Gastornis
Encyclopedia
Gastornis is an extinct genus
of large flightless bird
that lived during the late Paleocene
and Eocene
epochs of the Cenozoic
. It was named in 1855, after Gaston Planté
, who had discovered the first fossils in Argile Plastique formation deposits at Meudon
near Paris
(France
). At that time, Planté (described as a "studious young man full of zeal") was at the start of his academic career, and his remarkable discovery was soon to be overshadowed by his subsequent achievements in physics
.
In the 1870s, the famous American paleontologist Edward Drinker Cope
discovered another, more complete set of fossils in North America
, and named them Diatryma (icon , from Ancient Greek
διάτρημα, diatrema, meaning "canoe").
The fossil remains of these birds have been found in western-central Europe (England
, Belgium
, France
and Germany
).
Gastornis parisiensis measured on average 1.75 metres (5.7 ft) tall, but large individuals grew up to 2 metres (6.6 ft) tall. The Gastornis had a remarkably huge beak
with a slightly hooked top, which was taken as evidence suggesting that it was carnivorous. Gastornis had large powerful legs, with large, taloned feet, which also were considered in support of the theory that it was a predator.
The plumage
of Gastornis is unknown; it is generally depicted with a hair-like covering as in ratite
s, but this is conjectural. Some fibrous strands recovered from a Green River Formation
deposit at Roan Creek, Colorado were initially believed to represent Gastornis feathers and named Diatryma filifera. Subsequent examination showed that they were actually not feathers at all but plant fibers or similar.
-like ornithuran, very different from the North American species. Eventually this was sorted out, and only then it was realized that Gastornis and Diatryma were so much alike to make many scientists today consider the latter a junior synonym of the former pending a comprehensive review. Consequently the correct scientific name is Gastornis. In fact, this similarity was recognized as early as 1884 by Elliott Coues
, but his reasoning was initially discounted and subsequently ignored until the late 20th century.
Gastornis were variously considered allied with diverse birds, such as waterfowl
, ratite
s or waders. Their highly apomorphic anatomy
makes reliable assignment to any one group of birds difficult, in particular since no particularly close relatives survive today. In modern times, they were placed with the "Gruiformes
" assemblage, which includes cranes. But in the 21st century, these birds are most often considered to be Galloanseres, or "fowls", in the same superorder as chickens and waterfowl. Quite ironically, the original assessment of Hébert - who perceived similarities with the Anseriformes
in the original tibia
- thus would be far more correct than any later placement. Incidentally, since the Galloanseres are known to originate in the Cretaceous
already, it is comfortably explained how such a gigantic bird could be around less than 10 million years after the non-avian dinosaur
s became extinct.
The following species
are accepted today:
At its time, the environment in which Gastornis lived had large portions of dense forest and a moist semiarid, subtropical or tropical climate. North America and Europe were still rather close, and especially since Greenland
was probably then covered with lush woodland and grassland, only narrow strait
s of a few 100 km would have blocked entirely landbound dispersal of the Gastornis ancestors. While there were large contiguous areas of land in their North American range after the Western Interior Seaway
had receded, their European range was an archipelago
due to the Alpide orogeny and the high sea level
s of the Paleocene-Eocene Thermal Maximum
; geographically (but not geologically), it was perhaps roughly similar to today's Indonesia
.
Classically, Gastornis has been depicted as predatory. However, with the size of Gastornis legs, the bird would have had to have been more agile to catch fast-moving prey than the fossils suggest it to have been. Consequently, it has been suspected that Gastornis was an ambush hunter and/or used pack hunting techniques to pursue or ambush prey; if Gastornis was a predator, it would have certainly needed some other means of hunting prey through the dense forest .
