Eotyrannus

Last updated

Eotyrannus
Temporal range: Barremian
~130  Ma
O
S
D
C
P
T
J
K
Pg
N
Skeletal elements of Eotyrannus.png
Known skeletal elements
Skeletal reconstruction of Eotyrannus.png
Skeletal diagram
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Theropoda
Clade: Tyrannoraptora
Superfamily: Tyrannosauroidea
Clade: Pantyrannosauria
Genus: Eotyrannus
Hutt et al., 2001
Species:
E. lengi
Binomial name
Eotyrannus lengi
Hutt et al., 2001
Synonyms

Eotyrannus (meaning "dawn tyrant") is a genus of tyrannosauroid theropod dinosaur hailing from the Early Cretaceous Wessex Formation beds, included in Wealden Group, located in the southwest coast of the Isle of Wight, United Kingdom. The remains (MIWG1997.550), consisting of assorted skull, axial skeleton and appendicular skeleton elements, from a juvenile or subadult, found in a plant debris clay bed, were described by Hutt et al. in early 2001. [1] The etymology of the generic name refers to the animal's classification as an early tyrannosaur or "tyrant lizard", while the specific name honors the discoverer of the fossil.

Contents

Discovery and naming

Map of the Isle of Wight; Eotyrannus was discovered at Grange Chine Geological context of Eotyrannus.png
Map of the Isle of Wight; Eotyrannus was discovered at Grange Chine

The exact location of the discovery of the holotype specimen has not been revealed due to its importance and the possibility of new material to be collected as the coastline recedes. From what is mentioned in the description, the specimen was found on the southwestern coast of the Isle of Wight, between Atherfield Point and Hanover Point. In 1995, local collector Gavin Leng brought a claw he had found along the coastline to Steve Hutt who worked at the old Museum of Isle of Wight Geology at Sandown. Gavin Leng revealed the location of where the claw was discovered, and over the next few weeks the site was carefully excavated, and the fossils removed in a hard matrix. Over the next few years the specimen was carefully researched with scientists from the University of Portsmouth, and with help from the Natural History Museum. [2]

Eventually in 2001, Eotyrannus was given its name along with its specific epithet in honour of Mr. Leng. [1] The material was described briefly in 2001 by Hutt et al. In July 2018 Darren Naish, a colleague of Hutt who helped produce the preliminary description, created a GoFundMe fundraiser in order to release a monograph of the specimen, which received well over its goal. [3] The monograph was eventually published in the journal PeerJ in 2022. [3]

Description

Size of the holotype compared to a human Eotyrannus.png
Size of the holotype compared to a human

A number of characters present in the holotypic specimen are unique to the genus. These include: The rostral end of dentary possessing a concave notch housing the most mesial alveolus and a dorsally-directed prong on the rostromesial margin of the notch, curving lateral furrows on the lateral surface of the dentary, a surangular with a hypertrophied gutter-like concavity near the rostrodorsal border, with the caudal end of the concavity containing foramina that perforate the body of the surangular, a low coronoid process on the surangular with a concave area located caudodorsally, and an ulna and radius with a tear-drop shaped cross-section at the mid-shaft. [3]

The holotypic specimen was disarticulated prior to fossilisation, with many elements of its skeleton scattered throughout the assemblage: none of the vertebral column is preserved in articulation and those vertebrae that are preserved consist of separated neural arches and centra, signifying that the holotype was an immature individual.

Due to the relative low-quality preservation of many of the skeletal elements, numerous pieces discovered have been difficult to identify: these include unidentified cranial elements, as well as an “ulna” which has since been recognised as the distal part of the tibia. Before the proper identification of this fragment, Eotyrannus was reconstructed with much longer tibiae, which influenced the early reconstructions of the animal.

