Scipionyx
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''Scipionyx'' ( ) was a
genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...
of theropod
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
from the Early
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
of
Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...
, around 113
million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago). ...
. There is only one
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
known of ''Scipionyx'', discovered in 1981 by an amateur paleontologist and brought to the attention of science in 1993. In 1998 the
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
''Scipionyx samniticus'' was named, the generic name meaning "Scipio's claw". The find generated much publicity because of the unique preservation of large areas of petrified soft tissue and internal organs such as muscles and intestines. The fossil shows many details of these, even the internal structure of some muscle and bone cells. It was also the first dinosaur found in Italy. Because of the importance of the specimen, it has been intensely studied. The fossil is that of a juvenile only half a metre (twenty inches) long and perhaps just three days old. Its adult size is unknown. ''Scipionyx'' was a bipedal predator, its horizontal rump balanced by a long tail. Its body was probably covered by primitive feathers but these have not been found in the fossil, that is without any skin remains. In the guts of the fossil some half-digested meals are still present, indicating ''Scipionyx'' ate lizards and fish. Perhaps these had been fed to the young animal by its parents. Several scientists have tried to learn from the position of the internal organs how ''Scipionyx'' breathed, but their conclusions often disagree. The classification of ''Scipionyx'' is uncertain, due to the difficulties of classifying a taxon known only from such a young specimen. Most paleontologists have classified it as a member of Compsognathidae, a family of small
coelurosaurs Coelurosauria (; from Greek, meaning "hollow tailed lizards") is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs. Coelurosauria is a subgroup of theropod dinosaurs that includes compsognathids, tyrann ...
, but the paleontologist Andrea Cau has proposed it may belong to Carcharodontosauridae, a family of large carnosaurs.


History of discovery and naming

''Scipionyx'' was discovered in the spring of 1981 by Giovanni Todesco, an amateur
paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
, in the small ''Le Cavere'' quarry at the edge of the village of
Pietraroja Pietraroja is a mountain ''comune'' (municipality) in the province of Benevento in Campania, southern Italy. It is approximately 50 km by car from Benevento, in direction north-west, 83 km from Naples in direction north-east and appr ...
, approximately seventy kilometers northeast of
Naples Naples (; it, Napoli ; nap, Napule ), from grc, Νεάπολις, Neápolis, lit=new city. is the regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 909,048 within the city's adminis ...
. The specimen was preserved in the marine
Pietraroja Formation The Pietraroia Plattenkalk is a Cretaceous geologic formation located in the Italian municipality of Pietraroja,
, well known for unusually well-conserved fossils. Todesco thought the remains belonged to an extinct bird. He prepared the strange discovery in the basement of his house in
San Giovanni Ilarione San Giovanni Ilarione is a ''comune'' (municipality) in the Province of Verona in the Italian region Veneto, located about west of Venice and about northeast of Verona. San Giovanni Ilarione borders the following municipalities: Cazzano di Tra ...
near
Verona Verona ( , ; vec, Verona or ) is a city on the Adige River in Veneto, Northern Italy, Italy, with 258,031 inhabitants. It is one of the seven provincial capitals of the region. It is the largest city Comune, municipality in the region and the ...
, removing, without the use of any optical instrument, part of the chalk matrix from the top of the bones and covering them with vinyl glue. He strengthened the stone plate by adding pieces to its rim and on one of these he added a fake tail made from polyester resin as that of the fossil was largely lacking because he had failed to recover it completely. In early 1993 Todesco, who had nicknamed the animal ''cagnolino'', "little doggie", after its toothy jaws, brought the specimen to the attention of paleontologist Giorgio Teruzzi of the '' Museo Civico di Storia Naturale di Milano'', who identified it as the juvenile of a theropod dinosaur and nicknamed it ''Ambrogio'' after the
patron saint A patron saint, patroness saint, patron hallow or heavenly protector is a saint who in Catholicism, Anglicanism, or Eastern Orthodoxy is regarded as the heavenly advocate of a nation, place, craft, activity, class, clan, family, or perso ...
of
Milan Milan ( , , Lombard: ; it, Milano ) is a city in northern Italy, capital of Lombardy, and the second-most populous city proper in Italy after Rome. The city proper has a population of about 1.4 million, while its metropolitan city h ...
,
Ambrose Ambrose of Milan ( la, Aurelius Ambrosius; ), venerated as Saint Ambrose, ; lmo, Sant Ambroeus . was a theologian and statesman who served as Bishop of Milan from 374 to 397. He expressed himself prominently as a public figure, fiercely promo ...
. Not being an expert in the field of dinosaur studies himself, he called in the help of colleague Father
Giuseppe Leonardi Giuseppe Leonardi (born 31 July 1996) is an Italian sprinter, selected to be part of the Italian athletics team for the Tokyo 2020 Olympics, as a possible member of the relay team A relay race is a racing competition where members of a team ...
. In Italy such finds are by law State property and Todesco was convinced by science reporter Franco Capone to report the discovery to the authorities: on 15 October 1993 Todesco personally delivered the fossil to the Archaeological Directorship at Naples. The specimen was added to the collection of the regional ''Soprintendenza per i Beni Archeologici di Salerno, Avellino, Benevento e Caserta'' in
Salerno Salerno (, , ; nap, label= Salernitano, Saliernë, ) is an ancient city and ''comune'' in Campania (southwestern Italy) and is the capital of the namesake province, being the second largest city in the region by number of inhabitants, after ...
, to which it officially still belongs; on 19 April 2002 it was given its own display at the '' Museo Archeologico di Benevento''. In 1993 Teruzzi and Leonardi scientifically reported the find, which generated some publicity as it was the very first dinosaur found in Italy. The popular magazine '' Oggi'' simultaneously nicknamed the animal ''Ciro'', a typical Neapolitan boy's name, an idea by chief-editor Pino Aprile.Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages.'' In 1994 Leonardi published a larger article about the discovery. In 1995 Marco Signore of the University of Naples Federico II submitted a
thesis A thesis ( : theses), or dissertation (abbreviated diss.), is a document submitted in support of candidature for an academic degree or professional qualification presenting the author's research and findings.International Standard ISO 7144: ...
containing a lengthy description of the fossil, in which he named it "Dromaeodaimon irene". Because the thesis was unpublished this remained an invalid ''nomen ex dissertatione''. Meanwhile, in Salerno, Sergio Rampinelli had begun a further preparation of the fossil, during three hundred hours of work removing the fake tail, replacing the vinyl glue with a modern resin preservative and finishing the uncovering of the bones. On this occasion it was discovered that large parts of the soft tissues had been preserved. In 1998, ''Ciro'' because of this made the front cover of ''
Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...
'', when the
type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...
''Scipionyx samniticus'' was named and described by Marco Signore and
Cristiano Dal Sasso Cristiano Dal Sasso (born 12 September 1965) is an Italian paleontologist. Biography He was born in Monza, Italy and has been working since 1991 for the Milan Natural History Museum where he is the curator of fossil reptiles and birds. He was ...
. The generic name ''Scipionyx'' comes from the Latin name ''Scipio'' and the Greek ὄνυξ, ''onyx'', the combination meaning "Scipio's claw". "Scipio" refers to both
Scipione Breislak Scipione Breislak (1748 – 15 February 1826), Italy, Italian geologist of Sweden, Swedish parentage, was born in Rome in 1748. He distinguished himself as a professor of mathematical and mechanical philosophy in the college of Ragusa, Italy, Ra ...
, the 18th century geologist who wrote the first description of the formation in which the fossil was found and
Scipio Africanus Publius Cornelius Scipio Africanus (, , ; 236/235–183 BC) was a Roman general and statesman, most notable as one of the main architects of Rome's victory against Carthage in the Second Punic War. Often regarded as one of the best military com ...
, the famous Roman
consul Consul (abbrev. ''cos.''; Latin plural ''consules'') was the title of one of the two chief magistrates of the Roman Republic, and subsequently also an important title under the Roman Empire. The title was used in other European city-states throug ...
fighting
Hannibal Hannibal (; xpu, 𐤇𐤍𐤁𐤏𐤋, ''Ḥannibaʿl''; 247 – between 183 and 181 BC) was a Carthaginian general and statesman who commanded the forces of Carthage in their battle against the Roman Republic during the Second Puni ...
. The
specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...
''samniticus'' means "From
Samnium Samnium ( it, Sannio) is a Latin exonym for a region of Southern Italy anciently inhabited by the Samnites. Their own endonyms were ''Safinim'' for the country (attested in one inscription and one coin legend) and ''Safineis'' for the The lan ...
", the Latin name of the region around Pietraroja. Several other names had been considered but rejected, such as "Italosaurus", "Italoraptor" and "Microraptor". The last name has since been used for a genus of "four-winged" dromaeosaurid discovered in China a few years later. The
holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
, SBA-SA 163760, dates from the early Albian, about 110 million years old, and consists of an almost complete skeleton of a juvenile individual, lacking only the end of the tail, the lower legs and the claw of the right second finger. Extensive soft tissues have been preserved but no parts of the skin or any integument such as scales or feathers. In view of the exceptional importance of the find, between December 2005 and October 2008 the fossil was intensively studied in Milan resulting in a
monograph A monograph is a specialist work of writing (in contrast to reference works) or exhibition on a single subject or an aspect of a subject, often by a single author or artist, and usually on a scholarly subject. In library cataloging, ''monograph ...
by dal Sasso and
Simone Maganuco Simone may refer to: * Simone (given name), a feminine (or Italian masculine) given name of Hebrew origin * Simone (surname), an Italian surname Simone may also refer to: * ''Simone'' (1918 film), a French silent drama film * ''Simone'' (1926 fi ...
published in 2011,Cristiano dal Sasso & Simone Maganuco, 2011, '' ''Scipionyx samniticus'' (Theropoda: Compsognathidae) from the Lower Cretaceous of Italy — Osteology, ontogenetic assessment, phylogeny, soft tissue anatomy, taphonomy and palaeobiology'', Memorie della Società Italiana de Scienze Naturali e del Museo Civico di Storia Naturale di Milano XXXVII(I): 1-281 containing the most extensive description of a single dinosaur species ever. In 2021, the Italian paleontologist Andrea Cau proposed that the holotype of ''Scipionyx'' is a hatchling carcharodontosaur.


