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ANNALS OF THE SOUTH AFRICAN MUSEUM

ANNALE VAN DIE SUID-AFRIKAANSE MUSEUM

Volume 72 ~ # 2Band

November 1976 November

Part 3 Deel

NOTEOSUCHUS—THE OLDEST

KNOWN RHYNCHOSAUR

ROBERG te CARROLL

Cape Town Kaapstad

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NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR

ROBERT L. CARROLL

Redpath Museum, McGill University, Montreal, Canada

(With 12 figures)

LMS accepted 5 May 1976]

ABSTRACT

Noteosuchus colletti, known from a single specimen from the base of the Lystrosaurus zone

in South Africa, is the oldest known rhynchosaur. The postcranial skeleton closely resembles

that of Mesosuchus and Howesia. The tarsal elements resemble those of later rhynchosaurs

and demonstrate that the bones identified as intermedium and tibiale by Haughton, Von Huene

and Hughes are homologous with the astragalus and centrale of other primitive reptiles. The

tarsus of Noteosuchus is nearly identical to that of the primitive archosaur Proterosuchus, but

this may not be indicative of close relationship. It is probable that the rhynchosaurs had a

long period of evolution prior to their appearance in the Lower Triassic. Early Triassic rhyncho-

saurs show no significant similarities with primitive squamates.

CONTENTS

PAGE

Introduction : : ; : ; d ; 37

Noteosuchus—a forgotten rhynchosaur 5 38

Description

Material and methods : ; : : 39

Vertebrae and ribs. : 3 ; A 42

Forelimb . : 4 5 : ; : 43

Pelvic girdle and rear limb f : 4 47

Discussion . : : : : : ! : Sy

Acknowledgements. ; 3 ; : 3 56

References . 3 é : : ; : : 56

INTRODUCTION

The late Permian and early Triassic mark a time of major radiation among

diapsid reptiles, comparable with that which took place among placental

mammals in the late Cretaceous and early Tertiary, although far less well

documented. All three living diapsid orders—Crocodilia, Squamata and Rhyn-

chocephalia—are known by the end of the Triassic, and the thecodont ancestors

of the crocodiles and ancestral lizards are known from the late Permian.

Rhynchocephalians are reported from the Cynognathus zone, in the upper

portion of the Lower Triassic. The modern family Sphenodontidae is represented

only by one or two jaws, but the presumably closely related rhynchosaurs are

known from several nearly complete skeletons.

It is generally accepted that the Permo-Triassic eosuchians represent a

primitive stage in evolution, antecedent to the modern diapsid orders, although

Romer (1966, 1971) has maintained that archosaurs had a separate origin from

more primitive reptiles.

Although archosaurian features have been cited in the eosuchian genus

Ann, S. Afr. Mus. 72 (3), 1976: 37-57, 12 figs.

38 ANNALS OF THE SOUTH AFRICAN MUSEUM

Heleosaurus (Carroll 1976a), and the earliest lizards retain many eosuchian

features (Carroll 1975), the specific relationships between these advanced groups

and their eosuchian predecessors have not been established. The well-known

rhynchosaurs from the Cynognathus zone, Mesosuchus and Howesia (Broom

1906; Haughton 1921, 1924a) are also clearly distinct from the primitive

eosuchian pattern in their specialized dentition and foot structure. Determination

of the specific ancestry of rhynchosaurs requires the knowledge of earlier, more

primitive members of this group.

NOTEOSUCHUS—A FORGOTTEN RHYNCHOSAUR

The oldest known form attributed to the rhynchosaurs was described by

Watson (1912) and Broom (1925). It is from Grassy Ridge, Cape Province, at

the very base of the Lystrosaurus zone (J. Kitching, pers. comm.)—the lowermost

Fig. 1. Noteosuchus colletti, type, Albany Museum 3591; ventral view; x0,5.

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 39

Triassic. Watson originally designated the single known specimen (Albany

Museum, Grahamstown, 3591) as Eosuchus colletti, in analogy with Mesosuchus.

Broom subsequently recognized that this name was preoccupied, and so termed

the genus Noteosuchus. It is clear from Broom’s (1914) original definition of the

Order Eosuchia that it was based on Youngina, and that Watson’s genus had

no relevance to the group. Despite these early descriptions and the clear indica-

tion that Noteosuchus was a rhynchosaur, most if not all recent references (Romer

1956, 1966; Kuhn 1969) list Noteosuchus as an eosuchian rather than a rhyncho-

saur. Although some doubt might be cast on the inclusion of this specimen among

the Rhynchosauridae sensu strictu, it is certainly not an eosuchian, if the pattern

of Youngina can be taken as representative of this group.

