Ana səhifə

Review of the reptilia of the triassic

Yüklə 309.5 Kb.
ölçüsü309.5 Kb.
1   2   3   4   5   6   7   8   9   10

The primitive structure of the shoulder girdle in Pareiasaurus is also stegocephalian-like. It can be compared particularly well with the Permian temnospondylous Eryops. In Pareiasaurus this consists of episternum, clavicle, cleithrum, scapula, coracoid, and procoracoid. The Triassic Mastodonsaurus is also very similar. The intercentrum of the vertebrae, the more or less deeply amphicoelous articular surfaces of thc centra, whose bodies and the thick, mostly single-headed ribs are characteristics that mutatis mutandis very much recall many Permian and Triassic Stegocephalia. In Pareiasaurus the centra are even perforated by a nerve cord as in Eryops. The noteworthy distal expansion of the posterior dorsal ribs of Cynosuchus recalls a similar feature of the ribs of Archegosaurus. Also the long, distally expanded sacral ribs and the narrow ilium with expansion at the acetabular and upper end is just as in Dicynodon, Mastodonsaurus, Eryops, Chelonia and Proganosauria. The ilium of several other Anomodontia, like Cynosuchus, Pareiasaurus, etc. likewise recall this type, although the upper end of the ilium is rather broader by the large number of sacral vertebrae. The ilium of Nothosauria and Placodontia is also similar. Several Nothosauria certainly have a short, thick ilium that recalls Pareiasaurus bombidens more.

The femur and tibia of Pareiasaurus also have great similarity with temnospondylous Stegocephalia like Eryops and Actinodon. In the femur both have in common the huge, plate-like development of the greater trochanter that projects far over the tiny femoral head which is little more than a small wart; Deuterosaurus and Rhopalodon are the same. The backward, deeply bilobed proximal articular surface of the tibia of Pareiasaurus and Eryops is strikingly similar.

In most Anomodontia the ischium is larger than the pubis. Frequently both are fused almost completely, and both participate in the formation of the close acetabulum. The obturator foramen is most obvious.

Placodontia claim a particular interest since they are brought into a clearer light now by a find of skeletal bones and dermal armor described by Prof. O. JAEKEL (1). For a long time SEELEY has connected them with Anomodontia, and specifically with Deuterosauridae from the skull proportions. The new find from the Raibl Beds of Vesprum on the Plattensee has now aroused all possible interest as we gather from JAEKEL’s preliminary description. The entire back (in Placochelys) is armored, the armor consists of small polygonal plates with elevated midpoints, between which are scattered larger and higher plates. Psephoderma alpinum, P. anglicum, and Psephosaurus suevicus are therefore, as I see it, no more than the dorsal armor of Placodontia. Further, it emerges with certainty from the seldom-preserved cervical and dorsal vertebrae that Tanystrophaeus has nothing to do with Placodontia, as has been suggested already. The ribs have a triangular cross-section with a flat side above. Abdominal ribs are present. Further an almost circular pubis is present. Most skeletal bones of this new find are similar to Nothosaurus to such an extent that, if found isolated, they would have been assigned, in our hitherto inadequate knowledge, without thought to Nothosauria (2).