Description


Size

The holotype of ''Scipionyx'' represents a very small individual, the preserved length being just 237 millimetres. In 2011 dal Sasso & Maganuco estimated its total length, including the missing tail section, at 461 millimetres. The specimen was not much smaller than known embryos or hatchlings of ''
Lourinhasaurus ''Lourinhasaurus'' (meaning "Lourinhã lizard") was an herbivorous sauropod dinosaur genus dating from Late Jurassic strata of Estremadura Province (historical), Estremadura, Portugal. Discovery The first find in 1949 by Harold Weston Robbins, ...
'' and '' Allosaurus'', theropods of considerable magnitude. However, given its affinities with the Compsognathidae, it is likely that the adult size of ''Scipionyx'' did not surpass that of the largest known compsognathid, ''
Sinocalliopteryx ''Sinocalliopteryx'' (meaning 'Chinese beautiful feather') is a genus of carnivorous compsognathid theropod dinosaurs from the Lower Cretaceous Yixian Formation of China (Jianshangou Beds, dating to 124.6 Ma). While similar to the related ''Huax ...
'' of 237 centimetres length. As the hatchling would have fitted within an egg about eleven centimetres long and six centimetres wide, this would have implied a rather high egg size compared to the adult body length.


General build

Because the holotype is a hatchling of perhaps only a few days old, it is hard to determine the build of the adult animal but some general conclusions can be reliably made. ''Scipionyx'' was a small bipedal predator. Its horizontal rump was balanced by a long tail. The neck was relatively long and slender. The hindlimbs and especially the forelimbs were rather elongated. Dal Sasso & Maganuco considered it likely that a coat of primitive protofeathers was present, as these are also known from some direct relatives.


