Some Comments on *Bahariasaurus ingens* Stromer (1934)

["Jaime Headden" <ja_headden@qilong.8m.com>]

  Discussion with Mickey on this taxon prompted a critical review of what
Stromer (and virtually no other except to repeat him or add little other data)
had to say and figure of this form.

  *Bahariasaurus ingens* is represented by a partial type specimen, 1922 X 47
(Stromer, 1934:pl. 2, figs. 4, 8-10). This comprises a pair of fused pubes, the
proximal end of a right ischium above the obturator process, three sacral centra
in series, and a partial rib fragment; it was found at Gebel (hill) Gorâbi in
the northern Baharija basin. Referred specimens from the same site include a
proximal scapula and very fragmentary coracoid (1912 VIII 60), several pubes
(1922 X 48B, 1912 VIII 81, 1922 VIII 62), ischia (1922 XII 23, 1922 VIII 74), a
femur (1912 VIII 69, which Stromer felt was tentative), a fibula (1912 VIII 70,
same as for the femur), partial cervical (1922 X 48A, including portion of fused
centrum and neural arch),  "mid-series" (Stromer, 1934:74, "mittlerer") distal
caudal (1912 VIII 83A), caudal "thoracic" dorsal (1922 X 48D), sacral neural
arch (1912 VIII 62E), to sacrals (1912 VIII 62D, F), a proximal caudal vertebra
(1912 VIII 62B), and two sacral vertebrae, one of which is a centrum (1912 VIII
60D, G, same as for the femur). Stromer (1934) identified an element as a pair
of pubes (pl. 2, fig. 2) but these have a prominent obturator projection, and
compare well to the ischia of *Elaphrosaurus,* otherwise the material was
treated as gen. et sp. indet. As stated by Sereno et al., 1994, he believes that
the coracoid (but not scapula), pubes, right femur, proximal right tibia, and
left fibula, pertain to *Deltadromeus*, all from the specimens prefixing with
1912 VIII, but this refers to date and site, rather than specimen proximity; the
scapula and coracoid of 1912 VIII 60 are the same specimen, as an example. The
proximal tibia in question, 1912 VIII 78, was referred to aff. *Erectopus
sauvagei*, but compares in general to *Deltadromeus* in some, but not all
details. These details are significant, however, as they serve to differentiate
the material. Sereno et al. identify the type of *B. ingens* as being more
extensively composed than Stromer indicates (pg. 991, note 32), including
material Stromer indicated at 1922 X 48, though this specimen also comprises an
additional set of pubes 75% the size of the holotypic pubes.

  Comparative data is achievable between the type materials of the two taxa
through the distal pubes and proximal ischium. Problematically, Stromer did not
illustrate the type pubes in lateral view, merely in caudal view. A referred
pubis, that of a "juvenile" 1912 VIII 81, bears comparative boot morphology,
though the shaft of the pubes are sigmoid, whereas in *Deltadromeus* they are
straight in profile. The distal pubes in *Deltadromeus* are strongly constricted
distally, forming a very narrow and shallow pubic apron and bear not foramen
between them or between the distal ends of the boot, as in *B. ingens.* In fact,
only one pair of pubes from the sites compares to this in general, and that is
in fact 1912 VIII 81 in which they are strongly constricted distally, although
they bear a large foramen in the above the booth, and the apron is 75% of the
pubic length, unlike in *Deltadromeus*. The previously identified
*Elaphrosaurus* ischia bear similarities to the pubes in lacking any foramina
and their strong distal constriction, but the conjoined ischiadic apron is much
too extensive to relate.

  The proximal ischia are distinctly incomparable, as the proximal ends of it in
both taxa are far too incomplete to illustrate details.

  The femora compared show similar morphology of the distal end and of the
anterior trochanter, which is large and aliform or wing-like. The femoral shaft
in *Deltadromeus* is illustrated as having a slight curvature, whereas that of
1912 VIII 69 has a far more distinct curvature, though likely this is based on
size differences, and is arcuate, whereas *Deltadromeus* has a slightly sigmoid
femur in profile. The femoral head in *Deltadromeus* appears to be oriented
medially, given the figures in Sereno et al., which is how they coded this taxon
(as
in Coelurosauria); the femur of 1912 VIII 69 has a craniomedially-oriented head,
as in ceratosaurs and carnosaurs. The lesser trochanter of the two differs in
both position and size, where in the Egyptian femur, it is small and situated
below the proximal 1/3 of the femur; in *Deltadromeus*, the lesser trochanter is
large and in the proximal 1/3.

