Eotyrannus
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''Eotyrannus'' (meaning "dawn tyrant") is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of tyrannosauroid
theropod Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
hailing from the
Early Cretaceous The Early Cretaceous (geochronology, geochronological name) or the Lower Cretaceous (chronostratigraphy, chronostratigraphic name) is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 143.1 ...
Wessex Formation The Wessex Formation is a fossil-rich England, English geological formation that dates from the Berriasian to Barremian Stage (stratigraphy), stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Form ...
beds, included in
Wealden Group The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group (stratigraphy), group (a sequence of rock strata) in the lithostratigraphy of southern England. The Wealden group consists of wiktionary:paralic, paralic to c ...
, located in the southwest coast of the
Isle of Wight The Isle of Wight (Help:IPA/English, /waɪt/ Help:Pronunciation respelling key, ''WYTE'') is an island off the south coast of England which, together with its surrounding uninhabited islets and Skerry, skerries, is also a ceremonial county. T ...
,
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...
. 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. 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.


Discovery and naming

The exact location of the discovery of the
holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...
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 Sandown is a seaside resort and civil parishes in England, civil parish on the south-east coast of the Isle of Wight, England. The neighbouring resort of Shanklin and the settlement of Lake, Isle of Wight, Lake are sited just to the south of t ...
. 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 The University of Portsmouth (UoP) is a public university in Portsmouth, England. Comprising five Faculty (division), faculties, the university offers a wide range of academic disciplines. in 2022, with around 28,280 students enrolled in Unde ...
, and with help from the
Natural History Museum A natural history museum or museum of natural history is a scientific institution with natural history scientific collection, collections that include current and historical records of animals, plants, Fungus, fungi, ecosystems, geology, paleo ...
. Eventually in 2001, ''Eotyrannus'' was given its name along with its specific epithet in honour of Mr. Leng. The material was described briefly in 2001 by Hutt et al. In July 2018
Darren Naish Darren William Naish (born 26 September 1975) is a British vertebrate palaeontologist, author and science communicator. As a researcher, he is best known for his work describing and reevaluating dinosaurs and other Mesozoic reptiles, including ...
, a colleague of Hutt who helped produce the preliminary description, created a
GoFundMe GoFundMe is an American for-profit crowdfunding platform that allows people to raise money for events ranging from life events such as celebrations and graduations to challenging circumstances like accidents and illnesses. From 2010 to the ...
fundraiser in order to release a monograph of the specimen, which received well over its goal. The monograph was eventually published in the journal ''
PeerJ ''PeerJ'' is an open access peer-reviewed scientific mega journal covering research in the biological and medical sciences. It officially launched in June 2012, started accepting submissions on December 3, 2012, and published its first articles ...
'' in 2022.


Description

A number of characters present in the holotypic specimen are unique to the genus. These include: The
rostral Rostral may refer to: Anatomy * Rostral (anatomical term), situated toward the oral or nasal region * Rostral bone, in ceratopsian dinosaurs * Rostral organ, of certain fish * Rostral scale The rostral scale, or rostral, in snakes and other sca ...
end of dentary possessing a concave notch housing the most
mesial This is a list of definitions of commonly used terms of location and direction in dentistry. This set of terms provides orientation within the oral cavity, much as anatomical terms of location provide orientation throughout the body. Terms ...
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 In anatomy and osteology, a foramen (; : foramina, or foramens ; ) is an opening or enclosed gap within the dense connective tissue (bones and deep fasciae) of extant and extinct amniote animals, typically to allow passage of nerves, arter ...
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. 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 Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. Thi ...
elements, as well as an “ulna” which has since been recognised as the
distal Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...
part of the
tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
. 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 In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...
nor a pronounced rim to the antorbital fossa are unique to the genus. Although the specimen itself measures up to 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.


Classification

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. The find of this animal in Europe puts in question to the purported Asian origin for these animals along with
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
n ''
Stokesosaurus ''Stokesosaurus'' (meaning "Stokes' lizard") is a genus of small (around in length), carnivorous early tyrannosauroid theropod dinosaurs from the late Jurassic period of Utah, United States. History From 1960 onwards Utah geologist William ...
'' and
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
an '' Aviatyrannis'' arguing for a more complex biogeography for tyrannosauroids. Below is a cladogram by Loewen ''et al.'' in 2013 that includes most tyrannosauroid genera. A 2014 analysis found ''Eotyrannus'' to be a
megaraptora 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. Although undoubt ...
n closely related to taxa like ''
Megaraptor ''Megaraptor'' () is a genus of large Theropoda, theropod dinosaur that lived during the Turonian and Coniacian ages of the Late Cretaceous. Its fossils have been discovered in the Patagonian Portezuelo Formation of Argentina, South America. Th ...
''. The 2022 osteology 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. In 2024, Andrea Cau recovered ''Eotyrannus'' as a sister taxon of Proceratosauridae, distant in relation from
Megaraptora 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. Although undoubt ...
.