Identity of this specimen as a rhynchosaur is subject to question because of

the absence of the skull. Comparison with specimens of Howesia and Mesosuchus

in the South African Museum reveals no significant differences in the postcranial

skeleton. Howesia and Mesosuchus are currently being studied by M. E. Malan,

who published a preliminary report in 1963. Her work will provide a much more

complete understanding of the skeleton of these early rhynchosaurs. Despite the

general similarity of these forms to Noteosuchus, it seems valuable to publish a

complete description of this genus, since it 1s by far the oldest known rhyncho-

saur. The excellent preservation provides a strong basis for evaluating the pattern

in early rhynchosaurs and for comparison when possible antecedent forms are

discovered. Modern techniques of preparation and casting enable a much more

thorough description than was possible for Watson or Broom.

DESCRIPTION

MATERIAL AND METHODS

The type of Noteosuchus colletti is preserved in a roughly circular block of

waterworn limestone, termed a ‘nodule’ by early describers. The block was

broken into three large pieces, one ventral and two dorsal, divided along the line

of the neural spines. Small fragments at the junction of the blocks are now

missing. The posterior portion of the skeleton is present, including portions of

both hands, eleven trunk vertebrae, the pelvic girdle and rear limbs, and much

of the tail, curled around the front of the block (Figs 1-5). Broom suggested that

the break at the front of the block was still fresh, and indicated the necessity for

hunting further for the anterior portion of the skeleton. Sixty years later such a

search would still be worth while.

Very little effort was made to prepare the specimen by either Watson or

Broom, aside from splitting the blocks. Nearly all the exposed bones were split

in approximately equal parts so that only an occasional trace of original bone

surface was visible. It might have been possible to glue the blocks together and

prepare away the matrix, either mechanically or with acetic acid. Because the

matrix was exceedingly hard and the bone comparatively soft, it was decided

rather to remove the bone mechanically. This resulted in the exposure of

40 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 2. Noteosuchus, dorsal view of right side; vertebrae are drawn in lateral view, although

they are preserved in their natural orientation; 1.

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 4]

Fig. 3. Noteosuchus. A. Right ulna, carpals and tail, printed in approximately their natural

relationship to the remainder of the skeleton illustrated on the facing page; <1. B. Left ulna,

drawn from counterpart block; «1. C.-G. Carpals, drawn from ventral block except for

?radiale (tentative identification: C. ulnare; D. intermedium; E. radiale; F. centralia; G. distal

carpals 1-4); x2.H. Left ilium, drawn from ventral block; ™ 1.

42 ANNALS OF THE SOUTH AFRICAN MUSEUM

extremely high fidelity moulds of both dorsal and ventral surfaces. These were

cast with liquid latex. It is from these casts that the drawings have been made.

Although the skeleton as a whole is flattened into a single plane, the individual

bones are almost undistorted. Much greater detail has been exposed by this

method of preparation than is evident in most contemporary fossils prepared by

more orthodox methods. Where practical, casts of the dorsal and ventral surfaces

of individual bones have been joined together to form three-dimensional replicas.

VERTEBRAE AND RIBS

Eleven vertebrae are present anterior to the sacrum. They have tall rectangu-

lar spines, moderately well-developed transverse processes and non-notochordal

but shallowly amphicoelous centra. As has been noted in some other primitive

tetrapods (Vaughn 1970), there is a noticeable dimorphism of the neural spines.

The width of the spines is alternately wide and narrow throughout the sequence

preserved. The transverse processes show progressive shortening and thickening

toward the sacrum. They shift gradually from the level of the zygapophyses

toward the lower half of the centrum. The zygapophyses are nearly horizontal

and set close to the midline. In the typical younginid eosuchians Youngina and

Galesphyrus, the neural arches are wide, the neural spines short, the zygapophyses

laterally placed and the centra notochordal (Gow 1975; Carroll 19766).

The two sacral vertebrae resemble those more forward except that the sacral

ribs are fused to the transverse processes. The proximal caudal vertebrae can be

seen in the ventral block, but beyond the third this portion of the dorsal surface

has been lost. Ventrally, the first eight caudals are seen in sequence; all bear

short ribs fused to the transverse process and extending straight laterally. The

tail intersects the margin of the block at the level of the eighth caudal. A more

posterior segment of the tail can be seen at the anterior edge of one of the dorsal

blocks. Fourteen vertebrae are present, extending back toward the rear limbs.

The intervening portion of the tail presumably had wrapped around the front

of the body, but is missing from the blocks as preserved. This would suggest a

tail length of 40-50 segments. The posterior caudals are long and narrow, with

little development of the neural arch. Long narrow lateral processes are evident

in this series. No tail-break mechanism can be seen.