Alternatively, they may have been predominantly scavengers, omnivore
s or even herbivore
s. Indeed, the large beak of Gastornis would have been as well suited for crushing seeds and tearing off vegetation. But it seems excessively strong for a purely vegetarian diet, except in the rather improbable case that huge hard-shelled seeds and nut
s formed the main food item of Gastornis. Regardless of what these birds ate, the beak may simply have been used for social display though its presence in all known fossils argues against a sexual display role. These contradicting hypotheses, equivocally supported by the material evidence, make the dietary paleobiology of Gastornis impossible to pinpoint.
Similar gigantic birds of the Cenozoic were the South America
n terror birds (phorusrhacids) and the Australian mihirungs (Dromornithidae
). The former were certainly carnivorous, and the latter are suspected of being predators, too. On the other hand, ratite
s, the flightless giant birds of our time, feed on plants, small vertebrates, and invertebrate
s.
Gastornis were among the largest, if not the largest birds alive during the Paleogene
. They had few natural enemies and serious competitors apart from other Gastornis or then-rare large mammals, such as the predatory bear-like Arctocyon
of Europe. If these huge birds were active hunters, they must have been important apex predator
s that dominated the forest ecosystems of North America and Europe until the middle Eocene. The mid-Eocene saw the rise of large creodont and mesonychid
predators to ecological prominence in Eurasia and North America; the appearance of these new predators coincides with the decline of Gastornis and its relatives. This was possibly due to an increased tendency of mammalian predators to hunt together in packs (prevalent especially in hyaenodont
creodonts). The fact that no birds appear to have ever weighed much more than half a metric ton suggests that they were restricted in their ability to evolve to larger and larger sizes, and thus in their ability to out-evolve apex predators by sheer bulk as mammals are often able to do (see Cope's Rule
).
The fossil bones originally described as Omorhamphus storchii are the remains of a juvenile Gastornis giganteus. Specimen YPM PU
13258 from Early Eocene Willwood Formation rocks of Park County, Wyoming also seems to be a juvenile - perhaps of G. giganteus too, in which case it would be an even younger individual.
In Late Paleocene deposits of Spain
and Early Eocene deposits of France, shell fragments of huge eggs
have turned up, namely in the Provence
. These were described as the ichnotaxon
Ornitholithus and are presumably from Gastornis. While no direct association exists between Ornitholithus and Gastornis fossils, no other birds of sufficient size are known from that time and place: while the large Diogenornis
and Eremopezus
are known from the Eocene, the former lived in South America
(still separated from North America by the Tethys Ocean
then) and the latter is only known from the Late Eocene of North Africa, which also was separated by an (albeit less wide) stretch of the Tethys Ocean from Europe. The mid-Eocene ostrich
relative Palaeotis
from Europe, on the other hand, was a bustard
-sized bird, and the mysterious large Remiornis from France is only known from Paleocene
remains.
Some of these fragments were complete enough to reconstruct a size of 24 by 10 cm (about 9.5 by 4 inches) with shells 2.3-2.5 mm (0.09-0.1 in) thick, roughly half again as large as an ostrich egg and very different in shape from the more rounded ratite eggs. If Remiornis is indeed correctly identified as a ratite (which is quite doubtful however), Gastornis remains as the only known animal that could have laid these eggs. It is also notable that at least one species of Remiornis is known to have been smaller than the Gastornis, and was initially described as Gastornis minor by Mlíkovský in 2002. This would nicely match the remains of eggs a bit smaller than those of the living Ostrich which have also been found in Paleogene
deposits of Provence, were it not for the fact that these eggshell fossils also date from the Eocene but no Remiornis bones are known from that time yet.
There is no footprint record which is unequivocally known to be of Gastornis. This may be somewhat surprising, as there is an abundant record of fossilized bird and non-avian dinosaur tracks from the Cretaceous and Paleogene. But most of these are from shorelines or swamps, and thus the lack of Gastornis footprints might indicate that these birds stayed off soft ground, preferring terrain where they had better footing and consequently did not leave many trackways.
