Fruitadens
Encyclopedia
Fruitadens is a genus
of heterodontosaurid
dinosaur
. The name means "Fruita tooth", in reference to Fruita, Colorado
(USA), where its fossils were first found. It is known from partial skulls and skeletons from at least four individuals of differing biological ages, found in Tithonian
(Late Jurassic
) rocks of the Morrison Formation
in Colorado
. Fruitadens is the smallest known ornithischia
n dinosaur, with young adults estimated at 65 centimetre in length and 0.5 kilogram in weight. It is interpreted as an omnivore and represents one of the latest-surviving heterodontosaurids.
(LACM). The discovery area, on lands managed by the Bureau of Land Management
, is known as the Fruita Paleontological Area; the specimens were found there in sandstone
s of the Brushy Basin Member. Roughly equivalent beds have been dated to 150.3 ± 0.3 million years old and 150.2 ± 0.5 million years old, indicating an early Tithonian age.
The fossils now named Fruitadens were first thought to belong to a fabrosaurid
similar to Echinodon
, a genus from the Early Cretaceous
of England
; Fabrosauridae at the time was considered a general group of primitive
ornithopods, and Echinodon itself had not yet been reclassified as a heterodontosaurid. Fruitadens, although not formally described for a number of years, was briefly described in several works, usually as a relative of Echinodon or a new species of the genus. Formal description came in January 2010, by Richard Butler and colleagues (though the paper was published online before print in late 2009). The type species
is F. haagarorum, in recognition of support provided by Paul Haaga Jr., Heather Haaga, Blythe Haaga, Paul Haaga III, and Catalina Haaga for the Natural History Museum of Los Angeles County.
LACM 115747, consisting of incomplete jaws, a number of vertebrae, and partial hind limbs, of a nearly fully grown individual. At least three other individuals have been found. LACM 115727 is another nearly fully grown individual, known from vertebrae and hind limb bones. This individual was about the same size as LACM 115747, and was five years old at death. LACM 120478 consists of the upper arm
and most of the left leg of a juvenile, in its second year. Finally, LACM 128258 includes partial jaws and vertebrae of another juvenile. The largest individuals are estimated to have been about 65 centimetre long and 0.5 kilogram in weight. This makes Fruitadens the smallest known ornithischian and comparable in size to the smallest known dinosaurs, outside of birds. Known material of Echinodon
and Tianyulong
, related heterodontosaurids, comes from similar-sized individuals, but it is not known how old they were upon death.
Fruitadens was similar to Heterodontosaurus
in anatomy, with relatively short arms and long distal
sections of the legs (feet and shins
). The lower jaws had an enlarged canine-like tooth
, with a corresponding gap in the upper jaw. Unlike Echinodon, there wasn't an enlarged tooth in the upper jaw. Uniquely, a small peg-like tooth was present in front of the canine-like tooth. Replacement teeth were present in the jaws, unlike most other heterodontosaurids. The hind limb bones were hollow, like those of small theropod
dinosaurs. Fruitadens seems to have been more closely related to Heterodontosaurus than Echinodon, which was closer in time.
sandstones deposited in floodplain
s. The Fruita localities preserved a contemporaneous fauna including snails, clams, crayfish, various insects (represented by trace fossil
s), the lungfish
Ceratodus
, ray–finned fish
, the turtle Glyptops
, rhynchocephalian reptiles Eilenodon
and Opisthias
, several genera of lizards, a mesosuchia
n crocodylomorph
, and the mammals Fruitafossor
, Glirodon
, and Priacodon
. Disarticulated dinosaur fossils are common in the area.
Fruitadens was probably bipedal and cursorial
, and is suggested to have been omnivorous. Like Echinodon and Tianyulong, other late-surviving heterodontosaurids, Fruitadens had less specialized jaws than Early Jurassic
heterodontosaurids like Heterodontosaurus, and is interpreted as a generalist
.
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 heterodontosaurid
Heterodontosauridae
Heterodontosauridae is a family of early ornithischian dinosaurs that were likely among the most basal members of the group...
