The teeth of archaic whales were as sharp as those of terrestrial predators, and thus were capable of capturing and processing prey, according to new research published in the journal Biology Letters.
Reconstruction of the ancient toothed whale Janjucetus. Image credit: Carl Buell.
“Contrary to what many people thought, it seems that that whales never used their teeth as a sieve, and instead evolved their signature filter feeding strategy only later — maybe after their teeth had already been lost,” said lead author Dr. Alistair Evans, a senior lecturer at Monash University and an honorary associate at Museum Victoria.
To find out what the teeth of archaic whales were really capable of, Dr. Evans and co-authors compared them to both filter feeding seals and a range of modern predators, like dingoes and lions.
“We first generated high-resolution 3D surface models of the cheek teeth of five modern pinnipeds (including leopard and crabeater seals), four terrestrial carnivorans, and eight fossil cetaceans (five toothed mysticetes, including Janjucetus and Coronodon; the fossil shark-toothed dolphin Squalodon; and two archaeocetes),” the researchers explained.
“For each tooth, we then measured the sharpness of the anterior, posterior, labial and lingual sides of the main cusp, the tip of the main cusp and the first posterior notch.”
“Next, we scaled all measurements and subjected them to principal component analysis to determine which extant tooth morphologies and feeding styles fossil cetaceans most closely associate with.”
“Finally, we used Discriminant Function Analysis to distinguish extant tooth morphologies used for raptorial and suction filter feeding.”
Comparison of the postcanine teeth of the dingo (Canis lupus), with that of the crabeater seal (Lobodon carcinophaga), an extant seal known to employ tooth-based suction filter feeding, and the extinct toothed mysticete Janjucetus. Note the sharp cutting edges in the dingo and Janjucetus. 3D surface models not to scale. Image credit: Carl Buell / Hocking et al, doi: 10.1098/rsbl.2017.0348.
The team found that ancient whales had sharp teeth similar to lions and dingoes.
“It’s likely they used their teeth to kill rather than filter,” Dr. Evans said.
“Predators that kill and chew their prey need sharp teeth with cutting blades. By contrast, species that use their teeth as a sieve have blunt teeth with rounded edges that help to filter prey from water.”
“Our findings provide crucial new insights into how the biggest animals ever evolved their most important trait — filter feeding,” he said.
“Filter feeding is the defining trait of modern whales. There are few ways in which this unique strategy could have evolved from tooth-bearing, predatory ancestors, and our study firmly rules out one of them.”
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David P. Hocking et al. 2017. Ancient whales did not filter feed with their teeth. Biology Letters 13 (8): 20170348; doi: 10.1098/rsbl.2017.0348
