Sinosauropteryx
Encyclopedia
Sinosauropteryx was the first genus
of dinosaur
outside of Avialae
(birds and their immediate relatives) to be found with evidence of feather
s. They were covered with "furry" coats of very simple filament-like feathers. Structures that indicate colouration have been preserved for some of the feathers, which also makes Sinosauropteryx the first non-avialian dinosaurs where colouration has been determined. Colouration includes a banded tail with reddish and light bands. Some contention has arisen with an alternative interpretation of the filamentous impression as remains of collagen
fibres.
Sinosauropteryx were small theropod
s with unusually long tails and short arms. They were close relatives of the similar but older genus Compsognathus
, both genera belonging to the family
Compsognathidae
. Only one species
of Sinosauropteryx has been named: S. prima, meaning "first" in reference to its status as the first feathered non-avialian dinosaur species discovered. A handful of specimens have been described. One specimen previously assigned to this genus represents either a second, as-yet unnamed species or a related genus.
Sinosauropteryx prima lived in what is now northeastern China
during the early Cretaceous
period. They were among the first dinosaurs discovered from the Yixian Formation
in Liaoning Province, and were members of the remarkable Jehol Biota
. Well-preserved fossils of this species illustrate many aspects of their biology, such as their diet and reproduction.
Sinosauropteryx prima were small bipedal theropods, noted for their short arms, large first fingers (thumbs), and long tails. The species includes some of the smallest known adult non-avian theropod specimens, with the holotype
specimen measuring only 68 cm (26.8 in) in length, including the tail. This individual was relatively young. The longest known specimen reaches up to 1.07 m (3.5 ft) in length, with an estimated weight of 0.55 kg (1.2 lb).
Sinosauropteryx were anatomically similar to Compsognathus, differing from their European relatives in their proportions. The skulls of Sinosauropteryx were 15% longer than their thigh bones
, unlike Compsognathus, in which the skulls and thigh bones are approximately equivalent in length. The arms of Sinosauropteryx (humerus
and radius
) were only 30% the length of their legs (thigh bone and shin
), compared to 40% in Compsognathus. Additionally, Sinosauropteryx had several features unique among all other theropods. S. prima had 64 vertebrae in their tails. This high number helps give them the longest tails relative to body length of any theropod species. Their hands were long compared to its arms, about 84% to 91% of the length of the rest of the arm (humerus and radius), and half the length of the foot. The first and second digits were about the same length, with a large claw on the first digit. The first fingers were large, being both longer and thicker than either of the bones of the forearm. The teeth differed slightly
based on position: those near the tips of the upper jaws (on the premaxilla
e) were slender and lacked serrations, while those behind them (on the maxilla
e) were serrated and laterally compressed. The teeth of the lower jaws were similarly differentiated.
A pigmented area in the abdomen of the holotype has been suggested as possible traces of organs, and was interpreted as the liver
by John Ruben and colleagues, which they described as part of a crocodilia
n-like "hepatic piston" respiratory system. A later study, while agreeing that the pigmented area represented something originally inside the body, found no defined structure and noted that any organs would have been distorted by the processes that flattened the skeleton into an essentially two-dimensional form. Dark pigment is also present in the eye region of the holotype and another specimen.
Three specimens have been assigned to Sinosauropteryx prima: the holotype GMV
2123 (and its counter slab
[opposite face], NIGP 127586), NIGP 127587, and D 2141. Another specimen, IVPP
V14202, was assigned to the genus but not to a species by Zhang and colleagues. The assignment of an additional larger specimen to S. prima, GMV
2124, was later found to be in error. All of the fossils were found in the Jianshangou or Dawangzhangzi Beds of the Yixian Formation
in the Beipiao
and Lingyuan
regions of Liaoning
, China. These fossil beds have been dated to 124.6–122 million years ago, during the late Barremian
to early Aptian
stages of the Early Cretaceous
.
, the genus is only distantly related to the clade
Aves, usually defined as Archaeopteryx lithographica plus modern birds. The scientists who described Sinosauropteryx, however, used a character-based, or apomorphic, definition of the Class
Aves, in which any animal with feathers is considered to be a bird. They argued that the filamentous plumes of Sinosauropteryx represent true feathers with a rachis
and barbs, and thus that Sinosauropteryx should be considered a true bird. They classified the genus as belonging to a new biological order
, Sinosauropterygiformes, family Sinosauropterygidae, within the subclass Sauriurae
. These proposals have not been accepted, and Sinosauropteryx is generally classified in the family
Compsognathidae
, a group of small-bodied long-tailed coelurosauria
n theropods known from the Late Jurassic
and Early Cretaceous
of Asia, Europe, and South America.
There is only one named species of Sinosauropteryx, S. prima. A possible second species is represented by the specimen GMV 2124 (aka NGMC 2124), which was described as another, larger specimen of S. prima by Ji and Ji in 1997. However, in a 2002 presentation and abstract for the Society of Vertebrate Paleontology
, Nick Longrich showed that this specimen differs in several anatomical aspects from the others, including its relatively large size, proportionally longer shins, and shorter tail. Longrich suggested that GMV 2124 was a compsognathid coelurosaurian, while Sinosauropteryx proper was a more primitive kind of coelurosaurian or even a basal
carnosauria
n. In 2007, Gishlick and Gauthier concurred that this specimen was probably a new taxon
, and tentatively re-classified it as Sinosauropteryx? sp., though they suggested it may belong in a new genus. Also in 2007, Ji, Ji and colleagues wrote that GMV 2124 is probably a new genus, noting the differences in tail length and hindlimb proportions.
