Hylaeosaurus

Hylaeosaurus (/haɪˌliːoʊˈsɔːrəs/ 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.[1]

Hylaeosaurus was about five metres long. It was an armoured dinosaur. It carried at least three long spines on its shoulder.

Hylaeosaurus
Temporal range: Early Cretaceous, 140–136 Ma
Hylaeosaurus armatus
Holotype NMH R3775
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Order: Ornithischia
Suborder: Ankylosauria
Family: Nodosauridae
Genus: Hylaeosaurus
Mantell, 1833
Species:
H. armatus
Binomial name
Hylaeosaurus armatus
Mantell, 1833
Synonyms

History of discovery

Hylaeosaurus fossil illustration
Illustration of the holotype in its matrix, 1868

The first Hylaeosaurus fossils were discovered in West Sussex. On 20 July 1832, fossil collector Gideon Mantell wrote to Professor Benjamin Silliman that when a gunpowder explosion had demolished a quarry rock face in Tilgate Forest, several of the boulders freed showed the bones of a saurian. A local fossil dealer had assembled the about fifty pieces, described by him as a "great consarn of bites and boanes". Having doubts about the value of the fragments, Mantell had nevertheless purchased the pieces and soon discovered they could be united into a single skeleton, partially articulated. Mantell was delighted with the find because previous specimens of Megalosaurus and Iguanodon had consisted of single bone elements. The discovery in fact represented the most complete non-avian dinosaur skeleton known at the time. He was strongly inclined to describe the find as belonging to the latter genus, but during a visit by William Clift, the curator of the Royal College of Surgeons of England museum, and his assistant John Edward Gray, he began to doubt the identification. Clift was the first to point out that several plates and spikes were probably part of a body armour, attached to the back or sides of the rump.[2] In November 1832 Mantell decided to create a new generic name: Hylaeosaurus. It is derived from the Greek ὑλαῖος, hylaios, "of the wood". Mantell originally claimed the name Hylaeosaurus meant "forest lizard", after the Tilgate Forest in which it was discovered.[3] Later, he claimed that it meant "Wealden lizard" ("wealden" being another word for forest), in reference to the Wealden Group, the name for the early Cretaceous geological formation in which the dinosaur was first found.[4]

Hylæosaurus
Dermal spine

On 30 November Mantell sent the piece to the Geological Society of London. Shortly afterwards he himself went to London and on 5 December during a meeting of the Society, in which he for the first time personally met Richard Owen, reported on the find to large acclaim. However, he was also informed that a paper he had already prepared, was a third too long. On advice of his friend Charles Lyell, Mantell decided instead of rewriting the paper, to publish an entire book on his fossil finds and dedicate a chapter to Hylaeosaurus. Within three weeks Mantell composed the volume from earlier notes. On 17 December Henry De la Beche warned him that the changed conventions in nomenclature implied that only he who provided a full species name was recognised as the author: to Hylaeosaurus a specific name needed to be added.[2] Mantell on 19 December chose armatus, Latin for "armed" or "armoured", in reference to the spikes and armour plates. As Mantell himself put it: "there appears every reason to conclude that either its back was armed with a formidable row of spines, constituting a dermal fringe, or that its tail possessed the same appendage". In May 1833 his The Geology of the South-East of England appeared, hereby validly naming the type species Hylaeosaurus armatus. Mantell published a lithograph of his find in The Geology of the South-East of England;[5] and another drawing in the fourth edition of The Wonders of Geology, in 1840.

Crystal Palace Hylaeosaurus
Crystal Palace model by Benjamin Waterhouse Hawkins

Hylaeosaurus is the most obscure of the three animals used by Sir Richard Owen to first define the new group Dinosauria, in 1842, the other genera being Megalosaurus and Iguanodon. Not only has Hylaeosaurus received less public attention, despite being included in the life-sized models by Benjamin Waterhouse Hawkins placed in the Crystal Palace Park, it also never functioned as a "wastebasket taxon". Owen in 1840 developed a new hypothesis about the spikes; noting they were asymmetrical he correctly rejected the notion they formed a row on the back but incorrectly assumed they were gastralia or belly-ribs.

