Eonatator BW
   HOME

TheInfoList



OR:

''Eonatator'' is an extinct
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 marine lizard belonging to the
mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains wer ...
family. It is a close relative of ''
Halisaurus ''Halisaurus'' is an extinct genus of mosasaur named by Othniel Charles Marsh in 1869. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...
'', and part of the same subfamily, the
Halisaurinae The Halisaurinae are a subfamily of mosasaurs, a group of Late Cretaceous marine lizards. They were small to medium-sized, ranging from just under 3 meters in ''Eonatator sternbergi'' to as much as 8 or 9 meters in ''Pluridens serpentis''. The ...
. It is known from the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
of
North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
,
Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
and
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
. Originally, this
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 ...
was included within ''Halisaurus'', but was placed in its own genus, which also led to the subfamily Halisaurinae being created for the two genera.


Discovery and naming

''Eonatator'' is known from the
Smoky Hill Chalk The Smoky Hill Chalk Member of the Niobrara Chalk formation is a Cretaceous conservation Lagerstätte, or fossil rich geological member, known primarily for its exceptionally well-preserved marine reptiles. Named for the Smoky Hill River, the S ...
Member of the Niobrara Chalk Formation ( Late Coniacian to Early Campanian) of
Kansas Kansas ( ) is a landlocked U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Nebraska to the north; Missouri to the east; Oklahoma to the south; and Colorado to the west. Kansas is named a ...
, from the
Eutaw Formation The Eutaw Formation is a geological Formation (geology), formation in North America, within the United States, U.S. states of Alabama, Georgia (U.S. state), Georgia, and Mississippi. The strata date from the late Coniacian to the early Santonian S ...
(
Santonian The Santonian is an age in the geologic timescale or a chronostratigraphic stage. It is a subdivision of the Late Cretaceous Epoch or Upper Cretaceous Series. It spans the time between 86.3 ± 0.7 mya ( million years ago) and 83.6 ± 0.7 m ...
) and
Mooreville Chalk Formation The Mooreville Chalk is a geological formation in North America, within the U.S. states of Alabama and Mississippi, which were part of the subcontinent of Appalachia. The strata date back to the early Santonian to the early Campanian stage of th ...
(
Selma Group The Selma Group is a geological formation in North America, within the U.S. states of Alabama, Mississippi, and Tennessee. The strata date from the Santonian to the Maastrichtian stages of the Late Cretaceous. The group is composed of, in ascend ...
; Santonian-Lower Campanian) of
Alabama Alabama ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South, Deep Southern regions of the United States. It borders Tennessee to the north, Georgia (U.S. state), Georgia to the east, Florida and the Gu ...
(
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
), from the Kristianstad Basin of southern
Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...
(late early Campanian), and the unit Nivel de Lutitas y Arenas (Campanian) of the Olini Group in La Mesa,
Colombia Colombia, officially the Republic of Colombia, is a country primarily located in South America with Insular region of Colombia, insular regions in North America. The Colombian mainland is bordered by the Caribbean Sea to the north, Venezuel ...
. The name ''Eonatator'' means "dawn swimmer" (
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
''eos'' = dawn +
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 ...
''natator'' = swimmer). Originally, it contained only a single
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
, ''E. sternbergii''. The species is named in honour of
Charles Hazelius Sternberg Charles Hazelius Sternberg (June 15, 1850 – July 20, 1943) was an American fossil collector and paleontology, paleontologist. He was active in both fields from 1876 to 1928, and collected fossils for Edward Drinker Cope and Othniel C. Marsh, ...
and his son, Levi, who discovered the type specimen in the Niobrara Chalk during the summer of 1918. A second species, ''E. coellensis'', was named for the town of Coello in the
Department of Tolima Tolima () is one of the 32 departments of Colombia, located in the Andean region, in the center-west of the country. It is bordered on the north and the west by the department of Caldas; on the east by the department of Cundinamarca; on the ...
in Colombia, near of which it was discovered.


Description

''Eonatator'' was a small mosasaur, with the type specimen of ''Eonatator sternbergii'', UPI R 163, measuring approximately long. Bardet et al. (2005, p. 465) diagnose ''Eonatator sternbergii'' as follows: "Ambiguous characters:
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 ...
-
maxilla In vertebrates, the maxilla (: maxillae ) is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The two maxil ...
lateral suture ending posterior to 9th maxillary teeth; tail about 40% of the head and trunk length (convergent in mosasaurines);
caudal Caudal may refer to: Anatomy * Caudal (anatomical term) (from Latin ''cauda''; tail), used to describe how close something is to the trailing end of an organism * Caudal artery, the portion of the dorsal aorta of a vertebrate that passes into th ...
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 ...
length greater than width; fewer than four pygal vertebrae;
femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...
length about twice
distal Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...
width (convergent in ''Clidastes''). Autapomorphies: parietal with smooth triangular table extending very far posteriorly, bearing medium-sized circular foramen, located at distance twice its diameter from the frontal-parietal suture, and surrounded anteriorly and posteriorly by two parallel ridges; rounded quadrate with regularly convex tympanic ''ala'' (wing); vertebral formula: seven cervicals, 24 dorsals, four pygals, 28 median caudals and at least 41 terminal caudals;
humerus The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...
length approximately 2.5x distal width." ''E. coellensis'' is diagnosed by more retracted nostrils, between the 7 and the 17 maxillary teeth, premaxilla and maxilla with a short rostrum anterior to the first teeth; presence of a septomaxilla, a large prefrontal that makes most of the margin of the outer nostril, a short and wide frontal, a parietal foramen located near of the fronto-parietal suture, a triangular surface of the parietal with two medial depressions and 22 caudal vertebrae. The type specimen of ''E. coellensis'', IGM p 881237, measures long as preserved, but is missing part of its tail. This specimen had a long skull and lacked a complete tail. Still, it is remarkable for having remains of soft tissue in the ear region, the neck,
thoracic The thorax (: thoraces or thoraxes) or chest is a part of the anatomy of mammals and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main ...
and the
abdominal The abdomen (colloquially called the gut, belly, tummy, midriff, tucky, or stomach) is the front part of the torso between the thorax (chest) and pelvis in humans and in other vertebrates. The area occupied by the abdomen is called the abdominal ...
region. Under the pygal vertebrae and the seventeenth dorsal vertebra there is a series of 20 small vertebrae centra and a flattened bone, that together measure in length. It have features of the mosasauroids, with three vertebrae with haemal arches and procoelic centra, that suggest the possibility that these small bones belong to an embryo of this species, although the lack of diagnostic fossils like the skull or teeth prevents a complete identification. In any case, it will be consequent with the ovoviviparism previously reported in mosasauroids like ''
Carsosaurus ''Carsosaurus'' is a genus of extinct amphibious reptiles, in the mosasaur superfamily, containing only the species ''Carsosaurus marchesetti''. It is known from a single individual from the Komen Limestone of Slovenia. The specimen is well-pre ...
''.


