Some of Earth’s Extinct Giant Animals May Have Been Smaller Than We Thought

Researchers now suggest that body size estimates for Earth's extinct giants may have been overly inflated. Methods of estimation have recently faced scrutiny, with the effectiveness of initial calculations called into question.

Reevaluating Dunkleosteus

Take Dunkleosteus, an ancient armored fish known for its formidable bite around 360 million years ago. Previously, it was believed to reach lengths of up to 10 meters, based on the large fossilized remains of its head. However, doubts about the head-to-body ratio employed in those estimates have caused scientists to reconsider. Recent analyses imply that Dunkleosteus might have actually measured only about half that length and had a more robust body, leading some researchers to refer to it as "Chunkleosteus."

A Shift in Perception

Similar reassessments are occurring across various other extinct species, emphasizing caution with size estimates. The studies discussed in the journal Ecology and Evolution highlight a growing trend of exaggeration in reported size. As evolutionary biologist Joel Gayford points out, these discussions often see initial claims of record-breaking sizes or weights quickly challenged by subsequent research, providing a more accurate view.

When assessing body sizes, sometimes the fossil evidence is limited. For instance, the notorious Otodus megalodon, the largest shark known, is only represented by teeth alone. Similarly, the ancient whale Perucetus supplied scant evidence, with only a few vertebrae and one pelvis available for study. Researchers often rely on comparisons to living relatives or employ evolutionary analyses, yet these methods introduce assumptions.

The Megalodon Dilemma

Gayford and colleagues scrutinized the Megalodon size estimates, which were previously linked to great white sharks. These assumptions led to a belief in a robust body structure, expected for a creature the size of 11 meters. A recent study has since revised this view, suggesting that Megalodon could be longer but more streamlined — more akin to a bus than a wide van.

The same caution applies to Perucetus, where newer calculations have redefined its weight. Ongoing debates have reduced the initial weight estimate from as much as 340 metric tons to about 100 metric tons. While this departs from the figures of massive, living blue whales, it remains a formidable size.

The Impact of Size Estimates

The credibility of these "spurious size estimates" can significantly influence perceptions about terrestrial and marine giants. As Gayford cautions, these inflated assessments may affect ecological dynamics, impact food resources, and alter predator-prey interactions. Natural alterations in habitats can result in cascading effects on these animals.

Paleontologists laud the research for bringing light to critical challenges in size estimation. Still, Jack Cooper, a vertebrate paleontologist, believes that not every case was analyzed with equal depth. He raises concerns over the report misrepresenting the replicability of his work on Megalodon, pointing out that accuracy in reporting is crucial for ongoing discussions in paleontology.

Reflecting on Research Trends

Gayford clarified that their comments referred to the rarity of relevant fossils and not a critique of Cooper’s findings. He notes the broader issue of research publication trends, where journals may favor dramatic findings over methodically sound conclusions.

He emphasizes that while size can captivate attention, the fascination with these creatures lies in their uniqueness. "The point is for people to understand that it’s not the size or the weight of an animal that makes it interesting," Gayford explains. "Much can still be learned from these significant, awe-inspiring creatures."

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