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Re: _Becklespinax_



In a message dated 97-02-18 13:50:58 EST, jdharris@post.cis.smu.edu (Jerry D.
Harris) writes:

<< I'm hoping someone here has this confusing situation sorted out:
 what exactly is the deal with "Altispinax" vs. _Becklespinax_?  Is the
 latter a formally named and described taxon and, if so, what's the
 reference?  I know that _Altispinax_ is a nomen dubium, based on the
 holotype tooth and the vertebrae were referred.  I understand that the
 verts of _Becklespinax_ are what Owen originally put into "Megalosaurus"
 dunkeri, but are these also the verts that were stuck into _Altispinax_?
 And who separated them out and designated the name _Becklespinax_ and
 where? >>

I'm the culprit. I published the new name _Becklespinax_ in the first
printing of _Mesozoic Meanderings_ #2 to distinguish the very diagnostic set
of three dorsal vertebrae from the holotype tooth of _Megalosaurus dunkeri_,
which is the type species of the genus _Altispinax_. Here is a slightly
edited account from the forthcoming third edition of _MM_ #2, along with a
corresponding account for the theropod _Valdoraptor_ (sorry--the italics and
such don't come out in e-mail unless you're an AOL subscriber):

Becklespinax Olshevsky, 1991b
Huene (1923) coined the genus Altispinax for two species of Megalosaurus from
the Wealden of Great Britain. The older species, Megalosaurus dunkeri, had
originally been established by Dames (1884) for a single unusual carnosaurian
tooth from Hanover, Germany. The other species, Megalosaurus oweni, had been
established by Lydekker (1889a) for a partial left metatarsus (British Museum
[Natural History] R2559) originally described by Owen (1857) as belonging to
the nodosaurid Hylaeosaurus. Huene based his name on an articulated series of
three dorsal vertebrae (BMNH R1828) with greatly elongate neural spines that
Lydekker (1888b) had catalogued, along with almost all other Wealden theropod
material, in the species Megalosaurus dunkeri. Altispinax was created as a
conditional name, without a type species, in case it could someday be shown
that R1828 was referable to the species Megalosaurus dunkeri. This, however,
is now impossible.
In two forthcoming papers (Olshevsky, in preparation a,b), I will disentangle
the confusion that has arisen concerning the names Altispinax, Megalosaurus
dunkeri, and Megalosaurus oweni in the years since they were coined. Most of
the confusion stems from misidentified type and referred specimens, and some
stems from outright errors in figures and figure captions that have
propagated through the literature in uncritical reviews. Before I can publish
the papers, however, I must travel to London to examine the specimens
personally, to photograph and measure them for comparative study. This has so
far proved beyond my means. Based on photographs kindly supplied by Stephen
Pickering, Eric Buffetaut, and Jean Le Loeuff, however, I am convinced that
BMNH R1828 and R2559 cannot possibly belong to the genus Megalosaurus and
represent two different genera of Wealden theropods.
The tooth species Megalosaurus dunkeri, through one of those unfortunate
mishaps alluded to above, can no longer be separated from the genus
Altispinax; it was made its lectotype species by Kuhn (1939). The type tooth
(for which I have no specimen number, and which may, according to Pickering,
have been lost from the University of Marburg collection) is unusual in
having no serrations on the mesial carina. Dames regarded this as significant
enough to erect a new species of Megalosaurus, but Lydekker considered this
simply the result of wear. But Lydekker undertook the unwarranted step of
referring almost all the British Museum Wealden theropod material to Dames's
species, instead of isolating the species and perhaps creating new taxa of
his own.
In particular, Lydekker referred the three vertebrae, BMNH R1828, to
Megalosaurus dunkeri. This specimen had been discovered by noted amateur
fossil collector Samuel Husband Beckles, Esq., in the Hastings Beds of East
Sussex, probably at the Black Horse Quarry (Benton & Spencer, 1995), sometime
in the early 1850s. Owen (1855: T. XIX) figured the vertebrae at life size,
and in a subsequent work (1856, oddly not the work in which the specimen was
figured) described them as anterior dorsal vertebrae of Megalosaurus. There
is little question that Owen already had the specimen in hand when he
supervised the construction of the dinosaur models for the Crystal Palace.
The "humpbacked" appearance of the Crystal Palace Megalosaurus is certainly
based on R1828's elongate neural spines. Indeed, the Crystal Palace
Megalosaurus might well be relabeled Becklespinax(!).
To discuss all the nomenclatural problems that those specimens have inspired
is beyond the scope of this work. In the case of R1828, it is enough to note
that the vertebrae are posterior dorsals, probably #8–10, and that except for
the very tall neural spines, they most closely match dorsals #8–10 of the
Argentine theropod Piatnitzkysaurus Bonaparte, 1986a) in the conformation of
the apophyses and laminae and in the craniocaudal positioning of the neural
spine atop the neural arch. The firm contact between the apices of the neural
spines of vertebrae #9 and 10 (and, presumably, later vertebrae in the
series) is a diagnostic feature of the specimen that occurs in no other known
theropod genus. It is possible (though unlikely) that the neural spine of
vertebra #8 is not simply broken off at the top but is naturally shorter than
the spine of #9. (Owen [1856] regarded the spine as unbroken.) This would
constitute another strong autapomorphy of the genus, but it requires physical
examination of the specimen to be confirmed. The neural spines are very
different from those of Acrocanthosaurus and Spinosaurus. Relative to the
lengths of the centra, the neural spines of R1828 are the tallest known in
Theropoda except for Spinosaurus aegyptiacus. I can find little justification
for referring R1828 to the genus Acrocanthosaurus as the type specimen of the
species Acrocanthosaurus altispinax (Paul, 1988b). In view of the resemblance
of R1828 to figured vertebrae of the sinraptorid Piatnitzkysaurus, I removed
the species Acrocanthosaurus altispinax from the genus Acrocanthosaurus into
a new sinraptorid [formerly eustreptospondylid] genus named Becklespinax,
honoring Beckles, discoverer of the type specimen. The type species of the
genus thus became Becklespinax altispinax (Paul, 1988b).

