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RE: Plesiosaurs made furrows

From: Ben Creisler

See this article in Tetrapod Zoology on the topic, which has citations:

Who made the giant Jurassic sea-floor gutters?
Posted on: December 16, 2009 5:21 AM, by Darren Naish



Geister, Jörn (1998)
 Lebensspuren von Meersauriern und ihren Beutetieren im mittleren Jura
(Callovien) von Liesberg, Schweiz, (Lebensspuren made by Marine
Reptiles and their Prey in the Middle Jurassic (Callovian) of
Liesberg, Switzerland)
FACIES  39:105-124

Numerous gutter-like furrows, up to 60 cm wide and up to 9 m long are
preserved at the interface "Macrocephalus Beds" I "Callovian Marl"
over a surface of 20 by 200 m. They are interpreted as feeding traces
made by large marine vertebrates, most likely plesiosaurs and
ichthyosaurs searching for food in the lime mud of the shallow Middle
Jurassic sea floor. Possible prey animals were in faunal invertebrates
(crustaceans) which produced an intricate meshwork of burrows (mainly
Rhizocoralliurn irregulare and Thalassinoides) in the bottom
sediments, as well as infaunal bivalves. Evidence from coprolites of
predatory pelagic reptiles (ichthyosaurs, plesiosaurs) as well as
reptile regurgitalites indicate that these animals fed not only on
fast-swim-ming vertebrates and cephalopods but also on epi- and
endobenthic invertebrates. In addition, the cololites show that the
predators ingested considerable amounts of bottom sediment. Different
sizes and shapes of the traces suggest that the gutters were produced
by different reptiles or age groups. Candidates for the widest gutters
are pliosaurs. Of the marine vertebrates known from Jurassic time,
only the snout of adult pliosaurs of the genus Liopleurodon was broad
enough to produce gutters more than 40 cm wide. Smaller, less than 15
cm wide gutters, could have been made by plesiosauroids or by the
narrow pointed snouts of ichthyosaurs. Almost identical traces
described from the Oxfordian of Spain and similar but smaller traces
from the Lower Devonian of Prague are equally interpreted as feeding
traces on the sea floor. Feeding traces of vertebrates in bottom
sediments may give detailed information on the hunting behaviour of
the predators. However, the attribution of the traces to definite
vertebrate taxa remains uncertain.