Fin ray patterns at the fin-to-limb transition
https://www.pnas.org/content/early/2019/12/24/1915983117

Any explanation from the ID perspective?

Science News’s Top fossils in 2019 show a diminishing Darwin

In the mid 2000s several fossils were discovered in northern Canada of a strange fish-like creature dubbed Tiktaalik. The fossils were dated to hundreds of millions of years ago, to a time when there were thought to be fish but no vertebrate land animals, or “tetrapods.” On close examination the fossils were seen to have structures — in particular, bones that resembled wrists — that were thought to make them good candidates for transitional forms between fish and tetrapods. For several years Tiktaalik was hailed as the missing link between fish and land vertebrates. But its moment of fame was cut short in early 2010 with the discovery of fossil footprints in Poland of true tetrapods which were at least ten million years older than Tiktaalik. At a stroke, the Canadian fossil could no longer be a transitional form, since it appeared later in the fossil record than its supposed descendants.

Darwin on Trial — As Fresh and Relevant as Ever

The claim in the PBS video (timecode 6:02-6:06) that ancestors of early tetrapods like Tiktaalik and Ichthyostega probably had a swim bladder is complete rubbish. 

But it gets worse. PBS makes up a completely idiotic scenario where the swim bladder allegedly became bigger in some lobe-finned fish, developed more blood vessels, and then in time transformed the air bladder from a hydrostatic organ into a respiratory organ. This was then split into a paired lung in bichirs and lungfish. Again, this whole scenario is complete nonsense. It is emphatically not proposed by any evolutionary biologist!

Lungs simply could not have evolved from the swim bladder. Why? Because lungs predate the origin of the swim bladder, while the latter only appears as a parallel development in a subgroup of bony fish that has the lungs secondarily reduced. Alternatively the lungs and swim bladder might have both evolved from the primitive lungs of a common ancestor of lobe-finned and ray-finned fish (Tatsumi et al. 2016), which would be the exact reverse of the PBS fantasy scenario.

So, could PBS be excused on the grounds that this is all brand-new research they simply did not yet know about? Not really. I learned all of the above at Tübingen University nearly 25 years ago. We were told even then by our fantastic teacher Dr. Gerhard Mickoleit about the “urban legend” that lungs evolved from the swim bladder. (See his book Phylogenetische Systematik der Wirbeltiere, 2004: pp. 82 and 88, Pfeil Verlag.) 

At their Patreon fundraising site, PBS Eons advertises itself as being “devoted to making sure our content is of the highest possible quality, and that takes a lot of time and resources.” From a self-proclaimed high-class educational program, such crude errors are intolerable.

PBS Eons Teaches Nonsense about Evolution

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Repeated evolution of amphibious behavior in fish and its implications for the colonization of novel environments (2016)

We know little about on how frequently transitions into new habitats occur, especially the colonization of novel environments that are the most likely to instigate adaptive evolution. One of the most extreme ecological transitions has been the shift in habitat associated with the move from water to land by amphibious fish. We provide the first phylogenetic investigation of these transitions for living fish. Thirty‐three families have species reported to be amphibious and these are likely independent evolutionary origins of fish emerging onto land. Phylogenetic reconstructions of closely related taxa within one of these families, the Blenniidae, inferred as many as seven convergences on a highly amphibious lifestyle. Taken together, there appear to be few constraints on fish emerging onto land given amphibious behavior has evolved repeatedly many times across ecologically diverse families. The colonization of novel habitats by other taxa resulting in less dramatic changes in environment should be equally, if not, more frequent in nature, providing an important prerequisite for subsequent adaptive differentiation.