Valdoraptor Olshevsky, 1991b
 Having referred most of the Wealden theropod specimens to Megalosaurus
dunkeri (Lydekker, 1888b), Lydekker subsequently (1889a) redescribed, as a
new species, Megalosaurus oweni, the theropod metatarsus (BMNH R2559) that
Owen had originally referred to Hylaeosaurus (with the incorrect number
R2556). Hulke (1881) had earlier noted the theropod nature of the metatarsus,
but he did not refer it to any of the known theropod genera because his paper
was concerned with armored dinosaurs. Unfortunately, Lydekker seems to have
been misled by Owen's (1857) lithograph of the metatarsus, which presented a
mirror image of the actual specimen, and his numbering of the individual
bones (Owen deliberately [?mis]numbered the innermost metatarsal as IV and
the outermost as II): Lydekker misdescribed the left metatarsus as a right,
and shortly thereafter (Lydekker, 1890a) he referred two more metatarsals
(BMNH R604d and R1525) to Megalosaurus dunkeri, because to him they were
similar to—though not identical with—the metatarsals of Megalosaurus oweni.
Although they had been found about 180 yards apart in the Hollington Quarry,
Lydekker regarded them as belonging to the same individual! It was not long
afterward that Lydekker (1890b) removed the British Museum Wealden theropod
specimens from the species Megalosaurus dunkeri and referred them to his own
species.
Huene, in a series of papers on saurischians (1926a,b; 1932), misrepresented
the type specimen of Megalosaurus oweni as four metatarsals. This error
remained uncorrected in subsequent literature, surfacing in Steel, 1970, and
even as recently as Molnar, 1990, both of which considered the two referred
metatarsals (R604d and R1525) as cotype specimens of Megalosaurus oweni and
overlooked the real type specimen, the left metatarsus R2559.
I haven't the space here to provide all the details of those
misidentifications, and I refer the reader to the second of my forthcoming
papers on this subject (Olshevsky, in preparation b) for a more complete
study. Suffice it to say that the type metatarsus of Megalosaurus oweni is
more slenderly built and has a proportionately larger and more robust
metatarsal III than a metatarsus referred to Megalosaurus bucklandii (Molnar,
Kurzanov & Dong, 1990: Figure 6.29K). I therefore removed the species
Megalosaurus oweni from the genus Megalosaurus and made it the type species
of the new genus Valdoraptor ("Wealden robber"). The type metatarsus, BMNH
R2559, shows no sign of a proximally pinched metatarsal III, so I have
tentatively referred Valdoraptor to Allosauridae, pending completion of my
forthcoming paper. The proximal ends of the metatarsals are worn away, so it
is difficult to ascertain their configuration from the illustrative material
available to me. The type species of the genus became Valdoraptor oweni
(Lydekker, 1889).