TABLE IV

STRATIGRAPHY

SOUTH AFRICA ZAMBIAEAST AFRICA

T Upper (Cave Sandstone

R (Red Beds

I

A

Kiddle (Molteno Red MarieManda Formation

S

Lower (Cynognathus zone N'tawere Formation

S

T

(Lystrosaurue zone?Escarpment Grite ?Kingori Sandetonc.

ci

DISCUSSION

iriefly reviewing the four other species of 1nrotosaurus in

which the tabular has grown laterally towards the squamosal, it

is found that in P. aemiclnusus (Swinton, 192?), the tabular is

unexpanded dictally and only just fails to meet the squamosal.

The orbits are more roundeu and the jugal is excluded from the

orbital margin. Although the tabular horn of P. birdi (Brown,

1933) and P. peabodyi (Welles and Cosgriff, 196b) have moved

laterally, they still do not expand dietally. Also, P. peabodyi

haG a much shallower occiput and Howie (1969) has pointed out

that the vertebrae of P. peabodyi differ from those of ?. pronus.

P. birdi has a greater exposure of exoccipital on the palate than

F. pronue and the orbits are further opart in P. birdi.

1 . brookvnlcr, sis (Watson, 1958) has a distal expansion of

the tabular, but this is a bulbous swelling, which increases the

surface arta rather than causing it to approach the squamosal.

Howie (19^9)| has discounted the proposal that 1 . brookvaxeneis

is a juvenile of P. pronus, because of the character of its

ornament and the length of the snout, which are both adult in

proportion.In the type specimen of i arotoBriuruG pronus (Howie, 1969)*

the tabular is expanded laterally towards the squamosal, al­

though this expansion is greater in the type specimen of I_.

pronus. th.n in Specimen B, the significance lies not in the

absolute size (Welles and Cosgriff, 1965), but in the distinct

shape of the tabular horn, which in Specimen B is just about the

only region not distorted or damaged, and corresponds to that

rep'on in the typo species, '.he difference in. size of

- 5» -

distal expansion of the tabular and the whole skull could be

due to genetic variability >n populations.

The height to breadth ratio (H:B x 100) is 2} in the type

specimen and 17.2 and 17»^ in Specimen A and B respectively.

This difference is largely due to post-mortem deformation which

also included dorso-ventrnl flattening, which is discussed more

fully below.

The fact that in Specimen B the nares and or'oits are not

quite parallel to the skull border as they are i/i Specimen A

and the type specimen is almost certainly due to post-mortem

lateral compression.

Specimen B corresponds exactly to the type species with re­

gard to the skull breadth index (B:L is 75)* However, Specimen

A has a greater skull breadtn index (8l). This is due, mostly,

to the great difficulty in joining the small fragments in that

area; small gaps remain between abutting fragments, which added

together, caused this difference (see fig. 1 and M a t o !>•

In the type species the snout breadth index (S:Ly is 3>*-.

For Specimen A this value is hO, and Specimen k2. There seems

no doubt that even taking into consideration the lack of the

ano i Specimen A and the distortion of tnet area in S ecinen

B, Luangwa Valley animals have broader snouts ..’nan the type

species, which may be due to their larger size compared wi .h the

type.I have the opportunity of studying the almost complete

skulls from the Ruhuhu Valley, now in the Cambridge Kuseum, and

confirmed the triangular nature of their 6-ape. Vi'h ro^o.d to

Specimen B, the great expansion of the preorbital region makes

the shape of the skull almost oval (without,of c o u r s e , considering

- bt -I

the quadrate region). This could maan that with better

material, new facts may emerge to cast doubt on the taxonomy

and Specimen B could be a new species. With the available

material this latter conclusion would presume too r\»ch.

With regard to Specimen A, however, the total 1-ck of the

snout and the difficulty involved in iitting the fragments to­

gether, explain the difference in the snout index. As the in­

dices were obtained from direct measurement, not taking into

account the many small gaps, the morphological details, of the

braincase for example, convince me that Specimen A is

parotossurus pronus.

