Tuesday, May 24, 2011

Charig's thesis- "Mandasuchus" and "Teleocrater"

Fitting with the basal archosaur theme of this month, here's something I've been meaning to post for a while.  One of the rarest Mesozoic archosaur papers of all is Charig's (1957) unpublished thesis.  Unlike Zhao (1985), which I could at least order, no one can get a copy of Charig's work.  You're not even allowed to photocopy it without permission of the copyright holder, and Charig died in 1997.  Even if you somehow managed to get permission from his children, it'd still cost $176 to photocopy (assuming rates have stayed the same over the last decade, which they certainly haven't here).  George Olshevsky (DML, 2001), who's seen most every dinosaur paper in existence, believed "when he was alive he embargoed all the copies so that no one could obtain it."  In October 2001 John Jackson went to the Cambridge Library and made notes ("paraphrasing here and there, from fairly arbitrarily chosen sections, with bits missed out"), which he gave permission to distribute.  The previous person who accessed it did so in 1986, giving some idea of how rare it is.  As Charig's nomina nuda are well known, the publication is 54 years old, and he won't be publishing on them, I think the information is fair to share.  So without further ado, here's the closest any of us will probably get to reading Charig's thesis-


"Unfortunately the word “Nyasasaurus” does not appear in my notes.
 
The work is in two volumes: the illustrations: 53 plates, each with a facing
page of titles; and the volume of text of just over 500 pages.
 
Notes on:
Charig, A. J. 1957. New Triassic archosaurs from Tanganyika, including
Mandasuchus and Teleocrater. Dissertation Abstracts, Cambridge University.

[My comments in […] brackets.]
 
Mandasuchus longicervix, known from 3 specimens, and Teleocrater tanyura,
known from 2 specimens; in both genera, skull poor and post-cranial good.
 
General notes:
 
Both have closed acetabula.  Mandasuchus differs from Prestosuchus (from the
upper Rio do Rasto beds) in that Mandasuchus’s cervical vertebrae are
elongated (Prestosuchus’ are not, as far as is known).
 
The dermal armour differentiates the family [presumably Mandasuchus’s
family] from Stagolepidae (from the upper Tr of Laurasia).
 
There are no good grounds for considering the acetabulum of Spondylosaura[?]
to be open.  The neck of Spond. is more elongated than Mandasuchus.
 
Teleocrater has greatly elongated cervicals, unlike any other pseudosuchian
described, but closely resembling Coelophysis, yet it has a closed
acetabulum, and limbs like other pseudosuchians.
 
 
Diagnosis of Mandasuchus:
 
A pseudosuchian tending to large size.  The skull is unknown, except for
fragments of the maxilla and dentary, the former showing a large antorbital
vacuity; jaws long.  Dentition thecodont; teeth recurved, laterally somewhat
compressed, with anterior & posterior borders crenulated.
 
Vertebrae with the length of centrum never much less than the diameter and
usually greater than diameter.  Centra lightly amphicoelus; floor of neural
canal deeply concave in each centrum, except in posterior caudal region;
zygapophyses moderately oblique; tops of neural spines, especially in
anterior part of column, flattened and expanded to bear dorsal scutes.
 
Axial and caudal intercentra only.  More than 25 pre-sacral vertebrae
present.  Eight cervical vertabrae (by arbitrary definition) including
atlas; axis slightly elongated, other cervical vertebrae much elongated (up
to 50% over typical dorsals), elongation being greatest in 5th; axis and 3rd
cervical with prominent keel, faint ventromedial ridge in others; neural
spines low; axial and cervical ribs present, the later crocodiloid.
Seventeen or more dorsal vertebrae, centra mostly rounded beneath, some
slightly flattened; typical archosaurian shift in position of rib
articulation, parapophysis borne entirely on centrum in 2nd dorsal, on both
centrum and neural arch in 3rd & 4th, and on neural arch only on 5th;
diapophysis supported by oblique radiation buttress in anterior dorsals;
parapophysis and diapophysis tend to form “spectacles-shaped” rib
articulations then fuse in posterior dorsals; most if not all dorsal
vertebrae with hyposphene.  Two sacral vertebrae [in life probably].  Caudal
verts, except most anterior members, flattened ventrally and with
haemopophyses (absent in first three); distal caudals with small median
pre-neural spine between prezygapophyses, anterior to neural spine proper;
rami of proximal end of each haemopophysis joined by bridge, at least in
distal part of tail.
 
Major limb bones long and slender, with hollow shafts; propodials longer
than epipodials; bones of forelimb about two-thirds as long as hindlimb.
 
