the Flint Coral formations, and is found in tolerable abundance in a field near Tidsbury, Wiltshire , in pieces, sometimes as large as a quartern loaf. Some specimens show the remaining form of a real Coral most perfectly having at the same time little globular infiltrations, as if in the act of filling the spaces of the Coral with a whitish calcedony or cachalong-like substance, which more solidly pervades the Flint in other parts ; and a...