Age and growth in Myledaphus bipartitus, a late Cretaceous freshwater guitarfish from Alberta, Canada

Alycia E. Wilson, Michael G. Newbrey, Donald B. Brinkman, Todd Donald Cook, Andrew G. Neuman

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

Myledaphus bipartitus is a Late Cretaceous (75 Ma) freshwater guitarfish, commonly represented by teeth and vertebral centra. The species was first described in 1876, but until now, very little has been known about its ecology and life history. We analyzed the age and growth using 117 fossilized centra (74 hemisectioned) from the Oldman and Dinosaur Park formations of southern Alberta. The resulting estimated maximum age was 16 years. Radial distance (RD) at the estimated asymptotic growth was calculated, and average RD at birth and 3 years were compared with two extant marine species of Rhinobatos (R. productus and R. rhinobatos). Birth ring size ranged from 0.9 to 1.8 mm RD. At age three, centrum RD was between 2.8 and 4.6 mm RD for M. bipartitus and significantly less than R. productus and R. rhinobatos (5.0-6.6 mm RD). Myledaphus approached "asymptotic" growth at 7.8 mm RD in the growth equation. The growth trajectory of Myledaphus had a similar slope to the Rhinobatos species, but with significantly smaller centrum RD. Rhinobatos rhinobatos also outlived Myledaphus by 8 years.

Original languageEnglish (US)
Pages (from-to)930-944
Number of pages15
JournalCanadian Journal of Earth Sciences
Volume50
Issue number9
DOIs
StatePublished - Aug 6 2013

All Science Journal Classification (ASJC) codes

  • Earth and Planetary Sciences(all)

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