Cristatusaurus
   HOME

TheInfoList



OR:

''Cristatusaurus'' 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
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 ...
that lived during 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 ...
Period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...
of what is now
Niger Niger, officially the Republic of the Niger, is a landlocked country in West Africa. It is a unitary state Geography of Niger#Political geography, bordered by Libya to the Libya–Niger border, north-east, Chad to the Chad–Niger border, east ...
, 112 million years ago. It was a
baryonychine Baryonychinae is an extinct clade or subfamily of spinosaurids from the Early Cretaceous of Europe and West Africa. The clade was named by Charig & Milner in 1986 and defined by Sereno et al. in 1998 and Holtz et al. in 2004 as all taxa more close ...
member of the
Spinosauridae Spinosauridae (or spinosaurids) is a clade or Family (taxonomy), family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. ...
, a group of large
bipedal Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) 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'' ...
carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...
s with well-built forelimbs and elongated, crocodile-like skulls. The
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
''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 Lunar water, frozen water, in soil i ...
by scientists
Philippe Taquet Philippe Taquet (born 25 April 1940 Saint-Quentin, Aisne) is a French paleontologist who specializes in dinosaur systematics of finds primarily in northern Africa. He is a member of the French Academy of Sciences since 30 November 2004, president ...
and
Dale Russell Dale Alan Russell (27 December 1937 – 21 December 2019) was an American-Canadian geologist and palaeontologist. Throughout his career Russell worked as the Curator of Fossil Vertebrates at the Canadian Museum of Nature, Research Professor at ...
, on the basis of jaw bones and some
vertebra Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spina ...
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 preserve ...
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 excepti ...
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 as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
Albert-Félix de Lapparent Albert-Félix de Lapparent (; 1905–1975) was a French people, French Palaeontology, palaeontologist. He was also a Society of Saint-Sulpice, Sulpician priest. He undertook a number of fossil-hunting explorations in the Sahara desert. He contribute ...
. ''Cristatusaurus'' is known from the
Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...
to
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 ...
Elrhaz Formation The Elrhaz Formation is a geological Formation (geology), formation in Niger, West Africa. Its strata date back to the Early Cretaceous, about 125 to 112 million years ago. Dinosaur remains are among the fossils that have been recovered from the ...
, 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 b ...
and
iguanodontia Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...
n dinosaurs, other theropods, and various
crocodylomorphs Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably more ...
. 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'', from Ancient Greek ''σούχος'' (''soúkhos''), meaning "crocodile", and Latin ''mimus'', meaning "actor", is a genus of spinosaurid dinosaur that lived between 125 and 112 million years ago in what is now Niger, North A ...
,'' 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 ...
'', 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 ovum, egg to adult. The term can also be used to refer to t ...
(changes in an organism during growth). A recent study differentiated ''Cristatusaurus'' from ''Suchomimus'' and assigned it as a valid spinosaurid genus, placing 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 preserve ...
s of ''Cristatusaurus'' were found in 1973 by French
paleontologist Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
Philippe Taquet Philippe Taquet (born 25 April 1940 Saint-Quentin, Aisne) is a French paleontologist who specializes in dinosaur systematics of finds primarily in northern Africa. He is a member of the French Academy of Sciences since 30 November 2004, president ...
at Gadoufaoua, a locality within the
Elrhaz Formation The Elrhaz Formation is a geological Formation (geology), formation in Niger, West Africa. Its strata date back to the Early Cretaceous, about 125 to 112 million years ago. Dinosaur remains are among the fossils that have been recovered from the ...
in
Niger Niger, officially the Republic of the Niger, is a landlocked country in West Africa. It is a unitary state Geography of Niger#Political geography, bordered by Libya to the Libya–Niger border, north-east, Chad to the Chad–Niger border, east ...
. The
holotype specimen A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was Species description, formally described. It is either the single such physical example (or illus ...
, cataloged under the number
MNHN The French National Museum of Natural History ( ; abbr. MNHN) is the national natural history museum of France and a of higher education part of Sorbonne University. The main museum, with four galleries, is located in Paris, France, within the ...
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 mammals h ...
e (frontmost snout bones), a partial right (main upper jaw bone), and a fragment from the
mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...
. 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 (biology), isotype ...
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 coupling in its construction. This coupling works as a large pivot joint, allowing it to bend and turn more sharply. There are many kinds, from heavy equipment to buse ...
premaxillae; as well as MNHN GDF 357, 358, 359 and 361, four
dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebra (anatomy), vertebrae of intermediate size between the ce ...
. 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 (; 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 ...
within the
family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
