Wednesday, July 20, 2011

[Palaeontology • 2010] Rhinconichthys taylori • Giant Suspension-feeding Bony Fish from the lower Upper Cretaceous (Cenomanian), Kent, UK

(A) †Rhinconichthys taylori gen. et sp. nov.,
BMNH 219, from the lower Upper Cretaceous (Cenomanian) Lower Chalk of Kent, UK

Fig. 1 Newly recognized fossils of giant Mesozoic suspension-feeding bony fishes. (A) †Rhinconichthys taylori gen. et sp. nov., BMNH 219, from the lower Upper Cretaceous (Cenomanian) Lower Chalk of Kent, UK, in right- and left-lateral views. (B) Indeterminate edentulous †pachycormid, BMNH P.41669, from the lower Middle Jurassic (Bajocian) Inferior Oolite of Dorset, UK, in dorsal and ventral view (anterior is toward the top). Matrix has been digitally masked so as to enhance contrast, and preserved bone that would have been visible externally in the ventral and dorsal views is shaded in tentative reconstruction based on †Martillichthys and †Pachycormus. Scale bars apply only to fossils. boc, basioccipital; brs, branchiostegal rays; cbr, certobranchials; chy, anterior ceratohyal; de, dentary; dpt, dermopterotic; ent, entopterygoid; fr, frontal; gu, median gular; hhy, hypohyal; hym, hyomandibula; mtp, metapterygoid; mx, maxilla; psp, parasphenoid; rde, rostrodermethmoid; and scl, sclerotic ring. Paired bones are listed as right (r) or left (l).

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-Paleogene boundary, which is consistent with an opportunistic refilling of vacated ecospace.

Matt Friedman, Kenshu Shimada, Larry D. Martin, Michael J. Everhart, Jeff Liston, Anthony Maltese and Michael Triebold. 2010. 100-million-year Dynasty of Giant Planktivorous Bony Fishes in the Mesozoic Seas. Science. 327 (5968): 990–993. doi: 10.1126/science.1184743.