The first fossil specimen of the dinosaur later named Sinosauropteryx prima was uncovered in August 1996 by Li Yumin. Yumin was a farmer and part-time fossil hunter who often prospected around Liaoning Province to acquire fossils to sell to individuals and museums. Yumin recognized the unique quality of the specimen, which was separated into two slabs, and sold the slabs to two separate museums in China: the National Geological Museum in Beijing
, and the Nanjing
Institute of Geology and Paleontology. The director of the Beijing museum, Ji Qiang, recognized the importance of the find, as did visiting Canadian palaeontologist Phil Currie
and artist Michael Skrepnick, who became aware of the fossil by chance as they explored the Beijing museum's collections after leading a fossil tour of the area during the first week of October, 1996. Currie recognized the significance of the fossil immediately. As The New York Times quoted him, "When I saw this slab of silt stone
mixed with volcanic ash in which the creature is embedded, I was bowled over."
Chinese authorities initially barred photographs of the specimen from publication. However, Currie brought a photograph to the 1996 meeting of the Society of Vertebrate Paleontology
at the American Museum of Natural History
in New York, causing crowds of palaeontologists to gather and discuss the new discovery. The news reportedly left palaeontologist John Ostrom
, who in the 1970s had pioneered the theory that birds evolved from dinosaurs, "in a state of shock." Ostrom later joined an international team of researchers who gathered in Beijing to examine the fossils; other team members included feather expert Alan Brush, fossil bird expert Larry Martin
, and Peter Wellnhofer
, an expert on the early bird Archaeopteryx
.
on Thursday, April 24, 1997) were inconclusive; the team agreed that the structures preserved on Sinosauropteryx were not modern feathers, but suggested further research was required to discover their exact nature. Palaeontologist Alan Feduccia
, who had not yet examined the specimen, wrote in Audubon Magazine that the structures of Sinosauropteryx (which he considered at the time to be a synonym of Compsognathus, as Compsognathus prima) were stiffening structures from a frill running along the back, and that dinosaur palaeontologists were engaging in wishful thinking when equating the structures with feathers. Subsequent publications saw some of the team members disagreeing over the identity of the structures.
Feduccia's frill argument was followed up in several other publications, in which researchers interpreted the filamentous impressions around Sinosauropteryx fossils as remains of collagen
fibres rather than primitive feathers. Since the structures are clearly external to the body, these researchers have proposed that the fibres formed a frill on the back of the animal and underside of its tail, similar to some modern aquatic lizards. The absence of feathers would refute the proposal that Sinosauropteryx is the most basal
known theropod genus with feathers, and also raise questions about the current theory of feather origins itself. It calls into question the idea that the first feathers evolved not for flight
but for insulation, and that they made their first appearance in relatively basal dinosaur lineages that later evolved into modern birds.
Most researchers have disagreed with the identification of the structures as collagen or other structural fibres. Notably, the team of scientists that reported the presence of pigmentation cells in the structures argued that their presence proved the structures were feathers, not collagen, because collagen does not contain pigment. Gregory S. Paul
reidentified what the collagen hypothesis's proponents consider a body outline outside of the fibres as an artefact of preparation: breakage and brushed-on sealant have been misidentified as the outline of the body.
dinosaur, is a member of the Jehol Biota
, the assemblage of organisms found in the Yixian Formation and overlying Jiufotang Formation
. The Yixian Formation is composed largely of volcanic rock
s such as andesite
and basalt
. Between the volcanic layers are several beds of sedimentary rock
s representing deposition in a lake
. The freshwater lake strata of the Yixian Formation have preserved a wide variety of plants, invertebrates, and vertebrates. Gymnosperm
forests were extensive, with a few early flowering plants as well. Ostracod
s and insects were diverse, and bivalves and gastropods were abundant. Mammals and birds are also well-known from the formation. The setting was subject to periodic mortality events including volcanic eruptions, wildfire
s, and noxious gases erupting from the lakes
. The climate has been interpreted as temperate
, with distinct wet and dry seasons. The yearly temperature during this time period averaged about 10 degrees celsius
(50 degrees Fahrenheit
), indicating a temperate climate with unusually cold winters for the generally warm Mesozoic era, possibly due to northern China's high latitude during this time.
The specimen NIGP 127587 was preserved with the remains of a lizard
in its gut region, indicating that small, fast-moving animals made up part of the diet of Sinosauropteryx prima. Numerous lizards of this type have been found in the same rocks as Sinosauropteryx, but have yet to be described.