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...
. The name means "Fruita tooth", in reference to Fruita, Colorado
Fruita, Colorado
The City of Fruita is a Home Rule Municipality located in the western part of Mesa County, Colorado, in the United States. It is part of the Grand Junction Metropolitan Statistical Area and within the Grand Valley...
(USA), where its fossils were first found. It is known from partial skulls and skeletons from at least four individuals of differing biological ages, found in Tithonian
Tithonian
In the geologic timescale the Tithonian is the latest age of the Late Jurassic epoch or the uppermost stage of the Upper Jurassic series. It spans the time between 150.8 ± 4 Ma and 145.5 ± 4 Ma...
(Late Jurassic
Late Jurassic
The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.2 ± 4.0 to 145.5 ± 4.0 million years ago , which is preserved in Upper Jurassic strata. In European lithostratigraphy, the name "Malm" indicates rocks of Late Jurassic age...
) rocks of the Morrison Formation
Morrison Formation
The Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...
in Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
. Fruitadens is the smallest known ornithischia
Ornithischia
Ornithischia or Predentata is an extinct order of beaked, herbivorous dinosaurs. The name ornithischia is derived from the Greek ornitheos meaning 'of a bird' and ischion meaning 'hip joint'...
n dinosaur, with young adults estimated at 65 centimetre in length and 0.5 kilogram in weight. It is interpreted as an omnivore and represents one of the latest-surviving heterodontosaurids.
History of discovery
Fruitadens is known from fossils recovered under a valid paleontological permit in the 1970s and 1980s by teams led by George Callison, for the Natural History Museum of Los Angeles CountyNatural History Museum of Los Angeles County
The Natural History Museum of Los Angeles County opened in Exposition Park, Los Angeles, California, USA in 1913 as the Museum of History, Science, and Art. The moving force behind it was a museum association founded in 1910. Its distinctive main building, with fitted marble walls and domed and...
(LACM). The discovery area, on lands managed by the Bureau of Land Management
Bureau of Land Management
The Bureau of Land Management is an agency within the United States Department of the Interior which administers America's public lands, totaling approximately , or one-eighth of the landmass of the country. The BLM also manages of subsurface mineral estate underlying federal, state and private...
, is known as the Fruita Paleontological Area; the specimens were found there in sandstone
Sandstone
Sandstone is a sedimentary rock composed mainly of sand-sized minerals or rock grains.Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow,...
s of the Brushy Basin Member. Roughly equivalent beds have been dated to 150.3 ± 0.3 million years old and 150.2 ± 0.5 million years old, indicating an early Tithonian age.
The fossils now named Fruitadens were first thought to belong to a fabrosaurid
Fabrosauridae
The Fabrosauridae was originally proposed by Galton , as a group of basal ornithischian dinosaurs from the Early to Middle Jurassic. However, recent studies indicate the Fabrosaurs are not a natural grouping of dinosaurs, and instead consist of unrelated genera.The proposed "Fabrosaurs" descended...
similar to Echinodon
Echinodon
Echinodon meaning "hedgehog tooth" in reference to the spines on its teeth , occasionally known as Saurechinodon, is a genus of small European dinosaur of the early Cretaceous Period , 140 million years ago.-Discovery and species:The type specimen was discovered by Samuel Beckles in the Purbeck...
, a genus from the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
of 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...
; Fabrosauridae at the time was considered a general group of primitive
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
ornithopods, and Echinodon itself had not yet been reclassified as a heterodontosaurid. Fruitadens, although not formally described for a number of years, was briefly described in several works, usually as a relative of Echinodon or a new species of the genus. Formal description came in January 2010, by Richard Butler and colleagues (though the paper was published online before print in late 2009). The type species
Type species
In 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...
is F. haagarorum, in recognition of support provided by Paul Haaga Jr., Heather Haaga, Blythe Haaga, Paul Haaga III, and Catalina Haaga for the Natural History Museum of Los Angeles County.
