Struthiosaurinae

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" while being reinstated for a newly recognized clade of basal nodosaurids. 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.

It was originally mentioned by Franz Nopcsa in 1923 as a subfamily of Acanthopholidae, along with the previously defined Acanthopholinae. The family has gone through many taxonomic revisions since it was defined by Nopcsa in 1902. It is now recognized as a junior synonym of the family Nodosauridae. The subfamily now includes the genera Anoplosaurus, Europelta, Hungarosaurus, and Struthiosaurus, designated as the type genus. Because of the instability of Acanthopholis, the generic namesake of Acanthopholinae, and its current identification as a nomen dubium, Struthiosaurinae, the next named group, was decidedly used over the older one.

A review of ankylosaur osteoderms was published in 2000, and reviewed the armour of Struthiosaurinae. The group was represented by the single genus Struthiosaurus, known from head, cervical, dorsal, sacral, and caudal scutes. Only a few head osteoderms were identified, so it is unknown how much of the skull was armoured. Many cervical and dorsal scutes have been preserved alongside species of Struthiosaurus. They include cervical bands, which are groups of osteoderms fused together and attached to the vertebrae, and large spines found on the shoulders of nodosaurids like Sauropelta and Edmontonia, although it is not known if the spines were fused like the later of separate like the former. It is quite possible that small ovoid scutes found on Struthiosaurus could have formed a pelvic shield like polacanthids. The caudal scutes of struthiosaurines are small and rough. Even though osteoderms are well-known, it is not certain where they were positioned on the body.

Struthiosaurines
Temporal range:
Early to Late Cretaceous, 112–66 Ma
Europelta skull
Skull of Europelta
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Family: Nodosauridae
Subfamily: Struthiosaurinae
Nopcsa, 1923
Type species
Struthiosaurus austriacus
Genera[1]

?†Anoplosaurus
?†Europelta
?†Hungarosaurus
?†Rhadinosaurus
Struthiosaurus (type)

Classification

Struthiosaurinae is a group named by Franz Nopcsa, that was reinstated by James Kirkland for a group of just-european nodosaurids.[1]

History

Struthiosaurus occitanicus humerus
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.[2] 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.[3] In 1923 he divided up the family into two subfamilies without comment. These two subfamilies were named Acanthopholinae and Struthiosaurinae.[1][4]

In the same year, he corrected the subgroups of Thyreophora. He placed Acanthopholididae, Stegosauridae and Ceratopsidae together inside the group.[5] 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[6] inside it but moved Stegopelta and Ankylosaurus into the family Ankylosauridae.[7] 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.[8] 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.[1]

Phylogeny

Historically, Struthiosaurinae has been considered a junior synonym of the family Nodosauridae by Walter P. Coombs in 1978 and Tatyana Tumanova in 1987,[9][10] or a sister clade to Edmontoniinae, Panoplosaurinae, Stegopeltinae, and Sauropeltinae by Tracy L. Ford in 2000.[11] Kirkland and his colleagues followed Ford in using Struthiosaurinae as a clade of basal nodosaurids, but concluded that the only other subfamily of Nodosauridae was Nodosaurinae. According to 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.[1] Below is a cladogram from before the recognition of the clade Struthiosaurinae.[12]

Nodosauridae

Struthiosaurus

Hungarosaurus

Silvisaurus

Sauropelta

Pawpawsaurus

Edmontonia

Panoplosaurus

Description

Europelta Scale
Size comparison of Europelta and a human.