Jiowie (I969, p. 215)* dcscribce a pre-articular fossa in

the type spioies, which has not been described in other

labyrinthodonts end is not found in Sj. .cimen A, (see figs. 16A

and 16B). This foGsa is described as follows: "The (hamate)

process is transversely thickened and is excavated medially by

the leading edge of a pre-articular fossa". Howie then goes

on to explain that in the other labyrinthodonts which have a

hamate procees, this fossa is filled by a more anterior

ossification of Meckel’s Cartilage than eeen in I;. pronus. As

ossification of cartilage ic also ontogenetic, I venture to

suggest that Specimen A, was older at death than the type

specimen, causing ossification of the cartilage in this fossa.

lhe opening of the capitosaur jaw has traditionally pre­

sented a puzzle which former writers solved variously, the rrost

acceptable being the resting of the lower jaw on the substratum

together with the raising of the skull roof (aatson, 19^8) by

the depressor mandibulae muscle, which inserted on the c

1- 50 -

poi.it of the skull roof.

There are only two muscle systems which support the lower

jaw, the adductor muscles (which close the jaw) and the depressor

muscles which would open the jaw - if the lower jew was not grounded.

Howie (19&9) has reviewed the problem, and in freeing the

lower jaw of its obligation to hit the suostr&tum, has employed

the action of three muscle systems; the occipito-vertebral

muscles (which insert on the more or less vertical ccuiput and

run to the cervical vertebrae); the cleidomastoideus muscle

(which originates on the dorsal process of the clavicle and in­

serts on a projecting flange of the tatu?_ur) and the depressor

muscle, which inserted along the cheek region of the occiput on

the squamcsal and quadratojugal - so that origin and insertion

of the muscle are in the same vertical plane - the point of

attachment on the lower jaw being the slight medial inturning

of the retroarticular process.

Howie's solution has tvo phases; firstly the skull is

raised using the occipito-ve tebral muscles and then ti<e

cleidompstoideuB musclc-t r.d secondly the jaw is lowered by

the action of the deprcs. or muscles.I suggest another simpler mechanic’ • There is no Houbt

the capitosaurs were aquatic (tha lateral line system and ret?

vasculosum found in cap.tosaurs are habitus characters of

aquatic animals). If they did venture on land their progress

would have been ponderously slow, leaving little doubt that they

had little need to open their mouths on land witn a view to

catching prey. The position of their eyes (on the top of their

heads and also centrally t»l difficult to believe

they could see, stalk, lie in wait and therefore catch a meal

on land.

So, assuming the animals fed in water, on fish, which they

could see, the animal must have been totally bouyant. The

rodern animal with en analogous way of life is the crocodile.

On observation of these animals in glass tanks, it is clear the;

pt no line is the jaw firmly closed. Whether resting, swimming

or just walking on the bottom, there is a small gap between the

jews. This allows water to be continuously in t,he mouth, thus

equalizing the pressures inside and outside the mouth, then

when it wants to enap open the mouth less resistance is applied

by the water acting against e partial vacuum in the mouth, thus

decreasing the force required to oper the mouth.

A second interesting point emerged while observing croco­

diles; whenever they r.nap at prey the jaw first opens a distance

away from the prey and then the animal lurches forward. This

means that the inrush of water completes the wiaening of the

gap without great muscular exertion.

The opening oi" the capitosaur jaw by lowering of the jaw

instead of raising the skull roof, would also enable the animal

to keep sight of its prey.Assuming that capirosaurs preyed in a similar fashion to

the crocodile, if there was a depressor mandibular muscle

originating on the tabular horn flange and inserting on the

roughened area of the retroarticular process, («»jt.son, l. -fi),

this would mean when the muscle was contracted, iorce would

be exerted which resolved into vectors would have a vertical and

horizontal component, tlie latter of which wculd tend to move the

jaw rami medially (see fig. 26). This lf.tter fcrce is adequately

counteracted by the screw-shaped quadrate condyle, the thread

of which rune from pos.ero-lateral to ante*o-medial directions.

A lower jaw rotating about this condyle must move laterally.

The vertical component of the force, is possibly all the force

necessary to open the jnw in the conditions I have described

with the animal floating neutrally bouyant.

Thus, to summerise, I have employed only one mu&cle system

SUMMARY

I have dcacribed capitosaur material collected from the

fossiliferous beds of the N'tawore Formation in the Upper Luangvu Valley, Zambia.

I have assigned the Capitosaur material to the genus ard

species Parotor.aurus pronus on the basis of the va6t

similarity in proportions as well as other details (Spec: len

A), and the diagnostic otic notch, in which the tabular has

expanded laterally towards the squamosal (Specimen B).

he only other iarotosaurus pronus from another locality,

described to date, is that described by Howie (1969)1 which

was collected from Kkongoleko, Kuhuhu Valley, Tanzania, in

the Manda Fornction.