Small crescentic intercentra are present throughout the preserved portion

of the trunk and between the first three caudals. More posteriorly, haemal arches

are visible. There is no evidence for rib articulation on the trunk intercentra.

The distal ends of three anterior ribs are seen at the margin of the block.

The shafts are quite wide and flattened. Nearly complete ribs are visible adjacent

to all the preserved trunk and sacral vertebrae. The articulating surfaces are

rarely well exposed, but they appear to have two heads, fairly widely spaced, as

in more primitive reptiles. The shafts are long and widely oval, rather than round.

There are two pairs of sacral ribs, both fused to the vertebrae. The more anterior

has the articulating surface only slightly expanded from the shaft. The second

appears to be bifurcate, with a large anterior articulating surface and a narrower

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 43

posterior process. This pattern is repeated in later Rhynchocephalia, and is also

evident in the early archosaur Proterosuchus (Cruickshank 1972). In the first

eight caudals there are short ribs, indistinguishably fused to the transverse

processes. The first extends posteriorly at a slight angle. The remainder are set

at right angles to the axis of the tail. Their length gradually decreases to the edge

of the block.

FORELIMB

Nothing of the pectoral girdle is visible. Unfortunately, the trunk is not

preserved far enough anteriorly to determine whether or not there may have

been a sternum (a hallmark of sphenodontids in contrast to rhynchosaurs).

Neither humerus is preserved, but portions of both left and right lower

limbs and hands are in place. What is preserved of the forelimb is much smaller

than the rear. The ulna and radius are approximately 60 per cent the length of

the tibia, and very slim. The distal! articulating surface of the radius is circular,

and oriented at right angles to the shaft. The distal end of the ulna is flattened

in the plane of the carpus. The articulating surface is in the shape of a broad arc.

From the two sides of the animal, most of the carpus and manus is repre-

sented. The carpal elements, although individually well preserved, are difficult

to identify or reconstruct in the absence of better known material of related

genera, since they are badly disarticulated.

Of the left wrist, eight carpals can be seen in either the dorsal or ventral

blocks (Fig. 3). It may be that only four of the five distal carpals are preserved

since the fifth metacarpal is not evident, although other elements of the fifth

digit are present. The right hand is much less well preserved, but one of the

carpals appears to have a different configuration than any of those evident on

the left side. It is probable that there are four or five proximal carpals. There

are Six proximal carpals, including the pisiform, in most primitive reptiles. None

of the elements preserved resembles a pisiform, nor is any bone to be seen in

the area normally occupied by the pisiform. Two of the carpals are considerably

larger than the others, have a considerable area of finished bone, and are deeply

notched on one margin. Comparison with other primitive reptiles suggests that

these may be ulnare, intermedium or lateral centrale. The bone represented only

from the right wrist is also relatively large, with much finished surface; it is

roughly triangular in outline. It might be the radiale. The remaining elements

are approximately circular in outline, and have little finished bone surface. If

the pisiform is absent in the fossil or not present in the living animal, two of

the remaining elements are presumably centralia. The bones represented as distal

carpals in the restoration (Fig. 6B) are arranged according to the pattern in other

primitive reptiles, with the fourth the largest.

Apart from the loss of the fifth metacarpal, the hand is apparently repre-

sented in its entirety on the left side. The first metacarpal is only about half the

length of the second, after which the length increases only slightly in the third

and fourth. The more distal elements are just slightly shorter. The proximal

ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 4. Noteosuchus, dorsal view of left side of skeleton; x 1.

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 45

Fig. 5. Noteosuchus. A. Proximal caudal vertebrae drawn in approximately their natural

relationship to the remainder of the skeleton illustrated on facing page. B. Left femur in

dorsal, ventral, anterior, posterior, proximal and distal views. C. Left tibia in extensor, flexor,

medial, lateral, proximal and distal views. All x 1.

46 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 6. Noteosuchus. A. Left fifth metatarsal in dorsal, ventral, medial, lateral, ventrolateral,

proximal and distal views; x2. B. Right hand in dorsal view; <1. C. Left foot in dorsal

VICWisIeG Le

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 47

phalanges are all of approximately the same length, roughly that of the first

metacarpal. The unguals are long, fairly sharp, and somewhat recurved. Longi-

tudinal grooves along the ventral margin demarcate the base of a tubercle for

the attachment of the flexor tendon. Digits one, two and three definitely have a

phalangeal count of two, three, four. The fourth also appears to have only four,

although the slight displacement of the bones indicates the possibility that one

more might have originally been present. An element adjacent to the fourth

metacarpal is probably a phalanx from the fifth digit, from which another

proximal and the ungual phalanx are preserved.

