Multituberculata

Skull of Taeniolabis

• Eurasia, North America

The Multituberculata are a group of extinct mammals, which did parallels to the rodents in their dimensions, their diversity and their presumed life. They appeared in the middle Jurassic period ( about 165 million years ago) and had its heyday in the Cretaceous and Paleocene in - that survived the extinction of the dinosaurs, and are at the end of the Eocene extinct (before about 34 million years ago). They are more closely related to any group of mammals today, but represent a specialized side branch

• 3.1 phylogeny
• 3.2 External systematics

• 4.1 Plagiaulacida 4.1.1 incertae sedis Plagiaulacida
• 4.1.2 Allodontid - line
• 4.1.3 Paulchoffatiid - line
• 4.1.4 Plagiaulacid - line

• 4.2.1 Basal Cimolodonta
• 4.2.2 incertae sedis Cimolodonta
• 4.2.3 Ptilodontoidea
• 4.2.4 Djadochtatherioidea
• 4.2.5 Taeniolabioidea

• 5.1 Literature
• 5.2 External links
• 5.3 References

Physique

Multituberculata were consistently small animals. The most varied in extent between a small mouse and a rat and even the greatest representatives who Taeniolabidae reached only the size of a marmot (up to 60 cm in length).

Head and teeth

The head was built broad, the snout short and blunt, and the eyes were positioned laterally. The most striking feature were the teeth. In the mandible, these animals had only one pair of incisors, which was enlarged and protruded forward, maxillary incisors were one to three per half of the jaw exist. As with rodents only the front of the incisors was partially covered with enamel and the teeth were sharpened by mutual abrasion. For a nagging work best if the lower incisors were suitable, although they are not as effective as the rodents were safe.

Between cutting and molars is a gap ( diastema ). The canines were missing most, only the species urtümlicheren an upper canine was still present. The lower premolars showed jagged, sharp cusps that worked against the provided with many humps upper premolars. Only two molars were present per half of the jaw, they had two ( in some younger species also three) rows of up to eight consecutively arranged protuberances ( tubercles ). This many bumps owe the animals also the name Multituberculata. When chewed, the hump and the valleys of the opposing teeth inserted into one another and thus ensured for effective Mahltätigkeit.

The mandible was large and must have been moved by powerful muscles of mastication. A sideways movement of the mandible has not been possible, the food was instead crushed by a powerful pre-and -back movement.

Other Body Type

As with many fossil mammals only teeth or parts of the skull are often handed down now but also some completely preserved skeletons have been found. In the construction of the narrow shoulder shoulder blade is characteristic of the coracoid is reduced as in the Theria, but is like the monotremes a interclavicle ("Interim clavicle " ) available. The basin has marsupial bones, which is likely to be an original mammalian feature.

Multituberculata are among the few fossil mammals in which hairs were detected. In fossil coprolites remains were discovered by Lambdopsalis that clearly showed traces of fur.

Investigations of the cranial cavity of different species showed that the brain was considerably smaller than the present-day mammals of comparable size. The olfactory bulb, however, was well developed.

Way of life

A lot about the lifestyle of these extinct animals of course remains speculative. From the structure of the brain suggests that the sense of smell was well developed, which could speak for a nocturnal lifestyle policy.

The aforementioned analogy to rodents demonstrated by the fact that these animals inhabited a variety of habitats and developed different ways of moving. In Ptilodus very flexible feet and probably a prehensile tail can be seen, indicating an arboreal lifestyle. Bulganbaatar in turn had arranged under the body and limbs should have been a fast runner in a dry habitat. In Nemegtbaatar it can be assumed that the genus in a jumping manner - has moved - possibly similar to gerbils. Lambdopsalis had a broad, flat skull and massive humerus, which perhaps could speak for a grave lifestyle similar to moles. The majority of the genera is only through skull or teeth finds known so that the Multituberculata probably had an even greater variety of ways of moving and habitats than previously known.

The food of Multituberculata is not entirely clear. Some of them have fed on plant material such as seeds and tubers, is controversial to what extent they also took small animals to him. Probably some representatives were omnivores who supplemented their diet with insects, worms and other invertebrates, while other species may have been herbivores.

A pelvic examination revealed the speculative conclusion that Multituberculata have brought to live young. The narrowness of the birth canal ( 3.4 millimeters at Kryptobaatar ) were too small for eggs, the newborn could therefore have been comparable in size with newborn bag mammals.

