Sciurumimus

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Sciurumimus
Temporal range: Late Jurassic, 150  Ma
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Xaveropterus 2.jpg
The juvenile type specimen
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Orionides
Genus: Sciurumimus
Rauhut et al., 2012
Species:
S. albersdoerferi
Binomial name
Sciurumimus albersdoerferi
Rauhut et al., 2012

Sciurumimus ("Squirrel-mimic," named for its tail's resemblance to that of the tree squirrel, Sciurus [1] ) is an extinct genus of tetanuran theropod from the Late Jurassic Torleite Formation of Germany. It is known from a single juvenile specimen representing the type species, Sciurumimus albersdoerferi, which was found in a limestone quarry close to Painten in Lower Bavaria. [2] The specimen was preserved with traces of feather-like filaments. [3]

Contents

The Sciurumimus specimen was first announced in an informal presentation by Rauhut and Foth (2011), [4] but not formally described and named until the following year by Rauhut et al. (2012). Although originally classified as a basal megalosauroid, [2] later phylogenetic analyses dispute this placement. [5] However, a recent analysis on immature coelurosaurs, including compsognathids, finds Sciurumimus back in Megalosauroidea. [6]

Description

Life restoration of a juvenile Sciurumimus, with two Pterodactylus in the background Sciurumimus on beach.jpg
Life restoration of a juvenile Sciurumimus, with two Pterodactylus in the background

Sciurumimus is known from a single holotype fossil that is exceptionally well-preserved, with full skeleton in complete articulation along with fine details of soft tissue. It is comparable in size and proportions to the juvenile coelurosaur Juravenator , although differs significantly in several anatomical details. The skull of Sciurumimus is proportionally large, at 156% of the length of the femur and longer than the cervical vertebrae series. These body proportions, along with short forelimbs, lack of fusion in the skeleton, and regular tooth morphology indicate the specimen represents a very young, probably early-posthatchling individual. [2]

The fossil preserves filamentous plumage at the tail base and on other parts of the body. These structures are described as being identical to the stage 1 feathers preserved in some ornithischians, the basal tyrannosaur Dilong , and the basal therizinosauroid Beipiaosaurus . Skin is also preserved. [7] Although most of the preserved soft tissue on the Sciurumimus holotype likely represent integumentary structures, a small patch of what may be muscle tissue is observed along the rear edge of the tibia. [2]

Classification

Close up of the skull Xaveropterus head.jpg
Close up of the skull

When first discovered, a phylogenetic analysis suggested that Sciurumimus may have been a primitive member of the Megalosauroidea, a clade of large carnivorous dinosaurs more primitive than many other well-known theropods like the tyrannosauroids and carnosaurs, making it the most basal known feathered theropod. [2] This classification was supported by one of three initial analyses conducted by the scientists who described it. The other two analyses, which the authors regarded as less well supported, found it as more closely related to Monolophosaurus and Avetheropoda, and in an unresolved position among avetheropods and megalosauroids, respectively. The exact position in the various analyses was difficult to determine due to the fact that the only known specimen is a very young juvenile. [2]

This initial study was criticized by several researchers, who noted that some of the old analyses the scientists used to plug in data from the new fossil were incomplete and missing relevant data on various species. [8] [9] In an analysis published in 2013 Sciurumimus was obtained as one of the most primitive members of the Coelurosauria, more derived than the megalosauroids. However, this analysis focused on the Coelurosauria and the dataset on which it was based contained only one megalosaurid and only four terminal taxa outside the Coelurosauria. [10] Other analyses found it to be an allosauroid [11] or a tetanuran outside Avetheropoda. [12] Paul (2016) placed it among basal neocoelurosaurs. [13] A detailed reanalysis of the taxon was done in the supplementary material of Hartman et al. (2019) which found several characters to be misscored, and when the uncorrected Sciurumimus was placed in the matrix Juravenator was also found to be a basal tetanuran, while if Sciurumimus was absent Juravenator would be found to be a basal coelurosaur. The analysis found Sciurumimus to be a compsognathid, though they noted that this position was tentative. [5] Foth et al. (2020) again placed, albeit tentatively, Sciurumimus in Megalosauroidea, this time accompanied by Juravenator . [14]

Andrea Cau, in 2024, recovered Sciurumimus, along with Compsognathus and Scipionyx all within different positions within Megalosauroidea. [6]

Here is a simplified phylogeny of Cau (2024) with Sciurumimus in bold.

