genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

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 ...

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 ...

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

Niger ) , official_languages = , languages_type = National languagesbaryonychine member of the Spinosauridae, a group of large

bipedal Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...

s with well-built forelimbs and elongated, crocodile-like skulls. The

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

''Cristatusaurus lapparenti'' was named in

1998 1998 was designated as the ''International Year of the Ocean''. Events January * January 6 – The ''Lunar Prospector'' spacecraft is launched into orbit around the Moon, and later finds evidence for frozen water, in soil in permanently s ...

by scientists Philippe Taquet and Dale Russell, on the basis of jaw bones and some

vertebra The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characterist ...

e. Two claw

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s were also later assigned to ''Cristatusaurus''. The animal's generic name, which means "crested reptile", alludes to a

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...

on top of its snout; while the

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

is in honor of the French

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

Albert-Félix de Lapparent. ''Cristatusaurus'' is known from the

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± ...

to

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

Elrhaz Formation, where it would have coexisted with

sauropod Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their ...

and

iguanodontia Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', '' Dryosaurus'', '' Iguanodon'', '' Tenontosaurus'', and the hadrosaurids or "duck- ...

n dinosaurs, other theropods, and various crocodylomorphs. Originally proposed to be an indeterminate species of ''

Baryonyx ''Baryonyx'' () is a genus of theropod dinosaur which lived in the Barremian stage of the Early Cretaceous period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Smokejack Clay Pit, of Surrey, England, in ...

'', the identity of ''Cristatusaurus'' has been subject to debate, in part due to the fragmentary nature of its fossils. Some argue that it is probably the same dinosaur as ''

Suchomimus ''Suchomimus'' (meaning "crocodile mimic") is a genus of spinosaurid dinosaur that lived between 125 and 112 million years ago in what is now Niger, during the Aptian to early Albian stages of the Early Cretaceous period. It was named an ...

,'' which has also been found in Niger, in the same sediment layers. In that case the genus ''Cristatusaurus'' would have priority, since it was named two months earlier. Others have concluded, however, that ''Cristatusaurus'' is a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'', considering it indistinguishable from both ''Suchomimus'' and ''Baryonyx''. Some distinctions between the fossils of ''Cristatusaurus'' and ''Suchomimus'' have been pointed out, but it is uncertain whether these differences separate the two genera or if they are due to

ontogeny Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the stu ...

(changes in an organism during growth). A recent study differentiated ''Cristatusaurus'' from ''Suchomimus'' and assigned as a valid spinosaurid genus, placed the theropod just outside Baryonychinae.

History of research

The first

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

s of ''Cristatusaurus'' were found in 1973 by French

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

Philippe Taquet at Gadoufaoua, a locality within the Elrhaz Formation in

Niger ) , official_languages = , languages_type = National languagesholotype specimen, cataloged under the number

MNHN The French National Museum of Natural History, known in French as the ' (abbreviation MNHN), is the national natural history museum of France and a ' of higher education part of Sorbonne Universities. The main museum, with four galleries, is loca ...

GDF 366, consists of two

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has ...

e (frontmost snout bones), a partial right (main upper jaw bone), and a fragment from the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bon ...

. Several

paratype In zoology and botany, a paratype is a specimen of an organism that helps define what the scientific name of a species and other taxon actually represents, but it is not the holotype (and in botany is also neither an isotype nor a syntype). O ...

s have been assigned: MNHN GDF 365, a snout of two

articulated An articulated vehicle is a vehicle which has a permanent or semi-permanent pivot joint in its construction, allowing it to turn more sharply. There are many kinds, from heavy equipment to buses, trams and trains. Steam locomotives were sometim ...

premaxillae; as well as MNHN GDF 357, 358, 359 and 361, four dorsal vertebrae. Two thumb claws from separate specimens were also subsequently attributed to ''Cristatusaurus''. In 1984, the premaxilla specimens MNHN GDF 365 and 366 were first described in detail by Taquet, where he referred them to an unnamed new

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 ...

within the

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Spinosauridae, because of shared characteristics with the holotype dentary of ''Spinosaurus aegyptiacus''. At the time Taquet believed these specimens belonged to the creature's lower jaw, since no theropod was known then with over five teeth in the premaxilla, while ''Cristatusaurus'' had seven. This was later proven incorrect in 1996 by Brazilian paleontologists

