The second group of extinct animals to warrant a special investigation in the light of the quadralectic approach to history are the Ammonites. The Ammonoidea is the largest and most important subdivision of the Class Cephalopoda, which includes the modern squids, cuttlefishes and octopu-ses. The Ammonites derived their name from the Egyptian god Ammon, with ears in the shape of ram’s horns. The predecendants of these versatile sea animals were one of the first types of fossils, which attracted the interest of early naturists (fig. 70).
Fig. 70 – This illustration of some Ammonites or ‘snake stones’ (Cornus ammonis) was given in Robert Hooke’s book ‘Discourse on Earthquakes’ (1703).
(France). (Photo: Marten Kuilman, May 2006).
The earliest known ‘ammonoid’ (Eobactrites) occurred in rock layers from the Ordovician age (505 – 440 million years ago). This genus was the proto-type of a major development of the subclass, which started in the Upper Silurian and the beginning of the Devonian, some 395 mya. Ninety genera appeared in fairly short time.
The difference (in time) – 45 mya – between the first and the massive visibility poses a classical problem in the quadralectic approach to history. The question is: do we focus on the first occurrence of Eobactrites in the Ordovician as the beginning of the (empiric) visibility of the ammonites or do we concentrate on the (sudden) presence of many ammonoid genera after the Silurian-Devonian boundary?
The same question might be posed in a general way: is the visible visibility governed by the boundary of the first sighting (of a single item) or does the empirical existence start at a point when a widespread occurrence is evident? Anybody who has experience in the arduous task of observing nature – be it of fossils, plants, birds, butterflies or any other object of interest – will be familiar with the problem of scarcity. Things can be rare, on a given place and at a particular time. However, once a singular item of interest has been located – by chance or in a combined effort of specific observation and knowledge – then it is often not uncommon at all.
This observational problem is created in the tension between the single and the multitude. It is, for this reason, related to quadralectic division problems and the position of the observer therein. The answer to the dilemma of the separation between the one and the many must be clear. It all depends on the location of the observer who defines the boundaries in the first place. The observant individual is either situated in the Third Quadrant (III) in absolute surroundings or in the third quarter of the Fourth Quadrant (IV, 3) with knowledge of a subjective intervention.
Both positions of observation have their own merit. None is better than the other. The first view is precise, but limited, while the other perception is sometimes vague, but applicable in a wide field. We are inclined, as explorers of a quadralectic vision, to choose for the latter option and its associated dynamism. Even so, we must be conscious all the time, that the preference for the multitude (in a delineation process) is a choice.
The ammonoids found their demise at the end of the Cretaceous, together with the Dinosaurs. The reasons of their disappearance might have been the same: the mass extinction due to a meteorite or comet, which struck the earth and disturbed the ecological circumstances for a long time. Other possibilities, less fearsome in their immediate effects, like the changes in temperature or large-scale volcanism (as seen in the Decan Traps in India) which influenced the composition of sea and air – have to be taken into account. The explanation of the extinction (of the Dinosaurs) as a ‘catastrophic’ Third Quadrant event (extraterrestrial intervention) or as a gradual Fourth Quadrant episode is also a philosophical one, based on a personal point of view.
The actual mechanism of the Ammonites extinction is, at present, not of our concern, because we are only interested in the total time-era of (visible) visibility of the subclass of Ammonoidea. Scientific facts and the definition of our position as observer (the choice for multitude) fix the boundaries of the visibility area between 395 and 65 million years ago. The total visible visibility period (X) is therefore 330 million years.
The theoretical base of the CF-graph (V = 8/5.X) can be calculated in the same way as the Trilobites. The Ammonites have a total muun-length (V) of 528 million years, which is slightly less than the Trilobites. The length of a basic unit (BU) between two points of inflection (1/16th V) is computed for the Ammonites as 33 million years.
10 8
X = ——— . V = 330 my V = ——— . 330 = 528 my
16 5
1
BU = ——— . V = 33 my
16
The inflection points in the CF-graph for the Ammonites can be calculated when the basic unit (BU) and the First Visibility (FV) are known:
X = – 395 Y = 11.00 (FV) X = – 197 Y = 13.00 (SVC)
X = – 362 Y = 11.00 (AP) X = – 131 Y = 6.00 (SMA)
X = – 329 Y = 6.00 (FMA) X = – 98 Y = 11.00 (RP)
X = – 263 Y = 13.00 (FVC) X = – 65 Y = 11.00 (LV)
X = – 230 Y = 10.00 (PP)
The abbreviations of the inflection points on the CF-graph are as follows (in the general appraisal of the graph, see p. 122, fig. 51): FV = First Visibility; AP = Approach Point; FMA = First Major Approach; FVC = First Visibility Crisis; PP = Pivotal Point; SVC = Second Visibility Crisis; SMA = Second Major Approach; RP = Receding Point and LV = Last Visibility.