The skull of Placochelys has decorations like Miolania on the occiput. The skulls of Placodus and Cyamodus, known for a long time (which I learned about in Bayreuth, Munich, and London), seem to me to indicate without doubt close connection with certain Anomodontia. It was the occiput in particular that gave me this idea. The basioccipital with the two lobe-shaped downward processes, to which the extraordinarily short basisphenoid is connected, is as in Rhopalodon and Dicynodon. The internal border of the foramen magnum is formed by the exoccipitals which extend far horizontally toward the side and nearly reach the quadrate; they participate in the formation of the condyle. In Rhopalodon it is almost exactly the same. The exoccipitals of Dicynodon are much broader. The supraoccipital of Placodus is small and roof-shaped, in Rhopalodon broad and extended horizontally, in Dicynodon broad and high. Rhopalodon possesses a large interparietal, which still inserts a little between the parietals, exactly as in Placodus, only it reaches the upper surface of the skull roof; the parietals begin only near the middle of the temporal fossa. The interparietal is also present in Dicynodon. In these genera the squamosals also participate in the dorsal wall of the skull. The opisthotics are not separated by a suture. The pterygoids, whose posterior wings are turned over high upward, are likewise visible with a large surface posteriorly in Placodus and this is not the case in Dicynodon. Thus in the formation of the occiput there is perfect agreement between Placodus and Rhopalodon. The skull roof and sides may also be compared. Both genera have very small frontals and parietals and huge prefrontals in common. But the palate of Placodus, Rhopalodon, and Dicynodon is entirely different. The vomer does not generally occur in Placodus; palatine, maxilla and premaxilla, which are all provided with the well-known large pavement or incisor teeth, have a considerable extent. The pterygoid and ectopterygoid recede almost entirely. But this difference may be explained by the special development and function of the teeth. Only an unpaired inner nasal opening is present, which is bordered by palatine, maxilla and premaxilla. As in all Anomodontia only a single temporal fossa is present. From what has been said I think it is obvious that Placodontia are members of Anomodontia. SEELEY even viewed them directly as a subdivision of Deuterosauria. The pavement dentition and dorsal armor, otherwise unknown in Anomodontia, are no grounds against this view, for they connect directly with the way of life and give Placodontia the stamp of highly specialized forms; indeed the tooth loss indicates senility of the premaxilla (probably covered with a horny beak) in Placochelys. It is probably likely that Placodontia is related to Deuterosaurus and Rhopalodon, but the differences not only in the skull but also in the skeleton are, however, again so large that this is not positively certain. Nevertheless I can find nothing in the skeleton that contradicts such a direct relationship. In any case Placodontia is very much adapted to water or coastal living, which is already indicated by the dentition. If JAEKEL held Placodontia for the ancestors of Chelonia, I cannot agree with him. Against it is firstly the structure of the palate, then the presence of the interparietal and perhaps also that of the abdominal ribs. Also the geological occurrence deserves sufficient assessment. Chelyzoon from the Muschelkalk and Proganochelys from the Upper Keuper are the oldest Chelonia, but Placodontia are found from the Lower Muschelkalk (of Upper Silesia (1)) to the Rhaetic (Schönthal, Upper Bavaria, Lombardy, Somerset); thus fully developed Chelonia (cryptodire and pleurodire, see below) already appear long before the extinction of Placodontia, indeed even nearly contemporaneous with them. I hold Placodontia for an aberrant branch of land-living Anomodontia (perhaps Deuterosauridae) adapted to water life which became extinct at the end of the Triassic. The similarity of the limbs of Placodus and Nothosaurus seems to me to arise from the fact that Nothosauridae also arises from Anomodontia, even if from elsewhere (see below) and have also adopted to water life, only to a much greater extent and by other means.

Placodontia, which is distributed over nearly the entire European Triassic, also seems to have a representative in South Africa in the small Eunotosaurus africanus SEELEY. SEELEY compares it with Mesosaurus (2); certainly the thick ribs recall it, however they are strongly expanded on the dorsal side. But in particular the extraordinarily elongated dorsal vertebrae make close relationship with Sauropterygia impossible. The long vertebrae with low spinous process (see Fig. 20, dorsal side, the two most anterior vertebrae), the low cross-section of the centra in comparison to the thick ribs which first bend wing-like upward (see Fig. 20, dorsal side, 6th vertebra from front) to above the spinous process and then curve downward in the sides with a broad, smooth dorsal surface, recall Placodus very much as I have figured it on Pl. V, fig. 1 and 2. The pubis (see Fig. 20, ventral side) corresponds entirely with that of Placochelys which Prof. JAEKEL showed me in Berlin. Despite the lack of skull and limbs it is very likely that Eunotosaurus is a South African placodont.

Anomodontia must have been an extraordinarily plastic order, for its characteristic features embrace so many different animal forms, many very generalized, others highly specialized. They give the impression of uniting Stegocephalia and highly organized Reptilia more directly and promptly than occurs in other (genetic) lines. The Anomodontia cut off, as one might say, a detour. FÜRBRINGER expresses himself very aptly when he says that high specialization is built up on a very primitive base within Anomodontia.

Firstly, under the names Trochanterium and Eurycervix, remains will be described that could be placed in Stegocephalia rather than Anomodontia.


(Name referring to high greater trochanter) Pl. VI, Fig. 2.

H. von MEYER in his “Fauna der Vorwelt,” Pl. 65, fig. 8, figured a bone not clear at the time. It comes from the Upper Muschelkalk of Bischmisheim near Saarbrücken. Now that similar ones have been described by OWEN, SEELEY, and GAUDRY, we can easily get onto the right track.