Scapula broad both dorsally and ventrally, only moderately inflected;
coracoid with small foramen; dermal elements of pectoral girdle not known.
Humerus with high deltopectoral crest, well-marked supinator process and
ectepicondylar groove, no entepicondylar foramen or groove; ulna without
olecranon; no manus.
 
Acetabulum closed.
 
Ilium with short anterior spine, long posterior spine, well-developed
supra-acetabular crest, forming most of the acetabulum; pubis long, with
small obturator foramen, twisted proximally in typical pseudosuchian manner,
distally plate-like and directed steeply downwards, thickening of lateral
corner of distal end; ischium also elongate, peduncle flattened laterally
and with sharp anteroventral edge, possibly not meeting its fellow in
mid-line but diverging from it distally, distal end slightly thickened.
 
Femur slightly sigmoidal, with prominent 4th trochanter high on shaft;
fibula with anterior muscle process; fibulare crocodyloid, pes otherwise
unknown.
 
Paramedian dorsal scutes, not corresponding in number with verts but more
numerous, keeled externally, each notched posteriorly and overlapping
anterior spine of scute behind it, without ornament.
 
 
Teleocrater:
 
First impression is a vertebral column of a saurischian type, associated
with the ilium and limb bones of a pseudosuchian.  The verts resemble a
coelurosaur very closely; long, especially anterior, cervicals, and
generally lightly constructed.  But the acetabulum certainly closed; humerus
has supinator process and ectepicondylar groove; femur has no well-defined
head set at an angle to the shaft, and is without a 4th trochanter; tibia
shorter than femur; fibula has lateral trochanter.
 
This specimen was found in a heterogeneous field-collection [but other
material easily distinguished from the Teleocrater stuff].  It seems most
unlikely that 28 verts from a saurischian, without any corresponding limb
bones, would be found together with 9 well-preserved pseudosuchian girdle
and limb bones lacking any corresponding verts, and the dimensions of the
two sets of bones being strictly comparable.
 
The genus must be referred to the pseudosuchians because of the apparently
closed acetabulum.  Neither specimen has known dermal scutes, but then the
type lacks the top of every neural spine, and the other specimen is too
incomplete.  The ilium and limb bones of Teleocrater, though typically
pseudosuchian in form, resemble no other known particularly, though not
widely different from Mandasuchus, despite great differences between the
vertebrae of the two.  On the other hand, the vertebral column *does*
resemble coelophysis.  There is a general resemblance between Teleocrater
and Coelophysis in their hollow, thin-walled bones.  Teleocrater is a little
smaller on average than Coelophysis.  In both, verts are long and slender,
especially in the neck and tail, and the centra are usually amphicoelous.
 
Von Heune’s axis [his Coelophysis one] resembles the Teleocrater vertebra in
extreme elongation and in the marked and asymmetric concavity of its ventral
profle, the apex of which lies in front of the middle of the vertebra.  It
seems that in both animals the anterior face of the centrum must have lain
more dorsally than the posterior, showing the head was held above the level
of the body.  There is further resemblance in the nature of the ventral
surface of the centrum: concave or flattened in front between a pair of
sharp edges, bearing a medial ridge in the middle part (much longer in
Coelophysis) and rounded behind.  The posterior face is roughly circular,
and fairly deeply concave in both.  The most striking similarity is between
the flange-like diapophyses and zygapophysial ridges of the two verts,
giving both a highly characteristic appearance.  The detailed arrangement of
the flanges and ridges is almost exactly the same.
..
..
..
Dorsal Vertebrae:
In both [Coelophysis and Teleocrater] still slender and rather elongate, but
a little stouter towards the sacrum.  There is also a resemblance in the
gradual change in position of [the?] parapophysi…
..
..
..
Caudal region:  There is also a general similarity here between [_T_ and
_C_].  _C_ however differs from Teleocrater in having no facets or
intervertebral spaces for haemapophyses (though Case opines chevrons would
be expected), and their ventral surfaces are rounded without traces of
longitudinal grooves or ridges.  In Teleocrater only the last 4 of the 15
caudals preserved have rounded ventral surfaces without haemapophysial
facets.  In both Teleocrater and _C_ the centra are weakly amphicoelous, the
flattened transverse processes, the bases of which are axially long in the
anterior cuadals, diminish down the series and disappear; the zygapophyses
remain, even in the smallest vert, and the anterior pair project in front of
the centrum; and the neural spines, which also diminish and disappear, have
an anterior edge rising obliquely backwards, and a posterior edge rising
almost vertically.
..
..
..
The lilum of _C_ and Teleocrater is utterly different.  In Teleocrater the
acetabulum is almost certainly closed. The anterior spine in Teleocrater is
extremely short.  The posterior spine in Teleocrater is broken off but seems
to have been long, and the beginning of a strong medial crest is preserved.
Case ’27 described an isolated ilium from Texas, similar in size to _C_
longicollis but “somewhat different in form.”  It was actually very
different, and is definitely not from _C_, but rather similar to Teleocrater
though about twice as large; any acetabular perforation must have been very
small.  Extremely long anterior spine and correspondingly long, very heavy
posterior spine, bearing a high medial crest.
 