The original specimen, recovered by Gideon Mantell from the Tilgate Forest, was later acquired by the Natural History Museum of London. It has the inventory number NHMUK 3775 (earlier BMNH R3775). It was found in a layer of the Grinstead Clay Formation dating from the Valanginian, about 137 million year old. This holotype is the best specimen and is composed of the front end of a skeleton minus most of the head and the forelimbs, though only the parts on the face of the stone block are easily studied. The block measures about 135 by 75 centimetres. The holotype consists of the rear of the skull and perhaps lower jaws, ten vertebrae, both scapulae, both coracoids and several spikes and armour plates. The skeleton is viewed from below. For a long time no further preparation had taken place, beyond the assembly and chiselling out by Mantell himself, but in the early twenty-first century the museum began to further free the bones by both chemical and mechanical means.[6] The information gained hereby has not yet been published. Several finds from the mainland of Britain have been referred to Hylaeosaurus armatus.[7][8] However, in 2011 Paul Barrett and Susannah Maidment concluded that only the holotype could with certainty be associated with the species, in view of the presence of Polacanthus in the same layers.[9]

Hylaeosaurus sp. spike
Referred spike from Germany

Additional remains have been referred to Hylaeosaurus, from the Isle of Wight, (the Ardennes of) France,[10] Germany,[11] Spain[12] and Romania.[13] The remains from France may actually belong to Polacanthus and the other references are today also considered dubious.[6][14] However, possible remains were reported from Germany in 2013: a spike, specimen DLM 537 and the lower end of a humerus, specimen GPMM A3D.3, which were referred to a Hylaeosaurus sp.[15]

Later species

Hylaeosaurus oweni
Specimen referred to H. oweni

Hylaeosaurus armatus Mantell 1833 is currently considered the only valid species in the genus. However, three others have been named. In 1844, Mantell named Hylaeosaurus oweni based on the same specimen as H. armatus, wanting to honour Richard Owen.[16] This has been sunk as a junior objective synonym of H. armatus.[7] In 1956 Alfred Romer renamed Regnosaurus into Hylaeosaurus northhamptoni.[17] Polacanthus Owen 1865 was by Walter Coombs in 1971 renamed into Hylaeosaurus foxii.[18] These last two names have found no acceptance; H. foxii remained an invalid nomen ex dissertatione. It has also been suggested that Polacanthus is simply the same species as Hylaeosaurus armatus and thus a junior synonym, but there are a number of differences in their osteology.

Sometimes bones from the Hylaeosaurus material have later been made separate species. In 1928 Franz Nopcsa made specimen BMNH 2584, a left scapula referred by Mantell to H. armatus,[19] part of the type material of Polacanthoides ponderosus.[20] Though in 1978 synonymised with Hylaeosaurus,[21] Polacanthoides is today considered a nomen dubium,[22] an indeterminate member of the Thyreophora.

Description

Hylaeosaurus spikes
Diagram showing possible arrangement of neck-spikes

Gideon Mantell originally estimated that Hylaeosaurus was about 7.6 metres (25 ft) long, or about half the size of the other two original dinosaurs, Iguanodon and Megalosaurus. At the time, he modelled the animal after a modern lizard. Modern estimates range up to 6 metres (20 ft) in length.[23] Gregory S. Paul in 2010 estimated the length at 5 metres (16 ft), the weight at 2 tonnes (2.0 long tons; 2.2 short tons).[24] Some estimates are considerably lower: in 2001 Darren Naish e.a. gave a length of 3–4 metres (9.8–13.1 ft).[14]

Many details about the build of Hylaeosaurus are unknown, especially if the material is strictly limited to the holotype. Maidment gave two autapomorphies, unique derived traits: the scapula did not fuse with the coracoid, even when the animal was of a considerable size; there were three long spines on its shoulder.[9] Even these traits are not very distinctive: Mantell and Owen had attributed the lack of fusion to ontogeny and the total number of spines cannot be observed. Hylaeosaurus is often styled as a fairly typical nodosaur, with rows of armour plating on the back and tail combined with a relatively long head, equipped with a beak used to crop low-lying vegetation.