Alexander Kellner Alexander Wilhelm Armin Kellner (born September 26, 1961) is a Brazilian geologist and paleontologist who is a leading expert in the field of studying pterosaurs. His research has focused mainly on fossil reptiles from the Cretaceous Period, i ...

and Diogenes Campos, in light of the discoveries of other spinosaurids preserving upper jaw tips with over five teeth. Cristatusaurus claw

In a

1986 The year 1986 was designated as the International Year of Peace by the United Nations. Events January * January 1 **Aruba gains increased autonomy from the Netherlands by separating from the Netherlands Antilles. **Spain and Portugal enter ...

publication, British paleontologists

Alan Charig Alan Jack Charig (1 July 1927 – 15 July 1997) was an English palaeontologist and writer who popularised his subject on television and in books at the start of the wave of interest in dinosaurs in the 1970s. Charig was, though, first and fo ...

and

Angela Milner Angela Cheryl Milner (3 October 1947 – 13 August 2021) was a British Paleontology, paleontologist who, in 1986 alongside Alan Charig, described the dinosaur ''Baryonyx''. Early life Milner was born Angela Girven in Gosforth, daughter of ...

considered Taquet's jaw elements nearly indistinguishable from those of the spinosaurid '' Baryonyx walkeri''; which they were describing on the basis of a partial skeleton from the

Barremian The Barremian is an age in the geologic timescale (or a chronostratigraphic stage) between 129.4 ± 1.5 Ma ( million years ago) and 121.4 ± 1.0 Ma). It is a subdivision of the Early Cretaceous Epoch (or Lower Cretaceous Series). It is pre ...

of the

Weald Clay Formation Weald Clay or the Weald Clay Formation is a Lower Cretaceous sedimentary rock unit underlying areas of South East England, between the North and South Downs, in an area called the Weald Basin. It is the uppermost unit of the Wealden Group of ro ...

,

England England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe ...

. A 1997 followup to this preliminary paper referred MNHN GDF 365 and 366 to an indeterminate ''Baryonyx'' species, regardless of their younger geological age. In

1998 1998 was designated as the ''International Year of the Ocean''. Events January * January 6 – The ''Lunar Prospector'' spacecraft is launched into orbit around the Moon, and later finds evidence for frozen water, in soil in permanently s ...

, Taquet and American

geologist A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, alt ...

Dale Russell used the bones to erect the new

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial n ...

''Cristatusaurus,'' with the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen( ...

being ''Cristatusaurus lapparenti''. Its generic name is derived from the

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

''crista'' (for "crest"), and refers to a

sagittal crest A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...

on the snout. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

honors the late French paleontologist Albert-Félix de Lapparent, due to his contributions to dinosaur-related discoveries in the Sahara. In the same paper, several skull and vertebral fossils from the Tademaït of

Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , largest_city = capital , religi ...

were attributed to a new species of ''

Spinosaurus ''Spinosaurus'' (; ) is a genus of spinosaurid dinosaur that lived in what now is North Africa during the Cenomanian to upper Turonian stages of the Late Cretaceous period, about 99 to 93.5 million years ago. The genus was known first ...

'' called ''S. maroccanus,'' which was described and compared to ''Cristatusaurus''. ''Spinosaurus maroccanus'' is now considered by most paleontologists either a ''

nomen dubium In binomial nomenclature, a ''nomen dubium'' (Latin for "doubtful name", plural ''nomina dubia'') is a scientific name that is of unknown or doubtful application. Zoology In case of a ''nomen dubium'' it may be impossible to determine whether a s ...

'' (name of uncertain application)'''' or one

synonymous A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

with ''S. aegyptiacus.'' Two months after Taquet and Russel published their paper, another spinosaurid genus and species was named from the Erlhaz Formation, ''

Suchomimus tenerensis ''Suchomimus'' (meaning "crocodile mimic") is a genus of spinosaurid dinosaur that lived between 125 and 112 million years ago in what is now Niger, during the Aptian to early Albian stages of the Early Cretaceous period. It was named a ...

