100M year-old ammonite found in Catanduanes

March 29, 2010 11:34 pm 

By Danny O. Calleja

VIRAC, Catanduanes, March 29 -– A joint teams of Filipino and Japanese scientists has discovered here ammonite fossils described to be 100 million years old and first of its kind found in Southeast Asia.

Found at the Silungan ng Higante site deep in the forest of Dugui Wala in Barangay San Vicente of this capital town, Dr. Yasanuri Shigeta of the National Museum for Nature and Science (NMNS) in Tokyo, Japan said over the weekend that they found nine ammonite species in the area.

The most important among these species, Shigeta said, was the Mortoniceras being the first found in Southeast Asia.

Although the specie is believed to be widely distributed in North America, Japan and India, Shigeta said, none had been found in those areas.

"Mortoniceras is an index ammonite, meaning its presence would indicate the age of the rock it is embedded in as about 100 million years old or in the Cretaceous period," the Japanese scientist said noting that his team would be the first to study it.

He also said that the ammonites recently found in Mansalay, Mindoro was about 160 million years old (Jurassic period) while those found in Comagaycay, San Andres, Catanduanes were 110 million years old.

Dr. Shigeta was with NMNS curator-in-chief Dr. Tomoki Kase, when they joined the exploration team composed of Dr. Yolanda Aguilar, Wenceslao Mago, and Emolyn Azurin of the Mines and Geosciences Bureau (MGB).

Also part of the exploration team that made the search from March 15 to 18 were MGB geology division chief Roberto de Ocampo and curator Priscila Ong of the Philippine National Museum.

The undertaking was in connection with a joint research project on "Collection Building and Natural History Studies in the Philippines: Tracing the Origin of High Marine Biodiversity in the Indo-Pacific through Fossil Studies", Ong said.

The team was guided by Virac personnel officer Oseas Alberto who first discovered the ammonite site by accident while on a trek to get samples of small endemic fishes in mountain streams and rivers for possible breeding purposes in 2007.

A local newspaper, Catanduanes Tribune published the Alberto story on the find that year and drew the attention of the National Museum, which sent a team to the site in April 2009.

Last week, the team also found part of a fossil of a belemnite, an extinct group of marine cephalopods very similar to the squid and closely related to the cuttlefish, Ong said.

The belemnites possessed an ink sac but, unlike the squid, they had 10 arms and no tentacles. The part that remained of the belemnite, which could be as long as three meters or 10 feet, is the back part of the shell and it looks like a slender bullet, she said.

Shigeta said the Dugui ammonites could be found in a one-meter layer of sandstone at the bottom of the Silungan ng Higante rock outcrop, with the belemnite finds in the 20-centimeter thick muddy sandstone just below it.

While the Comagaycay site is older than the Dugui site, Aguilar said the Silungan site is far more biologically diverse as it has seashells, gastropods, sea urchins, squids, annelids or segmented worms, and rudists, which are bivalves of a strange shape.

The team also went three kilometers up the Comagaycay river to look for ammonite samples but found only a small one embedded in a rocky bank.

The site was discovered by a geologist, a certain Sendon from the MGB regional office for Bicol based in Legazpi City in 1984 while the agency and Japanese expert Dr. Wataro Hashimoto found Protozoan microscopic fossils belonging to the Cretaceous period at Bunag-bunag point in the same town, according to Aguilar.

Shigeta said that their study’s objectives were to date the enclosing rock of the fossil and study the life habits of the strange marine animals that existed long before they became extinct.

While the team did not find any fossil of a marine reptile, the possibility that there could be remnants of marine dinosaurs in the Silungan site remains.

Alberto said he was still looking for a huge bone that was said to have been stored by an old man in one of the recesses of a labyrinthine cavern at the top of a rock outcrop.(PNA)



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