In 2001 the skull and lower jaws remains were described by Kenneth Carpenter. The damaged and shifted skull elements provided little information. The quadrate is laterally bowed. The quadratojugal has a high attachment point on the shaft of the quadrate. A triangular postorbital horn was present.[25]

The spines at the shoulder are curved to the rear, long, flattened, narrow and pointed. Their underside shows a shallow trough. The front spine is the longest at 42.5 centimetres; to the rear the spines become gradually shorter and wider. A fourth spine, of about the same build but more forward-pointing, is present immediately behind the skull. In 2013 Sven Sachs and Jahn Hornung suggested a configuration in which there were five lateral neck spines, the new German spine having a morphology adapted to fit in the third position.[15]

Phylogeny

Hylaeosaurus sacrum
Referred sacral vertebrae
Hylaeosaurus sp. humerus
Partial referred humerus from Germany

Hylaeosaurus was the first ankylosaur discovered. Until well into the twentieth century its exact affinities would remain uncertain. In 1978 Coombs assigned it to the Nodosauridae within the Ankylosauria.[21] This is still a usual classification, Hylaeosaurus being recovered as a basal nodosaurid in most exact cladistic analyses, sometimes more precisely as a member of the Polacanthinae, and thus being related to Gastonia and Polacanthus. However, in the 1990s, the polacanthines were sometimes seen as basal ankylosaurids, because they were mistakenly believed to have small tail-clubs. A more popular alternative today is that they formed a Polacanthidae, a basal group outside of the nodosaurids + ankylosaurids clade.

A 2012 study finding Hylaeosaurus to be a basal nodosaurid but not a polacanthine is shown in this cladogram:[26]