Tetanurae

Related Research Articles

<span class="mw-page-title-main">Theropoda</span> Clade of dinosaurs

Theropoda whose members are known as theropods, is an extant dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the majority of large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 11,000 living species.

<span class="mw-page-title-main">Coelurosauria</span> Clade of dinosaurs

Coelurosauria is the clade containing all theropod dinosaurs more closely related to birds than to carnosaurs.

<span class="mw-page-title-main">Carnosauria</span> Extinct group of theropod dinosaurs

Carnosauria is an extinct group of carnivorous theropod dinosaurs that lived during the Jurassic and Cretaceous periods.

<span class="mw-page-title-main">Tetanurae</span> Clade containing most theropod dinosaurs

Tetanurae is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, and coelurosaurs. Tetanurans are defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely diverged from its sister group, Ceratosauria, during the late Triassic. Tetanurae first appeared in the fossil record by the Early Jurassic about 190 mya and by the Middle Jurassic had become globally distributed.

<span class="mw-page-title-main">Megalosauridae</span> Extinct family of dinosaurs

Megalosauridae is a monophyletic family of carnivorous theropod dinosaurs within the group Megalosauroidea. Appearing in the Middle Jurassic, megalosaurids were among the first major radiation of large theropod dinosaurs. They were a relatively primitive group of basal tetanurans containing two main subfamilies, Megalosaurinae and Afrovenatorinae, along with the basal genus Eustreptospondylus, an unresolved taxon which differs from both subfamilies.

<i>Megaraptor</i> Extinct genus of dinosaurs

Megaraptor is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dromaeosaur-like coelurosaur, it was classified as a neovenatorid allosauroid in previous phylogenies, but more recent phylogeny and discoveries of related megaraptoran genera has placed it as either a basal tyrannosauroid or a basal coelurosaur with some studies still considering it a neovenatorid.

<i>Piatnitzkysaurus</i> Extinct genus of dinosaurs

Piatnitzkysaurus is a genus of tetanuran theropod dinosaur that lived approximately 179 to 177 million years ago during the lower part of the Jurassic Period in what is now Argentina. Piatnitzkysaurus was a moderately large, lightly built, bipedal, ground-dwelling carnivore that could grow up to 6.6 m (21.7 ft) long.

Chuandongocoelurus is a genus of carnivorous tetanuran theropod dinosaur from the Jurassic of China.

<i>Condorraptor</i> Extinct genus of dinosaurs

Condorraptor is an extinct genus of megalosauroid theropod dinosaur. Its genus name means 'robber from Cerro Condor', referencing a nearby village, while its species name, currumili, is named after Hipolito Currumil, the landowner and discoverer of the locality. It was among the earliest large South American theropods, having been found in Lower Jurassic strata of the Cañadón Asfalto Formation in the Cañadón Asfalto Basin of Argentina. The type species, described in 2005, is Condorraptor currumili. It is based on a tibia, with an associated partial skeleton that may belong to the same individual. Initially described as a basal tetanuran, Benson (2010) found it to be a piatnitzkysaurid megalosauroid and the sister taxon of Piatnitzkysaurus, a finding supported by later studies.

<i>Juravenator</i> Extinct genus of dinosaurs

Juravenator is a genus of small coelurosaurian theropod dinosaur, which lived about 151 or 152 million years ago in the area that would someday become the top of the Franconian Jura of Germany. It is known from a single, juvenile specimen.

<span class="mw-page-title-main">Compsognathidae</span> Extinct family of dinosaurs

Compsognathidae is a family of coelurosaurian theropod dinosaurs. Compsognathids were small carnivores, generally conservative in form, hailing from the Jurassic and Cretaceous Periods. The bird-like features of these species, along with other dinosaurs such as Archaeopteryx inspired the idea for the connection between dinosaur reptiles and modern-day avian species. Compsognathid fossils preserve diverse integument — skin impressions are known from four genera commonly placed in the group, Compsognathus, Sinosauropteryx, Sinocalliopteryx, and Juravenator. While the latter three show evidence of a covering of some of the earliest primitive feathers over much of the body, Juravenator and Compsognathus also show evidence of scales on the tail or hind legs. "Ubirajara jubatus", informally described in 2020, had elaborate integumentary structures on its back and shoulders superficially similar to the display feathers of a standardwing bird-of-paradise, and unlike any other non-avian dinosaur currently described.

