Ammonoid Taphonomy

Ontogenetic trajectories of septal spacing in Early Jurassic belemnites from Germany and France, and their palaeobiological implications

“…; Hoffmann et al . ) its fossilization potential seems to be relatively high (see also Wani & Gupta ). On the other hand, the phragmocone was originally composed of aragonite (Hall & Kennedy ; Price et al .…”

Ammonoid Intraspecific Variability

“…However, some evidence suggests that variances within fossil samples are not necessarily dominated by time-averaging (Tintant 1980;Hunt 2004a, b). Well-preserved specimens, particularly those with in situ buccal masses, as well as the lack of preferred orientation, size distribution and other biostratinomic data have been used to support lack of (strong) condensation or (long) transport (compare Wani and Gupta 2015). Not only animals that lived during different times, but also organisms coming from various depths (i.e., living in different parts of the water column or at different seafloor depths) might be mixed within these assemblages, particularly in pelagic shell assemblages, which can also be related to post-mortem floating or transport of their shells.…”

“…Not only animals that lived during different times, but also organisms coming from various depths (i.e., living in different parts of the water column or at different seafloor depths) might be mixed within these assemblages, particularly in pelagic shell assemblages, which can also be related to post-mortem floating or transport of their shells. Taphonomic studies can be important to disentangle different post-mortem histories of shells within the same fossil sample and can also give information on the faunal succession (Fernández-López 1995Wani and Gupta 2015). However, it is not generally true that less well-preserved shells are older-their preservation mainly depends on how much time they spent on the sea bottom (or afloat) and the degree to which they were subjected to diagenesis during burial as well as 9 Ammonoid Intraspecific Variability in which paleoenvironments they resided (e.g., Flessa et al 1993).…”

“…The appearance of ornamentation and measurements of the same parameters might differ between differentially preserved specimens (internal moulds vs. shell preservation). Furthermore, fossils can be extremely compacted in some lithologies, particularly in shales, which might lead to the increase of the whorl height and diameter as well as a decrease of whorl thickness and umbilical width (e.g., Morard 2004;De Baets et al 2013b;Wani and Gupta 2015). These effects could even lead to the erection of endemic "species" restricted to certain lithologies (see De Baets et al 2013b for such a case in the early Emsian ammonoid Ivoites).…”

Discovery of Ammonoid Jaw Apparatus and Associated Features Using Reflectance Transformation Imaging (Rti)

“…Therefore, the functionality of the buoyancy apparatus might be more affected or completely lost as shown by Tsujino & Shigeta (2012). So, in a hypothetic scenario, the phragmocone was perforated and filled with seawater; in this state, the organism could not have retained its neutral buoyancy (Maeda & Seilacher, 1996;Tsujino & Shigeta, 2012;Wani & Gupta, 2015) and eventually succumbed (i.e., by starvation, hypoxia, or thermal and/or osmotic shock). The ballasting would not have allowed postmortem transport enabling the retention of the structures observed on the specimen (Yacobucci, 2018).…”