| Filter feeding vertebrates are the largest organisms | | | | filter feeding and large body size go back at least |
| swimming in modern oceans. Filter feeding involves | | | | another 100 million years, into the middle of the |
| adaptations for processing large quantities of sea | | | | Mesozoic. |
| water through the mouth, with some mechanism for | | | | This group of large fish belong to an extinct family |
| filtering out the countless small planktonic creatures | | | | called the Pachycormidae, with the newest member of |
| that live in the water to swallow. It turns out that this is | | | | the family named Bonnerichthys. While the fossils of |
| a very lucrative activity for certain organisms that can | | | | these fish have been in museums for many decades, |
| grow very large by eating the very small. | | | | they have been hard to interpret and have remained |
| For example, the largest animal ever known is not a | | | | poorly understood. The new work, along with some |
| dinosaur, but the modern blue whale, which reached | | | | new fossil finds, have clarified these fish, and opened |
| lengths of over 100 feet and can weigh 380,000 | | | | up our understanding of the past. |
| pounds. It belongs to a group of whales called the | | | | The new work shows that this family of fish spanned |
| baleen whales which gulp large amounts of water into | | | | from the Late Jurassic until the end of the Cretaceous. |
| their mouths, and push the water back out of their | | | | Their fossil remains have been found in Kansas as |
| mouths with their large tongue through a filtering series | | | | well as Europe. We have now put together the pieces |
| of brushes, or baleen. Then, they simply swallow | | | | of the puzzle, filling in a huge gap in scientific |
| whatever is left behind. | | | | knowledge of the Mesozoic seas. An important niche, |
| The largest modern fish is the whale shark. This big | | | | the large-bodied filter feeders, was filled in the past for |
| fish reaches over 40 feet long and weighs about | | | | millions of years by the pachycormid fish. This |
| 47,000 pounds, but unconfirmed accounts exist of | | | | resource of the oceans was utilized, and as today, the |
| much larger specimens. They filter water slightly | | | | fish were able to grow large. Bonnerichthys was about |
| differently than the whales. These fish swim forward | | | | 25 feet long, and its cousin. Leedsichthys was perhaps |
| and let the water flow past gill rakers, structures | | | | slightly larger. You can see more about Bonnerichthys |
| designed to trap plankton. | | | | at the Oceans of Kansas website, and listen to an |
| The niche of large-bodied filter feeding animals is today | | | | interview with Matt Friedman, principle author of the |
| occupied by things like the baleen whales, and certain | | | | new study, on NPR. |
| sharks and rays. The fossil evidence for this behavior | | | | At the end of the Age of Dinosaurs these fish |
| seems to start in the Cenozoic, after the Age of | | | | became extinct, along with dinosaurs and other large |
| Dinosaurs. Where there really no filter feeders during | | | | marine reptiles. It took several million years, but |
| the Mesozoic? | | | | eventually the rich planktonic resource was utilized |
| Until recently, there seemed to be none. However, a | | | | again by some sharks and whales, which moved into |
| recent paper in the journal Science clarifies that in fact, | | | | the role the pachycormid fish left open. |