.'' Its describers, the American paleontologist

Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago and a National Geographic "explorer-in-residence" who has discovered several new dinosaur species on several continents, including at sites ...

and colleagues, agreed with Charig and Milner in that there was no distinction between the skull fossils of ''Baryonyx'' and ''Cristatusaurus''; concluding that the latter was a ''nomen dubium''.'''' In a 2003 analysis, German paleontologist Oliver Rauhut concurred with this.'''' When describing the

taxon In biology, a taxon ( back-formation from '' taxonomy''; plural taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular n ...

, Taquet and Russel based ''Cristatusaurus''s separation from ''Baryonyx'' on the former's "brevirostrine condition of premaxilla" (having a short snout). The meaning of this diagnosis has been considered obscure by various subsequent authors, who describe the specimens as almost identical to those of ''Baryonyx'' and ''Suchomimus.'' In 2002, Eric Buffetaut and Mohamed Ouaja supported ''Cristatusaurus''s junior synonymy with ''Baryonyx.'' The same year,

Hans-Dieter Sues Hans-Dieter Sues (born January 13, 1956) is a German-born American paleontologist who is Senior Scientist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. He receiv ...

and colleagues regarded both ''Cristatusaurus'' and ''Suchomimus'' as junior synonyms of ''Baryonyx,'' stating that there is no fossil evidence indicating more than one spinosaur lived in the Elrhaz Formation. More recent research has retained ''Suchomimus'' and ''Baryonyx'' as distinct genera. Others, such as Bertin Tor in 2010, and Carrano and colleagues in 2012, have referred to ''Cristatusaurus'' as an indeterminate baryonychine, because of how fragmentary its remains are. In 2016, Christophe Hendrickx,

Octávio Mateus Octávio Mateus (born 1975) is a Portuguese dinosaur paleontologist and biologist Professor of Paleontology at the Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa. He graduated in Universidade de Évora and received his PhD at ...

, and Buffetaut noted that Taquet and Russel might have interpreted ''Cristatusaurus'' as having a shorter snout than ''Baryonyx'' by mistaking the notch where the maxillae articulated with the premaxillae for the nostril openings. Since both ''Suchomimus'' and ''Baryonyx'' have more completely preserved premaxillae, while ''Cristatusaurus'' only has the frontmost part of this bone known, Hendrickx and colleagues considered it possible that ''Cristatusaurus''s snout was just as long as in ''Baryonyx''. Therefore, they agreed with previous authors in the ambiguity of Taquet and Russel's diagnosis. Hendrickx and colleagues stated that since ''Cristatusaurus'' and ''Suchomimus'' are nearly identical and both hail from the same

stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize ...

, they are almost certainly synonyms. The researchers found ''Cristatusaurus'' and ''Suchomimus'' similar in that they both had premaxillary crests, similar size ratio of tooth sockets, and shallow depressions in front of their nostril openings. However, since these features are minor and may vary within species as well as depending on age and sex, Hendrickx and colleagues did not identify any definitive

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

(distinguishing features) of ''Cristatusaurus''s holotype, and thus considered the taxon a ''nomen dubium'' until its

postcrania Postcrania (postcranium, adjective: postcranial) in zoology and vertebrate paleontology is all or part of the skeleton apart from the skull. Frequently, fossil remains, e.g. of dinosaurs or other extinct tetrapods, consist of partial or isolated s ...

l remains are more closely examined''.'' Given that it was named first, ''Cristatusaurus lapparenti'' has priority over ''Suchomimus tenerensis'' in the case that they become synonymized. In a 2017 study, Marcos Sales and Cesar Schultz compared the holotype of ''Cristatusaurus'' (MNHN GDF 366) to the referred snout of ''Suchomimus'' (MNN GDF501). Both of them exhibit a narrow rim across the top of their premaxillae. However, ''Cristatusaurus''s convex secondary palate is clearly visible in side view (situated under the premaxillary teeth), whereas in ''Suchomimus'' it is discernible only through cracks on the fossil snout. It was also pointed out that where known, the upward-sloping process of ''Cristatusaurus''s maxilla is narrower than in ''Suchomimus''. The researchers concluded that further study is needed to determine whether these differences are possible

autapomorphies In phylogenetics, an autapomorphy is a distinctive feature, known as a derived trait, that is unique to a given taxon. That is, it is found only in one taxon, but not found in any others or outgroup taxa, not even those most closely related to t ...

