| Silesaurus Temporal range: Late Triassic, | |
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| Reconstructed skeleton | |
Scientific classification  | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dracohors |
| Family: | † Silesauridae |
| Clade: | † Sulcimentisauria |
| Genus: | † Silesaurus Dzik, 2003 |
| Species | |
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Silesaurus is a genus of silesaurid dinosauriform from the Late Triassic, of what is now Poland.
Fossilized remains of Silesaurus have been found in the Keuper Claystone in Krasiejów near Opole, Silesia, Poland, which is also the origin of its name. The type species, Silesaurus opolensis, was described by Jerzy Dzik in 2003. It is known from some 20 skeletons, making it one of the best-represented species of early dinosauriformes. [1]
Silesaurus measured approximately 2.3 meters (7.5 feet) in length. Lightly built, it was probably a fast and agile animal with an active lifestyle. The snout was narrow with forward-pointing nostrils, and the large orbits likely provided Silesaurus with acute vision.
Initially, Silesaurus was thought to be strictly herbivorous, but later research on coprolite contents indicates that it may have been insectivorous, [2] feeding on insects such as the beetle Triamyxa . The teeth of the animal were small, conical, and serrated, and were distributed irregularly in its jaws. The tip of the dentary had no teeth, and evidence suggests that it was covered by a keratinous beak. [1]
Scientists think that Silesaurus was not a dinosaur, but rather a dinosauriform. Dinosaurian features lacking in Silesaurus include an enlarged deltopectoral crest (a muscle attachment on the humerus), and epipophyses (enlarged tendon attachment above the postzygapophysis) on the cervical vertebrae.
However, Silesaurus has some dinosaurian characteristics as well:
As a result, alternative hypotheses place Silesaurus at or near the base of the ornithischian dinosaurs. Other scientists propose a basal link between the basal sauropodomorphs and ornithischians. [1]
Systematic position after Nesbitt (2011): [3]
| Ornithodira |
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Herbivory has been suggested for silesaurids in general and Silesaurus in particular based on tooth shape, and a 2014 study by the paleontologists Tai Kubo and Mugino O. Kubo of microwear on its teeth found it consistent with herbivory on soft objects, by comparing with wear on the teeth of extant mammals, though omnivory could not be ruled out. [4]
A 2019 study by paleontologist Martin Qvarnström and colleagues examining coprolites (fossil dung) that contained beetles attributed them to Silesaurus based on size and other factors. These researchers suggested that while Silesaurus could exploit plant resources, it was not strictly a plant-eater. They pointed out that the teeth of Silesaurus were not numerous or regularly spaced, and lacked the coarse serrations typical in herbivores. They hypothesized that the beak-like jaws were adapted for pecking small insects off the ground like modern birds. They cautioned that there could have been other food sources that were not preserved in the coprolites, such as soft prey, plant fragments, and larger, more resistant items that were regurgitated, and that beetles could have been a seasonal food item. If so, this would represent the earliest known occurrence of this highly derived mode of feeding and have implications for the understanding of the evolutionary adaptations that would eventually lead up to the origin of dinosaurs. [5]
Silesaurus and silesaurids in general have been considered quadrupedal due to their long, gracile forelimbs. In 2010, the paleontologists Rafał Piechowski and Jerzy Dzik considered such proportions typical of fast-running, quadrupedal animals, but noted that the long tail of Silesaurus which would have acted as a counterweight to the body, as well as the very gracile forelimbs, indicates it retained the ability for fast bipedal running. [6] Piechowski and the paleontologist Mateusz Tałanda concluded in 2020 that the short hindlimbs combined with the elongated forelimbs supported the idea that it was an obligate quadruped. [7]
Silesaurus lived in a subtropical environment similar to the modern Mediterranean basin with alternating summer monsoons and dry winters. The animal shared its environment of extensive swamplands and fern vegetation with a wealth of invertebrates as well as dipnoan and ganoid fishes, temnospondyls, phytosaurs and early pterosaurs. [8]
A coprolite is fossilized feces. Coprolites are classified as trace fossils as opposed to body fossils, as they give evidence for the animal's behaviour rather than morphology. The name is derived from the Greek words κόπρος and λίθος. They were first described by William Buckland in 1829. Before this, they were known as "fossil fir cones" and "bezoar stones". They serve a valuable purpose in paleontology because they provide direct evidence of the predation and diet of extinct organisms. Coprolites may range in size from a few millimetres to over 60 centimetres.
