Thyreophora

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Thyreophorans
Temporal range: Early Jurassic-Late Cretaceous, 200.91–66  Ma
Gastonia mount BYU 4.jpg
Skeletal mount of Gastonia burgei , BYU Museum of Paleontology
Stegosaurus (Natural History Museum, London).jpg
Skeletal mount of Stegosaurus stenops , Natural History Museum, London
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Clade: Genasauria
Clade: Thyreophora
Nopcsa, 1915
Subgroups

Thyreophora ("shield bearers", often known simply as "armored dinosaurs") is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous.

Contents

Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Primitive forms had simple, low, keeled scutes or osteoderms, whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans were herbivorous and had relatively small brains for their body size.

Thyreophora includes various subgroups, including the suborders Ankylosauria and Stegosauria. In both the suborders, the forelimbs were much shorter than the hindlimbs, particularly in stegosaurs. The clade has been defined as the group consisting of all species more closely related to Ankylosaurus than to Triceratops . Thyreophora is the sister group of Cerapoda within Genasauria.

Groups of thyreophorans

Ankylosauria

Among the Ankylosauria, the two main groups are the ankylosaurids and nodosaurids.

Ankylosaurids are noted by the presence of a large tail club composed of distended vertebrae that have fused into a single mass. They were heavy-set and heavily armored from head to tail in bony armor, even down to minor features such as the eyelids. Spikes and nodules, often of horn, were set into the armor. The head was flat, stocky, with little or no "neck", roughly shovel-shaped and characterized by two spikes on either side of the head approximately where the ears and cheeks were. Euoplocephalus tutus is perhaps the best-known ankylosaurid.

Nodosaurids, the other family in the Ankylosauria, may actually include the ancestors of the ankylosaurids. They lived during the middle Jurassic (approx 170 mya) on up through the late Cretaceous (66 mya) and, while armored as the ankylosaurids, did not have a tail club. Instead, the bony bumps and spikes that covered the rest of their body continued out to the tail and/or were augmented with sharp spines. Two examples of nodosaurs are Sauropelta and Edmontonia , the latter most notable for its formidable forward-pointing shoulder spikes.

Stegosauria

The suborder Stegosauria comprises Stegosauridae and Huayangosauridae. These dinosaurs lived mostly from the Middle to Late Jurassic, although some fossils have been found in the Cretaceous. Stegosaurs had very small heads with simple, leaf-like teeth. Stegosaurs possessed rows of plates and/or spikes running down the dorsal midline and elongated dorsal vertebra. It has been suggested that stegosaur plates functioned in control of body temperature (thermoregulation) and/or were used as a display to identify members of a species, as well as to attract mates and intimidate rivals. Well known stegosaurs are Stegosaurus and Kentrosaurus .

Classification

Taxonomy

While ranked taxonomy has largely fallen out of favor among dinosaur paleontologists, a few 21st century publications have retained the use of ranks, though sources have differed on what its rank should be. Most have listed Thyreophora as an unranked taxon containing the traditional suborders Stegosauria and Ankylosauria, though Thyreophora is also sometimes classified as a suborder, with Ankylosauria and Stegosauria as infraorders.

Phylogeny

Thyreophora was first named by Nopcsa in 1915. [1] Thyreophora was defined as a clade by Paul Sereno in 1998, as "all genasaurs more closely related to Ankylosaurus than to Triceratops ". Thyreophoroidea was first named by Nopcsa in 1928 and defined by Sereno in 1986, as " Scelidosaurus , Ankylosaurus , their most recent common ancestor and all of its descendants". [2] Eurypoda was first named by Sereno in 1986 and defined by him in 1998, as " Stegosaurus , Ankylosaurus, their most recent common ancestor and all of their descendants". [3] The cladogram below follows a 2011 analysis by paleontologists Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett. [4]

 Thyreophora 

Scutellosaurus Scutellosaurus.jpg

Emausaurus

 Thyreophoroidea 

Scelidosaurus Scelidosaurus harrisonii.png

 Eurypoda 

Stegosauria Stegosaurus stenops sophie wiki martyniuk flipped.png

  Ankylosauria  

Ankylosauridae Ankylosaurus magniventris reconstruction nomargin.png

Nodosauridae Edmontonia dinosaur.png

In 2020, as part of his monograph on Scelidosaurus , David Norman revised the relationships of early thyreophorans, finding that Stegosauria was the most basal branch, with Scutellosaurus , Emausaurus and Scelidosaurus being progressive stem groups to Ankylosauria, rather than to Stegosauria+Ankylosauria. A cladogram is given below: [5]

