Scipionyx

with, immediately above it, the Le Cavere quarry Scipionyx was discovered in the spring of 1981 by Giovanni Todesco, an amateur paleontologist, in the small Le Cavere quarry at the edge of the village of Pietraroja, approximately seventy kilometers northeast of Naples. 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. In 1994 Leonardi published a larger article about the discovery. In 1995 Marco Signore of the University of Naples Federico II Because the thesis was unpublished this remained an invalid nomen ex dissertatione.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. 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, 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". 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. 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, 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. Later, in 2024, Cau published a new paper that recovered Scipionyx in a polytomy with Wiehenvenator, Iberospinus, and the rest of Spinosauridae. == Description ==

Size The holotype of Scipionyx represents a very small individual, the preserved length of which is estimated at just . In 2011, dal Sasso and Maganuco estimated its total length, including the missing tail section, at . The specimen was not much smaller than known embryos or hatchlings of Lourinhanosaurus 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, which itself measures in length. As the hatchling would have fitted within an egg about long and wide, this would have implied a rather high egg size compared to the adult body length.) 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. 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 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 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 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 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, 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, hydrated iron oxide, a likely transformation product of the original haemoglobin. Also biliverdine was present, a bile component expected in the liver. The blood might also partly have originated from the heart and the spleen, 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, 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 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-secreting proventriculus preceding a muscular gizzard. Gastroliths 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. It is preserved partly in the form of a natural endocast, partly as a petrification still showing the cellular structure, including the mucosa and connective tissue. Some mesenteric 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. 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 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 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. 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 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 of the myotomes, the segments of the Musculus iliocaudalis or the Musculus ischiocaudalis. 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 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. == 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. }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} Here is a simplified version of Cau (2024), with Scipionyx in bold. == Paleobiology ==

Habitat The location where Scipionyx was found, in the Albian was part of the Apulian Plate, at the time largely covered by the shallow Paratethys. Some dry land was present however, but it is uncertain how extensive or connected the several terranes 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. 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. Parts of the windpipe, intestines, John Ruben'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 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. 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. 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 precocial as even with altricial birds this pelvis bone fully ossifies within a few days after hatching. == References ==