The history of the subclass Ammonoidea (of the Class Cephalopods) is now examined in quadralectic terms and compared with the more traditional (scientific) descriptions. The subclass is regarded as a unity (in time), which follows the rules of the universal communication (graph) expressed in an approach (intensio) and/or alienation (remissio) (fig. 71).
Fig. 71 – The visible visibility period (X) of the CF-graph for the extinct subclass of Ammonoidea, which lived from the early Devonian to the end of the Cretaceous, i.e. from around 395 to 65 mya., a time span of 330 million years.
The Approach Point (AP) marks the end of the primary visibility equilibrium of CF = 11 and is situated in time around 362 mya. This period is known on the geological time scale as the Upper Devonian (Givetian – Frasnian and Famennian). It was a time with a greenhouse climate, a high sea level and the development of vast carbonate platforms with extensive reef constructions. Locally, there were (evaporite) basins amidst deep rifts associated with volcanism. The large oil and gas reserves of the North Caspian Basin are situated in these rocks (CLARKE, 2000).
One of the major ‘catastrophes’ of the earth history happened in the Upper Devonian when most of the reefs were wiped out in the latest Frasnian. Organic carbon-rich sediments with debris from the continental forests did affect the shallow-water ecosystems. The deeper water Nautiloides, Orthoceroids and Ammonoides escaped the impact of these events.
The First Major Approach (FMA) took place at the end of the first quarter of the Carboniferous (395 – 2 x 33 = 329 mya). Here the maximum approach (and possibilities) in the communication was reached. The maximum intentio is situated on the geological time scale at the boundary between the Lower (Mississippian) and Upper (Pennsylvanian) Carboniferous. In particular the Goniatites – cephalopods with a simple infolded chamber wall (sutures) – developed into a large variety of forms. A new group with so-called ceratite sutures arrived in the Mississippian (Lower Carboniferous). The ceratite suture was characterized by a smooth rounded saddle and crinkled lobes. Their existence reached a maximum in the Triassic (the genus Ceratites is a typical example). The latter geological period (Triassic) has been called the ‘Age of the Ceratites’.
The Ammonites sensu stricto – distinguished by complex infolded chamber walls – first appeared in the Pennsylvanian Period (Upper Carboniferous). This geological era is known for its large quantities of coal. The surplus of carbon was derived from tropical forests, which kept on growing due to favorable biological, climatological and tectonic circumstances.
The First Visibility Crisis (FVC) was around 263 mya, at the beginning of the Perm. This picture of ‘crisis’ fits pretty well, because the Permian was – in general – rather hostile to the marine life. Sea level dropped, and continental movements became important. Some of the ammonites had a hard time in the changing environment, with locally developed into shallow seas with high concentrations of copper and salt (Zechstein). The ancient crustal cores of the Southern Hemisphere (Brazil, Africa, India, Australia and eastern Antarctic) had emerged from the Silurian-Devonian seas as a new continent called Gondwanaland. A large glaciation took place here during the Upper Carboniferous and Permian.
The folding of the inner septa (chamber walls) – visible as the curled sutures – continued to prosper in the surviving ammonites, but there was little sign of decorations of the outer shell. It was only after the turn of the Paleozoic into the Mesozoic (245 mya) that new shapes and design could develop.
The Pivotal Point (PP) in the visibility area of the Ammonoidea was situated in the middle of the Triassic Period (230 million years ago). The earlier mentioned Ceratites, with highly decorated shells, had their hey-days. The old Nautiloids, which first appeared in the Cambrian Period with smooth, gently infolded chamber walls, relived palmy days for the second time. The expansion was, in hindsight, a rearrangement of the deck chairs on the Titanic: both the Nautiloids and the Ammonoids nearly died out at the end of the Triassic (210 mya). The former only continued with a single species (the present day Nautilus). The latter started their development all over again from simple basic forms (taken from the surviving Phylloceras and Lytoceras) into forms with very complicated sutures (lobes in the chamber walls).
