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Ceratosaurs are members of the clade Ceratosauria, a group of
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s defined as all
theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
s sharing a more recent common ancestor with ''
Ceratosaurus ''Ceratosaurus'' (from Greek κέρας/κέρατος, ' meaning "horn" and σαῦρος ' meaning "lizard") was a carnivorous theropod dinosaur in the Late Jurassic period ( Kimmeridgian to Tithonian). The genus was first described in 1 ...
'' than with birds. The oldest known ceratosaur, '' Saltriovenator'', dates to the earliest part of the Jurassic, around 199 million years ago. According to the majority of the latest research, Ceratosauria includes three major clades:
Ceratosauridae Ceratosauridae is an extinct family of theropod dinosaurs belonging to the infraorder Ceratosauria. The family's type genus, ''Ceratosaurus'', was first found in Jurassic rocks from North America. Ceratosauridae is made up of the genera ''Cera ...
,
Noasauridae Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed abelisaurids, although most noasaurids had much more traditional body types generally similar to other th ...
, and
Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
, found primarily (though not exclusively) in the Southern Hemisphere. Originally, Ceratosauria included the above dinosaurs plus the Late Triassic to Early Jurassic
Coelophysoidea Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the ...
and Dilophosauridae, implying a much earlier divergence of ceratosaurs from other theropods. However, most recent studies have shown that coelophysoids and dilophosaurids do not form a natural group with other ceratosaurs, and are excluded from this group. Ceratosauria derives its names from the type species, ''
Ceratosaurus nasicornis ''Ceratosaurus'' (from Greek κέρας/κέρατος, ' meaning "horn" and σαῦρος ' meaning "lizard") was a carnivorous theropod dinosaur in the Late Jurassic period (Kimmeridgian to Tithonian). The genus was first described in 1884 ...
'', described by
O.C. Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
in 1884. A moderately large predator from the Late Jurassic, ''Ceratosaurus nasicornis'', was the first ceratosaur to be discovered. Ceratosaurs are generally moderately large in size, with some exceptions like the larger ''
Carnotaurus ''Carnotaurus'' (; ) is a genus of theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 71 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a single well-p ...
'' and the significantly smaller noasaurs. The major defining characteristics of Ceratosauria include a robust skull with increased ornamentation or height and a shortening of the arms. Both of these characteristics are generally accentuated in later members of the group, such as the abelisaurs, whereas more basal species such as ''C. nasicornis'' appear more similar to other basal
theropods Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally ca ...
. The highly fragmented nature of the ceratosaur fossil record means that the characteristics, relationships, and early history of Ceratosauria remain mysterious and highly debated.


Phylogeny


Historical phylogeny

Ceratosauria was first described by
O.C. Marsh Othniel Charles Marsh (October 29, 1831 – March 18, 1899) was an American professor of Paleontology in Yale College and President of the National Academy of Sciences. He was one of the preeminent scientists in the field of paleontology. Among h ...
in the ''
American Journal of Science The ''American Journal of Science'' (''AJS'') is the United States of America's longest-running scientific journal, having been published continuously since its conception in 1818 by Professor Benjamin Silliman, who edited and financed it himsel ...
'' in 1884. Writing about the newly discovered '' C. nasicornis'', he noted the similarities between the firmly united metatarsals of ''C. nasicornis'' and those of ''
Archaeopteryx ''Archaeopteryx'' (; ), sometimes referred to by its German name, "" ( ''Primeval Bird''), is a genus of bird-like dinosaurs. The name derives from the ancient Greek (''archaīos''), meaning "ancient", and (''ptéryx''), meaning "feather" ...
''. Since ''C. nasicornis'' was the only other dinosaur discovered at the time to share this trait, Marsh concluded that Ceratosauria must be placed very near ''Archaeopteryx'' and its related groups. However, the idea of the Ceratosauria was soon contested by Marsh's rival,
Edward Drinker Cope Edward Drinker Cope (July 28, 1840 – April 12, 1897) was an American zoologist, paleontologist, comparative anatomist, herpetologist, and ichthyologist. Born to a wealthy Quaker family, Cope distinguished himself as a child prodigy interes ...
. Cope argued that the taxon was invalid. The idea of the Ceratosauria would regain some support more than thirty years later when Gilmore argued in its favor in 1920. Despite Gilmore's support, few species were added to the group following World War I, and little emphasis was placed on it. In fact, the scientific community's most common interaction with Ceratosauria throughout much of the 20th century was the disputation of its existence, performed by the likes of
Romer A Reference Card or "Romer" is a device for increasing the accuracy when reading a grid reference from a map. Made from transparent plastic, paper or other materials, they are also found on most baseplate compasses. Essentially, it is a speciall ...
, Lapparent, Lavocat, Colbert, and Charig amongst others. Ceratosauria's fortune changed in 1986 when
Jacques Gauthier Jacques Armand Gauthier (born June 7, 1948 in New York City) is an American vertebrate paleontologist, comparative morphologist, and systematist, and one of the founders of the use of cladistics in biology. Life and career Gauthier is the so ...
, in an attempt to clarify the evolution of birds, grouped the majority of theropods into either Ceratosauria or
Tetanurae Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans (including birds). Tetanurans ar ...
. In Ceratosauria, he placed the ceratosaurs and
coelophysoids Coelophysoidea were common dinosaurs of the Late Triassic and Early Jurassic periods. They were widespread geographically, probably living on all continents. Coelophysoids were all slender, carnivorous forms with a superficial similarity to the ...
. Gauthier's paper brought Ceratosauria's use back in vogue, and by the early 1990s,
Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
had also been included under Ceratosauria. The triumvirate model of ceratosaurs, coelophysoids, and abelisaurids would go unchallenged until the early 2000s. Beginning at the turn of the millennium, a large number of paleontologists began excluding coelophysoids from Ceratosauria. This view is now widely held thanks to several similarities between Ceratosauria and Tetanurae not found in coelophysoids.


