''Gypsonictops'' is an extinct genus of

leptictida Leptictida (''leptos iktis'' "small/slender weasel") is a possibly paraphyletic extinct order of eutherian mammals. Their classification is contentious: according to cladistic studies, they may be (distantly) related to Euarchontoglires (rodents ...

mammals Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fu ...

of the

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

family Gypsonictopidae, which was described in 1927 by

George Gaylord Simpson George Gaylord Simpson (June 16, 1902 – October 6, 1984) was an American paleontologist. Simpson was perhaps the most influential paleontologist of the twentieth century, and a major participant in the modern synthesis, contributing '' Tempo ...

. Species in this genus were small mammals and the first representatives of the order

Leptictida Leptictida (''leptos iktis'' "small/slender weasel") is a possibly paraphyletic extinct order of eutherian mammals. Their classification is contentious: according to cladistic studies, they may be (distantly) related to Euarchontoglires (rodents ...

, that appeared during the

Upper Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger 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 ''creta'', ...

. The genus is thought to have gone extinct before the

Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configu ...

began, but there are indications that it may have survived into the early

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch that lasted from about 66 to 56 million years ago (mya). It is the first epoch of the Paleogene Period in the modern Cenozoic Era. The name is a combination of the Ancient Greek ''pal ...

. Fossils have been found in the United States, Belgium, and Uzbekistan. Like ''

Cimolestes ''Cimolestes'' (from Ancient Greek , 'chalk robber') is a genus of early eutherians with a full complement of teeth adapted for eating insects and other small animals. Paleontologists have disagreed on its relationship to other mammals, in part ...

'' or '' Daulestes'', it is possible that they had some distant relationship with the

ungulates Ungulates ( ) are members of the diverse clade Ungulata which primarily consists of large mammals with hooves. These include odd-toed ungulates such as horses, rhinoceroses, and tapirs; and even-toed ungulates such as cattle, pigs, giraffes, cam ...

. It is one of the few

eutherians Eutheria (; from Greek , 'good, right' and , 'beast'; ) is the clade consisting of all therian mammals that are more closely related to placentals than to marsupials. Eutherians are distinguished from noneutherians by various phenotypic ...

that existed in North America during the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

, a period in which the

multituberculates Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, ...

and the

metatherians Metatheria is a mammalian clade that includes all mammals more closely related to marsupials than to placentals. First proposed by Thomas Henry Huxley in 1880, it is a more inclusive group than the marsupials; it contains all marsupials as we ...

were the dominant ones on the continent.

Physiology

Like other

prehistoric Prehistory, also known as pre-literary history, is the period of human history between the use of the first stone tools by hominins 3.3 million years ago and the beginning of recorded history with the invention of writing systems. The use o ...

of the

in North America, ''Gypsonictops'' had a particular

dentition Dentition pertains to the development of teeth and their arrangement in the mouth. In particular, it is the characteristic arrangement, kind, and number of teeth in a given species at a given age. That is, the number, type, and morpho-physiolog ...

, with five

premolars The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...

double-rooted in the

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

, while the vast majority of mammals only had four. On the other hand, the five premolars also were a very typical feature of the most primitive

. In the same way as the species of the genus '' Leptictidium'', the P4 premolar was highly molarized, which caused confusion when analyzing a specimen of ''G. petersoni'' between P4 and molar M1. Eventually, P4 was found to be a paraconid-free premolar. It is known that the ''Gypsonictops'' were

and that they could be

placental Placental mammals (infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguishe ...

s, as they show very typical characteristics of these animals, although they belong to the

group, which includes some of the few non-placental eutherians that existed. Furthermore, the line between placental and non-placental eutherians is very thin, so the classification of ''Gypsonictops'' with precision is a very complicated task.

Taxonomy

The genus ''Gypsonictops'' was first classified within the family Leptictidae, by Simpson, along with all

of North America. This classification was maintained until 1967, year in which

Leigh Van Valen Leigh Van Valen (August 12, 1935 – October 16, 2010) was a U.S. evolutionary biologist. At the time of his death, he was professor emeritus in the Department of Ecology and Evolution at the University of Chicago. Research and interests Amongs ...

created the family Gypsonictopidae for this genus especially. In 1997,

Malcolm C. McKenna Malcolm Carnegie McKenna (1930–2008) was an American paleontologist and author on the subject. Paleontologist McKenna began his paleontology career at the Webb School of California (grades 9-12) in Claremont, California, under noted paleontol ...

and Susan K. Bell suggested the possibility that this family contained up to seven different genera, but documents published since then have shown a high degree of skepticism about the proposal.

Species

The genus ''Gypsonictops'' contains six species:

''Gypsonictops clemensi''

Described by J. K. Rigby and D. L. Wolberg in 1987. It inhabited the planet during the

and

Maastrichtian The Maastrichtian () is, in the ICS geologic timescale, the latest age (uppermost stage) of the Late Cretaceous Epoch or Upper Cretaceous Series, the Cretaceous Period or System, and of the Mesozoic Era or Erathem. It spanned the interv ...

periods. Its description was made from a molar M3 found in

New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejicano, Nuevo Mexicano) , seat = Santa Fe, New Mexico, Santa Fe , LargestCity = Albuquerque, New Mexico, Albuquerque , LargestMetro = Albuquerque metropolitan area, Tiguex , Offi ...

