Scipionyx
Scipionyx | |
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Holotype specimen, Museo Civico di Storia Naturale di Milano | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Clade: | Dinosauria |
Clade: | Saurischia |
Clade: | Theropoda |
Genus: | †Scipionyx dal Sasso & Signore, 1998 |
Species: | †S. samniticus
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Binomial name | |
†Scipionyx samniticus Dal Sasso & Signore, 1998
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Scipionyx (
There is only one fossil known of Scipionyx, discovered in 1981 by an amateur paleontologist and brought to the attention of science in 1993. In 1998 the type species 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.[3] 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 that was most likely a baby[3] only half a metre (twenty inches) long and perhaps just three days old. Its adult form and 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. 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
History of discovery and naming
Scipionyx was discovered in the spring of 1981 by Giovanni Todesco, an amateur
In 1993 Teruzzi and Leonardi scientifically reported the find,[5] which generated some publicity as it was the very first dinosaur found in Italy.[6] The popular magazine Oggi simultaneously nicknamed the animal Ciro, a typical Neapolitan boy's name, an idea by chief-editor Pino Aprile.[1] In 1994 Leonardi published a larger article about the discovery.[7] In 1995 Marco Signore of the University of Naples Federico II[4] submitted a thesis containing a lengthy description of the fossil, in which he named it "Dromaeodaimon irene".[8] 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, when the type species Scipionyx samniticus was named and described by Marco Signore and Cristiano Dal Sasso.[9] 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,[4] the 18th century geologist who wrote the first description of the formation in which the fossil was found and Scipio Africanus, the famous Roman consul fighting Hannibal. The specific name samniticus means "From Samnium", the Latin name of the region around Pietraroja. Several other names had been considered but rejected, such as "Italosaurus", "Italoraptor" and "Microraptor".[10] The last name has since been used for a genus of "four-winged" dromaeosaurid discovered in China a few years later.
The holotype, 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.[11]
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 by dal Sasso and Simone Maganuco published in 2011,[2] 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.[12] Later, in 2024, Cau published a new paper that recovered Scipionyx in a polytomy with Wiehenvenator, Iberospinus, and the rest of Spinosauridae.[13]
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 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 of 23.7 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.[2]
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.[2]
Diagnostic traits
The 2011 study established eight unique derived traits or
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
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.[2]
Scipionyx has five teeth in the premaxilla, seven in the maxilla and ten in the
Postcrania
The vertebral column 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.[2]
The vertebrae of the back are not pneumatised. They are
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. 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.[2]
The
In the pelvis the
Of the hindlimb, the lower leg is missing. The femur 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 has only a weak cnemial crest, separated from its outer condyle by a deep narrow groove, the incisura tibialis. The fibula is broad on top but has a slender shaft.[2]
Soft tissues
The holotype preserves an exceptionally large set of soft tissues for a fossil dinosaur. Although some muscle tissue (Santanaraptor, Pelecanimimus), cartilage (Juravenator, Aucasaurus[14]) or an intestine (Mirischia, Daurlong) 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.[2]
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.[2]
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.[2]
Ligaments and cartilage
From the ninth cervical vertebra to the back, the vertebral joints show the remains of
Respiratory system
Of the
Liver, heart, spleen and thymus
In the front part of the
Another organ in the thorax, traces of which might be present, is the thymus, which might have contributed to a greyish mass of organic origin visible in the neck base; this also contains connective and muscle tissue.[2]
Digestive system
The
Just behind the presumed position of the stomach a very conspicuous large and thick intestine is visible, that has been identified as the
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 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.[2]
Muscle tissue
At several places on the fossil
In the grey organic mass at the neck base, muscle fibres are present that have been identified as belonging to the
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.[2]
Integument
The fossil preserves no traces of any skin, scales or feathers. In 1999 Philip J. Currie 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.[2]
Phylogeny
Scipionyx was by the describers assigned to the
This cladogram shows the position of Scipionyx in the coelurosaurian tree, according to the 2011 study:
Tyrannoraptora
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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, Scipionyx and Sciurumimus, 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 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. An abbreviated version of the phylogeny recovered by Cau is shown below with putative compognathids in bold.[15]
Here is a simplified version of Cau (2024), with Scipionyx in bold.
