Gastornis

Gastornis

• Europe
• North America ( " Diatryma " )

Gastornis is a now extinct species of large, flightless birds that is more closely related to geese birds. She was from the Middle Paleocene to the Middle Eocene, 62-41 million years ago, both in contemporary Europe and North America spread. The first fossils of the genus Gastornis were discovered in 1855 near Paris. The oldest North American findings date back to 1876 and were originally assigned to the genus Diatryma. For a long time, both genera were considered independently, what part of a faulty reconstruction from the end of the 19th century was responsible. It was not until the early 1990s it was recognized that Diatryma and Gastornis them are closely related, new bone finds from France eventually led to synonymisation of Diatryma with Gastornis.

Because the physique Gastornis is considered a rather slowly moving, soil-inhabiting birds. The diet is not completely understood. On one hand, it is often assumed by the large skull and the beak a specialization in Animal Nutrition, in conjunction with its size Gastornis could thus represent a Spitzenprädator his time. On the other hand, a purely vegetarian diet is believed that results in part from the size of the animal and the construction of the beak. Investigations from 2013 seem to confirm the view of specialization in plant food.

• 2.1 Fossil Finds
• 2.2 soft tissues, eggs, and trace fossils

• 3.1 diet
• 3.2 locomotion

Features

Habit

Gastornis was a very large and sturdy built, flightless bird, which reached a peak height of 1.75 to about 2 m. This European representatives were on average slightly smaller than North American. The body weight was estimated to be 100-175 kg which he is one of the largest and heaviest known birds. Special features of the representatives of Gastornis put the big head is with a powerful beak, the short but strong neck and the massive legs, the lower sections were designed rather short. As with today's large ratites reported the wings in length to severely reduced bone mineral.

Skull and beak

The skull was very large, and measured with a full copy of 43 cm, the powerful beak took from a 23 cm. This was also very high, 16.5 cm, and the sides strongly narrowed. The top beak had a clearly convex curvature, while the tip of the beak was not extended like a hook. Especially by the latter feature, Gastornis significantly from similarly built Phorusrhacidae ( " terror birds " ) is different. The external nares were about 5 cm in front of the orbit and near the lower edge of the beak. They were small and directed forward. Again, there are differences to the Phorusrhaciden, begin their nostrils often right on the eyepiece. The orbit itself was surrounded by a strong and prominent raised ridge. The typical square leg for birds distinguished by its size, but overall was rather short and stocky. The zygomatic arches also had a short building and ran into an S-curve. The entire -faceted behind the eyes windows rear skull had only a small extent in contrast to the massive beak.

The lower jaw was massive and the bone body with up to 10 cm high. He had a strong symphysis, which reached some 18 cm in length and as nearly half of the total length of the mandible occupied, which is unusual for birds. She combined the two, almost straight-running, mandibles together and ended up in front with a narrow tip.

Body skeleton

The spine is not fully known, in general, the eddy recorded but by their Robustizität and their short vertebral bodies. The neck was composed of 13 or 14 vertebrae. On the back there were seven rib-bearing vertebrae. The ribs were bent there ansetztenden thin and wide. The tail consisted of ten or more vertebrae. The forelimbs were much atrophied. Typical of flightless birds was the obtuse angle between scapula and coracoid, which reached 180 °, similar to the two-legged running dinosaurs with short forelimbs, but in contrast to the flying birds, in which the angle is less than 90 °. The hind legs, however, were formed extremely strong. The femur reached about 38 cm in length and was at the lower joint end a good 10 inches wide. The tibiotarsus measured almost 60 cm and had a straight shaft on. The fibula had a very graceful contrast. With approximately 25 cm in length is very short and rather wide of the tarsometatarsus was designed. The legs ended in four-rayed feet, of which three beams (up to IV II) jutted forward and one ( I) was backwards. Of the three forward-facing toes possessed the middle ( III) the greatest length, which is different from the equally giant moa with three equal length beams. The shortest beam was the rear-facing. The phalanges exhibited only a short form and a triangular cross -section. In the longitudinal view, they were only slightly curved, which in turn differs from the Phorusrhaciden.

Biogeography

Fossil finds

Gastornis is detected both in Europe and in North America. The European finds dated to the period from the Middle Paleocene to the Middle Eocene, 62 to about 41 million years ago. Among the oldest evidence includes the scant remains of Walbeck in Western Saxony -Anhalt, under which there is a 7 cm long coracoid among others. The most extensive finds of the continent are known in the Geisel. They include more than three dozen found objects, including mostly remnants of the walking legs and pelvis, as well as wing bones and parts of the skull. You can be a total of nine individuals assigned and spread over the lower coal to the upper middle carbon of the site, thus dating to the Middle Eocene. The same age is a singular treasure in the form of an approximately 30 cm long femur from the Messel Pit in Hesse, who was in a rock tuber. He had already been found in the early 20th century during the mining operation, but could be assigned safely only in the 1960s. In contrast, numerous remains are from Mont de Berru at Reims in the Paris basin in turn known. They are slightly younger than those of Walbeck and represent, among other things, numerous walking leg rests. Among the southern European radicals further some leg bone from Saint- Papoul in the Aude department in southern France are expected. In addition, fossils of Gastornis found in London and Belgium.