  The proximal tibia of  1912 VIII 78 does indeed bear superficial similarities
to *Deltadromeus*, however this is only in profile and in general when seeing it
from the proximal surface end-on; a channel runs along the Egyptian tibia front
to back between the rear condyles and lateral to the cnemial crest, but not in
*Deltadromeus*, and the lateral cnemial crest is very sharply angled in dorsal
view, as is the lateral femoral condyle, whereas these are far rounder and
blunter in *Deltadromeus.*

  The fibulae compare very well, and in fact, except for apparent broader
expansion of the proximal end compared to *Deltadromeus*, and the less
well-defined margins for the medial fibular fossa, which also expand closer to
the edges of the proximal end in 1912 VIII 70, these are identical, and Sereno
et al. would not be amiss in referring them to *Deltadromeus.* Since the type of
*Bahariasaurus* does not include the fibula, this does not affect their relative
synonymy or the nature of the diagnostic status of the latter.

  Stromer remarked on an astragalus ("talus") from Gebel el Dist that is similar
to that of *Deltadromeus*, referring to it as "gen. et sp. indet." (pg. 56; pl.
3, fig. 7) This possesses a large calcaneal facet that is vertical and not
concave, contra *Deltadromeus*, with a horizontal groove across the anterior
face; the ascending process is broken, but is not wide, and did not expand to
the lateral or medial margin of the main body of the bone, as in *Deltadromeus*
and non-coelurosaurs.

  Another "gen. et sp. indet." remarked on is a metatarsal (1912 VIII 177),
likely the second based on its tear-drop shaped proximal end (Stromer, 1934:pl.
3, fig. 17; pp.52-55). This bone compares in length:width and shape to
*Deltadromeus* superficially, though the distal end is not ginglymoid, and does
not form a semi-condyle but is nearly flat in anterior view. Otherwise, this
bone resembles that of *Deltadromeus* strongly.

  The coracoid and scapula (1912 VIII 60) are, for all intends and purposes,
identical to *Deltadromeus*, as far as their partial preservation permits
comparisons, save some small details of profile differences: the coracoid
possess a more concave margin between the glenoid and tip of the caudoventral
process; the scapula proximal end is deeper towards the glenoid than in
*Deltadromeus.* It is not possible to tell how much larger or smaller the
complete scapulo-coracoid was to *Deltadromeus.*

  A caudal dorsal centrum referred to *Bahariasaurus*, 1922 X 48, cannot be
compared to the cranial dorsal neural arches in *Deltadromeus*, and the two are
otherwise quite distinct, with the Egyptian taxon lacking the extensive
infradiapophyseal lamina seen in *Deltadromeus*, but this is expected in
theropods where laminae are progressively reduced in the dorsal series. An
anterior dorsal centrum with partial neural arch is preserved, 1912 VIII 60D

 Compared vertebrae can only include the caudals, and both taxa have caudals as
part of their hypodigm. Both have distal caudals that are procoelous with a
caudally flat face; however, the distal caudal 1912 VIII 83A preserves
transverse processes on the neural arch, rather than on the centrum, as in
*Deltadromeus*, and the postzygapophyses project further caudally and dorsally
than in the latter. Other caudal vertebrae include what Stromer identified as
sacrals (pp.28-29; 1912 VIII 62D, F, pl.2, fig. 25-26), and are identified as
caudals because of the shallow transverse processes and their presence above
the centrum, rather than part of it, and by the lack of any indication of
sutures; these vertebrae are spool-shaped, amphicoelous, and bear prominent
pleurocoels in the upper central, surrounded by a fossa; as the material was
found apart from the type at Gebel Maisâra, this association is tentative at
best, and the material otherwise compares to descriptions of caudal vertebrae of
*Acrocanthosaurus*, leading me to suspect they belong to *Carcharodontosaurus*.
(I would also point out other caudal vertebrae that Stromer described include
smaller centra with large pleurocoels surrounded by fossae, possibly distal
carcharodontosaurid caudals [or something more spectacular, a therizinosaur?],
that has implications for the identification of a similar caudal-based taxon,
*Inosaurus*, also from Africa ... so, not a therizinosaur, but possibly a
carcharodontosaur?)

  A third vertebra, a mid-series caudal identified as a proximal one (pp.27;
1912 VIII 62B, pl.2, fig.24), represents a more distinct morphology, having a
long centrum over 2x as long as high caudally, with a broad-based and deep
transverse process, hyposphene-hypantrum articulation, strongly arched centrum
ventral
margin when viewed in profile, and a long, slit-like pleurocoel at the
centrum/neural arch suture; the centrum is also proceolous with a flat caudal
face, and implies that it does, in fact, represent the same taxon as 1912 VIII
83A. The neural spine is not preserved in any caudal, so the distinct features
of *Deltadromeus* caudals cannot be adequately compared. This does, however,
imply that a similar caudal morphology in *Bahariasaurus*, if in fact these
specimens pertain to the same as the Gebel Gorâbi material (type; referred).