Many of the characters also presented as unique to the genus in the diagnosis of Hutt et al. (2001) are in fact widespread throughout Tyrannosauroidea, for example the presence of 'serrated carinae on D-shaped premaxillary teeth' is far from unique to E. lengi. Furthermore, neither the presence of a laterally flattened rostral region to the maxilla nor a pronounced rim to the antorbital fossa are unique to the genus. [4]

Although the specimen itself measures up to 4.5 m (15 ft) in length, it doesn't represent the size of an adult; the specimen likely belongs to a subadult due to the lack of fusion regarding the neurocentral and sacral sutures. [3]

Classification

Life restoration Eotyrannus 2 NT.jpg
Life restoration

The discovery of Eotyrannus corroborates the notion that early tyrannosauroids were gracile with long forelimbs and three-fingered grasping hands, although the somewhat large size of the animal either means that early evolution for this clade was carried out at a large size or Eotyrannus developed large size independently. [5] The find of this animal in Europe puts in question to the purported Asian origin for these animals along with North American Stokesosaurus and European Aviatyrannis arguing for a more complex biogeography for tyrannosauroids. [6]

Below is a cladogram by Loewen et al. in 2013 that includes most tyrannosauroid genera. [6]

Tyrannosauroidea

A 2014 analysis found Eotyrannus to be a megaraptoran closely related to taxa like Megaraptor . [7]

Megaraptora

However, a 2017 study [8] stated that Eotyrannus was a stokesosaurid, while a 2022 analysis showed it to be a basal non-tyrannosaurid tyrannosauroid, with no close relationship to either stokesaurids or megaraptorans. [3]

The 2022 study by Naish and Cau by comparison, classifies Eotyrannus as an intermediate gracile tyrannosauroid more closely related to the true tyrannosaurids; more advanced than proceratosaurids, stokesosaurids and Yutyrannus, but without the characteristics of more advanced genera. Simultaneously, the description of Eotyrannus' placement in the family suggests that Megaraptora are tyrannosauroids as well, even though it was found that Eotyrannus is not a megaraptoran itself according to the authors' research, with Megaraptora representing a second wave of large-bodied tyrannosauroids that were important members of the world's ecosystem, one that may have originally slowed the evolutionary radiation of tyrannosaurids initially. [3]

Tyrannosauroidea

Palaeoenvironment

Restoration of Eotyrannus chasing Hypsilophodon, with other dinosaurs from the Wessex Formation in the background Wessex Formation dinosaurs.jpg
Restoration of Eotyrannus chasing Hypsilophodon , with other dinosaurs from the Wessex Formation in the background

The Wessex Formation, where Eotyrannus was found, was considered to have been warm and humid, similar to the present-day Mediterranean. However, there is evidence of a phase of increasing aridity during the late Barremian to early Aptian when Eotyrannus lived. In the Wessex Basin, sedimentological evidence, as well as fossils such as mud-cracks, suggests that the area experienced a warm, equable paleoclimate with a mean annual temperature of 20–25 °C with low seasonal rainfall. Watson and Alvin (1996) and Allen (1998) showed that the Wessex Formation flora was both fire and drought resistant and suggested that it was adapted to a seasonal climate with periods of marked aridity. Evidence for a wet season is provided by the frequent occurrence of fungal decay in plant material from the plant debris beds. [9]

The Wessex Formation possessed a wide array of fauna, including many other dinosaurs such as the carcharodontosaurian Neovenator , the compsognathid Aristosuchus ; the medium size spinosaurids Riparovenator and Ceratosuchops ; the basal neornithischian Hypsilophodon ; the ornithopods Iguanodon , Mantellisaurus , Brighstoneus , and Valdosaurus ; the sauropods Ornithopsis , Eucamerotus , and Iuticosaurus ; and the ankylosaur Polacanthus . There were many contemporary mammal species which Eotyrannus likely fed on, including the spalacotheriid Yaverlestes and the eobaatarid Eobaatar .[ citation needed ]

See also

Related Research Articles

The Isle of Wight is one of the richest dinosaur localities in Europe, with over 20 species of dinosaur having been recognised from the early Cretaceous Period, some of which were first identified on the island, as well as the contemporary non-dinosaurian species of crocodile, turtle and pterosaur.

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

Neovenator is a genus of carcharodontosaurian theropod dinosaur. It is known from several skeletons found in the Early Cretaceous (Hauterivian-Barremian) Wessex Formation on the south coast of the Isle of Wight, southern England. It is one of the best known theropod dinosaurs from the Early Cretaceous of Europe.

<i>Fukuiraptor</i> Megaraptoran theropod dinosaur genus from the Early Cretaceous epoch

Fukuiraptor was a medium-sized megaraptoran theropod dinosaur of the Early Cretaceous epoch that lived in what is now Japan. Fukuiraptor is known from the Kitadani Formation and possibly also the Sebayashi Formation.

