Fossil Friday: The Abrupt Origin of Ichthyosaurs
This Fossil Friday features Stenopterygius quadricissus from the Lower Jurassic Posidonia shale of Holzmaden in southern Germany, which is about 190 million years old. As a child I went collecting fossils from this fossil locality, which was close to my childhood home, and with a bit of luck you could not only find ammonites but even vertebrae of such ichthyosaurs. Apart from dinosaurs and pterosaurs, the ichthyosaurs are one of the iconic groups of Mesozoic reptiles. Even though they look like a hybrid between a dolphin and a shark, they were marine reptiles that are believed to have descended from monitor-lizard-like terrestrial ancestors.
Darwinism would predict a long and gradual transition between these very different body plans, but actually ichthyosaurs appeared very abruptly about 4 million years after the great end-Permian mass extinction event about 252 million years ago, which annihilated about 81 percent of marine and 70 percent of terrestrial biodiversity. There is general consensus that ichthyosaurs did not yet exist before this cataclysm, and the oldest fossils indeed only appeared in the Lower Triassic of China about 248 million years ago. Jiang et al. (2016) concluded that “ichthyosauriforms evolved rapidly within the first one million years of their evolution.” Well, that was the state of knowledge until a few days ago, when a brand new study (Kear et al. 2023) changed the picture and made the origin of ichthyosaurs even much more abrupt. A team of scientists from Norway and Sweden described ichthyosaur remains from the Arctic island of Spitsbergen, which are about 250 million years old but already show clear evidence for a fully marine way of life.
Revealing Admissions
The press release by Uppsala University (2023) makes some very revealing admissions about this unexpected discovery:
As the story goes, land-based reptiles with walking legs invaded shallow coastal environments to take advantage [of] marine predator niches that were left vacant by this cataclysmic event. Over time, these early amphibious reptiles became more efficient at swimming and eventually modified their limbs into flippers, developed a fish-like body shape, and started giving birth to live young; thus, severing their final tie with the land by not needing to come ashore to lay eggs.
The new fossils discovered on Spitsbergen are now revising this long accepted theory. …
Unexpectedly, these vertebrae occurred within rocks that were supposedly too old for ichthyosaurs. Also, rather than representing the textbook example of an amphibious ichthyosaur ancestor, the vertebrae are identical to those of geologically much younger larger-bodied ichthyosaurs, and even preserve internal bone microstructure showing adaptive hallmarks of fast growth, elevated metabolism and a fully oceanic lifestyle.
This means nothing less than that the transition from a land-living reptile to a fish-like marine reptile was completed in less than 2 million years, which corresponds to about half the average longevity of a larger vertebrate animal species. This is incredibly short in geological and biological terms and does not allow for the required genetic changes to have originated by an unguided process. This waiting time problem of neo-Darwinism is proven by population genetic calculations, which is the subject on an ongoing research project by Discovery Institute scientists.
Even the time span of 4 million years that was implied by the previously known fossil record of Early Triassic ichthyosaurs is shockingly short, so much so that a friend and colleague of mine, who is a renowned expert on ichthyosaurs and neither a theist nor an advocate of intelligent design, confidentially told me that he came to doubt the neo-Darwinian explanation for this very reason. He said: “That this transition happened by a Darwinian mechanism in such a short time is simply IMPOSSIBLE!” With this window of time now cut in half, the transition becomes even more incredible.
A Temporal Paradox
But there is another problem: The new discovery makes fully marine ichthyosaurs older than their alleged amphibious relatives such as Cartorhynchus (Motani et al. 2015, Jiang et al. 2016) and likely older than their unknown terrestrial relatives. This creates a temporal paradox of assumed descendants appearing before their assumed stem group. Thus, ichthyosaurs joined the numerous other examples of such paradoxes, such as early tetrapods or early birds. Not exactly a success story for Darwinism.
With increasing knowledge of the fossil record, the mainstream narrative is rendered more and more untenable and inconsistent with the empirical evidence. It’s time to move on and consider more adequate explanations like intelligent design theory.
