We all know the story: 65.5Ma, the dinosaurs became
extinct (except for the ones that survived), and the world was at last
liberated from the cold, scaly monarchy of reptiles. Hooray!
This wasn’t the case. At all. First of all, dinosaurs are
warm-blooded, and secondly, in the ten-million-year period following the
extinction of the non-avian dinosaurs, the world was still, in some areas, home
to truly enormous reptiles. The Cerrejon Formation of Colombia, dating back to
the Paleocene epoch, preserves an otherworldly environment in which giant
snakes, turtles, and crocodilians ruled the landscape, and this formation has
drawn much attention from its abundance of tremendous scaly beasts.
While the wildlife of the Cerrejon Formation is no doubt
amazing, the ecological importance of the 58-million-year-old formation is
often overlooked. The various fossilized plants, leaves, and evidence of
herbivorous insects represent the earliest known record of modern Neotropical
rainforests. The families of plants that have been found, including various
palms and legumes, can still be found in the Amazon Basin. Though they were
present in the Paleocene, they are far more diverse today; this may be due to
the fact that the earth was still in recovery from the latest mass extinction
at the time the Cerrejon was formed. It may also be due to the fact that the
Cerrejon represents a wetland, rather than a rainforest, environment; wetlands
generally host a lower diversity of plants than forests. (Gomez-Navarro et. al, 2005)
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| Titanoboa cerrejonensis, a dyrosaurid, and a giant turtle: the scaly, cold-blooded overlords of the Cerrejon Formation. Reconstruction by Jason Bourque. |
Mean annual temperature (MAT) and mean annual precipitation
(MAP) estimates are somewhat varied. Some authors suggest a balmy temperature
of greater than 28C (~82F), with an average of 2,500mm (~8ft) of rainfall
annually. (Gomez-Navarro et. al, 2005) Others suggest a slightly cooler MAT of 24C (~75F) and still higher
rainfall levels of 3240mm (~11ft). (Herrera et.
al, 2005) These figures were calculated using a method known as leaf-margin
analysis: the number of angiosperm species with toothed leaves is inversely
proportional to the MAT. Therefore, the greater percentage of untoothed leaves
that are present in any environment, the higher the temperature is likely to
be. (Niinemets et. al, 2012) Untoothed
angiosperms make up anywhere from 74-78% of fossilized leaves recovered from
Cerrejon, implying a high MAT for the local environment.
Scaly Monsters and
Serpent Freaks
These early Neotropical wetlands of Colombia, at the
northern tip of the ancient island of South America, were home to a host of reptiles.
The high temperatures and humid environment favored the cold-blooded creatures
and, because no large mammalian or avian predators had evolved yet, some of
these grew to outrageous sizes.
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| A life-sized model of T. cerrejonensis swallowing an unfortunate dyrosaurid, with artist Kevin Hockley. Photo by Robert Clark. |
In 2009, one particular species made headlines, breaking
all kinds of records as the world’s largest, longest, and heaviest snake: Titanoboa cerrejonensis, a name that
needs no explanation. Twenty-eight specimens of T. cerrejonensis were uncovered from the coal mines of the Cerrejon
Formation, and the largest of these measured up to 15m (~50ft) long and tipped
the scales at 1,135kg (~2,500lb).
This huge serpent was the apex predator of its
environment, and, like the closely-related anacondas, hunted a variety of animals,
including fish and crocodilians. As a boid, the family of snakes which includes
boa constrictors and anacondas, T.
cerrejonensis used its bulk and muscle to subdue its prey. With an
abundance of large-bodied reptiles in the area, it was likely a specialist in
hunting local dyrosaurids, as well as various species of lungfish and other
large fish in the waterways.
Check back soon for the next installment of this small series, in which we will take a look at the specialized dyrosaurids of the Cerrejon.
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