Diagnostic traits

The 2011 study established eight unique derived traits or autapomorphies in which ''Scipionyx'' differed from its closest relatives. The praemaxilla has five teeth. Where the parietal and the
frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...
bone make contact, the depression in which the
supratemporal fenestra The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
, a skull roof opening, was present, shows a sinuous ridge on the postorbital. The lower branch of the squamosal has a rectangular end. The wrist consists of just two, superimposed, bones: a radial and a lower element formed by a fusion of the first and second carpal. This last element has the shape of a lens, not a crescent; is flattened; and is fused seamlessly. The first finger is conspicuously elongated, 23% longer than the third finger. The notch in the front edge of the ilium is directed to the front and only weakly developed. The front edge of the
ischium The ischium () form ...
shaft has a long obturator process with a rectangular end.


Skull

The skull of the holotype is large, compared to the size of the body, and short with very large eye-sockets. This is largely due to its young age. Accordingly, the semi-circular antorbital fenestra, the normally largest skull opening, is short too and smaller than the eye-socket. In front of it two smaller openings are present: the maxillary and promaxillary. The snout is pointed with a low rounded tip. The
premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...
, the bone forming the front of the snout, carries five teeth. The
maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...
behind it, is deep with a very short front branch. It carries seven teeth. The depression in its surface for the antorbital opening is bounded by a ridge. The lacrimal is robust and lacks a horn; its side is not pierced by a foramen. The prefrontal is exceptionally large, forming a large part of the front upper edge of the eye-socket. The
frontal Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front'', 1976 film Music *The Front (band), an American rock band signed to Columbia Records and active in the 1980s and ea ...
bones have a transverse ridge at their back. Between the frontals and the parietals the skull roof over a limited distance has not closed yet, resulting in a conspicuous diamond-shaped opening, a
fontanelle A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allow f ...
that was first mistaken for damage inflicted on the fossil during the first preparation. On its inner side the supratemporal fenestra has no depression, being bounded by a high edge of the parietal. The jugal has no front vertical branch towards the lacrimal. The quadrate bone has on its front edge a large wing-like expansion, touching the pterygoid. The bones of the braincase are largely inaccessible but a small inner ear opening, the ''recessus tympanicus dorsalis'', is visible. The underside of the braincase lacks an inflated part or ''bulla''. The lower jaw is straight and elongated. The jaw bone is rather low: the specimen creates the illusion of a strong jaw because the left jaw is visible below the right one. It bears ten teeth. In the 1998 description a part of the splenial was mistaken for a supradentarium and the angular was misidentified as the surangular because in the fossil it had been displaced upwards, creating the false impression an external mandibular fenestra, an opening in the outer side of the jaw, would be present. ''Scipionyx'' has five teeth in the premaxilla, seven in the maxilla and ten in the dentary of the lower jaw for a total of twenty-two per side and a grand total for the head of forty-four. The number of five premaxillary teeth is surprising, as a total of four is normal for compsognathids: otherwise, only some Carnosauria have five. Due to the young age of the specimen, the tooth replacement cycle had not started yet, causing a perfect dental symmetry between the left and the right jaws. The teeth lack the typical compsognathid shape with a suddenly recurving apex of the tooth crown. Instead, in general they curve gradually; only the largest teeth show something of a "kink". Exceptionally, the tooth row of the lower jaw extends further to the back than that of the upper jaw. The premaxillary teeth are pointed and lack denticles. The first four have an oval cross-section; the fifth is more flattened near its apex. The second and fifth teeth are the largest. The maxillary teeth are flattened with denticles on their trailing edges. The second and fourth maxillary teeth are the largest; the latter being the largest tooth of all. Of the ten teeth of the lower jaw, the first two are rather straight with an oval cross-section and lack denticles. The third tooth has denticles at its base and a flatter top; the other seven are more recurved and flattened along their entire height; gradually the denticles reach the apex.


