Review of the reptilia of the triassic




старонка8/10
Дата канвертавання18.04.2016
Памер457.69 Kb.
1   2   3   4   5   6   7   8   9   10


The Schaumkalk (upper Lower Muschelkalk) of Freiburg am Unstrut has yelded a rich fauna to the Museum at Halle. The Nothosauridae predominate by far in all porrible sizes and forms. Also vertebrae of Mastodonsaurus and Ichthyosaurus (?Shastasaurus) are not absent, and Placodus is also present. Then there are the limb bones of temnospondylous Stegocephalia, femora of unknown Anomodontia (Crurosaurus), etc. Vertebrae of Anomosaurus also occur here, from very different species, in relatively high numbers. Also Tanystrophaeus, which is like that from Upper Silesia, has been found, with thin-walled bones like Coelurus. Even a true crocodile is already present. These all indicate an extremely rich fauna. The Middle Muschelkalk of Esperstädt near Jena has yielded Conchiosaurus, among others.

The reptile fauna of the Upper Muschelkalk is even richer than that of the Lower. The Nothosauria predominate by far in numbers of individuals and species. They are distributed all over the German Triassic province (also in Heligoland), and are found even in the Alpine Muschelkalk (Lariosaurus from the Comersee). Numerous genera and species are based on isolated skulls, but in very rare cases the skeleton belonging to it is also known. There seems to me to be two groups among the Nothosaurus skeletons; one has a short, thick ilium and blade-like pubis, whereas the other has a rod-shaped, rather curved ilium and a non-stalked pubis. Lunéville and Bayreuth are frequently named as productive localities for Nothosauridae. True Plesiosaurus remains are found all over Germany, scattered in the main Muschelkalk, however always as great rarities. I recall once more the sacral vertebra, described above, from Bayreuth. Very fine Plesiosaurus and particularly Nothosaurus remains are found in the well-known upper bonebed of the Oelmühle near Crailsheim, and in a similar bed near Biebersfeld and Gaildorf, Württemberg, lying only a little higher. As we have seen above, large Ichthyosauria occur in the Alpine Reifling limestone. Further, several chelonian remains (Chelyzoon), which have been found in the main Muschelkalk of Laineck near Bayreuth and in the upper bonebed of Crailsheim, give evidence of the diverse population of the sea and its coast. In Arctosaurus from Arctic North America, they have a foreign representative. The vertebrae named “Anomosaurus”, which come from the Upper Muschelkalk of Thuringia (Schlotheim), Bayreuth, and Württemberg (Neckarvaihingen), belong to an unknown anomodont. Teeth and skull remains of Placodontia are well distributed, if not very frequent. They are very common only at Bayreuth, but they are found in the whole extent of the German Muschelkalk. They probably inhabited the coasts and sand banks of the Muschelkalk sea. A small representative of this group, Eunotosaurus SEELEY, also occurs in the South African Karroo. Of remains of land animals, poorly defined stegocephalian bones are found at Lunéville and Bayreuth in the main Muschelkalk. At Steinbiedersdorf, Lorraine, Prof. BENECKE discovered a femur, here described as Trochanterium, that belongs to a temnospondylous stegocephalian or a Pareiasaurus-like anomodont. The famous Crailsheim bonebed has yielded particularly numerous stegocephalian remains. Capitosaurus and Mastodonsaurus are described in several species from there. Eurycervix, based on huge, double-bladed cervical ribs, seems to have been a last large temnospondyl. In the main Muschelkalk of Bayreuth, Göttingen, Lunéville, and the Crailsheim bonebed have been found a number of vertebrae and other bones of small theropod Dinosauria, which very rarely passed from dry land into the marine deposits. These are animals that were about the size of Anchisaurus, Palaeoctomus, and Thecodontosaurus, but which remained far behind the Upper Triassic Theropoda of central Europe and South Africa. Finally, bones of true Crocodilia (Eusuchia) are already present in the Crailsheim bonebed, and in Lunéville there occur polygonal dermal armor plates with edge serrations, which in the same way belong to the abdominal armor of a crocodile (see above).