<i>Duriavenator</i> Genus of theropod dinosaur

Duriavenator is a genus of theropod dinosaur that lived in what is now England during the Middle Jurassic, about 168 million years ago. In 1882, upper and lower jaw bones of a dinosaur were collected near Sherborne in Dorset, and Richard Owen considered the fossils to belong to the species Megalosaurus bucklandii, the first named non-bird dinosaur. By 1964, the specimen was recognised as belonging to a different species, and in 1974 it was described as a new species of Megalosaurus, M. hesperis; the specific name means 'the West' or 'western'. Later researchers questioned whether the species belonged to Megalosaurus, in which many fragmentary theropods from around the world had historically been placed. After examining the taxonomic issues surrounding Megalosaurus, Roger B. J. Benson moved M. hesperis to its own genus in 2008, Duriavenator; this name means "Dorset hunter".

<span class="mw-page-title-main">Megaraptora</span> Extinct clade of dinosaurs

Megaraptora is a clade of carnivorous theropod dinosaurs with controversial relationships to other tetanuran theropods. Its derived members, the Megaraptoridae are noted for their large hand claws and powerfully-built forelimbs, which are usually reduced in size in other large theropods.

<i>Zuolong</i> Extinct genus of dinosaurs

Zuolong is an extinct genus of tetanuran theropod from the Late Jurassic period of China. The type and only species is Z. salleei. The generic name of Zuolong is in honor of General Zuo Zōngtáng with the Chinese word "long" which means dragon. The specific epithet "salleei" is in honor of Hilmar Sallee, who funded the expedition which led to the specimen's discovery.

<span class="mw-page-title-main">Piatnitzkysauridae</span> Extinct family of dinosaurs

Piatnitzkysauridae is an extinct family of megalosauroid or basal allosauroid dinosaurs. It only consists of three to four known dinosaur genera: Condorraptor, Marshosaurus, Piatnitzkysaurus and possibly Xuanhanosaurus. The most complete and well known member of this family is Piatnitzkysaurus, which also gives the family its name.

<i>Kulindadromeus</i> Extinct genus of dinosaurs

Kulindadromeus was a herbivorous dinosaur, a basal neornithischian from the Middle Jurassic. The first Kulindadromeus fossil was found in Russia. Its feather-like integument is evidence for protofeathers being basal to Ornithischia and possibly Dinosauria as a whole, rather than just to Coelurosauria, as previously suspected.

<i>Serikornis</i> Extinct genus of dinosaurs

Serikornis is a genus of small, feathered anchiornithid dinosaur from the Upper Jurassic Tiaojishan Formation of Liaoning, China. It is represented by the type species Serikornis sungei.

<span class="mw-page-title-main">Anchiornithidae</span> Extinct family of dinosaurs

Anchiornithidae is a family of small paravian dinosaurs. Anchiornithids have been classified at varying positions in the paravian tree, with some scientists classifying them as a distinct family, a basal subfamily of Troodontidae, members of Archaeopterygidae, or an assemblage of dinosaurs that are an evolutionary grade within Avialae or Paraves.

<i>Asfaltovenator</i> Extinct genus of theropod dinosaur

Asfaltovenator is a genus of possibly allosauroid dinosaur from the Lower Jurassic Cañadón Asfalto Formation of Chubut Province, Argentina. The type and only species is Asfaltovenator vialidadi.

