Sauropods

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Sauropods
Skeletal reconstruction of Diplodocus in Berlin Central Station

Skeletal reconstruction of Diplodocus in Berlin Central Station

Temporal occurrence
Upper Triassic to Upper Cretaceous ( Norium to Maastrichtian )
228 to 66 million years
Locations
  • Worldwide
Systematics
Archosauria
Ornithodira
Dinosaur (dinosauria)
Lizard dinosaur (Saurischia)
Sauropodomorpha
Sauropods
Scientific name
Sauropoda
Marsh , 1878

The sauropods (Sauropoda; old Gr . Σαύρα saúra "lizard" and πούς / ποδός pod-, "foot") are a group of lizard- pelvis dinosaurs (Saurischia), which belong to the Sauropodomorpha .

The sauropods are one of the most biodiverse and widespread groups of herbivorous dinosaurs . Their habitus was characterized by a barrel-shaped trunk on four massive legs, a long neck and tail, and a disproportionately small head. The sauropods as the largest land-dwelling animals in the history of the earth went with their gigantism to the limits of what is physiologically and physically possible within the blueprint of the land vertebrates . In the animal world , only a few species of whale achieve even greater body mass.

The sauropods appear in the Upper Triassic about 228 million years ago and reached their greatest biodiversity during the Upper Jurassic . They became extinct 66 million years ago, at the end of the Cretaceous Period , along with all other non-avian dinosaurs. Their fossil remains can be found on every continent . Among the dinosaurs, the sauropods are the second most species-rich group; there are over a hundred genera with more than 150 valid species (as of 2011). However, a complete skeleton is known of only five genera, since such large bodies on land were extremely rarely embedded in the sediment as a whole .

Sauropods are among the most depicted dinosaurs in popular culture and appear in many documentaries and feature films. The sauropods Brachiosaurus / Giraffatitan , Diplodocus and Brontosaurus are among the most popular dinosaurs.

features

General

Giraffatitan in the Berlin Natural History Museum

Sauropods were mostly very large, sometimes gigantic, always quadruped (four-footed) locomotives herbivores . The body structure was similar in all representatives and is characterized by a mostly extremely long neck and tail, a massive, barrel-shaped body with columnar legs and a proportionally very small head. Their size ranges from six meters in length in the case of the island form Europaaurus, discovered in Germany, to over 30 meters in length and presumably over 70 tons in weight for giant forms such as Argentinosaurus , whose actual size can only be estimated, however, due to the mostly fragmentary finds.

Somewhat older images show sauropods, how they stretch their long necks like a giraffe to graze trees almost vertically and drag their tail behind them. Today it is believed that most sauropods held their necks horizontally above the ground. The extent to which the neck could be moved laterally and vertically, however, depends on the individual species and their vertebral structure. The almost complete lack of tail prints in fossil tracks suggests that the tail was always held above the ground.

skull

Finds of skull bones, which belong to the most important skeletal parts for the systematic classification , are extremely rare in sauropods. Chure et al. found in 2010 that skull material has been found in less than a third of the known genera and complete skulls are even rarer. This is attributed to the very weak connection between the atlas (the first cervical vertebra) and the skull, which means that the latter can easily separate from the main skeleton and thus be lost after the death of the animal.

Skull of Diplodocus

There are two main types of sauropod skulls: On the one hand, the flat, long-nosed type with long, pin-like teeth, as found in the Diplodocidae , and on the other hand, the curved, short-nosed type with thick, spatula-shaped teeth, such as most other sauropods have. The original form presumably mediated between these two types, as suggested by traditional skull bones in the basal species Shunosaurus and Omeisaurus . In some advanced titanosaurs , many of the diplodocid-type features have evolved convergently so that the skull takes on a diplodocid-like appearance.

Skull of Camarasaurus

As with all sauropodomorphs , the skull has enlarged skull openings for the nasal passages (naris), which are usually located directly in front of the orbital window ( eye socket ). The nasal passages are rather small in Diplodociden skulls, but in other species such as Camarasaurus or Brachiosaurus they are about the same size as the orbital windows and form a bulge on the top of the skull, which can be clearly seen especially in Brachiosaurus and Europäischeaurus . In contrast, the antorbital window , an additional opening in the skull of dinosaurs and other archosaurs , is quite small in sauropods. The muzzle is broad and rounded. The premaxillary , a bone in front of the upper jaw, is robust and equipped with four teeth; in diplodocids it is extremely thin and elongated and extends to the orbital windows.

The number of teeth decreased in the evolution of the sauropods. The basal species Shunosaurus still had 21 teeth each in the upper and lower jaw and thus resembled the prosauropods , other sauropods had fewer teeth. Compared to other dinosaurs, the rows of teeth are short. In neosauropods they end at the level of the antorbital window, in diplodocids even only the foremost end of the snout is equipped with teeth. In many sauropods the teeth are directed forward, but in Brachiosaurus or the Nemegtosauridae they are approximately vertical. In the jaws, there were usually one or two spare teeth in stock under each useful tooth, but in Diplodocidae there may be more than seven.

whirl

Sauropod vertebrae, especially the neck and dorsal vertebrae, usually have a variety of cavities and additional struts, which resulted in a reduction in the total weight that is advantageous for the animals. This created an enormous variety of shapes, which is why the vertebrae are very important for diagnosis. Them can thus be particularly common autapomorphies (for individual taxa specific characteristics) make - they weigh the disadvantage of often missing skull material to part.

Dorsal vertebrae of the Europasaurus

An important feature for identifying different genera is the number of dorsal vertebrae (vertebrae) and the number of cervical vertebrae (neck vertebrae). The earliest sauropods still had 10 cervical vertebrae, 15 back vertebrae, three sacral vertebrae (pelvic vertebrae), and 40–50 caudal vertebrae (tail vertebrae). To enable the development of a longer neck, up to six new cervical vertebrae were added in the evolution of the sauropods. In addition, in many species, the cervical vertebrae elongated - in some cases more than a meter - and dorsal vertebrae turned into cervical vertebrae. At the same time, the number of dorsal vertebrae decreased, while the number of sacral vertebrae in neosauropods increased to five due to the integration of two tail and one dorsal vertebrae, which stabilized the pelvic region. The number of caudal vertebrae remained about the same, only the Diplodocidae had 70–80 caudal vertebrae due to the development of a whip-like tail.

The middle and posterior vertebrae showed, in addition to the usual mechanical connections between two vertebrae (the post- and prezygapophyses), another connecting element , the hyposphene-hypantrum connection : Below the postzygapophyses there is a rearwardly directed process (hyposphere), which fits into a hollow (hypantrum) of the following vertebra. This mechanism stabilized the spine, but at the same time restricted its mobility. This feature is regarded as a jointly derived feature ( synapomorphism ) of the Saurischia and thus developed before the sauropods. Different groups of sauropods have independently lost this trait, for example the Rebbachisauridae and the Titanosauria .

In Shunosaurus and especially in the Diplodocidae, the chevron bones on the underside of the tail have developed into a characteristic "double bar" shape; Processes at the bottom of the bone point forward and backward.

Shoulder girdle and limbs

Amargasaurus skeleton

The large, elongated shoulder blade ( scapula ) is connected at the lower end to the oval to semicircular, sometimes square coracoid (raven bone). Additional small, slender bones have been found in various genera, such as Jobaria and Diplodocus ; although Nopcsa (1905) interpreted them as penis bones , these are now regarded as collarbones .

