1 Mar 2010 03:27
Giant plankton-eating fish of the Mesozoic
Tim Williams <tijawi <at> yahoo.com>
2010-03-01 02:27:07 GMT
2010-03-01 02:27:07 GMT
Not directly dinosaur-related, but interesting nonetheless because of the impact on marine Mesozoic ecosystems. A new paper in Science provides a reason for why there are no unambiguous plankton-eating reptiles in the Mesozoic: they were muscled out by big fishies. The following paper describes two new genera of planktivorous fishes (_Rhinconichthys_ and _Bonnerichthys_), part of a radiation of planktivorous stem teleosts (Pachycormidae) that continued to the end of the Cretaceous. Although certain plesiosaurs have been described as "filter-feeders" (e.g., _Aristonectes_, _Kaiwhekea_), with the small teeth and wide jaws used to strain out small prey, it's my understanding that this is not true "filter-feeding" (= suspension feeding). Instead, these plesiosaurs might have had a feeding strategy more like the crab-eater seal, which has sieve-like teeth for trapping krill. Friedman, M., Shimada, K., Martin, L.D., Everhart, M.J., Liston, J., Maltese, A., and Triebold, M. 100-Million-Year Dynasty of Giant Planktivorous Bony Fishes in the Mesozoic Seas. DOI: 10.1126/science.1184743 Science 327, 990 (2010). "Large-bodied suspension feeders (planktivores), which include the most massive animals to have ever lived, are conspicuously absent from Mesozoic marine environments. The only clear representatives of this trophic guild in the Mesozoic have been an enigmatic and apparently short-lived Jurassic group of extinct pachycormid fishes. Here, we report several new examples of these giant bony fishes from Asia, Europe, and North America. These fossils provide the first detailed anatomical information on this poorly understood clade and extend its range from the lower Middle Jurassic to the end of the Cretaceous, showing that this group persisted for more than 100 million years. Modern large-bodied, planktivorous vertebrates diversified after the extinction of pachycormids at the Cretaceous-Pa leogene boundary, which is consistent with an opportunistic refilling of vacated ecospace."
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