PELVIC GIRDLE AND REAR LIMB

The pelvic girdle is of the primitive plate-like appearance seen in eosuchians,

other primitive rhynchosaurs and proterosuchian archosaurs. There may be a

slight down-turning of the pubis, but this is difficult to ascertain as a result of

the manner of preservation. There is certainly a prominent pubic tubercle. There

is asmall obturator foramen at the posterior margin of the pubis, but no develop-

ment of the thyroid fenestra. The pubis and ischium both meet their counterparts

ES EL 8 US

Fig. 7. Ilia of rhynchosaurs, reduced to a common size. A. Noteosuchus. B. Howesia.

C. Stenaulorhynchus. D. Paradapedon. (B.—D. from Chatterjee 1974.)

along the full length of their medial margins. The ilium closely resembles that of

Mesosuchus, in having a broad blade and narrow anterior and posterior ridges

surrounding an essentially circular acetabulum. Chatterjee (1974) has illustrated

a series of ilia from more advanced rhynchosaurs, which show progressive

anterior extension of the blade. In Noteosuchus, the anterior margin is nearly

vertical. The pubis and ischium appear to contribute equally to the acetabulum,

in contrast to the condition in Proterosuchus, in which the pubis is excluded.

Except for its smaller size, the ischium is almost identical with that of

Proterosuchus.

The bones of the rear limb (Fig. 5) resemble those of Howesia and

Mesosuchus in their length and proportions. They are much slimmer than those

of Proterosuchus. In anterior or posterior view, the femur is notably sigmoidal

in configuration, as is that of Mesosuchus. The proximal articulating surface is

a flat, nearly square area, which is continuous with an internal trochanter that

nearly doubles the thickness of the end of the bone. This structure is continuous

with the anterior surface of the femur, and tapers gradually toward the middle

48 ANNALS OF THE SOUTH AFRICAN MUSEUM

of the shaft. The intertrochanteric fossa is short without a definite distal limit.

There is no adductor crest.

The tibia is approximately 90 per cent the length of the femur. There is a

large, more or less triangular, proximal articulating surface, and no cnemial crest:

The shaft rapidly narrows to an oval cross-section, and then very gradually

thickens toward a flat, circular, distal articulating surface. The fibula is a slim,

flattened bone with a small oval articulating surface proximally and a larger,

flattened area distally. Distally, the bone is no wider than the tibia, in contrast

to that of Galesphyrus.

The feet of the only specimen of Noteosuchus are particularly well known.

Although somewhat disarticuvlated, the individual elements are perfectly

preserved, retaining their original three-dimensional configuration. There 1s little

difficulty in restoring the natural arrangement of the foot. Its elements are

figured individually and in articulation in Figures 6 and 12. The general con-

figuration is comparable to the tarsus of later rhynchosaurs recently reviewed

by Hughes (1968). Before detailed description of the feet is possible, a very serious

question of the homology of the units must be settled. Romer (1956) and

Schaeffer (1941) identify the proximal elements in the tarsus of rhynchosaurs as

astragalus, calcaneum and centrale—the elements present in the vast majority

of primitive reptiles. Hughes (1968), in his recent consideration of the rhyncho-

cephalian foot, identifies the centrale as a tibiale and the astragalus as an inter-

medium. No centrale is recognized. This identification has been followed by

Cruickshank (1972) and Chatterjee (1974).

If comparison is made with Galesphyrus or other primitive reptiles (Fig. 10),

acceptance of Hughes’s identification of the proximal elements in rhynchosaurs

indicates very significant differences. The astragalus must be assumed to revert

to a more primitive state in which the intermedium and tibiale are not co-ossified,

a condition not seen in any other reptile. Presumably, the proximal centrale, a

third bone which was incorporated into the astragalus of primitive reptiles

(Peabody 1951), remains with one or the other of the two recognized elements.

At the same time, the distal centrale is presumably lost or incorporated in some

other area of ossification.

In fact, there is a considerably easier way of looking at the changes in the

proximal series. Rather than both losing the distal centrale and breaking down

the astragalus into its primitive components, one need only enlarge the distal

centrale from the condition seen in Galesphyrus and incorporate it more closely

with support of the tibia. The element termed ‘intermedium’ by Hughes ts in

fact structurally and functionally completely comparable with the astragalus of

Galesphyrus, captorhinomorphs and other primitive reptiles. In all these forms

there are large but distinctly separate facets for articulation with the tibia and

fibula. The so-called tibiale of rhynchosaurs has the same relationship to the

astragalus and to the first three distal tarsals as has the centrale of all primitive

reptiles.