Combining points 1, 2, and 3t I have corroborated evidence

put forward by bixcy (i°37). Crompton (1955), Crompton and

Ellenberger (19^7) and Drysdall and Kiichmg (1969), that the

N'tawere Formation in the Upper Luangva Valley .ad the Manda

represent the sane horizon.

I have considered faunal units of the relevent horizons and

on the assumption that the foregoing is correct, conclude

that the *Hed Mari' horir.on of the N'tawer*. it' large.y

equivalent to that of the Mkongcleko area of the Manda

Formation and that both of these nost-dat ■ the Cyr.ognathus

zone only slightly. The lower of t>e two N'tawere

horizons may in fact, be of the saac age as thn Cynognathus

6. Assuming sapitosaurs had a similar life-style to the modern

crocodile, and the animals were neutrally bouyant, I have

suggested that only the depressor itandiouae muscleB were

necessary to open the mouth, by levering the lower ,4ew.

- rJ -

ACKNOWLEDGEMENTS

I a* deeply grateful to Dr. A . R... Cruickshank for his con­

stant help and advice as supervisor of the programme, which was

originally submitted for the degree of M.Sc.

Thanks are alto due to Mr. C. Gow for general assistance,

Mr. Patrick Nagel for his brilliunt photography, Mr. Eric Chernir

for technical assistance, and Mr. K„ Isernhinke for hid help in

biophysics.

The research was aided by a Senior bursary from Wxtwatersrand

University, and a C.S.I.R. post-graduate bursary.

- lj8 - REFERENCES

BRINK, A.S.

BROWN, B.,

CEAR1G, A.J

CHEHK1N, S.

CRU1CKSHANK

COX, C.B.,

COX, L.R.,

1963 Tvo cynodonts from the N'tawere

formation in the Luangwa Valley of

Northern Rhodesia. Palaeont. afr..

s, rt - 96.

-933 A new genus of etegocephala from the

Triaesic of Arizona. Am. Mus. Novi'...

6**0. 1 - k.

., .’i.963 Stratif raphical notenclature in the

Sonpea series of Tanganyika. Rec.

geol. Surv. Tanranyika. 10, J*7.

AND A capitosaurid amphibian from tiae

1 A.P..I., 1970 Upper Luangwa Valley, Zambia. I. U . G . .

2nd International ;̂,s:r»osium on

G( ncivann Stratirr:;phy and i alaeo-

lo<*y Cap~ Town ind Johannesburg,

1970. S.H. Haughton. Ed. C.S.I.R.

Pretoria.

1967 Changes in terrestrial vertebrate faunas

during the Mesozoic. Ini Harland,

W.B. et al. edo. The Fossil Record,

London (Geological Society), 77 - 89.

1969 Two new d.icynodonts from the Triaseic

N 1tawere Formation, Zambia. Bui)- Br.

Kws. nat. Hist. (Gcol.) Lond., ,

No. 6, 257 - 293.1932 Lcmellibranchia from the* Karroo Bede

of the Ruhuhw coalfields, TanganyiKa

Territory. ?./uart. «■■. geol. Soc. Lone’.

88, 623 - ^33.

CROMPTON, A.W

CROMFTON, A.V

e l l e n b e r g e r ,

CRUiCKiHANK,

D1XEY, F.,

r-<YSDAI.L, A.

KITCHINO, J.

I'lNDLAY, G.H

•, 1955 On some Triassic Cynodcnte from

Tanganyika, lroc. zool. Soc. Lond.,

125, 617 - 669.

. AND 1957 On a new Cynodont from the Molteno

P. Beds .. i the origin of the

Tritylodontids. Ann. S. >lfr. Hue.,

1 - Ik.

A.R.I., 1965 On a spe^’cen of Kannemeyeria

latifrons (Broom) from the Manda

Formation of Tanzania (Tanganyika).

Proc. Linn. Soc. I.oml., , 1 ^ 9 -

157.1967 A new dicynodont. gpnis from the Manda

Formation of Tanzania (Tanganyika).

J. Zool., 1 5?. l63 - 2o8*1937 The geology of part of the upper

Luangwa valley, north-eastern

Rho.13f..io. vuart. J . geol. Soc. Lond. ,

£5, -'7 - 93R. AND 1963 A re-e .-u nation of thy "‘irroo

succession and foasil localities of

part of the upper Luangwa Valley.