It is a small but very massively built right femur. The greater trochanter is developed thickly fan-shaped and rises far above the femoral head, which projects upward in direct continuation of the diaphysis as a small spine, so that a small pit remains between it and the root of the greater trochanter. On the lateral side the greater trochanter is thicker than on the median; the whole fan curves a little outward. The diaphysis is short and very thick; it is thicker on the median side than the lateral; three edges arise from this, the two median ones are straight, the lateral curved strongly outward. The distal end is again thickened and bears the two condyles, of which the median one projects more strongly and further than the lateral. Thus the end seems obliquely cut off.

The construction of the femur indicates a stocky animal with relatively short limbs. The distal end in particular shows that tibia and fibula must have stood far apart, which again requires a very muscular lower leg.

Similar femora are frequently present, in Pareiasaurus, Deuterosaurus (“Dinosaurus”), Rhopalodon, Eryops, Actinodon, etc. But only in these is found a related group (Temnospondyli, Pareiasauridae, Deuterosauridae) which also has many other things in common. In the former view, the similarity with Actinodon and Pareiasaurus is greatest. The formation of the femoral head is perhaps most similar to Deuterosaurus, but here as in the others named the greater trochanter is much higher and narrower and the femoral head is still insignificant and moved more toward the side. The femur of Actinodon is unfortunately not known from the posterior side, however it is not so broad and strongly built as in Trochanterium. For a deuterosaurid the latter is again too stocky. In Pareiasaurus and Eryops the condyles are formed entirely differently; thus it cannot have belonged to any of them. It agrees best with built; but whether it was a true temnospondyl naturally cannot be decided with certainty. It is also possible that it is a transitional form between Stegocephalia and Pareiasauridae. This is one of the few remains of land reptiles from the German Muschelkalk.

In GAUDRY’s honor, Trochanterium may bear his name, which the knowledge of Actinodon has made so highly deserved.

eurycervix postumus n. gen., n. sp.

Pl. IX, Fig. 2.

In the collection of the honorable BLEZINGER of Crailsheim are found several very noteworthy ribs. They come from the Upper Muschelkalk bonebed of the Oelmühle, near Crailsheim. There are two rather complete specimens and four fragments. The form is very noteworthy; it recalls broad, double-bladed paddles, strongly constricted in the middle, at the same time thickened toward one side; both ends expanded flat and turned a little toward each other. The expanded part has a thickened and a thin edge; the thick edge lies on one side diagonally opposite to that of the other end; therefore also the thickening in the constricted middle runs rather obliquely to the longitudinal axis. Proximal and distal ends are difficult to distinguish. The Geological Collection at Breslau possesses a piece of a similar, almost equally large cervical rib; it comes from the Dadocrinus horizon of the Lower Muschelkalk of Gogolin, Upper Silesia.

The smaller Discosaurus from the Plauen Valley near Dresden (1) has almost exactly similar cervical ribs, but similar ones also in Melanerpeton, Brachiosaurus, Sclerocephalus; further Archegosaurus, Actinodon, etc. Also the dorsal ribs of Cynosuchus have a certain similarity.

The agreement of these cervical ribs with those of the named temnospondylous Stegocephalia is so striking that there is no doubt that we also have here remains of a gigantic ancestor of the group. The whole animal must have been 2.5-3 m long, if one takes into consideration the proportions of the ribs at hand to those of the 1 m long Sclerocephalus.

It is not impossible that that form of the tibia belongs to the same genus which is found fairly frequently in the Schaumkalk of Freiburg am Unstrut and occasionally also in the Lettenkohle of Hoheneck. It is characterized by a high, straight, and strongly marked crest. The distal end

shows two articular facets meeting roof-like. The proximal end, seen from above, is long, broader backward and divided in two. The shaft is considerably narrower in the middle than at the ends. I figure here (Pl. V, fig. 1) a particularly fine example from the Upper Muschelkalk of Steinbiedersdorf, Lorraine, which belongs to the Strassburg Collection; a sketch should illustrate a piece from the Schaumkalk of Freiburg am Unstrut in the Halle Collection.

The similarity with the tibia of Sclerocephalus labyrinthicus CREDN. is striking. Despite small differences in the individuals, the overall structure is exactly the same (1).

Since both the cervical ribs and the tibia recall Sclerocephalus, it is suggested that they belong to the same or a very similar genus.

Here I also rank a fibula from the Schaumkalk of Freiburg am Unstrut, which, from its entire structure, agrees very well with the described type of the tibia. Probably it belongs to the same genus.