References

  1. "Newly Discovered Dinosaur Implies Greater Prevalence of Feathers". American Museum of Natural History. July 2, 2012. Retrieved February 2, 2019.
  2. 1 2 3 4 5 6 Rauhut, O. W. M.; Foth, C.; Tischlinger, H.; Norell, M. A. (2012). "Exceptionally preserved juvenile megalosauroid theropod dinosaur with filamentous integument from the Late Jurassic of Germany". Proceedings of the National Academy of Sciences. 109 (29): 11746–11751. Bibcode:2012PNAS..10911746R. doi: 10.1073/pnas.1203238109 . PMC   3406838 . PMID   22753486.
  3. Switek, B. (2012). "Rise of the fuzzy dinosaurs". Nature. doi:10.1038/nature.2012.10933. S2CID   123219913.
  4. Rauhut and Foth, (2011). New information on Late Jurassic theropod dinosaurs from Southern Germany. IV Congresso Latinoamericano Paleontologia de Vertebrados.
  5. 1 2 Hartman, Scott; Mortimer, Mickey; Wahl, William R.; Lomax, Dean R.; Lippincott, Jessica; Lovelace, David M. (2019-07-10). "A new paravian dinosaur from the Late Jurassic of North America supports a late acquisition of avian flight (Supplemental phylogenetic data)". PeerJ. 7: e7247. doi: 10.7717/peerj.7247 . ISSN   2167-8359. PMC   6626525 . PMID   31333906.
  6. 1 2 Cau, Andrea (2024). "A Unified Framework for Predatory Dinosaur Macroevolution" (PDF). Bollettino della Società Paleontologica Italiana. 63 (1): 1-19. doi:10.4435/BSPI.2024.08 (inactive 2024-11-20).{{cite journal}}: CS1 maint: DOI inactive as of November 2024 (link)
  7. Hendrickx, Christophe; Bell, Phil R.; Pittman, Michael; Milner, Andrew R. C.; Cuesta, Elena; O'Connor, Jingmai; Loewen, Mark; Currie, Philip J.; Mateus, Octávio; Kaye, Thomas G.; Delcourt, Rafael (2022). "Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs". Biological Reviews. 97 (3): 960–1004. doi:10.1111/brv.12829. ISSN   1469-185X. PMID   34991180. S2CID   245820672.
  8. Mortimer, M. 2013. "Coelurosauria Archived 2013-09-29 at the Wayback Machine ", The Theropod Database. Accessed online 09-AUG-2013.http://archosaur.us/theropoddatabase/Coelurosauria.htm#Sciurumimusalbersdoerferi
  9. Mortimer, M. and Marjanovic, D. (in prep.) http://archosaur.us/theropoddatabase/Coelurosauria.htm#Sciurumimusalbersdoerferi Archived 2013-09-29 at the Wayback Machine
  10. See pages 3 and 11 in the supplementary material of Godefroit, Pascal; Cau, Andrea; Hu, Dong-Yu; Escuillié, François; Wu, Wenhao; Dyke, Gareth (2013). "A Jurassic avialan dinosaur from China resolves the early phylogenetic history of birds". Nature. 498 (7454): 359–362. Bibcode:2013Natur.498..359G. doi:10.1038/nature12168. PMID   23719374. S2CID   4364892.
  11. Yang, Zixiao; Jiang, Baoyu; McNamara, Maria E.; Kearns, Stuart L.; Pittman, Michael; Kaye, Thomas G.; Orr, Patrick J.; Xu, Xing; Benton, Michael J. (January 2019). "Pterosaur integumentary structures with complex feather-like branching". Nature Ecology & Evolution. 3 (1): 24–30. doi:10.1038/s41559-018-0728-7. hdl: 1983/1f7893a1-924d-4cb3-a4bf-c4b1592356e9 . ISSN   2397-334X. PMID   30568282. S2CID   56480710.
  12. Benton, Michael J.; Dhouailly, Danielle; Jiang, Baoyu; McNamara, Maria (2019-09-01). "The Early Origin of Feathers". Trends in Ecology & Evolution. 34 (9): 856–869. doi:10.1016/j.tree.2019.04.018. hdl: 10468/8068 . ISSN   0169-5347. PMID   31164250. S2CID   174811556.
  13. Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs 2nd Edition. Princeton University Press. p. 120. ISBN   978-0-691-16766-4.
  14. Foth, Christian; Haug, Carolin; Haug, Joachim T.; Tischlinger, Helmut; Rauhut, Oliver W. M. (2020), Foth, Christian; Rauhut, Oliver W. M. (eds.), "Two of a Feather: A Comparison of the Preserved Integument in the Juvenile Theropod Dinosaurs Sciurumimus and Juravenator from the Kimmeridgian Torleite Formation of Southern Germany", The Evolution of Feathers: From Their Origin to the Present, Fascinating Life Sciences, Cham: Springer International Publishing, pp. 79–101, doi:10.1007/978-3-030-27223-4_6, ISBN   978-3-030-27223-4, S2CID   216245045 , retrieved 2020-11-12