The well-known North American finds are set all of the Lower Eocene and distributed to over 50 sites. These is one of the few complete skeletons, which is reconstructed up to 2.1 m high. This comes from the Bighorn Basin in Wyoming. It was already the beginning of the 20th century discovered and is the result of numerous previous, more profound studies in which previously some leg and foot bones had come to light. For the same basin comes from the Willwood Formation a larger collection, which also includes skull and leg rests and eddy finds. Other discoveries were beyond in New Mexico to the fore. Here is primarily a tarsometatarsus of importance that led to the formation of the genus Diatryma in 1876. A few bones could also be described from the untereozänen Margaret Formation on Ellesmere Iceland in the Arctic north of Canada. These represent the northernmost known finds of Gastornis ever dar. Despite the small size of the fossil remains of Ellesmere Iceland comes to this key position. The higher age of some sites of Gastornis in Europe indicated that the genus originated there and had later spread over an Arctic land bridge to North America.

Soft tissues, eggs, and trace fossils

In addition to fossil bone remains only a few remnants of the soft tissue are known. Already in the 1920s spring finds were described by the Loan Creek in the western U.S. state of Colorado that were a good 20 inches long and came from the Green River Formation. This turned out upon further examination as residues of plant fibers. Actual springs in the form of, among others, a 24 -cm-long specimen, on the other hand came in the Fossil Butte Member, also the Green River Formation belonging to days. But as more fossil remains are missing, they can be assigned Gastornis limited due to their size.

From Provence and Languedoc in the south-eastern and southern France numerous fragmented eggs were in deposits of the Upper Paleocene ( Thanetium ) and the Lower Eocene ( Sparnacium ) found whose discovery dates back to the 1950s. The eggshells were up to 3.1 mm thick. A few, some completely preserved eggs reached dimensions of 24 x 15 cm, so they are larger than those of the African ostrich (Struthio ) but smaller than that of the Madagascan elephant birds ( Aepyornis ). Some other eggs even had a diameter of up to 40 cm. Since the egg shells of different size and structure, they are interpreted as legacies of different bird species, since no further fossil material is to be assigned to Oogenus Ornitholithus, where Ornitholithus arcuatis is the larger type and could match Gastornis. The nearest locality with Gastornis residues located only a few dozen kilometers away with Saint- Papoul. However, it is quite possible that other early ratites such as the ostrich -like Palaeotis, the eggs could have placed.

Among the finds are also rare trace fossils. In the Chuckanut Formation in the northwestern part of the U.S. state of Washington sunken footprints of a large bird were with three forward-facing toes found in untereozänen sandstone layers. The largest seal have lengths of 28.5 and latitude of 24.5 cm. Due to the size of the footprints Gastornis can be regarded as the cause. Since no other fossils are present, but they are assigned to the Ichnospezies Rivavipes giganteus. They had previously reported from the King County of the same state over a similar but unique track that belongs to the Middle to Upper Eocene, and thus is outside the temporal range of Gastornis in North America. Today, this track is regarded as a pseudo fossil. Also from Europe, from the region around Paris, fossil traces of great birds were known and associated with Gastornis. However, these belong to the Upper Eocene, for which there is no proof of these bird species in Europe.

Paleobiology

Diet

The diet of Gastornis was and is the subject of scientific controversy. Very early on included scientists from the mighty and very powerful beak that it must have probably traded in Gastornis a carnivore. This evolved convergently to the South American, now also extinct Phorusrhacidae ( " terror birds " ), in which we find among others a similar nature beak. Both lines originated consequently independently after the extinction of the dinosaurs 65 million years ago and occupied by the vacant niche of large carnivores. Investigations on the biomechanics of the mandible in conjunction with the massive symphysis and the mighty maxilla showed that the beak and the jaw joints were designed to develop a high bite force, especially in the rear part of the beak. The symphysis held large, both transversely and vertically acting loads were. The resulting force, was calculated, was enough to crack any known nut. For a purely plant-based diet, the beak was therefore fitted as to well regarded, even if it is similar to those of parrots and other seed and nut eaters under construction. He served on this view thus the prey, the Mangle of carrion and the breaking of bones or of crustaceans. As a food source thus served smaller mammals such as the Propalaeotherium frequent among others in the Geisel, but also small reptiles and molluscs. It seemed Gastornis when catching prey as a strong "bush breaker". As Spitzenprädator his time Gastornis competed only with the large, mostly water -dwelling crocodiles.

