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laying 1-7 eggs (or more) in nests on a rather flat land, such as sea-shores (Sanz et al., 1995),
tidal flats (López-Martínez et al., 2000) and beside estuaries, lagoons, marshes and fluvial
plains (Vianey-Liaud & Lopez-Martinez, 1997). Despite brood-care by the adults, the eggs
and the hatchlings were frequently exposed to potential predators and could be snatched
from the nest or consumed on site after the distraction of the parent. Dinosaurs and
pterosaurs living in this region were probably involved in the killing of their kind. This
common process among birds was suspected to have occurred in dinosaurs as indicated by
the name Oviraptor ='egg stealer', given to a dinosaur situated in an egg nest. Other
oviparous reptiles such as crocodiles, land lizards and sea-turtles hid the brood and only
experienced predators knew were to search for them, whereby most of the eggs hatched and
the young quickly looked for shelter. The marine reptiles gave birth to young which were
likewise vulnerable to predation at this stage as hinted by bones of small, probably young
mosasaurs in Upper Campanian sediments in southern Israel. The dinosaurian branch of
birds survived this predatory threat thanks to their rather small body, and hence their egg
size. These could be laid in nests high above the ground hidden in trees, in bushes or at
inaccessible sites such as on cliffs. The threat to the brood was thus minimized and restricted
to the few predators which could discover and reach these breeding sites. The extant large
ostrich exemplifies the mode of breeding of the dinosaurs on open ground whereby some of
the 10-12 eggs might be consumed by predators.
MacLeod et al. (1997) summarize the record of the Upper Cretaceous cartilaginous fishes
many of which survived into the Tertiary like many of the bony fishes. Among those which
became extinct are Enchodus and Stratodus. Enchodus species reached 1 m of length whereas
Stratodus species were over 3 m long (Lewy et al., 1992). These rather large bony fishes, as
well as most of the cartilaginous ones seem to have swum as individuals in contrast to
present-day small fish, forming vortex-like swarms, hence confusing predators. Thus the
surviving potential of these small fish is higher than of individual large ones, despite their
skills as vicious predators which could be overcome by larger sharks and by big marine
reptiles.
4.2 Cephalopods
Ammonites are another example of a large group seemingly to suddenly disappear at the
end of the Cretaceous Period like the dinosaurs. These conch bearing cephalopods
diversified during the Upper Cretaceous, providing excellent biostratigraphic markers.
Ammonite species gradually disappeared during the Upper Maastrictian, with 12 reaching
close to the K-T boundary in the section exposed in northern Spain, in which other species
disappear in groups or individual species during the Upper Maastrichtian (Marshall &
ward, 1996). This is probably the most complete latest Cretaceous sedimentary sequence
with ammonites. The simultaneous disappearance of twelve species close to the K-T
boundary gives the impression of a catastrophic event that killed all ammonites in this area
and seems to corroborate the total elimination of the order Ammonoidea throughout the
world.
Lewy (1996, 2002a, b) analyzed the functional morphology of ammonites (ammonoid
conchs), especially of heteromorphs, but also of the planispirally coiled ones. Most of the
heteromorph ammonites (except for the Baculitidae) developed a U-shaped terminal whorl
with an upward facing aperture, which in some species was partly occluded by the previous
whorls. Some planispiral ammonites changed the shape of the last whorl, inflating it and
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