The front legs are - with about 75 percent of the length of the hind legs in most species - quite long. The robust humerus is always longer than the forearm. Wrist bones are rarely found, so far not a single one of the Titanosauria group is known. The basal form of Shunosaurus still had three bones in the wrist, Brachiosaurus and Camarasaurus had two, while Apatosaurus only had one wrist bone. The five fingers were almost vertical, with only the fingertips touching the ground ( digitigrad ). The number of finger bones decreased during the evolution of the sauropods; For example, more primitive species like Shunosaurus had a finger bone formula of 2-2-2-2-1, many later species had a formula of 2-1-1-1-1. The Titanosauria showed only extremely reduced finger joints, while carpal bones and claws seem to be completely absent. The thumb often had a clearly enlarged claw ( phalanx 1-2).

The femur (thigh bone), often the longest bone in the skeleton, is straight and sturdy. The ankle joint consists of the astragalus (ankle bone), which fits on the lower head of the tibia (shinbone), and the much smaller calcaneus ( heel bone ), the upper hollow of which sat on the lower end of the fibula (calf bone), but apparently lost in Opisthocoelicaudia has gone. The five toes are spread apart. The metatarsals were aligned almost horizontally and partially touched the ground (semidigitigrade), so sauropods were not pure toe-walkers like all other Saurischia. The underside of the foot was probably supported by a fleshy pad. The hind legs have far more toe bones than the front legs have finger bones - the phalanx formula is mostly 2-3-4-2-1.

Osteoderms and skin prints

Osteoderm of Ampelosaurus atacis

Osteoderms (skin bone plates) have so far been detected in ten genera from the group of Titanosauria . Those in the dermis located (dermis) and formed bone were found in the form of millimeter-sized, mosaic-like arrangement bones and in the form of plates with up to 59 centimeters in diameter, whose surface partially shows comb-like or pointed projections. Asymmetrically shaped osteoderms presumably covered the flanks of the animals, while bilateral symmetrically shaped osteoderms possibly ran in a row on the midline of the body above the vertebral spines. Since at most a few osteoderms were found in connection with connected parts of the skeleton, the number of osteoderms in living animals was probably not sufficient to provide effective protection against predators . The osteoderms of these sauropods may have served as a calcium reservoir instead.

Rare finds of skin imprints show that, like other dinosaurs, the skin surface was covered with tubercle-like , non-overlapping scales. As shown by Tehuelchesaurus skin prints , the scales in the back region were larger than in the abdominal region. At least some representatives of the Diplodocidae showed a series of triangular, keratinous spines that ran along the back line.

Paleobiology

Habitat

Although Marsh and Cope initially imagined the sauropods to be terrestrial because of the structure of their legs , they later believed in an amphibious way of life in shallow water. This idea lasted well into the twentieth century. This idea was supported, among other things, by the long neck and large nostrils arranged on the top of the head, which were ascribed a snorkel-like function, and the air-filled (pneumatic) vertebrae, which, according to some researchers, were used for buoyancy could have. In contrast, a purely terrestrial way of life has been assumed since the 1970s. It has been shown that their physique - the columnar legs, compact feet, and barrel-shaped body - have clear analogies to modern large terrestrial animals such as elephants and rhinos.

Overall, sauropods seem to prefer flat, moist areas - often delta or coastal regions - as shown by a large number of deposits with sauropod finds. Even the late Cretaceous Mongolian species Opisthocoelicaudia and Nemegtosaurus do not come from the famous deposits of the Djadochta Formation or the Barun-Goyot Formation , when the climate was dry, but from the overlying Nemegt Formation , which consists of river deposits . However, other researchers suggest that sauropods would prefer to live in semi-arid, perhaps savanna-like areas with seasonal rainfall, as apparently the Morrison Formation did .

Diet and Function of the Neck

All sauropods were herbivores - earlier theories that suggested mollusks or even fish as food are now considered refuted and were strongly linked to the idea of ​​an amphibious or aquatic way of life. To date, however, there is no clear, direct evidence of which plants served the sauropods as food. Although fossil stomach contents were described in 1964, this was called into question because the plant material might have entered the skeleton after the death of the animal. Also coprolites (fossilized feces), which were found formation Morrison in North American can not safely be assigned to the Sauropoden. Possibly conifers , tree ferns , ginkgos , ferns , horsetail and, during the late Cretaceous, also bedspreads played a role as a source of food. Grass did not appear until the Late Cretaceous, but has recently been found in coprolites from India, which probably belonged to late Cretaceous titanosaurs. However, according to the researchers, grass was not a large part of the diet of these sauropods.

Mamenchisaurus , a very long-necked sauropod

The feeding mechanisms vary significantly between different sauropod groups. A precise cutting mechanism seems to have developed early in the evolution of the sauropods, as indicated by facets on the teeth that were created by the meshing of the teeth. In this way, vegetation could be cut off and swallowed with a strong bite, although extensive chewing would hardly have been possible due to the lack of jaws - the strong tongue could, however, have partially displaced food in the mouth for further chopping.

The cutting mechanism, which represents an improvement over the relatively simple adaptations of the prosauropods, is found particularly in basal eusauropods such as Shunosaurus , but also in the later genus Camarasaurus . In Brachiosaurus and Titanosauria, the teeth probably did not fit into one another, but were directly opposite one another when the teeth were closed. Diplodocidae, on the other hand, probably had a completely different feeding mechanism, which suggests signs of wear and tear, which presumably occurred when the tooth came into contact with food. Diplodocidae could eventually strip off branches to loosen the leaves; this theory is also supported by other aspects of skull morphology, such as the long snout or the comb-like arranged pin-like teeth.

The question of what functions the long neck had in feeding has been and is hotly debated since the discovery of such fossils. The traditional notion of sauropods as they grazed tree tops like giraffes with their necks stretched upwards has been questioned since 1999 by computer-aided studies, particularly by Perrisch and Stevens. Since, according to the results, the head of many species would only be just above the ground in its neutral position, the researchers suspect that the neck could have served to graze a large area "like a vacuum cleaner" without having to move the main body. These researchers believe that even Brachiosaurus , which was closer to the structure of a giraffe with elongated forelegs than other sauropods, usually only kept its neck level to slightly downward.

Based on their results, Perrisch and Stevens speculated that diplodocids, dicraeosaurids and also Euhelopus feed on vegetation close to the ground. Camarasaurus, on the other hand, appears to have had a very flexible neck, and the head of Brachiosaurus was higher above the ground than other sauropods due to the long front legs. For these sauropods, the researchers suspect that they could have fed on both high-altitude and low-level vegetation. Some researchers also believe that Camarasaurus and Brachiosaurus may have eaten tougher plant material such as tree ferns or conifers because of their wide, spatula-shaped teeth and other skull features, while species with pin-like teeth such as diplodocids and some titanosaurs such as Nemegtosaurus consumed relatively soft plants could have.

This eating of soft vegetation close to the ground found its extreme with the Rebbachisauriden Nigersaurus , which with a very light skull and a strongly broadened mouth probably possessed a very modest jaw musculature, which only allowed soft food. Evidence from the inner ear of this genus has shown that the head, which is usually directly above the ground, was directed downward by −67 ° in the neutral position. In Diplodocus , the ground-level view of many researchers recorded vegetation, a neutral head position was of -37 ° while Camarasaurus had a -15 °.