However, two mysterious footprint fossilizations are known that might be of Gastornis. One set of footprints was reported from Late Eocene gypsum
at Montmorency
and other locations of the Paris Basin
in the 19th century, from 1859 onwards. Described initially by Jules Desnoyers
and later on by Alphonse Milne-Edwards
, these ichnofossils were quite celebrated, and most French geologists of the late 19th century knew about them. They were discussed by Charles Lyell
in his Elements of Geology as an example of the incompleteness of the fossil record - no bones had been found associated with the footprints. Unfortunately, these fine specimens which sometimes preserved even details of the skin structure are now lost. They were brought to the Muséum national d'histoire naturelle
when Desnoyers started to work there, and the last documented record of them deals with their presence in the geology exhibition of the MNHN in 1912. The largest of these footprints, although only consisting of a single toe's impression, was a stunning 40 cm (16 in) long. Interestingly, the large footprints from the Paris Basin
could also be divided into huge and "merely" large examples, much like the eggshells from southern France which are 20 million years older.
The other footprint record consists of a single imprint which still exists, though it has proven to be even more controversial. It was found in Late Eocene Puget Group rocks in the Green River
valley near Black Diamond, Washington
. After its discovery, it raised considerable interest in the Seattle area in May–July 1992, being subject of at least two longer articles in the Seattle Times. Variously declared a hoax
or genuine, this apparent impression of a single bird foot measures about 27 cm wide by 32 cm long (11 by 13 in) and lacks a hallux
(hind toe); it was described as the ichnotaxon Ornithoformipes controversus. 14 years after the initial discovery, the debate about the find's authenticity was still unresolved. The specimen is now at Western Washington University
.
The problem with these trace fossils is that no fossil of Gastornis has been found to be younger than about 45 million years. The enigmatic "Diatryma" cotei is known from remains almost as old as the Paris basin footprints (whose date never could be accurately determined), but in North America the fossil record of unequivocal gastornithids seems to end even earlier than in Europe.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of large flightless bird
Flightless bird
Flightless birds are birds which lack the ability to fly, relying instead on their ability to run or swim. They are thought to have evolved from flying ancestors. There are about forty species in existence today, the best known being the ostrich, emu, cassowary, rhea, kiwi, and penguin...
that lived during the late Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
and Eocene
Eocene
The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
epochs of the Cenozoic
Cenozoic
The Cenozoic era is the current and most recent of the three Phanerozoic geological eras and covers the period from 65.5 mya to the present. The era began in the wake of the Cretaceous–Tertiary extinction event at the end of the Cretaceous that saw the demise of the last non-avian dinosaurs and...
. It was named in 1855, after Gaston Planté
Gaston Planté
Gaston Planté was the French physicist who invented the lead-acid battery in 1859. The lead-acid battery eventually became the first rechargeable electric battery marketed for commercial use.Planté was born on April 22, 1834, in Orthez, France...
, who had discovered the first fossils in Argile Plastique formation deposits at Meudon
Meudon
Meudon is a municipality in the southwestern suburbs of Paris, France. It is in the département of Hauts-de-Seine. It is located from the center of Paris.-Geography:...
near Paris
Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...
(France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
). At that time, Planté (described as a "studious young man full of zeal") was at the start of his academic career, and his remarkable discovery was soon to be overshadowed by his subsequent achievements in physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
.
In the 1870s, the famous American paleontologist Edward Drinker Cope
Edward Drinker Cope
Edward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
discovered another, more complete set of fossils in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
, and named them Diatryma (icon , from Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
διάτρημα, diatrema, meaning "canoe").
The fossil remains of these birds have been found in western-central Europe (England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, Belgium
Belgium
Belgium , officially the Kingdom of Belgium, is a federal state in Western Europe. It is a founding member of the European Union and hosts the EU's headquarters, and those of several other major international organisations such as NATO.Belgium is also a member of, or affiliated to, many...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
and Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
).