Palaeoenvironment

The
Wessex Formation The Wessex Formation is a fossil-rich England, English geological formation that dates from the Berriasian to Barremian Stage (stratigraphy), stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Form ...
, where ''Eotyrannus'' was found, was considered to have been warm and humid, similar to the present-day
Mediterranean The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern ...
. However, there is evidence of a phase of increasing aridity during the late
Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 125.77 Ma (million years ago) and 121.4 ± 1.0 Ma (Historically, this stage was placed at 129.4 million to approximately 125 million years ago) It is a ...
to early
Aptian The Aptian is an age (geology), age in the geologic timescale or a stage (stratigraphy), stage in the stratigraphic column. It is a subdivision of the Early Cretaceous, Early or Lower Cretaceous epoch (geology), Epoch or series (stratigraphy), S ...
when ''Eotyrannus'' lived. In the
Wessex Basin The Wessex Basin is a petroleum-bearing geological area located along the southern coast of England and extending into the English Channel. The onshore part of the basin covers approximately 20,000 km2 and the area that encompasses the Englis ...
, sedimentological evidence, as well as fossils such as mud-cracks, suggests that the area experienced a warm, equable
paleoclimate Paleoclimatology ( British spelling, palaeoclimatology) is the scientific study of climates predating the invention of meteorological instruments, when no direct measurement data were available. As instrumental records only span a tiny part of ...
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 The Wessex Formation is a fossil-rich England, English geological formation that dates from the Berriasian to Barremian Stage (stratigraphy), stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Form ...
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.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. The
Wessex Formation The Wessex Formation is a fossil-rich England, English geological formation that dates from the Berriasian to Barremian Stage (stratigraphy), stages of the Early Cretaceous. It forms part of the Wealden Group and underlies the younger Vectis Form ...
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 Neornithischia ("new ornithischians") is a clade of the dinosaur order Ornithischia. It is the sister group of the Thyreophora within the clade Genasauria. Neornithischians are united by having a thicker layer of asymmetrical enamel on the insi ...
''
Hypsilophodon ''Hypsilophodon'' (; meaning "high-crested tooth") is a neornithischian dinosaur genus from the Early Cretaceous period of England. It has traditionally been considered an early member of the group Ornithopoda, but recent research has put this ...
''; the ornithopods ''
Iguanodon ''Iguanodon'' ( ; meaning 'iguana-tooth'), named in 1825, is a genus of iguanodontian dinosaur. While many species found worldwide have been classified in the genus ''Iguanodon'', dating from the Late Jurassic to Early Cretaceous, Taxonomy (bi ...
'', ''
Mantellisaurus ''Mantellisaurus'' is a genus of iguanodontian dinosaur that lived in the Barremian and early Aptian ages of the Early Cretaceous Period of Europe. Its remains are known from Belgium (Bernissart), England, Spain and Germany. The type species, ty ...
'', ''
Brighstoneus ''Brighstoneus'' (after Brighstone, a village on the Isle of Wight) is a genus of Ankylopollexia, hadrosauriform dinosaur from the Early Cretaceous Wessex Formation of the Isle of Wight, Isle of Wight, England. The genus contains a single specie ...
'', and ''
Valdosaurus ''Valdosaurus'' ("Weald Lizard") is a genus of bipedal herbivorous iguanodont ornithopod dinosaur found on the Isle of Wight and elsewhere in England, and possibly also Spain and Romania. It lived during the Early Cretaceous. Discovery and namin ...
''; the sauropods ''
Ornithopsis ''Ornithopsis'' (meaning "bird-likeness") is a genus of sauropod dinosaur, from the Early Cretaceous of England and possibly Germany. The type species, which is the only species seen as valid today, is ''O. hulkei,'' which is only known from frag ...
'', ''
Eucamerotus ''Eucamerotus'' (meaning "well-chambered", in reference to the hollows of the vertebrae) was a genus of sauropod dinosaur from the Barremian-age Lower Cretaceous Wessex Formation ( Wealden) of the Isle of Wight, England. History and taxonomy J ...
'', and '' Iuticosaurus''; and the
ankylosaur Ankylosauria is a group of herbivorous dinosaurs of the clade 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 l ...
''
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 ...
''. There were many contemporary mammal species which ''Eotyrannus'' likely fed on, including the
spalacotheriid Spalacotheriidae is a family of extinct mammals belonging to the paraphyletic group 'Symmetrodonta'. They lasted from the Early Cretaceous to the Campanian in North America, Europe, Asia and North Africa. Spalacotheriids are characterised by hav ...
''
Yaverlestes ''Yaverlestes gassoni'' is an extinct mammal which dates to the early Cretaceous period, 130 million years ago. It is part of the Wessex Formation from the Isle of Wight, England. The holotype A holotype (Latin: ''holotypus'') is a single ...
'' and the eobaatarid '' Eobaatar''.


See also

*
Timeline of tyrannosaur research This timeline of tyrannosaur research is a chronological listing of events in the history of paleontology focused on the tyrannosaurs, a group of predatory theropod dinosaurs that began as small, long-armed bird-like creatures with elaborate cr ...


References

{{Portal bar, Dinosaurs Tyrannosauroidea Dinosaur genera Barremian dinosaurs Wessex Formation Fossil taxa described in 2001 Taxa named by Darren Naish Dinosaurs of the United Kingdom