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.
|Skeletons of Gastonia burgei, North American Museum of Ancient Life|
The family Polacanthidae was named by Wieland in 1911 to refer to a group of ankylosaurs which seemed to him intermediate between the ankylosaurids and nodosaurids. This grouping was ignored by most researchers until the late 1990s, when it was used as a subfamily (Polacanthinae) by Kirkland for a natural group recovered by his 1998 analysis suggesting that Polacanthus, Gastonia, and Mymoorapelta were closely related within the family Ankylosauridae. Kenneth Carpenter resurrected the name Polacanthidae for a similar group which he also found to be closer to ankylosaurids than to nodosaurids. Carpenter became the first to define Polacanthidae as all dinosaurs closer to Gastonia than to either Edmontonia or Euoplocephalus. Most subsequent researchers placed polacanthines as primitive ankylosaurids, though mostly without any rigorous study to demonstrate this idea. The first comprehensive study of 'polacanthid' relationships, published in 2012, found that they are either an unnatural grouping of primitive nodosaurids, or a valid subfamily at the base of Nodosauridae.
The clade Nodosauridae was first defined by Paul Sereno in 1998 as "all ankylosaurs closer to Panoplosaurus than to Ankylosaurus," a definition followed by Vickaryous, Teresa Maryańska, and Weishampel in 2004. Vickaryous et al. considered two genera of nodosaurids to be of uncertain placement (incertae sedis): Struthiosaurus and Animantarx, and considered the most primitive member of the Nodosauridae to be Cedarpelta. The cladogram below follows the most resolved topology from a 2013 analysis, which used an expanded version of the data presented by Richard S. Thompson and colleagues (2012). The placement of Polacanthinae follows its original definition by Kenneth Carpenter in 2001.
The near simultaneous appearance of nodosaurids in both North America and Europe is worthy of consideration. 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 from the Arundel Clay of the Potomac Group of Maryland, which dates near the Aptian–Albian boundary. The Propanoplosaurus hatchling from the base of the underlying Patuxent Formation, date to the upper Aptian, making Propanoplosaurus the oldest nodosaurid.
Polacanthines 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, pushes the groups date of evolution back to at least the "middle" Aptian. The separation of advanced nodosaurids 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.
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.Ankylosauria
Ankylosauria is a group of mainly herbivorous dinosaurs of the order Ornithischia. It includes the great majority of dinosaurs with armor in the form of bony osteoderms. Ankylosaurs were bulky quadrupeds, with short, powerful limbs. They are known to have first appeared in the early Jurassic Period, and persisted until the end of the Cretaceous Period. They have been found on every continent. The first dinosaur discovered in Antarctica was the ankylosaurian Antarctopelta, fossils of which were recovered from Ross Island in 1986.
Ankylosauria was first named by Henry Fairfield Osborn in 1923. In the Linnaean classification system, the group is usually considered either a suborder or an infraorder. It is contained within the group Thyreophora, which also includes the stegosaurs, armored dinosaurs known for their combination of plates and spikes.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.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.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.Gastonia (dinosaur)
Gastonia is a genus of herbivorous ankylosaurian dinosaur from the Early Cretaceous of North America, around 125 million years ago. It is often considered a nodosaurid closely related to Polacanthus. Gastonia has a sacral shield and large shoulder spikes.Hoplitosaurus
Hoplitosaurus (meaning "Hoplite lizard") was a genus of armored dinosaur related to Polacanthus. It was named from a partial skeleton found in the ?Barremian-age Lower Cretaceous Lakota Formation of Custer County, South Dakota. It is an obscure genus which has been subject to some misinterpretation of its damaged remains. Although there was a push to synonymize it with Polacanthus in the late 1980s-early 1990s, Hoplitosaurus has been accepted as a valid albeit poorly known genus in more recent reviews.Hylaeosaurus
Hylaeosaurus ( hy-LEE-o-SOR-əs; Greek: hylaios/ὑλαῖος "belonging to the forest" and sauros/σαυρος "lizard") is a herbivorous ankylosaurian dinosaur that lived about 136 million years ago, in the late Valanginian stage of the early Cretaceous period of England.