Nodosauridae

Antarctopelta

Mymoorapelta

Hylaeosaurus

Anoplosaurus

Tatankacephalus

Horshamosaurus

Polacanthinae

Gargoyleosaurus

Hoplitosaurus

Gastonia

Peloroplites

Polacanthus

Struthiosaurus

Zhejiangosaurus

Hungarosaurus

Animantarx

Niobrarasaurus

Nodosaurus

Pawpawsaurus

Sauropelta

Silvisaurus

Stegopelta

Texasetes

Edmontonia

Panoplosaurus

See also

References

  1. ^ Arbour, Victoria M; Zanno, Lindsay E; Gates, Terry (2016). "Ankylosaurian dinosaur palaeoenvironmental associations were influenced by extirpation, sea-level fluctuation, and geodispersal". Palaeogeography, Palaeoclimatology, Palaeoecology. 449: 289–299. doi:10.1016/j.palaeo.2016.02.033.
  2. ^ a b Dennis R. Dean, 1999, Gideon Mantell and the Discovery of Dinosaurs, Cambridge University Press, 315 pp
  3. ^ Mantell, Gideon Algernon (1833). "Observations on the remains of the Iguanodon, and other fossil reptiles, of the strata of Tilgate Forest in Sussex". Proceedings of the Geological Society of London. 1: 410–411.
  4. ^ Mantell, G.A., 1838, The Wonders of Geology or a Familiar Exposition of Geological Phenomena, 2 vols, Relfe and Fletcher, London
  5. ^ G.A. Mantell. 1833. The Geology of the South-East of England. Longman Ltd., London
  6. ^ a b Naish, D.; Martill, D.M. (2008). "Dinosaurs of Great Britain and the role of the Geological Society of London in their discovery: Ornithischia". Journal of the Geological Society, London. 165 (3): 613–623. doi:10.1144/0016-76492007-154.
  7. ^ a b Pereda-Suberbiola, J (1993). "Hylaeosaurus, Polacanthus, and the systematics and stratigraphy of Wealden armoured dinosaurs". Geological Magazine. 130 (6): 767–781. doi:10.1017/s0016756800023141.
  8. ^ Barrett, P.M. (1996). "The first known femur of Hylaeosaurus armatus and reidentification of ornithopod material in The Natural History Museum, London". Bulletin of the Natural History Museum, Geology Series. 52: 115–118.
  9. ^ a b Barrett, P.M. and Maidment, S.C.R., 2011, "Wealden armoured dinosaurs". In: Batten, D.J. (ed.). English Wealden fossils. Palaeontological Association, London, Field Guides to Fossils 14, 769 pp
  10. ^ Corroy, G (1922). "Les reptiles néocomiens et albiens du Bassin de Paris". Comptes Rendus de l'Académie des Sciences de Paris. 172: 1192–1194.
  11. ^ Koken, E (1887). "Die Dinosaurier, Crocodiliden und Sauropterygier des norddeutschen Wealden". Geologische und Palaeontologische Abhandlungen. 3: 311–420.
  12. ^ Sanz, J.L. (1983). "A nodosaurid ankylosaur from the Lower Cretaceous of Salas de los Infantes (Province of Burgos, Spain)". Geobios. 16 (5): 615–621. doi:10.1016/s0016-6995(83)80038-2.
  13. ^ E. Posmosanu, 2003, "The palaeoecology of the dinosaur fauna from a Lower Cretaceous bauxite deposit from Bihor (Romania)". In: A. Petculescu & E. Stiuca (eds.), Advances in Vertebrate Paleontology: Hen to Panta. Romanian Academy, "Emil Racovita" Institute of Speleology, Bucarest pp. 121-124
  14. ^ a b Naish, D. and Martill, D.M., 2001, "Armoured Dinosaurs: Thyreophorans". In: Martill, D.M., Naish, D., (editors). Dinosaurs of the Isle of Wight. Palaeontological Association Field Guides to Fossils 10. pp. 147–184
  15. ^ a b Sachs, S.; Hornung, J. J. (2013). Evans, David C (ed.). "Ankylosaur Remains from the Early Cretaceous (Valanginian) of Northwestern Germany". PLoS ONE. 8 (4): e60571. doi:10.1371/journal.pone.0060571. PMC 3616133. PMID 23560099.
  16. ^ Mantell, G.A. 1844. The Medals of Creation: or first lessons in geology and in the study of organic remains. London Volume 2, pp. 587-876
  17. ^ Romer, A.S. 1956. Osteology of the Reptiles. University of Chicago Press, Chicago
  18. ^ Coombs, W. 1971. The Ankylosauria. Ph.D. thesis, New York: Columbia University
  19. ^ Mantell, G.A. (1841). "Memoir on a portion of the lower jaw of the Iguanodon and on the remains of the Hylaeosaurus and other saurians, discovered in the strata of Tilgate Forest, in Sussex". Philosophical Transactions of the Royal Society of London. 131: 131–151. doi:10.1098/rstl.1841.0013.
  20. ^ Nopcsa, F., 1928, "Palaeontological notes on Reptiles", Geologica Hungarica, Series Palaeontologica, tomus, 1, -Pasc. 1, p. 1-84
  21. ^ a b Coombs, W.P. (1978). "The families of the ornithischian dinosaur order Ankylosauria". Palaeontology. 21 (1): 143–170.
  22. ^ Blows, W.T. (1987). "The armoured dinosaur Polacanthus foxi from the Lower Cretaceous of the Isle of Wight". Palaeontology. 30 (3): 557–580.
  23. ^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 157. ISBN 978-1-84028-152-1.
  24. ^ Paul, G.S., 2010, The Princeton Field Guide to Dinosaurs, Princeton University Press p. 228
  25. ^ Carpenter, K., 2001, "Skull of the polacanthid ankylosaur Hylaeosaurus armatus Mantell, 1833, from the Lower Cretaceous of England", pp 169–172 In: Carpenter, K. (ed.). The armored dinosaurs. Indiana University Press, Bloomington and Indianapolis, 525 pp
  26. ^ Thompson, Richard S.; Parish, Jolyon C.; Maidment, Susannah C. R.; Barrett, Paul M. (2012). "Phylogeny of the ankylosaurian dinosaurs (Ornithischia: Thyreophora)". Journal of Systematic Palaeontology. 10 (2): 301–312. doi:10.1080/14772019.2011.569091.

