Struthiosaurinae

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Struthiosaurines
Temporal range:
Early to Late Cretaceous, 112–66Ma
Skull of Europelta
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: †Ornithischia
Family: †Nodosauridae
Subfamily: †Struthiosaurinae
Nopcsa, 1923
Type species
Struthiosaurus austriacus
Bunzel, 1871
Genera

†Anoplosaurus
†Europelta
†Hungarosaurus
†Struthiosaurus

Struthiosaurinae is a subfamily of ankylosaurian dinosaurs from the Cretaceous of Europe. It is defined as the most inclusive clade containing Europelta but not Cedarpelta, Peloroplites, Sauropelta or Edmontonia. It was originally defined by Franz Nopcsa in 1923 as a subfamily of Acanthopholidae, now a junior synonym of Nodosauridae. The family has gone through many taxonomic revisions since it was defined by Nopcsa in 1902. It includes Anoplosaurus, Europelta, Hungarosaurus, and Struthiosaurus. Struthiosaurinae is now in use over Acanthopholinae because of the instability of Acanthopholis, the generic namesake. Struthiosaurinae appeared at about exactly the same time as the North American subfamily Nodosaurinae. Struthiosaurines range all across the cretaceous, the oldest genus being Europelta at an age of 112 Ma and the youngest being Struthiosaurus at about 85–66 Ma.

History

Humerus of Struthiosaurus

Baron Franz Nopcsa, in 1902, proposed a new grouping of dinosaurs, Acanthopholididae, a clade of lightly-built thyreophorans. He included in it the genera Acanthopholis, Polacanthus, Syngonosaurus, Struthiosaurus, and possibly Nodosaurus. Soon after, he also added Priodontognathus and Palaeoscincus. He considered Acanthopholididae to be the sister clade to Stegosauridae, and also stated that it might include Hylaeosaurus, which he found had most of the characteristics of the family.[1] Later, in 1915, he rearranged the species included in it. The genera that were later included were Acanthopholis (=Anoplosaurus), Polacanthus, Stegopelta, Stegoceras, and Struthiosaurus. Along with Ankylosaurus, Acanthopholididae was defined to form a subfamily of Nodosauridae.[2] In 1923 he divided up the family into two subfamilies without comment. These two subfamilies were named Acanthopholinae and Struthiosaurinae.[3]

Struthiosaurus osteoderms

In the same year, he corrected the subgroups of Thyreophora. He placed Acanthopholididae, Stegosauridae and Ceratopsidae together inside the group.[4] Five years later, he corrected the name of the family to Acanthopholidae, which is now the correct spelling. In the same publication, he also changed the genera included. He assigned Hylaeosaurus, Stegoceras, Struthiosaurus, and Troodon[5] inside it but moved Stegopelta and Ankylosaurus into the family Ankylosauridae.[6] Nopcsa then downgraded the phylogenetic rank of Acanthopholidae to make it a subfamily inside Nodosauridae. The clade was defined to include Ankylosaurus and Acanthopholinae. Inside Acanthopholinae he placed Acanthopholis, Hylaeosaurus, Rhodanosaurus, Struthiosaurus, and Troodon.[7] Now considered as an artificial grouping, it was defined to include dinosaur taxa now considered to be polacanthids, a pachycephalosaur and Acanthopholis, a genus that is widely considered to be dubious. Acanthopholidae and Acanthopholinae are now dubious groups since the validity of Acanthopholis has changed.[8]

Distinguishing characteristics

Skeletal reconstruction of Europelta, the most complete ankylosaurian known from Europe

Struthiosaurinae has a group of defining characteristics that allow it to be set apart from other clades and exclude certain genera. All the characteristics must be present for the genus to be considered part of the clade. All nodosaurids that possess this combination are included in the subfamily.[8]

The characteristics they have are: a narrow predentary; a nearly horizontal unfused quadrate oriented 30 degrees from the skull roof; mandibular condyles three times wider than long; premaxillary and dentary teeth that are near predentary symphysis; a dorsally arched sacrum; an acromion process dorsal to the midpoint of the scapula to coracoid suture; a straight ischium with a straight dorsal margin; relatively long, slender limbs; sacral shield armour; and erect pelvic osteoderms with flat bases.[8]