More land was already present in the time of the Lettenkohle, particularly in southern Germany. The marshy regions must have been populated then and in the Lower Keuper (Schilfsandstein) by huge crowds of heavily armored Stegocephalia (Capitosaurus, Mastodonsaurus, Cyclotosaurus, Metopias). The lower Upper Lettenkohle of Biebersfeld and Gaildorf in Württemberg are good localities. The Upper Lettenkohle of Hoheneck contains only very few Stegocephalia, for it is a more marine and brackish deposit. On the other hand, the Schilfsandstein of the lowest Keuper of the Feuerbacher Haide near Stuttgart is unsurpassed for the host of large and fine stegocephalian remains (1). In the Schilfsandstein of the same locality, a lower jaw of Belodon (arenaceus E. FRAAS sp.) has been found, as well as a fine specimen of Dyoplax, thus two parasuchian crocodiles. We have no traces of Dinosauria from this period in Europe. The coasts and seas were no less richly populated. The Placodontia are still distributed as in the Upper Muschelkalk. Large armor pieces occur at Hoheneck (Psephosaurus suevicus E. FRAAS). Placochelys, with highly decorated armor and skull, comes from the Lower Keuper of Vesprem on the Plattensee, Hungary. A great wealth of forms of Nothosauridae moved about in great numbers in the German inland sea. Enormous species alternate with very small ones. Of the latter are known in particular the delicate Neusticosaurus pusillus of the Upper Lettenkohle of Hoheneck, and Pachypleurosaurus from the Lombardy Raibl beds. The Lettenkohle also does not entirely lack large Plesiosaurus (e.g., Biebersfeld near Württemberg). The famous skeletons of Mixosaurus also come from northern Italy as well as the first flying reptile, Tribelesodon longobardicus BASSANI (and the even better known Megalocnemis BASSANI in Sched. Mus. Civico, Milan).



Mostly terrestrial reptiles are preserved from the Middle Keuper. Many remains of Rhynchosaurus have been found in Warwickshire and Gloucestershire in western England, which together with Hyperodapedon form a separate group. According to R. BURCKHARDT, Rhynchosaurus was equipped with a lizard-like armor. Bones and teeth of Thecodontosaurus and Palaeosaurus also come from the Middle Keuper of the same region (Bristol and Warwickshire). Those small theropod Dinosauria have been found again in the Swabian Stubensandstein. Similar ones occur in North America, South Africa, and Australia. The huge Dinosauria begin with Teratosaurus in the Stubensandstein of Württemberg, but they are not yet frequent; they appear there in two forms, one very large and another smaller. Together with them, bones of Belodon and Mystriosuchus are found in large numbers; they must have lived in whole crowds on the river banks. The most important localities in Württemberg are Messlach, Rübgarten, and Aixheim, but Belodon also occurs in the Middle Keuper of France and England. The famous slab with 25 specimens of Aetosaurus, a small parasuchian which is very like Ornithosuchus from Elgin, comes from Hesslach. Also, several specimens of pleurodire Chelonia (Proganochelys) have been found in Swabia, which already display the high development of that reptile group. In Silesia, Plesiosauria (Termatosaurus) occur in the marine or brackish deposits of the Middle Keuper.