(distinguishing features) between the taxa, or if they are the result of

ontogenetic Ontogeny (also ontogenesis) is the origination and development of an organism (both physical and psychological, e.g., moral development), usually from the time of fertilization of the egg to adult. The term can also be used to refer to the s ...

(developmental) changes, given that the ''Cristatusaurus'' holotype represents a younger individual. In a 2021 study Cristatusaurus assigned just outside of Baryonychinae and differentiated from Suchomimus as a valid genus.

Description

In 2012, American vertebrate paleontologist

Thomas R. Holtz Jr. Thomas Richard Holtz Jr. (born September 13, 1965) is an American vertebrate palaeontologist, author, and principal lecturer at the University of Maryland's Department of Geology. He has published extensively on the phylogeny, morphology, ecomorp ...

tentatively estimated ''Cristatusaurus'' at around in length and weighing between .Holtz, Thomas R. Jr. (2011) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'
Winter 2010 Appendix.
/ref> The holotype premaxillae are long and tall. The other known set of premaxillae (specimen MNHN GDF 365) are larger at long and tall. The holotype's smaller size, smoother surface, and lack of

co-ossified Ossification (also called osteogenesis or bone mineralization) in bone remodeling is the process of laying down new bone material by cells named osteoblasts. It is synonymous with bone tissue formation. There are two processes resulting in t ...

(fused) sutures all indicate that it belongs to a juvenile individual; while MNHN GDF 365 probably represents an adult. The tip of ''Cristatusaurus''s premaxilla was short and expanded, while the rear end was narrowed near the suture with the maxilla; this rosette-like snout shape was characteristic of spinosaurids. The front of the upper jaw was concave on the bottom, shaped to interlock with what would have been the convex and also enlarged tip of the mandible's dentary bone. A thin sagittal crest ran lengthwise on top of the premaxillae, a condition present in ''Baryonyx'' and ''Suchomimus'', and very prominent in ''Angaturama'' (a possible synonym of ''

Irritator ''Irritator'' is a genus of spinosaurid dinosaur that lived in what is now Brazil during the Albian stage of the Early Cretaceous Period, about 113 to 110 million years ago. It is known from a nearly complete skull found in the Romualdo Fo ...

''). Like all spinosaurids, ''Cristatusaurus''s (bony nostrils) were positioned further back on the skull that in typical theropods. Two bony

processes A process is a series or set of activities that interact to produce a result; it may occur once-only or be recurrent or periodic. Things called a process include: Business and management *Business process, activities that produce a specific se ...

extended across the underside of the snout, in a convex structure that formed the animal's

secondary palate The secondary palate is an anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates. In human embryology, it refers to that portion of the hard palate that is formed by the growth of the two palatine shelves med ...

. This condition is observed in all extant

crocodilia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest livi ...

ns, but not in most theropod dinosaurs; however, it was a common trait among spinosaurids. Cristatusaurus_premaxillae

''Cristatusaurus''s dental (tooth sockets) were closely spaced, those in the maxilla and dentary were flattened somewhat sideways; while the ones in the premaxillae were large and mostly circular, with the frontmost alveoli being the largest. Partial tooth crowns preserved in some alveoli show that the teeth were finely , with flutes (lengthwise ridges) on their

lingual Lingual may refer to: * Tongue, a muscular hydrostat on the floors of the mouths of most vertebrates which manipulates food for mastication * Lingual, in palaeontology, the side of the teeth that faces the tongue * Lingual artery arises from the e ...

(inward-facing side of teeth) surface. Both premaxilla specimens had seven alveoli on each side, the same number as in ''Suchomimus'', ''Angaturama'', ''

Oxalaia ''Oxalaia'' (in reference to the African deity '' Oxalá'') is a genus of spinosaurid dinosaur that lived in what is now the Northeast Region of Brazil during the Cenomanian stage of the Late Cretaceous period, sometime between 100.5 and 93 ...

'', and the ''Spinosaurus maroccanus'' specimen. One of the dorsal vertebrae (MNHN GDF 358) measured in length, which is equal to the largest known vertebrae of ''Spinosaurus maroccanus''. The preserved base of one of ''Cristatusaurus''s vertebral

neural spines The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic i ...

