Tiktaalik

Today's animal is one of the oldest creatures I've ever written about, and is probably the oldest vertebrate. (I know there are a few really old invertebrates in the archives somewhere) Tiktaalik roseae is a species first discovered in Nunavit, Canada back in 2004 and was named after and Inuit word for the Burbot fish.. It is notable because it is (possibly) one of the precursors to modern Tetrapods, and helps us to understand how amphibians and other Tetrapods evolved.

Tiktaalik Illustration

Like Coelocanths and my beloved Lungfish, Tiktaalik was a Lobe-finned fish. What made it different from all its cousins at the time was that is had some really neat characteristics that would be found in the earliest amphibians.

For one, Tiktaalik had a flat body, with eyes on its head in a way very similar to alligators and crocodiles. It also had a mobile neck that fish do not possess, as well as tetrapod-like lungs. However, it was not quite a tetrapod yet, for it still had lungs, scales, and fins.

Early in this entry I stated that Tiktaalik is possibly a precursor to Tetrapods. The reasoning for the uncertainty is that in 2010 tetrapod footprints from Poland were dated to be 400 million years old. Those predate even the Tiktaalilk. Because fossils only preserve in very specific situations, breaks undoubtedly exist between species in the record. Our understanding of the distant, distant past adjusts and changes with each new, valuable discovery. It'll be interesting to see what more can be learned from Tiktaalik, these tracks, and other early vertebrates.

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Status : Lived around 375 million years ago

Location : Fossils found in Canada

Size : Body length up to 9ft (2.7m)

Classification : Phylum : Chordata -- Subphylum : Vertebrata -- Class : Sarcopterygii
Genus : Tiktaalik -- Species : T. roseae

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Australian Lungfish

Granddad (with the spots) and a friend

Yesterday I had the delight to meet Granddad, the world's oldest fish in a public aquarium. Granddad is an Australian Lungfish who first arrived at Chicago's Shedd Aquarium in 1933! So if you only learn one thing from this article, know that Lungfish can live for quite a long time.

But if you're after two cool tidbits, know that the Australian Lungfish is essentially a living fossil. Fossilized evidence of its family members date back to the Devonian, and the Australian Lungfish itself has remained relatively unchanged for nearly 100 million years! There are five other Lungfish species still alive, and one of their closest lobe-finned relatives is the Coelacanth. Lobe-Finned fish are especially notable because it is from them that tetrapods eventually evolved!

So why are they called Lungfish anyway? Because they have lungs of course! In the case of the Australian Lungfish, only one lung is present. But if there is a lack of water it is able to surface and breathe air for a short amount of time.

Australian Lungfish reproduce through spawning, which takes place from September to December. The eggs take only three weeks to hatch, but the young fish grow very, very slowly. After eight months they may only be 6 inches long! Due to their slow growth rate, no one actually knows how old Granddad is. He was fully mature when he showed up, making him at least 80 but possibly much, much older!

Australian Lungfish are not listed by the IUCN, but they are protected by the local government and are listed in CITES Appendix 2.

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IUCN Status : Not Listed

Location : Australia

Size : Length up to 5ft (1.5m)

Classification : Phylum : Chordata -- Class : Sarcopterygii -- Subclass : Dipnoi
Order : Ceratodontiformes -- Family : Ceratodontidae
Genus : Neoceratodus -- Species : N. forsteri

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Coelocanth

Coelocanths are an entire order of lobe-fined fishes that were believed to have died out during the Cretaceous Extinction 65 million years ago. Fossil specimens of 125 species have been identified, some dating back 400 million years. Everyone thought they were a creature of the past and then all of that thought kicked the bucket when a living species of Coelocanth was caught by fishermen off the coast of South Africa in 1938. Since then, dozens of these fish have been found off the east coast of Africa, and in 1998 a second living species was discovered in the waters outside of Sulawesi, Indonesia.

(Image Source)

Coelocanths are so amazing because they really are living fossils. They are lobed finned fish, a class of animals that is now largely extinct but that also includes half a dozen species of extant Lungfish. The fins of Coelocanths jut outwards from the body and rotate almost as if the fish were walking. If is no surprise that lobed finned fish were the descendants of all Tetrapods!

Coelocanths also have a few other special features, including an electrosensitive organ in their snout that helps them detect prey. They also have no vertebrae, and their "spine" is actually a notochord; an oil filled tube that provides the body with support. Coelocanths also have an intercranial joint that allows their mouths to open especially wide in order to swallow prey whole. Coelocanths can reach lengths of up to 6 feet and weigh over 200lbs. Females are ovoviviparous, and two pup baring females have been caught.

It is estimated that there are around 1,000 Coelocanths left, all of which lives at depths of up to 2,300ft. They are an endangered species and are protected by CITES.

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