Number of times cited according to CrossRef: 14

• Yukitoshi Katayama, Yoshio Takei, Makoto Kusakabe and Tatsuya Sakamoto, Hormonal regulation of thirst in the amphibious ray-finned fish suggests the requirement for terrestrialization during evolution, Scientific Reports, 10.1038/s41598-019-52870-7, 9, 1, (2019).
  Crossref
• Tak Shing Chan and Andreas Carlson, Physics of adhesive organs in animals, The European Physical Journal Special Topics, 10.1140/epjst/e2019-800131-2, 227, 17, (2501-2512), (2019).
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• Helder Mateus Viana Espírito‐Santo, Jefferson Gomes Sodré and Jansen Zuanon, He leaps, she beats: The role of social interactions on the overland movements of an Amazonian amphibious killifish, Ecology of Freshwater Fish, 28, 3, (356-364), (2018).
  Wiley Online Library
• Andy J. Turko, Priyam Maini, Patricia A. Wright and Emily M. Standen, Gill remodelling during terrestrial acclimation in the amphibious fish , Journal of Morphology, 280, 3, (329-338), (2019).
  Wiley Online Library
• Takashi Miyake, Natsuki Aihara, Ken Maeda, Chuya Shinzato, Ryo Koyanagi, Hirozumi Kobayashi and Kazunori Yamahira, Bloodmeal host identification with inferences to feeding habits of a fish-fed mosquito, Aedes baisasi, Scientific Reports, 10.1038/s41598-019-40509-6, 9, 1, (2019).
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• Yukitoshi Katayama, Tatsuya Sakamoto, Kazuhiro Saito, Hirotsugu Tsuchimochi, Hiroyuki Kaiya, Taro Watanabe, James T. Pearson and Yoshio Takei, Drinking by amphibious fish: convergent evolution of thirst mechanisms during vertebrate terrestrialization, Scientific Reports, 10.1038/s41598-017-18611-4, 8, 1, (2018).
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• Ryan Andrades, José Amorim Reis-Filho, Raphael M. Macieira, Tommaso Giarrizzo and Jean-Christophe Joyeux, Endemic fish species structuring oceanic intertidal reef assemblages, Scientific Reports, 10.1038/s41598-018-29088-0, 8, 1, (2018).
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• Giulia S. Rossi, Andy J. Turko and Patricia A. Wright, Oxygen drives skeletal muscle remodeling in an amphibious fish out of water, The Journal of Experimental Biology, 10.1242/jeb.180257, 221, 11, (jeb180257), (2018).
  Crossref
• Michael D. Livingston, Vikram V. Bhargav, Andy J. Turko, Jonathan M. Wilson and Patricia A. Wright, Widespread use of emersion and cutaneous ammonia excretion in Aplocheiloid killifishes, Proceedings of the Royal Society B: Biological Sciences, 10.1098/rspb.2018.1496, 285, 1884, (20181496), (2018).
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• Peter C. Wainwright and Sarah J. Longo, Functional Innovations and the Conquest of the Oceans by Acanthomorph Fishes, Current Biology, 10.1016/j.cub.2017.03.044, 27, 11, (R550-R557), (2017).
  Crossref
• Andy J. Turko, Dietmar Kültz, Douglas Fudge, Roger P. Croll, Frank M. Smith, Matthew R. Stoyek and Patricia A. Wright, Skeletal stiffening in an amphibious fish out of water is a response to increased body weight, The Journal of Experimental Biology, 10.1242/jeb.161638, 220, 20, (3621-3631), (2017).
  Crossref
• Terry J. Ord, Thomas C. Summers, Mae M. Noble and Christopher J. Fulton, Ecological Release from Aquatic Predation Is Associated with the Emergence of Marine Blenny Fishes onto Land, The American Naturalist, 10.1086/691155, 189, 5, (570-579), (2017).
  Crossref
• Yukitoshi Katayama, Tatsuya Sakamoto, Keiko Takanami and Yoshio Takei, The Amphibious Mudskipper: A Unique Model Bridging the Gap of Central Actions of Osmoregulatory Hormones Between Terrestrial and Aquatic Vertebrates, Frontiers in Physiology, 10.3389/fphys.2018.01112, 9, (2018).
  Crossref
• Christian Damsgaard, Vikram B. Baliga, Eric Bates, Warren Burggren, David J. McKenzie, Edwin Taylor and Patricia A. Wright, Evolutionary and cardio‐respiratory physiology of air‐breathing and amphibious fishes, Acta Physiologica, e13406, (2019).
  Wiley Online Library

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The Origin and Evolution of the Surfactant System in Fish: Insights into the Evolution of Lungs and Swim Bladders

Several times throughout their radiation fish have evolved either lungs or swim bladders as gas‐holding structures. Lungs and swim bladders have different ontogenetic origins and can be used either for buoyancy or as an accessory respiratory organ. Therefore, the presence of air‐filled bladders or lungs in different groups of fishes is an example of convergent evolution. We propose that air breathing could not occur without the presence of a surfactant system and suggest that this system may have originated in epithelial cells lining the pharynx. Here we present new data on the surfactant system in swim bladders of three teleost fish (the air‐breathing pirarucu Arapaima gigas and tarpon Megalops cyprinoides and the non‐air‐breathing New Zealand snapper Pagrus auratus). We determined the presence of surfactant using biochemical, biophysical, and morphological analyses and determined homology using immunohistochemical analysis of the surfactant proteins (SPs). We relate the presence and structure of the surfactant system to those previously described in the swim bladders of another teleost, the goldfish, and those of the air‐breathing organs of the other members of the Osteichthyes, the more primitive air‐breathing Actinopterygii and the Sarcopterygii. Snapper and tarpon swim bladders are lined with squamous and cuboidal epithelial cells, respectively, containing membrane‐bound lamellar bodies. Phosphatidylcholine dominates the phospholipid (PL) profile of lavage material from all fish analyzed to date. The presence of the characteristic surfactant lipids in pirarucu and tarpon, lamellar bodies in tarpon and snapper, SP‐B in tarpon and pirarucu lavage, and SPs (A, B, and D) in swim bladder tissue of the tarpon provide strong evidence that the surfactant system of teleosts is homologous with that of other fish and of tetrapods. This study is the first demonstration of the presence of SP‐D in the air‐breathing organs of nonmammalian species and SP‐B in actinopterygian fishes. The extremely high cholesterol/disaturated PL and cholesterol/PL ratios of surfactant extracted from tarpon and pirarucu bladders and the poor surface activity of tarpon surfactant are characteristics of the surfactant system in other fishes. Despite the paraphyletic phylogeny of the Osteichthyes, their surfactant is uniform in composition and may represent the vertebrate protosurfactant.