From the Schaumkalk of the Middle Muschelkalk of Freiburg am Unstrut there is in the Geological Collection at Halle am Saale a strange bone that, at first glance, resembles an ulna, but must rahther be a femur.

A few sketches of the bone may suffice to give an idea of its structure. I refrain from a detailed description. It is important to me in general to show what kind of interesting things occur in the Muschelkalk.

In the interpreation of the bone as a femur, the plate-like forward-reaching part must be the greater trochanter and the ascending triangular part the femoral head. The upper leg of Trochanterium is indeed almost built on a similar principle. In the Freiburg piece both condyles are very strong at the distal end.

The structure of the bone seems to me to indicate the order Anomodontia (cf. about this, the statements on Trochanterium), more cannot be said in advance, for the find is completely isolated.


1857 FISCHER, Über Scl. armatus H. v. M. N. Jahrb. f. Min. etc., p. 136-140, pl. 3 and 1 text-fig.

1859 H. v. MEYER. Palaeontographica VII, 35-40, pl. 6.
= Labyrinthodon rütimeyeri WIEDERSHEIM.

1878 WIEDERSHEIM, Labyrinthodon rütimeyeri, Ein Beitrag zur Anatomie von Gesammtskelet und Gehirn der triadischen Labyrinthodonten. Abh. Schweiz. pal. Ges. Bd. 5.

= Aristodesmus rütimeyeri (WIEDERSHEIM sp.) SEELEY

1895 SEELEY, On an anomodont reptile from the Bunter Sandstone near Basel. Proc. Roy. Soc. 59, 167-169.

1900 SEELEY, Aristodesmus rütimeyeri (WIEDERSHEIM). Quart. Jour. 56, 620-645.
Pl. I-III and IV, fig. 5.
The two valuable slabs of stone from the Main Bunter Sandstone of Riehen near Basel that bear the impression of' the well-known fossil (1), which were lately described in detail by SEELEY (loc. cit.) and placed in the correct light, were recently very kindly sent to me from the Museum at Basel. WIEDERSHEIM had described the animal only from the negative, in the course of which several quite disturbing errors crept in. SEELEY made casts of separate parts and was thus in a position to judge the systematic position correctly. When I was fortunate enough to see the rubber casts in Prof. SEELEY’s house last summer, I decided at once to attempt a complete cast, if permitted. This permission was granted with great kindness in January 1902 for which I thank most sincerely the Museum Commission at Basel and especially Dr. STEHLIN.

The cast was made by TH. TRAA of Stuttgart, the very skilled plaster cast maker, in the Geological Institute, Tübingen. Since the work was some of the most difficult of its kind, it will be in order to say a few works on the technical execution. Firstly the sandstone was hardened with ether copal resin and then coated with white shellac (which could be remoced with alcohol. He used as a casting medium a mixture in approximately equal parts by volume of “brown hare lime” (of Paris (1)) and glycerine. This mixture has a strong enough bond and is nevertheless so soft and plastic that there is no risk of breaking some of the brittle sandstone. Also the deepest hollows could be molded using it; but where he broke the gelatine he later made a special cast in which was previously fixed an unravelled cord that he attached carefully with a heated knife. The greatest difficulty was converting the gelatine positive into one of plaster, since a gelatine mold was impossible because of the hot molding. Thus a negative of (red-colored) plaster had to be made and (white) plaster poured into it. Now the positive was in plaster but could not be withdrawn like the first plaster form and the red negative had to be dissected carefully using a needle, which took many days. This form was hardened with linseed oil and reproduced by the well-kown methods (2).

The casts produced by this method not only give an idea of the habitus of the complete skeleton, which could already be recognized with care from the negative (originally) but they have also produced some real surorises. Above all, the skull has a bizarre appearance because of the huge skull spines which are similar to those of Elginia and the North Russian Pareiasauria.

The purpose of these lines is not entirely to replace SEELEY’s excellent description by a new one but mainly to indicate the further important discoveries made possibe for the first time by the complete casts.