Classification

According to James Kirkland et al., Acanthopholinae was not an acceptable classification for the new clade of previously unrecognized nodosaurids because of the instability of Acanthopholis. Struthiosaurinae was decided on as the name of the clade, as it was the next published term after Acanthopholinae. To ensure the group was rendered valid, Kirkland et al. redefined Struthiosaurinae as the most inclusive clade containing Europelta but not Cedarpelta, Peloroplites, Sauropelta, or Edmontonia. This definition includes the genera Anoplosaurus, Europelta, Hungarosaurus and Struthiosaurus inside the newly defined group.[8]

This clade of nodosaurid genera has not been previously recognized by any analysis' of Nodosauridae.[8]

Biogeography

Skull restoration of Europelta, the oldest European nodosaurid

The near simultaneous appearance of nodosaurids in both North America and Europe is worthy of consideration, because at the time, they were separated from each other by a huge body of water. Europelta is the oldest nodosaurid from Europe; it is derived from the lower Albian Escucha Formation. The oldest western North American nodosaurid is Sauropelta, from the lower Albian Little Sheep Mudstone Member of the Cloverly Formation, at an age of 108.5±0.2 million years. Eastern North American fossils seem older. Teeth of Priconodon crassus have been derived from the Arundel Clay of the Potomac Group of Maryland, which dates near the Aptian–Albian boundary. A Propanoplosaurus hatchling was uncovered from the base of the underlying Patuxent Formation, dated to the upper Aptian, making Propanoplosaurus the oldest nodosaurid.[8]

Polacanthids are known from pre-Aptian fauna from both Europe and North America. The timing of the appearance of nodosaurids on both continents indicates the origins of the clade preceded the isolation of North America and Europe, thereby pushing the group's date of evolution back to at least the middle Aptian. The separation of Nodosauridae into European Struthiosaurinae and North American Nodosaurinae by the end of the Aptian provides a revised date for the isolation of the continents from each other with rising sealevel.[8]

Struthiosaurinae is one of the longest-lasting groups of ankylosaurians. They range from Europelta at 112 Ma to Struthiosaurus, which lived until the uppermost Cretaceous, or 66 Ma.[8] In between those two early and late struthiosaurines are the genera Anoplosaurus and Hungarosaurus. Hungarosaurus is younger, at about 85 Ma, from the late Santonian of the Csehbánya Formation. Anoplosaurus is a fair amount older, at about 100 Ma, from the late Albian Cambridge Greensand.[9]

Cretaceous Jurassic Late Cretaceous Early Cretaceous Late Jurassic Glyptodontopelta Antarctopelta Panoplosaurus Edmontonia Struthiosaurus Hungarosaurus Niobrarasaurus Silvisaurus Anoplosaurus Nodosaurus Stegopelta Animantarx Texasetes Pawpawsaurus Peloroplites Sauropelta Tatankacephalus Europelta Priconodon Propanoplosaurus Zhejiangosaurus Dongyangopelta Taohelong Gastonia (dinosaur) Polacanthus Hoplitosaurus Hylaeosaurus Gargoyleosaurus Mymoorapelta Cretaceous Jurassic Late Cretaceous Early Cretaceous Late Jurassic
Timeline of ages of polacanthid and nodosaurid genera. Genera are colour-coded based on continent: North American genera are green; European genera are blue; Asian genera are claret; genera from other continents are black. The dashed line separates the Polacanthids (above) from the Nodosaurids (below). Classification is based on Kirkland et al.[8] Ages are based on Holtz (2011)[10] except for Europelta, Propanoplosaurus, Priconodon, Sauropelta and Struthiosaurus whose ages are based on Kirkland et al. (2013);[8] Taohelong, Peloroplites, Tatankacephalus and Dongyangopelta whose ages are based on Yang et al. (2013),[11] Chure et al. (2010),[9][12] Parsons & Parsons (2009),[13] and Chen et al. (2013),[14] respectively; and Anoplosaurus and Hungarosaurus whose ages are based on Weishampel et al. (2004).[9]