The possible Sinosauropteryx specimen GMV 2124 (Sinosauropteryx? sp.) was found with three mammal jaws in its gut region. Hurum, Luo, and Kielan-Jaworowska (2006) identified two of these jaws as belonging to Zhangheotherium
and the third to Sinobaatar
, showing that these two mammals were part of the animal's diet. Interestingly, Zhangheotherium is known to have had a spur on the ankle, like the modern platypus
, which would indicate that Sinosauropteryx fed on possibly venomous mammals.
in its abdomen. Two eggs were preserved just in front of and above the pubic
boot, and several more may lie underneath them on the slab. It is unlikely that they were eaten by the animal, as they are in the wrong part of the body cavity for the egg shells to have remained intact. It is more likely that they are unlaid eggs produced by the animal itself. Each egg measured 36 mm (1.4 in) long by 26 mm (1 in) wide. The presence of two developed eggs suggests that Sinosauropteryx had dual oviduct
s and laid eggs in pairs, like other theropods.
s. These short, down-like filaments are preserved along the back half of the skull, arms, neck, back, and top and bottom of the tail. Additional patches of feathers have been identified on the sides of the body, and palaeontologists Chen, Dong and Zheng proposed that the density of the feathers on the back and the randomness of the patches elsewhere on the body indicated the animals would have been fully feathered in life, with the ventral
feathers having been removed by decomposition.
The filaments are preserved with a gap between the bones, which several authors have noted corresponds closely to the expected amount of skin and muscle tissue that would have been present in life. The feathers are closest to the bone on the skull and end of the tail, where little to no muscle was present, and the gap increases over the back vertebrae, where more musculature would be expected, indicating that the filaments were external to the skin and do not correspond with subcutaneous
structures.
The filaments exhibit random orientations and are often wavy, which has been interpreted as evidence that they were soft and pliable in life. Microscopic examination shows that individual filaments appear dark along the edges and light internally, suggesting that they were hollow, like modern feathers. Compared to modern mammals the filaments were quite coarse, with each individual strand much larger and thicker than the corresponding hair
s of similarly sized mammals.
The length of the filaments varies across the body. On the type specimen, they are shortest just in front of the eyes, with a length of 13 mm (0.511811023622047 in). Going further along the body, the filaments rapidly increase in length until reaching lengths of 35 mm (1.4 in) over the shoulder blades
. The length remains uniform over the back, until beyond the hips, when the filaments lengthen again and reach their maximum length midway down the tail at 40 mm (1.6 in). The filaments on the underside of the tail are shorter overall and decrease in length more rapidly than those on the dorsal surface. By the 25th tail vertebrae, the filaments on the underside reach a length of only 35 mm (1.4 in). The longest feathers present on the forearm measured 14 mm (0.551181102362205 in).
Though the feathers are too dense to isolate a single structure for examination, several studies have suggested the presence of two distinct filament types (thick and thin) interspersed with each other. The thick filaments tend to appear 'stiffer' than thin filaments, and the thin filaments tend to lie parallel to each other but at angles to nearby thick filaments. These properties suggest that the individual feathers consisted of a central quill (rachis) with thinner barbs branching off from it, similar to but more primitive in structure than modern bird feathers. Overall, the filaments most closely resemble the "plumules" or down-like feathers of some modern birds, with a thick central quill and long, thin barbs. The same structures are seen in other fossils from the Yixian Formation, including Confuciusornis
.
While Sinosauropteryx had feather-like structures, it was not very closely related to the previous "first bird" Archaeopteryx
. There are many dinosaur clade
s that were more closely related to Archaeopteryx than Sinosauropteryx was, including the deinonychosauria
ns, the oviraptorosauria
ns, and the therizinosaur
oids. This indicates that feathers may have been a characteristic of many theropod dinosaurs, not just the obviously bird-like ones, making it possible that equally distant animals such as Compsognathus
had feathers as well.
with dark colouration on its back and lighter colouration on its underside, with bands or stripes on the tail for camouflage.
Longrich's conclusions were supported in a paper first published online in the journal Nature in January 2010. Fucheng Zhang and colleagues examined the fossilized feathers of several dinosaurs and early birds, and found evidence that they preserved melanosome
s, the cells that give the feathers of modern birds their colour. Among the specimens studied was a previously undescribed specimen of Sinosauropteryx, IVPP V14202. By examining melanosome structure and distribution, Zhang and colleagues were able to confirm the presence of light and dark bands of colour in the tail feathers of Sinosauropteryx. Furthermore, the team was able to compare melanosome types to those of modern birds to determine a general range of colour. From the presence of phaeomelanosomes, spherical melanosomes that make and store red pigment, they concluded that the darker feathers of Sinosauropteryx were chestnut or reddish brown in colour.
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 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...
outside of Avialae
Avialae
Avialae is a clade of dinosaurs containing their only living representatives, birds , and the most immediate extinct relatives of birds.-Competing definitions:...
(birds and their immediate relatives) to be found with evidence of feather
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...
s. They were covered with "furry" coats of very simple filament-like feathers. Structures that indicate colouration have been preserved for some of the feathers, which also makes Sinosauropteryx the first non-avialian dinosaurs where colouration has been determined. Colouration includes a banded tail with reddish and light bands. Some contention has arisen with an alternative interpretation of the filamentous impression as remains of collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
fibres.
Sinosauropteryx were 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...
s with unusually long tails and short arms. They were close relatives of the similar but older genus Compsognathus
Compsognathus
Compsognathus was a small, bipedal, carnivorous theropod dinosaur. The animal was the size of a turkey and lived around 150 million years ago, the early Tithonian stage of the late Jurassic Period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany...