(MNHN GDF 359) was thick in comparison to the measurement seen in an equivalent ''Spinosaurus'' vertebra, indicating that ''Cristatusaurus''s neural spines were probably not as tall as those of ''Spinosaurus''. Of the two manual

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulate Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammal ...

s (claws) referred to ''Cristatusaurus'', one was equivalent in size to those found for ''Suchomimus'' and ''Baryonyx'', while the other was about 25 to 30 percent smaller. As a spinosaur, it would have wielded these claws with three-fingered hands carried by robust arms.

Classification

Suchomimus, Cristatusaurus, and Baryonyx rostra

Spinosaurids were large

bipedal Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' 'double' ...

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other ...

s with well-built forelimbs and elongated, crocodile-like skulls. The taxonomic and

phylogenetic In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups o ...

affinities of the group are subject to active research and debate, given that in comparison to other theropod groups, many of the family's taxa (including ''Cristatusaurus'') are based on relatively poor fossil material. Traditionally the family has been divided into two

subfamilies In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end subfamily botanical names with "-oideae", and zoologi ...

: Spinosaurinae, which includes genera like ''Irritator'', ''Spinosaurus,'' and ''Oxalaia''; and Baryonychinae, which includes ''Baryonyx'' and ''Suchomimus''. Although the genus and species placement of ''Cristatusaurus lapparenti'' is disputed, its fossils certainly belong to a member of the baryonychinae, because of its more forwardly placed external nostrils; relatively larger first premaxillary teeth; and more closely spaced tooth sockets than in spinosaurines; as well as the presence of fine serrations, in contrast to spinosaurines lacking them entirely. However, authors like Sales and Schultz have questioned the

monophyly In cladistics for a group of organisms, monophyly is the condition of being a clade—that is, a group of taxa composed only of a common ancestor (or more precisely an ancestral population) and all of its lineal descendants. Monophyletic gr ...

of Baryonychinae (meaning it might be an unnatural group), stating that the South American spinosaurids ''Angaturama'' and ''Irritator'' represent intermediate forms between Baryonychinae and Spinosaurinae, based on their craniodental (skull and tooth) features. Their

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 ...

can be seen below.

Paleoecology

The Elrhaz Formation, part of the Tegama Group, consists mainly of

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluv ...

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

s with low relief, much of which is obscured by sand dunes. The

sediments Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand a ...

are coarse- to medium-grained, with almost no fine-grained horizons. ''Cristatusaurus'' lived in what is now Niger, during the late

Aptian The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous Epoch or Series and encompasses the time from 121.4 ± 1.0 Ma to 113.0 ± 1.0 Ma (million years ag ...

to early

Albian The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± ...

stages of the

Early Cretaceous The Early Cretaceous (geochronological name) or the Lower Cretaceous ( chronostratigraphic name), is the earlier or lower of the two major divisions of the Cretaceous. It is usually considered to stretch from 145 Ma to 100.5 Ma. Geology Pr ...

Period, 112 million years ago. The sediment layers of the formation have been interpreted as an inland habitat of extensive freshwater

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

s and fast-moving rivers, with a tropical climate that likely experienced seasonal dry periods.. Cristatusaurus_lapparenti_by_PaleoGeek

This environment was home to a variety of fauna including dinosaurs,

pterosaur Pterosaurs (; from Greek ''pteron'' and ''sauros'', meaning "wing lizard") is an extinct clade of flying reptiles in the Order (biology), order, Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cre ...

s,

chelonians Turtles are an order (biology), order of reptiles known as Testudines, characterized by a special turtle shell, shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) an ...

, fish,

hybodont sharks Hybodontidae is an extinct family of sharks that first appeared in the Mississippian subperiod of the Carboniferous and disappeared at the end of the Late Cretaceous.

, and freshwater

bivalves Bivalvia (), in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, biv ...

.'''' Besides ''Cristatusaurus lapparenti'' and ''Suchomimus tenerensis'', theropods such as the abelisaurid ''

Kryptops palaios ''Kryptops'' is a genus of abelisaurid theropod dinosaur from the Early Cretaceous of Niger. It is known from a partial skeleton found at the Gadoufaoua locality in the western Ténéré Desert, in rocks of the Aptian- Albian age Elrhaz Fo ...