Struthiosaurines are well-known, and include one of the best-preserved species of ankylosaur, Europelta carbonensis.[1]

Osteoderms

Struthiosaurus occitanicus osteoderms
Struthiosaurus osteoderms

In 2000, Ford published a complete description of ankylosaurian osteoderms, in which he recognized the group Struthiosaurinae. Ford's description of Struthiosaurinae was based on the genus Struthiosaurus. Ford found that Struthiosaurus transylvanicus lacked any remains of the jugal, which makes a jugal scute unknown. The skull roof of T. transylvanicus is large and bulbous, preserving a large, flat scute on top, and no osteoderms behind the orbits. Another species, S. austriacus, is known from two incomplete skulls, which preserved irregular scutes parallel to the orbits along the cranium.[11]

Scutes from the postcranial region of the skeleton are also known from struthiosaurines. Cervical bands have been found on S. austriacus, as well as S. sp.. The cervical bands are preserved as a groups of two or three osteoderms that are fused with a large neural spine on the medial edge, and attached to each other through small ovular scutes with short rounded peaks. The scute attaching to the neural spine has a round ridge with a shallow depression ovular in shape. One band was preserved with a primary osteoderm that was angled across the neck from side-to-side and was as long as the whole band itself. The base of the scute is rounded and ends with a tapered point, and the upper side of the scute has a smooth, lightly arching shape. Other bands are preserved with a triangular osteoderms with flat tops and rounded bottoms. The exact placement of cervical bands is not known. In 1995, Pereda-Suberbiola et al. suggested that in a more traditional placement, the bands would have been horizontal along the body, with the neural spine in the middle of the back. That positioning would mean that the medial scute would be next to another osteoderm of equal size, and together they would either fuse, like in Edmontonia, or touch, as in Sauropelta. Another possibility, suggested by Ford, was that the bands were along the side of the neck, pointing dorsally. If oriented along the side, the primary scutes would have pointed up and down, like in polacanthids, and the medial scutes would, by definition, become secondary osteoderms. The set of medial scutes (or secondary) would be possibly oval in shape.[11]

Skeletal reconstruction of Europelta
Skeletal reconstruction of Europelta, the most complete ankylosaurian known from Europe: B and C showing osteoderm coverage

Thoratic scutes on struthiosaurines are oval to teardrop shaped, and possess sharp ridges that rise distally. Some scutes were long and had small domes on them. The first primary osteoderms on the pelvis are large, compressed from the sides, and have a sharp, short point. S. sp. was preserved with five fragmentary scutes from the pelvis. One fragment includes two small scutes with a ridge down the middle, joining the two together, and a compressed osteoderm with a small spike. It is thought that the fragment was from the edge of the pelvic region. Another fragment includes two oval osteoderms with small ossicles fused between them. Pelvic shields were probably formed on struthiosaurines by these scutes.[11]

Caudal scutes have been preserved on struthiosaurines. The osteoderms are compressed inwards from the side, have a slope positioned anteriorly, and a square-shaped posterior edge.[11]

Distinguishing anatomical features

All ankylosaurs that possess these characteristics - a narrow predentary; a nearly horizontal quadrate that is not fused and is oriented 30 degrees from the skull roof; the presence of mandibular condyles that are three times wider than long; premaxillary and dentary teeth that are near a symphysis with the front of the lower jaw (the predentary); a sacrum arched on top; an acromion process above the midpoint of the scapula to coracoid attachment; a straight ischium with a straight dorsal margin; relatively long, slender limbs; sacral shield armour; and the presence of erect pelvic osteoderms with flat bases - form a clade of basal nodosaurids, the Struthiosaurinae. That set of cranial and postcranial features are only present on genera considered to be in the clade. The features above distinguish Struthiosaurinae from other clades and genera found by other analysis'.[1]

Biogeography

Nodosauridae biogeography
Biogeography of european and North American nodosaurids and polacanthids

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.[1] 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.[1]

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.[1] 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.[13]