Phylogeny and systematics exterior

Phylogeny

The oldest finds of Multituberculata come from the Middle Jurassic and are around 165 million years old. The animals soon spread across Laurasia (present-day Eurasia and North America) from, but they never came to Gondwana. ( Finds from South America are today considered as a separate group, Gondwanatheria. ) In the Cretaceous, they developed further. According to both the individuals as well as by the number of species they represent the most common group of mammals of this period, up to 75 % of all mammals found the Upper Cretaceous are Multituberculata. Although some groups like the Djadochtatherioidea probably died out at the end of the Cretaceous, Paleocene in they make but still a considerable part of the mammalian fauna.

The decline of this group in the Eocene and their extinction at the end of this period ( around 34 million years ago ) is expected with the development and global distribution of rodents are related, occupy similar ecological niches. The exact reasons for the extinction of the Multituberculata are unclear, possibly the rodents were superior to them in the construction of the locomotor and masticatory apparatus.

Nevertheless, the Multituberculata existed for about 130 million years, and thus represent one of the longest-lived mammal selcetion ever

Outer systematics

In what way the Multituberculata are related to other mammal groups, is still controversial. One theory sees them as descendants of the Haramiyida, an early mammal group is known almost exclusively by dental findings. Although indicate similarities in the structure of teeth on this relationship back - the common taxon is called Allotheria and possibly also includes the Gondwanatheria. In the construction of the jaw Multituberculata the show but in common with other mammals, which speaks against this descent. Another theory sees the Multituberculata close relatives of the monotremes. This view is supported by similarities in the structure of the skull and the ear, but other features contradict, so this is a minority opinion.

A third theory, it represents a close relative of the Trechnotheria, a taxon, in addition to some extinct relatives also includes today's Theria. Thus, the Multituberculata are closer to the bag and Higher mammals used as these with the monotremes. A detailed cladistic analysis looks a bit more support for this than for the Allotheria theory, but the difference is hardly significant. The question of the origin of the Multituberculata can not be answered thus at the present time.

Inside systematics

The most comprehensive study of the inner scheme of Multituberculata comes from Zofia Kielan - Jaworowska Jørn H. Hurum and from the year 2001. They differed two groups urtümlicheren Plagiaulacida that lived from the Middle Jurassic to the Middle Cretaceous, and the more developed Cimolodonta, the existed from the Lower Cretaceous to the end of the Eocene.

Plagiaulacida

The Plagiaulacida are the older of the two and urtümlichere subtaxa. Since the Cimolodonta have developed from them, they are paraphyletic. The representatives of this group are in the construction of their teeth are not as sophisticated as the later species. They can be divided into three lines of development, the Allodontid - line Paulchoffatiid line and the Plagiaulacid line to which some discovered recently, not been einordbare genres come.

Incertae sedis Plagiaulacida

These genera are incertae sedis, that is their systematic classification is unclear.

• Hahnotherium and Kermackodon are known only by the molars, which were found in 2005 in England. They originate from the Middle Jurassic and are the oldest known representative of the Multituberculata.
• Ameribaatar and Janumys were discovered in the Middle Cretaceous of North America and Utaher be dated to the mid-Cretaceous time. Your assignment is controversial, they may also belong to the Cimolodonta.

Allodontid - line

The types of Allodontid - line have a primitive construction of the teeth ( five upper and four lower premolars, small third incisors ) and are among the oldest known better Multituberculata. So far, individual teeth and jaw and skull bones were found. All representatives are from the Upper Jurassic and were found in North America. You share in the family of Allodontidae ( Ctenacodon, Morrisodon and Psalodon ) and in the isolated genera Glirodon and Zofiabataar.