Postcrania

The
vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordata, ...
of ''Scipionyx'' probably includes ten cervical vertebrae and thirteen dorsal vertebrae; due to the fact the specimen is just a hatchling, the differentiation between the two categories has not fully developed, making any distinction rather arbitrary. With certainty five sacral vertebrae are present. The fossil has preserved just nine tail vertebrae; likely fifty or more had been originally present. The neck vertebrae are opisthocoelous. The axis is pneumatised as a pneumatopore, an opening through which a diverticulum of the air sack of the neck base could reach its hollow interior, is visible on its side. The third, fourth and fifth vertebrae also show pneumatopores but the consecutive series lacks them, which is surprising as it had been assumed the pneumatisation process would have started at the back, working itself forward. Contrary to what was stated by the 1998 study, the cervical ribs are very elongated, with a length of up to three vertebral centra. The vertebrae of the back are not pneumatised. They are amphiplatyan with an oval cross-section and bear low spines with a hexagonal profile. Just below the top of the spine on the front and back edge a small beak-shaped process is present. In 1998 interpreted as a reduced
hyposphene The hyposphene-hypantrum articulation is an accessory joint found in the vertebrae of several fossil reptiles of the group Archosauromorpha. It consists of a process on the backside of the vertebrae, the hyposphene, that fits in a depression in the ...
-
hypantrum The hyposphene-hypantrum articulation is an accessory joint found in the vertebrae of several fossil reptiles of the group Archosauromorpha. It consists of a process on the backside of the vertebrae, the hyposphene, that fits in a depression in the ...
complex, a system of secondary vertebral joints shown by many theropods, it was by the 2011 study seen as a pair of attachment points for tendons, as identified in 2006 in ''Compsognathus''. Exceptionally, with the thirteenth vertebra the two rib joint processes, the parapophysis and the diapophysis, are positioned at the same level. The five sacral vertebrae have not yet fused into a real
sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...
. The tail vertebrae are platycoelous with low spines and backward slanting chevrons. There are at least twelve pairs of dorsal ribs; some displaced elements might represent a thirteenth pair. The third and fourth rib have expanded lower ends that in life probably were attached to cartilaginous sternal ribs, themselves connected to sterna that in the holotype specimen have not (yet) ossified. The lower rump is covered by a basket of eighteen pairs of gastralia or belly ribs. Mysterious shaft parts present near the forelimbs are by Dal Sasso & Maganuco interpreted as the remains of a nineteenth frontmost element consisting of two completely fused shafts homologous to the normal medial elements of a pair of gastralia; such a chevron-like bone has also been reported with ''
Juravenator ''Juravenator'' is a genus of small (75 cm long) coelurosaurian theropod dinosaur (although a 2020 study proposed it to be a hatchling megalosauroid), which lived in the area which would someday become the top of the Franconian Jura of Germa ...
''. The gastralia form a herringbone pattern, the left and right medial elements overlapping each other at their forked ends in order that the basket can expand and contract to accommodate the breathing movements of the abdomen. The
scapula The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eithe ...
is relatively straight and about six to seven times longer than wide; its upper end is missing. Its lower end is connected to a semicircular coracoid. The furcula is broad and more or less U-shaped with its two branches angled at 125°. The forelimb is rather long; its length is equal to 48% of the body length in front of the pelvis. Especially the hand is elongated as is typical for compsognathids; for a member of that group ''Scipionyx'' has a relatively short hand, however. The
humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
is straight with a moderately developed deltopectoral crest. The
ulna The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
is slender and cylinder-shaped with a length of 70% of that of the humerus. The wrist consists of two elements only: a radial bone capping the lower end of the
radius In classical geometry, a radius ( : radii) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
and a disc-shaped bone below it; this is either the enlarged first lower carpal or a perfect seamless fusion of the first and second lower carpal. The
metacarpus In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...
is compact and moderately elongated. Its three elements mirror the shape of the fingers they bear: the first is the shortest en thickest; the second the longest; and the third is intermediate in length and thickness. The third finger is exceptionally long for a comspognathid, with 123% of thumb length. As the lower joint of the first metacarpal is bevelled, the thumb diverges medially. Its claw is no larger than that of the second finger. The hand claws are moderately curved. In the pelvis the ilium is short and flat with a slightly convex upper profile. The back end is rectangular, the front edge has an appending hook-shaped point and near its top a circular notch, a trait that is usually considered a synapomorphy of the
Tyrannosauroidea Tyrannosauroidea (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent b ...
. The pubic bone points almost vertically downwards and is thus "mesopubic" or "orthopubic". It is relatively short with about two thirds of the length of the femur. It has a short "foot" shaped like a golf club. The
ischium The ischium () form ...
has three quarters the length of the pubis, set at an angle of 54° to it. It ends in a small expansion. On the front of its shaft a large hatchet-shaped obturator process is present, the attachment for the '' Musculus puboischiofemoralis externus'', that lacks a small circular notch between its lower edge and the shaft, though this lack is normally associated with the possession of a lower triangular ''processus obturatorius''. Of the hindlimb, the lower leg is missing. The
femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
or thigh bone is straight and robust. The lesser trochanter is markedly lower than the greater trochanter and separated from it by a narrow cleft. It has the shape of a wing-like expansion to the front. An accessory or posterior trochanter is lacking; likewise a fourth trochanter on the back shaft is absent. The
tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
has only a weak cnemial crest, separated from its outer condyle by a deep narrow groove, the ''incisura tibialis''. The
fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...
is broad on top but has a slender shaft.


Soft tissues

The holotype preserves an exceptionally large set of soft tissues for a fossil dinosaur. Although some muscle tissue (''
Santanaraptor ''Santanaraptor'' (meaning "Santana Formation thief") is a genus of Tyrannosauroidea, tyrannosauroid Theropoda, theropod dinosaur that lived in South America during the Early Cretaceous (late Aptian-early Albian), about 112 million years ago. Di ...
'', ''
Pelecanimimus ''Pelecanimimus'' (meaning "pelican mimic") is an extinct genus of basal ("primitive") ornithomimosaurian dinosaur from the Early Cretaceous of Spain. It is notable for possessing more teeth than any other member of the Ornithomimosauria (or an ...
''),
cartilage Cartilage is a resilient and smooth type of connective tissue. In tetrapods, it covers and protects the ends of long bones at the joints as articular cartilage, and is a structural component of many body parts including the rib cage, the neck an ...
(''
Juravenator ''Juravenator'' is a genus of small (75 cm long) coelurosaurian theropod dinosaur (although a 2020 study proposed it to be a hatchling megalosauroid), which lived in the area which would someday become the top of the Franconian Jura of Germa ...
'', ''
Aucasaurus ''Aucasaurus'' is a genus of medium-sized abelisaurid theropod dinosaur from Argentina that lived during the Late Cretaceous (Santonian to Campanian stage) of the Anacleto Formation. It was smaller than the related ''Carnotaurus'', although more ...
'') or an intestine (''
Mirischia ''Mirischia'' is a small (two meter-long) genus of compsognathid theropod dinosaur from the Albian stage ( Early Cretaceous Period) of Brazil. Discovery and naming In 2000 David Martill and Eberhard Frey reported the find of a small dinosaur ...
'', ''
Daurlong ''Daurlong'' (meaning " Daur dragon") is an extinct genus of dromaeosaurid dinosaur from the Early Cretaceous (Aptian) Longjiang Formation of China. The genus contains a single species, ''D. wangi'', known from a nearly complete skeleton. ''Daur ...
'') have been reported from other dinosaurs, ''Scipionyx'' is unique in preserving in some form examples from most major internal organ groups: blood, blood vessels, cartilage, connective tissues, bone tissue, muscle tissue, horn sheaths, the respiratory system and the digestive system. Nervous tissue and the external skin, including possible scales or feathers, are absent. The soft tissues are not present in the form of imprints but as three-dimensional petrifications, having been replaced by calcium phosphate in amazing detail, even to the subcellular level; or as transformed remains of the original biomolecular components.


Bone tissue

The original bone tissue is no longer present but the calcium phosphate mineralisation has preserved the structure of original bone cells, showing individual osteocytes including their inner hollow spaces and the ''canaliculi''. Also the internal blood vessels of the bone have been preserved, in some cases still empty inside. On some bones, including some of the skull and lower jaws, the periosteum is still visible.