, both genera belonging to the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Compsognathidae
Compsognathidae
Compsognathidae is a family of small carnivorous dinosaurs, generally conservative in form, from the Jurassic and Cretaceous Periods. Compsognathids lie at or near the origin of feathers—skin impressions are known from four genera, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator...
. Only one 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...
of Sinosauropteryx has been named: S. prima, meaning "first" in reference to its status as the first feathered non-avialian dinosaur species discovered. A handful of specimens have been described. One specimen previously assigned to this genus represents either a second, as-yet unnamed species or a related genus.
Sinosauropteryx prima lived in what is now northeastern China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
during the early 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...
period. They were among the first dinosaurs discovered from the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
in Liaoning Province, and were members of the remarkable Jehol Biota
Jehol Biota
The Jehol Biota includes all the living organisms - the ecosystem - of northeastern China between 133 to 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. It is also believed to have left fossils in the Sinuiju series...
. Well-preserved fossils of this species illustrate many aspects of their biology, such as their diet and reproduction.
Description
Holotype
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...
specimen measuring only 68 cm (26.8 in) in length, including the tail. This individual was relatively young. The longest known specimen reaches up to 1.07 m (3.5 ft) in length, with an estimated weight of 0.55 kg (1.2 lb).
Sinosauropteryx were anatomically similar to Compsognathus, differing from their European relatives in their proportions. The skulls of Sinosauropteryx were 15% longer than their thigh bones
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, unlike Compsognathus, in which the skulls and thigh bones are approximately equivalent in length. The arms of Sinosauropteryx (humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
and radius
Radius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
) were only 30% the length of their legs (thigh bone and shin
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....
), compared to 40% in Compsognathus. Additionally, Sinosauropteryx had several features unique among all other theropods. S. prima had 64 vertebrae in their tails. This high number helps give them the longest tails relative to body length of any theropod species. Their hands were long compared to its arms, about 84% to 91% of the length of the rest of the arm (humerus and radius), and half the length of the foot. The first and second digits were about the same length, with a large claw on the first digit. The first fingers were large, being both longer and thicker than either of the bones of the forearm. The teeth differed slightly
Heterodont
The anatomical term heterodont refers to animals which possess more than a single tooth morphology. For example, members of the Synapsida generally possess incisors, canines , premolars, and molars. The presence of heterodont dentition is evidence of some degree of feeding/hunting specialization...
based on position: those near the tips of the upper jaws (on the premaxilla
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
e) were slender and lacked serrations, while those behind them (on the maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
e) were serrated and laterally compressed. The teeth of the lower jaws were similarly differentiated.
A pigmented area in the abdomen of the holotype has been suggested as possible traces of organs, and was interpreted as the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
by John Ruben and colleagues, which they described as part of a crocodilia
Crocodilia
Crocodilia is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period . They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria...
n-like "hepatic piston" respiratory system. A later study, while agreeing that the pigmented area represented something originally inside the body, found no defined structure and noted that any organs would have been distorted by the processes that flattened the skeleton into an essentially two-dimensional form. Dark pigment is also present in the eye region of the holotype and another specimen.
Three specimens have been assigned to Sinosauropteryx prima: the holotype GMV
Geological Museum of China
The Geological Museum of China , built in 1916, is a geological museum, boasting 200 thousand specimens.This museum is located in the Xisi area of Beijing and opened on October 1, 1959. It is the earliest geological scientific museum of China....
2123 (and its counter slab
Counter slab
Counter slab and slab are the matching halves of a fossil-bearing matrix formed in sedimentary deposits. When excavated the matrix may be split along the natural grain or cleavage of the rock. A fossil embedded in the sediment may then also split down the middle, with fossil remains sticking to...
[opposite face], NIGP 127586), NIGP 127587, and D 2141. Another specimen, IVPP
Institute of Vertebrate Paleontology and Paleoanthropology
The Institute of Vertebrate Paleontology and Paleoanthropology of China is a prominent research institution and collections repository for fossils, including many dinosaur and pterosaurand cat poo specimens...
V14202, was assigned to the genus but not to a species by Zhang and colleagues. The assignment of an additional larger specimen to S. prima, GMV
Geological Museum of China
The Geological Museum of China , built in 1916, is a geological museum, boasting 200 thousand specimens.This museum is located in the Xisi area of Beijing and opened on October 1, 1959. It is the earliest geological scientific museum of China....
2124, was later found to be in error. All of the fossils were found in the Jianshangou or Dawangzhangzi Beds of the Yixian Formation
Yixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
in the Beipiao
Beipiao
Beipiao is a city in Chaoyang prefecture, Liaoning province, in Northeast China. It has a population of 202,807. The main industry in the area is coal mining. With vertical shafts of almost 1000m, these are some of the deepest coal mines in China. The coal produced is used for coking...
and Lingyuan
Lingyuan, Liaoning
Lingyuan is a city in the west of Liaoning province in Northeast China, bordering Hebei province and Inner Mongolia. It is under the administration of Chaoyang City, which lies to the east-northeast.-Administrative Divisions:...
regions of Liaoning
Liaoning
' is a province of the People's Republic of China, located in the northeast of the country. Its one-character abbreviation is "辽" , a name taken from the Liao River that flows through the province. "Níng" means "peace"...
