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Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?

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Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?


Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?

Para ahli paleontologi baru-baru ini menemukan fosil dari ikan bertulang tertua di dunia. Ikan ini diperkirakan hidup di laut Devonian 400 juta tahun lalu.

"Ligulalepis", ikan bertulang paling awal ini diketahui berhubungan erat dengan nenek moyang manusia.

Tak hanya moyang manusia, ikan ini juga diperkirakan berhubungan dengan moyang osteichthians, sekelompok hewan yang memiliki kerangka tulang dan rahang.

Osteichthians meliputi keluarga ikan modern, amfibi, reptil, burung, dan mamalia.

Para peneliti dari Flinder's University di Adelaide, Australia bekerja dengan tim peneliti internasional untuk mempelajari fosil ini.

Dua tengkorak fosil yang ditemukan di Australia tersebut memang tidak sempurna. Tapi, dengan pemindaian 3D dan data micro-CT, para peneliti menciptakan model digital otaknya berdasar bentuk yang diambil dari dalam bagian tengkoraknya.

Mereka juga dapat menentukan bentuk atap tengkorak dan saluran hidung dan telinga dari hal tersebut. Ini menjelaskan rincian tentang bagaimana salah satu leluhur awal mamalia berevolusi.


“Memahami struktur itu penting karena Ligulalepis berada dalam posisi penting di pohon evolusi," ungkap Dr Alice Clement, salah satu peneliti yang terlibat penelitian ini dikutip dari news.flinders.edu.au.

"Penemuan ini mengidentifikasi ikan ini sebagai leluhur dari semua ikan bertulang tepat sebelum dua kelompok besar membelah dan berevolusi dengan tubuh yang berbeda," sambungnya.

Baca juga: Berusia 90.000 Tahun, 2 Alat Kayu Ini Bukan Buatan Nenek Moyang Kita

Profesor Palaeontologi di Flinders University, John Long mengatakan bahwa ikan bertulang ini adalah kelompok yang penting karena hewan darat seperti mamalia, reptil, dan amfibi berevolusi dari mereka.

“Tidak banyak orang yang mengira manusia mengembangkan bagian-bagian struktur tulang mereka dari ikan. Kita semua hanyalah ikan yang sangat mahir, itulah inti dari cerita kita, ”kata Profesor Long.

"Sekitar 400 juta tahun yang lalu, beberapa ikan canggih ini mulai mengembangkan sirip di bagian depan yang memiliki tulang yang pada akhirnya akan menjadi humerus (lengan), ulna (pergelangan tangan), dan jari-jari yang membentuk lengan kita dan ikan ini mulai mengembangkannya dalam sirip mereka," Profesor Kata panjang.

Para peneliti menerbitkan makalah tentang hewan itu di jurnal Evolutionary Biology.

Dirangkum dari Newsweek, Jumat (01/06/2018), beberapa tahun terakhir, penemuan fosil menjadi sangat penting bagi ahli biologi evolusi. Fosil-fosil tersebut membantu kita untuk memahami detail tentang pohon kehidupan.




https://sains.kompas.com/read/2018/0...usia-kok-bisa-
buat update gan 😁


Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?
Ligulalepis is an extinct genus of prehistoric bony fish.[1] Ligulalepis was first described from isolated scales found in the Taemas-Wee jasper limestones of New South Wales (Early Devonian age) by Dr Hans-Peter Schultze (1968[2]) and further material described by Burrow (1994)[3]. A nearly complete skull found in the same general location was described in Nature by Basden et al. (2000) claiming the genus was closely related to basal ray-finned fishes (Actinopterygii)[4].In 2015 Flinders University student Benedict King found a more complete new skull of this genus which was formally described by Clement et al. (2018), showing the fish to be on the stem of all osteichthyans[5].


It's less than 2cm long, but this 400 million year old fossil fish changes our view of vertebrate evolution




Published today, our new paper describes a spectacular 400 million-year-old 3-D-preserved fossil fish, Ligulalepis.



The 3-D anatomy of the fossilised Ligulalepis skull reveals previously unknown details of the pattern of dermal skull bones, the shape of the brain cavity, and other soft tissue features (such as nerves and blood vessels) in this species.

Why are we so excited about discovering the structure of an ancient fish skull? Because Ligulalepis sits in a very important position in the vertebrate evolutionary tree.

Boney fishes—and us

Fishes are the most diverse group of backboned animals (vertebrates) on the planet, with roughly 30,000 known species.

The vast majority of these (around 98%!) are bony fishes or osteichthyans. These includes most of fishes we like to eat, such as salmon, tuna and trout, as well as fishes we keep as pets, like goldfishes and guppies. These are called ray-finned fishes (actinopterygians) as their fins are supported by bony rods called fin-rays.

The other major group of bony fishes have robust lobe-fins (sarcopterygians), a group that contains the living lungfishes and coelacanths, as well as several extinct groups.

It's less than 2cm long, but this 400 million year old fossil fish changes our view of vertebrate evolution
A: skull of Ligulalepis viewed from the left side; and B: space for the brain (cranial endocast) also shown in left lateral view. Credit: Alice Clement
Sarcopterygians are an important group because the first four-legged land animals, the tetrapods, evolved from them. Today we can regard all living tetrapods (amphibians, reptiles, birds and mammals) as a subgroup within the bony fishes.