Ligaments and cartilage

From the ninth cervical vertebra to the back, the vertebral joints show the remains of articular capsules. Between the spines at places very thin interspinal and supraspinal
ligaments A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the: * Peritoneal li ...
are visible. Six vertebrae are visibly capped by cartilaginous synchondroses, a typical juvenile feature. Cartilaginous caps are also present on all limb joints, even the smallest, and are especially thick in the shoulder, elbow and wrist joints. Also the pubic foot is capped and the ilium and pubic bone are separated by cartilage.


Respiratory system

Of the
respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
little has been preserved. No traces of the lungs have survived, nor of any air sacks. The sole element still present consists of a seven millimetre long piece of the
trachea The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...
of which about ten tracheal rings are visible, the most anterior of which are open at the top, giving them a C-shape. They have an average length of 0.33 millimetres and are separated by 0.17 millimetre thick interspaces. The trachea is quite thin, with a preserved width of one millimetre about half as wide as would be expected for an animal the size of the holotype, and positioned rather low in the neck base, embedded in connective tissue.


Liver, heart, spleen and thymus

In the front part of the
thorax The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the cre ...
a conspicuous red halo is visible, forming a roughly circular stain with a diameter of seventeen millimetres. In 1998 it was suggested this might represent the remains of the decayed
liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
, a blood-rich organ. That the red pigment was indeed derived from blood, was confirmed in 2011: a scanning electron microscope analysis indicated that the substance consisted of
limonite Limonite () is an iron ore consisting of a mixture of hydrated iron(III) oxide-hydroxides in varying composition. The generic formula is frequently written as FeO(OH)·H2O, although this is not entirely accurate as the ratio of oxide to hydroxid ...
, hydrated
iron oxide Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of whic ...
, a likely transformation product of the original haemoglobin. Also biliverdine was present, a
bile Bile (from Latin ''bilis''), or gall, is a dark-green-to-yellowish-brown fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is produced continuously by the liver (liver bile ...
component expected in the liver. The blood might also partly have originated from the
heart The heart is a muscular organ in most animals. This organ pumps blood through the blood vessels of the circulatory system. The pumped blood carries oxygen and nutrients to the body, while carrying metabolic waste such as carbon dioxide t ...
and the
spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .
, two similarly blood-rich organs, with reptiles positioned between the two lobes of the liver. Another organ in the thorax, traces of which might be present, is the
thymus The thymus is a specialized primary lymphoid organ of the immune system. Within the thymus, thymus cell lymphocytes or ''T cells'' mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. ...
, which might have contributed to a greyish mass of organic origin visible in the neck base; this also contains connective and muscle tissue.


Digestive system

The digestive tract can mostly be traced, either because the intestines are still present or by the presence of food items. The position of the
oesophagus The esophagus (American English) or oesophagus (British English; both ), non-technically known also as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the ...
is indicated by a five millimetre long series of small food particles. Below the ninth dorsal vertebra the location of the stomach is shown by a cluster of bones of prey animals, the organ itself likely having been dissolved by its own stomach acid shortly after death. The rather backward position of the cluster suggests the stomach was dual in structure, with a forward
enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
-secreting
proventriculus The proventriculus is part of the digestive system of birds.Encarta World English Dictionary orth American Edition(2007). ''Proventriculus''. Source: (accessed: December 18, 2007) An analogous organ exists in invertebrates and insects. Birds The ...
preceding a muscular gizzard.
Gastroliths A gastrolith, also called a stomach stone or gizzard stone, is a rock held inside a gastrointestinal tract. Gastroliths in some species are retained in the muscular gizzard and used to grind food in animals lacking suitable grinding teeth. In oth ...
have not been reported. Just behind the presumed position of the stomach a very conspicuous large and thick intestine is visible, that has been identified as the
duodenum The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
. It is preserved partly in the form of a natural endocast, partly as a petrification still showing the cellular structure, including the
mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...
and connective tissue. Some
mesenteric The mesentery is an organ that attaches the intestines to the posterior abdominal wall in humans and is formed by the double fold of peritoneum. It helps in storing fat and allowing blood vessels, lymphatics, and nerves to supply the intestines ...
blood vessels cover the intestine in the form of up to a centimetre long and 0.02 to 0.1 millimetre wide hollow tubes. The duodenum forms a large loop, the descending part of which first is directed downwards towards the gastralia and then runs to the back. There in a sharp bend, the folds of which are clearly visible, it turns to the front, proceeding as an ascending tract, its visible part ending near the stomach. At this point the tract is directed to the left of the body, perpendicular to the fossil slab, and its course can thus no longer be followed. Nearby and slightly above, a subsequent intestine part surfaces that has been interpreted as the jejunum. This thinner intestine turns to the back, running parallel to the ascending tract of the duodenum and ultimately disappearing under it, at the level of the twelfth dorsal vertebra. Apparently a loop to the front is made because it resurfaces below the tenth dorsal vertebra, first running upwards and then turning to the back below the hind vertebral column — or at places even over it: probably after death its position partly shifted upwards. The jejunum seems to blend with an exceptionally short ileum. A contraction below the thirteenth dorsal vertebra might indicate the transition to the
rectum The rectum is the final straight portion of the large intestine in humans and some other mammals, and the Gastrointestinal tract, gut in others. The adult human rectum is about long, and begins at the rectosigmoid junction (the end of the s ...
. A caecum seems absent. The rectum runs to the back between the upper shafts of the pubes and ischia. Then it bends downwards parallel to the ischium shaft, at the end of it turning upwards again. In this final part faeces are still present. The
cloaca In animal anatomy, a cloaca ( ), plural cloacae ( or ), is the posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles and birds, a ...
is lacking. Dal Sasso & Maganuco suggested the cloaca exit was rather low, at the level of the ischial feet and that a rectocoprodaeal valve separated faeces and urine. Between the front edge of the pubic shafts and the back of the intestines a large empty space is present. Also, the rectum seems to run in a very high position as if it were forced upwards by something. According to Dal Sasso & Maganuco, in life this space would have been filled by the
yolk sac The yolk sac is a membranous sac attached to an embryo, formed by cells of the hypoblast layer of the bilaminar embryonic disc. This is alternatively called the umbilical vesicle by the Terminologia Embryologica (TE), though ''yolk sac'' is far ...
of the hatchling; on hatching the juveniles of reptiles typically have not absorbed all the yolk and use the residual nutrients to supplement the food intake during their first weeks.