The Upper Keuper and Rhaetic display a gigantic fauna of huge reptiles which moved with the strangest structures and gaits on all continents at that time. The Upper Keuper of central Europe, frequently named the Zanclodon-bed, is developed here mostly as red or colored inland deposits. In northwest Germany, western France, and western England, the similar rocks of the Rhaetic are most closely associated with these marls. In the Rhaetic, the beginning marine transgression of the approaching Jurassic begins to make itself felt, and so the uppermost Rhaetic beds frequently show a colored jumble of terrestrial and marine fossils. Soon after, the same regions were entirely under the Liassic sea. In Gresslyosaurus, the Triassic Dinosauria reach a length of almost 10 m. This largest genus is found in several localities in Württemberg and Franconia, Switzerland near Basel, the Département Jura in France, and Somerset, England (Avalonia and Picrodon SEELEY). Besides these largest forms, other different ones occur that also reach 6-8 m in length. A large number of individuals is found. Several skeletons were unearthed nearly complete; the finest ones are found in the collections at Tübingen, Stuttgart, and Poligny (France). Also, more teeth of Dinosauria occur in the uppermost Rhaetic bonebed of Württemberg and England, which indicate quite different genera; teeth are even found that recall Thecodontosaurus of the Middle Keuper. Phalanges occur in the bonebed of Aust Cliff near Bristol, which MOORE ascribed to the lower Liassic Scelidosaurus. Larger bone remains have been discovered in the Rhaetic-Keuper of Wolfenbüttel and Kreuzberg near Göttingen. Belodon also occurs in many places that have yielded Dinosauria, but not as frequently as in the Middle Keuper. The largest Belodon remains known to me are those from Schönthal near Liestal (the femur is 40 cm long) from the Zanclodon-bed. Belodon still occurs in the Rhaetic sandstone of Waldhausen near Tübingen, to conclude from an armor plate. Dermal plates of Stegocephalia (1) have been unearthed in the Upper Keuper of Somerset, together with Avalonia (Gresslyosaurus), and are especially common in Warwickshire (2); armor plates and teeth are frequent in the Rhaetic bonebed of Aust Cliff near Bristol, and the former in the same bed at Schönthal near Basel. Labyrinthodon supremus PORLIG comes from the Rhaetic sandstone of Kleinenhagen near Göttingen (Collection at Halle). Moreover it is noted here that the Stegocephalia do not become extinct before the beginning of the Liassic, as one frequently reads, but the last representatives are described from the middle Dogger of England. In the Rhaetic the true flying Pterosauria appear for the first time; Tribelesodon indeed occurs as early as the Raibl beds, but its systematic position is difficult to determine. Flight fingers and separate vertebrae, which indicate long-tailed Pterosauria, have been found isolated in several localities in Württemberg and England. Flying finger fragments from Hettingen, which GERVAIS described, are already to be ascribed rather to the Liassic. On the sea coasts, Placodontia still lived. Dorsal armor pieces are known as Psephoderma alpinum from the Alpine Dachsteinkalk of Upper Bavaria; similar smaller plates have been found in the Rhaetic of Aust Cliff (Ps. anglicum H. von MEYER), in the Rhaetic of Schönthal near Basel, and in the Lombardy Rhaetic. Chelonia (a vertebra from the Schlosslesmühle bonebed, Württemberg) also contribute to the enrichment of the coast fauna. In the Rhaetic of Bristol and Warwick, OWEN found peculiar bones and vertebrae (1), which he described as Labyrinthodon scutulatus; I suppose that this is why MOORE et al. speak of the presence of Nothosaurus in the English Rhaetic, because certain of its limb bones certainly recall femora of Nothosaurus to some extent. The vertebrae are not quite unlike caudal vertebrae of Anomodontia. The distribution of sculpture and spinal processes is striking; I cannot say with certainty to which reptile group they belong. As early as 1860, CORNALIA mentioned (2) in the Rhaetic beds of Azzarola, Lombardy, two reptile remains that have some interest, namely a hardly more closely identifiable “lower jaw bone of a crocodile”, and a “median plate of the carapace of a Cistudo or Emys”. Both as well figured. The latter piece has clearly serrated side edges and thus could belong to a crocodile or a chelonian, however it is not Psephoderma. R. OWEN also described three extremely small vertebrae from Somerset that could probably belong to Chelonia (3); that figured is a cervical, not a dorsal vertebra as OWEN thought. Peculiar bone pegs occur in the Aust Cliff bonebed, which remind me very much of the pegs on the lower jaw of Pareiasaurus. But what they really are cannot be said. But in any case small Anomodontia of the group Gomphodontia lived in Europe at this time, I mean Microlestes, Hypsiprymnopsis (4), and Triglyphus. The teeth of Microlestes and those of Diademodon from the South African Karroo show no important differences at all beyond the size difference. But Diademodon belongs in the narrow group of the Gomphodontia, of which the skull and entire skeleton are known; thus the reptilian nature of Microlestes cannot be doubted—this has been the view of SEELEY and several other experts for a long time; nevertheless, Microlestes is shown in all the textbooks as a multituberculate mammal. The small teeth of Microlestes have been found in the Rhaetic bonebed of Degerloch, and more recently in several specimens from Olgahain near Tübingen. However at Holwell, Mendip Hills, near Bristol, MOORE has collected 29 teeth from one quarry over a long time, and DAWKINS has done the same at Watchet. It is very likely that Triglyphus (several teeth) from Bebenhausen (Württemberg) is also a gomphodont, for the similarity of the teeth to those of Tritylodon is very great, and this has the skull structure of an anomodont from the named group (pre- and postfrontal identifed according to R. OWEN and SEELEY). To conclude from the tooth structure, Microlestes must have been a very small, probably insectivorous reptile; Triglyphus was probably larger (5). From such always isolated finds, one can conclude that the dry land was populated by a fauna that stood in direct connection with that of the beginning of the Triassic and with the contemporaneous ones of South Africa and north Russia. In the uppermost Keuper and Rhaetic, the influx of the Liassic marine transgression sometimes makes itself felt. Thus in the uppermost Keuper of Schönthal near Basel, one finds, between Dinosauria and Belodon remains, teeth and vertebrae of Plesiosaurus; the vertebrae (see above) reach an unusual size. Also teeth (Termatosaurus albertii) and vertebrae of Plesiosauria occur in the Swabian bonebed and the Rhaetic Lissauer breccia of Noczurry and Gattentag and near Lübnitz, Upper Silesia; Plesiosaurus (Termatosaurus) are also found near Autun and near Göttingen. Plesiosaurus is even frequent in the Rhaetic of Aust Cliff. Ichthyosauria also are not infrequent there. Parts of a large lower jaw of Ichthyosaurus lie in the Museum at Bristol. Ichthyosaurus remains have also been found near Autun, also rarely in the Swabian Rhaetic bonebed.