, China. These fossil beds have been dated to 124.6–122 million years ago, during the late Barremian
Barremian
The Barremian is an age in the geologic timescale between 130.0 ± 1.5 Ma and 125.0 ± 1.0 Ma). It is a subdivision of the Early Cretaceous epoch...
to early Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
stages of 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...
.
Classification
Despite its feathers, most palaeontologists do not consider Sinosauropteryx to be birds. PhylogeneticallyPhylogenetics
In biology, phylogenetics is the study of evolutionary relatedness among groups of organisms , which is discovered through molecular sequencing data and morphological data matrices...
, the genus is only distantly related to the clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
Aves, usually defined as Archaeopteryx lithographica plus modern birds. The scientists who described Sinosauropteryx, however, used a character-based, or apomorphic, definition of the Class
Class (biology)
In biological classification, class is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, order, family, genus, and species, with class fitting between phylum and order...
Aves, in which any animal with feathers is considered to be a bird. They argued that the filamentous plumes of Sinosauropteryx represent true feathers with a rachis
Rachis
Rachis is a biological term for a main axis or "shaft".-In zoology:In vertebrates a rachis can refer to the series of articulated vertebrae, which encase the spinal cord. In this case the rachis usually form the supporting axis of the body and is then called the spine or vertebral column...
and barbs, and thus that Sinosauropteryx should be considered a true bird. They classified the genus as belonging to a new biological order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
, Sinosauropterygiformes, family Sinosauropterygidae, within the subclass Sauriurae
Sauriurae
Sauriurae is a now-deprecated subclass of birds created by Ernst Haeckel in 1866. It was intended to include Archaeopteryx and distinguish it from all other birds then known, which he grouped in the sister-group Ornithurae...
. These proposals have not been accepted, and Sinosauropteryx is generally classified in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Compsognathidae
Compsognathidae
Compsognathidae is a family of small carnivorous dinosaurs, generally conservative in form, from the Jurassic and Cretaceous Periods. Compsognathids lie at or near the origin of feathers—skin impressions are known from four genera, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator...
, a group of small-bodied long-tailed coelurosauria
Coelurosauria
Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. In the past, it was used to refer to all small theropods, although this classification has been abolished...
n theropods known from the 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...
and 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 Asia, Europe, and South America.
There is only one named species of Sinosauropteryx, S. prima. A possible second species is represented by the specimen GMV 2124 (aka NGMC 2124), which was described as another, larger specimen of S. prima by Ji and Ji in 1997. However, in a 2002 presentation and abstract for the Society of Vertebrate Paleontology
Society of Vertebrate Paleontology
The Society of Vertebrate Paleontology was founded in 1940 for individuals with an interest in vertebrate paleontology. SVP now has almost 2,000 members. The society's website states that SVP "is organized exclusively for educational and scientific purposes...
, Nick Longrich showed that this specimen differs in several anatomical aspects from the others, including its relatively large size, proportionally longer shins, and shorter tail. Longrich suggested that GMV 2124 was a compsognathid coelurosaurian, while Sinosauropteryx proper was a more primitive kind of coelurosaurian or even a basal
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:...
carnosauria
Carnosauria
Carnosauria is a group of large predatory dinosaurs that lived during the Jurassic and Cretaceous periods. While it originally contained a wide assortment of giant theropods that were not closely related, the group has since been defined to encompass only the allosaurs and their closest kin...
n. In 2007, Gishlick and Gauthier concurred that this specimen was probably a new taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
, and tentatively re-classified it as Sinosauropteryx? sp., though they suggested it may belong in a new genus. Also in 2007, Ji, Ji and colleagues wrote that GMV 2124 is probably a new genus, noting the differences in tail length and hindlimb proportions.
History of discovery
Beijing
Beijing , also known as Peking , is the capital of the People's Republic of China and one of the most populous cities in the world, with a population of 19,612,368 as of 2010. The city is the country's political, cultural, and educational center, and home to the headquarters for most of China's...
, and the Nanjing
Nanjing
' is the capital of Jiangsu province in China and has a prominent place in Chinese history and culture, having been the capital of China on several occasions...
Institute of Geology and Paleontology. The director of the Beijing museum, Ji Qiang, recognized the importance of the find, as did visiting Canadian palaeontologist Phil Currie
Phil Currie
Philip John Currie, AOE is a Canadian palaeontologist and museum curator who helped found the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta and is now a professor at the University of Alberta in Edmonton...
and artist Michael Skrepnick, who became aware of the fossil by chance as they explored the Beijing museum's collections after leading a fossil tour of the area during the first week of October, 1996. Currie recognized the significance of the fossil immediately. As The New York Times quoted him, "When I saw this slab of silt stone
Siltstone
Siltstone is a sedimentary rock which has a grain size in the silt range, finer than sandstone and coarser than claystones.- Description :As its name implies, it is primarily composed of silt sized particles, defined as grains 1/16 - 1/256 mm or 4 to 8 on the Krumbein phi scale...
mixed with volcanic ash in which the creature is embedded, I was bowled over."
