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Stonesfield theropod OUM J13506



    This left maxilla is intriguing. Rather than
recapitulate the 2 pages of osteological description
from my book-in-progress, I'll present the comparisons
with other taxa. The specimen: 478 mm long from the
tip of the rostromedial process, 464 mm from the front
of the lower tip. The tooth row is 356 mm long. The
specimen was part of the first restoration of a
theropod skull (John Phillips 1871, figs. 56-57). He
mistook the antorbital fenestra for the orbit, and
placed sclerotic rings in it, but no rings are known.
    Compared with the ceratosaur Walkersaurus hesperis
BMNH R332, it has a very different shape, the
subnarial plate differs in reaching the premaxilla
laterally. The nasal process is less far back. The
height of the caudal plate decreases less gradually.
The recess is shallower. There are 11 teeth in 320 mm
vs. 11 in 250 mm, but the teeth are larger and so are
more crowded. The teeth differ in the mesiolateral
bulging and basal medial thickening. The 4th vs. 5th
tooth is below the centre of the nasal process.
    Compared with Eustreptospondylus oxoniensis OUM
J13558, the rostral ramus is much shorter and higher,
and there is a gap between it and the premaxillae. The
rostromedial process is higher and not nearly
horizontal, differing in projecting in front of the
labial surface. There are 13 vs. 9 teeth. The maxilla
is much larger, higher, 108 vs. 57 mm high at the
front of the dorsal process.
    Compared with Metriacanthosaurus reynoldsi SDM
44.1 (S. Reynolds 1939, fig. 10), the rostral edge
dips more steeply rostrally. Although nearly the same
height below the naris, the rugosae in this area are
much higher so that the lingual surface above them and
below the rostromedial process is much lower. The
lingual bar is much lower. The rugosae are not as
separate and are lower caudally.
    Compared with Metriacanthosaurus reynoldsi BMNH
R8303, the rostral edge dips more steeply and the
caudal rugosae are lower.
    Compared with ?Metriacanthosaurus shangyouensis
CV00215-00216 (Dong, Zhou, Zhang 1983, figs. 45 & 54),
the maxilla has a similar abbreviated rostral process.
    Compared with Dromaeosaurus albertensis AMNH 5356
(E. Colbert & D. Russell 1969, figs. 1-4), both lack
narial emargination, but OUM J13506 differs in being
larger, with higher alveoli count, and in the presence
of rugosae.
    Only one other maxilla has been assigned to 
Megalosaurus bucklandii, OUM J13559, figured also with
photographs in my book-in-progress, and is not
distinguishable from OUM J13506. It lacks its
rostroventral tip, but has more of the surface
preserved than OUM J13506.
    Currie and Zhao in 1994, positioned
Yangchuanosaurus in Sinraptoridae, on the basis of the
"arrangement of the accessory fenestra in the
antorbital fossa", but did not, of course, analyze the
hypodigms of the Megalosauridae as I have constituted
it. Recent efforts to use Megalosauridae without
Megalosaurus bucklandii are, needless to say, not
tenable. Not acceptable, too, is the opinion that
Megalosaurus bucklandii must be restricted to
Buckland's mandible (neither Buckland nor von Meyer
chose a type specimen; it is OUM J13505, the rostral
right dentary + the kleptotype specimens listed
below), nor do I accept the opinions that Buckland's
original figures of a partial skeleton are not from
the same individual. Sam Welles (to whom I owe much,
not the least of which is having all of his negatives
and mss.) spent more time with these hypodigms than
anyone. On the basis of actually sitting at a table,
and reconstructing the Buckland bones into one
individual, was convinced OUM J13505, 13577, 13576,
13579, 29881, 13563, 13565, 13561, 13572 was ONE
individual, regardless of the fact that Buckland
himself kept no notes. However, as Sam stressed to me
time and again: he was able to satisfy himself this
was one individual because none of the other OUM/BMNH
elements matched in size and colour of matrix the
Buckland illustrations and the specimens themselves.
"They fit together", he said to me.
   Megalosauridae consists of Megalosaurus (including
Torvosaurus), Metriacanthosaurs, Eustreptospondylus,
and Poecilopleuron/Poekilopleuron (the former
spelling, it seems to me, will prove to have priority,
as the earliest publication I am aware of uses it,
although I am still awaiting word on elusive pre-1838
abstracts). 




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