Early Ammonoids

Joined
Mar 7, 2009
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542
Here's a real Bactrites from the German Devonian (Büdesheim, Eifel), just 16 mm long, but beautifully preserved in pyrite. The ventral lobe on the sutures is nicely seen on this specimen.
 

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and this is an Anetoceras, 44 mm across, from the Early Devonian of Bundenbach.
 

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Another early ammonoid in pyrite from the German Devonian (17 mm across). Does anybody recognise this? Could it be Erbenoceras?
 

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Dr. Christian Klug identifies the specimen above as Gyroceratites and the Anetoceras is now renamed to Ivoites hunsrueckianum or perhaps Bovites. Thanks!

The phylogram below is from DE BAETS, K., KLUG, C. & KORN, D. (2009): Anetoceratinae (Ammonoidea, Early Devonian) from
the Eifel and Harz Mountains (Germany), with a revision of their genera. – N. Jb. Geol. Paläont. Abh., 252: 361–376.
 

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Here's a fine image to illustrate the "Devonian Nekton Revolution" in which the early ammonoids play a major role. It's from a new paper by Klug et al. (2009) and has the caption "Macroecological steps in the evolution of Palaeozoic marine food webs".

Klug, C., Kroger, B., Kiessling, W., Mullins, G.L., Servais, T., Fryda, J., Korn, D. & Turner, S. 2009: The Devonian nekton revolution. Lethaia, 10.
 

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Hi Kevin,

This is what they say about early nautiloids:
“Among the nautiloids, all nautiloids originating during the Cambrian, the Actinocerida, Ascocerida, Discosorida, Ellesmerocerida, Endocerida, Lituitida and Oncocerida are here considered demersal; this inference is based on the facies they occur in and morphological features such as coiling and position of hyponomic sinuses (Chen & Teichert 1983; Stridsberg 1985; Westermann 1999; Kroger & Mutvei 2005).”

On orthocerids: “Most orthocerids were probably capable of minor horizontal movements but they were ineffective swimmers and migrated predominantly vertically and/or drifted passively (Hewitt & Watkins 1980; Westermann 1999; Mutvei 2002; Kroger 2003, 2005; Kroger & Mutvei 2005; Mutvei et al. 2007). This is suggested by their poorly differentiated muscle-attachment structures, the absence of significant endosiphonal or endocameral deposits and, in some cases, also shell morphology.”

“The coiled Tarphycerida and Nautilida are interpreted as nektobenthic or nektoplanktonic based on actualistic comparision of the shell form, muscle attachment structures and position of the hyponome (Westermann 1999; Kroger & Mutvei 2005).”

Here below is how they assigned the different animal groups to "ecological megaguilds".

Don't know who the artist is, but I've asked.
 

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