Another study by Berman and Rothschild, supported by computed tomography , found two different types of cervical vertebrae: a robust type in Camarasaurus and an undetermined titanosaur, and a delicate type in Diplodocus , Apatosaurus , Haplocanthosaurus , Barosaurus and Brachiosaurus . The researchers concluded from their results that the robust vertebral type could indicate an almost vertical posture of the neck, while animals with the graceful type kept the neck approximately horizontal.

In the past, other hypotheses have been made about how sauropods might have fed. Stevens and Perrisch noted, for example, that diplodocidae may also have fed on aquatic plants. Due to the construction of the skull and the fact that it was clearly tilted downwards in a neutral position, the animals could have maintained visual and olfactory contact with the environment while grazing directly above or in the water .

A diplodocide also takes on stones (gastroliths) when consuming a cycad (cycadophyta).

The nostrils of the sauropods are often shown placed in the back of the skull above the eyes, depending on the position of the nostrils. Because of the retraction of the nostrils, some researchers have speculated on a proboscis that would have played a significant role in feeding - but other authors dismiss this idea. Coombs (1975) notes that it is unlikely that sauropods possessed the necessary facial muscles. As Witmer (2001) suggests, the nostrils could actually have been located much deeper towards the snout.

There is only speculation about the amount of food that had to be consumed by a sauropod as well as about internal digestive organs, since there are no fossils. In general, due to the size of the main body, a long intestine is assumed which would allow fermentation by microorganisms. Many of today's birds swallow stones called gastroliths (stomach stones) to crush their food in the gizzard . Since strangely smooth polished stones are occasionally found in sauropod skeletons, it is assumed that gastroliths were also found in sauropods. However, direct evidence is very rare and in fact only a few species may have possessed gastroliths. More recent research by Oliver Wings and Martin Sander , who carried out studies on recent ostriches , has questioned the existence of a gastric mill in sauropod dinosaurs that works with gastroliths. Gastroliths were rarely found in sauropod fossils; In addition, they are rough and unpolished in birds, and the total mass of the swallowed stones is too small in relation to the body mass of sauropods, according to the researchers.

size

Size comparison of some very large sauropods

The most striking feature of almost all sauropods was their enormous size, which was already evident in the earliest sauropods in the late Triassic. The largest sauropods, of which almost complete skeletal material is known, are Diplodocus with a secured length of 27 meters and the shorter but more massive Brachiosaurus with a length of 22 meters. References to even larger species can be found in various lineages; the actual size can only be estimated due to the mostly fragmentary remains. The determination of the weight is particularly difficult and led to much discussion - Brachiosaurus was estimated in a study by Colbert (1962) at 80 tons, while a study by Béland and Russel (1980) came to only 15 tons. Today a weight of 30 tons is given for Brachiosaurus .

Diplodocus hallorum , living reconstruction

The particularly large sauropods include the Diplodocid Supersaurus , which was estimated to be 33–34 meters long and weigh 35–40 tons. Seismosaurus , which is often traded in the popular media as “the longest dinosaur” with a length of over 50 meters, is now considered a juvenile synonym with Diplodocus and, according to recent research results, reached a length of around 30 meters. The Argentine titanosaur Argentinosaurus , which was estimated at a length of 30 meters and a weight of 73 tons, was much more massive . The brachiosauride Sauroposeidon is said to have become an estimated 32 meters long, but is only known from a few cervical vertebrae. Amphicoelias fragillimus , which was described by Cope in 1878 using a huge, incomplete vertebra, is mysterious . However, shortly after its description, the vortex appears to have been lost; However, the description suggests a diplodocids that - would he like the same physique Diplodocus had - would have been up 58 meters long and 9 meters.

The question of why sauropods became so large cannot yet be answered with certainty. Advantages of such a size could be the development of additional food sources that would not be accessible to smaller herbivores, as well as protection from predators. Some researchers suggest that increasing body volume increases the efficiency of digestion, especially in nutrient-poor plants. A larger body naturally has a longer digestive tract, which means that food stays in the body longer. This allows today's large animals such as elephants , rhinos or hippos to survive with low-energy food sources, especially in connection with fermentation in the large intestine or in special chambers. Sauropods could have survived periods of drought in this way.

breathing

Many researchers assume that sauropods had an air sac system similar to that of today's birds, as probably did the theropods and pterosaurs . Evidence of this is provided by the vertebrae with their complex pits (fossae), openings (foramia) and chambers, which may have been filled with diverticula (protuberances) of the air sacs, as in birds. While in basal sauropods only the presacral vertebrae were pneumatized (filled with air), this feature developed in the sacral vertebrae of many neosauropods . Independently of each other, pneumatized anterior caudal vertebrae developed in the Diplodocidae and the Titanosauria. Finds of vertebrae in juvenile animals show only very simple chambers, which is why it is assumed that individuals in an early stage of development did not have pneumatized vertebrae.

The question of how the large dead space caused by the long neck could be overcome raises problems if one proceeds from the lizard-like respiratory system, which is also found in mammals . Gale (1998) hypothesized that sauropods would have to use 50–100% of their metabolic energy to transport the huge amounts of air they need into and out of the body . This dead space could be compensated with an airbag system, as it is also the case with birds, since oxygen-containing air can flow through the lungs both when inhaling and when exhaling.

Researchers working with Daniela Schwarz reconstructed soft tissue such as air sacs, ligaments and muscles in the cervical vertebrae of diplodocids and dicraeosaurids based on comparisons with crocodiles and birds. The arrangement of the diverticula showed that the air sacs, in interaction with ligaments and muscles, could have had a support and stabilization function for the neck. This would make thick neck muscles superfluous for stabilization, which would have resulted in further weight reduction of the neck.

Thermoregulation

The question of whether sauropods were poikilothermic (alternating warmth), tachymetabolic (with increased basal metabolic rate) or even homoiothermic (equally warm) is the subject of many discussions of thermoregulation . A common assumption is that the sheer mass makes an additionally increased metabolism for maintaining the body temperature superfluous or even counterproductive. The presumed fermentation of food by microorganisms could have been an important source of heat. Additional metabolism could easily have overheated the animal as a large body can hold heat much better because the skin surface area is much smaller compared to the body mass than that of a smaller animal.

Wedel (2003), who assumes an air sac system for breathing, notes, however, that, as in the case of birds, evaporation (evaporation) could have taken place in the air sacs, which is a very effective cooling mechanism. The core of the body could have been cooled directly in this way. He also states that sauropods have a very rapid growth rate that is comparable to that of mammals; while crocodiles, for example, have a much slower growth rate. Therefore, the researcher considers an increased metabolism (tachymetabolism) or even homoiothermia in sauropods to be likely.

Locomotion and fossil footprints

A sauropod trail near Barkhausen (Lower Saxony). A forefoot print can be seen on the lower left.
Formerly a footprint on the Tinzenhorn in Graubünden , discovered in 2006 in the main dolomite , further traces were found on Piz Mitgel

All sauropods probably moved exclusively quadruped (four-footed), but carried their main burden on their hind legs. The limbs were moved by relatively weak muscles; the gait may have been similar to that of elephants . Rothschild and Molnar (2005) found fatigue fractures in five percent of the foot bones they examined and concluded that the main propulsion came from the hind legs. According to an estimate by Alexander (1991), the maximum speed was 25 km / h; fossil tracks, however, indicate a normal speed of only 2–4 km / h.