External links

1833 in paleontology

Paleontology or palaeontology is the study of prehistoric life forms on Earth through the examination of plant and animal fossils. This includes the study of body fossils, tracks (ichnites), burrows, cast-off parts, fossilised feces (coprolites), palynomorphs and chemical residues. Because humans have encountered fossils for millennia, paleontology has a long history both before and after becoming formalized as a science. This article records significant discoveries and events related to paleontology that occurred or were published in the year 1833.

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.

Berriasian

In the geological timescale, the Berriasian is an age or stage of the Early Cretaceous. It is the oldest, or lowest, subdivision in the entire Cretaceous. It spanned the time between 145.0 ± 4.0 Ma and 139.8 ± 3.0 Ma (million years ago). The Berriasian succeeds the Tithonian (part of the Jurassic) and precedes the Valanginian.

Crystal Palace Dinosaurs

The Crystal Palace Dinosaurs are a series of sculptures of dinosaurs and other extinct animals, incorrect by modern standards, in the London borough of Bromley's Crystal Palace Park. Commissioned in 1852 to accompany the Crystal Palace after its move from the Great Exhibition in Hyde Park, they were unveiled in 1854 as the first dinosaur sculptures in the world. The models were designed and sculpted by Benjamin Waterhouse Hawkins under the scientific direction of Sir Richard Owen, representing the latest scientific knowledge at the time. The models, also known as Dinosaur Court, were classed as Grade II listed buildings from 1973, extensively restored in 2002, and upgraded to Grade I listed in 2007.

The models represent 15 genera of extinct animals, not all dinosaurs. They are from a wide range of geological ages, and include true dinosaurs, ichthyosaurs, and plesiosaurs mainly from the Mesozoic era, and some mammals from the more recent Cenozoic era.

Dinosaur classification

Dinosaur classification began in 1842 when Sir Richard Owen placed Iguanodon, Megalosaurus, and Hylaeosaurus in "a distinct tribe or suborder of Saurian Reptiles, for which I would propose the name of Dinosauria." In 1887 and 1888 Harry Seeley divided dinosaurs into the two orders Saurischia and Ornithischia, based on their hip structure. These divisions have proved remarkably enduring, even through several seismic changes in the taxonomy of dinosaurs.

The largest change was prompted by entomologist Willi Hennig's work in the 1950s, which evolved into modern cladistics. For specimens known only from fossils, the rigorous analysis of characters to determine evolutionary relationships between different groups of animals (clades) proved incredibly useful. When computer-based analysis using cladistics came into its own in the 1990s, paleontologists became among the first zoologists to almost wholeheartedly adopt the system. Progressive scrutiny and work upon dinosaurian interrelationships, with the aid of new discoveries that have shed light on previously uncertain relationships between taxa, have begun to yield a stabilizing classification since the mid-2000s. While cladistics is the predominant classificatory system among paleontology professionals, the Linnean system is still in use, especially in works intended for popular distribution.

Forest Marble Formation

The Forest Marble is a geological formation in England. Part of the Great Oolite Group, it dates to back to the late Bathonian stage of the Middle Jurassic.