Current phylogeny

Most paleontologists have postulated that Ceratosauria split off from other theropods in the Late Triassic or earliest Jurassic. Despite this, no ceratosaurs have been discovered prior to the Early Jurassic, and even in the Middle Jurassic, species are sparse. Many scientists, such as Carrano and Sampson, have postulated the lack of specimens is due to a poor fossil record, rather than an indictment on the abundance of ceratosaurs at the time. A similarly large gap of specimens exist in the lower Cretaceous, particularly for
Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
. Several recent discoveries of possible ceratosaurs have begun reshaping the phylogeny of Ceratosauria by filling in some of these gaps. Specifically, this has allowed paleontologists to begin altering the sub-groups inside Ceratosauria, in an attempt to find their most basal members. Currently, most paleontologists agree that Ceratosauria divides into two sub groups,
Ceratosauridae Ceratosauridae is an extinct family of theropod dinosaurs belonging to the infraorder Ceratosauria. The family's type genus, ''Ceratosaurus'', was first found in Jurassic rocks from North America. Ceratosauridae is made up of the genera ''Cera ...
and Abelisauroidea, with some variance as to which taxa are placed into basal polytomy. Abelisauroidea is further divided into the
Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
and
Noasauridae Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed abelisaurids, although most noasaurids had much more traditional body types generally similar to other th ...
, with Abelisauridae, including
Carnotaurinae Carnotaurinae is a subfamily of the theropod dinosaur family Abelisauridae. It includes the dinosaurs '' Aucasaurus'' (from Argentina), '' Carnotaurus'' (from Argentina). The group was first proposed by American paleontologist Paul Sereno in 19 ...
. Recently, Rauhut and Carrano have placed Elaphrosaurinae inside Noasauridae while simultaneously moving the previous noasaurs into Noasaurinae. Into their new Noasauridae, they have uniquely included '' Deltadromeus'' and ''
Limusaurus ''Limusaurus'' is a genus of theropod dinosaur that lived in what is now China during the Late Jurassic, around 161 to 157 million years ago. The type and only species ''Limusaurus inextricabilis'' was described in 2009 from specimens ...
''. The oldest known ceratosaur currently described is '' Saltriovenator zanellai'' which is dated to the Early
Sinemurian In the geologic timescale, the Sinemurian is an age and stage in the Early or Lower Jurassic Epoch or Series. It spans the time between 199.3 ± 2 Ma and 190.8 ± 1.5 Ma (million years ago). The Sinemurian is preceded by the Hettangian and ...
, 199-197 Ma. The origin of Ceratosauria could have been in Northern Pangea where ''Saltriovenator'', its close relative ''
Berberosaurus ''Berberosaurus'' (meaning " Berber lizard", in reference to the Berbers of Morocco) is a genus of neotheropod dinosaur, possibly a ceratosaur, from the Early Toarcian-age (Lower Jurassic) Azilal Formation found in the High Atlas of Toundoute, O ...
,'' and ''
Carmelopodus ''Carmelopodus'' is an ichnogenus of dinosaur footprint. They are suggested to belong to basal ceratosaurs, due to their similarities with abelisaurid footprints. In 2016, a large footprint from the Early Jurassic of Morocco Morocco ( ...
'' footprints have been found. The following
cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to ...
follows an analysis by Diego Pol and Oliver W. M. Rauhut, 2012. A different conclusion was reached in a 2017 paper on ''
Limusaurus ''Limusaurus'' is a genus of theropod dinosaur that lived in what is now China during the Late Jurassic, around 161 to 157 million years ago. The type and only species ''Limusaurus inextricabilis'' was described in 2009 from specimens ...
'' ontogeny. Unlike other analyses,
Noasauridae Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed abelisaurids, although most noasaurids had much more traditional body types generally similar to other th ...
was placed more basal than ''
Ceratosaurus ''Ceratosaurus'' (from Greek κέρας/κέρατος, ' meaning "horn" and σαῦρος ' meaning "lizard") was a carnivorous theropod dinosaur in the Late Jurassic period ( Kimmeridgian to Tithonian). The genus was first described in 1 ...
'', with the latter being within
Abelisauridae Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are fou ...
by definition. This was later expanded on in a 2018 paper on ceratosaur paleobiology, which named a new clade Etrigansauria, which contained the families Abelisauridae and Ceratosauridae. The following cladogram is a consensus tree of the latest phylogenies shown in the paper.