Description
Beak
The beak, bill or rostrum is an external anatomical structure of birds which is used for eating and for grooming, manipulating objects, killing prey, fighting, probing for food, courtship and feeding young...
with a slightly hooked top, which was taken as evidence suggesting that it was carnivorous. Gastornis had large powerful legs, with large, taloned feet, which also were considered in support of the theory that it was a predator.
The plumage
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
of Gastornis is unknown; it is generally depicted with a hair-like covering as in ratite
Ratite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
s, but this is conjectural. Some fibrous strands recovered from a Green River Formation
Green River Formation
The Green River Formation is an Eocene geologic formation that records the sedimentation in a group of intermountain lakes. The sediments are deposited in very fine layers, a dark layer during the growing season and a light-hue inorganic layer in winter. Each pair of layers is called a varve and...
deposit at Roan Creek, Colorado were initially believed to represent Gastornis feathers and named Diatryma filifera. Subsequent examination showed that they were actually not feathers at all but plant fibers or similar.
Taxonomy and systematics
The skull of Gastornis remained unknown except for nondescript fragments, and several bones assigned to it were those of other animals. Thus, the European bird was long reconstructed as a sort of gigantic craneCrane (bird)
Cranes are a family, Gruidae, of large, long-legged and long-necked birds in the order Gruiformes. There are fifteen species of crane in four genera. Unlike the similar-looking but unrelated herons, cranes fly with necks outstretched, not pulled back...
-like ornithuran, very different from the North American species. Eventually this was sorted out, and only then it was realized that Gastornis and Diatryma were so much alike to make many scientists today consider the latter a junior synonym of the former pending a comprehensive review. Consequently the correct scientific name is Gastornis. In fact, this similarity was recognized as early as 1884 by Elliott Coues
Elliott Coues
Elliott Coues was an American army surgeon, historian, ornithologist and author.Coues was born in Portsmouth, New Hampshire. He graduated at Columbian University, Washington, D.C., in 1861, and at the Medical school of that institution in 1863...
, but his reasoning was initially discounted and subsequently ignored until the late 20th century.
Gastornis were variously considered allied with diverse birds, such as waterfowl
Waterfowl
Waterfowl are certain wildfowl of the order Anseriformes, especially members of the family Anatidae, which includes ducks, geese, and swans....
, ratite
Ratite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
s or waders. Their highly apomorphic anatomy
Anatomy
Anatomy is a branch of biology and medicine that is the consideration of the structure of living things. It is a general term that includes human anatomy, animal anatomy , and plant anatomy...
makes reliable assignment to any one group of birds difficult, in particular since no particularly close relatives survive today. In modern times, they were placed with the "Gruiformes
Gruiformes
The Gruiformes are an order containing a considerable number of living and extinct bird families, with a widespread geographical diversity. Gruiform means "crane-like"....
" assemblage, which includes cranes. But in the 21st century, these birds are most often considered to be Galloanseres, or "fowls", in the same superorder as chickens and waterfowl. Quite ironically, the original assessment of Hébert - who perceived similarities with the Anseriformes
Anseriformes
The order Anseriformes contains about 150 living species of birds in three extant families: the Anhimidae , Anseranatidae , and the Anatidae, which includes over 140 species of waterfowl, among them the ducks, geese, and swans.All species in the order are highly adapted for an aquatic existence at...
in the original tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
- thus would be far more correct than any later placement. Incidentally, since the Galloanseres are known to originate in the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
already, it is comfortably explained how such a gigantic bird could be around less than 10 million years after the non-avian dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s became extinct.
The following species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
are accepted today:
- Gastornis parisiensis Hébert, 1855 - the type speciesType speciesIn biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
- Late Paleocene - Early Eocene of WC Europe
- Synonyms: Gastornis edwardsii Lemoine, 1878; G. klaasseni Newton, 1885; G. pariensis (lapsusLapsusA lapsus is an involuntary mistake made while writing or speaking. According to Freud's early psychoanalytic theory, a lapsus represents a missed deed that hides an unconscious desire....
