May 4, 2005 | David F. Coppedge

Toothy Dinosaur Goes Vegan

The news media all pounced on a dinosaur fossil discovery reported in Nature this week.1  Dinosaur finds are ever popular, and reporters especially like it when an artist’s rendition is available.  Some outlets reporting the discovery of Falcarius utahensis, a previously unknown species “in the process of converting to vegetarianism from a rather more bloodthirsty diet,” included BBC News, National Geographic, News@Nature, MSNBC, CNN, Science Now and Science Daily.
    The news media echoed the theme that this fossil represented a dinosaur “missing link” that was evolving from carnivory to herbivory.  What did the scientists actually report?  First of all, the new species was found in a fossil graveyard in Utah.  Second, it is the most complete of this class of dinosaurs, heretofore poorly represented with fragmentary characters, and is the first one found in North America (the best other representatives are from China).  Third, according to their dating method and phylogenetic analysis, “this species documents the earliest known stage in the poorly understood transition from carnivory to herbivory within Therizinosauroidea” (emphasis added in all quotes.)  The diet story is based on these findings announced by the discoverers:

Therizinosaurs are here proposed as shifting their dietary habit from predation to herbivory on the basis of the development of a number of features that seem convergent with clades of other herbivorous dinosaurs.  The most significant of these features include small, leaf-shaped teeth, an edentulous beak, posterior displacement of the pubis and lateral expansion of the pelvis associated with greatly increased intestinal volume, and shortening of the tibia relative to the femur and an increased number of weight-supporting pedal digits—the latter two being specific reversals of the cursorial condition.  Falcarius demonstrates the mosaic nature of this evolutionary transition, indicating that the dentition and pelvis were among the first hard-tissue structures to undergo modification.  These changes probably coincided with modifications in food acquisition and digestion during the early stages of therizinosauroid evolution.  Moreover, similarities between the dentition of the basal therizinosaur Falcarius and the basal oviraptorosaur Incisivosaurus, in combination with their proposed sister relationship (Fig. 3), raises the possibility that the common ancestor of these clades had already undertaken the initial steps in this transition.

The fossils of 10 individuals were found in a densely-packed bone bed about one meter thick and 8,000 meters in extent, “with bone densities in some areas exceeding 100 elements per cubic metre.”  Judging from extent of the bed, “perhaps hundreds of disarticulated individuals remain interred,” they say, with 99% of them this one species and traces of an unknown ankylosaur.
    The team used a computerized parsimony analysis to reconstruct the phylogeny of this species, but it left questions about the relationship with the Chinese sister group Eshanosaurs:

Falcarius casts further doubt on the affinities of Eshanosaurus by increasing its stratigraphic and phylogenetic inconsistency.  Given the discovery of North American members of the therizinosauroid clade, together with the poor record of Middle Cretaceous dinosaurs, it seems that the generally accepted hypothesis of an Asian origin and radiation for Therizinosauroidea requires additional testing.


1Kirkland et al., “A primitive therizinosauroid dinosaur from the Early Cretaceous of Utah,” Nature 435, 84-87 (5 May 2005) | doi: 10.1038/nature03468.

Researchers like details and big words, but the news media like slang and humor.  Researchers speak in tentative and reserved language, but news media like certainty.  The scientists here proposed an interpretation that these species, despite the poor fit within a “generally accepted” hypothesis and uncertain dating, that Falcarius was undergoing a dietary change, even though (1) the number of simultaneous morphological adaptations needed would be considerable, difficult to account for by chance mutations and natural selection, and (2) they had to invoke the multiply-improbable concept of “convergent evolution” to link these changes to those going on in other species.  These problems notwithstanding, perhaps the shape of teeth and pelvis suggested that these dinosaurs were in the midst of a transition from meat-eating to plant-eating.    That’s all the news media needed: a picture and a sound bite: “Fossil-hunters working in the dusty Utah desert have caught a dinosaur in the act of going vegetarian.”  *Sigh*.  Who do they think we are – children, who can’t handle the solid meat of data, and who cannot discern interpretations from evidence?  These dinosaurs were not sitting around experimenting on lettuce for dessert after their usual steak.  Get real; the herd was living within their well-adapted niche, when a flood suddenly came and buried them all.

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Categories: Dinosaurs, Fossils, Media

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