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STONESFIELD, ECHOLOCATION & LIFE OF MAMMALS
A few things that might be of interest in view of recent
It's funny that no one's been doing anything with megalosaurids
for ages; all of a sudden all hell breaks lose. As discussed, Allain
and Chure (2002) argue that more than one theropod taxon is
present in the Stonesfield Slate as indicated by different femora
and ilia in British collections. On this note I was a bit surprised
that they didn't mention the suggestion that OUM J13506, the left
maxilla described by Huxley (1869) and later incorporated by
Phillips (1871) into his skull reconstruction, is not from
_Megalosaurus_ but from a sinraptorid. This suggestion was
made by Bakker et al. (1992) in the _Edmarka_ paper and is based
on the abbreviated rostral ramus. A long megalosaurid-style
rostral ramus is not missing from the specimen as the rostral
margin, even with its rostromedial process, is intact.
Whether or not OUM J13506 is from a sinraptorid, it's clearly
from a theropod with a very different maxilla to that seen in
_Torvosaurus_, _Afrovenator_, _Poekilopleuron?
valesdunensis_ and _Walkersaurus hesperis_. It thus is almost
certainly not from a megalosaurid and thus also supports the
presence of more than one big theropod at Stonesfield.
Bakker, R. T., Kralis, D., Siegwarth, J. & Filla, J. 1992.
_Edmarka rex_, a new, gigantic theropod dinosaur from the
middle Morrison Formation, Late Jurassic of the Como Bluff
outcrop region. _Hunteria_ 2 (9), 1-24.
Huxley, T. H. 1869. On the upper jaw of _Megalosaurus_.
_Quarterly Journal of the Geological Society, London_ 25, 311-
Jaime covered most of the points but I don't recall him
mentioning the following. Echolocation requires directional
hearing and hence, in water, isolation of the ear bones from the
rest of the skull (otherwise all sounds are conducted through all
bones too quickly for the brain to effectively register the time
delay). Cetaceans have oil-filled sacs isolating their ear bones
from the rest of the skull. Mosasaurs (and other marine reptiles)
don't and presumably would have employed bone-conducted
The possibility of echolocation and/or high-frequency hearing has
been considered (in the literature) for all the Mesozoic marine
reptile groups and all the evidence indicates that
echolocation/HFH was not practised by these animals. Wade (see
below) reported the possible presence of a melon-like structure in
_Platypterygius_ but, while some ichthyosaurs possess a
frontoparietal concavity dorsal to the frontoparietal foramen, this
interpretation is probably not correct.
Wade, M. 1984. _Platypterygius australis_, an Australian
Cretaceous ichthyosaur. Lethaia 17, 99-113.
- . 1990. A review of the Australian Cretaceous longipinnate
_Platypterygius_ (Ichthyosauria, Ichthyopterygia). _Memoirs of
the Queesland Museum_ 28, 115-137.
Did anyone see episode II of _Life of Mammals_? This was about
insectivores (in the lose, generic sense) and included xenarthrans
and pangolins as well as lipotyphlans and bats. The reason I'm
mentioning this? Attenborough claimed that anteaters (s.s.) and
pangolins have gone pretty much unchanged for 40-odd million
years and.. cue Messel - he then showed fossils of
_Eurotamandua_ and _Eomanis_. Storch was credited as a
technical consultant so it seems that, despite Szalay and Shrenk
(1998), _Eurotamandua_ is still a myrmecophagid even though
it's been shown not to be. See...
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