Muscle tissue

At several places on the fossil muscle tissue is present. The degree of preservation is often exceptional, with not only the individual fibres still discernible but also the individual cells and even the subcellular sarcomeres. Among dinosaur fossils such sarcomeres are only known from ''Santanaraptor'', whose muscle fibres are four times as thick. The original organic material has been replaced by small hollow globes, the walls of which consist of euhedric crystals of
apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...
. In the grey organic mass at the neck base, muscle fibres are present that have been identified as belonging to the '' Musculus sternohyoideus'' and the '' Musculus sternotrachealis''. Between the sixth and seventh dorsal vertebra a patch of muscle fibres is visible belonging to either the '' Musculus transversospinalis'' or the '' Musculus longissimus dorsi''. In front of the right ischium muscle fibres are present running from the ischial foot in the direction of the femur. Their identity is uncertain: they could belong to the '' Musculus puboischiofemoralis pars medialis'' (the ''Musculus adductor femoris I'' of crocodiles) but in that case this muscle with (some) non-avian theropods would not be anchored on the obturator process. The fibres could also represent an unknown muscle. In any case they refute a conjecture by Gregory S. Paul that there would be no muscle connection between the ischium and the femur at all. Above the rectum tract a large area of horizontal unsegmented muscle fibres is present, probably representing the unsegmented ''
Musculus caudofemoralis longus Musculus may refer to: *Andreas Musculus (1514–1581), German Lutheran theologian *Heinrich Musculus (b. 1868), Swedish-Norwegian businessperson *Wolfgang Musculus (1497–1563), German Reformed theologian *Musculus (bivalve), ''Musculus'' (bivalv ...
'' of the tail base, the main retractor muscle operating on the thighbone. These fibres are polygonal in cross-section and show the intercellular spaces also. Below some tail base vertebrae the connective ligaments between the chevrons are present, forming the ''ligmamentum interhaemale'', but also some small muscle fibres and some mysterious hollow tubes arranged in a herringbone pattern; the latter perhaps represent the
myosepta A myotome is the group of muscles that a single spinal nerve innervates. Similarly a dermatome is an area of skin that a single nerve innervates with sensory fibers. Myotomes are separated by myosepta (singular: myoseptum). In vertebrate embryon ...
of the myotomes, the segments of the '' Musculus iliocaudalis'' or the ''
Musculus ischiocaudalis Musculus may refer to: * Andreas Musculus (1514–1581), German Lutheran theologian *Heinrich Musculus (b. 1868), Swedish-Norwegian businessperson *Wolfgang Musculus Wolfgang Musculus, born "Müslin" or "Mauslein", (10 September 1497 – 30 Augus ...
''.


Horn sheaths

On all claws preserved in the fossil — those of the feet have all been lost — horn sheaths are visible. These have a darker colouration on top than on the bottom which suggests that the original horn material is still present — but this has not yet been directly tested by a chemical analysis for fear of damaging these delicate structures that were seen as forming an essential part of the integrity of the precious specimen. The horn sheaths of the hand claws extend the bony cores by about 40%, scythe-like continuing the bone curve and ending in sharp points. On some claws the sheaths have partly detached; on others they have been flattened or split.


Integument

The fossil preserves no traces of any skin, scales or feathers. In 1999
Philip J. Currie Philip John Currie (born March 13, 1949) 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. In the ...
hypothesised this might be otherwise, suggesting the tubes found on the tail base would represent the filaments of protofeathers. In 2011, however, Dal Sasso & Maganuco rejected this interpretation because the tubes taper at both ends, while integument filaments are expected to have only a tapered top end. Nevertheless, they considered it likely that ''Scipionyx'' in life had protofeathers as these are known to be present with the compsognathids '' Sinosauropteryx'' and ''
Sinocalliopteryx ''Sinocalliopteryx'' (meaning 'Chinese beautiful feather') is a genus of carnivorous compsognathid theropod dinosaurs from the Lower Cretaceous Yixian Formation of China (Jianshangou Beds, dating to 124.6 Ma). While similar to the related ''Huax ...
''.


Phylogeny

''Scipionyx'' was by the describers assigned to the Coelurosauria, a group of theropods. Because the only remains recovered belong to that of a juvenile, it has proven difficult to assign this dinosaur to a more specific group. One problem is that in the build of a juvenile animal the original traits of ancestor groups are more likely to be expressed, suggesting a too basal position in the evolutionary tree. Part of the 2011 monograph was a cladistic analysis which indicated that ''Scipionyx'' was a basal member of the Compsognathidae and the sister species of '' Orkoraptor''. Dal Sasso & Maganuco emphasised that, due to its limited remains, the position of ''Orkoraptor'' is tentative. This cladogram shows the position of ''Scipionyx'' in the coelurosaurian tree, according to the 2011 study: In 2021, a study proposed by Andrea Cau re-evaluated the classification of this specimen and the classification of compsognathids in general. According to Cau's study, compsognathids would be a "false clade" (a polyphyletic assemblage) and most of the ascribed genera would actually represent juvenile forms or chicks of other tetanuran theropod clades, stating that the same characteristics used to differentiate the group from other families of theropods, are actually the typical characteristics of the chicks of the large basal tetanurae. In his study, Cau proposes a new procedure to classify these animals, applying it to ''
Juravenator ''Juravenator'' is a genus of small (75 cm long) coelurosaurian theropod dinosaur (although a 2020 study proposed it to be a hatchling megalosauroid), which lived in the area which would someday become the top of the Franconian Jura of Germa ...
'', ''Scipionyx'' and ''
Sciurumimus ''Sciurumimus'' ("Squirrel-mimic," named for its tail's resemblance to that of the tree squirrel, ''Sciurus'') is an extinct genus of tetanuran theropod from the Late Jurassic of Germany. It is known from a single juvenile specimen representing t ...
'', obtaining a possible phylogenetic position that was not affected by the immaturity of the specimens. According to this new procedure, ''Juravenator'' and ''Sciurumimus'' turn out to be megalosauroids, while ''Scipionyx'' turns out to be a carcharodontosaurid. This interpretation would also be supported by the similarity of the
jaw The jaw is any opposable articulated structure at the entrance of the mouth, typically used for grasping and manipulating food. The term ''jaws'' is also broadly applied to the whole of the structures constituting the vault of the mouth and serv ...
of ''Scipionyx'' with that of an '' Allosaurus'' chick. Furthermore, this location would explain the size discrepancy between the ''Scipionyx'' type specimen and the estimated adult size for the presumed adult compsognathids, more in line with the size of the large carcharodontosaurids.