 Thyreophora 

 Stegosauria Stegosaurus stenops sophie wiki martyniuk flipped.png

 

Scutellosaurus Scutellosaurus.jpg

Emausaurus

    

Scelidosaurus Scelidosaurus harrisonii.png

Ankylosauria Edmontonia dinosaur.png

See also

Related Research Articles

<i>Stegosaurus</i> Thyreophoran stegosaurid dinosaur genus from Late Jurassic period

Stegosaurus is a genus of herbivorous, four-legged, armored dinosaur from the Late Jurassic, characterized by the distinctive kite-shaped upright plates along their backs and spikes on their tails. Fossils of the genus have been found in the western United States and in Portugal, where they are found in Kimmeridgian- to early Tithonian-aged strata, dating to between 155 and 145 million years ago. Of the species that have been classified in the upper Morrison Formation of the western US, only three are universally recognized: S. stenops, S. ungulatus and S. sulcatus. The remains of over 80 individual animals of this genus have been found. Stegosaurus would have lived alongside dinosaurs such as Apatosaurus, Diplodocus, Brachiosaurus, Ceratosaurus, and Allosaurus; the latter two may have preyed on it.

Ankylosauria Extinct order of dinosaurs

Ankylosauria is a group of herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms, similar to turtles. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are known to have first appeared in the Middle Jurassic, and persisted until the end of the Cretaceous Period. The two main families of Ankylosaurs, Nodosauridae and Ankylosauridae are primarily known from the Northern Hemisphere, but the more basal Parankylosauria are known from southern Gondwana during the Cretaceous.

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

Nodosaurus is a genus of herbivorous nodosaurid ankylosaurian dinosaur from the Late Cretaceous, the fossils of which are found in North America.

<i>Ankylosaurus</i> Ankylosaurid dinosaur genus from the Late Cretaceous Period

Ankylosaurus is a genus of armored dinosaur. Its fossils have been found in geological formations dating to the very end of the Cretaceous Period, about 68–66 million years ago, in western North America, making it among the last of the non-avian dinosaurs. It was named by Barnum Brown in 1908; it is monotypic, containing only A. magniventris. The generic name means "fused lizard", and the specific name means "great belly". A handful of specimens have been excavated to date, but a complete skeleton has not been discovered. Though other members of Ankylosauria are represented by more extensive fossil material, Ankylosaurus is often considered the archetypal member of its group, despite having some unusual features.

<i>Euoplocephalus</i> Genus of ankylosaurid dinosaur from the Late Cretaceous period

Euoplocephalus is a genus of very large, herbivorous ankylosaurid dinosaurs, living during the Late Cretaceous of Canada. It has only one named species, Euoplocephalus tutus.

<i>Scelidosaurus</i> Genus of reptiles (fossil)

Scelidosaurus is a genus of herbivorous armoured ornithischian dinosaur from the Jurassic of the British Isles.

<i>Dacentrurus</i> Extinct species of reptile

Dacentrurus, originally known as Omosaurus, is a genus of stegosaurian dinosaur from the Late Jurassic to Early Cretaceous of Europe. Its type species, Omosaurus armatus, was named in 1875, based on a skeleton found in a clay pit in the Kimmeridge Clay in Swindon, England. In 1902 the genus was renamed Dacentrurus because the name Omosaurus had already been used for a crocodylian. After 1875, half a dozen other species would be named but perhaps only Dacentrurus armatus is valid. Finds of this animal have been limited and much of its appearance is uncertain. It was a heavily built quadrupedal herbivore, adorned with plates and spikes, reaching 8–9 metres (26–30 ft) in length and 5 metric tons in body mass.

Ankylosauridae Extinct family of dinosaurs

Ankylosauridae is a family of armored dinosaurs within Ankylosauria, and is the sister group to Nodosauridae. The oldest known Ankylosaurids date to around 122 million years ago and went extinct 66 million years ago during the Cretaceous–Paleogene extinction event. These animals were mainly herbivorous and were obligate quadrupeds, with leaf-shaped teeth and robust, scute-covered bodies. Ankylosaurids possess a distinctly domed and short snout, wedge-shaped osteoderms on their skull, scutes along their torso, and a tail club.

