[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Leedsichthys paper and news stories



(A 50-foot fish!  Pfffttt.  You should've seen the one that got away!)


_Leedsichthys_ and other planktivorous members of the Pachycormidae
were certainly the most abundant large filter-feeding planktivores in
the Mesozoic.  But there is evidence (albeit weak) of other large
planktivores in the Mesozoic, including even earlier than known
pachycormids.  These include cartilaginous fishes (Neoselachii = crown
sharks) from the Late Triassic and Late Cretaceous.  The teeth of
these putative filter-feeding sharks superficially resemble those of
the extant basking shark (_Cetorhinus_) and megamouth (_Megachasma_),
respectively, even though it is doubtful whether they belong to modern
shark families (especially in the case of the former).  But they might
indicate the existence of filter-feeding neoselachians in the
Mesozoic, before other planktivorous neoselachians appear in the
Cenozoic (cetorhinids, megachasmids, rhincodontids, mobulids), as well
as baleen whales (Mysticeti).


It is odd that no large reptiles apparently occupied this niche, not
even shastasaurid ichthyosaurs or stomatosuchid crocodyliforms
(despite suggestions that they were filter-feeding planktivores).  In
the Mesozoic, marine non-tetrapods appear to have cornered the market.




On Tue, Aug 27, 2013 at 9:24 AM, Ben Creisler <bcreisler@gmail.com> wrote:
> From: Ben Creisler
> bcreisler@gmail.com
>
>
> A recent non-dino paper about the gigantic fish Leedsichthys and some
> related news stories:
>
>
> Jeff LISTON, Michael G. NEWBREY, Thomas James CHALLANDS and Colin E.
> ADAMS (2013). Growth, age and size of the Jurassic pachycormid
> Leedsichthys problematicus (Osteichthyes: Actinopterygii) : 145–175;
> in ARRATIA, Gloria, Hans-Peter SCHULTZE & Mark V. H. WILSON (editors)
> (2013): Mesozoic Fishes 5 – Global Diversity and Evolution:
> Proceedings of the international meeting Saltillo, 2010:  560 pp.
>
> Contents with pdfs:
>
> http://www.pfeil-verlag.de/07pala/d4_59a.php
>
> Leedsichthys pdf is free at:
>
> http://www.pfeil-verlag.de/07pala/pdf/4_59d06.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.
>
>
> News stories:
>
> http://phys.org/news/2013-08-prehistoric-giant-fish-metres.html
>
> http://o.canada.com/2013/08/26/canadian-fossil-expert-helps-identify-biggest-fish-ever-known/
>
> http://www.heraldscotland.com/news/home-news/researchers-reveal-the-worlds-biggest-fish.21969545
>
> http://www.theguardian.com/science/2013/aug/25/scale-jurassic-giant-fish-uncovered