Sauropod tracks and tracks can be found all over the world. Since they always only represent a brief extract from the life of the animal, they can contain information that cannot be obtained from bone finds alone. Since the digitigrade fingers (touching the ground with the tips of their toes) are arranged like a hoof, the imprints of the forefeet often appear crescent-shaped - they are in the track sequence directly in front of the much larger impressions of the hindfoot.

In general, two types of sauropod track sequences can be distinguished based on their width, which indicate different modes of movement. The “broad-gauge” type ( Brontopodus ) shows a clear gap between left and right impressions and often comes from the Cretaceous period; the causers are probably titanosaurs. The "narrow-gauge" type ( Parabrontopodus ) is common in Jurassic strata and comes from non-titanosaurs such as the Diplodocidae - the impressions border on the center line of the track sequence, so they are close together. The reason for this difference in tracking is due to a different alignment of the legs; For example, the thigh bones of the titanosaurs were directed slightly outwards, while in other sauropods they stood vertically under the body. More flexible knee and elbow joints suggest that the lower legs of the titanosaurs contributed more actively to locomotion than those of other sauropods.

Some sauropod tracks only show prints of the front legs. The first such discovery in Texas was interpreted by Bird (1944) as an indication of a swimming sauropod that only touched the ground with its forelegs. Today it is believed that the forelegs usually sank deeper into the ground than the hind legs and therefore remain visible as so-called underscores, even if the overlying layers of sediment and the impressions of the hind foot are lost.

Reproduction and development

Fossil eggs that can be clearly attributed to sauropods are very rare and have only been detected in the last decade. For example, egg finds from France were attributed to the titanosaur Hypselosaurus priscus as early as 1930 , but no evidence of sauropod origin can be proven, as no remains of embryos or young animals were found on the eggs. Bakker (1980) suspected that sauropods could have been viviparous and given birth to relatively large young, which he concluded, not least because of the large pelvic canal.

Nest building and egg laying in a titanosaur .

In Auca Mahuevo in Argentina, thousands of clutches with eggs that can be assigned to titanosaurs were found. Some of the eggs contain bones from embryos , including full skulls. The eggs are almost round, measure 13-15 cm in diameter and have a volume of about 800 cm³. The nests had a diameter between 100 and 140 centimeters, were 10 to 18 centimeters deep and allegedly housed 20-40 eggs. These findings allow insights into the breeding behavior of the sauropods: The animals dug out the nests, but did not bury the eggs with soil. The number of eggs shows that the sauropods lived in flocks when the eggs were laid; different levels with nests suggest that they used this place several times at different times for breeding. Pores in the eggshells indicate a high level of moisture in the nest, and from round ornaments that may have served to keep the pores free, some researchers suggest that sauropods have covered their eggs with plant material. However, the researchers rule out brood care after the eggs have been laid, as neither trampled eggs nor trampled ground (" dinoturbation ") were discovered. Another argument against brood care is the difference in size between newly hatched juveniles and adult animals - juveniles could have been only one meter long and weigh less than ten kilograms, while adult animals sometimes reached the size of whales.

Finds of young animals are generally rare, which is why there are only a few studies on the development ( ontogenesis ) of a sauropod. By comparing the embryo skulls from Auca Mahuevo with well-preserved titanosaur skulls ( Nemegtosaurus and Rapetosaurus ), indications of strong deformations of the skull during growth were found: bones were rearranged while the snout was significantly elongated. It used to be assumed that growth would be slow and steady. Calculations by Case (1978), which are based on the growth rates of today's reptiles, came with Hypselosaurus on a sexual maturity with 62 years and a full size with 82-118 years. More recent, bone histological analyzes examine the growth based on the structure of the bone tissue , and conclude that growth is significantly faster, similar to that of today's mammals. The tissue of fossil bones can be reconstructed using cavities and the arrangement of minerals in the bones, including the blood vessels and collagen fibers . By comparing it with today's vertebrates, one can, among other things, infer the rate of growth in different phases of development: Sander (2000) stated that Janenschia was sexually mature at 11 years, maximum height at 26 years and death at 38 years. The researcher also shows that sauropods reached sexual maturity long before their maximum size - Brachiosaurus was sexually mature at 40% of its full size; with Barosaurus it was 70%.

behavior

Unlike other sauropods, Diplodocidae had a long and very agile, whip-like tail end. A widespread hypothesis is that Diplodocidae swung their tail in defense of the attacker in order to drive them away or even to injure them. However, this idea has fallen into disrepute, as the posterior caudal vertebrae neither appear stable enough nor show any damage. In addition, lateral movements of the front and middle part of the tail were only possible to a limited extent. Many researchers now suspect that Diplodocidae were able to accelerate their tail end to supersonic speed by swinging their tails and thus generate loud bangs, similar to a whip. Perhaps this could have driven away attackers; a social function is also conceivable. Shunosaurus had a fused vertebrae at the end of its tail that may actually have been used for defense.

Mamenchisaurus , erect on its hind legs

Another hypothesis suggests that some sauropods were able to stand up on their hind legs to defend themselves against predators or to eat higher vegetation, with the tail serving as additional support. Famous is a Barosaurus skeleton in the American Museum of Natural History , which is placed in such a position. In any case, many researchers doubt this idea; Stevens and Perrisch (1999) noted that such a posture must have led to problems with the blood supply to the head, since the neck is oriented towards a horizontal posture. Rothschild and Molnar (2006) admitted that the joints offered the necessary freedom of movement. However, the researchers did not find any fractures in the hand bones or the dorsal and lumbar vertebrae that must have occasionally occurred during the straightening or lowering.

There were also discussions about the function of the enlarged claw on the hand. Some researchers suspect that the claw may have been used as a weapon for defense, foraging for food, or for propping up against trees while it stood up on its hind legs. However, this seems questionable as the claw is blunt and the front legs are not very mobile. The other suggestion is that the claw could have been used to dig water holes or dig nests.

Fossil tracks running in parallel show that some sauropods lived in herds, at least for a time. The mass graves, in which sauropods are particularly common, also speak for this. The Ardely site in England, in which more than 40 tracks have been excavated, also shows a mixed herd of traces of titanosaurs and traces of other sauropods. Another trace find from Texas, the Davenport Ranch Find, has been interpreted to mean that large, fully grown animals ran on the edge of the herd to protect smaller animals in the middle of the herd. However, later studies (Lockley, 1991) have refuted this theory; to date there is no evidence of strategic structures in sauropod herds. There are also no indications of very large herds with hundreds or thousands of animals, such as those suspected in the Ceratopsia and Hadrosauriden .

Evolution and biodiversity

Early sauropods

Little is known about the early history of the sauropods. The first skeletal finds of dinosaurs come from the South American Ischigualasto Formation and are 228 million years old, while the earliest known sauropodomorphs are from the Carnian and five million years younger. However, footprints dating back 238 million years suggest that sauropodomorphs and theropods separated much earlier. Some finds that have been assigned to sauropods also come from the Carnian - their assignment has yet to be confirmed. The first finds that can be assigned with certainty to sauropods come from the late Triassic ; this is the footprint of Tetrasauropus ( Norium - Rhaetium ) and the geologically perhaps somewhat younger Isanosaurus from Thailand .

Today it is assumed that the sauropods separated from their sister group, the prosauropods , at the latest in Carnian . Their ancestors were probably basal sauropodomorphs; some researchers suggest that early prosauropods were the direct ancestors of the sauropods. However, most researchers assume that the prosauropods are a monophyletic group.