Paleobiology


Habitat

The location where ''Scipionyx'' was found, in the Albian was part of the
Apulian Plate The Adriatic or Apulian Plate is a small tectonic plate carrying primarily continental crust that broke away from the African Plate along a large transform fault in the Cretaceous period. The name Adriatic Plate is usually used when referring ...
, at the time largely covered by the shallow
Paratethys The Paratethys sea, Paratethys ocean, Paratethys realm or just Paratethys was a large shallow inland sea that stretched from the region north of the Alps over Central Europe to the Aral Sea in Central Asia. Paratethys was peculiar due to its pa ...
. Some dry land was present however, but it is uncertain how extensive or connected the several
terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its own ...
s were. The marine sediments of the Pietraroja ''Plattenkalk'' were probably deposited closely to a piece of the Apennine Platform, which piece possibly formed a small island between the present middle of Italy and
Tunisia ) , image_map = Tunisia location (orthographic projection).svg , map_caption = Location of Tunisia in northern Africa , image_map2 = , capital = Tunis , largest_city = capital , ...
. From this it has been concluded that the habitat of ''Scipionyx'' in general consisted of small islands and it represented one of the larger animals of its
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syste ...
. However, there are also indications that the terranes regularly interconnected to form far more extensive islands, land bridges allowing a dispersal of much larger animals, such as sauropods and large theropods. If so, they were not present for long when the land surface fragmented again, because there are no signs of insular dwarfism, a size reduction as an adaptation to decreased resources. Likewise, ''Scipionyx'' itself is no dwarf among its relatives. Due to its small absolute size, ''Scipionyx'' would have been able to maintain itself when the dry land shrank. Nevertheless, Dal Sasso & Maganuco did not consider ''Scipionyx'' to have been a permanent resident of small islands throughout tens of millions of years, but more likely a recent immigrant arriving during a dispersal wave, probably from North-Africa. They admitted this was at odds with their own phylogenetic analysis, showing ''Scipionyx'' to be a basal compsognathid, but they pointed out that the phylogeny found was uncertain due to the juvenile status of the fossil. Land animals actually found in the Pietraroja deposits are all small. They include the
lizards Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia althou ...
''
Chometokadmon ''Chometokadmon'' is an extinct genus of anguimorph lizard from the Early Cretaceous of Italy. The type and only species is ''Chometokadmon fitzingeri'', named by Italian zoologist Oronzio Gabriele Costa in 1864. It is known from only one speci ...
'' and '' Eichstaettisaurus gouldi'', a relative of the forty million years older German ''Eichstaettisaurus schroederi''; the
rhynchocephalian Rhynchocephalia (; ) is an order of lizard-like reptiles that includes only one living species, the tuatara (''Sphenodon punctatus'') of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a diverse gro ...
''
Derasmosaurus ''Derasmosaurus'' is an extinct species of rhynchocephalian known from the Pietraroja Plattenkalk of Italy. It was originally considered to be a specimen of ''Lacerta brevicauda'' by Costa in 1866, it was later considered a specimen of the l ...
'' and the
amphibian Amphibians are tetrapod, four-limbed and ectothermic vertebrates of the Class (biology), class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terres ...
'' Celtedens megacephalus''.


Food

The fossil provides direct information about the diet of ''Scipionyx'' because remains of a complete series of consecutive meals have been preserved, perhaps everything the animal ate during its short life. These confirm what already could be concluded from its phylogenetic affinities and general build: that ''Scipionyx'' was a predator. In the oesophagus tract about eight scales and some bone fragments are present. Dal Sasso & Maganuco considered it likely that these had not been swallowed as loose elements but were the remains of a meal, partly regurgitated from the stomach in the final death throes. In the stomach position itself, a cluster of small bones is visible. These include an ankle with a three millimetre wide metatarsus consisting of five metatarsals attached, a tail vertebra and the upper end of an ulna. If the remains represent a single prey animal, it is likely either a member of the
Mesoeucrocodylia Mesoeucrocodylia is the clade that includes Eusuchia and crocodyliforms formerly placed in the paraphyletic group Mesosuchia. The group appeared during the Early Jurassic, and continues to the present day. Diagnosis It was long known that M ...
or some
lepidosaurian The Lepidosauria (, from Greek meaning ''scaled lizards'') is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes snakes, lizards, and amphisbaenia, amphisbaenians. Squamata contains over 9, ...
lizard-like animal; the size indicates the last possibility. In the descending tract of the duodenum two clusters of lizard scales are present and, more below, a fish vertebra. The jejunum shows a cluster of dozens of fish vertebrae, likely having belonged to a member of the Clupeomorpha. A second cluster of vertebrae was found at the jejunum-ileum boundary. The final tract of the rectum still holds faeces in which a piece of skin is visible showing seventeen scales of a fish of the Osteoglossiformes that was nine seasons old, judging from the growth lines on the scales. The food items found allow to reconstruct a sequence of food intakes: first a four to five centimetres long fish; secondly a smaller fish of two to three centimetres; next a ten to twelve centimetres long lizard; then a fifteen to forty, depending on the identification, centimetres long lepidosaurian lizard; and finally some indeterminate vertebrate(s). Together they represent a varied diet showing that ''Scipionyx'' was an opportunistic generalist. That swift lizards had been caught and sea fish washed ashore had been gathered necessitating a prolonged patrolling of the flood line, both indicate a good mobility. If the prey animal in the stomach really was forty centimetres long, it is highly unlikely that the equally-sized hatchling had been able to subdue it, indicating parental care.