Men, real. Surv. Pep. N. K>iod.,

Lusaka, ^ - 62.

1968 On the structure ->f the skin mUranoC'?ntrodon (P'inesuchus)

senekalensiE 3oepen. Pal^eont.

N •

- -

FR/iAS, £., 1889

HOWIE, A.A., I969

JA5K£L, c., 1922

HEYER, H. VON, 1858

NILSSON, ?., 19^6

ROMER, A.S. 19^7

SAVE-SODERBERGH, G., 1936

SCHRODER, H.C.. 1913

STOCKLEY, G.M., 1932

kie Latyrinthondten der Schwabischen

Trias. 1alaeontopr.. 60, 275 - 295.

A new Capi.tosaurid Labyrinthodont

frcm East Africa. Palaeontology.

l;, 210 - ,' 53.

Neues ubor Hemispondyla. Ialaeont.

_Z., J?, 1 - 25»

Labyrinthodonten aus dem ounten

Sandstein von Bernburg. 1 alaeontopr.

b 221 - 2^5.

Oi. ;ce genus leltostepa Wiman and

the classification uf the Triassic

stegocephaliuns. K. Svenska

Vetensk. Akad. h’andl., No. 3 - 55»

Review of the Labyrinthodonts. bull.

Hus. como. <-iol. Harv., 22* ^ “ 352.

On the morphology of Triassi. -

Stegocephalians from i;p:.t-bergen,

a-'d the interpretation c,f the

endocranium in the Lebyrinthociontia.

K. Stre’iska Veter<t.<« Akad. Haiidj..,

1 - 181.Ein Stegocephalen-Schadel von

Helgoland. Jb. preusr,. geol.

Lardesarst. Berp; Akad. ,

232 - 264.The geology of the Ruhuhu Coalfields,

Tanganyika Territory, ^unrt. J. ££1:1 •

S oc. Lord. , 881 610 - t>22.

SVINTON, U.E. 1927

TURNER, B.R., 1972

WA'.'SON, D.M.S. 1958

1962

WELLES, o.P. AND 1965

COSGRIFF, J.,

4 new species of Capitosaurus froa

the Trias of the Blick Forest. Arm.

Mag. not. Hi-,t.. 20, 178 - 186.

Revising of the stratigraphic poBitior

of cynodonts from the upper part of

the Karroo (Gondwana) Syjtem in

Lesotho. G.ol1. Map;., 109, (in press).

A new labyri thodont (Peracycloto-

Baurus) from the Upper Trias of New

South Wales. Dull. Brit. Hus. nat.

Hist,_(Geol.) Lend., 233 - 263*

The evolution o£ the labyrinthodonts.

Phil, Trons. R. £oc. Bt 219 - 265.

A revision c “ the labyrinthodont

family Capitosa’iridae. Univ. Calif.

Pubic. Bull ♦ Pep. Geol., 51*» 1 ~ li(8.

