''Tytthostonyx'' is a

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 ...

of prehistoric

seabird Seabirds (also known as marine birds) are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same envir ...

. Found in the much-debated

Hornerstown Formation The Hornerstown Formation is a Paleogene or latest Mesozoic geologic formation in New Jersey.Weishampel, et al. (2004). "Dinosaur distribution." Pp. 517-607. The age of these deposits have been controversial. While most fossils are of animals typ ...

which straddles the

Cretaceous–Paleogene boundary The Cretaceous–Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K–T) boundary, is a geological signature, usually a thin band of rock containing much more iridium than other bands. The K–Pg boundary marks the end ...

66 million years ago, this animal was apparently closely related to the ancestor of some modern birds, such as

Procellariiformes Procellariiformes is an order of seabirds that comprises four families: the albatrosses, the petrels and shearwaters, and two families of storm petrels. Formerly called Tubinares and still called tubenoses in English, procellariiforms are of ...

and/or "

Pelecaniformes The Pelecaniformes are an order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such n ...

". A single species is placed herein, ''Tytthostonyx glauconiticus''.Olson, S. and Parris, D.C. (1987).
The Cretaceous Birds of New Jersey.
''Smithsonian Contributions to Paleontology'', 63: 22pp. It has been placed into a

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 ...

of its own, Tytthostonychidae.

References

Procellariiformes Prehistoric bird genera Late Cretaceous birds of North America Extinct birds of North America Fossil taxa described in 1987 {{paleo-bird-stub