Classification

Like many mosasaurs, this genus has a complicated
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 ...
history. The
type specimen In biology, a type is a particular wikt:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally associated. In other words, a type is an example that serves to ancho ...
(UPI R 163, Uppsala University Palaeontological Institute,
Uppsala Uppsala ( ; ; archaically spelled ''Upsala'') is the capital of Uppsala County and the List of urban areas in Sweden by population, fourth-largest city in Sweden, after Stockholm, Gothenburg, and Malmö. It had 177,074 inhabitants in 2019. Loc ...
, Sweden), a nearly complete skeleton, was originally referred to the genus ''Clidastes'' by Wiman and then to ''Halisaurus'' by Russell. Hence, ''Clidastes sternbergii'' became ''Halisaurus sternbergii''. Although some agreed with this generic attribution, other
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 ...
s suggested that while ''H. sternbergii'' did not belong to ''Clidastes'', its designation under ''Halisaurus'' is questionable; Lingham-Soliar (1996) referred ''H. sternbergii'' to ''C. sternbergii'' again, but this has found no acceptance in other researchers. In 2005, ''Halisaurus sternbergii'' was reassigned to its own genus, ''Eonatator'' by Nathalie Bardet and colleagues along with the description of ''Halisaurus arambourgi'' and the creation of the subfamily Halisaurinae. In the same year, Lindgren and Siverson suggested that ''Eonatator'' is an invalid junior synonym and should be classified as ''H. sternbergii'', but this has found no acceptance in other researchers who used the genus name ''Eonatator'' instead. Below is a
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 ...
following an analysis by Takuya Konishi and colleagues (
2016 2016 was designated as: * International Year of Pulses by the sixty-eighth session of the United Nations General Assembly. * International Year of Global Understanding (IYGU) by the International Council for Science (ICSU), the Internationa ...
) done during the description of '' Phosphorosaurus ponpetelegans'', which showcases the internal relationships within the Halisaurinae. The analysis excluded the dubious '' Halisaurus onchognathus'' and the genus ''
Pluridens ''Pluridens'' ("many teeth") is an extinct genus of marine lizard belonging to the Mosasauridae. ''Pluridens'' is placed in the subfamily Halisaurinae with the genera ''Phosphorosaurus'', ''Eonatator'' and ''Halisaurus''.Konishi, Takuya; Caldwell ...
''. In their 2023 description of the new ''
Halisaurus ''Halisaurus'' is an extinct genus of mosasaur named by Othniel Charles Marsh in 1869. The holotype, consisting of an angular and a basicranium fragment discovered near Hornerstown, New Jersey, already revealed a relatively unique combination ...
'' species, ''H. hebae'', Shaker ''et al''. performed a
phylogenetic analyses In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as Computational phylogenetics, phylogenetic inference. It infers the relationship among organ ...
of members of the
Halisaurinae The Halisaurinae are a subfamily of mosasaurs, a group of Late Cretaceous marine lizards. They were small to medium-sized, ranging from just under 3 meters in ''Eonatator sternbergi'' to as much as 8 or 9 meters in ''Pluridens serpentis''. The ...
. They suggested that '' Phosphorosaurus ponpetelegans'' and ''Eonatator coellensis'' were more closely related to the genus ''Halisaurus'' than the type species of their respective genera. They tentatively assigned both of these species to ''Halisaurus''. The results of their analyses are displayed in the cladogram below:


Notes


References


Further reading

* Lindgren J, Siverson M. 2005. ''Halisaurus sternbergii'', a small mosasaur with an intercontinental distribution. ''Journal of Paleontology'' 79 (4): 763–773.


External links


Kansas Mosasaurs in Sweden: the type specimen of ''Eonatator'' (''Halisaurus'') ''sternbergi'' Wiman 1920 @ Oceans of Kansas, very good photographs of type specimen
{{Portal bar, Paleontology, Colombia Russellosaurins Santonian genus first appearances Campanian genus extinctions Mosasaurs of South America Late Cretaceous reptiles of South America Cretaceous Colombia Fossils of Colombia Mosasaurs of Europe Late Cretaceous reptiles of Europe Fossils of Sweden Fossil taxa described in 2005 Taxa named by María Páramo