Despite their obvious homology, the relationship of the astragalus with the

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 49

calcaneum in Nofeosuchus and the shape of the calcaneum are distinctly advanced

over the pattern of eosuchians (Carroll 19765) and completely comparable to

that seen in more advanced Triassic rhynchosaurs. The astragalus has a well-

developed peg which overrides the medial end of the calcaneum, and the latter

bone has a distinct lateral tubercle. The centrale is a smaller, nearly spherical

bone with no finished surface. It is not as closely integrated with the astragalus

as it is in middle and late Triassic rhynchosaurs. Although the pattern of the

proximal tarsals can be derived from that seen in eosuchians, no known eosuchian

specifically presages this condition. There is no fifth distal tarsal. The fourth

Fig. 8. Right foot of Howesia, South African Museum 5886, in various views; fifth metatarsal

in ventral view; restoration of foot; «1,5. Abbreviations: a—astragalus; cal—calcaneum;

cen—centrale: fib—fibula; tib—tibia; 1,2, 3,4,5—distal tarsals; I, 1], 111, 1V, V—metatarsals.

50 ANNALS OF THE SOUTH AFRICAN MUSEUM

distal tarsal is a large, flat, quadrangular bone, supporting principally the

calcaneum. The second and third distal tarsals are much smaller, essentially

spherical elements. The first distal tarsal is a larger oval bone, articulating with

almost the entire proximal end of the first metatarsal.

The lateral margins of the proximal end of the first four metatarsals overlap

each other in succession. The length of the metatarsals increases steadily from

the first to the fourth. All are approximately twice as long as their counterparts

in the forelimb. The fifth metatarsal (Fig. 6) is shorter than all but the first and

exhibits all the characteristics cited by Robinson (1975) as typifying the hooked

condition in lepidosaurs. The proximal end of the shaft angles sharply medially

and presents a very large articulating surface to the fourth distal tarsal. There

is no articulating surface between the fourth and fifth metatarsals. Laterally,

the proximal end of the bone has a distinct outer process. The dorsal surface of

the shaft is evenly convex from side to side throughout its length. Ventrally, the

lateral margin is projected as a distal plantar tubercle. There appears to be a

smaller medial tubercle as well. The distal articulating surface forms a broad

arc on which the digit could rotate widely.

The proximal phalanges are all considerably shorter than their correspond-

ing metatarsals; those of the first two digits are considerably smaller than the

rest. The length of the remaining phalanges diminishes gradually. The ungual

of the first digit is seen on the right side; two on the left are probably from digits

three and four. As in other rhynchosaurs, there is apparently still the primitive

reptilian phalangeal count of 2, 3, 4, 5, 4.

Large but fairly typical reptilian ventral scales can be seen among the ribs.

M. E. Malan, who is currently studying the rhynchosaurs from the

Cynognathus zone—Howesia and Mesosuchus—kindly gave the author permis-

sion to prepare and illustrate the feet of these forms (Figs 8-9). They show a

striking similarity to the feet of Noteosuchus. Except for the definite identification

of a first distal tarsal and elimination of the possibility of a separate medial

centrale beneath the astragalus, little modification of the reconstruction of

Howesia given by Broom (1906) is required. Additional preparation has shown

that most of the elements are larger than he had estimated; consequently, all

the bones are more closely fitting. The relatively small size of the centrale and

its separation from the astragalus reflect the more primitive condition of this

genus in comparison with the Middle Triassic forms described by Hughes.

Mesosuchus is slightly closer to the pattern of the later forms. Hughes has

admitted some difficulty in interpreting the drawing of Mesosuchus provided by

Haughton (1921, plate 3 (fig. 6)). Further preparation of this specimen (Fig. 9B)

demonstrates an anatomy very similar to that of Howesia. The element identified

as intermedium is actually the lateral portion of the astragalus; the presumed

break from the more medial area is simply the sharp change in angle at the level

of the raised articular facet for the tibia. The elements shown by Haughton and

Hughes as fused calcaneum and tibiale are clearly separable into astragalus and

centrale. Although definitely not fused, the centrale shows a more intimate

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 51

Fig. 9. Mesosuchus. A. South African Museum 7416, left and right feet. B. South African

Museum 6046, right foot. All «1,5. Abbreviations as for Figure 8.

SZ ANNALS OF THE SOUTH AFRICAN MUSEUM

association with the astragalus than is seen in Howesia. The left and right feet

of Mesosuchus are fairly well preserved in a second specimen, South African

Museum 7416 (Fig. 9A), confirming the pattern shown in the earlier described

ankle and providing additional information concerning the metatarsals and

phalanges.