)- Gastornis russeli L.MartinLarry MartinLarry Martin is an American vertebrate paleontologist and curator of the Natural History Museum and Biodiversity Research Center at the University of Kansas. Among Martin's work is research on the Triassic reptile Longisquama and theropod dinosaur Caudipteryx...
, 1992
- Gastornis russeli L.Martin
- Late Paleocene of Berru, France
- Gastornis sarasini (Schaub, 1929)
- Early Eocene - middle Eocene of WC Europe
- Gastornis giganteus CopeEdward Drinker CopeEdward Drinker Cope was an American paleontologist and comparative anatomist, as well as a noted herpetologist and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interested in science; he published his first scientific paper at the age of nineteen...
, 1876
- Gastornis giganteus Cope
- Early -? middle Eocene of SC North America
- Synonyms: Barornis regens MarshOthniel Charles MarshOthniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...
, 1894; Omorhamphus storchii Sinclair, 1928; O. storchi WetmoreAlexander WetmoreFrank Alexander Wetmore was an American ornithologist and avian paleontologist.-Life:Wetmore studied at the University of Kansas...
, 1931 (unjustified emendation) Omorhamphus storchii was described based on fossils from the Lower EoceneEoceneThe Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...
of WyomingWyomingWyoming is a state in the mountain region of the Western United States. The western two thirds of the state is covered mostly with the mountain ranges and rangelands in the foothills of the Eastern Rocky Mountains, while the eastern third of the state is high elevation prairie known as the High...
. The species was named in honor of T. C. von Storch, who found the fossils remains in Princeton 1927 Expedition..
Paleoecology
Greenland
Greenland is an autonomous country within the Kingdom of Denmark, located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago. Though physiographically a part of the continent of North America, Greenland has been politically and culturally associated with Europe for...
was probably then covered with lush woodland and grassland, only narrow strait
Strait
A strait or straits is a narrow, typically navigable channel of water that connects two larger, navigable bodies of water. It most commonly refers to a channel of water that lies between two land masses, but it may also refer to a navigable channel through a body of water that is otherwise not...
s of a few 100 km would have blocked entirely landbound dispersal of the Gastornis ancestors. While there were large contiguous areas of land in their North American range after the Western Interior Seaway
Western Interior Seaway
The Western Interior Seaway, also called the Cretaceous Seaway, the Niobraran Sea, and the North American Inland Sea, was a huge inland sea that split the continent of North America into two halves, Laramidia and Appalachia, during most of the mid- and late-Cretaceous Period...
had receded, their European range was an archipelago
Archipelago
An archipelago , sometimes called an island group, is a chain or cluster of islands. The word archipelago is derived from the Greek ἄρχι- – arkhi- and πέλαγος – pélagos through the Italian arcipelago...
due to the Alpide orogeny and the high sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
s of the Paleocene-Eocene Thermal Maximum
Paleocene-Eocene Thermal Maximum
The most extreme change in Earth surface conditions during the Cenozoic Era began at the temporal boundary between the Paleocene and Eocene epochs . This event, the Paleocene–Eocene Thermal Maximum , was associated with rapid global...
; geographically (but not geologically), it was perhaps roughly similar to today's Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
.
Classically, Gastornis has been depicted as predatory. However, with the size of Gastornis legs, the bird would have had to have been more agile to catch fast-moving prey than the fossils suggest it to have been. Consequently, it has been suspected that Gastornis was an ambush hunter and/or used pack hunting techniques to pursue or ambush prey; if Gastornis was a predator, it would have certainly needed some other means of hunting prey through the dense forest .
