Kogaionidae is a family of

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

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), fur or ...

within the

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 ...

order

Multituberculata 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, a ...

. Representatives are known from the Upper

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...

and the

Paleocene The Paleocene, ( ) or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), E ...

Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...

. Having started as island endemics on Hateg Island during the Upper Cretaceous, where they were in fact the dominant mammal group and diverged into rather unique ecological niches, they expanded across Europe in the

, where they briefly became a major component of its mammal fauna before their extinction.First mammal species identified from the Upper Cretaceous of the Rusca Montana Basin (Transylvania, Romania) Article in Comptes Rendus Palevol https://dx.doi.org/10.1016/j.crpv.2016.04.002 · June 2016 They are considered to be basal members of

Cimolodonta Cimolodonta is a taxon of extinct mammals that lived from the Cretaceous to the Eocene. They were some of the more derived members of the extinct order Multituberculata. They probably lived something of a rodent-like existence until their ecolo ...

Classification

This family is part of the

suborder Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...

, generally accepted as closely related to

Taeniolabidoidea Taeniolabidoidea is a group of extinct mammals known from North America and Asia. They were the largest members of the extinct order Multituberculata, as well as the largest non-therian mammals. '' Lambdopsalis'' even provides direct fossil evide ...

.Thierry Smith, Codrea Vlad, Red Iron-Pigmented Tooth Enamel in a Multituberculate Mammal from the Late Cretaceous Transylvanian " Haţeg Island ", Article in PLoS ONE 10(7):e0132550-1-16 · July 2015 These small multituberculates were named by Rădulescu R. and Samson P. in 1996, who stated they :"Share with

the general shape of the skull, with anterior part of

zygomatic arch In anatomy, the zygomatic arch, or cheek bone, is a part of the skull formed by the zygomatic process of the temporal bone (a bone extending forward from the side of the skull, over the opening of the ear) and the temporal process of the zygomati ...

es directed roughly transversely and very short basicranial region, which gives the skull a square-like appearance, but differ from them in having a strongly elongated snout and different dentition," (Kielan-Jaworowska & Hurum 2001, p.418). Recent studies have favoured a position close to

. A 2021 study found them to be the amongst the most basal members of Cimolodonta, more derived only than ''

Bryceomys ''Bryceomys'' is an extinct mammal that lived during the late Cretaceous period (between 100 and 66 million years ago) and thus shared the world with dinosaurs. It was a member of the also extinct order of Multituberculata. It was within the sub ...

'', and they probably originated from an eobaatarid-like ancestor.

Biology

Like some modern

rodents Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are nat ...

and

shrews Shrews (family Soricidae) are small mole-like mammals classified in the order Eulipotyphla. True shrews are not to be confused with treeshrews, otter shrews, elephant shrews, West Indies shrews, or marsupial shrews, which belong to different ...

, at least some kogaionids had red, iron-pigmented enamel. In ''

Barbatodon ''Barbatodon'' is a mammal genus from the Upper Cretaceous period. It lived in Transylvania at the same time as some of the last dinosaurs and was a member of the extinct order of Multituberculata. It is within the suborder of Cimolodonta, and t ...

'' this distribution is more similar to that seen in shrews as opposed to the condition seen in rodents, and suggests

insectivore A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores wer ...

habits. This is a unique evolutionary route taken in the isolation of their island environment, almost entirely deprived of competing mammals, and inadvertently resulted in their survival across the KT event. In '' Litovoi tholocephalos'', there was an extreme brain size reduction, displaying one of the smallest brains in proportion to body size of any derived mammal. Additionally, it bore a small dome in its head, like a

pachycephalosaur Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachyc ...

Range

Kogaionids first appear as island endemics on

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 interval from ...

Romania Romania ( ; ro, România ) is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern, and Southeast Europe, Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, S ...

, then isolated from the rest of

. They are in fact the only European multituberculates from the Late Cretaceous, in contrast to the Early Cretaceous' massive multituberculate diversity in

Britain Britain most often refers to: * The United Kingdom, a sovereign state in Europe comprising the island of Great Britain, the north-eastern part of the island of Ireland and many smaller islands * Great Britain, the largest island in the United King ...

and the

Iberian Peninsula The Iberian Peninsula (), ** * Aragonese and Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, defi ...

. A supposed kogaionid is also known from 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. Campanian s ...

Appalachia Appalachia () is a cultural region in the Eastern United States that stretches from the Southern Tier of New York State to northern Alabama and Georgia. While the Appalachian Mountains stretch from Belle Isle in Newfoundland and Labrador, Ca ...

, but its identity as a kogaionid is ambiguous and rather unlikely considering the otherwise Hateg Island-restricted range.Paleobiogeographical implications of the fossil mammals from the Maastrichtian of the Hateg Basin Article · January 2002 Perhaps due to their insectivorous habits, kogaionids managed to survive the KT event. During the

Hateg Island connected to the rest of Europe, and so these multituberculates dispersed; fossils are known in

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

and

Belgium Belgium, ; french: Belgique ; german: Belgien officially the Kingdom of Belgium, is a country in Northwestern Europe. The country is bordered by the Netherlands to the north, Germany to the east, Luxembourg to the southeast, France to th ...

, beside Romania's Paleocene deposits at Jisou. For a brief period of time these were among the most common mammals in Europe, but by the Late Paleocene the arrival of other multituberculate groups from North America brought a quick decline, culminating in its extinction at the PETM.

References

* Rădulescu and Samson (1996), "The first multituberculate skull from the Late Cretaceous (Maastrichtian) of Europe (Hateg Basin, Romania)". ''Anuarul Institutului de Geologie al României, Supplement 1'' 69, p. 177-178. * Kielan-Jaworowska Z & Hurum JH (2001), "Phylogeny and Systematics of multituberculate mammals". ''Paleontology'' 44, p. 389-429. * Much of this information has been derived fro

MESOZOIC MAMMALS: "basal"

Cimolomyidae Cimolomyidae is a family of fossil mammal within the extinct order Multituberculata. Representatives are known from the Upper Cretaceous and the Paleocene of North America and perhaps Mongolia. The family is part of the suborder Cimolodonta. Oth ...

, Boffiidae and Kogaionidae, an Internet directory. {{Taxonbar, from=Q6425752 Cimolodonts Cretaceous mammals of Europe Paleogene mammals of Europe Paleocene mammals Maastrichtian first appearances Paleocene extinctions Prehistoric mammal families