Fig. 10. Tarsals of diapsids. A. Galesphyrus; 1,5. B. Noteosuchus; «1. C. Howesia; x1.

D. Stenaulorhynchus; 0,25 (from Hughes 1968). E. Paradapedon; 0,25. Astragalus is

heavily outlined, centrale is coarsely stippled. Abbreviations as for Figure 8.

DISCUSSION

Comparison of all known elements of the skeleton of Noteosuchus with those

of the slightly younger rhynchosaurs Howesia and Mesosuchus shows extremely

similar patterns. Specimens of all three genera are of nearly equal size and

degree of ossification, further emphasizing their anatomical similarity.

Despite the absence of the skull and anterior trunk region, Noteosuchus may

be included in the same family with considerable assurance. It is not possible,

however, to determine whether or not generic distinction from both younger

genera is justified.

Assignment of Noteosuchus to the Rhynchosauridae extends the known

range of the family to the very base of the Triassic. Unfortunately, Noteosuchus

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 53

provides little if any more specific information regarding the origin of the

rhynchosaurs. Eosuchians from earlier beds are either much more primitive,

e.g. Youngina (Gow 1975) and Galesphyrus (Carroll 19766), or specialized in a

totally different manner, e.g. He/eosaurus (Carroll 1976a), and the Tangasauridae

(Haughton 19246; Piveteau 1926) and Paliguanidae (Carroll 1975, 1977). One

must assume a considerably earlier separation of rhynchosaurs from the ancestral

eosuchian stock. The description of a primitive diapsid from the Upper Penn-

sylvanian (Reisz 1975) indicates that rhynchosaurs could have diverged from the

basic eosuchian stock long before their fossils are first known in the Lower

Triassic.

A further comparison of Noteosuchus and other primitive rhynchosaurs that

bears investigation was made by Cruikshank (1972). In describing the archosaur

Proterosuchus he stated (p. 116), ‘it is possible that Proterosuchus represents a

slightly modified carnivorous rhynchocephalian’. Cruickshank stressed the

similarity of the feet of these forms. This was emphasized by his acceptance of

Hughes’s terminology of the proximal units asfibulare, intermedium and tibiale.

More detailed illustrations of the feet of Proterosuchus and Noteosuchus

(Figs 11-12) show how close the resemblance is. Comparisons are particularly

striking between the astragalus and calcaneum, both of which exhibit consider-

able complexity.

The elements in Proterosuchus are approximately 50 per cent larger than

those of Noteosuchus, and there are some differences in proportions, but hardly

more than might be expected in different species within a genus or even different-

sized individuals in a single species. Functionally, they must have been nearly

identical. One difference which does appear significant is the configuration of

the facet of the astragalus that articulates with the tibia. In Proterosuchus it 1s

very broad and flat, but in Noteosuchus and also Mesosuchus and Howesia it is

narrower and distinctly convex.

In Proterosuchus and early rhynchosaurs, the centrale is a large, essentially

spherical bone, with no area of finished surface, that shares with the astragalus

support of the tibia. The fourth distal tarsal is a larger element that is notched

to receive the much smaller third distal tarsal. The second distal tarsal is much

smaller, but the first is comparable in size to the centrale. The metatarsals

(notably the hooked fifth) and the phalanges are similar in all significant respects,

although the fifth digit appears to have one more phalanx in Noteosuchus.

Despite the general similarities of the postcranial skeleton between Protero-

suchus and Noteosuchus, and the striking similarities of the tarsus, a number of

specific differences can be cited:

1. Exclusion of the pubis from the acetabulum by the ilium in Proterosuchus

but not Noteosuchus.

2. Sharp posterior angle of the iliac blade in Proterosuchus in contrast with a

rounded margin in Noteosuchus.

3. Three-part division of the posterior sacral rib in Proterosuchus, in contrast

with two parts in Noteosuchus.

54 ANNALS OF THE SOUTH AFRICAN MUSEUM

Fig. 11. A. Proterosuchus, dorsal and ventral views of the left foot; x 0,75. B. Noteosuchus,

ventral view of left foot; 1,5.

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 55

4. Proportionately heavier limb bones in Proterosuchus, corresponding to the

greater size of the adult.

It is difficult to evaluate the relative significance of the head and the post-

cranial skeleton in establishing phylogenetic relationships, although in practice

more importance is nearly always given to cranial remains. In view of the

constancy of important cranial features among both primitive thecodonts

(Ewer 1965; Cruickshank 1972; Hughes 1963) and rhynchosaurs (Malan 1963;

Chatterjee 1974), it seems probable that the similarities in foot structure in

Fig. 12. Proximal tarsals of a rhynchosaur and an archosaur. A. Proterosuchus, left calcaneum

in proximal, distal, dorsal, ventral and medial views; 0,75. B. Noteosuchus, left calcaneum

in same views; “1,5. C. Proterosuchus, left astragalus in dorsal, ventral, medial, lateral and

proximal views; *0,75. D. Noteosuchus, left astragalus in same views; 1,5.