Barapasaurus , an early Eusauropod

The genera Blikanasaurus and Antetonitrus from the Norium (Upper Triassic) have characteristics of both sauropods and prosauropods and have probably already moved four-legged - whether they are really sauropods, however, is disputed. Other basal sauropods, for example Gongxianosaurus , also found adaptations to a quadruped (four-footed) way of life: the front legs became longer, the femur (thigh bone) became straight and longer than the tibia (shin), while the foot bones became shorter.

Good skull material from early sauropods is rare and is only found in Tazoudasaurus from the early Jurassic and the basal Eusauropod Shunosaurus from the middle Jurassic. Eusauropods like Shunosaurus , which include all sauropods except for a few basal species, already had characteristic features such as a rounded snout, a reduced number of overlapping, broad-crowned teeth and a precise cutting mechanism (see above). The non-Eusauropod Tazoudasaurus, on the other hand, still had many features that are reminiscent of prosauropods: The teeth did not overlap, but continued over the entire length of the lower jaw, while the snout tapered towards the front.

Sauropods in the Jura

Camarasaurus , a sauropod from the Upper Jurassic

While the biodiversity (species diversity) of the sauropods was still quite low in the late Triassic, it increased significantly in the early and middle Jurassic. In the middle Jurassic, the sauropods were distributed almost all over the world. In the Oxfordian (formerly Upper Jurassic) there was a small extinction of species among sauropods - although the biodiversity increased significantly again in the subsequent Kimmeridgian and Tithonian (later Jurassic) and reached its zenith with at least 27 known genera. In the late Jurassic the Neosauropoda , a subgroup of the Eusauropoda, made up a large part of the sauropod genera. The Neosauropoda split into two large groups: the Diplodocoidea with the families Diplodocidae , Dicraeosauridae and Rebbachisauridae , and the Macronaria , which includes Camarasaurus , Brachiosaurus and the Titanosauria .

In the diplodocoids, the widening of the snout continued, while the rows of teeth continued to shorten and mostly shifted into the tip of the snout. In the Rebbachisauriden, this feature developed to the extreme, as Nigersaurus shows from the early Cretaceous: The jaw was box-shaped when viewed from above, while the teeth in a straight row formed the front of the snout. In contrast to the development of broad-crowned teeth in basal eusauropods, the dental crowns in diplodocoids shrank, leaving only pin-like teeth. This also favored the formation of additional replacement teeth. In the Macronaria, on the other hand, a wider duct (see above) and enlarged nostrils (naris) developed, which exceeded the size of the orbital windows (eye sockets) in diameter.

Sauropods in the chalk

Alamosaurus , an Upper Cretaceous sauropod

At the Jura-Cretaceous border there was a mass extinction among sauropods, in which the biodiversity from the Upper Jurassic ( Kimmeridgian ) to the Lower Cretaceous ( Berriasian ) sank by 65 to 93 percent within 5.5 million years. The Diplodocidae and all non-Neosauropods died out, but most groups survived into the Early Cretaceous - the Rebbachisaurids, the last known Diplodocoids, are even known from the Coniacium (early Upper Cretaceous). The dominant sauropod group of the Cretaceous were the Titanosauria , a subgroup of the Macronaria and the only sauropod group that survived until the end of the Mesozoic Era. While the major continents Gondwana and Laurasia completely broke up in the Cretaceous to form today's continents, the titanosauria, with the exception of Antarctica, were widespread worldwide and brought about a great diversity: to date, over 30 genera have been described, which is more than a third of the known Sauropods.

Later titanosaurs showed some convergent developments that had already developed earlier in the diplodocoids: the teeth became pin-like and limited to the front part of the snout, the skull took on a horse-like appearance. Like the Rebbachisauriden, the Titanosauria lost the additional connections to the vertebrae (between the hyposphen and the hypantrum), which distinguished other sauropods; this gave the spine flexibility. Saltasaurids, a later family of titanosaurs, had a significantly shorter tail than earlier sauropods with only about 35 vertebrae; in addition, the finger bones were significantly reduced.

Although the biodiversity of the sauropods apparently decreased slightly during the Cretaceous, at the end of the Upper Cretaceous ( Campanian to Maastrichtian ) it reached a peak again that is comparable to the diversity during the Middle Jurassic. During the mass extinction 66 million years ago on the border between Cretaceous and Tertiary (→ Cretaceous-Tertiary border ) all sauropods disappeared.

Systematics

In the late 19th century, after Marsh (1878) coined the term Sauropoda, the systematics of the sauropods consisted only of a few families that existed on an equal footing without higher-ranking taxa (including Atlantosauridae, Pleurocoelidae, Diplodocidae and Titanosauridae ). Since this system did not allow any conclusions to be drawn about relationships and evolution within the sauropods, new possibilities were soon sought: Janensch (1920) divided the sauropods into two families, the Bothrosauropodidae and the Homalosauropodidae, to which he assigned several subfamilies. However, other authors continued the traditional system of rank families (e.g. McIntosh, 1990). Later studies were in the spirit of cladistics ; So Upchurch (1995) placed almost all sauropods in the group Eusauropoda, while he assigned more modern species to the subgroup Neosauropoda. Today the systematics of the sauropods is still controversial in many places, which is why analyzes by different authors differ in many points. A current example follows (simplified from Weishampel, Dodson and Osmólska, 2004).

 Sauropoda  
  Eusauropoda  

 Shunosaurus


   

 Barapasaurus , Cetiosaurus


  Neosauropoda  
  Diplodocoidea  

 Rebbachisauridae


   

 Dicraeosauridae


   

 Diplodocidae


Template: Klade / Maintenance / 3

  Macronaria , Camarasauromorpha  

 Camarasaurus


  Titanosauriformes  

 Brachiosaurus


   

 Titanosauria





Template: Klade / Maintenance / 3

   

Vulcanodon



History of discovery and research

Early discoveries in England

The first scientifically studied sauropod bones were discovered in England. As early as 1825, John Kingston reported fragmentary leg bones from the Middle Jurassic, and other giant bones from Jurassic rocks were discovered within the next 16 years. The later first describer of the Dinosauria Richard Owen , unwittingly gave the first sauropod fossil a scientific name; he named a tooth Cardiodon , although he did not know which animal it belonged to.

In his study on fossil reptiles from England, published in 1842, Owen described, among other things, the giant bones found so far and later placed among the sauropods. He said they belonged to a large animal and could not be assigned to any known shape, but that the whales had a spongy bone structure. Based on this finding, he named the unknown animal Cetiosaurus , which means something like "whale lizard". He assumed a large, marine crocodile . In 1860 Owen created a new suborder of the crocodiles, the Opisthocaudia, where he classified Cetiosaurus and Streptospondylus (later rewritten as Theropod ).

In the 30 years after the description of Cetiosaurus, various fragmentary finds were described ( e.g. Pelorosaurus and Aepisaurus ), but these are considered invalid or dubious. A first picture of the true nature of the sauropods could only be made after the discovery of a partially preserved, but skullless, Cetiosaurus skeleton. This was recovered in a quarry near Gibraltar near Oxford and described in detail in the book "The Geology of Oxford" by John Phillips , published in 1871 . Phillips suggested that the bones came from a large, land-dwelling dinosaur. He discovered that the legs could not stand as spread apart as with crocodiles, but stood straighter under the body. He also concluded for the first time from the only remaining tooth that it must be a herbivore .

