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Placoderm "Placoderms, often called the dinosaurs of the seas, thrived some 420 to 350 million years ago." "A prehistoric fish which roamed the seas almost 400 million years ago has been unveiled by scientists as the "oldest mother ever discovered". The fossilised placoderm - a now extinct, armoured fish - was discovered in Western Australia complete with a perfectly preserved embryo and umbilical cord." "The 10in fossil, dug up at the Gogo rock formation, east of the remote town of Fitzroy Crossing, has been named Materpiscis attenboroughi - 'Attenborough's mother fish' - after the naturalist Sir David Attenborough. Thought to be at least 380 million years old, the find pushes back the record for a live birth by 200 million years. Dr John Long, head of sciences at Museum Victoria, Melbourne, who found the specimen, said: "I think this is one of the most extraordinary fossil finds of all time, as it is the first time in history we have a maternal feeding structure preserved in any fossil "When I first saw the embryo inside the mother fish my jaw dropped. I was silent, stunned like a mullet. I realised that in my hands was the oldest known vertebrate embryo. "It dawned on me after studying the specimen that this was the earliest evidence of vertebrates having sex by copulation - not just spawning in water, but sex that was fun." Kate Trinajstic who was involved in the discovery said the cord and embryo almost went unnoticed." - The Telegraph, UK. Refs: https://www.nature.com/news/2008/080528/full/453575a/box/1.html Copulation in Placoderms (YouTube; 30 secs) Copuate to Populate The first vertebrate sexual organs evolved as an extra pair of legs Tiktaalik In 2014 an unique fossil ,half fish half amphibian was found on Ellesmere Island in Arctic Canada. "Its extraordinary blend of gills, scales, fins and lungs, combined with a movable neck, sturdy ribcage and crocodile-like head, placed Tiktaalik half way between fish and the earliest four-legged land animals." said The Guardian.

Hagfish Not related to Lampreys it was unclear if Lampreys and Hagfish were related or whether the Hagfish was a degenerate form of Lamprey which seemed to be the case from morphological arguments. However new fossil evidence and DNA has now shown they are independent and both were around at the same time long long ago. Title:agfish from the Cretaceous Tethys Sea and a reconciliation of the morphological–molecular conflict in early vertebrate phylogeny", Miyashita et. al., 2018. Summary: "Hagfish depart so much from other fishes anatomically that they were sometimes considered not fully vertebrate. They may represent: (i) an anatomically primitive outgroup of vertebrates (the morphology-based craniate hypothesis); or (ii) an anatomically degenerate vertebrate lineage sister to lampreys (the molecular-based cyclostome hypothesis). This systematic conundrum has become a prominent case of conflict between morphology- and molecular-based phylogenies. To date, the fossil record has offered few insights to this long-branch problem or the evolutionary history of hagfish in general, because unequivocal fossil members of the group are unknown. Here, we report an unequivocal fossil hagfish from the early Late Cretaceous of Lebanon. The soft tissue anatomy includes key attributes of living hagfish: cartilages of barbels, postcranial position of branchial apparatus, and chemical traces of slime glands. This indicates that the suite of characters unique to living hagfish appeared well before Cretaceous times. This new hagfish prompted a reevaluation of morphological characters for interrelationships among jawless vertebrates. By addressing nonindependence of characters, our phylogenetic analyses recovered hagfish and lampreys in a clade of cyclostomes (congruent with the cyclostome hypothesis) using only morphological data. This new phylogeny places the fossil taxon within the hagfish crown group, and resolved other putative fossil cyclostomes to the stem of either hagfish or lamprey crown groups. These results potentially resolve the morphological–molecular conflict at the base of the Vertebrata. Thus, assessment of character nonindependence may help reconcile morphological and molecular inferences for other major discords in animal phylogeny"