References
- Jiang DY, Motani R, Huang JD et al. 2016. A large aberrant stem ichthyosauriform indicating early rise and demise of ichthyosauromorphs in the wake of the end-Permian extinction. Scientific Reports 6: 26232, 1–9. DOI: https://doi.org/10.1038/srep26232
- Kear BP, Engelschiøn VS, Hammer Ø, Roberts AJ & Hurum JH 2023. Earliest Triassic ichthyosaur fossils push back oceanic reptile origins. Current Biology 33(5), 178–179. DOI: https://doi.org/10.1016/j.cub.2022.12.053
- Motani R, Jiang DY, Chen GB et al. 2015. A basal ichthyosauriform with a short snout from the Lower Triassic of China. Nature 517, 485–488. DOI: https://doi.org/10.1038/nature13866
- Uppsala University 2023. Oldest sea reptile from Age of Dinosaurs found on Arctic island. Phys.org March 13, 2023. https://phys.org/news/2023-03-oldest-sea-reptile-age-dinosaurs.html
A Unique Window Into the Past – Ancient Jurassic Shark Fossil Reveals Surprising Evolutionary Truth
Fossil of the Late Jurassic shark Protospinax annectans from Solnhofen and Eichstätt, Germany. Credit: Sebastian Stumpf
The evolutionary history of sharks and rays has been illuminated by a recently constructed phylogenetic tree.
A recent study by an international team of researchers, led by paleobiologist Patrick L. Jambura from the University of Vienna’s Department of Palaeontology, has revealed that cartilaginous fish have undergone more evolutionary changes than previously thought. The evidence for this conclusion was obtained from new fossils of a shark-like ray called Protospinax annectans, which show that sharks were highly evolved during the Late Jurassic period. The findings of the study have been published in the journal Diversity.
Sharks, rays, and ratfish are a group of ancient animals known as cartilaginous fishes, which have been present on earth for over 400 million years, predating the dinosaurs. They have also endured all five mass extinctions and their fossil remains can be found globally in great quantities. However, typically only their teeth remain intact as the cartilaginous skeleton decays along with the rest of the body and does not fossilize.
A unique window into the past
In the Solnhofen archipelago, a so-called “Konservat Lagerstätte” in Bavaria, Germany, skeletal remains and even imprints of skin and muscles of Late Jurassic vertebrates (including cartilaginous fishes) have been preserved due to special preservation conditions. The research team used this circumstance to take a closer look at the previously unclear role of the already extinct species Protospinax annectans in the evolution of sharks and rays, also with the help of modern genetic evidence.
Paleoreconstruction of the Solnhofen Archipelago 150 million years ago showing Protospinax annectans and the Jurassic ray Asterodermus platypterus. Credit: Manuel Andreas Staggl
“Protospinax carried features that are found in both sharks and rays today,” explains study author Patrick L. Jambura. Protospinax lived some 150 million years ago and was a 1.5-m-long, dorso-ventrally flattened cartilaginous fish with expanded pectoral fins and a prominent fin spine in front of each dorsal fin. Although known from well-preserved fossils, the phylogenetic position of Protospinax has puzzled researchers ever since it was first described in 1918
“Of particular interest,” Jambura continued, “is whether Protospinax represents a transition between sharks and rays as a ‘missing link’ — a hypothesis that has gained considerable appeal among experts over the past 25 years.”
Alternatively, Protospinax could have been a very primitive shark, an ancestor of rays and sharks, or an ancestor of a certain group of sharks, the Galeomorphii, which includes the great white shark today — all of which are exciting ideas whose plausibility has now been clarified by scientists.
One mystery solved, another one remains
Incorporating the latest fossil finds, Jambura and his international team reconstructed the family tree of extant sharks and rays using genetic data (mitochondrial DNA) and embedded fossil groups — including Protospinax annectans — using morphological data. The results of the analysis were startling: Protospinax was neither a “missing link” nor a ray nor a primitive shark — but a highly evolved shark.
“We tend to think of evolution like a hierarchical, ladder-like system, in which older groups are at the base, while humans, as a very young species in Earth’s history, are at the top. In truth, however, evolution has never stopped even for these primitive representatives, but they continue to evolve day by day via changes in their DNA, just as we do. This is the only way they have been able to adapt to constantly changing environments and survive to this day,” says Jambura.
Even though cartilaginous fishes as a group have survived to this day, most species disappeared during their evolution, including Protospinax. Why Protospinax became extinct at the Jurassic-Cretaceous boundary some 145 million years ago and why there are no comparable shark species today, while the ecologically similarly adapted rays exist relatively unchanged to this day, remains a mystery at this point.
Reference: “Systematics and Phylogenetic Interrelationships of the Enigmatic Late Jurassic Shark Protospinax annectans Woodward, 1918 with Comments on the Shark–Ray Sister Group Relationship” by Patrick L. Jambura, Eduardo Villalobos-Segura, Julia Türtscher, Arnaud Begat, Manuel Andreas Staggl, Sebastian Stumpf, René Kindlimann, Stefanie Klug, Frederic Lacombat, Burkhard Pohl, John G. Maisey, Gavin J. P. Naylor and Jürgen Kriwet, 21 February 2023, Diversity.
DOI: 10.3390/d15030311
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