Paulchoffatiid - line

The types of Paulchoffatiid - line are also characterized by a primitive Zahnbau. You have maxillary canine and even a five premolars, and the enamel of the incisors is not prismatic. In addition to teeth and jaw parts little about them is known. Representatives of this group were spread from the Middle Jurassic to the Early Cretaceous, finds are known from Western Europe and North Africa. Three families can be distinguished:

• The Hahnodontidae ( genera Denisodon and Hahnodon ) lived in the Lower Cretaceous, the findings are from North Africa ( Morocco), making them the single previously known African Multituberculata.
• The Paulchoffatiidae are named in honor of the geologist Paul Choffat, they are from the Middle Jurassic to the Lower Cretaceous of western Europe ( Iberian Peninsula and England). Known. They include the genera Bathmochoffatia, Galveodon, Guimarotodon, Henkelodon, Kielanodon, Kuehneodon, Meketibolodon, Meketichoffatia, Paulchoffatia, Plesiochoffatia, Pseudobolodon, Sunnyodon and Xenachoffatia.
• The Pinheirodontidae are mainly from dental findings known to have been made on the Iberian Peninsula and in England and which are dated to the Early Cretaceous. The family includes the genera Bernardodon, Ecprepaulax, Gerhardodon, Iberodon and Lavocatia,

Plagiaulacid - line

The representatives of the Plagiaulacid line were common from the upper Jurassic to the Lower Cretaceous and lived in North America and Eurasia. At least the lower canine tooth was lost and the number of premolars reduced. Probably have the later Multituberculata that Cimolodonta, developed from this group. Four families can be distinguished:

• The Plagiaulacidae are known from the Upper Jurassic of North America and the Lower Cretaceous of England and include the genera Bolodon, Parabolodon and Plagiaulax.
• The Albionbaataridae ( genera Albionbaatar and Proalbionbaatar ) are known only by individual teeth from the Upper Jurassic and Lower Cretaceous of Western Europe and possibly also from East Asia.
• The Eobataaridae ( genera Eobaatar, Loxaulax, Monobaatar, Parendotherium and Sinobaatar ) lived in the Lower Cretaceous and are known from Western Europe and East Asia. From Sinobaatar also the body is known. It was a shrew large animal with five-toed feet, which was still little specialized compared to later Multituberculata.
• Arginbaatar is in one 's own family, Arginbaataridae, like. The genus is known only by individual teeth, which reveal a transitional stage between the Plagiaulacida and Cimolodonta and complicate the systematic classification. The genus lived in the Lower Cretaceous of Mongolia.

Cimolodonta

The advanced Multituberculata be summarized as Cimolodonta. You are probably a monophyletic group that evolved from an ancestor from the Plagiaulacid line. They appear in the Lower Cretaceous, had their heyday in the Upper Cretaceous and Paleocene and are probably extinct at the end of the Eocene. Cimolodonta are known from North America and Eurasia. They can be in a basal group, three superfamilies ( Ptilodontoidea, Djadochtatherioidea and Taeniolabioidea ) and several families of uncertain affiliation divided.

Basal Cimolodonta

The most primitive representatives of Cimolodonta are summarized in the so-called Paracimexomys group. It is not a natural group, as have presumably developed several lines of them. Were mouse large animals whose weight is estimated to be 20 to 100 grams. Finds the genus Cimexomys been made in dinosaur nests (of Maiasaura ) - if that allows conclusions to their diet is controversial. These animals are occupied by the Lower Cretaceous to Paleocene in the and mostly come from North America. To Paracimexomys group the genera Bryceomys, Cedaromys, Cimexomys, Dakotamys and Paracimexomys be. The systematic position of the genus Uzbekbaatar ( Upper Cretaceous of Central Asia ) and Viridomys ( Upper Cretaceous of North America ) is still unclear.

Incertae sedis Cimolodonta

Several families of Cimolodonta are listed as incertae sedis, meaning that their systematic affiliation is disputed.

• The Cimolomyidae ( genera Buginbaatar, Cimolomys, Essonodon, Meniscoessus ) are known from the Upper Cretaceous of North America and Asia. There were relatively large, externally believed to be rat -like animals that could reach a weight of 0.3 to 3 kilograms and thus were among the largest mammals in the Cretaceous period.
• The Boffiidae consist of only one genus, Boffius, which is known from the lower Paleocene of Belgium, and was also relatively large. Maybe it was related to the Cimolomyidae.
• The Kogaionidae ( genera Barbatodon, Hainina and Kogaionon ) are known only by a few finds from Europe. They lived on the Upper Cretaceous to Paleocene in the and were very small animals, which were characterized by an elongated snout.
• The Eucosmodontidae ( genera Clemensodon, Eucosmodon, Stygimys ) lived from the Upper Cretaceous to Paleocene in the primarily in North America. They are known only by relatively few jaw and tooth fossils and isolated cranial bones. They may have been related to the Djadochtatherioidea.
• The Microcosmodontidae ( genera Acheronodon, Microcosmodon and Pentacosmodon ) resembled the Eucosmodontidae, but were much smaller. Findings of this group are known from the Upper Cretaceous and Paleocene of North America, unsafe finds there are also from Europe.

