Schumacher, Bruce A, Shimada, Kenshu, Liston, Jeff and Maltese, Anthony (2016) Highly specialized suspension-feeding bony fish Rhinconichthys (Actinopterygii: Pachycormiformes) from the mid-Cretaceous of the United States, England, and Japan. Cretaceous Research, 61. pp. 71-81. ISSN 0195-6671

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We re-define the Cretaceous bony fish genus Rhinconichthys by re-describing the type species, R. taylori, and defining two new species; R. purgatorensis sp. nov. from the lowermost Carlile Shale (middle Turonian), southeastern Colorado, United States, and R. uyenoi sp. nov. from the Mikasa Formation (Cenomanian), Middle Yezo Group, Hokkaido, Japan. Rhinconichthys purgatoirensis sp. nov. is designated on a newly discovered specimen consisting of a nearly complete skull with pectoral elements. Only known previously by two Cenomanian age specimens from England and Japan, the North American specimen significantly extends the geographic and stratigraphic range of Rhinconichthys. The skull of Rhinconichthys is elongate, including an expansive gill basket, and estimated maximum body length ranges between 2.0 and 2.7 m. Rhinconichthys was likely an obligate suspension-feeder due to its derived cranial morphology, characterized by a remarkably large and elongate hyomandibula. The hyomandibula mechanically acts as a lever to thrust the jaw articulation and hyoid arch both ventrally and anterolaterally during protraction, thus creating a massive buccal space to maximize filtering of planktonic prey items. Cladistic analysis supports a monophyly of suspension-feeding pachycormids including Rhinconichthys, but further resolution within this clade will require more information through additional fossil specimens.

Item Type: Article
Uncontrolled Keywords: Cenomanian; Osteichthyes; Pachycormid; Phylogeny; Planktivory; Turonian
Subjects: D History General and Old World > DA Great Britain
D History General and Old World > DS Asia
E History America > E151 United States (General)
Q Science > QE Geology
Q Science > QL Zoology
Theme: Understanding the natural world
Department: Natural Sciences
Related URLs:
Depositing User: Ross Anderson
Date Deposited: 23 Sep 2016 16:42
Last Modified: 04 Oct 2017 16:07

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