"Prehistorical animals – Thalassocnus"
2485, Bl. 70
Alvarez M. –SERPOST S.A.
on stamp and reconstruction in block margin
(width x height)
||30mm x 40mm
with 1 stamp
||Thomas Grag and Sons –
||Servicios Postales del Peru SA
In 2010 the Post Authority of
Peru - Servicios
Postales del Peru SA - continue to show natural
heritage of the country discoverdon their stamps. This year a
block depcted scientific
reconstruction and fossil of prehistoric sloth - Thalassocnus
is added to "Prehistoric animals"
Prehistoricos - Fosiles) set started in 2004.
you think of marine mammals, sloths are probably the last thing you’d
expect to take to the water. But from the late Miocene (7-8 million
years ago) to the late Pliocene (3-1.5 million years ago), several
species of giant ground sloths in the genus Thalassocnus
did indeed evolve to take advantage of the aquatic environment. However
even some modern slots can swim.
"If there is something amazing about
paleontology it is a capacity to show us that the life on the
Earth, such as we know it nowadays, is the result of constant changes.
Even the English
naturalist Charles Darwin sketched his primordial ideas about the
biological evolution inspired by fossilized bones of giant sloths and
the ancestors of little tree sloths and armadillos in South America.
evolution –developed 150 years ago in Darwin’s “The origin of the
concept that integrates all the sciences of life, now with the help of
and molecular biology. Like in Darwin’s time, fossils are the most
resource for the evolution.
of years ago, the
area of Sacaco, north to Arequipa, was a littoral marine environment.
sands lie hundreds of fossils of whales, dolphins, seals, penguins and
in excellent state of preservation. In 1967, french paleontologist
Hoffstetter visit the area, and was greatly surprised to find
terrestrial intruder: a sloth between
inicially assumed that the sloth lived on land, near the littoral.
that their bodies were dragged into the sea by an andian paleo-river,
they were buried and preserved with aquatic species. However, something
wrong: the skeletons were always found articulated and complete, as if
in the same place of their death - in the sea. What if it really was
sloth? This possibility, though wild, encouraged paleontologists
Muizon and Greg McDonald to observe every bone's detail to look for
clues. In 1995, Muzion and McDonald announced in Nature Magazine, the
of a 4 million year aquatic sloth in Peru.
Some details of its anatomy,
the shape of the premaxilla,
and caudal vertebrae (the bones that make up the tails of
tailed animals) , are
certain aquatic mammals that to others extinct sloths. Various
almost 15 years and many
dicoveries made by Mario Urbina, 5 species of the aquatic sloth
were described, all of them found in marine deposits nearby Sacaco,
rocks belonging to succesive epochs from 9 to 2,5 million years ago.
record, let us track the first splashes in its linnage evolution, and
observe the way that certain adaptations to the aquatic environment
progressevely accentuated through time. Thalassocnus was a sloth the
size of a
large dog, with long tail and powerful claws. It had simple teeth with
enamel. Since the most ancient species (Thalassocnus antiquus) to the
modern (Thalassocnus yaucensis) several changes were observed,
increase in the length and width of the muzzle’s previous region,
obtaining aquatic grass as a new source of food. The radius
substancial differences in the locomotion way. While Thalassocnus
a long radious bone with a reduced supinator crest, typical of
Thalassocnus yaucensis the radius bone
is short and the supinator crest is
developed as observed in seals and sea lions. Today there is no doubt
Talassocnus was an aquatic sloth which spent a long time feeding into
but what could have impulsed it to leave its quiet life on land to
amongst waves infested with sharks? Good question. It is known that the
peruvian coast was already desertic in that epoch. Possibly the scarce
vegetation in the coasted desert lead to the search of an alternative
in the beached algae during low tide. After many generations, some of
adventured to look for algae and marine grass into the sea. As this
strategy was good enough, those individuals who had small anatomical
to live and feed in the sea –therefore the more suitable - had more
opportunities to reproduce and fix its genes in their offspring. The
of evolution proposed by
selection- was on the road.
2008, we published, with
colleague, at the Journal of Vertebrate Paleontology, the first remains
Thalassocnus discovered outside of Sacaco, almost 1500 km away, on
marine origin in Bahia Inglesa (English Bay), in the north of Chile.
us think that Thalassocnus dominated a vast littoral territory of
ecological characteristics. As we can imagine their bones were found
whale and dolphin remains. Recently, new Thalassocnus remains were
Ica, 180 km north to Sacaco.
evolutive travesy of
sloth Thalassocnus finished 2 million years ago. The bays of quiet warm
that existed for millions of years, made a way to a lineal coast of an
sea, just like we know it today. The wide cover of sea grass
the Thalassocnus’ linnage was extinted. Instead, other terrestrial
evolved to become the largest mammals that lived in South America."
Salas Gismondi. Curator. Verbratete
Department. Natural History Museum. UNMSM.
Many thanks to fellow stamp collector Romina Aimar from Argentina , for her help in translation of original text from Spanish to English
Latest update 21.11.2017
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