''Thoracosaurus'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus of eusuchian

crocodylomorph 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. During Mesozoic and early Cenozoic times, cro ...

which existed during the Late Cretaceous and Early Paleocene in North America and Europe. The taxon had traditionally been thought to be related to the modern

false gharial The false gharial (''Tomistoma schlegelii''), also known by the names Malayan gharial, Sunda gharial and tomistoma is a freshwater crocodilian of the family Gavialidae native to Peninsular Malaysia, Borneo, Sumatra and Java. It is listed as Vu ...

, largely because the nasal bones contact the premaxillae. Phylogenetic work starting in the 1990s instead supported affinities within Gavialoidea exclusive of such forms, although a 2018 tip dating study simultaneously using morphological,

molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

(

DNA sequencing DNA sequencing is the process of determining the nucleic acid sequence – the order of nucleotides in DNA. It includes any method or technology that is used to determine the order of the four bases: adenine, guanine, cytosine, and thymine. Th ...

), and stratigraphic ( fossil age) data suggests that it might have been a non- crocodylian

eusuchian Eusuchia is a clade of crocodylomorphs that first appeared in the Early Cretaceous with ''Hylaeochampsa''. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades ...

. The genus contains the type species ''Thoracosaurus neocesariensis'' in North America, and what is either ''Thoracosaurus isorhynchus'' or ''Thoracosaurus macrorhynchus'' from Europe; a recent review argues that ''T. macrorhynchus'' is a junior

synonym 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 ...

of ''T. isorhynchus,'' but it is unclear whether the type of ''T. isorhynchus'' allows differentiation of European and North American ''Thoracosaurus;'' if not, then ''T. isorhynchus'' would be 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 ...

''. A number of species have been referred to this genus, but most are dubious. Thoracosaurus macrorhynchus - Maastricht.jpg, ''Thoracosaurus macrorhynchus'' skull at the Naturalis Museum in Leiden, Netherlands Image:Thoracosaurus.jpg, ''Thoracosaurus sp.'' teeth at the Geological Museum, Copenhagen

References

Neosuchians Late Cretaceous crocodylomorphs Paleocene crocodylomorphs Late Cretaceous first appearances Cretaceous–Paleogene boundary Paleocene extinctions Cretaceous reptiles of North America Paleocene reptiles of North America Hell Creek fauna Fossil taxa described in 1852 Taxa named by Joseph Leidy Prehistoric pseudosuchian genera {{paleo-archosaur-stub