Missing Links Found: Walking Seal, Teen Tyrannosaur
Science news media are abuzz with reports that two missing links have been found. One is a fossil seal (pinniped) with four legs, the other a smaller presumed ancestor of the famous Tyrannosaurus rex.
- Seal: National Geographic News calls it a seal with arms, and features artwork of an otter-like animal doing a kind of dog paddle with webbed fingers on the way to becoming flippers. The BBC News announced, “Missing link fossil seal walked,” and said “the 23 million-year-old proto-seal would have walked on land and swum in fresh water.” The discoverers named it Puijila darwini in honor of Charles Darwin, “who wrote with his usual prescience, ‘A strictly terrestrial animal, by occasionally hunting for food in shallow water, then in streams or lakes, might at last be converted into an animal so thoroughly aquatic as to brave the open ocean.’”
Analysis of the paper in Nature revealed several problems with these claims.1 For one, it’s not news. Another fossil from Europe, Potamotherium, is very similar in body proportions to this one, and no one was claiming that was a missing link to pinnipeds. Another problem is that the authors’ own phylogeny chart shows this animal as a contemporary with Potamotherium and Enaliarctos, the oldest known pinniped fossils, which already had flippers and the body proportions of modern seals. In fact, the “more highly derived” pinniped Enaliarctos dates to the Oligocene, the period prior to the Miocene in which Puijila was discovered, “and not long before a significant radiation of other early marine pinnipeds.” This seems to represent an abrupt appearance of fully-flippered pinnipeds alongside if not before the appearance of Puijila. If anything, Puijila represents an extinct sister lineage of extant seals. “Puijila itself appears to be a relict stem pinniped,” the authors stated in the paper. A third problem is that these sister fossils are found from different parts of the world. Puijila was found in the Arctic near Greenland, Potamotherium in Europe, and Enaliarctos on the northwest shores of North America. It seems implausible these contemporaneous creatures migrated to such distant parts of the world on their evolutionary path. Finally, other mammals were found in the lake bed habitat: a rabbit, a shrew, an artiodactyl and a rhinoceros. None of them seemed to be evolving into swimmers to adapt to the aquatic habitat.
The discoverers of a new fossil often have a difficult time classifying it. That was the case here: “Taken together,” they said after describing the bones, “the dental, cranial and postcranial characters of Puijila suggest that a phylogenetic analysis including Amphicticeps shackelfordi, Potamotherium valletoni and Enaliarctos would be appropriate.” This is usually followed by some tweaking and fitting of the animal into a phylogenetic tree. They chose to run a parsimony analysis using PAUP software (Phylogenetic Analysis Using Parsimony), version 4.10b. It gave them a cladogram based on the eight most “parsimonious” trees. The software also avoided an undesirable processing artifact called “long branch attraction” that often doesn’t yield the desired evolutionary relationships – suggesting that a fair amount of subjectivity entered into the conclusions; after all, nature may not be so parsimonious at times. Even then, the resulting tree did not suggest any kind of ancestral relationship between the three stem lineages, one of which was already a “more highly derived” pinniped from earlier in the fossil record.
It seems the authors got a little carried away with the missing-link interpretation in an effort to patch up an embarrassing gap. “With Enaliarctos considered the earliest pinniped, there exists a major transformational gap between a terrestrial ancestor and the appearance of flippered pinnipeds,” they admitted in the introduction. “Indeed, most studies of pinniped relationships and evolution do not consider the critical first evolutionary stages that ultimately gave rise to this successful group of marine carnivores.” Enter Puijila, a “small mammalian carnivore,” to the rescue: “Puijila is a morphological intermediate in the land-to-sea transition of pinnipeds and provides new evidence concerning the evolution and biogeography of the earliest pinnipeds.” Notice they said morphological intermediate, not temporal intermediate. Sisters do not ancestors make.
Nevertheless, the news media overlooked these problems and hyped the “missing link” angle, aided by the artwork, movies, audio files, Flash multimedia and Powerpoint slides provided by the authors. National Geographic News announced “Evolution at Work” in the Arctic, the new “hotbed of evolution.” Andrea Thompson, senior writer for Live Science, was swept off her feet. She announced, “Walking Seal Called Missing Link in Evolution” and quoted the senior author saying, “This discovery supports the hypothesis that the Arctic may have been a geographic center in pinniped evolution.” Like the authors of the paper in Nature, Thompson decorated her triumphant article with the imprimatur of Darwin (see quote above), suggesting his prediction has now been vindicated.
- Tyrannosaur: The news media are also celebrating a missing link of T. rex. The BBC News announced, “Ancestor of T rex found in China” and used the suggestive evolutionary catch-phrase “missing link.” Similarly, Live Science said the new fossil “Fills Evolutionary Gap.” What was found?
The original paper was published in the Proceedings B of the Royal Society.2 Makovichy et al named their new ornithomimosaur Beishanlong grandis. Initially, it might seem odd that the ancestor of a North American giant was vacationing in China, but the authors noted that strange evolutionary things were going on there and then. The five-foot-tall creature that is said to have lived 125 million years ago “provides evidence for the parallel evolution of gigantism in separate lineages of beaked and possibly herbivorous coelurosaurs within a short time span in Central Asia. Clearly, size matters, and China was the place to be if you wanted to evolve or perish.
The skeleton was not complete. No head was found. Only a scapula and parts of the legs and arms from two individuals were available for study. It appears one of them was a juvenile, since growth rings show it was still growing when it died.