Lagosuchus is an extinct genus of avemetatarsalian archosaur from the Late Triassic of Argentina. The type species of Lagosuchus, Lagosuchus talampayensis, is based on a small partial skeleton recovered from the early Carnian-age Chañares Formation. The holotype skeleton of L. talampayensis is fairly fragmentary, but it does possess some traits suggesting that Lagosuchus was a probable dinosauriform, closely related to dinosaurs.
Marasuchus is a genus of basal dinosauriform archosaur which is possibly synonymous with Lagosuchus. Both genera lived during the Late Triassic in what is now La Rioja Province, Argentina. Marasuchus contains a single species, Marasuchus lilloensis.
Pisanosaurus is an extinct genus of early dinosauriform, likely an ornithischian or silesaurid, from the Late Triassic of Argentina. It was a small, lightly built, ground-dwelling herbivore, that could grow up to an estimated 1 m (3.3 ft) long. Only one species, the type, Pisanosaurus mertii, is known, based on a single partial skeleton discovered in the Ischigualasto Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina. This part of the formation has been dated to the late Carnian, approximately 229 million years ago.
Nyasasaurus is an extinct genus of avemetatarsalian archosaur from the putatively Middle Triassic Manda Formation of Tanzania that may be the earliest known dinosaur. The type species Nyasasaurus parringtoni was first described in 1956 in the doctoral thesis of English paleontologist Alan J. Charig, but it was not formally described until 2013.
Teleocrater is a genus of avemetatarsalian archosaur from the Middle Triassic Manda Formation of Tanzania. The name was coined by English paleontologist Alan Charig in his 1956 doctoral dissertation, but was only formally published in 2017 by Sterling Nesbitt and colleagues. The genus contains the type and only species T. rhadinus. Uncertainty over the affinities of Teleocrater have persisted since Charig's initial publication; they were not resolved until Nesbitt et al. performed a phylogenetic analysis. They found that Teleocrater is most closely related to the similarly enigmatic Yarasuchus, Dongusuchus, and Spondylosoma in a group that was named the Aphanosauria. Aphanosauria was found to be the sister group of the Ornithodira, the group containing dinosaurs and pterosaurs.
Dinosauromorpha is a clade of avemetatarsalian archosaurs that includes the Dinosauria (dinosaurs) and some of their close relatives. It was originally defined to include dinosauriforms and lagerpetids, with later formulations specifically excluding pterosaurs from the group. Birds are the only dinosauromorphs which survive to the present day.
Stagonolepis is an extinct genus of stagonolepidid aetosaur known from the Late Triassic Hassberge Formation of Germany, the Drawno Beds of Poland, and the Lossiemouth Sandstone of Scotland. Supposed fossils from North and South America have been placed into their own genera, Calyptosuchus and Aetosauroides, respectively.
Dromomeron is a genus of lagerpetid avemetatarsalian which lived around 220 to 211.9 ± 0.7 million years ago. The genus contains species known from Late Triassic-age rocks of the Southwestern United States and northwestern Argentina. It is described as most closely related to the earlier Lagerpeton of Argentina, but was found among remains of true dinosaurs like Chindesaurus, indicating that the first dinosaurs did not immediately replace related groups.
Asilisaurus ; from Swahili, asili, and Greek, σαυρος is an extinct genus of silesaurid archosaur. The type species is Asilisaurus kongwe.Asilisaurus fossils were uncovered in the Manda Beds of Tanzania and date back to the early Carnian, making it one of the oldest known members of the Avemetatarsalia. It was the first non-dinosaurian dinosauriform recovered from Africa. The discovery of Asilisaurus has provided evidence for a rapid diversification of avemetatarsalians during the Middle Triassic, with the diversification of archosaurs during this time previously only documented in pseudosuchians.