Between 1870 and 1890 other important discoveries were made for an understanding of the anatomy of sauropods; In 1877, the Indian Titanosaurus ( Lydekker ) was described as the first sauropod from a southern continent.

Discoveries in North America (Morrison Formation)

As early as 1856, two teeth from Maryland were described as an astrodon , the first record of a sauropod from North America. From 1877 a flood of new discoveries from the late Jurassic Morrison formation began. The two rivals ED Cope and OC Marsh described in their so-called " bone wars " a huge amount of material (especially from Garden Park, Morrison and Como Bluff ) with the aim of outbidding the others by all means. Although this competition led to a total of 142 new dinosaur species, the publications were often only very brief and in many cases the underlying material was largely not yet cleared from the surrounding rock. Not least, this led to many synonyms (double names for the same animal).

Othniel Charles Marsh , the first descriptor of the Sauropoda

The most significant contributions regarding sauropods at the time came from Marsh. In 1878 he established the group Sauropoda and described ten features that characterize the new taxon. In 1879 he described a partially preserved skull for the first time and named the animal "Morosaurus" ("stupid lizard") because of the tiny size of the skull compared to the rest of the body. Morosaurus was later recognized as a synonym with the Camarasaurus described by Cope ; as the latter was described before Morosaurus , Camarasaurus is the name valid today. In 1883 Marsh described an almost complete skeleton as "Brontosaurus" excelsus and published a complete reconstruction for the first time. However, Brontosaurus was later recognized as a synonym with Apatosaurus (Marsh, 1877), which is why Brontosaurus is now considered invalid. In 1884 Marsh described the genus Diplodocus and with it the first complete, connected sauropod skull.

At the turn of the century there were significant discoveries from Como Bluff and the nearby Bone Cabin Quarry , two Wyoming dinosaur cemeteries . Hundreds of finds have been made from Bone Cabin Quarry alone, including many connected limb bones from sauropods. The findings led, among other things, to detailed descriptions of Diplodocus (Hatcher, 1901), Apatosaurus (Hatcher, 1902) and Haplocanthosaurus (Hatcher, 1903). Casts of a Diplodocus skeleton have been sent to museums around the world.

Earl Douglass discovered the largest site for sauropod bones in 1909, the Dinosaur National Monument in Utah . Here nine complete or almost complete sauropod skulls of Camarasaurus , Diplodocus and Apatosaurus came to light, as well as five skeletons. The rare genus Barosaurus is also among the finds.

Discoveries from the Tendaguru and Shaximiao Formations

Dicraeosaurus in the Berlin Natural History Museum

At the beginning of the twentieth century, another, now familiar, sauropod fauna was discovered in the former German province of East Africa (today's Tanzania ) - the fauna of the late Jurassic Tendaguru formation. A German expedition unearthed fossils that were described by E. Fraas in 1908 and are now known as Tornieria and Janenschia . Further excavations under the direction of Werner Janensch brought to light a large number of bones, which were later described by Janensch from 1914 to 1961. The majority of these bones are now in the Humboldt Museum für Naturkunde in Berlin, including Brachiosaurus and Dicraeosaurus .

From the 1920s and 1930s there were detailed publications on Camarasaurus (Osborn and Mook, 1921) - an almost complete sauropod skeleton was described for the first time (Gilmore, 1925) - and on Apatosaurus (Gilmore, 1936). Other publications include a comprehensive description of the Chinese Euhelopus (Wiman, 1929) and descriptions of the Argentine and Indian titanosaurs ( Huene and Matley, 1933).

From the end of the Second World War there was a series of publications by the legendary Chinese researcher CC Young on the rich fossil deposits from the Middle and Late Jurassic of China. In 1972 Mamenchisaurus from Sichuan was described as having a neck that is remarkably long in relation to its body. Other species come from the upper Shaximiao Formation , which today, together with the North American Morrison Formation and the East African Tendaguru Formation, is one of the best-known sauropod faunas - among the finds are Shunosaurus , Datousaurus and Omeisaurus . Today, China has gained great importance in the study of sauropods due to its many fragmentary and complete skeletons. Notable finds have also been made from other areas of Asia, especially the Gobi Desert , including Nemegtosaurus , Quaesitosaurus, and Opisthocoelicaudia .

Recent discoveries

Live reconstruction of Paralititan

Besides China, Argentina is the region from which most of the new sauropod finds come today. Notable finds from the middle Jurassic to the late Cretaceous include Patagosaurus , Saltasaurus , and from the more recent past Rayososaurus , Amargasaurus , Andesaurus and Argentinosaurus . Other finds come from the Sahara of North Africa, such as Nigersaurus and Jobaria .

Significant recent discoveries include the titanosaur Rapetosaurus (2001) from Madagascar and the small europeansaurus (2006) from Germany. Other important finds from the recent past include the primitive Spinophorosaurus (2009) and the titanosaurs Futalognkosaurus (2007) and Tapuiasaurus (2011).