Nodosauridae Extinct family of dinosaurs

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

<i>Paranthodon</i> Stegosaurian dinosaur genus from Early Cretaceous South Africa

Paranthodon is a genus of stegosaurian dinosaur that lived in what is now South Africa during the Early Cretaceous, between 139 and 131 million years ago. Discovered in 1845, it was one of the first stegosaurians found. Its only remains, a partial skull, isolated teeth, and fragments of vertebrae, were found in the Kirkwood Formation. British paleontologist Richard Owen initially identified the fragments as those of the pareiasaur Anthodon. After remaining untouched for years in the British Museum of Natural History, the partial skull was identified by South African paleontologist Robert Broom as belonging to a different genus; he named the specimen Palaeoscincus africanus. Several years later, Hungarian paleontologist Franz Nopcsa, unaware of Broom's new name, similarly concluded that it represented a new taxon, and named it Paranthodon owenii. Since Nopcsa's species name was assigned after Broom's, and Broom did not assign a new genus, both names are now synonyms of the current binomial, Paranthodon africanus. The genus name combines the Ancient Greek para (near) with the genus name Anthodon, to represent the initial referral of the remains.

<i>Mymoorapelta</i> Extinct genus of ornithischian dinosaur

Mymoorapelta is a monospecific genus of nodosaurid ankylosaur, a group of heavily armored, herbivorous, quadrupedal dinosaurs, from the Late Jurassic Morrison Formation of western Colorado and central Utah, USA. Few specimens are known, but the most complete one is the holotype, or name, individual from Mygatt-Moore Quarry that includes many osteoderms, a partial skull, vertebrae, and other bones which was initially described by James Kirkland and Kenneth Carpenter in 1994. It is one of the earliest known nodosaurids and one of two known from the Morrison Formation, the other being Gargoyleosaurus, and the best known nodosaurid genus from the Jurassic.

Stegosauria Extinct suborder of dinosaurs

Stegosauria is a group of herbivorous ornithischian dinosaurs that lived during the Jurassic and early Cretaceous periods. Stegosaurian fossils have been found mostly in the Northern Hemisphere, predominantly in what is now North America, Europe, Africa, South America and Asia. Their geographical origins are unclear; the earliest unequivocal stegosaurian, Huayangosaurus taibaii, lived in China.

Stegosauridae Extinct family of dinosaurs

Stegosauridae is a family of thyreophoran dinosaurs within the suborder Stegosauria. The clade is defined as all species of dinosaurs more closely related to Stegosaurus than Huayangosaurus. The name ‘Stegosauridae’ is thus a stem-based name taken from the well-represented genus – Stegosaurus. Fossil evidence of stegosaurids, dating from the Middle Jurassic through the Early Cretaceous, have been recovered from North America, Eurasia and Africa.

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

Panoplosaurus is a genus of armoured dinosaur from the Late Cretaceous of Alberta, Canada. Few specimens of the genus are known, all from the middle Campanian of the Dinosaur Park Formation, roughly 76 to 75 million years ago. It was first discovered in 1917, and named in 1919 by Lawrence Lambe, named for its extensive armour, meaning "well-armoured lizard". Panoplosaurus has at times been considered the proper name for material otherwise referred to as Edmontonia, complicating its phylogenetic and ecological interpretations, at one point being considered to have existed across Alberta, New Mexico and Texas, with specimens in institutions from Canada and the United States. The skull and skeleton of Panoplosaurus are similar to its relatives, but have a few significant differences, such as the lumpy form of the skull osteoderms, a completely fused shoulder blade, and regularly shaped plates on its neck and body lacking prominent spines. It was a quadrupedal animal, roughly 5 m (16 ft) long and 1,600 kg (3,500 lb) in weight. The skull has a short snout, with a very domed surface, and bony plates directly covering the cheek. The neck had circular groups of plates arranged around the top surface, both the forelimb and hindlimb were about the same length, and the hand may have only included three fingers. Almost the entire surface of the body was covered in plates, osteoderms and scutes of varying sizes, ranging from large elements along the skull and neck, to smaller, round bones underneath the chin and body, to small ossicles that filled in the spaces between other, larger osteoderms.

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

Emausaurus is a genus of thyreophoran or armored dinosaur from the Early Jurassic. Its fossils have been found in Mecklenburg-Vorpommern, northern Germany. Emausaurus is the only known Toarcian thyreophoran and it is also the only dinosaur from the zone of the same age with a formal name.