Hastings Beds

The Hastings Beds is a geological unit that includes interbedded clays, silts, siltstones, sands and sandstones in the High Weald of southeast England. These strata make up the component geological formations of the Ashdown Formation, the Wadhurst Clay Formation and the Tunbridge Wells Sand Formation. The term 'Hastings Beds' has been superseded and the component formations are included in the Wealden Group.The sediments of the Weald, including the Hastings Beds, were deposited during the Early Cretaceous Period, which lasted for approximately 40 million years from 140 to 100 million years ago. The Hastings Beds are of Early Berriasian to Late Valanginian age. The Group takes its name from the fishing town of Hastings in East Sussex.

Dinosaur remains are among the fossils that have been recovered from the included formations.

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.

Oplosaurus

Oplosaurus (meaning "armed or weapon lizard" or "armoured lizard"; see below for discussion) was a genus of sauropod dinosaur from the Barremian-age Lower Cretaceous Wessex Formation of the Isle of Wight, England. It is known from a single tooth usually referred to the contemporaneous "wastebasket taxon" Pelorosaurus, although there is no solid evidence for this.

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.

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.

Regnosaurus

Regnosaurus (meaning "Sussex lizard") is a genus of herbivorous stegosaurian dinosaur that lived during the Early Cretaceous Period in what is now England.

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.

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.

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.The first scientifically documented ankylosaur remains were recovered from Early Cretaceous rocks in England and named Hylaeosaurus armatus by Gideon Mantell in 1833. However, the Ankylosauria itself would not be named until Henry Fairfield Osborn did so in 1923 nearly a hundred years later. Prior to this, the ankylosaurs had been considered members of the Stegosauria, which included all armored dinosaurs when Othniel Charles Marsh named the group in 1877. 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 of the Jurassic that form the ankylosaurs' nearest relatives. The next major revision to ankylosaur taxonomy would not come until Walter Coombs divided the group into the two main families paleontologists still recognize today; the nodosaurids and ankylosaurids. Since then, many new ankylosaur genera and species have been discovered from all over the world and continue to come to light. Many fossil ankylosaur trackways have also been recognized.

Timeline of paleontology

Timeline of paleontology

6th century B.C. — The pre-Socratic Greek philosopher Xenophanes of Colophon argues that fossils of marine organisms show that dry land was once under water.

1027 — The Persian naturalist, Avicenna, explains the stoniness of fossils in The Book of Healing by proposing the theory of petrifying fluids (succus lapidificatus).

1031-1095 — The Chinese naturalist, Shen Kuo, uses evidence of marine fossils found in the Taihang Mountains to infer geological processes caused shifting of seashores over time, and uses petrified bamboos found underground in Yan'an, to argue for gradual climate change.

1320-1390 — Avicenna's theory of petrifying fluids (succus lapidificatus) was elaborated on by Albert of Saxony.

c. 1500 — Leonardo da Vinci uses ichnofossils to complement his hypothesis concerning the biogenic nature of body fossils.

1665 — In his book Micrographia Robert Hooke compares petrified wood to wood, concludes that petrified wood formed from wood soaked in mineral-rich water, and argues that fossils like Ammonite shells were produced the same way, sparking debate over the organic origin of fossils and the possibility of extinction.

1669 — Nicholas Steno writes that some kinds of rock formed from layers of sediment deposited in water, and that fossils were organic remains buried in the process.

1770 — The fossilised bones of a huge animal are found in a quarry near Maastricht in the Netherlands. In 1808 Georges Cuvier identified it as an extinct marine reptile and in 1822 William Conybeare named it Mosasaurus.

1789 — The skeleton of a large animal is unearthed in Argentina. In 1796 Cuvier reports that it had an affinity to modern tree sloths and names it Megatherium.

1796 — Cuvier presents a paper on living and fossil elephants that shows that mammoths were a different species from any living elephant. He argues that this proved the reality of extinction, which he attributes to a geological catastrophe.