56 ANNALS OF THE SOUTH AFRICAN MUSEUM

primitive rhynchosaurs and Proterosuchus are a result of convergence of this

particular feature, rather than being indicative of close relationship. In the

absence of knowledge of the specific ancestors for either rhynchosaurs or

Proterosuchus, this cannot, however, be stated with great confidence.

There are also a number of points of similarity between the postcranial

skeleton of Noteosuchus and that of Prolacerta, recently described by Gow

(1975). The shapes of the sacral ribs and the ilium are essentially the same, and

the femur shows a comparable twisting. However, the greater length of the tibia

and fibula, relative to the femur, provides a simple way of differentiating these

forms. The foot of Prolacerta shows a comparably hooked fifth metatarsal.

Material of both Pro/acerta and rhynchosaurs demonstrates the difficulty of

assigning late Permian and early Triassic diapsids to either the Lepidosauria or

the Archosauria, as distinguished by Romer (1956).

ACKNOWLEDGEMENTS

I wish to thank Dr T. H. Barry and Dr Michael Cluver for their hospitality

and assistance while this work was being carried out in the South African

Museum. Dr M. E. Malan, University of Stellenbosch, was extremely helpful in

allowing me to study the postcranial material of Howesia and Mesosuchus and

in discussing the cranial anatomy of these forms, on which she expects to publish

shortly. Mr C. F. Jacot-Guillermot kindly allowed me to prepare and describe

the type material of Noteosuchus from the Albany Museum, Grahamstown.

I also wish to express my appreciation to Drs A. Cruickshank and C. Gow for

their assistance in making facilities available at the Bernard Price Institute in

Johannesburg. Dr J. Kitching was extremely helpful in providing stratigraphic

data on these and other specimens from South Africa. The illustrations of

Noteosuchus were completed by Mrs Pamela Gaskill. This work was supported

by grants from the Merrill Foundation, the National Research Council of

Canada, and the Faculty of Graduate Studies and Research, McGill University.

REFERENCES

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1906: 591-600.

Broom, R. 1914. A new thecodont reptile.— Proc. zool. Soc. Lond. 1914: 1072-1077.

Broom, R. 1925. On the South African Triassic rhynchocephaloid reptile ‘Eosuchus’ colletti,

Watson.— Rec. Albany Mus. 3: 300-305.

CARROLL, R. 1975. Permo-Triassic ‘lizards’ from the Karroo. Palaeont. afr. 18: 71-87.

CARROLL, R. 1976a. Eosuchians and the origin of archosaurs. /n: CHURCHER, C. S., ed. Athlon:

Essays on Palaeontology in Honour of Loris Shano Russell. Misc. Publ. R. Ont. Mus.:

58-79.

CARROLL, R. 19766. Galesphyrus capensis, a younginid eosuchian from the Cistecephalus zone

of South Africa. Ann. S. Afr. Mus. 72: 59-68.

CARROLL, R. 1977. The origin of lizards. Jn: MiLes, R. S., ANDREWS, S. M., & WALKER, A.,

eds. Linnean Society Westoll Commemoration Volume. London: Academic Press. (In press.)

CHATTERJEE, S. 1974. A rhynchosaur from the Upper Triassic Maleri Formation of India.—

Phil. Trans. R. Soc. Lond. (B) 267: 209-261.

NOTEOSUCHUS—THE OLDEST KNOWN RHYNCHOSAUR 57

CRUICKSHANK, A. R. I. 1972. The proterosuchian thecodonts. Jn: Joysey, K. A. & Kemp, T. S.,

eds. Studies in vertebrate evolution: 89-119. Edinburgh: Oliver & Boyd.

Ewer, R. F. 1965. The anatomy of the thecodont reptile Euparkeria capensis Broom.— Phil.

Trans. R. Soc. Lond. (B) 248: 379-435.

Gow, C. E. 1975. The morphology and relationships of Youngina capensis Broom and Prolacerta

broomi Parrington.—Palaeont. afr. 18: 89-131.

HauGuton, S. H. 1921. On the reptilian genera Euparkeria Broom, and Mesosuchus Watson.

—Trans. R. Soc. S. Afr. 10: 81-88.

HauGuton, S. H. 1924a. On a skull and partial skeleton of Mesosuchus browni Watson. —

Trans. R. Soc. S. Afr. 12: 17-26.