Polacanthinae Extinct subfamily of dinosaurs

Polacanthinae is a subfamily of ankylosaurs, most often nodosaurids, from the Late Jurassic through Early Cretaceous of Europe and potentially North America and Asia. The group is defined as the largest clade closer to Polacanthus foxii than Nodosaurus textilis or Ankylosaurus magniventris, as long as that group nests within either Nodosauridae or Ankylosauridae. If Polacanthus, and by extent Polacanthinae, falls outside either family-level clade, then the -inae suffix would be inappropriate, and the proper name for the group would be the informally defined Polacanthidae.

Genasauria Extinct clade of dinosaurs

Genasauria is a clade of extinct beaked, primarily herbivorous dinosaurs. Paleontologist Paul Sereno first named Genasauria in 1986. The name Genasauria is derived from the Latin word gena meaning ‘cheek’ and the Greek word saúra (σαύρα) meaning ‘lizard.’ It is hypothesized that Genasauria had diverged from Lesothosaurus by the Early Jurassic. Cranial features that characterize Genasauria include a medial offset of the maxillary dentition, a sprout-shaped mandibular symphysis, moderately sized coronoid process, and an edentulous anterior portion of the premaxilla. A distinguishing postcranial feature of Genasauria is a pubic peduncle of the ilium that is less robust than the ischial peduncle. Genasauria is commonly divided into Neornithischia and Thyreophora. Neornithischia is characterized by asymmetrical distributions of enamel covering the crowns of the cheek teeth, an open acetabulum, and a laterally protruding ischial peduncle of the ilium. Neornithischia includes ornithopods, pachycephalosaurs, and ceratopsians. Thyreophora is characterized by body armor and includes stegosaurs, ankylosaurs, Scelidosaurus, and Scutellosaurus.

Timeline of stegosaur research

This timeline of stegosaur research is a chronological listing of events in the history of paleontology focused on the stegosaurs, the iconic plate-backed, spike-tailed herbivorous eurypod dinosaurs that predominated during the Jurassic period. The first scientifically documented stegosaur remains were recovered from Early Cretaceous strata in England during the mid-19th century. However, they would not be recognized as a distinct group of dinosaurs until Othniel Charles Marsh described the new genus and species Stegosaurus armatus in 1877, which he regarded as the founding member of the Stegosauria. This new taxon originally included all armored dinosaurs. It was not until 1927 that Alfred Sherwood Romer implemented the modern use of the name Stegosauria as specifically pertaining to the plate-backed and spike-tailed dinosaurs.

Timeline of ankylosaur research

This timeline of ankylosaur research is a chronological listing of events in the history of paleontology focused on the ankylosaurs, quadrupedal herbivorous dinosaurs who were protected by a covering bony plates and spikes and sometimes by a clubbed tail. Although formally trained scientists did not begin documenting ankylosaur fossils until the early 19th century, Native Americans had a long history of contact with these remains, which were generally interpreted through a mythological lens. The Delaware people have stories about smoking the bones of ancient monsters in a magic ritual to have wishes granted and ankylosaur fossils are among the local fossils that may have been used like this. The Native Americans of the modern southwestern United States tell stories about an armored monster named Yeitso that may have been influenced by local ankylosaur fossils. Likewise, ankylosaur remains are among the dinosaur bones found along the Red Deer River of Alberta, Canada where the Piegan people believe that the Grandfather of the Buffalo once lived.

Parankylosauria Extinct group of dinosaurs

Parankylosauria is a group of basal ankylosaurian dinosaurs known from the Cretaceous of South America, Antarctica, and Australia. It is thought the group split from other ankylosaurs during the mid-Jurassic period, despite this being unpreserved in the fossil record.

References

  1. Nopcsa, Ferenc (1915). "Die dinosaurier der Siebenbürgischen landesteile Ungarns" (PDF). Mitteilungen aus dem Jahrbuche der KGL. 23: 1–24.
  2. Sereno, Paul (1986). "Phylogeny of the bird-hipped dinosaurs (order Ornithischia)". National Geographic Research. 2 (2): 234–256.
  3. Paul, Sereno (1998). "A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 210 (1): 41–83. doi:10.1127/njgpa/210/1998/41.
  4. Richard S. Thompson, Jolyon C. Parish, Susannah C. R. Maidment and Paul M. Barrett (2011). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. 10 (2): 301–312. doi:10.1080/14772019.2011.569091. S2CID   86002282.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. Norman, David B (2021-01-01). "Scelidosaurus harrisonii (Dinosauria: Ornithischia) from the Early Jurassic of Dorset, England: biology and phylogenetic relationships". Zoological Journal of the Linnean Society. 191 (1): 1–86. doi:10.1093/zoolinnean/zlaa061. ISSN   0024-4082.