Of the skull, the lower jaw is preserved complete; also present are the inner surface of the skull roof, the right maxilla, the two posterior angles of the skull and parts of the ccciput. That originally the complete skull roof was present in the block of stone is to be gathered regrettably from the following words by WIEDERSHEIM (loc. cit.): “When the slab of stone first came into my hands, there was visible on one of the slabs, PL. I, only the roof of the oral cavity or, more exactly, only the dorsal half of the cast of the oral cavity, once full of sand. But soon I noticed, by examination with very flexible probes, that I could reach from different openings into one enlarged cavity that extended along the entire dorsal surface of the mass of stone, interpreted by me earlier as a skull. I did not hesitate to take chisel and hammer in my hand and not rest until the entire upper surface was freed from the stone core. Yet I did not conceal from myself the fact that by this procedure possible fossils of the skull bones in the covering mass of stone, which I was reducing to chips by hammer blows, must have disappeared along with the matrix. Thus I can say nothing of their possible existence, only a repeated examination of the chipped fragments showed me that the bones, if they had left behind fossils, bore no sculpture of the kind borne by most labyrinthodont skulls but must have been perfectly flat…In the middle of the posterior region, 1.5 cm from the occipital edge, one sees a round, bud-shaped elevation. It was originally much longer than it appears in the figure, for we have before us the only point by which the upper surface of the internal cast was suspended by a well-shaped small colunn surrounded by the casing of stone. There can be no doubt that we have here the place where sediment intruded into the parietal foramen from above and later hardened; it was blocked by it and I could conclude, from the original height of the stone plug before it fell under the chisel, the huge thickness of the parietal in the immediate surroundings of the parietal foramen.” It is much to be regretted that such an effort was made with this valuable object in the endeavor to find an endocranial cast! WIEDERSHEIM has indeed claimed the inner impression of the skull cap for this (3)! The different openings through which he reached with flexible probes into an extensive cavity will probably have been the head spines which covered the whole skull, like Elginia. The cavity was the space that formerly received the bones of the skull roof. The position of the parietal foramen is hardly recognizable any longer in the present condition of the fossil. Only with the help of WIEDERSHEIM’s figure can they be found, and it is reproduced as a photographed cast on Pl. IV, fig. 5. The considerable diameter of the foramen agrees well with Procolophon (Pareiasaurus much smaller); many short-snouted dicynodonts are also similar.

Of the spines present the large 4.5 cm long ones go out from the squamosal, the deeper-placed second largest ones from the quadrate, and the two which are found above it take their origin from the supratemporal (posteriorly) and the quadratojugal (anteriorly), just as in Elginia. The squamosal spine is actually only 2.5 cm long, but it stands on a 2 cm high base that is isolated by a rim. It is analogous to the horn structure of mammals. Of recent lizard heads one can best compare Phrynosuchus in a sense; it only has dermal spines that are not connected with the skull bones, but in Phrynosoma not only the occiput but almost the whole body is covered with such spines.

The whole skull of Sclerosaurus must have been much flatter than that of Elginia, as already shown by the relatively closer arrangement of the skull outgrowths. The quadrate spine on the right is preserved on slab II, the other on slab I. The distance from the point of one to the point of the other measures 10 cm.

The occiput is quite well preserved only strongly displaced. The basioccipital with the large spherical condyle which, with the basisphenoid and the left exoccipital and half the supraoccipital together with the base of the left squamosal spine, is reversed so that dorsal and ventral and anterior and posterior are exchanged, however right and left remain correct. The right quadrate with the posterior edge of the right pterygoid and perhaps part of the right exoccipital are still found in their natural positions. If these bones are brought into their natural connection—as I have done with a gelatine cast—it arises that the dorsal wall of the skull sloped very obliquely from posterodorsal to anteroventral. The strong condyle represents quite a uniform hemisphere as in Pareiasaurus and Elginia. The exoccipital is directed laterally and downward. The border of the foramen magnum is unfortunately missing, however the place is clearly recognizable. I hold the flat bone piece which has lain above the left lower jaw ramus for the left supraoccipital. Below the occipital condyle, the basisphenoid extends anteriorly (here posteriorly), medially it shows a very deep groove, so that it has a U-shaped cross-section. This is also the case in Pareiasaurus and Elginia, but in particular exactly the same in Procolophon. In the continuation of the groove anteriorly, the posterior unpaired palatal opening might follow. But here the suture between basisphenoid and pterygoid is lost. On the right side one sees that the pterygoid sends a wing far posteriorly that curves dorsally on the posterior edge of the skull and reaches the quadrate. Unfortunately the largest part of the palate is missing.

1   2   3   4   5   6   7   8   9   10

Verilənlər bazası müəlliflik hüququ ilə müdafiə olunur © 2016
rəhbərliyinə müraciət