Fossil Fish Pushes Evolutionary Time
Quick! When was the Age of Fishes? If you said “Devonian,” you were correct according to the textbooks and museums, but where’s your evidence? Look at this diorama in the Smithsonian depicting the seas of the Silurian, the period preceding the Devonian: crinoids, trilobites, corals and nautiloids, but no fish. It may be time to change the artwork and the textbooks. A fully-finned fish, jaws and all, has been found in Silurian rock in China.
Prior to the announcement in Nature,1 the only tentative fossil evidence of a gnathostome (jawed) fish in the late Silurian consisted of head fragments dated 416 million years ago (Mya). Now, a nearly complete fossil of a jawed fish the discoverers named Guiyu oneiros pushes the date three million years earlier, well into the Silurian. The fact that it is already fully a boned fish means its non-fish predecessors had to have evolved, according to Darwin’s theory, much earlier than that. “As the oldest articulated sarcopterygian, the new taxon offers insights into the origin and early divergence of osteichthyans [bony fish], and indicates that the minimum date for the actinopterygian�sarcopterygian split was no later than 419 million years ago,” the authors said. “No later than” translates to “probably a lot earlier than.”
This puts pressure on the whole fish family tree. Prior to the division between actinopterygians (which includes most familiar fish species) and sarcopterygians (lungfish, Coelacanth, and all four-footed animals, including us), there was supposed to be some branching points within the osteichthyes (bony fish) and chondrichthyes (cartilaginous fish), and between jawed and non-jawed vertebrates. How well documented have these major branching points been in the fossil record?
Osteichthyans, which fall into two major monophyletic groups, namely actinopterygians (bichirs, sturgeons, gars, bowfins and teleosts) and sarcopterygians (coelacanths, lungfishes and tetrapods), make up 98% of recognized living vertebrate species. The rise of osteichthyans from other primitive gnathostomes is a key transition in vertebrate evolution, yet this transition is poorly documented by the fossil discoveries of the last century. Major morphological gaps existed between actinopterygians and sarcopterygians, and between osteichthyans and non-osteichthyan gnathostomes (chondrichthyans, acanthodians and placoderms). The past decade has seen the gap narrowing with fossil discoveries such as Psarolepis, Ligulalepis and Dialipina, which show fascinating combinations of osteichthyan and non-osteichthyan gnathostome characters, providing new opportunities for studying the polarity and evolution of these characters. However, the basal osteichthyan phylogeny remains uncertain owing to the large number of unknown character states in these early forms and the provisional assignment of disarticulated remains to a single taxon. A better understanding of these fishes is therefore crucial in reconstructing the part of phylogeny close to the split between actinopterygians and sarcopterygians.
That’s where Guiyu comes in. It is unquestionably sarcopteryginian. Before now, evolutionary paleontologists drew their phylogenetic trees of the Silurian in the absence of evidence about jawed vertebrates. The three specimens mentioned above are all well in the Devonian, except for Psarolepis, “an indeterminable osteichthyan” tentatively dated to the late Silurian. Now, Guiyu puts one of the major branching points well into the Silurian. Whatever led to the evolution of the sarcopterygians had to happen earlier, and more rapidly, than previously believed.
Michael I. Coates (U of Chicago) commented on this find in the same issue of Nature.2 “Discovery of an unusually intact and ancient fossil fish provides further evidence that the search for modern vertebrate origins requires breaking out of the Devonian and into the preceding period,” he began. Usually, the earliest fossils are scrappy and indistinct, concocted into “conjectural species” from fragments, but this one is remarkably well preserved. Coates agrees that it comes from a “poorly resolved patch of vertebrate evolution. Crucially, this piscine offshoot of our own distant past is both unusually intact and exceptionally old.”
What does this find indicate about our knowledge of past eras? After discussing other remarkable recent finds, some of which have surprising mosaics of features, he said that “The straightforward message is that the origin of modern gnathostomes is not a Devonian phenomenon, after all.” Add some fish to that Silurian diorama. In fact, in his article he showed a 1940s-era artwork of a fishless Silurian sea, and said, “What else might be absent? Evidence of early actinopterygians (ray-finned fishes) and chondrichthyans (sharks and chimaeras) must be lurking out there, somewhere in the Silurian sediments.” Here’s another straightforward message by Coates: “By pushing a whole series of branching points in gnathostome evolution out of the Devonian and into the Silurian, the discovery of Guiyu also signals that a significant part of early vertebrate evolution is unknown.” He encouraged paleontologists to take a new look at their Silurian fossils and dig up evidence that must be there.
1. Zhu, Zhao, Jia, Lu, Qiao and Qu, “The oldest articulated osteichthyan reveals mosaic gnathostome characters,” Nature 458, 469-474 (26 March 2009) | doi:10.1038/nature07855.
2. Michael I. Coates, “Palaeontology: Beyond the Age of Fishes,” Nature 458, 413-414 (26 March 2009) | doi:10.1038/458413a.
The collapse of a mythology – the fishless Silurian sea – occurring before our eyes. Evolutionists like to quote the maxim “absence of evidence is not evidence of absence” when they are confronted with the lack of transitional forms. That maxim cuts both ways. They jeer creationists about the lack of any “Precambrian rabbit” fossils, but notice two things about that: (1) use the same maxim against the evolutionists, and (2) the evolutionists have rigged the names and dates of the strata to prevent such a thing from being found. We’ve seen them reclassify a stratum from one end of the geological column to the other when it suited their purposes (01/03/2007). Finding a rabbit in a Precambrian bed would not make them abandon Darwin Daddy. They would just say, “Well, what do you know; this bed is Pleistocene.”
When you find anomalies like this within their own dating scheme, the case for falsification is more convincing. Notice that the “earliest” fossils are not transitional. They neither show primitive features nor clear-cut lineages. Prior to Guiyu, they said the earliest specimens like Psarolepis had a mosaic of features. This means it did not clearly fall into a single lineage. Now, an even earlier specimen is unquestionably sarcopterygian and 100% fish. The artist conception shows a fish you could catch and eat. It’s got teeth, gills, scales, fins, eyes and all the equipment a fish could want. It wasn’t becoming a fish from something else, and it wasn’t evolving into something else. Think how many lucky mutations must have been required to get all these parts working together from some non-fish predecessor. Since vertebrates have now been found all the way back to the early Cambrian (01/30/2003), it’s not that big a stretch to imagine finding a mammal in Cambrian or Precambrian strata some day. After all, the skeletal system, immune system, digestive system, circulatory system, central nervous system had already “emerged” by then, so what’s the big deal shaping the outward morphology a little?
Another case of the “absence of evidence” maxim bears repeating. The world is full of “living fossils” – species alive today that left no trace for supposed tens or hundreds of millions of years (see list on CreationWiki). There are two possible lessons here. One is that Precambrian rabbits could conceivably be found. If you accept the evolutionary timeline, you would have to believe that the tuatara, coelacanth and Wollemi Pine lived through tens of millions of years, catastrophes and all, without leaving a trace in the fossil record – because they are still alive today. There you go – “absence of evidence is not evidence of absence.”. Secondly, living fossils argue against the evolutionary timeline altogether. Is it plausible to think that these organisms survived unchanged for all that time? Where is the evolution? Just maybe those millions of years are fiction. It would make more sense to believe that not much time has passed between the fossil and living representatives. Whichever way you take it, today’s entry should shame the Darwinists into admitting they don’t know what they claim in their museum dioramas.