Physiology

''Scipionyx'' is considered one of the most important fossil vertebrates ever discovered, after a long and painstaking "autopsy" revealed the unique fossilisation of portions of its internal organs. It is believed ''Scipionyx'' lived in a region filled with shallow
lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') a ...
s. These bodies of water were oxygen deficient, leading to the well-preserved ''Scipionyx'' specimen, much like the fine fossil preservation seen in Germany's ''
Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
''.Reisdorf, A.G., and Wuttke, M. (2012). "Re-evaluating Moodie's Opisthotonic-Posture Hypothesis in fossil vertebrates. Part I: Reptiles – The taphonomy of the bipedal dinosaurs ''Compsognathus longipes'' and ''Juravenator starki'' from the Solnhofen Archipelago (Jurassic, Germany)." ''Palaeobiodiversity and Palaeoenvironments'', Parts of the
windpipe The trachea, also known as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the la ...
,
intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...
s,
liver The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
, blood vessels, cartilage, horn sheaths, tendons and muscles were fossilised in the fine limestone. The specimen's liver was preserved in the form of a red
hematite Hematite (), also spelled as haematite, is a common iron oxide compound with the formula, Fe2O3 and is widely found in rocks and soils. Hematite crystals belong to the rhombohedral lattice system which is designated the alpha polymorph of . ...
halo retaining the shape it had when the animal was alive. The find has great importance because the relative positions of internal organs of dinosaurs could only be guessed at before this discovery. The holotype specimen thus provides unique direct information about the
physiology Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
of non-avian dinosaurs, especially regarding the digestion, the respiration and the ontogenesis.


Digestion

The digestive tract of ''Scipionyx'' is generally short but wide. The overall length of the intestines — shorter than what was expected — indicates ''Scipionyx'' could process food very efficiently. The efficiency would be improved by the visible intestine folds, the ''plicae circulares'', enlarging the absorption surface. Dal Sasso & Maganuco emphasised that a short tract does not necessarily imply that the processing time was short too; retention could have been prolonged to optimise digestion. Most extant vertebrate predators are capable of extracting about 75% of the energetic value of the prey flesh. The bones in the stomach region had not been etched by the stomach acid, indicating this meal was less than a day old. It is possible that the stomach exit was too narrow to let these remains pass and that the acid was used to extract
calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to ...
from the bones, a much-needed nutrient for a young growing animal. The subsequent digestive tract with most extant vertebrates is incapable of further digesting bones. Afterwards the remains would then have been regurgitated. However, the presence of vertebrae in the intestines suggests that the exit was wide and that non-avian theropods in this respect were more like present
Lepidosauromorpha Lepidosauromorpha (in PhyloCode known as ''Pan-Lepidosauria'') is a group of reptiles comprising all diapsids closer to lizards than to archosaurs (which include crocodiles and birds). The only living sub-group is the Lepidosauria, which contains ...
than extant Archosauria who regurgitate. This is also confirmed by a high bone content in the
coprolite A coprolite (also known as a coprolith) is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour (in this case, diet) rather than morphology. The name is de ...
s of large theropods. Fish contains much calcium and it is possible that the hatchling instinctively sought it out; alternatively, it could have been preferentially fed fish by its parents. The presence of skin in the faeces was to be expected as this is not easily digested. The body parts of the large lepidosaurian in the stomach had been made more digestible by biting them into pieces. According to Dal Sasso & Maganuco the hatchling would certainly have been incapable of achieving this and they considered it a strong indication of parental care as it was improbable the animal had by chance encountered a carcass neatly ripped apart into easily swallowed bits by predators or scavengers.


Respiration

Although most of the respiratory system has not been preserved, some far-reaching conclusions have been drawn from the indirect evidence available. In 1999
John Ruben John A. Ruben is a researcher in Zoology and Vertebrate paleontology at the Oregon State University in Corvallis. Much of his published research is focused on studying the respiratory system in birds, in order to contradict the theory of theropod ...
e.a. inferred that ''Scipionyx'' had a
respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
different from
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s, and more similar to
crocodile Crocodiles (family (biology), family Crocodylidae) or true crocodiles are large semiaquatic reptiles that live throughout the tropics in Africa, Asia, the Americas and Australia. The term crocodile is sometimes used even more loosely to inclu ...
s, based on an analysis of pictures of the
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
which seemed to indicate the presence of a
diaphragm Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...
. The large liver would have completely divided the body cavity into an anterior section for the heart and lungs and a posterior section for the intestines. This would have indicated the presence of septate lungs, ventilated by a hepatic-piston diaphragm, driven by the liver and a '' Musculus diaphragmaticus'', which in the fossil was visibly attached to the pubes. Such a system would be an argument against the idea that
bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweigh ...
s, whose lungs are ventilated by air-sacs, are coelurosaurian theropods, and an indication theropods were cold-blooded.
John Ruben John A. Ruben is a researcher in Zoology and Vertebrate paleontology at the Oregon State University in Corvallis. Much of his published research is focused on studying the respiratory system in birds, in order to contradict the theory of theropod ...
's conclusions have, however, been questioned by some scientists, such as Lawrence Witmer, who claimed the study to be flawed. The 2011 study concluded that due to the fact that the liver had been preserved as a vague halo, representing body fluids that after death might have covered a larger surface than the organs they originated from, its exact dimensions and extent cannot be determined. In any case a diaphragm itself or its position could not be directly observed. Many bird livers are large too, showing that such a trait is compatible with an air-sac system. The small body cavity in front of the halo seemed to indicate the presence of small stiff bird-like lungs. The presumed ''M. diaphragmaticus'' was shown to be an artifact caused by the polishing and engraving of calcite nodules of non-organic origin during preparation, creating the illusion of muscle fibres. The empty space between the pubic bones and the intestines has by G.S. Paul and
David Martill {{Short pages monitor