The Second Visibility Crisis (SVC) at 200 mya – a mere 10 million years after the events at the Triassic-Jura boundary – contained all the drama of these times of change for the Ammonites. Melting glaciers and large-scale magmatism caused a continuous changing landscape. The pattern of transgression and regressions – as it reflected in the deposits of the Triassic (a name pointing to the triple division: Buntsandstein – Muschelkalk – Keuper) – continued into the Jurassic. After a severe regression (in the Upper Triassic or Rhaetium stage), the Jurassic was again a period of transgression. Newly flooded parts of land offered rich, relative shallow seas. The adventurous Ammonites had to adapt to these sea level changes, and they did so brilliantly, becoming the leading time-indicating fossils of the Jurassic Period (210 – 145 mya).
The ‘Golden Age’ of the Ammonites was the beginning of the Jura period, which was also in other respects a time with a rich fossil record (fig. 72). The small Foraminifera (plankton) staked their claim as widespread index fossils from the Jurassic onwards. Reef building was as important in this epoch (particular in the Malm) as it was in the Silurian, Middle Devonian, Lower Carboniferous and Middle Triassic.
Fig. 72 – Ammonites of the Lias (Lower Jurassic) showed a rich variety of ornaments and complicated sutures. Still, their survival had only some millions years earlier hung in the balance, when nearly the whole population of Ammonoidea died out. The Second Visibility Crisis (200 mya) coincided, within a margin of 10 million years, with the boundary between Triassic and Jurassic, when these radical changes occurred.
The Second Major Approach (SMA) took place some 135 million years ago, at the beginning of the Cretaceous (145 – 65 mya). The Ammonites touched their basic existence (as a subclass) in an environment, which mirrored the desirable settings of the Jurassic Period. Further expansion of the (Upper) Cretaceous seas offered more space for development. The great transgression of seas in Europe had submerged lands that had not been covered by water since the Palaeozoic.
A large transgression, known as the Comanchean Sea, spread in the Lower Cretaceous over the southern states of northern America. Later, in the Upper Cretaceous, the Colorado Sea extended even further from Mexico up into the Arctic. These circumstances were favorable for the Ammonites and they proliferated in a wide variety of forms.
The Ammonites were finally caught up in the mass extinction at the end of the Cretaceous. This event at the K/T (Cretaceous-Tertiary) boundary killed about seventy-five percent of all species, including marine, freshwater and terrestrial organisms. The mass extinction included all the Ammonoids and Belemnoids, large groups of organisms such as Foraminifera, Echinodermata and Molluscs, flying reptiles (Pterosaurs) and the complete wipe-out of the Dinosaurs.
Fig. 73 – The number of Ammonoid families and superfamilies during their existence on earth from the Lower Devonian to the Upper Cretaceous, i.e. from around 395 to 65 mya.
The evolution of the Ammonoids was not a gradual affair, as will be clear from the graph in fig. 73 (the number of families and superfamilies are adapted from MOORE (1959/1997) and CLARKSON (1979). It is a history of successes and disasters in what may be called a ‘paleontological relay’. The ancestral stock gave from time to time rise to short-lived groups, which replaced each other in due course. This picture, as observed here within one subclass, might be the blueprint for the evolution of the Large Visible Animals (LVA) as a whole.
The Ammonoids (as the Trilobites before them) have been so important because they provided a marker point in the geological history and a subsequent scale of measurements. The end of these flexible groups, which nearly died out at earlier occasions, brings about the real character of visibility. A suture or break in the unity of life (because a species or group vanished from the earth) calls for a choice. The disappearance of the Ammonoids (and all other extinct species) from view – for whatever reason – will lead, if nothing else, to the notion of a boundary. The nature of this distinction, as interpreted by the observer in a particular division setting, will eventually contribute to the insight of visibility-in-general.
Life on earth is a matter of coming and going, trying new chances, adapt to changes or simply disappear altogether. Existence is a moment in space and part of a specific communication. The fact that certain life forms have disappeared only proves that they have left the visible visibility area of a communication cycle between Man, as the observer, and the earth, as it is known here and now. It could mean that their existence continues – this very moment – in other communication cycles between other participants. This prospect means that nothing is lost forever.
Visions of Four Notions 