Chinese authorities initially barred photographs of the specimen from publication. However, Currie brought a photograph to the 1996 meeting of the Society of Vertebrate Paleontology
Society of Vertebrate Paleontology
The Society of Vertebrate Paleontology was founded in 1940 for individuals with an interest in vertebrate paleontology. SVP now has almost 2,000 members. The society's website states that SVP "is organized exclusively for educational and scientific purposes...
at the American Museum of Natural History
American Museum of Natural History
The American Museum of Natural History , located on the Upper West Side of Manhattan in New York City, United States, is one of the largest and most celebrated museums in the world...
in New York, causing crowds of palaeontologists to gather and discuss the new discovery. The news reportedly left palaeontologist John Ostrom
John Ostrom
John H. Ostrom was an American paleontologist who revolutionized modern understanding of dinosaurs in the 1960s, when he demonstrated that dinosaurs are more like big non-flying birds than they are like lizards , an idea first proposed by Thomas Henry Huxley in the 1860s, but which had garnered...
, who in the 1970s had pioneered the theory that birds evolved from dinosaurs, "in a state of shock." Ostrom later joined an international team of researchers who gathered in Beijing to examine the fossils; other team members included feather expert Alan Brush, fossil bird expert Larry Martin
Larry Martin
Larry 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...
, and Peter Wellnhofer
Peter Wellnhofer
Peter Wellnhofer is a German paleontologist at the "Bayerische Staatssammlung fur Paläontologie" in Munich. He is best known for his work on the various fossil specimens of Archaeopteryx or "Urvogel", the first known bird...
, an expert on the early bird Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
.
Controversy
Controversy regarding the identity of the filaments preserved in the first Sinosauropteryx specimen began almost immediately, as the team of scientists spent three days in Beijing examining the specimen under a microscope. The results of their studies (reported during a press conference at the Philadelphia Academy of Natural SciencesAcademy of Natural Sciences
The Academy of Natural Sciences of Drexel University, formerly Academy of Natural Sciences of Philadelphia, is the oldest natural science research institution and museum in the New World...
on Thursday, April 24, 1997) were inconclusive; the team agreed that the structures preserved on Sinosauropteryx were not modern feathers, but suggested further research was required to discover their exact nature. Palaeontologist Alan Feduccia
Alan Feduccia
Alan Feduccia is a paleornithologist, specializing in the origins and phylogeny of birds. He is now Professor Emeritus at the University of North Carolina. Feduccia's principal authored works include two books, The Age of Birds and The Origin and Evolution of Birds, and numerous papers in various...
, who had not yet examined the specimen, wrote in Audubon Magazine that the structures of Sinosauropteryx (which he considered at the time to be a synonym of Compsognathus, as Compsognathus prima) were stiffening structures from a frill running along the back, and that dinosaur palaeontologists were engaging in wishful thinking when equating the structures with feathers. Subsequent publications saw some of the team members disagreeing over the identity of the structures.
Feduccia's frill argument was followed up in several other publications, in which researchers interpreted the filamentous impressions around Sinosauropteryx fossils as remains of collagen
Collagen
Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...
fibres rather than primitive feathers. Since the structures are clearly external to the body, these researchers have proposed that the fibres formed a frill on the back of the animal and underside of its tail, similar to some modern aquatic lizards. The absence of feathers would refute the proposal that Sinosauropteryx is the most basal
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:...
known theropod genus with feathers, and also raise questions about the current theory of feather origins itself. It calls into question the idea that the first feathers evolved not for flight
Flight
Flight is the process by which an object moves either through an atmosphere or beyond it by generating lift or propulsive thrust, or aerostatically using buoyancy, or by simple ballistic movement....
but for insulation, and that they made their first appearance in relatively basal dinosaur lineages that later evolved into modern birds.
Most researchers have disagreed with the identification of the structures as collagen or other structural fibres. Notably, the team of scientists that reported the presence of pigmentation cells in the structures argued that their presence proved the structures were feathers, not collagen, because collagen does not contain pigment. Gregory S. Paul
Gregory S. Paul
Gregory Scott Paul is a freelance researcher, author and illustrator who works in paleontology, and more recently has examined sociology and theology. He is best known for his work and research on theropod dinosaurs and his detailed illustrations, both live and skeletal...
reidentified what the collagen hypothesis's proponents consider a body outline outside of the fibres as an artefact of preparation: breakage and brushed-on sealant have been misidentified as the outline of the body.
Palaeoecology
Sinosauropteryx, as a Yixian FormationYixian Formation
The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that spans 11 million years during the early Cretaceous period...
dinosaur, is a member of the Jehol Biota
Jehol Biota
The Jehol Biota includes all the living organisms - the ecosystem - of northeastern China between 133 to 120 million years ago. This is the Lower Cretaceous ecosystem which left fossils in the Yixian Formation and Jiufotang Formation. It is also believed to have left fossils in the Sinuiju series...
, the assemblage of organisms found in the Yixian Formation and overlying Jiufotang Formation
Jiufotang Formation
The Jiufotang Formation is an Early Cretaceous geological formation in Chaoyang, Liaoning which has yielded fossils of feathered dinosaurs, primitive birds, pterosaurs, and other organisms. . It is a member of the Jehol group. The exact age of the Jiufotang has been debated for years, with...
. The Yixian Formation is composed largely of volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...
s such as andesite
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
and basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
. Between the volcanic layers are several beds of sedimentary rock
Sedimentary rock
Sedimentary rock are types of rock that are formed by the deposition of material at the Earth's surface and within bodies of water. Sedimentation is the collective name for processes that cause mineral and/or organic particles to settle and accumulate or minerals to precipitate from a solution....
s representing deposition in a lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...
