Palaeontological Institute and Museum

The generally accepted theory of a U-mode sutural ontogeny of prolecanitid ammonoids and their descendants is refuted. The basic suture formula of the order Prolecanitida is E A L U I (not E L U2  U1 I), resembling that of derived members of the suborder Tornoceratina (their phylogenetic ancestors), and of the suborder Goniatitina. During phylogeny of the prolecanitids, secondary umbilical lobes are introduced and lead to multilobate forms. In early ceratites, the original L lobe disappeared, and an increase in sutural elements took place by the introduction of supplementary U lobes. Consequently, sutural nomenclature of Permian ceratites and Mesozoic ammonoids has to be modified.

"Exceptionally preserved specimens of the genera
Myophoria, Neoschizodus and Trigonodus (Bivalvia, Palaeoheterodonta,
Trigonioida) from carbonate sediments of the
Muschelkalk (Anisian, Ladinian) contain phosphatized softtissues.
This is the oldest record of soft-tissue preservation in
bivalves and the first from the German Muschelkalk. The
phosphatized remains are here interpreted as relics of the
originally chitinous gill supports, the gill axis, the labial palps
(?), the adductor muscles, the pedal retractor muscles, the
mantle margin including the radial mantle musculature, and
the ‘siphons’. According to microprobe analysis, the mineral
replacing the soft-tissue is mainly apatite and, more rarely,
francolite. Additionally, quartz filled voids within the gill
supports, and in one sample it occurs in minute crystals in
the phosphatized remains of the adductor muscle of Neoschizodus.
Myophoria, Neoschizodus and Trigonodus were softbottom
dwellers and five of the specimens were discovered
in life position. This is indicated by geopetal structures in
three specimens."

"For a stratophenetic analysis of Middle Triassic ammonoids from the German Muschelkalk (Anisian, Ladinian), whorl
expansion rates, whorl width indexes, umbilical width indexes, maximal conch sizes, body chamber lengths, the orientations of
the aperture, and a number of sculpture parameters of approximately 500 specimens were identified. 274 of these data sets,
sorted according to their stratigraphic age, were evaluated in scatter plots as well as canonical discriminant function analyses.
Several of the diagrams that were produced in these analyses reflect more or less steady changes in conch morphology through
geological time, except for some intervals with abrupt and rather drastic transformations. These morphological discontinuities
are synchronous with immigrations into the Germanic Basin of crinoid and brachiopod taxa. This discovery indicates
disturbances in the endemic evolution of the ammonoids caused by such immigrations. At a small scale, this case study
demonstrates that a rising sea level may have boosted the faunal exchange between an open marine and a restricted
epicontinental basin, causing a minor regional increase in biodiversity. It also demonstrates that the evolution of dGermanicT
ceratites happened mainly within the Germanic Basin but partially probably also within the Tethyan Sea. The ecology of the
ceratites from this Basin is discussed. Accordingly, they were stenohaline, good backward swimmers with a good
manoeuvrability, and able to achieve neutral buoyancy."

Palaeozoic and Mesozoic cephalopod conchs
occasionally reveal dark organic coatings at the aperture. A
number of these coatings, including still unrecorded examples,
are described, figured and interpreted herein. On the
basis of elemental analysis, actualistic comparison and a
comparison with Triassic bivalves, some of these coatings are
shown to consist of apatite and primarily probably of
conchiolin (and also probably melanin). In several Mesozoic
ammonoid genera such as Paranannites, Psiloceras, Lytoceras,
Phylloceras, Harpoceras and Chondroceras, some of these coatings
(recorded herein for most of these taxa for the first
time) are interpreted as a structure similar to the black band,
which was previously known only from Recent Allonautilus
and Nautilus. In contrast to these nautilid genera, however,
the organic material of some Mesozoic ammonoids was not
deposited on the inside of the shell but externally, albeit
positioned at the terminal aperture as in Recent nautilids.
Some ammonoids of Carboniferous and Triassic age show
several such bands at more or less regular angular distances
on the ultimate whorls and at the aperture, e.g. Nomismoceras,
Gatherites, Owenites, Paranannites, Juvenites and Melagathiceratidae
gen. et sp. nov. Triassic material from Oman
shows that the black coating was probably secreted from the
inside, because the position of this organic deposit changes
from interior to exterior in an anterior direction (i.e. adaperturally).
This structure has previously been referred to as a
‘false colour pattern’ and is here interpreted as having been
formed at an interim aperture or megastria (‘alter Mundrand’).
All structures discussed in the paper are considered
to have been secreted by a single organ and to have been initiated
by some form of stress or adverse conditions. Thus,
certain environmental parameters and growth anomalies
appear to have influenced their formation.

Soft-tissue attachment structures were found in various molluscs from the marls and limestones of the German Muschelkalk (Anisian, Ladinian). For instance, bivalves often display the sites where the adductors and the pallium were attached (e.g., Klug et al., 2005). For the nautiloid Germanonautilus, Klug and Lehmkuhl (2004) documented the attachment scars of the cephalic retractors which sometimes are preserved in great detail. Although representatives of the Ceratitida are very common (at least in some beds of some localities), soft-tissue attachment sites have never been described and figured previously. Muscle attachment scars (the dorsal and ventral scars) were listed as “unpublished observations” by Doguzhaeva and Mutvei (1996: 54), but, as far as we know, they never published these “observations” in greater detail.