''Tytthostonyx'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

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 enviro ...

. Found in the much-debated

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

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 of ...

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

Procellariiformes Procellariiformes is an order (biology), order of seabirds that comprises four family (biology), families: the albatrosses, the Procellariidae, petrels and shearwaters, and two families of storm petrels. Formerly called Tubinares and still call ...

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 Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

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