1800 — Cuvier writes that a drawing of a fossil found in Bavaria shows a flying reptile; in 1809 he names it Pterodactyl.

1808 — Cuvier and Alexandre Brongniart publish preliminary results of their survey of the geology of the Paris Basin that uses the fossils found in different strata to reconstruct the geologic history of the region.

1811 — Mary Anning and her brother Joseph discover the fossilised remains of an ichthyosaur at Lyme Regis.

1815 — William Smith published The Map that Changed the World, the first geologic map of England, Wales, and southern Scotland, using fossils to correlate rock strata.

1821 — William Buckland analyzes Kirkdale Cave in Yorkshire, containing the bones of lions, elephants and rhinoceros, and concludes it was a prehistoric hyena den.

1821-1822 — Mary Anning discovers the world's first Plesiosaur skeleton at Lyme Regis.

1822 — Mary Ann Mantell and Gideon Mantell discover fossil teeth of the dinosaur Iguanodon.

1822 — The editor of the French journal Journal de Phisique, Henri Marie Ducrotay de Blainville, invents the word "paleontologie" for the reconstruction of ancient animals and plants from fossils.

1823 — Buckland finds a human skeleton with mammoth remains at Paviland Cave on the Gower Peninsula, but at the time it is not accepted that this showed they coexisted.

1824 — Buckland finds lower jaw of the carnivorous dinosaur Megalosaurus.

1829 — Buckland publishes paper on work he and Mary Anning had done identifying and analyzing fossilized feces found at Lyme Regis and elsewhere. Buckland coins the term coprolite for them, and uses them to analyze ancient food chains.

1830 — The Cuvier–Geoffroy debate in Paris on the determination of animal structure

1831 — Mantell publishes an influential paper entitled "The Age of Reptiles" summarizing evidence of an extended period during which large reptiles had been the dominant animals.

1832 — Mantell finds partial skeleton of the dinosaur Hylaeosaurus.

1836 — Edward Hitchcock describes footprints (Eubrontes and Otozoum) of giant birds from Jurassic formations in Connecticut. Later they would be recognized as dinosaur tracks.

1841 — Anatomist Richard Owen creates a new order of reptiles, dinosauria, for animals: Iguanodon, Megalosaurus, and Hylaeosaurus, found by Mantell and Buckland.

1841 — The first global geologic timescale is defined by John Phillips based on the type of fossils found in different rock layers. He coins the term Mesozoic for what Mantell had called the age of reptiles.

1856 — Fossils are found in the Neander Valley in Germany that Johann Carl Fuhlrott and Hermann Schaaffhausen recognize as a human different from modern people. A few years later William King names Homo neanderthalensis.

1858 — The first dinosaur skeleton found in the United States, Hadrosaurus, is excavated and described by Joseph Leidy.

1859 — Charles Darwin publishes On The Origin of Species.

1861 — The first Archaeopteryx, skeleton is found in Bavaria, Germany, and recognized as a transitional form between reptiles and birds.

1869 — Joseph Lockyer starts the scientific journal Nature

1871 — Othniel Charles Marsh discovers the first American pterosaur fossils.

1874-77 — Marsh finds a series of Equid fossils in the American West that shed light on the Evolution of the horse.

1877 — The first Diplodocus skeleton is found near Cañon City, Colorado.

1891 — Eugene Dubois discovers fossils of Java Man (Homo erectus) in Indonesia.

1901 — Petroleum geologist W.W. Orcutt recovers first fossils from the La Brea Tar Pits in Southern California, a rich source of ice age mammal remains.

1905 — Tyrannosaurus rex is described and named by Henry Fairfield Osborn.

1909 — Cambrian fossils in the Burgess Shale are discovered by Charles Walcott.

1912 — Continental Drift is proposed by Alfred Wegener, leading to plate tectonics, which explained many patterns of ancient biogeography revealed by the fossil record.