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

Appalachiosaurus is a genus of basal eutyrannosaurian theropod dinosaur from the middle Campanian age of the Late Cretaceous period of what is now eastern North America. Like most theropods, it was a bipedal predator. Only a juvenile skeleton has been found, representing an animal approximately 6.5 metres (21 ft) long and weighing 623 kilograms (1,373 lb), which indicates an adult would have been significantly larger. It is the most completely known theropod from eastern North America.

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

Proceratosaurus is a genus of carnivorous theropod dinosaur from the Middle Jurassic (Bathonian) of England. It contains a single species. P. bradleyi, known from a mostly complete skull and lower jaws. Proceratosaurus was a small dinosaur, estimated to measure around 3 m (9.8 ft) in length. Its name refers to how it was originally thought to be an ancestor of Ceratosaurus, due to the partially preserved portion of the crest of Proceratosaurus superficially resembling the small crest of Ceratosaurus. Now, however, it is considered a coelurosaur, specifically a member of the family Proceratosauridae, and amongst the earliest known members of the clade Tyrannosauroidea.

<span class="mw-page-title-main">Darren Naish</span> British palaeontologist and science writer (born 1975)

Darren William Naish is a British vertebrate palaeontologist, author and science communicator.

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

Megaraptor is a genus of large theropod dinosaur that lived in the ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Initially thought to have been a giant dromaeosaur-like coelurosaur, it was classified as a neovenatorid allosauroid in previous phylogenies, but more recent phylogeny and discoveries of related megaraptoran genera has placed it as either a basal tyrannosauroid or a basal coelurosaur with some studies still considering it a neovenatorid.

<span class="mw-page-title-main">Tyrannosauroidea</span> Extinct superfamily of dinosaurs

Tyrannosauroidea is a superfamily of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic Tyrannosaurus. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe and Asia, with fragmentary remains possibly attributable to tyrannosaurs also known from South America and Australia.

Calamospondylus is a genus of theropod dinosaur. It lived during the Early Cretaceous and its fossils were found on the Isle of Wight in southern England. The type species is C. oweni.

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

Aerosteon is a genus of megaraptoran dinosaur from the Late Cretaceous period of Argentina. Its remains were discovered in 1996 in the Anacleto Formation, which is from the late Campanian. The type and only known species is A. riocoloradensis. Its specific name indicates that its remains were found 1 km north of the Río Colorado, in Mendoza Province, Argentina.

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

Xiongguanlong is an extinct genus of tyrannosauroid theropod from the Early Cretaceous period of what is now China. The type and only species is X. baimoensis. The generic name comes from Jiayuguan City and the Mandarin word "long" which means dragon. The specific epithet, "baimoensis" is a latinization of the Mandarin word for "white ghost" in reference to one of the geological features of the type locality.

<span class="mw-page-title-main">Neovenatoridae</span> Extinct family of dinosaurs

Neovenatoridae is a proposed clade of carcharodontosaurian dinosaurs uniting some primitive members of the group such as Neovenator with the Megaraptora, a group of theropods with controversial affinities. Other studies recover megaraptorans as basal coelurosaurs unrelated to carcharodontosaurs. Other theropods with uncertain affinities such as Gualicho, Chilantaisaurus and Deltadromeus are also sometimes included.

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

Sinotyrannus is a genus of large basal tyrannosauroid dinosaur, known from a single incomplete fossil specimen including a partial skull, from the Early Cretaceous Jiufotang Formation of Liaoning, China. Specifically, it is a member of the Proceratosauridae, a family that originated in the Jurassic whose members are known from Europe and Asia. Though it is not significantly younger than primitive tyrannosauroids such as Dilong, it is similar in size to later forms such as Tyrannosaurus. It was much larger than contemporary tyrannosauroids, reaching a total estimated length of 9–10 m (30–33 ft), and was the largest known theropod from the Jiufotang Formation. The type species, S. kazuoensis, was described by Ji et al. in 2009.

<span class="mw-page-title-main">Megaraptora</span> Extinct clade of dinosaurs

Megaraptora is a clade of carnivorous theropod dinosaurs. Its derived members, the Megaraptoridae are noted for their large hand claws and powerfully-built forelimbs, which are usually reduced in size in other large theropods.

<span class="mw-page-title-main">Proceratosauridae</span> Extinct family of dinosaurs

Proceratosauridae is a family or clade of tyrannosauroid theropod dinosaurs from the Middle Jurassic to the Early Cretaceous.