Tetanurae |
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Paleobiology
Habitat
The location where Scipionyx was found, in the Albian was part of the
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.[2]
Land animals actually found in the Pietraroja deposits are all small. They include the
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.[2]
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
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.[2]
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
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.[4] 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.[2]
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
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.[2]
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 e.a. inferred that Scipionyx had a respiratory system different from birds, and more similar to crocodiles, based on an analysis of pictures of the fossil which seemed to indicate the presence of a diaphragm. 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 birds, whose lungs are ventilated by air-sacs, are coelurosaurian theropods, and an indication theropods were cold-blooded.[17]
John Ruben's conclusions have, however, been questioned by some scientists, such as Lawrence Witmer, who claimed the study to be flawed.[18] 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.[2]
The empty space between the pubic bones and the intestines has by G.S. Paul and David Martill been hypothesised to have been the location of a large air-sac. Dal Sasso & Maganuco however, rejected this interpretation because with living birds the air-sac of the posterior abdomen does not force the intestines forwards. They considered the space more likely to have been filled by a large yolk-sac. Air-sacs were nevertheless probable given the pneumatisation of the vertebrae. Vertebrae without pneumatopores would have indicated the boundaries between three air-sac systems: those of the neck base, the lungs, and the abdomen. The double rib heads would indicate a rather stiff thorax, ventilated by the gastralia. A system of hook-like uncinate processes on the ribs as with the Maniraptoriformes, allowing the ribcage to move flexibly, in articulation with an ossified sternum, was absent in Scipionyx.[2]
Growth
The holotype of Scipionyx is a rare example of a non-avian theropod hatchling; the most important other very young specimens are the chicks of Byronosaurus that however are much less complete. The young age is reflected by the proportions and the low degree of ossification and fusion of several skeletal elements. The most obvious youthful trait is the relatively large and short head.[2]
Dal Sasso & Maganuco have tried to determine the absolute age of the hatchling. The fact that the fontanelle had not closed yet, poses an upper age limit of about five weeks. An even lower limit is indicated by the lack of any tooth replacement, which with Archosauria begins after a few weeks at the latest. The most exact age is given by the size of the yolk sac, which indicates a probable age of three days, with an upper limit of a week. Despite its very young age, the hatchling was able to walk, as is shown by the complete ossification of the ilium. However, this does not imply Scipionyx was
References
- ^ a b Holtz, Thomas R. Jr. (2011) Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap 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
- ^ ISSN 1097-5721.
- ^ a b c d e Poling, Jeff (1998). "Skippy the dinosaur". Journal of Dinosaur Paleontology. Archived from the original on 2007-02-04. Retrieved 2007-03-01.
- ^ Leonardi, G. & Teruzzi, G., 1993, "Prima segnalazione di uno scheletro fossile di dinosauro (Theropoda, Coelurosauria) in Italia (Cretacico di Pietraroia, Benevento)", Paleocronache 1993: 7-14
- ^ Dal Sasso, C. and Signore, M., 1998, "Scipionyx samniticus (Saurischia, Theropoda): the first Italian dinosaur", Third European Workshop on Vertebrate Paleontology, Abstract: 23
- ^ Leonardi, G. & Avanzini, M., 1994, "Dinosauri in Italia", Le Scienze (Quaderni), 76: 69-81
- ^ Signore, M., 1995, Il teropode del Plattenkalk della Civita di Pietraroia (Cretaceo inferiore, Bn). Thesis, Dip. Paleont. Univ. Napoli "Federico II"
- ^ Dal Sasso, C. and Signore, M. (1998). "Exceptional soft tissue preservation in a theropod dinosaur from Italy." Nature, 392: 383-387.
- ^ Cristiano Dal Sasso & Giuseppe Brillante, 2001, Dinosauri italiani, Marsilio pp 256
- ^ Dal Sasso, C. and Signore, M., 1998, "Scipionyx samniticus (Theropoda: Coelurosauria) and its exceptionally well preserved internal organs", Journal of Vertebrate Paleontology 18 (3): 37A
- ^ Cau, Andrea (2021). "Comments on the Mesozoic theropod dinosaurs from Italy". Atti della Società dei Naturalisti e Matematici di Modena. 152: 81–95.
- .
- ^ Carrano, M.T. & Sampson S.D. 2008. "The phylogeny of Ceratosauria". Journal of Systematic Palaeontology 6(2): 183-236
- ^ "Comments on the Mesozoic theropod dinosaurs from Italy". ResearchGate. Retrieved 2021-12-28.
- PMID 9915693
- ^ Browne, Malcolm W (26 January 1999), "Spectacular fossil reveals dinosaur soft part anatomy and supports cold-blooded dinos not related to birds", New York Times