literature

Web links

Commons : Sauropods  - Collection of images, videos and audio files

Individual evidence

  1. ^ Gregory S. Paul : The Princeton Field Guide To Dinosaurs. Princeton University Press, Princeton NJ et al. 2010, ISBN 978-0-691-13720-9 , pp. 171-213, online .
  2. ↑ a b c Ignacio A. Cerda, Ariana Paulina Carabajal, Leonardo Salgado , Rodolfo A. Coria , Marcelo A. Reguero, Claudia P. Tambussi, Juan J. Moly: The first record of a sauropod dinosaur from Antarctica. In: Natural Sciences . Vol. 99, No. 1, 2012, pp. 83-87, doi : 10.1007 / s00114-011-0869-x .
  3. ↑ a b c d e f g h i j k l m n Paul Upchurch , Paul M. Barrett , Peter Dodson : Sauropoda. Section: Anatomy. In: David B. Weishampel , Peter Dodson, Halszka Osmólska (eds.): The Dinosauria. 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 273-295.
  4. ↑ a b c P. Martin Sander , Octávio Mateus, Thomas Laven, Nils Knötschke: Bone histology indicates insular dwarfism in a new Late Jurassic sauropod dinosaur. In: Nature . Vol. 441, No. 7094, 2006, pp. 739–741, doi : 10.1038 / nature04633 , digitized version (PDF; 264.58 kB) ( Memento from July 7, 2006 in the Internet Archive ).
  5. ^ A b Gerardo V. Mazzetta, Per Christiansen, Richard A. Fariña: Giants and Bizarres: Body Size of Some Southern South American Cretaceous Dinosaurs. In: Historical Biology. Vol. 16, No. 2/4, 2004, ISSN  0891-2963 , pp. 71-83, doi : 10.1080 / 08912960410001715132 , digital version (PDF; 574.66 kB) .
  6. ^ A b John S. McIntosh, Michael K. Brett-Surman, James O. Farlow: Sauropods. In: James O. Farlow, Michael K. Brett-Surman (Eds.): The Complete Dinosaur. Indiana University Press, Bloomington IN et al. 1997, ISBN 0-253-33349-0 , pp. 269-271.
  7. ^ Daniel Chure, Brooks B. Britt, John A. Whitlock, Jeffrey A. Wilson: First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition. In: Natural Sciences. Vol. 97, No. 4, 2010, pp. 379-391, doi : 10.1007 / s00114-010-0650-6 .
  8. ↑ a b c d e f g h i j k John S. McIntosh, Michael K. Brett-Surman, James O. Farlow: Sauropods. Section: Sauropod Anatomy. In: James O. Farlow, Michael K. Brett-Surman (Eds.): The Complete Dinosaur. Indiana University Press, Bloomington IN et al. 1997, ISBN 0-253-33349-0 , pp. 269-271.
  9. ↑ Sebastián Apesteguía: Evolution of the Hyposphene-Hypantrum Complex within Sauropoda. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 248-267.
  10. ↑ a b c d e f g Jeffrey A. Wilson: Overview of Sauropod Phylogeny and Evolution. Kristina Curry Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. a 2005, ISBN 0-520-24623-3 , pp. 15-49, digitized version (PDF; 384.37 kB) .
  11. ^ Daniel T. Ksepka, Mark A. Norell : Erketu ellisoni, a Long-Necked Sauropod from Bor Guvé (Dornogov Aimag, Mongolia) (= American Museum Novitates. No. 3508, ISSN  0003-0082 ). American Museum of Natural History, New York NY 2006, digitized version (PDF; 2.02 MB) .
  12. ↑ a b c Michael D. D'Emic, Jeffrey A. Wilson, Sankar Chatterjee : The titanosaur (Dinosauria: Sauropoda) osteoderm record: review and first definitive specimen from India. In: Journal of Vertebrate Paleontology. Vol. 29, No. 1, 2009, ISSN  0272-4634 , pp. 165-177, doi : 10.1671 / 039.029.0131 .
  13. ↑ Leonardo Salgado: Considerations on the bony plates assigned to titanosaurs (Dinosauria, Sauropoda). In: Ameghiniana . Vol. 40, No. 3, 2003, pp. 441-456, abstract .
  14. ↑ Jeffrey A. Wilson, Dhananjay M. Mohabey, Shanan E. Peters, Jason J. Head: Predation upon Hatchling Dinosaurs by a New Snake from the Late Cretaceous of India. In: PLoS Biol . Vol. 8, No. 3, 2010, e1000322, doi : 10.1371 / journal.pbio.1000322 .
  15. ↑ Thiago da Silva Marinho: Functional aspects of titanosaur osteoderms. In: Nature Precedings. 2007, ZDB -ID 2637018-9 , doi : 10.1038 / npre.2007.508.1 .
  16. Jump up ↑ a b P. Martin Sander, Andreas Christian, Marcus Clauss, Regina Fechner, Carole T. Gee, Eva-Maria Griebeler, Hanns-Christian Gunga , Jürgen Hummel, Heinrich Mallison, Steven F. Perry, Holger Preuschoft, Oliver WM Rauhut , Kristian Remes, Thomas Tütken, Oliver Wings, Ulrich Witzel: Biology of the sauropod dinosaurs: the evolution of gigantism. In: Biological Reviews. Vol. 86, No. 1, 2011, ISSN  1464-7931 , pp. 117–155, doi : 10.1111 / j.1469-185X.2010.00137.x , digital version (PDF; 1.25 MB) .
  17. ↑ Olga del Valle Giménez: Skin impressions of Tehuelchesaurus (Sauropoda) from the Upper Jurassic of Patagonia. In: Revista del Museo Argentino de Ciencias Naturales. NS Vol. 9, No. 2, 2007, ISSN  1514-5158 , pp. 119–124, digitized version (PDF; 466.55 kB) ( Memento of the original from October 7, 2012 in the Internet Archive ) Info: The archive link became automatic used and not yet tested. Please check the original and archive link according to the instructions and then remove this notice. . @1@ 2Template: Webachiv / IABot / www.macn.secyt.gov.ar
  18. ↑ Stephen Czerkas: The history and interpretation of sauropod skin impressions. In: Martin G. Lockley, Vanda F. dos Santos, Christian A. Meyer, Adrian P. Hunt (eds.): Aspects of sauropod paleobiology (= Gaia. Revista de Geociências. No. 10, ISSN  0871-5424 ). Museu Nacional de História Natural, Lisboa 1994, digital version (PDF; 2.96 MB) .
  19. ↑ a b c d e f g h i j k l m n o p q r s Paul Upchurch, Paul M. Barrett, Peter Dodson: Sauropoda. Section: Paleobiology, Taphonomy, and Paleoecology. In: David B. Weishampel, Peter Dodson, Halszka Osmólska (eds.): The Dinosauria. 2nd edition. University of California Press, Berkeley CA et al. 2004, ISBN 0-520-24209-2 , pp. 273-295.
  20. ↑ a b c d e f g Kenneth Carpenter: Biggest of the big: a critical re-evaluation of the mega-sauropod Amphicoelias fragillimus Cope, 1878. In: John R. Foster, Spencer G. Lucas (eds.): Paleontology and Geology of the Upper Jurassic Morrison Formation (= New Mexico Museum of Natural History & Science. Bulletin. 36, ISSN  1524-4156 ). New Mexico Museum of Natural History & Science, Albuquerque NM 2006, pp. 131-138, online .
  21. ↑ a b c d e Kent Stevens, Michael Parrish: Neck Posture, Dentition, and Feeding Strategies in Jurassic Sauropod Dinosaurs. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 212-232.
  22. ^ Vandana Prasad, Caroline AE Strömberg, Habib Alimohammadian, Ashok Sahni: Dinosaur Coprolites and the Early Evolution of Grasses and Grazers. In: Science . Vol. 310, no. 5751, 2005, pp. 1177-1180, doi : 10.1126 / science.1118806 .
  23. ^ Paul M. Barrett, Emily J. Rayfield: Ecological and evolutionary implications of dinosaur feeding behavior. In: Trends in Ecology & Evolution. Vol. 21, No. 4, 2006, ISSN  0169-5347 , pp. 217-224, doi : 10.1016 / j.tree.2006.01.002 .
  24. ↑ a b Sankar Chatterjee, Zhong Zheng: Neuroanatomy and Dentition of 'Camarasaurus lentus'. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 199-211.
