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Giant Leedichthys and other fish papers (free pdfs)



From: Ben Creisler
bcreisler@gmail.com


A couple of recent fish-related papers that may be of interest:


Giant Leedichthys

Liston, J., Newbrey, M., Challands, T., and Adams, C. (2013)
Growth, age and size of the Jurassic pachycormid Leedsichthys
problematicus (Osteichthyes: Actinopterygii)
in: Arratia, G, Schultze, H and Wilson, M (eds.) Mesozoic Fishes 5 –
Global Diversity and Evolution. Verlag Dr.Friedrich Pfeil, München,
Germany, pp. 145-175.
ISBN 9783899371598 Publication date: 22 July 2013

Paper free pdf:
http://eprints.gla.ac.uk/81797/1/81797.pdf

The Jurassic pachycormid osteichthyan Leedsichthys problematicus is
renowned for having been able to achieve prodigious size for a bony
fish. Building on work of MARTILL (1986a), a thorough examination of
all known material was conducted in order to constrain estimates of
the size of this animal and examine its rate of growth. Important
specimens of Leedsichthys are described for the first time. The
histology of Leedsichthys is reviewed, and the presence of growth
annuli is used to establish ages for five specimens. Age and growth
data were obtained from gill rakers (n = 4) and lepidotrichia (n = 2).
Lepidotrichia show upward curvilinear growth profiles and ages ranging
from 21 to 40 annuli, which are assumed to represent years. Both
growth profiles start at a small size (0.26 and 0.33 mm radial
distance), which is assumed to represent age 1. However, annuli can be
lost near the margins of the elements. Gill rakers exhibit a sigmoidal
growth profile. Age of gill rakers was estimated by adjusting the
alignment of the inflection points of the growth profiles thereby
giving adjusted ages. Gill rakers ranged in age from 19–38 annuli, but
all show evidence of reabsorption of annuli near the focal points and
at the margins of most elements. Sizes for the five individuals range
from 8.0-16.5 m for ages of 19-40 years. Growth rate (0.01-0.05 K) was
relatively slow as expected for a large, long-lived fish. At age 1,
individuals were 1.6 m in length. Estimates for the length of L.
problematicus compare well with published lengths of other large
suspension feeders such as those for basking and whale sharks.

Press release:
http://www.bris.ac.uk/news/2013/9614.html

===
Thomas J. Near, Alex Dornburg, Ron I. Eytan, Benjamin P. Keck, W. Leo
Smith, Kristen L. Kuhn, Jon A. Moore, Samantha A. Price, Frank T.
Burbrink, Matt Friedman, and Peter C. Wainwright (2013)
Phylogeny and tempo of diversification in the superradiation of
spiny-rayed fishes.
PNAS 2013 (published ahead of print July 15, 2013)
doi:10.1073/pnas.1304661110
http://www.pnas.org/content/early/2013/07/10/1304661110.abstract?sid=bfd6b677-2c5c-4910-bfa8-138bfa77df67
pdf in open access:
http://www.pnas.org/content/early/2013/07/10/1304661110.full.pdf+html?sid=bfd6b677-2c5c-4910-bfa8-138bfa77df67

Spiny-rayed fishes, or acanthomorphs, comprise nearly one-third of all
living vertebrates. Despite their dominant role in aquatic ecosystems,
the evolutionary history and tempo of acanthomorph diversification is
poorly understood. We investigate the pattern of lineage
diversification in acanthomorphs by using a well-resolved
time-calibrated phylogeny inferred from a nuclear gene supermatrix
that includes 520 acanthomorph species and 37 fossil age constraints.
This phylogeny provides resolution for what has been classically
referred to as the “bush at the top” of the teleost tree, and
indicates acanthomorphs originated in the Early Cretaceous.
Paleontological evidence suggests acanthomorphs exhibit a pulse of
morphological diversification following the end Cretaceous mass
extinction; however, the role of this event on the accumulation of
living acanthomorph diversity remains unclear. Lineage diversification
rates through time exhibit no shifts associated with the end
Cretaceous mass extinction, but there is a global decrease in lineage
diversification rates 50 Ma that occurs during a period when
morphological disparity among fossil acanthomorphs increases sharply.
Analysis of clade-specific shifts in diversification rates reveal that
the hyperdiversity of living acanthomorphs is highlighted by several
rapidly radiating lineages including tunas, gobies, blennies,
snailfishes, and Afro-American cichlids. These lineages with high
diversification rates are not associated with a single habitat type,
such as coral reefs, indicating there is no single explanation for the
success of acanthomorphs, as exceptional bouts of diversification have
occurred across a wide array of marine and freshwater habitats.