An exciting new find

The first discovery of the fish called Ligulalepis was a tiny fossil fish skull found in limestone near Wee Jasper in New South Wales about 20 years ago.



It has fuelled debate around early osteichthyan evolution ever since, without any clear resolution as to where this enigmatic fish sits in the family tree.

Then, about two years ago, a second skull of this fish was discovered by a Flinders University student, Benedict King. The specimen was found in the same limestone outcrops near Wee Jasper. It was also preserved in 3-D, but was even more complete than the original specimen.

Earlier work by us recognised electroreceptive sensory pits in this skull of Ligulalepis.

It's less than 2cm long, but this 400 million year old fossil fish changes our view of vertebrate evolution
Both known Ligulalepis fossils were found in limestone outcrops at Wee Jasper, NSW. Credit: Ben King, Author provided
Secrets of the skull

Both the old and new skulls were the focus of our new paper. Our team first prepared the tiny more recent specimen (less than 2cm in length) out of the rock using using weak acetic acid to expose the bone, as the carbonate rock dissolved.

Then we used micro computed tomography (CT) scanning to visualise the skeletal anatomy of the two known Ligulalepis specimens. Powerful X-rays pass through the bones to reveal many hidden features inside the skulls.

The scans revealed a perplexing mixture of characters in the skulls of these fish. Some features, like the shape of the inner ear canals, seemed to belong to cartilaginous fishes such as sharks. Other features, like the overall shape of the brain case, were clearly osteichthyan (bony fish) characters.

The pattern of bones that form the skull roof was an unexpectedly primitive feature also seen in an extinct group of jawed fishes called placoderms.

The CT technique enabled us to reconstruct what the brain cavity of this 400 million year old fish looked like, allowing us to digitally restore the brain shape for the first time (see video below).


A digital view of the Ligulalepis brain.
A complicated family tree

Prior to our detailed analysis of this skull, some scientists considered Ligulalepis to be closely related to the ray-finned fishes. Others placed it alongside lobe-finned fishes.

A third school of thought envisaged it even lower down on the fish family tree – and this is close to where we have now placed it, on the "stem" of the tree leading to the true osteichthyans.

Its unique position on the tree of life means that Ligulalepis provides great insight into what the ancestor of the two major radiations of bony fishes looked like. Furthermore, the detailed analysis of its newly revealed characters helps to clarify the early evolutionary radiation of all animals with a bony skeleton—including us humans.

Missing fossils

Most modern fish are ray-finned fish (actinopterygians), with around 29,000 living species. Their origins can be confidently dated back to the Middle Devonian, around 390 million years ago with fishes like Cheirolepis from Scotland.

It's less than 2cm long, but this 400 million year old fossil fish changes our view of vertebrate evolution
The position of Ligulalepis in the evolutionary family tree at the base of the osteichthyan radiation. Credit: Brian Choo
However the existence of the related group "lobe-fins" (sarcopterygians) is much older, with early representatives of that group such as Guiyu, from China, dated at about 430 million years ago. This suggests there are some parts of the early fish fossil record that are poorly understood.

Our fossil and the new analyses we have performed helps to resolve the big question about what the ancestor of all modern bony fishes looked like. It also illustrates the sequence of changes these early fish went through to achieve their modern "body plan".

Also, our analyses show that Ligulalepis was the closest known species to a peculiar group of early lobe-finned fish called "psarolepids" known only from China. It supports the hypothesis that the first early boney fish originated and radiated in China, then migrated out via East Gondwana (Australia and Antarctica), the part of the southern supercontinent closest to the ancient Chinese terrains.

Our findings highlight that the evolutionary family tree of the first bony fishes is much more complicated than we had thought, demonstrating the importance of palaeontology to help us more accurately understand our distant origins.


Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?

Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?





More information: Alice M Clement et al. Neurocranial anatomy of an enigmatic Early Devonian fish sheds light on early osteichthyan evolution, eLife (2018). DOI: 10.7554/eLife.34349

This article was originally published on The Conversation. Read the original article.The Conversation

Provided by: The Conversation
Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa? tapi kita juga ikan
Dari ikan akan kembali jadi ikan.

Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?
jaman baheula
waduh jadi bingung ane gan
masa moyang manusia ikan.
keluarga Nye Aquaman dong.


Quote:


banyak teori ya gan 😁
Bukannya Kera bre emoticon-Leh Uga
jaman purba
siluman iwak jebul emoticon-Wow

Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?


KATANYA AHLI TAPI KOK MASIH PERCAYA TOERI EVOLUSI.
KASIHAN
Ikan indosiar itu gan emoticon-Big Grin
Hmmm...
Para ilmuan bisa prediksi umur ikan itu 400 tahun bagaimana sih ? emoticon-Bingung (S)
Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?Ahli Sebut Fosil Ikan 400 Juta Tahun Ini Moyang Manusia, Kok Bisa?

mungkin ikanya kakek ini yg dimaksud
nenek moyang ane bangsa Saiyan emoticon-Cool
In God i trust
Quote:


400 juta tahun gan
Dulu dibilang moyangnya manusia dari monyet, sekarang ikan, ntar apaan lagi dah emoticon-Big Grin