See also

References

  1. ^ a b c d e f g h i j Kirkland, J. I.; Alcalá, L.; Loewen, M. A.; Espílez, E.; Mampel, L.; Wiersma, J. P. (2013). Butler, Richard J (ed.). "The Basal Nodosaurid Ankylosaur Europelta carbonensis n. gen., n. sp. From the Lower Cretaceous (Lower Albian) Escucha Formation of Northeastern Spain". PLoS ONE. 8 (12): e80405. doi:10.1371/journal.pone.0080405. PMC 3847141. PMID 24312471.
  2. ^ 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.
  3. ^ Nopcsa, B.F (1915). "Die dinosaurier der Siebenbürgischen landesteile Ungarns". Mitteilungen aus dem Jahrbuche der Königlich-Ungarischen Geologischen Reichsanstalt. 23: 1–26.
  4. ^ 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.
  5. ^ 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.
  6. ^ Nopcsa, B.F. (1928). "The genera of reptiles". Palaeobiologica. 1: 163–188.
  7. ^ 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.
  8. ^ Nopcsa, B.F. (1929). "Dinosaurierreste aus Seibenburgen V.". Geologica Hungarica. Series Palaeontologica (4): 1–76.
  9. ^ Coombs, W.P. Jr. (1978). "The Families of the Ornithischia Dinosaur Order Ankylosauria" (PDF). Palaeontology. 21 (1): 143–170.
  10. ^ Tumanova, T.A. (1987). "The Armored Dinosaurs of Mongolia" (PDF). The Joint Soviet-Mongolian Paleontological Expedition Transaction. 32: 9.
  11. ^ a b c d e Ford, T.L. (2000). Lucas, S.G.; Heckert, A.B. (eds.). "Dinosaurs of New Mexico". New Mexico Museum of Natural History and Science Bulletin. 17: 157–167. |chapter= ignored (help)
  12. ^ Stein, M.; Hayashi, S.; Sander, P. M. (2013). "Long Bone Histology and Growth Patterns in Ankylosaurs: Implications for Life History and Evolution". PLoS ONE. 8 (7): e68590. doi:10.1371/journal.pone.0068590. PMC 3722194. PMID 23894321.
  13. ^ 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.CS1 maint: Uses authors parameter (link)

External links

Acantholipan

Acantholipan is a genus of herbivorous nodosaurid dinosaur from Mexico from the early Santonian age of the Late Cretaceous. It includes one species, Acantholipan gonzalezi.

Ankylosaurinae

Ankylosaurinae is a subfamily of ankylosaurid dinosaurs, existing from the Early Cretaceous about 105 million years ago until the end of the Late Cretaceous, about 66 mya. Many genera are included in the clade, such as Ankylosaurus, Pinacosaurus, Euoplocephalus, and Saichania.

Anoplosaurus

Anoplosaurus (meaning "unarmored or unarmed lizard") is an extinct genus of herbivorous nodosaurid dinosaur, from the late Albian-age Lower Cretaceous Cambridge Greensand of Cambridgeshire, England. It has in the past been classified with either the armored dinosaurs or the ornithopods, but current thought has been in agreement with the "armored dinosaur" interpretation, placing it in the Ankylosauria.

Bienosaurus

Bienosaurus (meaning "Bien's lizard") is a genus of thyreophoran dinosaur from the Lower Jurassic (probably Sinemurian) Lower Lufeng Formation in Yunnan Province in China.

Bissektipelta

Bissektipelta is a genus of herbivorous ankylosaurid dinosaur from the Upper Cretaceous of Uzbekistan. Bissektipelta is monospecific, containing only the species B. archibaldi.

Dongyangopelta

Dongyangopelta is an extinct genus of nodosaurid ankylosaurian dinosaur known from the "middle" Cretaceous Chaochuan Formation (Albian or Cenomanian stage) of Dongyang, Zhejiang Province, China. Dongyangopelta was first named by Rongjun Chen, Wenjie Zheng, Yoichi Azuma, Masateru Shibata, Tianliang Lou, Qiang Jin and Xingsheng Jin in 2013 and the type species is Dongyangopelta yangyanensis. It differs from Zhejiangosaurus, the second nodosaurid from southeast China, in the characters of presacral rod, ilium, and femur. Donyangopelta is distinguishable from Zhejiangosaurus only on the basis of the morphology of its pelvic shield.

Europelta

Europelta is an extinct genus of struthiosaurine nodosaurid dinosaur known from the Early Cretaceous (early Albian stage) lower Escucha Formation of Teruel Province, northeastern Spain. It contains a single species, Europelta carbonensis. It is known from two associated partial skeletons, and represents the most complete ankylosaur known from Europe.