. The freshwater lake strata of the Yixian Formation have preserved a wide variety of plants, invertebrates, and vertebrates. Gymnosperm
Gymnosperm
The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...
forests were extensive, with a few early flowering plants as well. Ostracod
Ostracod
Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance. Some 65,000 species have been identified, grouped into several orders....
s and insects were diverse, and bivalves and gastropods were abundant. Mammals and birds are also well-known from the formation. The setting was subject to periodic mortality events including volcanic eruptions, wildfire
Wildfire
A wildfire is any uncontrolled fire in combustible vegetation that occurs in the countryside or a wilderness area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same...
s, and noxious gases erupting from the lakes
Limnic eruption
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which carbon dioxide suddenly erupts from deep lake water, suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists...
. The climate has been interpreted as temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally relatively moderate, rather than extreme hot or cold...
, with distinct wet and dry seasons. The yearly temperature during this time period averaged about 10 degrees celsius
Celsius
Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(50 degrees Fahrenheit
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
), indicating a temperate climate with unusually cold winters for the generally warm Mesozoic era, possibly due to northern China's high latitude during this time.
Diet
Lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...
in its gut region, indicating that small, fast-moving animals made up part of the diet of Sinosauropteryx prima. Numerous lizards of this type have been found in the same rocks as Sinosauropteryx, but have yet to be described.
The possible Sinosauropteryx specimen GMV 2124 (Sinosauropteryx? sp.) was found with three mammal jaws in its gut region. Hurum, Luo, and Kielan-Jaworowska (2006) identified two of these jaws as belonging to Zhangheotherium
Zhangheotherium
Zhangheotherium is a genus of symmetrodont, an extinct order of mammals. Previously known from only the tall pointed crowned teeth, Zhangheotherium, described from Liaoning Province, China, fossils in 1997, is the first symmetrodont known from a complete skeleton. It was dated to between 145-125...
and the third to Sinobaatar
Sinobaatar
Sinobaatar is a genus of extinct mammal from the Lower Cretaceous of China. It is categorized within the also extinct order Multituberculata and among these it belongs to the plagiaulacid lineage . Sinobaatar was a small herbivore during the Mesozoic era, commonly called "the age of the dinosaurs"....
, showing that these two mammals were part of the animal's diet. Interestingly, Zhangheotherium is known to have had a spur on the ankle, like the modern platypus
Platypus
The platypus is a semi-aquatic mammal endemic to eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth to live young...
, which would indicate that Sinosauropteryx fed on possibly venomous mammals.
Reproduction
The same specimen of S. prima which had preserved a lizard in its stomach contents (NIGP 127587) also had several small eggsEgg (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...
in its abdomen. Two eggs were preserved just in front of and above the pubic
Pubis (bone)
In vertebrates, the pubic bone is the ventral and anterior of the three principal bones composing either half of the pelvis.It is covered by a layer of fat, which is covered by the mons pubis....
boot, and several more may lie underneath them on the slab. It is unlikely that they were eaten by the animal, as they are in the wrong part of the body cavity for the egg shells to have remained intact. It is more likely that they are unlaid eggs produced by the animal itself. Each egg measured 36 mm (1.4 in) long by 26 mm (1 in) wide. The presence of two developed eggs suggests that Sinosauropteryx had dual oviduct
Oviduct
In non-mammalian vertebrates, the passageway from the ovaries to the outside of the body is known as the oviduct. The eggs travel along the oviduct. These eggs will either be fertilized by sperm to become a zygote, or will degenerate in the body...
s and laid eggs in pairs, like other theropods.
Feathers
All described specimens of Sinosauropteryx preserve integumentary structures (filaments arising from the skin) which most palaeontologists interpret as very primitive featherFeather
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...
s. These short, down-like filaments are preserved along the back half of the skull, arms, neck, back, and top and bottom of the tail. Additional patches of feathers have been identified on the sides of the body, and palaeontologists Chen, Dong and Zheng proposed that the density of the feathers on the back and the randomness of the patches elsewhere on the body indicated the animals would have been fully feathered in life, with the ventral
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...
feathers having been removed by decomposition.
Subcutaneous tissue
The hypodermis, also called the hypoderm, subcutaneous tissue, or superficial fascia is the lowermost layer of the integumentary system in vertebrates. Types of cells that are found in the hypodermis are fibroblasts, adipose cells, and macrophages...
structures.
The filaments exhibit random orientations and are often wavy, which has been interpreted as evidence that they were soft and pliable in life. Microscopic examination shows that individual filaments appear dark along the edges and light internally, suggesting that they were hollow, like modern feathers. Compared to modern mammals the filaments were quite coarse, with each individual strand much larger and thicker than the corresponding hair
Hair
Hair is a filamentous biomaterial, that grows from follicles found in the dermis. Found exclusively in mammals, hair is one of the defining characteristics of the mammalian class....
s of similarly sized mammals.