Alternatively, they may have been predominantly scavengers, omnivore
Omnivore
Omnivores are species that eat both plants and animals as their primary food source...
s or even herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
s. Indeed, the large beak of Gastornis would have been as well suited for crushing seeds and tearing off vegetation. But it seems excessively strong for a purely vegetarian diet, except in the rather improbable case that huge hard-shelled seeds and nut
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...
s formed the main food item of Gastornis. Regardless of what these birds ate, the beak may simply have been used for social display though its presence in all known fossils argues against a sexual display role. These contradicting hypotheses, equivocally supported by the material evidence, make the dietary paleobiology of Gastornis impossible to pinpoint.
Similar gigantic birds of the Cenozoic were the South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n terror birds (phorusrhacids) and the Australian mihirungs (Dromornithidae
Dromornithidae
Dromornithidae — the dromornithids — were a family of large, flightless Australian birds of the Oligocene through Pleistocene epochs. All are now extinct. They were long classified in the order Struthioniformes, but are now usually classified as a family of Anseriformes1...
). The former were certainly carnivorous, and the latter are suspected of being predators, too. On the other hand, ratite
Ratite
A ratite is any of a diverse group of large, flightless birds of Gondwanan origin, most of them now extinct. Unlike other flightless birds, the ratites have no keel on their sternum—hence the name from the Latin ratis...
s, the flightless giant birds of our time, feed on plants, small vertebrates, and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
s.
Gastornis were among the largest, if not the largest birds alive during the Paleogene
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
. They had few natural enemies and serious competitors apart from other Gastornis or then-rare large mammals, such as the predatory bear-like Arctocyon
Arctocyon
Arctocyon is an extinct genus of condylarth mammals. The jackal-sized creature was plantigrade, that is, it walked on the soles of its feet, like a bear. Although probably mainly terrestrial, it is possible that it also climbed trees. Arctocyon was probably an omnivore....
of Europe. If these huge birds were active hunters, they must have been important apex predator
Apex predator
Apex predators are predators that have no predators of their own, residing at the top of their food chain. Zoologists define predation as the killing and consumption of another organism...
s that dominated the forest ecosystems of North America and Europe until the middle Eocene. The mid-Eocene saw the rise of large creodont and mesonychid
Mesonychid
Mesonychia are an extinct order of medium to large-sized carnivorous mammals that were closely related to artiodactyls and to cetaceans...
predators to ecological prominence in Eurasia and North America; the appearance of these new predators coincides with the decline of Gastornis and its relatives. This was possibly due to an increased tendency of mammalian predators to hunt together in packs (prevalent especially in hyaenodont
Hyaenodontidae
Hyaenodontidae is a family of the extinct order Creodonta, which contains several dozen genera.The Hyaenodontids were important mammalian predators that arose during the late Paleocene and persisted well into the Miocene...
creodonts). The fact that no birds appear to have ever weighed much more than half a metric ton suggests that they were restricted in their ability to evolve to larger and larger sizes, and thus in their ability to out-evolve apex predators by sheer bulk as mammals are often able to do (see Cope's Rule
Cope's rule
Cope's rule states that population lineages tend to increase in body size over evolutionary time. While the rule has been demonstrated in many instances, it does not hold true at all taxonomic levels, or in all clades...
).
The fossil bones originally described as Omorhamphus storchii are the remains of a juvenile Gastornis giganteus. Specimen YPM PU
Princeton University
Princeton University is a private research university located in Princeton, New Jersey, United States. The school is one of the eight universities of the Ivy League, and is one of the nine Colonial Colleges founded before the American Revolution....
13258 from Early Eocene Willwood Formation rocks of Park County, Wyoming also seems to be a juvenile - perhaps of G. giganteus too, in which case it would be an even younger individual.
Trace fossils
Spain
Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...
and Early Eocene deposits of France, shell fragments of huge eggs
Egg (biology)
An egg is an organic vessel in which an embryo first begins to develop. In most birds, reptiles, insects, molluscs, fish, and monotremes, an egg is the zygote, resulting from fertilization of the ovum, which is expelled from the body and permitted to develop outside the body until the developing...
have turned up, namely in the Provence
Provence
Provence ; Provençal: Provença in classical norm or Prouvènço in Mistralian norm) is a region of south eastern France on the Mediterranean adjacent to Italy. It is part of the administrative région of Provence-Alpes-Côte d'Azur...