The fumur of _C_ and Teleocrater differ mainly in the head in Teleocrater
being not at all bent towards the median side.  Teleocrater’s femur more
powerfully built but relatively even longer  (compared to _C_’s equivalent
to 5 of its dorsal verts) in Teleocrater equivalent to six or seven anterior
dorsal verts.  The shaft is sigmoidally curved and there is no ext.
trochanter.  The only similarities between femur of _C_ and Teleocrater are
the absence of a properly developed fourth trochanter, and the form of the
broadened, club-shaped distal end with its weakly developed condyles.
 
Tibia:
Not the remotest resemblance between the two animals.
 
Fibula: in _C_ “but little expanded.”  This differs from Teleocrater.
 
Summary:
_C_ and Teleocrater only similar in their vertebral columns.  This
similarity is no more than might be expected between any two coelurosaurs.
However there is a particularly close resemblance in the anterior cervicals,
with their highly elongate centra and characteristic flanges; this form is
most unusual and yet almost identical.
..
..
..
General Taxonomics:
Both Mandasuchus and Teleocrater are from the “upper bone bed” of
Tanganyika, and share a common tendency to resemble the saurischia to an
unusual extent.  This tendency, particularly in Teleocrater, is more
pronounced in the vertebral column than the girdle and limbs.  The two
genera are strikingly different: Mandasuchus (and other prestosuchids)
generally reminiscient of pachypodosaurs, Teleocrater very like
coelurosaurs.
 
[He considers the vert. column similarities between Teleocrater and
Mandasuchus enough to suggest acet. perforation occurred independently in
the two saurischian groups (and between 4-6 times overall).]
 
 
 
His thesis also deals with other archosaur bits from the Maleri beds of
India, all of which were described in Von Heune (‘40c): Palaeont. Indica
(n.s.) 32 memoir no. 1, 1-42.
 
 
From the Summary:
The only important difference between Mandasuchus and Prestosuchus is
Mandasuchus’s cervical verts are elongated while the latter’s (as far as is
known) are not.  It is proposed to erect a new family: Prestosuchidae for th
e two, the most diagnostic feature of which would be the dermal armour,
clearly distinguishing it from the Stagonolepidae." 
 
Thanks to John for this interesting look at an obscure document.

6 comments:

  1. I believe "Nyasasaurus" was n-nudumed in Appelby et al, 1967

    Appleby, R.M., Charig, A.J., Cox, C.B., Kermack, K.A. & Tarlo, L.B.H. 1967. Reptilia. Geological Society, London, Special Publications, 2: 695-731.

    jay

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  2. Your introduction seems to be missing something. What's to stop anyone else from going to the Cambridge Library and requesting to look at it?

    If you're still alive in 2067, the thesis should be public domain then.

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  3. Also, how difficult is it to view the actual fossils?

    According to Butler et al (2009), "Mandasuchus" was redescribed in an unpublished thesis by K. M. Thomas in 2005.

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  4. "What's to stop anyone else from going to the Cambridge Library and requesting to look at it?"
    "Also, how difficult is it to view the actual fossils?"

    Both would require travel to England, which I know I'm not going to be able to do anytime soon. If I did go there though, I know I'd be spending my time in collections, not reading outdated theses on taxa which will be redescribed soon by Nesbitt, Berrett, etc. anyway.

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  5. The name Nyasasaurus is now officially described ---- see Nesbitt et. al. 2012 for original description.

    As pointed out by Nesbitt et. al. in the supplementary data for their paper, "Teleocrater rhadinus" may belong to the same species as Nyasasaurus, even though they stress that the evidence for such an assignment is weak. They also refer Thecodontosaurus alophos (based on a few presacral vertebrae) to Nyasasaurus.

    Nesbitt, S. J., Barrett, P. M., Werning, S., Sidor, C. A., and A. J. Charig. 2012. The oldest dinosaur? A Middle Triassic dinosauriform from Tanzania. Biology Letters.

    ReplyDelete
    Replies
    1. Very cool indeed. Now to get "Mandasuchus tanyauchen", "Teleocrater rhadinus" and "Pallisteria angustimentum" described.

      Delete