The length of the filaments varies across the body. On the type specimen, they are shortest just in front of the eyes, with a length of 13 mm (0.511811023622047 in). Going further along the body, the filaments rapidly increase in length until reaching lengths of 35 mm (1.4 in) over the shoulder blades
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
. The length remains uniform over the back, until beyond the hips, when the filaments lengthen again and reach their maximum length midway down the tail at 40 mm (1.6 in). The filaments on the underside of the tail are shorter overall and decrease in length more rapidly than those on the dorsal surface. By the 25th tail vertebrae, the filaments on the underside reach a length of only 35 mm (1.4 in). The longest feathers present on the forearm measured 14 mm (0.551181102362205 in).
Though the feathers are too dense to isolate a single structure for examination, several studies have suggested the presence of two distinct filament types (thick and thin) interspersed with each other. The thick filaments tend to appear 'stiffer' than thin filaments, and the thin filaments tend to lie parallel to each other but at angles to nearby thick filaments. These properties suggest that the individual feathers consisted of a central quill (rachis) with thinner barbs branching off from it, similar to but more primitive in structure than modern bird feathers. Overall, the filaments most closely resemble the "plumules" or down-like feathers of some modern birds, with a thick central quill and long, thin barbs. The same structures are seen in other fossils from the Yixian Formation, including Confuciusornis
Confuciusornis
Confuciusornis is a genus of primitive crow-sized birds from the Early Cretaceous Yixian and Jiufotang Formations of China, dating from 125 to 120 million years ago...
.
While Sinosauropteryx had feather-like structures, it was not very closely related to the previous "first bird" Archaeopteryx
Archaeopteryx
Archaeopteryx , sometimes referred to by its German name Urvogel , is a genus of theropod dinosaur that is closely related to birds. The name derives from the Ancient Greek meaning "ancient", and , meaning "feather" or "wing"...
. There are many dinosaur clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
s that were more closely related to Archaeopteryx than Sinosauropteryx was, including the deinonychosauria
Deinonychosauria
The Deinonychosauria were a clade of coelurosaurian theropod dinosaurs from the Late Jurassic and Cretaceous periods. These omnivores and carnivores are known for their switchblade-like second toe claws and for displaying numerous bird-like characteristics. The clade has been divided into two...
ns, the oviraptorosauria
Oviraptorosauria
Oviraptorosaurs are a group of feathered maniraptoran dinosaurs from the Cretaceous Period of what are now Asia and North America. They are distinct for their characteristically short, beaked, parrot - like skulls, with or without bony crests atop the head...
ns, and the therizinosaur
Therizinosaur
Therizinosaurs are theropod dinosaurs belonging to the clade Therizinosauria. Therizinosaur fossils have been found in Early through Late Cretaceous deposits in Mongolia, the People's Republic of China and Western North America...
oids. This indicates that feathers may have been a characteristic of many theropod dinosaurs, not just the obviously bird-like ones, making it possible that equally distant animals such as Compsognathus
Compsognathus
Compsognathus was a small, bipedal, carnivorous theropod dinosaur. The animal was the size of a turkey and lived around 150 million years ago, the early Tithonian stage of the late Jurassic Period, in what is now Europe. Paleontologists have found two well-preserved fossils, one in Germany...
had feathers as well.
Colouration
Sinosauropteryx was the first dinosaur to have its life colouration described by scientists based on physical evidence. Some fossils of Sinosauropteryx show an alternation of lighter and darker bands preserved on the tail. Chen and colleagues initially interpreted this banding pattern as an artifact of the splitting between the main slab and counter-slab in which the original specimen was preserved. However, Longrich suggested in his 2002 presentation for the Society of Vertebrate Paleontology that these specimens actually preserve remnants of the colouration pattern the animal would have exhibited in life. He argued that the dark, banded areas on the tail were too evenly spaced to have been caused by random separation of the fossil slabs, and that they represent fossilized pigments present in the feathers. Additionally, rather than an artifact of preservation or decomposition, the presence of dark feathers along only the top of the body may also reflect the colour pattern in life, indicating that Sinosauropteryx prima was countershadedCountershading
Countershading, or Thayer's Law, is a form of camouflage. Countershading, in which an animal’s pigmentation is darker dorsally, is often thought to have an adaptive effect of reducing conspicuous shadows cast on the ventral region of an animal’s body...
with dark colouration on its back and lighter colouration on its underside, with bands or stripes on the tail for camouflage.
Longrich's conclusions were supported in a paper first published online in the journal Nature in January 2010. Fucheng Zhang and colleagues examined the fossilized feathers of several dinosaurs and early birds, and found evidence that they preserved melanosome
Melanosome
In a biological cell, a melanosome is an organelle containing melanin, the most common light-absorbing pigment found in the animal kingdom.Cells that synthesize melanins are called melanocytes, and also the retinal pigment epithelium cells, whereas cells that have merely engulfed the melanosomes...
s, the cells that give the feathers of modern birds their colour. Among the specimens studied was a previously undescribed specimen of Sinosauropteryx, IVPP V14202. By examining melanosome structure and distribution, Zhang and colleagues were able to confirm the presence of light and dark bands of colour in the tail feathers of Sinosauropteryx. Furthermore, the team was able to compare melanosome types to those of modern birds to determine a general range of colour. From the presence of phaeomelanosomes, spherical melanosomes that make and store red pigment, they concluded that the darker feathers of Sinosauropteryx were chestnut or reddish brown in colour.
External links
- Sinosauropteryx prima in The Theropod Database