The usual forcing and fitting into an evolutionary tree was conducted. These authors relied on a “strict consensus of the results of a larger analysis of 293 characters in 72 theropod taxa conducted with the program TNT.” The new fossil has many similarities to another named Harpymimus. Since no one can observe the lifestyle of extinct creatures, nor the morphological developmental changes during their growth (think of flatfish), nor the range of variation within species, there is inherent subjectivity in their classification from fossils alone. To see this subjectivity in the original language, consider this paragraph (focus on the reasoning, not the technical terms):
Beishanlong and Harpymimus are very similar throughout the preserved skeletal parts common to both, although many of these traits are plesiomorphic [i.e., prior to the last common ancestor]. Both retain ginglymous distal articulations on metacarpal I (inferred from phalanx I-1 in Beishanlong), a deep ligament pit on metacarpal III and a strongly curved pollex claw, but straighter claws on other digits. Both taxa possess a subarctometatarsal foot with the diaphysis of metatarsal III pinched dorsally and exhibits a wedge-like exposure on the ankle, although this condition persists in Garudimimus (Kobayashi 2005) and the feet of Pelecanimimus and Shenzhousaurus are unknown. Of considerable interest in this regard is the keeled condition of two of the caudal vertebrae of Beishanlong and the near-keeled condition of caudal vertebrae in a juvenile ornithomimosaur specimen possibly referable to Harpymimus (Y. Kobayashi 2002, unpublished data). In the latter specimen (IGM 100/960910KD), the preserved caudals bear relatively taller neural spines and transverse processes compared with the mid-caudals of Beishanlong, so it is possible that the lack of haemal groove may be related to their position in the caudal series rather than representing a taxonomic difference. Although mid-caudal vertebrae of Garudimimus are unknown, those of other ornithomimosaurs do not exhibit a ventral midline keel or keel-like anatomy, so this trait could represent a possible synapomorphy [i.e., trait present in the last common ancestor] uniting Beishanlong and Harpymimus as sister taxa.
(Read this Cladistics reference article about the terms and decisions paleontologists make.) It is evident that the skeleton does not jump out and announce its ancestry. Presumably other researchers, with other software and other outgroups and other lists of taxa to include, could arrive at different conclusions. This team chose to emphasize the differences between the new fossil and the older one – though they mentioned that theirs was from an actively growing subadult, and the other was from a mature individual. And lest anyone believe evolutionary trends are straightforwardly apparent in the fossil record, they examined various lines of evidence that “suggest that this lineage did not follow a directional trend of body-size evolution such as has recently been shown for some paravian lineages.” In biology, real data are messy. One other surprise was noted: “It is remarkable that such body-size shifts in three different coelurosaurian lineages are so tightly clustered geographically and stratigraphically.” Was something else going on?
And where did the tyrannosaur missing link idea come from? The authors did not draw that conclusion in their paper. In fact, they said, “The holotype of Beishanlong co-occurs with therizinosauroids, hadrosauroids, turtles and tyrannosauroids in the lower mesic faces of Xinminpu Group…, and a strong and remarkably invariant degree of faunal association between these particular clades persists in mesic environments throughout the Cretaceous….” Here again, if tyrannosauroids were living alongside this creature, it seems unwarranted for the BBC News and Live Science to call Beishanlong an ancestor to T. rex. Linguists might note with interest that the suffix “-long” in Chinese means “dragon.”
1. Natalia Rybczynski, Mary R. Dawson, and Richard H. Tedford, Nature 458, 1021-1024 (23 April 2009) | doi:10.1038/nature07985.
2. Makovichy et al, “A giant ornithomimosaur from the Early Cretaceous of China,” Proceedings of the Royal Society B, Published online before print April 22, 2009, doi: 10.1098/rspb.2009.0236.
We need to coin a new law of nature: evolutionary hype is inversely proportional to the empirical data available. Write in your suggestion for the person whose name should grace this law. The Darwiniacs went into a frenzy inventing ways to take a few millimeters of bone here, or a slight proportion there, into trinkets to offer their idol, Charles Darwin.
You should know that Creation-Evolution Headlines strives to give each scientist a fair hearing. Scanning the hyperbole in the headlines, the initial reaction was to think, “Well, it seems the Darwinians may have scored some points.” Unlike the majority of lay people who lack the time, patience and access to the original papers to investigate the grounds for the claims, we take the time and show you, in their own words, how solid it is. As you can see, the grand picture looks more like a hologram, full of light and color, but low on substance, or like the shadows of a man’s hand making animal silhouettes projected onto hundred-foot monsters of shadow and light on the walls of a skyscraper.
You saw what they did: assume evolution, observe a fact, and make up a story to fit the fact into the assumption of evolution. That’s how they always do it. Nothing about these discoveries jumps up and says, “Charlie was right!” Even a young-earth creationist paleontologist would have no heartburn over this. You could take living animals – a skunk, an otter, a beaver and a seal – and arrange them into a phylogenetic tree. One little detail we found in their own tree was that they used the same shape for Puijila, Potamotherium and an outlier unrelated to them all. What kind of evolution is that? The dinosaur fossil storytellers had even less data to connect their scattered bones with the headlines.
As usual, the original papers are full of uncomfortable little details that undermine their story. The damages are glossed over with highfalutin euphemisms, ad-hoc stories, and promises that it will all become clear someday in the future. This is how Darwinian science is done. Hire an artist to do a little visualization for you, give it to the press, and they will be overjoyed to dish it out to the masses as proof that King Charles is still on the throne. The peasants are revolting because the King’s protectors are so revolting.