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asteroid impacts (Keller, 2008) would have had little contribution to the gradual collapse of
Earth's biological systems.
7. Early Tertiary biological recovery
The Deccan volcanic activity extended into the lowermost Tertiary (~64.8 Myr; Keller et al.,
2009) and thereafter the climatic and ecologic systems began their recovery. Small
globigerinid planktonic foraminifera survived the end-Cretaceous biological crisis and
appear in Early Paleocene sediments (e.g., Orue-Etxebarria & Apellaniz, 2000). Their
trochospiral coiling with 4-7 nearly globular chambers in the last whorl resembles other
associated species such as
Parvularugoglobigerina eugobina
(Olsson et al., 1999). This general
shape and size has neen observed in one of the earliest planktonic foraminifer from the
Lower Jurassic (probably Hettangian; ca 190 Myr) of Hungary (Görög, 1994). Keeled
planktonic foraminifera appeared in the Upper Albian (
Rotalipora
) about 90 Myr later
(Leckie, 1987). The earliest Tertiary keeled (pseudo-keel) planktonic foraminifer [e.g.,
Morozovella angulata
(White)]
appeared at the base of the Upper Paleocene (Thanatian, 58.7
Myr) about 6 million years after the recovery of the ocean ecological setting. This rapid
introduction of the keel structure among pelagic foraminifera suggests that the survivors in
a 'primitive' appearance preserved in their genome the ability to secrete keels and other
morphologies under suitable conditions. The relative quick recovery of planktonic
microorganisms after their near elimination at the end of the Cretaceous Period explains the
similar recovery of life in the marine and terrestrial bioprovinces. Many Late Cretaceous
species retreated to small-restricted niches protected from the side effects of the Deccan
volcanism. They continued living in these numerous small habitats, adapting to the
restricted ecological settings and thereby gradually changing their physiology, anatomy and
the skeleton. With the recovery and stabilization of the ecological systems all of these
'hidden' communities tried to enter and adapt to the physical and chemical conditions of the
open-large habitats and share the environment with other communities. Only those which
succeeded to accommodate themselves in these extensive bioprovinces in large populations
were discovered. The fossil record of all earlier small communities which lived in restricted
areas is still missing, giving a misleading impression of a big hiatus in taxa ranges and
sudden first appearance of new ones. These are actually members of evolutionary lineages,
of which the earliest Paleocene ancestors have not been yet discovered. This all took part in
an evolutionary biological continuum from the latest Mesozoic into the Cenozoic. The
technical comparison of taxa names between these eras intensified the apparent catastrophic
aspect of the end-Cretaceous biological crisis, being erroneously referred to a
mass
extinction
.
8. Conclusion
Sunlight screening by volcaniclast dust from the Deccan volcanic eruptions blurred the
distinction between annual seasons and disordered the biological clock of organisms and
plants on land and in the sea. Flowering plants produced less fruits for vegetarians,
reducing their birth-rate. The disturbed sexual cycle of carnivores likewise lowered their
birth rate and drastically reduced the amount of food (eggs and young born), on which
adults depended for feeding themselves and their young ones after a long period of near
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