Central Europe was subject to variations during the Triassic. We may find in one and the same locality a continental fauna in older Triassic beds, in younger beds a coastal and marine fauna, and in the youngest again a terrestrial fauna. Therefore it is clear that terrestrial animals could not evolve independently and continually in Central Europe. In order to learn about such a continental fauna, we must turn to South Africa, north Russia, and India.

South Africa (i.e., Cape Colony and Boer states) had nearly unbroken continental evolution from the Permian to the Jurassic (Mesosaurus beds!). Thus the well-known rich anomodont fauna could be more highly developed there. It has hitherto not been feasible to establish a succession of separate zones for them with sufficient material and thoroughness. SEELEY has indeed tried to divide the Karroo into five geographical and at the same time stratigraphic zones. From the oldest division he named Pristerodon, Oudenodon, Anthodon, and Mesosaurus; from the second, Pareiasaurus and Tapinocephalus; from the third, the cynodonts, Endothiodon, Procolophon; from the fourth, the Theriodontia; and from the fifth, Euskelosaurus and Massospondylus. However this subdivision is to be accepted with some caution, for it is hardly conceivable that, e.g., Oudenodon appears before Dicynodon. However, from its paleontological content, zone 5 agrees very well with the uppermost Triassic of Central Europe, England, and North America, which always contain the large Dinosauria.

The Reptilia of the Karroo, as described by R. OWEN, HUXLEY, and SEELEY, stand alone in diversity. There are no fewer than 46 genera of Anomodontia with ca. 120 species. This fact alone is evidence of the long and great evolution.

Most lifestyles of living mammals are represented in those ancient Anomodontia. This is reflected particularly in the teeth and the structure of the limbs. The Pareiasauridae, Gorgonopsia, Dinocephalia, and some of the Dicynodontia are extremely stocky and strongly built. Several Dicynodontia and particularly Theriodontia have a delicate skeleton and must have been agile animals. Several Stegocephalia also lived together with the Anomodontia; of Temnospondyli there are Petrophryne OWEN (= Micropholis HUXLEY) and a species of Eryops (africanus LYDEKKER (1)); of Stereospondyli only the genus Rhystidosteus is represented. Petrophryne is a very ancient form that recalls many Carboniferous genera, and Eryops is found elsewhere in the Permian of Texas. Only two genera indicate that they were confined to the water, and at least one even in salt water, namely Eunotosaurus SEELEY and Mesosaurus. I have (see above) tried to prove that Eunotosaurus belong to the Placodontia, and these were probably coastal animals, as one must conclude from their teeth. Mesosaurus is a very primitive sauropterygian from the Kimberley shales (= Mesosaurus beds), which are of marine origin. It is striking that the whole Karroo lacks Parasuchia and Crocodilia (2).

A partly similar and no less interesting reptile fauna was discovered a few years ago by Prof. AMALITZKY in continental beds of north Russia (3). He has ascribed an Upper Permian age to it, however one could perhaps also conclude a Triassic age from the occurrence of the plants Gangamopteris, Glossopteris, etc. together. Most nearly or quite complete skeletons lie all in one and the same direction in an old river bed, which is now being laboriously uncovered. Pareiasauria are predominant in numbers, then Gordonia, a dicynodont, which is already known from Elgin, a skull of Geikia (an oudenodont from Elgin); Inostrancevia and Lycosaurus, two closely related genera , are particularly huge; Kistecephalus is also present, and a series of still undetermined skeletons; a single Deuterosaurus (4) was also found but it still partly unprepared. Two genera of Stegocephalia are also present, of which one is like Melanerpeton. The Pareiasauria, which separate into several species, are distinguished by noteworthy bizzare head-spines, and their entire back is covered with round, sculptured bone plates. In this they differ not a little from the South African ones, and at the same time preserve a truly younger appearance than the latter, because such extreme decorations are not primary but of secondary type. The skeleton mounted in Warsaw with a high back and rather lower-hanging head looks more natural than the specimens displayed in London. The knobby, spiny appearance of the head gives the impression of a mimicry protection arrangement by matching the stony ground. For this clumsy animal must have been a sluggish herbivore, which certainly must have suffered from the fierce Inostrancevia with its long, serrated, Machairodus-like fangs (one skull of Inostrancevia is 57 cm long). Pareiasaurus and Lycosaurus are both South African types that do not occur in other Russian (Permo-Triassic) continental deposits, likewise Kistecephalus. Only the Procolophonia related to Pareiasaurus have already been found beyond South Africa, in Scotland and central Europe (Rheinthal), and both times in armored forms; the skull is equipped with numerous long spines (Elginia and Sclerosaurus), as is the case in the north Russian Pareiasauria but not in the South African. The Dicynodontia, or rather the Oudenodontia, of north Russia are not identical with the South African and Indian, but with the more closely neighboring fauna of Elgin; in both places there are Gordonia and Geikia, both with a slender skeletal structure. The Parasuchia are also entirely absent here, for they first appear in the Upper or Middle Triassic.