As an alternative scenario, a predominantly plant-based diet has already been approved in the 1970s, this view in the early 1990s gave new momentum. It has been argued that the upper beak lacks the typical birds of prey hooked end. The feet did not have the characteristic bird of prey claws, which are also detected in the Phorusrhacidae ( " terror birds " ) and its absence can be also obtained in the fossil, Gastornis assigned to observe footprints. According to this view, Gastornis nourished by numerous plants of the dense tropical rain forests, which he chewed with his beak or cut. As one in appearance and possibly in the diet to Gastornis analog bird genus still living Takahe ( Porphyrio ) is seen beyond. This now spread to New Zealand, flightless bird has a strong, high beak, a short neck, and also short leg bones, but only has a maximum weight of 3 kg and is a relative of the Rails. A survey conducted in 2013, analysis of calcium isotopes in fossil bones of Gastornis - finds from the Geisel gave similar isotopic ratios as in herbivorous mammals, which in turn differed from those clearly of carnivorous mammals and just as nourishing dinosaurs such as Tyrannosaurus. This now makes it more likely that the members of the genus Gastornis were herbivores. A completely plant-based diet is not well known in today's flying birds, since the energy required for the flight must be provided directly from the diet. For large ratites such a diet happens, however. Since leaves are a rather low-energy diet, and is well digested long Gastornis must have spent a lot of time with the food. The switch to plant food in Gastornis could be explained by the enormous body size increase.

Locomotion

The walking legs are constructed similar to that of today's African ostrich (Struthio ). As with this, much of the muscle mass of the legs also focuses on Gastornis directly beneath the body, which is confirmed by the rather short and very compact femur. Thus, the legs act like a pendulum under the hull and allow locomotion. As a fast runner the ostrich has a long and slender tarsometatarsus and two forwardly projecting rays toes on the feet. Other today live ratites, including cassowaries ( Casuarus ) and rheas ( Rhea ), have also next to a long tarsometatarsus about feet with three forward pointing beams. This reduction in the number of toes rays compared to four in many flying birds is a functional adaptation to the fast running in open landscapes and reduces the frictional resistance with the ground. Gastornis other hand, has a comparatively short and broad tarsometatarsus. The walking legs also ends in four-jet feet, one of which shows a ray backwards ( anisodactyl ). This combination of features is considered to be very earthy, even in comparison to other extant ratites. Due to the short Fußknochens and the rear-facing fourth toe a low running speed is reconstructed for Gastornis. Since the vast habitat of the bird genus dense tropical and subtropical rain forest represents a slow running gear is assumed that may have been interrupted by brief faster gaits. The little curved claws of the feet represent an adaptation to stronger ground activities and walking slowly and are less suitable for a quick hunt for prey. Whether the short rear toe supported functionally the foot during locomotion, is unclear. The footprints of the Chuckanut Formation have no rear, fourth toe impression, so this toe could have been potentially greatly reduced.

System

Phorusrhacidae

Gallinaceous birds ( Galliformes )

Gastornithidae ( Gastornis and Zhongyuanus )

Brontornithidae ( Brontornis et al )

Dromornithidae

Anatidae i.w.S. ( Anatoidea )

Spaltfußgänse ( Anseranatidae )

Screamers ( Anhimidae )

Gastornis is a genus of the family of Gastornithidae. These represent large ratites, which are characterized by a strong, laterally narrowed beak, a convex curved top ( culmen ), which in contrast to the similar built Phorusrhacidae but does not have a hook-like tip. Closely related to Gastornis is proven from East Asia Zhongyuanus, which was described in 1980 based on a tibiotarsus from untereozänen deposits in the Chinese province of Henan. The origin of the Gastornithidae is not fully understood. Maybe they can be derived from large ratites from the Upper Cretaceous, as they were first detected with Gargantuavis, based on a 6.5 cm long Synsacrums from near Fox Amphous in the French department of Var in Provence for this time period. Further finds, a pool, and a femur and several vertebrae, also come from the south of France. These fossil remains have an approximately ostrich large bird out of possibly weighing up to 140 kg, and have similarities to those of Gastornis. Based on the characteristics of the limb bones and the jaw joint but it is clear that Gastornis and its summarized in the order Gastornithiformes relatives with the geese birds ( Anseriformes ) and gallinaceous birds ( Galliformes ) are related. Today they form the sister group to the geese birds.