Spinosauridae Spinosauridae (or spinosaurids) is a clade or Family (taxonomy), family of tetanuran theropod dinosaurs comprising ten to seventeen known genera. Spinosaurid fossils have been recovered worldwide, including Africa, Europe, South America, and Asia. ...
, 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. 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 en ...
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 paleontologist who, in 1986 alongside Alan Charig, described the dinosaur ''Baryonyx''. Early life Milner was born Angela Girven in Gosforth, daughter of Cyril and Luci ...
considered Taquet's jaw elements nearly indistinguishable from those of the spinosaurid ''
Baryonyx walkeri ''Baryonyx'' () is a genus of theropod dinosaur which lived in the Barremian Geological stage, stage of the Early Cretaceous Period (geology), period, about 130–125 million years ago. The first skeleton was discovered in 1983 in the Smokejack ...
''; 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 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 ...
of the Weald Clay Formation,
England England is a Countries of the United Kingdom, country that is part of the United Kingdom. It is located on the island of Great Britain, of which it covers about 62%, and List of islands of England, more than 100 smaller adjacent islands. It ...
. 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 Lunar water, frozen water, in soil i ...
, Taquet and American
geologist A geologist is a scientist who studies the structure, composition, and History of Earth, history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the Field research, ...
Dale Russell Dale Alan Russell (27 December 1937 – 21 December 2019) was an American-Canadian geologist and palaeontologist. Throughout his career Russell worked as the Curator of Fossil Vertebrates at the Canadian Museum of Nature, Research Professor at ...
used the bones to erect the new
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 ...
''Cristatusaurus,'' with the
type species In International_Code_of_Zoological_Nomenclature, 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 spe ...
being ''Cristatusaurus lapparenti''. Its generic name is derived from the
Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...
''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 excepti ...
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 Albert-Félix de Lapparent (; 1905–1975) was a French people, French Palaeontology, palaeontologist. He was also a Society of Saint-Sulpice, Sulpician priest. He undertook a number of fossil-hunting explorations in the Sahara desert. He contribute ...
, due to his contributions to dinosaur-related discoveries in the Sahara. In the same paper, several skull and vertebral fossils from the
Tademaït Tademaït is a natural region in the Sahara Desert right in the centre of Algeria. It is located north of In Salah and south of the Grand Erg Occidental in the Adrar District of Adrar Province, El Ménia District of Ghardaïa Province and the n ...
of
Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...
were attributed to a new species of ''
Spinosaurus ''Spinosaurus'' (; ) is a genus of large spinosaurid theropod dinosaurs that lived in what now is North Africa during the Cenomanian faunal stage, stage of the Late Cretaceous Period (geology), period, about 100 to 94 annum, million year ...
'' 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 ...
'' (name of uncertain application)'''' or one
synonymous A synonym is a word, morpheme, or phrase that means precisely 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 a ...
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.'' Its describers, the American paleontologist
Paul Sereno Paul Callistus Sereno (born October 11, 1957) is a professor of paleontology at the University of Chicago who has discovered several new dinosaur species on several continents, including at sites in Inner Mongolia, Argentina, Morocco and Niger. ...
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''; : 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 name and ...
, 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 The given name Eric, Erich, Erikk, Erik, Erick, Eirik, or Eiríkur is derived from the Old Norse name ''Eiríkr'' (or ''Eríkr'' in Old East Norse due to monophthongization). The first element, ''ei-'' may be derived from the older Proto-Nor ...
and Mohamed Ouaja supported ''Cristatusaurus''s
junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...
y with ''Baryonyx.'' The same year,
Hans-Dieter Sues Hans-Dieter Sues (born 1956) is a German-born American palaeontologist who is a Senior Research Geologist and Curator of Vertebrate Paleontology at the National Museum of Natural History of the Smithsonian Institution in Washington, DC. Career ...
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 Baryonychinae is an extinct clade or subfamily of spinosaurids from the Early Cretaceous of Europe and West Africa. The clade was named by Charig & Milner in 1986 and defined by Sereno et al. in 1998 and Holtz et al. in 2004 as all taxa more close ...
, because of how fragmentary its remains are. In 2016, Christophe Hendrickx,
Octávio Mateus Octávio Mateus (born 1975) is a Portugal, Portuguese dinosaur paleontologist and biologist Professor of Paleontology at the Faculdade de Ciências e Tecnologia da NOVA University Lisbon, Universidade Nova de Lisboa. He graduated in University of ...
, 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 characteriz ...
, 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 ...
(distinguishing features) of ''Cristatusaurus''s holotype, and thus considered the taxon a ''nomen dubium'' until its
postcrania The postcranium ("behind the cranium"; plural: postcrania) or postcranial skeleton in zoology and vertebrate paleontology is the skeleton apart from the skull. The postcranium encompasses the axial skeleton, which includes the entirety of the verte ...
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 ...
(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 stu ...
(developmental) changes, given that the ''Cristatusaurus'' holotype represents a younger individual. A 2021 study assigned ''Cristatusaurus'' just outside of Baryonychinae and differentiated from ''Suchomimus'' as a valid genus, supporting its independence as a genus.