  So are they the same?

  No. There is little comparative data between the type and the material assumed
to pertain to it, even forbidding Stromer's tentative assignments. However, if
one assumes that the type and referred material DO pertain to a single taxon,
this form does possess some distinct features from that of *Deltadromeus*,
including the distal pubic morphology, that shows they are separate taxa.
Features of the referred material (caudal morphology, fibular fossa) indicate
the presence of *Deltadromeus* or a very closely related taxon exists at
Baharija. The proximal caudal 1912 VIII 62B also bears features in common with
*Elaphrosaurus*, including strongly arched centrum and proximal face inclined
ventrally when the caudal face is vertical. The pectoral girdle almost certainly
pertains to a taxon close to *Deltadromeus*, and these in turn are nearly
identical aside from their absence of fusion to *Carnotaurus* and *Aucasaurus.*
Other ceratosaur features include the very small, degenerate(?) lateral cnemial
crest of the tibia, metatarsals II and IV narrower than III, distal chevron do
not fork cranially to form skid-like processes, a very large medial fibular
fossa that expands to fill the proximal end. The femur does not decline from
the greater trochanter, nor does it bear a medial crest on the distal end, as in
abelisaurs, though the fourth trochanter is large and proximal in position with
a semi-lunate profile.

  Tetanuran features of *Deltadromeus* (based on Holtz, 2000) include:
  341.1, distal femoral extensor groove shallow and just barely conspicuous;
  352.1, tibia backs distal end of fibula and calcaneum;
  362.1, astragalar ascending process mediolaterally reduced, and apparently low
(based on the distal tibia).
ACCTRAN optimization provided: 334.1, anterior trochanter divided from greater
by deep cleft;
  360.1, fibula distal end less than twice the width of the mid-shaft, with
reduced dorsal fossa on astragalus/calcaneum/tibia for articulation of the
distal end;
  364.1, astragalar distal ends oriented craniocaudally.
DELTRAN optimization provided: 338.2, no trochanteric shelf;
  350.1, crista tibiofibularis not well-developed.

  Tetanuran features of *Bahariasaurus* include:
  305.1, pubic peduncle of ilium longer craniocaudally than it is wide (based on
the proximal pubis);
  341.1, distal femoral extensor groove shallow and just barely conspicuous;
  352.1, tibia backs distal end of fibula and calcaneum;
  362.1, astragalar ascending process mediolaterally reduced.
ACCTRAN optimization provided: 334.1, anterior trochanter divided from greater
by deep cleft;
  360.1, fibula distal end less than twice the width of the mid-shaft, with
reduced dorsal fossa on astragalus/calcaneum/tibia for articulation of the
distal end;
  364.1, astragalar distal ends oriented craniocaudally.
DELTRAN optimization provided: 338.2, no trochanteric shelf.

  So they would appear to be, by some extent, relatively close, basal
tetanurans, perhaps abelisaurs convergent upon tetanurans, or a moderate taxon;
some features used to diagnose Tetanurae (Holtz, 2000) occur in abelisaurids, as
well, including expansion of tibia to back calcaneum and fibula, mediolateral
width of astragalus ascending process reduced, distal condyles of astragalus
orient craniaventrally. Though it seems likely they are not ceratosaurs, these
shared features appear to place them between "Ceratosauria" and Coelurosauria,
to be safer than sorrier, with convergent qualities of both, resulting in Sereno
et al. (1996) finding a basal coelurosaur position for *Deltadromeus.*

References:

Holtz, T.H., Jr. 2000 [marked as 1998]. A new phylogeny of the carnivorous
  dinosaurs. _GAIA_ 15: 5-61.

Sereno, P.C.; Dutheil, D.B.; Iarochene, M.; Larsson, H.C.E.; Lyon, G.H.;
  Magwene, P.M.; Sidor, C.A.; Varricchio, D.J.; and Wilson, J.A. 1996. Predatory
  dinosaurs from the Sahara and Late Cretaceous faunal differentiation.
_Science_
  272: 986-991.

Stromer, E. von. 1934. Ergebnisse der Forschungsreisen Prof. E. Stromers in den
  Wüsten Ägytpens. II. Wirbeltierreste der Baharîje-Stufe (unterstes Cenoman).
13.
  Dinosauria. [.] _Abhandlungen der Bayerischen Akademie der Wissenschaten_
  (neue folge.) 22: 1-79, pls. I-III.



  Cheers,

  Jaime A. Headden

  Little steps are often the hardest to take. We are too used to making leaps in
the face of adversity, that a simple skip is so hard to do.  We should all learn
to walk soft, walk small, see the world around us rather than zoom by it.

  "Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)