Throughout the history of research numerous species have been described from Gastornis recognized today are the following:

• G. geiselensis Fischer, 1976
• G. gigantaeus Cope, 1876
• G. parisiensis Hébert, 1855
• Russelli G. Martin, 1992
• Sarasini G. Schaub, 1929

G. ruselli represents the phylogenetically oldest and smallest species, reaching only half the size of a modern ostrich. It stands as a sister form over the other types of Gastornis. Other species such as G. steini, G. and G. edwardsi klaasseni described are no longer valid today. For North America, is partially also regens recognized for G. G. gigantaeus as an independent species, which differs slightly in the proportions of the phalanges. Other researchers hold for G. geiselensis synonymous with G. Sarasini, but this is only partially recognized. Generally, a new revision of the genus is called for.

Gastornis and Diatryma - The history of research a bird genus

The study of the genus Gastornis dates back to the mid-19th century. In 1855 the French physicist Gaston Plante discovered ( 1834-1889 ), who later invented the lead-acid battery in deposits of the Upper Paleocene and Lower Eocene, the " Conglomérat de Meudon ", in a suburb of Paris, the first bone of a giant bird that a femur and tibiotarsus included. These were duly described the same year by Edmond Hébert as the newly created genus Gastornis, which was then the oldest known bird species counted at all. The name Gastornis derives from the name it Plantes, Gaston, and the Greek name ὄρνις ( ornis ) for " bird". Only a short time later a few more finds came at Passy, also located near Paris, to the fore. The systematic position of Gastornis was completely unknown at that time. Hébert himself (1855 ) and Alphonse Milne -Edwards (1867 ) introduced the genus close to the ducks birds ( Anatidae ), Édouard Armand Lartet (1855 ) thought of a relationship with the Charadriiformes ( Charadriiformes ), Achille Valenciennes (1855 ) even saw similarities with albatrosses ( Diomedeidae ) and Charles Lucien Jules Laurent Bonaparte (1856 ) held Gastornis for a relative of the great, Malagasy running bird Aepyornis. Very extensive material was discovered after an interval of about 20 years in unterpaläozänen " Conglomérat de Cernay " at Reims, which was the oldest known fossil finding site of the Tertiary in Europe at that time. This archaeological material caused Victor Lemoine (1823-1911) in 1881 to make one skeleton reconstruction, but had diverged considerably and significantly gracefully from today known actual appearance of Gastornis. Lemoine had the inspiration for his reconstruction of recently discovered birds like Archaeopteryx or Hesperornis. The reconstruction was dominantly over the next few decades for the appearance of Gastornis. In the period that followed a few other finds were asked to Gastornis, the fossil remains of Croydon in England and Walbeck in Germany.

Described the basis of a large tarsometatarsus from the Eocene of the U.S. state of New Mexico Edward Drinker Cope (1840-1897) in 1876, the genus Diatryma, where the name to a bone shaft at the upper end penetrating the foramen, an opening in the bone, refers. While Cope saw similarities to the European Gastornis, but favored a separate genus name. However, in the aftermath poorly anatomical comparisons of the two bird species were possible as from North America only sparse fossil remains were known. A toe bone from New Jersey pointed Othniel Charles Marsh in 1894 Barornis, which was later united with Diatryma. The situation did not change until 1916, when a nearly complete skeleton was found in Wyoming, which described William Diller Matthew ( 1871-1930 ) and Walter Granger ( 1872-1941 ) in the following year peripherally. These skeletal reconstruction proved to be totally different from Lemoine, which was illustrated by the robust body and huge head. Therefore, many scientists both Gastornis and Diatryma certified a separate genus character. In the following years were also European discoveries, like the Geisel and the Messel Pit in Germany or from Lyon in France, an assignment to the genus Diatryma.

Until the late 1980s the two bird species have been assigned to different families, so Gastornis the Gastornithidae and Diatryma the Diatrymidae. The realization that Diatryma and Gastornis itself were substantially similar, grew only at the beginning of the 1990s. During a revision of the skeletal reconstruction of Lemoine and the inclusion of new material found in 1992 LD Martin realized that the reconstruction based only to a small extent on fossil remains of birds, namely only on a vortex and parts of the walking legs and some foot bones, by far the greater part, however, came from fish and reptiles, which the primitive form had been caused by Gastornis. Martin presented here also produces morphological similarities of Gastornis to Diatryma, referring both to the family Gastornithidae. Finds from Reims, an upper end of a tibiotarsus, which had not yet been described by Gastornis to the point of Diatryma but was already present on several occasions made ​​in 1997 raised the question of whether both classes are not identical. Only a few years later, in 2002, Gastornis and Diatryma were synonymized formal, which was confirmed in 2008 by the new discovery of another tibiotarsus from Saint- Papoul. Here, Eric Buffetaut had made ​​this discovery to the type species G. parisiensis, but at the same time noticed both similarities to comparable bones of G. geiselensis, which was originally described as Diatryma, as well as to similar finds from North America. The individual differences that exist are considered to be so small that Diatryma is now considered synonymous with Gastornis.