Silesauridae is an extinct family of Triassic dinosauriforms. It is most commonly considered to be a clade of non-dinosaur dinosauriforms, and the sister group of dinosaurs. Some studies have instead suggested that most or all silesaurids comprised an early diverging clade or a paraphyletic grade within ornithischian dinosaurs. Silesaurids have a consistent general body plan, with a fairly long neck and legs and possibly quadrupedal habits, but most silesaurids are heavily fragmentary nonetheless. Furthermore, they occupied a variety of ecological niches, with early silesaurids being carnivorous and later taxa having adaptations for specialized herbivory. As indicated by the contents of referred coprolites, Silesaurus may have been insectivorous, feeding selectively on small beetles and other arthropods.
Diodorus is a genus of silesaurid dinosauromorph that lived during the Late Triassic in what is now Morocco. Fossils were discovered in the Timezgadiouine Formation of the Argana Basin, and were used to name the new genus and species Diodorus scytobrachion. The genus name honors the mythological king Diodorus and the ancient historian Diodorus Siculus; the specific name is ancient Greek for 'leathery arm' and also honors the mythographer Dionysius Scytobrachion. The holotype specimen is a partial dentary bone (front of the lower jaw), and assigned specimens include isolated teeth, two humeri (upper arm bones), a metatarsal (foot bone), and femur (thigh bone).
Smok is an extinct genus of large carnivorous archosaur. It lived during the latest Triassic period. Its remains have been found in Lisowice, southern Poland. The only species is Smok wawelski and was named in 2012. It is larger than any other known predatory archosaur from the Late Triassic or Early Jurassic of central Europe. The relation of Smok to other archosaurs has not yet been thoroughly studied; it may be a rauisuchid, prestosuchid, an ornithosuchid pseudosuchian or a theropod dinosaur.
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 front side of the next vertebrae, the hypantrum. Hyposphene-hypantrum articulations occur in the dorsal vertebrae and sometimes also in the posteriormost cervical and anteriormost caudal vertebrae.
Jerzy Dzik is a Polish paleontologist.
Soumyasaurus is a small silesaurid dinosauriform from the Late Triassic (Norian) Cooper Canyon Formation of western Texas.
Lisowicia is an extinct genus of giant dicynodont synapsid that lived in what is now Poland during the late Norian or earliest Rhaetian age of the Late Triassic Period, about 210–205 million years ago. Lisowicia is the largest known dicynodont, as well as the largest non-mammalian synapsid, reaching about 4.5 metres (15 ft) long, standing up to 2.6 metres (8.5 ft) tall at the hips and weighing around 5–7 metric tons, comparable in size to modern elephants. It was also one of the last dicynodonts, living shortly before their extinction at the end of the Triassic period. Fossils of a giant dicynodont were known from Poland since 2008, but Lisowicia was not named and officially described as a new species until late 2018.
Kwanasaurus is an extinct genus of silesaurid dinosauromorph reptiles from the Late Triassic of Colorado. It is known from a single species, Kwanasaurus williamparkeri. Kwanasaurus had a deeper, stronger skull and greater specialization for herbivory compared to other silesaurids. It also possessed many unique characteristics of the snout, ilium, and lower part of the femur. It was described along with new specimens of Dromomeron from the Eagle Basin, the northernmost extent of the Chinle Formation.
Kongonaphon is an extinct genus of lagerpetid avemetatarsalians from the Middle to Late Triassic of Madagascar. It contains a single species, Kongonaphon kely, which is known from a fragmentary partial skeleton. This fossil hails from the late Ladinian or early Carnian-age "basal Isalo II beds". As the first lagerpetid found in Africa, Kongonaphon extends the range of the family significantly. It possessed a combination of features from various other lagerpetids, but developed particularly long and slender leg bones. Kongonaphon is also the first lagerpetid for which fossils of the snout and teeth are known. It was likely an insectivore based on the shape and texture of its teeth.
Triamyxa is an extinct genus of myxophagan beetle in the monotypic family Triamyxidae from the Carnian stage of Late Triassic, approximately 230 million years ago. It was found in the Keuper Claystone of Poland. The type species is T. coprolithica and it was identified from specimens found in the coprolite ZPAL AbIII/3520, likely belonging to the dinosauriform Silesaurus opolensis. Because Triamyxa specimens were found inside coprolites, this may offer a new method of finding insect fossils aside from amber. It is currently the oldest known member of Myxophaga. It was interpreted as either the most basal member of Myxophaga, or a sister group to Hydroscaphidae.
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