References

  1. ↑ Nopcsa, B. F. (1902). "Notizen über cretacische Dinosaurier [Notes on Cretaceous dinosaurs]". Sitzungsberichte der Mathematisch-Naturwissenschaftlichen Classe der Kaiserlichen Akademie der Wissenschaften. 111 (1): 93–114. 
  2. ↑ Nopcsa, B.F (1915). "Die dinosaurier der Siebenbürgischen landesteile Ungarns". Mitteilungen aus dem Jahrbuche der Königlich-Ungarischen Geologischen Reichsanstalt 23: 1–26. 
  3. ↑ Nopcsa, B. F. (1923). "Die Familien der Reptilien. Fortschritte der Geologie und Paleontologie". Science 58 (1512): 517–526. doi:10.1126/science.58.1512.517-a. 
  4. ↑ Nopcsa, F. (1923). "On the Geological Importance of the Primitive Reptilian Fauna in the Uppermost Cretaceous of Hungary; with a Description of a New Tortoise (Kallokibotion)". Quarterly Journal of the Geological Society 79: 100–116. doi:10.1144/GSL.JGS.1923.079.01-04.08. 
  5. ↑ Nopcsa, B.F. (1928). "The genera of reptiles". Palaeobiologica 1: 163–188. 
  6. ↑ Nopcsa, B.F. (1928). "Palaeontological notes on reptiles. V. On the skull of the Upper Cretaceous dinosaur Euoplocephalus". Geologica Hungarica, Series Palaeontologica 1 (1): 1–84. 
  7. ↑ Nopcsa, B.F. (1929). "Dinosaurierreste aus Seibenburgen V.". Geologica Hungarica. Series Palaeontologica (4): 1–76. 
  8. ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 Kirkland, J. I.; Alcalá, L.; Loewen, M. A.; Espílez, E.; Mampel, L.; Wiersma, J. P. (2013). "The Basal Nodosaurid Ankylosaur Europelta carbonensis n. gen., n. sp. From the Lower Cretaceous (Lower Albian) Escucha Formation of Northeastern Spain". In Butler, Richard J. PLoS ONE 8 (12): e80405. doi:10.1371/journal.pone.0080405. 
  9. ↑ 9.0 9.1 9.2 Weishampel, D.B.; Dodson, P.; and Osmólska, H. (2004). The Dinosauria, 2nd. Berkeley: University of California Press. pp. 588–593. ISBN 0-520-24209-2. 
  10. ↑ Holtz, T.R. Jr. (2011). Dinosaurs: The Most Complete, Up-to-date Encyclopedia for Dinosaur Lovers of All Ages. New York: Random House. pp. 37–38. ISBN 0-375-81297-0. 
  11. ↑ Yang, J.T.; You, H.L.; Li, D.Q.; Kong, D.L. (2013). "First discovery of a polacanthine ankylosaur dinosaur in Asia". Vertebrata PalAsiatica: 265–277. 
  12. ↑ Chure, D.; Britt, B.; Whitlock, J.A. & Wilson, J.A. (2010). "First complete sauropod dinosaur skull from the Cretaceous of the Americas and the evolution of sauropod dentition". Naturwissenschaften 97 (4): 379–391. doi:10.1007/s00114-010-0650-6. PMC 2841758. PMID 20179896. 
  13. ↑ Parsons, W.L. & Parsons, K.M. (2009). "A new ankylosaur (Dinosauria: Ankylosauria) from the Lower Cretaceous Cloverly Formation of central Montana". Canadian Journal of Earth Sciences 46: 721–738. 
  14. ↑ Chen, R.; Zheng, W.; Azuma, Y.; Shibata, M.; Lou, T.; Jin, Q. & Jin, X. (2013). "A New Nodosaurid Ankylosaur from the Chaochuan Formation of Dongyang, Zhejiang Province, China". Acta Geologica Sinica 87 (3): 658–671. 

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