The Triassic Maleri Beds of east India have yielded a fauna partly recalling that of South Africa. Particularly numerous Dicynodontia are known from them, which resemble neither those from South Africa, Scotland, nor north Russia. Together with these are found temnospondylous Stegocephalia, such as Xestorhytias, Gondwanosaurus, and Brachyops, and stereospondylous forms such as Pachygonia and Gonioglyptus. HUXLEY has described a temnospondyl related to these from the Australian Triassic as Bothriceps. Hyperodapedon, otherwise known only from Elgin and Devon, has also been found in India. Parasuchia and Dinosauria seldom compete with each other. Thus teeth were found in India that have been ascribed to the genera Epicampodon and Massospondylus. They are without doubt of Upper Triassic age.

In these youngest Triassic beds of South Africa, a considerable dinosaur fauna has also been preserved. Euskelosaurus and perhaps also Orosaurus are huge Zanclodon- and Gresslyosaurus-like animals. Bathygnathus from the Arctic of North America also belongs to them. However the smaller forms such as Hortalotarsus, Massospondylus, Pachyspondylus, and Leptospondylus are partly after the type of Thecodontosaurus of Europe, Agrosaurus of Australia, and Anchisaurus and Ammosaurus, Palaeoctomus and Typothorax (ex parte) of North America. Whether Dystrophaeus from Utah is really an orthopod, as COPE thinks, could not be previously established. Tanystrophaeus COPE from the Triassic of North America is a small anchisaurid or coelurid, whereas Tanystrophaeus H. von MEYER from the Muschelkalk and Lettenkohle of Germany seems to have been a dinosaur standing isolated.

The North American Upper Triassic also contains a series of Parasuchia: Belodon, Stegomus, and Rhytiodon are examples. Eupelor and Typothorax (ex parte) are Stegocephalia, and I suppose finally (see above) a cryptodire chelonian in Arctosaurus.

The astonishing abundance of Triassic Reptilia that have passed before us just now very briefly are mainly composed of faunas that still have a Paleozoic character. In particular, there are temnospondylous Stegocephalia, Proterosauridae, and Clepsydropidae. Characteristic of the Triassic are the stereospondylous Stegocephalia, the larger part of the Anomodontia, the Nothosauridae (specifically from the German Triassic province), and the Parasuchia (Upper Triassic).

In the following Liassic, the large order Anomodontia is no longer present; the Parasuchia are also absent. Both impart a strange characteristic stamp on the fauna of the Triassic continent. Only a few Stegocephalia prolong a wretched existence into the Dogger. Only the Pterosauria could be said with certain justification to be new for the Liassic and Triassic, although they first appear at the end of the Triassic. The role of Parasuchia is taken over by the probably more marine Eusuchia, which were also present in the Muschelkalk, but the number of individuals is still very much reduced. The Ichthyosauria and Plesiosauria are not obvious; they are rulers of the sea from now on; probably both these groups were present on the stage of life already in the Muschelkalk, but the Nothosauridae prevailed in numbers then so that the others could not yet evolve. Now the Nothosauridae die out completely. On the threshold of the Jurassic Period, when the ocean moves in and blots out the specific features and living conditions of the German inland sea, the obstacles to free development of the marine reptiles are removed. The terrestrial Dinosauria continue, but we have little knowledge of them from the beginning of the Jurassic.

1   2   3   4   5   6   7   8   9   10


База данных защищена авторским правом ©shkola.of.by 2016
звярнуцца да адміністрацыі

    Галоўная старонка