<i>Yutyrannus</i> Genus of proceratosaurid dinosaur from the Early Cretaceous period

Yutyrannus is a genus of proceratosaurid tyrannosauroid dinosaur which contains a single known species, Yutyrannus huali. This species lived during the early Cretaceous period in what is now northeastern China. Three fossils of Yutyrannus huali —all found in the rock beds of Liaoning Province— are currently the largest-known carnivorous dinosaur specimens that preserve direct evidence of feathers.

<i>Siats</i> Extinct genus of theropod dinosaur

Siats (/see-ats/) is an extinct genus of large theropod dinosaur known from the Late Cretaceous Cedar Mountain Formation of Utah, United States. It contains a single species, Siats meekerorum. It was initially classified as a megaraptoran, a clade of large theropods with very controversial relationships. Siats may be a neovenatorid allosauroid, a coelurosaur of uncertain phylogenetic position, or a tyrannosauroid.

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

Murusraptor is a genus of carnivorous megaraptoran theropod dinosaur from the Sierra Barrosa Formation, part of the Neuquén Group of Patagonia, in Argentina, South America. It is known from a single specimen that consists of a partial skull, ribs, partial pelvis, leg and other assorted skeletal elements.

<i>Ceratosuchops</i> Genus of baryonychine spinosaur from the Early Cretaceous

Ceratosuchops is a genus of spinosaurid from the Early Cretaceous (Barremian) of Britain.

<i>Riparovenator</i> Genus of baryonychine spinosaur from the Early Cretaceous

Riparovenator is a genus of baryonychine spinosaurid dinosaur from the Early Cretaceous (Barremian) period of Britain. The genus contains a single species, Riparovenator milnerae.

References

  1. 1 2 Hutt, S.; Naish, D.; Martill, D.M.; Barker, M.J.; Newbery, P. (2001). "A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Cretaceous) of southern England" (PDF). Cretaceous Research. 22: 227–242. doi:10.1006/cres.2001.0252.
  2. Price, T. (2018, November 26). Eotyrannus lengi. Retrieved from http://www.dinosaurisle.com/eotyrannus.aspx
  3. 1 2 3 4 5 6 Naish, D.; Cau, A. (July 2022). "The osteology and affinities of Eotyrannus lengi, a tyrannosauroid theropod from the Wealden Supergroup of southern England". PeerJ. 10: e12727. doi: 10.7717/peerj.12727 . PMC   9271276 . PMID   35821895.
  4. Naish, D., (2006). The Osteology and Affinities of Eotyrannus lengi and Other Lower Cretaceous Theropod Dinosaurs From England. Unpublished Ph.D. Thesis, University of Portsmouth.
  5. Holtz, T. R. Jr. (1994). "The phylogenetic position of the Tyrannosauridae: implications for theropod systematics". Journal of Paleontology. 68 (5): 1100–1117. doi:10.1017/S0022336000026706. S2CID   129684676.
  6. 1 2 Loewen, M.A.; Irmis, R.B.; Sertich, J.J.W.; Currie, P. J.; Sampson, S. D. (2013). Evans, David C (ed.). "Tyrant dinosaur evolution tracks the rise and fall of Late Cretaceous oceans". PLoS ONE . 8 (11): e79420. Bibcode:2013PLoSO...879420L. doi: 10.1371/journal.pone.0079420 . PMC   3819173 . PMID   24223179.
  7. Juan D. Porfiri; Fernando E. Novas; Jorge O. Calvo; Federico L. Agnolín; Martín D. Ezcurra; Ignacio A. Cerda (2014). "Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation". Cretaceous Research. 51: 35–55. doi:10.1016/j.cretres.2014.04.007. hdl: 11336/12129 .
  8. Carr, Thomas D.; Varricchio, David J.; Sedlmayr, Jayc C.; Roberts, Eric M.; Moore, Jason R. (2017-03-30). "A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system". Scientific Reports. 7 (1): 44942. Bibcode:2017NatSR...744942C. doi:10.1038/srep44942. ISSN   2045-2322. PMC   5372470 . PMID   28358353.
  9. Sweetman, Steven & N. Insole, Allan. (2010). The plant debris beds of the Early Cretaceous (Barremian) Wessex Formation of the Isle of Wight, southern England: Their genesis and palaeontological significance. Palaeogeography, Palaeoclimatology, Palaeoecology. 292. 409-424. 10.1016/j.palaeo.2010.03.055.