Guimarotodon is an extinct mammal

Mammal

Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...

 of the Upper Jurassic

Jurassic

The Jurassic is a geologic period and system that extends from about Mya to  Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...

. It was a relatively early member of the also extinct order

Order (biology)

In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...

 of Multituberculata

Multituberculata

The Multituberculata were a group of rodent-like mammals that existed for approximately one hundred and twenty million years—the longest fossil history of any mammal lineage—but were eventually outcompeted by rodents, becoming extinct during the early Oligocene. At least 200 species are...

. It made its living nibbling plants as great big, and small, dinosaur

Dinosaur

Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...

s roamed the world. (For the technically minded, suborder Plagiaulacida

Plagiaulacida

Plagiaulacida is a group of extinct multituberculate mammals. Multituberculates were among the most common mammals of the Mesozoic, "the age of the dinosaurs"...

, family Paulchoffatiidae

Paulchoffatiidae

Paulchoffatiidae is a family of extinct mammals that lived predominantly during the Upper Jurassic period, though a couple of genera are known from the earliest Cretaceous. Some undescribed fossils from the Middle Jurassic of England may represent earlier versions. Remains have been reported from...

.)

Guimarotodon ("Guimarota tooth") Hahn G, 1969. "Guimarotodon Hahn 1969 exhibits a more slender Corpus mandibulae than either Paulchoffatia

Paulchoffatia

Paulchoffatia is a genus of extinct mammal of the Upper Jurassic - Lower Cretaceous. It was a relatively early member of the also extinct order Multituberculata, within the suborder "Plagiaulacida" and family Paulchoffatiidae. It lived in Europe during the "age of the dinosaurs."The genus...

or Meketibolodon

Meketibolodon

Meketibolodon is a genus of extinct mammal from the Kimmeridgian Camadas de Guimarota of Guimarota, Portugal. It was a relatively early member of the also extinct order Multituberculata, suborder Plagiaulacida, family Paulchoffatiidae. The genus was named by Hahn G...

. The most conspicuous character of this genus is the morphology of the P3-4 and the M1.". The Corpus mandibulae is the part of the jaw below the tooth row. P3-4 are upper premolar

Premolar

The premolar teeth or bicuspids are transitional teeth located between the canine and molar teeth. In humans, there are two premolars per quadrant, making eight premolars total in the mouth. They have at least two cusps. Premolars can be considered as a 'transitional tooth' during chewing, or...

s, whilst M1 is an upper molar

Molar (tooth)

Molars are the rearmost and most complicated kind of tooth in most mammals. In many mammals they grind food; hence the Latin name mola, "millstone"....

 tooth.

"The incisor

Incisor

Incisors are the first kind of tooth in heterodont mammals. They are located in the premaxilla above and mandible below.-Function:...

 is relatively little curved and its root is of similar length as that of Meketibolodon and extends to underneath the posterior premolars." (Both quotations from Hahn & Hahn 2000, p. 105-106).

Guimarotodon leiriensis

Guimarotodon leiriensis is found in Kimmeridgian (Upper Jurassic) of Guimarota, Portugal. Classification is based on three lower jaws. The species name refers to the local town of Leiria

Leiria

Leiria is a city in Leiria Municipality in the Centro Region, Portugal. It is the capital of Leiria District. The city proper has 50,200 inhabitants and the entire municipality has nearly 120,000...

.