Paleobiology


Anatomy

Some of the defining characteristics of Ceratosauria include an increase in height and ornamentation of the skull, as well as a shortening of the forelimbs. Likewise, ceratosaurs fused their ilium, ischium, and pubis together, as well as the astralagus and calcaneum. For less derived members of the group, such as '' C. nasicornis'', traits such as raising of the skull and shortening of the forelimbs were not as noticeable. The skull of ''C. nasicornis'' was rather similar to the basal
theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
mold, with a distinguishing nasal crest to go along with lacrimal crests similar to the contemporary ''
Allosaurus ''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch ( Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alludin ...
''. ''C. nasicornis'' had larger teeth than ''Allosaurus'', and some paleontologists postulate that it would have had a difficult time attacking larger prey. Abelisaurids, however, carried many of these defining traits to their extremes. Most abelisaurids had largely shortened forelimbs, with ''Carnotaurus'' having shrunk them further than any large theropod. After analyzing the features of the newly discovered ''Rugops primus'', Paul Sereno has postulated that many of these abelisaurid features may lend themselves to scavenging. Despite the huge reduction in size, no taxa in Ceratosauria ever lost a digit or any critical elements of the forelimb. Some joint variation has also been observed in Ceratosauria, and it has been postulated that they may have had better shoulder mobility than other large theropods.


Geography

Ceratosaurs appeared to have had a global population that diverged by the early Jurassic. However, they appear to have largely disappeared from
Laurasia Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pa ...
in the
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...
, with those few specimens that have been discovered having been possibly reintroduced from
Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...
. No confirmed specimens of ceratosaurs in North America during the Cretaceous have been found. Abelisaurids in particular had great success in
Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final sta ...
, particularly in the Cretaceous. Some Gondwanan and Laurasian specimens have recently been found and dated to Late Jurassic, and possibly even the Middle Jurassic, greatly extending the abelisaurid timeline. Some paleontologists have postulated that a large desert may have kept abelisaurids locked in southern Gondwana until the late Jurassic. Whether correlation or causation, it has been largely observed that late Cretaceous ceratosaurs were found less in areas dominated by basal
tetanurans Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans (including birds). Tetanurans ar ...
(Africa) or coelurosaurs (North America and Asia). The below phylogeny follows a simplified cladogram of Hendrickx et al. (2015), limited to Ceratosauria.


Diet

Ceratosaurs were theropods and thus carnivores, with one exception, ''
Limusaurus inextricabilis ''Limusaurus'' is a genus of theropod dinosaur that lived in what is now China during the Late Jurassic, around 161 to 157 million years ago. The type and only species ''Limusaurus inextricabilis'' was described in 2009 from specim ...
'' was an herbivore with a toothless beak. ''
Ceratosaurus ''Ceratosaurus'' (from Greek κέρας/κέρατος, ' meaning "horn" and σαῦρος ' meaning "lizard") was a carnivorous theropod dinosaur in the Late Jurassic period ( Kimmeridgian to Tithonian). The genus was first described in 1 ...
'' has been argued to have eaten a large amount of fish and other aquatic creatures, though this has been disputed by many paleontologists. Tooth marks on large animals such as ''
Allosaurus ''Allosaurus'' () is a genus of large carnosaurian theropod dinosaur that lived 155 to 145 million years ago during the Late Jurassic epoch ( Kimmeridgian to late Tithonian). The name "''Allosaurus''" means "different lizard" alludin ...
'' indicate that ''Ceratosaurus'' likely utilized scavenging often. The interesting jaws of the abelisaurids have drawn mixed dietary predictions. One study on ''
Carnotaurus ''Carnotaurus'' (; ) is a genus of theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 71 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a single well-p ...
'' found that its bite, thanks to its shortened skull, was suited for hunting small prey, thanks to a quick, but relatively weak bite. On the other hand, other groups of paleontologists have found that the bite of ''Carnotaurus'' was relatively powerful, and more adept at hunting and wounding large prey. Others have postulated its skull was built for scavenging. The debate over the eating habits of ceratosaurs is quite active, particularly recently with the increase in abelisaur discoveries.


See also

*
Timeline of ceratosaur research This timeline of ceratosaur research is a chronological listing of events in the history of paleontology focused on the ceratosaurs, a group of relatively primitive, often horned, predatory theropod dinosaurs that became the apex predators of ...


References


External links

{{Portal bar, Dinosaurs, Paleontology, Cretaceous Cretaceous dinosaurs Jurassic dinosaurs Pliensbachian first appearances Maastrichtian extinctions Taxa named by Othniel Charles Marsh