Description
Fruitadens is based onHolotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
LACM 115747, consisting of incomplete jaws, a number of vertebrae, and partial hind limbs, of a nearly fully grown individual. At least three other individuals have been found. LACM 115727 is another nearly fully grown individual, known from vertebrae and hind limb bones. This individual was about the same size as LACM 115747, and was five years old at death. LACM 120478 consists of the upper arm
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
and most of the left leg of a juvenile, in its second year. Finally, LACM 128258 includes partial jaws and vertebrae of another juvenile. The largest individuals are estimated to have been about 65 centimetre long and 0.5 kilogram in weight. This makes Fruitadens the smallest known ornithischian and comparable in size to the smallest known dinosaurs, outside of birds. Known material of Echinodon
Echinodon
Echinodon meaning "hedgehog tooth" in reference to the spines on its teeth , occasionally known as Saurechinodon, is a genus of small European dinosaur of the early Cretaceous Period , 140 million years ago.-Discovery and species:The type specimen was discovered by Samuel Beckles in the Purbeck...
and Tianyulong
Tianyulong
Tianyulong is a genus of heterodontosaurid ornithischian dinosaur. The only species is T. confuciusi, whose remains were discovered in Jianchang County, Western Liaoning Province, China...
, related heterodontosaurids, comes from similar-sized individuals, but it is not known how old they were upon death.
Fruitadens was similar to Heterodontosaurus
Heterodontosaurus
Heterodontosaurus is a genus of small herbivorous dinosaur with prominent canine teeth which lived in the Early Jurassic of South Africa. It was similar to a hypsilophodont in shape, and ate plants, despite its canines.Heterodontosaurus is currently known from specimens of the SAFM from South...
in anatomy, with relatively short arms and long distal
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
sections of the legs (feet and shins
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....
). The lower jaws had an enlarged canine-like tooth
Canine tooth
In mammalian oral anatomy, the canine teeth, also called cuspids, dogteeth, fangs, or eye teeth, are relatively long, pointed teeth...
, with a corresponding gap in the upper jaw. Unlike Echinodon, there wasn't an enlarged tooth in the upper jaw. Uniquely, a small peg-like tooth was present in front of the canine-like tooth. Replacement teeth were present in the jaws, unlike most other heterodontosaurids. The hind limb bones were hollow, like those of small theropod
Theropoda
Theropoda is both a suborder of bipedal saurischian dinosaurs, and a clade consisting of that suborder and its descendants . Dinosaurs belonging to the suborder theropoda were primarily carnivorous, although a number of theropod groups evolved herbivory, omnivory, and insectivory...
dinosaurs. Fruitadens seems to have been more closely related to Heterodontosaurus than Echinodon, which was closer in time.
Paleoecology and paleobiology
The four individuals were found in localities at the base of the Morrison Formation's Brushy Basin Member, in crevasse splayCrevasse splay
A crevasse splay is a sedimentary fluvial deposit which forms when a stream breaks its natural or artificial levees and deposits sediment on a floodplain. This breach can cause large deposits that spread in a pattern similar to that of an alluvial fan deposit. Once the levee has been breached the...
sandstones deposited in floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
s. The Fruita localities preserved a contemporaneous fauna including snails, clams, crayfish, various insects (represented by trace fossil
Trace fossil
Trace fossils, also called ichnofossils , are geological records of biological activity. Trace fossils may be impressions made on the substrate by an organism: for example, burrows, borings , urolites , footprints and feeding marks, and root cavities...
s), the lungfish
Lungfish
Lungfish are freshwater fish belonging to the Subclass Dipnoi. Lungfish are best known for retaining characteristics primitive within the Osteichthyes, including the ability to breathe air, and structures primitive within Sarcopterygii, including the presence of lobed fins with a well-developed...
Ceratodus
Ceratodus
Ceratodus was a wide-ranging genus of extinct sarcopterygiian lungfish. Fossil evidence dates back to the Middle Triassic 228 million years ago. A wide range of fossil species from different time periods have been found around the world in places such as the United States, Argentina, England,...