1912 — Charles Dawson announces discovery of Piltdown Man in England, a hoax that would confuse paleoanthropology until the fossils were revealed as forgeries in 1953.

1912-15 — Spinosaurus is found in North Africa and is speculated to be the largest terrestrial predator that ever lived.

1920 — Andrew Douglass proposes dendrochronology (tree-ring dating).

1924 — Raymond Dart examines fossils of Taung Child, found by quarrymen in South Africa, and names Australopithecus africanus.

1944 — The publication of Tempo and Mode in Evolution by George Gaylord Simpson integrates paleontology into the modern evolutionary synthesis.

1946 — Reginald Sprigg discovers fossils of the Ediacaran biota in Australia. In the 1960s Martin Glaessner would show that they were pre-Cambrian.

1947 — Willard Libby introduces carbon-14 dating.

1953 — Stanley A. Tyler discovers microfossils in the gunflint chert formation of cyanobacteria that created pre-Cambrian stromatolites approximately 2 billion years ago.

1967 — Paul S. Martin proposes the overkill hypothesis, that the extinction of the Pleistocene megafauna in North America resulted from over hunting by Native Americans.

1972 — Niles Eldredge and Stephen Jay Gould propose punctuated equilibrium, claiming that the evolutionary history of most species involves long intervals of stasis between relatively short periods of rapid change.

1974 — Donald Johanson and Tom Gray discover a 3.5 million-year-old female hominid fossil that is 40% complete and name it "Lucy".

1980 — Luis Alvarez, Walter Alvarez, Frank Asaro, and Helen Michel propose the Alvarez hypothesis, that a comet or asteroid struck the Earth 66 million years ago causing the Cretaceous–Paleogene extinction event, including the extinction of the non-avian dinosaurs, and enriching the iridium in the K–T boundary.

1982 — Jack Sepkoski and David M. Raup publish a statistical analysis of the fossil record of marine invertebrates that shows a pattern (possibly cyclical) of repeated mass extinctions.

1984 — Hou Xianguang discovers the Maotianshan Shales Cambrian fossil site in the Yunnan province of China.

1993 — Johannes G.M. Thewissen and Sayed Taseer Hussain discover fossils of the amphibious whale ancestor Ambulocetus in Pakistan.

1996 — Li Yumin discovers a fossil of the theropod dinosaur Sinosauropteryx showing evidence of feathers in the Liaoning province of China.

2004 — Tiktaalik, a transitional form between lobe-finned fish and tetrapods is discovered in Canada by Ted Daeschler, Neil H. Shubin, and Farish A. Jenkins Jr..

2009 — Fossils of Titanoboa, a giant snake, are unearthed in the coal mines of Cerrejón in La Guajira, Colombia, suggesting paleocene equatorial temperatures were higher than today. "

2016 — Tail fossils of a baby species of Coelurosaur, fully preserved in amber including soft tissue, are found in Myanmar by Lida Xing.

Valanginian

In the geologic timescale, the Valanginian is an age or stage of the Early or Lower Cretaceous. It spans between 139.8 ± 3.0 Ma and 132.9 ± 2.0 Ma (million years ago). The Valanginian stage succeeds the Berriasian stage of the Lower Cretaceous and precedes the Hauterivian stage of the Lower Cretaceous.

Valdoraptor

Valdoraptor (meaning "Wealden plunderer") is a genus of theropod dinosaur from the Early Cretaceous. Its fossils were found in England. It is known only from bones of the feet. The holotype, BMNH R2559 (incorrectly given by Owen as BMNH R2556), was found near Cuckfield in layers of the Tunbridge Wells Sand Formation dating from the late Valanginian. The specimen is damaged lacking parts of the upper and lower ends. It has a conserved length of 215 millimetres (8.5 in) and an estimated length of 240 millimetres (9.4 in). This genus is paleontologically significant for being the first ornithomimosaur specimen known from England and represents the earliest record of ornithomimosaurs.

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