'', the carcharodontosaurid ''

Eocarcharia dinops ''Eocarcharia'' (meaning "dawn shark") is a genus of carcharodontosaurid theropod dinosaur from the Early Cretaceous Elrhaz Formation that lived in the Sahara 112 million years ago, in what today is the country of Niger. It was discovered ...

'', and an unknown

noasaurid 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 ...

have been found. Herbivorous dinosaurs of the region included

iguanodontia Iguanodontia (the iguanodonts) is a clade of herbivorous dinosaurs that lived from the Middle Jurassic to Late Cretaceous. Some members include ''Camptosaurus'', '' Dryosaurus'', '' Iguanodon'', '' Tenontosaurus'', and the hadrosaurids or "duck- ...

ns like '' Ouranosaurus nigeriensis'', ''

Elrhazosaurus nigeriensis ''Elrhazosaurus'' (meaning " Elrhaz lizard") is a genus of basal iguanodontian dinosaur, known from isolated bones found in Early Cretaceous rocks of Niger. These bones were initially thought to belong to a species of the related dryosaurid '' ...

'', '' Lurdusaurus arenatus'', and two sauropods: '' Nigersaurus taqueti'', and an unnamed

titanosaur Titanosaurs (or titanosaurians; members of the group Titanosauria) were a diverse group of sauropod dinosaurs, including genera from all seven continents. The titanosaurs were the last surviving group of long-necked sauropods, with taxa still th ...

. Crocodylomorphs were abundant; represented by the giant pholidosaur species '' Sarcosuchus imperator'', as well as small notosuchians like '' Anatosuchus minor'', ''

Araripesuchus wegeneri ''Araripesuchus'' is a genus of extinct crocodyliform that existed during the Cretaceous period of the late Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is ...

'', and '' Stolokrosuchus lapparenti''. The local flora probably consisted mainly of

ferns A fern (Polypodiopsida or Polypodiophyta ) is a member of a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. The polypodiophytes include all living pteridophytes except t ...

,

horsetails ''Equisetum'' (; horsetail, snake grass, puzzlegrass) is the only living genus in Equisetaceae, a family of ferns, which reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass ...

, and

angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (), commonly called angiosperms. They include all forbs (flowering plants without a woody stem), grasses and grass-like plants, a vast majority of br ...

, based on the dietary adaptations of the sauropods that lived there. A

semiaquatic In biology, semiaquatic can refer to various types of animals that spend part of their time in water, or plants that naturally grow partially submerged in water. Examples are given below. Semiaquatic animals Semi aquatic animals include: * Ve ...

lifestyle has been proposed for many spinosaurids, on account of their unusual anatomical traits and bone

histology Histology, also known as microscopic anatomy or microanatomy, is the branch of biology which studies the microscopic anatomy of biological tissues. Histology is the microscopic counterpart to gross anatomy, which looks at larger structures vi ...

. ''Cristatusaurus''s teeth would have likely been used for piercing and gripping prey items, rather than slicing flesh, as indicated by their subcircular cross section and reduced serrations. Its teeth, combined with the

sinusoidal A sine wave, sinusoidal wave, or just sinusoid is a mathematical curve defined in terms of the '' sine'' trigonometric function, of which it is the graph. It is a type of continuous wave and also a smooth periodic function. It occurs often in ...

(wave-like) curvature of the jaws, would have performed as tan efficient trap for fish. The retracted nostrils would have allowed it to submerge its snout further underwater than most theropods, while still being able to breathe; and the bony secondary palate is theorized to have reinforced the skull against bending stresses when feeding. The use of the giant recurved manual unguals of spinosaurs is still under debate; suggested functions have ranged from

gaffing In fishing, a gaff is a handheld pole with a sharp hook or sideway spike on the distal end, which is used to swing and stab into the body of a large fish like a pickaxe, and then pull the fish out of the water like using a pike pole. Ideally, ...

aquatic prey out of the water, to scavenging carcasses or digging.

References

{{Taxonbar, from=Q134640 Spinosaurids Early Cretaceous dinosaurs of Africa Fossil taxa described in 1998 Taxa named by Philippe Taquet Taxa named by Dale Russell