Description

In 2012,
American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, p ...
vertebrate paleontologist Thomas R. Holtz Jr. 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.
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 (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 Rosette is the French diminutive of ''rose''. It may refer to: Flower shaped designs * Rosette (award), a mark awarded by an organisation * Rosette (design), a small flower design *hence, various flower-shaped or rotational symmetric forms: ** R ...
-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 Spinosauridae, spinosaurid dinosaur that lived in what is now Brazil during the Albian Geological stage, stage of the Early Cretaceous Geological period, Period, about 113 to 110 million years ago. It is known from ...
''). Like all spinosaurids, ''Cristatusaurus''s (bony nostrils) were positioned further back on the skull that in typical theropods. Two bony processes 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 () is an order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorph pseudosuchia ...
ns, but not in most theropod dinosaurs; however, it was a common trait among spinosaurids. ''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 A tooth (: teeth) is a hard, calcification, calcified structure found in the jaws (or mouths) of many vertebrates and used to Mastication, break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturin ...
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 controversial genus of Spinosauridae, spinosaurid dinosaur that lived in what is now the Northeast Region, Brazil, Northeast Region of Brazil during the Cenomanian Geological stage, ...
'', 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 Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...
(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 ungulates have ungual phalanges, as did the sauropod Sauropoda (), whose members are known as sauropods (; ...
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

Spinosaurids were large
bipedal Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) 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'' ...
carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...
s with well-built forelimbs and elongated, crocodile-like skulls. The
taxonomic 280px, Generalized scheme of taxonomy Taxonomy is a practice and science concerned with classification or categorization. Typically, there are two parts to it: the development of an underlying scheme of classes (a taxonomy) and the allocation ...
and
phylogenetic In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical dat ...
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 botanical subfamily names with "-oideae", and zool ...
: 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 biological cladistics for the classification of organisms, monophyly is the condition of a taxonomic grouping being a clade – that is, a grouping of organisms which meets these criteria: # the grouping contains its own most recent comm ...
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 language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
can be seen below.