HauGutTon, S. H. 19246. On reptilian remains from the Karroo beds of East Africa. — Quart.

J. geol. Soc. Lond. 80 (1): 1-11.

Huaues, B. 1963. The earliest archosaurian reptiles.—S. Afr. J. Sci. 59: 221-241.

Huaues, B. 1968. The tarsus of rhynchocephalian reptiles.—J. Zool. Lond. 156: 457-481.

Kuun, O. 1969. Proganosauria, Bolosauria, Placodontia, Araeoscelidia, Trilophosauria,

Weigeltisauria, Millerosauria, Rhynchocephalia, Protosauria. Handb. Paldoherp. 9: 1-74.

MaALAN, M. E. 1963. The dentitions of the South African Rhynchocephalia and their bearing

on the origin of the rhynchosaurs. S. Afr. J. Sci. 59: 214-220.

PEABODY, F. 1951. The origin of the astragalus of reptiles. Evolution 5: 339-344.

PIVETEAU, J. M. 1926. Paleontologie de Madagascar, XIII. Amphibiens et reptiles permiens.

Annls Paléont. 15: 1-128.

Reisz, R. 1975. Petrolacosaurus kansensis Lane: the earliest known diapsid reptile. Unpublished

Ph.D. thesis, McGill University, Dept. of Biology.

RoBINSON, P. 1975. The functions of the hooked fifth metatarsal in lepidosaurian reptiles. —

Colloques int. Cent. natu. Rech. scient. 218: 461-483.

Romer, A. 1956. Osteology of the reptiles. Chicago: University of Chicago Press.

Romer, A. 1966. Vertebrate paleontology. 3rd ed. Chicago: University of Chicago Press.

Romer, A. 1971. Unorthodoxies in reptilian phylogeny. — Evolution 25: 103-112.

SCHAEFFER, B. 1941. The morphological and functional evolution of the tarsus in amphibians

and reptiles.— Bull. Am. Mus. nat. Hist. 78: 395-472.

VAUGHN, P. 1970. Alternation of neural spine height in certain early Permian tetrapods. —

Bull. sth. Cal. Acad. Sci. 69: 80-86.

Watson, D. 1912. Eosuchus colletti, gen. et spec. nov.— Rec. Albany Mus, 2: 298-299,

6. SYSTEMATIC papers must conform with the International code of zoological nomenclature

(particularly Articles 22 and 51).

Names of new taxa, combinations, synonyms, etc., when used for the first time, must be

followed by the appropriate Latin (not English) abbreviation, e.g. gen. NOV., sp. nov., comb.

nov., syn. nov., etc.

An author’s name when cited must follow the name of the taxon without intervening

punctuation and not be abbreviated; if the year is added, a comma must separate author’s

name and year. The author’s name (and date, if cited) must be placed in parentheses if a

species or subspecies is transferred from its original genus. The name of a subsequent user of

a scientific name must be separated from the scientific name by a colon.

Synonymy arrangement should be according to chronology of names, i.e. all published

scientific names by which the species previously has been designated are listed in chronological

order, with all references to that name following in chronological order, e.g.:

Family Nuculanidae

Nuculana (Lembulus) bicuspidata (Gould, 1845)

Figs 14-15A

Nucula (Leda) bicuspidata Gould, 1845: 37.

Leda plicifera A. Adams, 1856: 50.

Laeda bicuspidata Hanley, 1859: 118, pl. 228 (fig. 73). Sowerby, 1871: pl. 2 (figs 8a—b).

Nucula largillierti Philippi, 1861: 87.

Leda bicuspidata: Nicklés, 1950: 163, fig. 301; 1955: 110. Barnard, 1964: 234, figs 8-9.

Note punctuation in the above example:

comma separates author’s name and year

semicolon separates more than one reference by the same author

full stop separates references by different authors

figures of plates are enclosed in parentheses to distinguish them from text-figures

dash, not comma, separates consecutive numbers

Synonymy arrangement according to chronology of bibliographic references, whereby

the year is placed in front of each entry, and the synonym repeated in full for each entry, is

not acceptable.

In describing new species, one specimen must be designated as the holotype; other speci-

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not regarded as paratypes should be listed separately. The complete data (registration number,

depository, description of specimen, locality, collector, date) of the holotype and paratypes

must be recorded, e.g.:

Holotype

SAM-A13535 in the South African Museum, Cape Town. Adult female from mid-tide region, King’s Beach,

Port Elizabeth (33.51S, 25.39E), collected by A. Smith, 15 January 1973.

Note standard form of writing South African Museum registration numbers, date and geographical positions.

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e.g. . the Figure depicting C. namacolus . . in C. namacolus (Fig. 10) .

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