  25. ^ Paul C. Sereno , Jeffrey A. Wilson, Lawrence M. Witmer, John A. Whitlock, Abdoulaye Maga, Oumarou Ide, Timothy A. Rowe: Structural Extremes in a Cretaceous Dinosaur. In: PLOS ONE . Vol. 2, No. 11, 2007, e1230, doi : 10.1371 / journal.pone.0001230 .
  26. ↑ David Berman, Bruce Rothschild: Neck Posture of Sauropods Determined Using Radiological Imaging to Reveal Three-Dimensional Structure of Cervical Vertebrae. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 233-247.
  27. ↑ a b Kent A. Stevens, J. Michael Parrish: Neck Posture and Feeding Habits of Two Jurassic Sauropod Dinosaurs. In: Science. Vol. 284, No. 5415, 1999, pp. 798-800, doi : 10.1126 / science.284.5415.798 .
  28. ↑ Oliver Wings: A review of gastrolith function with implications for fossil vertebrates and a revised classification. In: Acta Palaeontologica Polonica. Vol. 52, No. 1, 2007, ISSN  0567-7920 , pp. 1-16, online .
  29. ↑ O. Wings, PM Sander: No gastric mill in sauropod dinosaurs: new evidence from analysis of gastrolith mass and function in ostriches. In: Proceedings. Biological sciences / The Royal Society. Volume 274, number 1610, March 2007, pp. 635-640, doi : 10.1098 / rspb.2006.3763 , PMID 17254987 , PMC 2197205 (free full text).
  30. ^ A b Jeffrey A. Wilson, Kristina Curry Rogers: Monoliths of the Mesozoic. In: Kristina Curry A. Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. 2005, ISBN 0-520-24623-3 , pp. 1-14, digitized version (PDF; 175.70 kB) .
  31. ↑ a b c Mathew J. Wedel, Richard L. Cifelli: Sauroposeidon: Oklahoma's Native Giant (= Oklahoma Geology Notes. Vol. 65, No. 2, ISSN  0030-1736 ). Oklahoma Geological Survey, Norman OK 2005, digitized version (PDF; 2.15 MB) .
  32. ↑ David M. Lovelance, Scott A. Hartman, William R. Wahl: Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of Diplodocoid phylogeny. In: Arquivos do Museu Nacional. Vol. 65, No. 4, 2007, ISSN  0365-4508 , pp. 527-544, digitized version (PDF; 1.9 MB) ( Memento of the original from August 22, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. . @1@ 2Template: Webachiv / IABot / www.publicacao.museunacional.ufrj.br
  33. ↑ Spencer G. Lucas, Matthew C. Herne, Andrew B. Heckert, Adrian P. Hunt, Robert M. Sullivan: Reappraisal of Seismosaurus, A Late Jurassic Sauropod Dinosaur from New Mexico In: The Geological Society of America. Abstracts with Programs. Vol. 36, No. 5, 2004, ISSN  0016-7592 , p. 422.
  34. ↑ Oliver Rauhut: 40 m long and 100 t heavy. The gigantism of the sauropod dinosaurs. In: fossils. Vol. 22, No. 4, 2005, ISSN  0175-5021 , pp. 208-213, online .
  35. ↑ a b c d Mathew J. Wedel: Vertebral pneumaticity, air sacs, and the physiology of sauropod dinosaurs. In: Paleobiology. Vol. 29, No. 2, 2003, ISSN  0094-8373 , pp. 243-255, doi : 10.1666 / 0094-8373 (2003) 029 <0243: VPASAT> 2.0.CO; 2 , digitized version (PDF; 860.30 kB) ( Memento from December 17, 2008 in the Internet Archive ).
  36. ^ Daniela Schwarz, Eberhard Frey, Christian A. Meyer: Pneumaticity and soft-tissue reconstructions in the neck of diplodocid and dicraeosaurid sauropods. In: Acta Palaeontologica Polonica. Vol. 52, No. 1, 2007, pp. 167-188 ( online ).
  37. ↑ a b Bruce Rotschild, Ralph Molnar: Sauropod Stress Fractures as Clues to Activity. In: Virginia Tidwell, Kenneth Carpenter (Eds.): Thunder-lizards. The Sauropodomorph Dinosaurs. Indiana University Press, Bloomington IN et al. 2005, ISBN 0-253-34542-1 , pp. 381-392.
  38. ↑ Jeffrey A. Wilson, Matthew T. Carrano: Titanosaurs and the Origin of "Wide-Gauge" Trackways: A Biomechanical and Systematic Perspective on Sauropod Locomotion. In: Paleobiology. Vol. 25, No. 2, 1999, pp. 252-267.
  39. ^ Martin Lockley, Christian Meyer: Dinosaur Tracks and other fossil footprints of Europe. Columbia University Press, New York et al. 2000, ISBN 0-231-10710-2 , p. 164.
  40. ^ A b Martin G. Lockley: A guide to the fossil footprints of the world. University of Colorado et al., Denver CO et al. 2002, ISBN 0-9706091-3-2 .
  41. ^ Eric Buffetaut , Jean Le Loeuff: The discovery of dinosaur eggshells in nineteenth-century France. In: Kenneth Carpenter, Karl F. Hirsch, John R. Horner (Eds.): Dinosaur Eggs and Babies. Cambridge University Press, Cambridge 1994, ISBN 0-521-44342-3 , pp. 31-34.
  42. ↑ Brooks B. Britt, Bruce G. Naylor: An embryonic 'Camarasaurus' (Dinosauria, Sauropoda) from the Upper Jurassic Morrison Formation (Dry Mesa Quarry, Colorado). In: Kenneth Carpenter, Karl F. Hirsch, John R. Horner (Eds.): Dinosaur Eggs and Babies. Cambridge University Press, Cambridge 1994, ISBN 0-521-44342-3 , pp. 256-264.
  43. ↑ Bernat Vila, Frankie D. Jackson, Josep Fortuny, Albert G. Sellés, Àngel Galobart: 3-D Modeling of Megaloolithid Clutches: Insights about Nest Construction and Dinosaur Behavior. In: PLoS ONE. Vol. 5, No. 5, 2010, e10362, doi : 10.1371 / journal.pone.0010362 .
  44. ↑ Gerald Grellet-Tinner, Luis M. Chiappe , Rodolfo Coria : Eggs of titanosaurid sauropods from the Upper Cretaceous of Auca Mahuevo (Argentina). In: Canadian Journal of Earth Sciences. Vol. 41, No. 8, 2004, ISSN  0008-4077 , pp. 949-960, doi : 10.1139 / e04-049 .
  45. ↑ a b Kristina Curry Rogers, Gregory M. Erickson: Sauropod Histology: microscopic views on the lives of giants. In: Kristina Curry A. Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. 2005, ISBN 0-520-24623-3 , pp. 303-326, doi : 10.1525 / california / 9780520246232.003.0012 .
  46. ↑ a b Luis M. Chiappe, Frankie Jackson, Rodolfo A. Coria, Lowell Dingus: Nesting Titanosaurs from Auca Mahuevo and Adjacent Sites: Understanding Sauropod Reproductive Behavior and Embryonic Development. In: Kristina Curry A. Rogers, Jeffrey A. Wilson (Eds.): The Sauropods. Evolution and Paleobiology. University of California Press, Berkeley CA et al. 2005, ISBN 0-520-24623-3 , pp. 285-302, doi : 10.1525 / california / 9780520246232.003.0011 .
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  66. ↑ Kristian Remes, Francisco Ortega, Ignacio Fierro, Ulrich Joger , Ralf Kosma, José Manuel Marín Ferrer: A new basal sauropod dinosaur from the Middle Jurassic of Niger and the early evolution of sauropoda. In: PLoS ONE. Vol. 4, No. 9, 2009, e6924, doi : 10.1371 / journal.pone.0006924 .
  67. ↑ Jorge O. Calvo , Juan D. Porfiri, Bernardo J. Gonzáles-Riga, Alexander WA Kellner: A new Cretaceous terrestrial ecosystem from Gondwana with the description of a new sauropod dinosaur. In: Anais da Academia Brasileira de Ciências. Vol. 79, No. 3, 2007, ISSN  0001-3765 , pp. 529-541, digital version (PDF; 836.43 kB) .
  68. ↑ Hussam Zaher, Diego Pol, Alberto B. Carvalho, Paulo M. Nascimento, Claudio Riccomini, Peter Larson, Rubén Juarez-Valieri, Ricardo Pires-Domingues, Nelson Jorge da Silva Jr., Diógenes de Almeida Campos: A Complete Skull of an Early Cretaceous Sauropod and the Evolution of Advanced Titanosaurians. In: PLoS ONE. Vol. 6, No. 2, 2011, e16663, doi : 10.1371 / journal.pone.0016663 .
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