Back to Search
Start Over
Age and growth in Myledaphus bipartitus, a Late Cretaceous freshwater guitarfish from Alberta, Canada
- Source :
- Canadian Journal of Earth Sciences. September 1, 2013, Vol. 50 Issue 9, p930, 15 p.
- Publication Year :
- 2013
-
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. Myledaphus bipartitus est un poisson-guitare d'eau douce du Cretace tardif (75 Ma) communement represente par des dents et des centres vertebraux. L'espece a ete decrite pour la premiere fois en 1876, mais jusqu'a present, les connaissances sur son ecologie et son cycle de vie etaient tres limitees. Nous en avons analyse l'age et la croissance a la lumiere de 117 centres fossilises (74 hemisectionnes) des Formations d'Oldman et de Dinosaur Park du sud de l'Alberta. L'age maximum ainsi estime etait de 16 ans. La distance radiale (RD) au taux de croissance asymptotique estime a ete calculee, et les RD moyennes a la naissance et a trois ans ont ete comparees a celles de deux especes marines actuelles de Rhinobatos (R. productus et R. rhinobatos). La taille des anneaux a la naissance, en termes de RD, va de 0,9 mm a 1,8 mm. A 3 ans, la RD des centres va de 2,8 mm a 4,6 mm pour M. bipartitus et est significativement plus faible que celles de R. productus et R. rhinobatos (RD de 5,0-6,6 mm). Myledaphus s'approche de la croissance << asymptotique >> a une RD de 7,8 mm dans l'equation de croissance. La trajectoire de croissance de Myledaphus presente une pente semblable a celle des especes de Rhinobatos, bien qu'avec des RD des centres significativement plus faibles. La duree de vie de Rhinobatos rhinobatos surpasse egalement de 8 ans celle de Myledaphus. [Traduit par la Redaction]<br />Introduction Myledaphus bipartitus, Cope, 1876, is a Late Cretaceous enigmatic freshwater batoid represented predominantly by isolated teeth (Cappetta 2012). It is known from various Campanian formations such as the Oldman [...]
- Subjects :
- Aging -- Research
Company growth
Earth sciences
Subjects
Details
- Language :
- English
- ISSN :
- 00084077
- Volume :
- 50
- Issue :
- 9
- Database :
- Gale General OneFile
- Journal :
- Canadian Journal of Earth Sciences
- Publication Type :
- Academic Journal
- Accession number :
- edsgcl.341819592
- Full Text :
- https://doi.org/10.1139/cjes-2013-0001