Hylaeosaurus was one of the first dinosaurs to be discovered, in 1832 by Gideon Mantell. In 1842 it was one of the three dinosaurs Richard Owen based the Dinosauria on. Four species were named in the genus, but only the type species Hylaeosaurus armatus is today considered valid. Only limited remains have been found of Hylaeosaurus and much of its anatomy is unknown. It might have been a basal nodosaurid, although a recent cladistic analysis recovers it as a basal ankylosaurid.Hylaeosaurus was about five metres long. It was an armoured dinosaur. It carried at least three long spines on its shoulder.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.Peloroplites
Peloroplites (from Greek pelor "monster", and hoplites, "armoured soldier") is a genus of nodosaurid armored dinosaur from Lower Cretaceous rocks of Utah, United States. It is known from a partial skull and partial postcranial remains from the base of the Mussentuchit Member of the Cedar Mountain Formation, deposited during the Albian-Cenomanian boundary, about 104.46 to 98.37 million years ago, and was found in Emery County, Utah. It was named in 2008 by Kenneth Carpenter and colleagues.
Peloroplites was about 5 to 5.5 meters (16 to 18 ft) long, comparable to its approximate contemporary Sauropelta. It is one of the largest known nodosaurids, and came from a time when ankylosaurians in general were attaining large sizes.Polacanthoides
Polacanthoides (meaning Polacanthus like) is an extinct genus of nodosaurid dinosaur from Europe. It lived about 140 to 135 million years ago in what is now England. It was named by Nopsca in 1928. The type specimen is BMNH 2584. It is a possible junior synonym of Hylaeosaurus and Polacanthus. It is now considered to be a nomen dubium or a chimera.Polacanthus
Polacanthus, deriving its name from the Ancient Greek polys-/πολύς- "many" and akantha/ἄκανθα "thorn" or "prickle", is an early armoured, spiked, plant-eating ankylosaurian dinosaur from the early Cretaceous period of England.
In the genus Polacanthus several species have been named but only the type species Polacanthus foxii is today seen as valid.
Polacanthus was a quadrupedal ornithischian or "bird-hipped" dinosaur. It lived 130 to 125 million years ago in what is now western Europe. Polacanthus foxii was named after a find on the Isle of Wight in 1865. There are not many fossil remains of this creature, and some important anatomical features, such as its skull, are poorly known. Early depictions often gave it a very generic head as it was only known from the rear half of the creature. It grew to about 5 metres (16 ft) long. Its body was covered with armour plates and spikes. It possibly was a basal member of the Nodosauridae.Silvisaurus
Silvisaurus, from the Latin silva "woodland" and Greek sauros "lizard", is a nodosaurid ankylosaur from the middle Cretaceous period.Taohelong
Taohelong is a genus of nodosaurid dinosaur known from Lower Cretaceous rocks in north-central China.
Taohelong is based on Gansu Dinosaur Museum (GSDM) 00021, fossils including a tail vertebra, ribs, a left ilium (the main bone of the hip), and bony armor recovered from the Hekou Group in the Lanzhou-Minhe Basin. The animal's armor includes part of a "sacral shield", a carpet of osteoderms over the hips found in some other ankylosaurians. Taohelong was named and described in 2013 by Yang Jing-Tao, You Hai-Lu, Li Da-Qing, and Kong De-Lai. The type species is Taohelong jinchengensis. The generic name means "dragon (long) of the river (he) Tao". The specific name refers to the provenance at Jincheng.The describers established some diagnostic traits. The neural channel of the tail vertebra has a cross-section like an inverted trapezium. In top view the profile of the outer rim of the ilium is like a mirrored "S". The osteoderms of the sacral shield are irregular in both shape and size.Taohelong was placed in the Nodosauridae, more precisely in the Polacanthinae. Yang et al. performed a phylogenetic analysis and found Taohelong to be the sister taxon to Polacanthus foxii, making it the first polacanthine to be described from Asia.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.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.