. These were described as the ichnotaxon
Ichnotaxon
An ichnotaxon is defined by the International Code of Zoological Nomenclature as "a taxon based on the fossilized work of an organism", that is, the non-human equivalent of an artifact. Ichnotaxa are names used to identify and distinguish morphologically distinctive ichnofossils, more commonly...
Ornitholithus and are presumably from Gastornis. While no direct association exists between Ornitholithus and Gastornis fossils, no other birds of sufficient size are known from that time and place: while the large Diogenornis
Diogenornis
Diogenornis is an extinct genus of ratite which lived during the Paleocene. It was described in 1983 by Brazilian scientist Herculano Marcos Ferraz de Alvarenga. The type species is D. fragilis.-References:...
and Eremopezus
Eremopezus
Eremopezus is a prehistoric bird genus. It is known only from the fossil remains of a single species,the huge and presumably flightless Eremopezus eocaenus. This was found in Upper Eocene Jebel Qatrani Formation deposits around the Qasr el-Sagha escarpment, north of the Birket Qarun lake near...
are known from the Eocene, the former lived in South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
(still separated from North America by the Tethys Ocean
Tethys Ocean
The Tethys Ocean was an ocean that existed between the continents of Gondwana and Laurasia during the Mesozoic era before the opening of the Indian Ocean.-Modern theory:...
then) and the latter is only known from the Late Eocene of North Africa, which also was separated by an (albeit less wide) stretch of the Tethys Ocean from Europe. The mid-Eocene ostrich
Ostrich
The Ostrich is one or two species of large flightless birds native to Africa, the only living member of the genus Struthio. Some analyses indicate that the Somali Ostrich may be better considered a full species apart from the Common Ostrich, but most taxonomists consider it to be a...
relative Palaeotis
Palaeotis
Palaeotis is a genus of paleognath bird from the middle Eocene epoch of central Europe. One species is known, Paleotis weigelti. The holotype specimen is a fossil tarsometatarsus and phalanx. Lambrect described it as an extinct bustard , and gave it its consequent name . After a suggestion by...
from Europe, on the other hand, was a bustard
Bustard
Bustards, including floricans and korhaans, are large terrestrial birds mainly associated with dry open country and steppes in the Old World...
-sized bird, and the mysterious large Remiornis from France is only known from Paleocene
Paleocene
The Paleocene or Palaeocene, the "early recent", is a geologic epoch that lasted from about . It is the first epoch of the Palaeogene Period in the modern Cenozoic Era...
remains.
Paleogene
The Paleogene is a geologic period and system that began 65.5 ± 0.3 and ended 23.03 ± 0.05 million years ago and comprises the first part of the Cenozoic Era...
deposits of Provence, were it not for the fact that these eggshell fossils also date from the Eocene but no Remiornis bones are known from that time yet.
There is no footprint record which is unequivocally known to be of Gastornis. This may be somewhat surprising, as there is an abundant record of fossilized bird and non-avian dinosaur tracks from the Cretaceous and Paleogene. But most of these are from shorelines or swamps, and thus the lack of Gastornis footprints might indicate that these birds stayed off soft ground, preferring terrain where they had better footing and consequently did not leave many trackways.