Ptilodontoidea

The Ptilodontoidea were a group of Multituberculata, which had its heyday in the Upper Cretaceous and Paleocene and is known almost exclusively in North America. The eponymous genus Ptilodus had a prehensile tail and probably lived in trees, to what extent this is true also for the other representatives, is not known. The Ptilodontoidea can be divided into an isolated genus and three families:

• Neoliotomus was an estimated 2 kilograms relatively large, the genus lived in the Paleocene and Eocene in North America.
• The Neoplagiaulacidae are a relatively sparse findings by (mostly jaws and teeth ) narrated group. Characteristic of them was the narrow, forwardly projecting lower incisor. The group was formed in the Upper Cretaceous and lasted until the end of the Eocene (perhaps even to the early Oligocene ), so it represents one of the youngest families of Multituberculata. To this family the genera Cernaysia, Ectypodus, Fractinus, Krauseia, Mesodma, Mesodmops, Mimetodon, Neoplagiaulax, Parectypodus, Xanclomys and Xironomys be counted.
• The Ptilodontidae are limited to North America group, which appeared in the Upper Cretaceous, had its heyday in the Paleocene and Eocene became extinct at the bottom. The best known representative is Ptilodus, which is known also the physique. It was 30 to 50 inches long, the limbs were very mobile and remember the the tree squirrels and the tail was designed as a prehensile tail. All this speaks for arboreal life. Other less completely preserved genera of this group are Baiotomeus, Kimbetohia and Prochetodon.
• The Cimolodontidae ( genera Anconodon, Cimolodon and Liotomus ) are primarily known by teeth similar to those of Ptilodontidae. Representatives of this group are known from the Upper Cretaceous and Paleocene of North America and Europe.

Djadochtatherioidea

The Djadochtatherioidea are only from the Upper Cretaceous of Asia known (primarily from Mongolia ). Some of the best preserved fossils of Multituberculata come from this group that a terrestrial ( ground-dwelling ) led lifestyle in contrast to the arboreal Ptilodontoidea. This group is divided into three isolated genera and two families:

• Bulganbaatar is completely preserved. Investigations of the skeleton indicate that the legs under the body were placed and the animal was probably adapted for fast running on the floor.
• Nemegtbaatar is also known nearly complete and was relatively large. His physique shows evidence that the genre in a jumping manner - has moved - possibly similar to gerbils.
• Chulsanbaatar is also obtained by complete skeletons. This genus was remarkably small in comparison to other Djadochtatherioidea.
• The Sloanbaataridae ( genera Kamptobaatar, Nessovbaatar and Sloanbaatar ) were relatively small representative of the Djadochtatherioidea. They are named after the paleontologist Robert Evan Sloan.
• The Djadochtatheriidae were also rather small, in the upper Cretaceous widespread animals. For Kryptobaatar, one of the most studied Multituberculata, a length of 13.5 inches and a weight estimate of 40 to 80 grams is indicated. Other genera of this family was Catopsbaatar, Djadochtatherium and Tombaatar.

Taeniolabioidea

The Taeniolabioidea include only one family the Taeniolabidae. They were spread from the Upper Cretaceous to the end of the Paleocene in North America and Asia. These animals are characterized by a blunt muzzle and a square skull. This group includes the largest Multituberculata, they reached the size of a beaver ( body length about 60 inches, estimated weight 25 to 30 kg). Genera of this group are Catopsalis, Lambdopsalis, Prionessus, Sphenopsalis and Taeniolabis. The genus Lambdopsalis is interesting for two reasons: on the one hand traces of a fur were found in their fossil, which is unusual for mammals of this age. On the other hand, the broad, stocky humerus may indicate a grave end, the moles similar lifestyle.

Note on naming

Many generic names ending in- baatar. This is the Mongolian word for " hero " and finds himself about in the name of Ulan Bator ( Ulaanbaatar mongol. ). This naming is originally derived from the fact that many complete skeletons have been found in Mongolia; now this fashion but is also applied to findings from other continents (about Ameribaatar from America or Albionbaatar from the UK ).

Swell