Paleoecology

The Elrhaz Formation, part of the Tegama Group, consists mainly of
fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
s with low relief, much of which is obscured by sand dunes. The
sediments Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
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 (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 ...
to early
Albian The Albian is both an age (geology), age of the geologic timescale and a stage (stratigraphy), stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early Cretaceous, Early/Lower Cretaceous epoch (geology), Epoch/s ...
stages Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...
of 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 ...
Period Period may refer to: Common uses * Period (punctuation) * Era, a length or span of time *Menstruation, commonly referred to as a "period" Arts, entertainment, and media * Period (music), a concept in musical composition * Periodic sentence (o ...
, 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. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
s and fast-moving rivers, with a tropical climate that likely experienced seasonal dry periods.. This environment was home to a variety of fauna including dinosaurs,
pterosaur Pterosaurs are an extinct clade of flying reptiles in the order Pterosauria. They existed during most of the Mesozoic: from the Late Triassic to the end of the Cretaceous (228 million to 66 million years ago). Pterosaurs are the earli ...
s, chelonians, fish, hybodont sharks, and freshwater
bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...
.'''' Besides ''Cristatusaurus lapparenti'' and ''Suchomimus tenerensis'', theropods such as the
abelisaurid 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 foun ...
'' Kryptops palaios'', the
carcharodontosaurid Carcharodontosauridae (carcharodontosaurids; from the Greek καρχαροδοντόσαυρος, ''carcharodontósauros'': "shark-toothed lizards") is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae ...
'' Eocarcharia dinops'' and the noasaurid ''
Afromimus tenerensis ''Afromimus'' (meaning "Africa mimic") is a genus of ceratosaurian theropod dinosaur from the Early Cretaceous Elrhaz Formation of Niger. It contains a single species, ''A. tenerensis'', named in 2017 by Paul Sereno from parts of the right leg, v ...
'' have been found. Herbivorous dinosaurs of the region included
iguanodontia Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (). They represent one of the most successful groups of herbivorous dinosaurs during the Cretaceous. The most primitive members of the group were bipedal and relatively sm ...
ns like ''
Ouranosaurus nigeriensis ''Ouranosaurus'' is a genus of herbivorous basal hadrosauriform dinosaur that lived during the Aptian stage of the Early Cretaceous of modern-day Niger and Cameroon. ''Ouranosaurus'' measured about long and weighed . Two rather complete fossils ...
'', '' Elrhazosaurus nigeriensis'', '' Lurdusaurus arenatus'', and two
sauropods 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 b ...
: '' 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 thr ...
.
Crocodylomorphs Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably more ...
were abundant; represented by the giant pholidosaur species '' Sarcosuchus imperator'', as well as small
notosuchians Notosuchia is a clade of primarily Gondwanan mesoeucrocodylian Crocodylomorpha, crocodylomorphs that lived during the Jurassic and Cretaceous. Some phylogeny, phylogenies recover Sebecosuchia as a clade within Notosuchia, others as a sister group ...
like '' Anatosuchus minor'', ''
Araripesuchus wegeneri ''Araripesuchus'' is a genus of extinct crocodyliform that existed during the Cretaceous period of the late Mesozoic era some 125 to 66 million years ago. ''Araripesuchus'' is generally considered to be a notosuchian (belonging to the clade Mesoe ...
'', and '' Stolokrosuchus lapparenti''. The local flora probably consisted mainly of
ferns The ferns (Polypodiopsida or Polypodiophyta) are a group of vascular plants (plants with xylem and phloem) that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular, i.e., having specialized tissue ...
,
horsetails ''Equisetum'' (; horsetail) is the only living genus in Equisetaceae, a family of vascular plants that reproduce by spores rather than seeds. ''Equisetum'' is a "living fossil", the only living genus of the entire subclass Equisetidae, which f ...
, and
angiosperms Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed within a fruit. T ...
, based on the dietary adaptations of the sauropods that lived there. A
semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...
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 that studies the microscopic anatomy of biological tissue (biology), tissues. Histology is the microscopic counterpart to gross anatomy, which looks at large ...
. ''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 sinusoid (symbol: ∿) is a periodic wave whose waveform (shape) is the trigonometric sine function. In mechanics, as a linear motion over time, this is '' simple harmonic motion''; as rotation, it correspond ...
(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 aquatic prey out of the water, to scavenging carcasses or digging.


References

{{Taxonbar, from=Q134640 Spinosauridae Dinosaur genera Albian dinosaurs Fossil taxa described in 1998 Taxa named by Philippe Taquet Taxa named by Dale Russell Dinosaurs of Niger