However, two mysterious footprint fossilizations are known that might be of Gastornis. One set of footprints was reported from Late Eocene gypsum
Gypsum
Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...
at Montmorency
Montmorency, Val-d'Oise
Montmorency is a commune in the northern suburbs of Paris, France. It is located from the center of Paris.Montmorency was the fief of the Montmorency family, one of the oldest and most distinguished families of the French nobility...
and other locations of the Paris Basin
Paris Basin
Paris Basin may refer to:*As a hydrological basin, it is largely the basin of the River Seine* Paris Basin , the geological basin...
in the 19th century, from 1859 onwards. Described initially by Jules Desnoyers
Jules Desnoyers
Jules Pierre François Stanislaus Desnoyers was a French geologist and archaeologist.-Life:Desnoyers was born at Nogent-le-Rotrou, in the department of Eure-et-Loir. Becoming interested in geology at an early age, he was one of the founders of the Geological Society of France in 1830...
and later on by Alphonse Milne-Edwards
Alphonse Milne-Edwards
Alphonse Milne-Edwards was a French mammalologist, ornithologist and carcinologist. He was English in origin, the son of Henri Milne-Edwards and grandson of Bryan Edwards, a Jamaican planter who settled at Bruges .Milne-Edwards obtained a medical degree in 1859 and became assistant to his father...
, these ichnofossils were quite celebrated, and most French geologists of the late 19th century knew about them. They were discussed by Charles Lyell
Charles Lyell
Sir Charles Lyell, 1st Baronet, Kt FRS was a British lawyer and the foremost geologist of his day. He is best known as the author of Principles of Geology, which popularised James Hutton's concepts of uniformitarianism – the idea that the earth was shaped by slow-moving forces still in operation...
in his Elements of Geology as an example of the incompleteness of the fossil record - no bones had been found associated with the footprints. Unfortunately, these fine specimens which sometimes preserved even details of the skin structure are now lost. They were brought to the Muséum national d'histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...
when Desnoyers started to work there, and the last documented record of them deals with their presence in the geology exhibition of the MNHN in 1912. The largest of these footprints, although only consisting of a single toe's impression, was a stunning 40 cm (16 in) long. Interestingly, the large footprints from the Paris Basin
Paris Basin
Paris Basin may refer to:*As a hydrological basin, it is largely the basin of the River Seine* Paris Basin , the geological basin...
could also be divided into huge and "merely" large examples, much like the eggshells from southern France which are 20 million years older.
The other footprint record consists of a single imprint which still exists, though it has proven to be even more controversial. It was found in Late Eocene Puget Group rocks in the Green River
Green River (Washington)
The Green River is a long river in the state of Washington in the United States, arising on the western slopes of the Cascade Mountains south of I-90....
valley near Black Diamond, Washington
Black Diamond, Washington
Black Diamond is a city in King County, Washington, United States. The population was 4,151 at the 2010 census.Based on per capita income, one of the more reliable measures of affluence, Black Diamond ranks 64th of 522 areas in the state of Washington to be ranked.-History:Black Diamond was...
. After its discovery, it raised considerable interest in the Seattle area in May–July 1992, being subject of at least two longer articles in the Seattle Times. Variously declared a hoax
Hoax
A hoax is a deliberately fabricated falsehood made to masquerade as truth. It is distinguishable from errors in observation or judgment, or rumors, urban legends, pseudosciences or April Fools' Day events that are passed along in good faith by believers or as jokes.-Definition:The British...
or genuine, this apparent impression of a single bird foot measures about 27 cm wide by 32 cm long (11 by 13 in) and lacks a hallux
Hallux
In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals...
(hind toe); it was described as the ichnotaxon Ornithoformipes controversus. 14 years after the initial discovery, the debate about the find's authenticity was still unresolved. The specimen is now at Western Washington University
Western Washington University
Western Washington University is one of six state-funded, four-year universities of higher education in the U.S. state of Washington. It is located in Bellingham and offers bachelor's and master's degrees.-History:...
.
The problem with these trace fossils is that no fossil of Gastornis has been found to be younger than about 45 million years. The enigmatic "Diatryma" cotei is known from remains almost as old as the Paris basin footprints (whose date never could be accurately determined), but in North America the fossil record of unequivocal gastornithids seems to end even earlier than in Europe.