Soft–part preservation in heteromorph ammonites from the Cenomanian–Turonian Boundary Event (OAE 2) in north–west Germany

Abstract

From thinly laminated marlstones of the Hesseltal Formation, representing the Late Cenomanian Oceanic Anoxic Event (OAE) 2, at Lengerich in the Teutoburger Wald (Westfalen, north‐west Germany), 17 sediment‐compacted baculitid ammonites with carbonised and partially phosphatised soft parts are recorded. Some preserve remains of the buccal mass, including jaws (occasionally articulated) and radulae, as well as of the cephalic cartilage, such as eye capsules. Such have not yet been recorded previously for the order Ammonoidea. In addition, originally unmineralised parts found preserved in these specimens include extensive portions of the digestive tract, the siphonal tube, false colour patterns (megastriae), as well as traces of what would appear to be the oviduct. At the same levels, patches with numerous isolated horny upper and rarer lower jaws as well as radulae occur; these may represent regurgitates or faeces of larger predators. The cephalopod remains described were deposited in an epicontinental setting, possibly at palaeodepths between 200 and 600 m. In this particular Late Cretaceous fossil Lagerstätte, upper jaws and anaptychi of ammonites rank among the commonest fossils.

Mature Modifications and Sexual Dimorphism

“…Ammonoid eggs have been reported by several authors (Lehmann 1966;Müller 1969;Zakharov 1969;Maeda 1991;Urlichs 2009;Etches et al 2009;Landman et al 2010;Klug et al 2012). In spite of these findings, there is as yet no report of a discovery of eggs within an ammonoid shell that is free of doubt (De Baets et al 2015b).…”

“…In the baculitids, the adult modifications are usually limited to changes in ornament (stronger ribs on the venter), sometimes a slight dorsal turn of the aperture and dorsal as well as ventral lappets (Kennedy 1988;Cobban and Kennedy 1991c;Klug et al 2012). The ventral projection or rostrum can be rather long, clearly exceeding the shell diameter.…”

Ammonoid Intraspecific Variability

“…Intraspecific variation also occurs in the shape or position of the suture line (e.g., Yacobucci and Manship 2011) or in dextral or sinistral coiling of the conch (e.g., Matsunaga et al 2008) as seen in extant gastropods. Ammonoids might also have differed intraspecifically in colour patterns (e.g., Mapes and Sneck 1987;Bardhan et al 1993; see also Mapes and Larson 2015), buccal mass (Davis et al 1996;Keupp 2000;Keupp and Mitta 2013;compare Kruta et al 2015) or other characteristics which are rarely or not preserved at all such as soft-tissues (Klug et al 2012) or other peculiar structures (Landman et al 2012). We will herein focus on intraspecific variation in shell shape, ornamentation and size, as well as spacing and shape of the septa (suture lines), for which more data are available.…”

Non-invasive imaging methods applied to neo- and paleo-ontological cephalopod research

“…Much has been improved since the earliest attempts, invasive or not, for 3-D reconstructions of fossils and their internal structures (Sollas and Sollas, 1914;Tipper, 1976;Luo and Ketten, 1991;Herbert et al, 1995;Hurum, 1996;Stock, 2006;Tafforeau et al, 2006;Sutton et al, 2001, Hoffmann and Zachow, 2011;Falkingham, 2012). Specifically for cephalopods non-invasive methods were used lately for reconstructing internal soft parts, mainly buccal masses of ammonoids, e.g., Klug et al (2012), Kruta et al (2013Kruta et al ( , 2014, and Tanabe et al (2013), and were also used on extant cephalopods, e.g., Westermann et al (2002) and Kerbl et al (2013). Recently, Sutton et al (2014) published an extensive overview of techniques for virtual paleontology, including destructive and non-destructive approaches.…”