. The name of the species is dedicated to the American

paleontologist Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

William A. Clemens William Alvin Clemens Jr. (May 15, 1932 — November 17, 2020) was a paleontologist at the University of California at Berkeley. He was faculty of the Department of Paleontology from 1967, then the Department of Integrative Biology from 1994 to h ...

''Gypsonictops dormaalensis''

Described by G. E. Quinet in 1964. The name of the species refers to the Belgian population of Dormaal, a city in which there is an important fossil deposit in which fossils of ''G. dormaalensis''.

''Gypsonictops hypoconus''

Described by G. G. Simpson in 1927. It lived during the

and

periods, and fossils have been found in the

Hell Creek Formation The Hell Creek Formation is an intensively studied division of mostly Upper Cretaceous and some lower Paleocene rocks in North America, named for exposures studied along Hell Creek, near Jordan, Montana. The formation stretches over portions of ...

and other sites in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., federal district, five ma ...

. When Simpson created the genus ''Gypsonictops'' to define this species, placed it within the family Leptictidae, which was then part of the Insectivara order, now obsolete. The name of the species refers to its hypocone, the lower cusp of the molar teeth.

''Gypsonictops illuminatus''

Described by J. A. Lillegraven in 1969. It inhabited

Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surf ...

during the

, and fossils have been found in the

, in the

, as well as in various paleontological sites in

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tota ...

''Gypsonictops lewisi''

Described by A. Sahni in 1972. It lived during the

. Fossils of the species have been found in the

Judith River Formation The Judith River Formation is a fossil-bearing geologic formation in Montana, and is part of the Judith River Group. It dates to the Late Cretaceous, between 79 and 75.3 million years ago, corresponding to the "Judithian" land vertebrate age. I ...

Montana Montana () is a U.S. state, state in the Mountain states, Mountain West List of regions of the United States#Census Bureau-designated regions and divisions, division of the Western United States. It is bordered by Idaho to the west, North ...

. ''G. lewisi'' is one of the species with more typical characteristics of the

s of the genus, such as the fusion of a small metaconid with a long protoconid, or a small talonid with two cusps. On the other hand, the

premolar The premolars, also called premolar teeth, or bicuspids, are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant in the permanent set of teeth, making eight premolars total in the mouth ...

es are not as molarized as in other species of the genus. They usually used to weigh over fifty

gram The gram (originally gramme; SI unit symbol g) is a unit of mass in the International System of Units (SI) equal to one one thousandth of a kilogram. Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to ...

s. The species name is dedicated to the

Captain Captain is a title, an appellative for the commanding officer of a military unit; the supreme leader of a navy ship, merchant ship, aeroplane, spacecraft, or other vessel; or the commander of a port, fire or police department, election precinct, e ...

Meriwether Lewis Meriwether Lewis (August 18, 1774 – October 11, 1809) was an American explorer, soldier, politician, and public administrator, best known for his role as the leader of the Lewis and Clark Expedition, also known as the Corps of Discovery, wi ...

, a celebrated American explorer.

''Gypsonictops petersoni''

Described in 1929 by G. G. Simpson, who named the species "Euangelistes petersoni" and wrongly classified it within the

infraclass In biological classification, class ( la, classis) is a taxonomic rank, as well as a taxonomic unit, a taxon, in that rank. It is a group of related taxonomic orders. Other well-known ranks in descending order of size are life, domain, king ...

Marsupialia Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a ...

. It is known with certainty that they inhabited the planet during the

, but it is possible that they could have survived the Cretaceous-Paleogene mass extinction and lived until the

Danian The Danian is the oldest age or lowest stage of the Paleocene Epoch or Series, of the Paleogene Period or System, and of the Cenozoic Era or Erathem. The beginning of the Danian (and the end of the preceding Maastrichtian) is at the Creta ...

. The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of seve ...

of this species is in the

Carnegie Museum of Natural History The Carnegie Museum of Natural History (abbreviated as CMNH) is a natural history museum in the Oakland neighborhood of Pittsburgh, Pennsylvania. It was founded by Pittsburgh-based industrialist Andrew Carnegie in 1896. Housing some 22 million ...

and it is a

that had been badly damaged. Another specimen, preserved at

Yale University Yale University is a Private university, private research university in New Haven, Connecticut. Established in 1701 as the Collegiate School, it is the List of Colonial Colleges, third-oldest institution of higher education in the United Sta ...

, has been described by up to five different names. In case there was not enough controversy on the subject, in 1973,

Clemens Clemens is both a Late Latin masculine given name and a surname meaning "merciful". Notable people with the name include: Surname * Adelaide Clemens (born 1989), Australian actress. * Andrew Clemens (b. 1852 or 1857–1894), American folk artist ...

stated that ''G. petersoni'' was the same species as ''G. hypoconus''.

Bibliography

* * * * *

References

External links

"American Cretaceous Insectivares", by George Gaylord Simpson
{{Authority control Leptictids Prehistoric mammal genera Late Cretaceous mammals of Asia Late Cretaceous mammals of North America Cretaceous mammals of Europe Fossil taxa described in 1927