- 6i -

LIST py ABBREVIATIONS USTP IN VIGU3ES

a - angular fma - anterior Meckelian

ae - auxiliary articulatory foramenarea fmp - posterior Meckeliaa

at - anterior commissure foramen

apv - anterior palatine fogl - glenoid fossa

vacuity fpsym - postsymphysial foramen

art - articular ic - intercoronoid

bac - baeioccipital ini - infraorbital canal

chamber ins - intercostal sulcus

bas - basal process iv - interpterygoid vacuity

bcr - basioccipital crest j - jugal

c - coronoid j' - jugalar foramen

ch - choana jl - jugal canal

CB - crista rsuscularis la - xacrimal

con - condyle lam - lamellar process

cp - cultriform rocess ClX - maxilla

crb - conical rt-ess for n - nasal

the basipterygoid nr - nare

process obr - oblique ridge

d - dentary P - parietal

dor - dorsal process paf - paraqucdrate foramen

ec - eciopterygoid pafn - parietal foramen

eo - exoccipital pal - palatine

epi - epipterygoid par - paroccipital process

f - frontal pare _ parapterygoid crest

fad - adductor fosf. . pc - precoronoid

fcnt - chorda tympani foramen pea - internal opening of

fa - foremen magnum palatine branch of the

3- 6# -

pea

P*

pmx

por

pos

PPppt

pra

pi'tif

prf

prh

prprc

prptc

P8

pt

ptf

q

qc

qj

qpt

rae

.ontinued

internal carotid

s-rtery

postfrontal

prcraaxilla

poeiorbital

postsplenial

postparietal

palatine ramus of

pterygoid

prearticular

preisa) illary foramen

prefiontal

hamate process of

prearticular

preconJylar process

poetcondylar procese

- pararphenoid

- pterygoid

- post-temporal fossa

- quadrate

- screw-shaped quadra e

ccndy)e

- Qua^-r itojugal

- q \edrate ramus of

pteri ̂ oid

- roughened area for the

attachment of the

epipterygoid

rfo - ridge marking fenestra

oval is in the dorsal

groove of the pterygoid

rp - retroartioular process

s.» - surangular

sacc - sulcus accessoriuB

sf - tub temporal fenestra

str.and - sulcus mandibularis

eoral - sulcus oralis

sp - splenial

sq - squamosal

st - stapes

stp - suprateraporal

sul - €»upraorbital canal

eym - symphysis

t - tabular

tl - temporal c.nal

tr - trough for depressor

mandibular muscle

v - vomer

ven - ventral process

KEY TO LINE I>I AGHAMS

. 61 -

Solid line - Vi'.sibj.e outline or suture in

Broken line - Reconstructed outline or suture.

estimated correct position.

Double line of hooks - Visible lateral line canal ii.

estimated correct position.

Single line of hooks - Reconstructed lateral line canal.

Heavy regular stipple - Vacuity or foramen.

Light regular stipple - Hollow or depression.

Parallel lines - W o m broken cur face.

- 4 -

Dorsal viow of Specimen A, showing superfi-ial sculpture.

Reconstruction and analysis of the dorsal view of

Specimen A.

Reconstruction of lateral viev. of Specimen k.

Reconstruction and analysis of palatal view of skull

of Specimen A.

Reconstruction and analysis of occipital view of

Speciraer- A.

Palatal view of vomer and cultriform process of

Speoim-n A.

Posterior view of braincase of Specimen A, also showing

posterior view of left exoccipitel.

Posterior view of postero-lateral area of skull of

Specimen A.

Ventral view of occipital region of Specimen A.

A) Median view of lett exoccipi.tal of Specimen A.

B ) Lateral view of left exoccijital of Specimen A.

C) Anterior view of left exoccipital of Specimen A.

Anterior view of quadrate region of Specimen A.

Dorsul view of br&incase of Specimen A.

A) Lower jaw ef Specimen A, seea lingually. (Reversed

from left side)

B) Reconstruction and analysis of lower jaw of

Specimei A, seen lingually.

A) Lingual view of anterior end of lower jaw ramus of

Specimen A. (Reversed from left)

B) Reconstruction and analysis of lingual view ox

anterior end of lower jpw ramus of Specimen A.

LIST OF ILLUSTRATIONS

It.

17.

18.

IS.

20.

21.

22.

23.

2**.

25.

26.

PLATE

PI.ATF. 1

15. A ) Posterior view of left lower jaw of Specimen A .

13) Analysis of posterior view oi' left lower jaw of

Specimen A.

A ) Postero-dorsal view of left lower ramus of

Specimen A.

B ) Analysis of postero-dorsal view of left lower

ramus of Specimen A.

Lateral view of posterior end of left lower ramus

of Specimen A, showing lateral line complex.

Lingual view of posterior end of left lower rnnue

of Specimen A to show hamate process.

Dorcal view of Specimen P.

Reconstruction and analysis of dorsal view of s k uII

of Specimen B.

ItccoT.tjtruction pnd analyr- J of laterel view of 6kuJ i

of Specimen B.

Reconstruction and analysis o r posterior view o. skull

of Specimen B.

Dorsrl view of otic notch of Specimen E, showing

superficial sculpture.

Ventral view of occipital region of Specimen B.

Posterior view of occipital view of Specimen ”.

Semi-diagramatic representation of a b-.'̂ gested

mechanism -por opening the mouth in Copitosf.urs, if

the Tniruali> are neutrally bouyo'i .

Dorsal view of skull roof c'i Specimen A.

Dorjal view of skull roof of Specimen H.

FIG .1.

F IG .3.

■MmwStasffrsige

J\Q £ M &

Author Chernin Sharon

Name of thesis Capitosaurid amphibians from the upper Luangwa Valley, Zambia.

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