, ray–finned fish
Actinopterygii
The Actinopterygii or ray-finned fishes constitute a class or sub-class of the bony fishes.The ray-finned fishes are so called because they possess lepidotrichia or "fin rays", their fins being webs of skin supported by bony or horny spines , as opposed to the fleshy, lobed fins that characterize...
, the turtle Glyptops
Glyptops
Glyptops is an extinct genus of cryptodire turtle dating from the Late Jurassic and Early Cretaceous periods 155 to 99 m.y.a. Fossils have been found in South Dakota, Wyoming, Colorado, Utah, New Mexico, Oklahoma, and Texas from both the Morrison and Cedar Mountain formations. The type species is G...
, rhynchocephalian reptiles Eilenodon
Eilenodon
Eilenodon is a Late Jurassic genus of sphenodont reptile from the Morrison Formation of western North America, present in stratigraphic zone 4.-See also:* Prehistoric reptile* Paleobiota of the Morrison Formation...
and Opisthias
Opisthias
Opisthias is a Late Jurassic genus of sphenodont reptile from the Morrison Formation of western North America, present in stratigraphic zones 2 and 4-6.-See also:* Prehistoric reptile* Paleobiota of the Morrison Formation...
, several genera of lizards, a mesosuchia
Mesosuchia
"Mesosuchia" is an obsolete name for a group of terrestrial, semi-aquatic, or fully aquatic crocodylomorph reptiles. The marine crocodile Metriorhynchus had paddle-like forelimbs, Dakosaurus andiniensis had a skull that was adapted to eat large sea reptiles, and Shamosuchus was adapted for eating...
n crocodylomorph
Crocodylomorpha
The Crocodylomorpha are an important group of archosaurs that include the crocodilians and their extinct relatives.During Mesozoic and early Tertiary times the Crocodylomorpha were far more diverse than they are now. Triassic forms were small, lightly built, active terrestrial animals. These were...
, and the mammals Fruitafossor
Fruitafossor
Fruitafossor was a termite-eating mammal endemic to North America during the Late Jurassic epoch , existing for approximately ....
, Glirodon
Glirodon
Glirodon is a genus of extinct mammal from the Upper Jurassic. It was a relatively early member of the also-extinct order of Multituberculata, suborder "Plagiaulacida". These mammals lived in North America during the Mesozoic, also known as the "age of the dinosaurs".The genus Glirodon has been...
, and Priacodon
Priacodon
Priacodon is an extinct genus of Late Jurassic mammal from the Morrison Formation.Present in stratigraphic zones 4–6.-See also:* Prehistoric amphibian** List of prehistoric amphibians* Paleobiota of the Morrison Formation-References:...
. Disarticulated dinosaur fossils are common in the area.
Fruitadens was probably bipedal and cursorial
Cursorial
Cursorial is a biological term that describes an organism as being adapted specifically to run. It is typically used in conjunction with an animal's feeding habits or another important adaptation. For example, a horse can be considered a "cursorial grazer", while a wolf may be considered a...
, and is suggested to have been omnivorous. Like Echinodon and Tianyulong, other late-surviving heterodontosaurids, Fruitadens had less specialized jaws than Early Jurassic
Early Jurassic
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period...
heterodontosaurids like Heterodontosaurus, and is interpreted as a generalist
Generalist and specialist species
A generalist species is able to thrive in a wide variety of environmental conditions and can make use of a variety of different resources . A specialist species can only thrive in a narrow range of environmental conditions or has a limited diet. Most organisms do not all fit neatly into either...
.
See also
- 2010 in paleontology2010 in paleontology-Anomalocaridids:-Newly named crustaceans:-Newly named insects:* A new family, Cascopleciidae, is published by Poinar Jr.* A new family of ceraphronoid Hymenopters, Radiophronidae, is published by Ortega-Blanco, Rasnitsyn, and Delclòs....
- Dinosaurs of the Morrison FormationDinosaurs of the Morrison FormationThe Morrison Formation is a distinctive sequence of Late Jurassic sedimentary rock that is found in the western United States, which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltstone and limestone and is light grey, greenish...