Hungarosaurus

Hungarosaurus tormai is a herbivorous nodosaurid ankylosaur from the Upper Cretaceous (Santonian) Csehbánya Formation of the Bakony Mountains of western Hungary. It is the most completely known ankylosaur from the Cretaceous of Europe. Ankylosaur material had been known from Europe since the 19th century, with finds having been previously made in England, Austria, western Romania, France, and northern Spain.

Invictarx

Invictarx is a genus of herbivorous nodosaurid dinosaur from New Mexico dating from the early Campanian epoch of the Late Cretaceous.

Mongolostegus

Mongolostegus is a genus of stegosaur from the Early Cretaceous (Aptian-Albian) of Mongolia. The type and only species is M. exspectabilis, known from a single specimen previously under the nomen nudum Wuerhosaurus mongoliensis.

Nodosauridae

Nodosauridae is a family of ankylosaurian dinosaurs, from the Late Jurassic to the Late Cretaceous period of what are now North America, Europe, Asia, Africa, and Antarctica.

Nodosaurinae

Nodosaurinae is a group of ankylosaurian dinosaurs named in 1919 by Othenio Abel.

Nodosaurus

Nodosaurus (meaning "knobbed lizard") is a genus of herbivorous ankylosaurian dinosaur from the Late Cretaceous, the fossils of which are found in North America.

Polacanthinae

Polacanthinae is a grouping of ankylosaurs, possibly primitive nodosaurids. Polacanthines are late Jurassic to early Cretaceous in age, and appear to have become extinct about the same time a land bridge opened between Asia and North America.Polacanthines were somewhat more lightly armoured than more advanced ankylosaurids and nodosaurids. Their spikes were made up of thin, compact bone with less reinforcing collagen than in the heavily armoured nodosaurids. The relative fragility of polacanthine armour suggests that it may have been as much for display as defense.

Silvisaurus

Silvisaurus, from the Latin silva "woodland" and Greek sauros "lizard", is a nodosaurid ankylosaur from the middle Cretaceous period.

Struthiosaurus

Struthiosaurus (Latin struthio = ostrich + Greek sauros = lizard) is one of the smallest known and most basal genera of nodosaurid dinosaurs, from the Late Cretaceous period (Santonian-Maastrichtian) of Austria, Romania, France and Hungary in Europe. It was protected by body armour. Although estimates of its length vary, it may have been as small as 2.2 metres (7.2 ft) long.

Tatisaurus

Tatisaurus is a genus of ornithischian dinosaur from the Early Jurassic from the Lower Lufeng Formation in Yunnan Province in China. Little is known as the remains are fragmentary.

Tianzhenosaurus

Tianzhenosaurus (Tianzhen + Greek sauros="lizard") is a genus of ankylosaurid dinosaurs discovered in Tianzhen County, at Kangdailiang near Zhaojiagou Village, in Shanxi Province, China, in the Late Cretaceous Huiquanpu Formation. Thus far, a virtually complete skull and postcranial skeleton have been assigned to the genus, which is monotypic (T. youngi Pang & Cheng, 1998).

This was a medium-sized ankylosaurian, the skull measuring 28 cm (11 in) in length, with a total body length around 4 m (13 ft).

Vickaryous et al. (2004) placed Tianzhenosaurus within the Ankylosauridae, nested as the sister group to Pinacosaurus. Some authors have suggested that Tianzhenosaurus is actually a junior synonym of Saichania chulsanensis.

Tsagantegia

Tsagantegia (; meaning "of Tsagan-Teg"; Tumanova, 1993) is a genus of medium-sized ankylosaurid dinosaur from the Late Cretaceous of Mongolia, during the Cenomanian stage.

The holotype specimen (GI SPS N 700/17), a complete skull, was recovered from the Bayan Shireh Formation (Cenomanian-Santonian), at the Tsagan-Teg ("White Mountain") locality, Dzun-Bayan, in the southeastern Gobi Desert, Mongolia. The genus is monotypic, including only the type species, T. longicranialis.

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