Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct taxon of rodent-like allotherianmammals that existed for approximately 166 million years, the longest fossil history of any mammal lineage. They eventually declined from the late Palaeocene onwards, disappearing in the late Eocene, though they might have lived even longer into the Miocene, if gondwanatheres are part of this group. More than 200 species are known, ranging from mouse-sized to beaver-sized. These species occupied a diversity of ecological niches, ranging from burrow-dwelling to squirrel-like arborealism to jerboa-like hoppers. Multituberculates are usually placed as crown mammals outside either of the two main groups of living mammals—Theria, including placentals and marsupials, and Monotremata—but closer to Theria than to monotremes.
Restoration of Taeniolabis, the largest multituberculate at approximately 100 kg.
The multituberculates had a cranial and dental anatomy superficially similar to rodents such as mice and rats, with cheek-teeth separated from the chisel-like front teeth by a wide tooth-less gap (the diasteme). Each cheek-tooth displayed several rows of small cusps (or tubercles, hence the name) that operated against similar rows in the teeth of the jaw; the exact homology of these cusps to therian ones is still a matter of debate. Unlike rodents, which have ever-growing teeth, multituberculates underwent dental replacement patterns typical to most mammals (though in at least some species the lower incisors continued to erupt long after the root's closure). Multituberculates are notable for the presence of a massive fourth lower premolar, the plagiaulacoid; other mammals, like Plesiadapiformes and diprotodontianmarsupials, also have similar premolars in both upper and lower jaws, but in multituberculates this tooth is massive and the upper premolars aren't modified this way. In basal multituberculates all three lower premolars were plagiaulacoids, increasing in size posteriorly, but in Cimolodonta only the fourth lower premolar remained, with the third one remaining only as a vestigial peg-like tooth, and in several taxa like gondwanatherians and taeniolabidoideans the plagiaulacoid disappeared entirely or was reconverted into a molariform tooth.
Skull of Ptilodus. Notice the massive blade-like lower premolar.
Unlike rodents and similar therians, multituberculates had a palinal jaw stroke (front-to-back), instead of a propalinal (back-to-front) or transverse (side-to-side) one; as a consequence, their jaw musculature and cusp orientation is radically different. Palinal jaw strokes are almost entirely absent in modern mammals (with the possible exception of the dugong), but are also present in haramiyidans, argyrolagoideans and tritylodontids, the former historically united with multituberculates on that basis. Multituberculate mastication is thought to have operated in a two stroke cycle: first, food held in place by the last upper premolar was sliced by the bladelike lower pre-molars as the dentary moved orthally (upward). Then the lower jaw moved palinally, grinding the food between the molar cusp rows.
Lower jaws and teeth of allodontid multituberculates
The structure of the pelvis in the Multituberculata suggests that they gave birth to tiny helpless, underdeveloped young, similar to modern marsupials, such as kangaroos.
Multituberculates first appear in the fossil record during the Jurassic era, and then survived and even dominated for over one hundred million years, longer than any other order of mammaliforms, including placental mammals. The earliest known example is Rugosodon, a rodent-like omnivore living 160 million years ago in what would someday be China.
During the Cretaceous, the multituberculates radiated into a wide variety of morphotypes, including the squirrel-like arboreal ptilodonts. Like all categories of life on earth, most species of multituberculata appear to have been wiped out during the K-T event (the extinction of the dinosaurs), but they seem to have been among the first to recover and diversify again. The peculiar shape of their last lower premolar is their most outstanding feature. These teeth were larger and more elongated than the other cheek-teeth and had an occlusive surface forming a serrated slicing blade. Though it can be assumed that this was used for crushing seeds and nuts, it is believed that most small multituberculates also supplemented their diet with insects, worms, and fruits. Tooth marks attributed to multituberculates are known on Champsosaurus fossils, indicating that at least some of these mammals were scavengers.
A ptilodont that throve in North America was Ptilodus. Thanks to the well-preserved Ptilodus specimens found in the Bighorn Basin, Wyoming, we know that these multituberculates were able to abduct and adduct their big toes, and thus that their foot mobility was similar to that of modern squirrels, which descend trees head first.
In Europe, another family of multituberculates were equally successful—the Kogaionidae, first discovered in Haţeg, Romania. They also developed an enlarged blade-like lower premolar. The Hainina, the most successful genus, was originally believed to be a ptilodont. However, more detailed analysis of this genus revealed a smaller number of dental cusps and a retained fifth premolar—a unique combination of primitive and advanced features indicating that Hainina were related to some Jurassic genera and that enlarged, blade-like premolars were acquired independently in Europe and North America.
Another group of multituberculates, the taeniolabids, were heavier and more massively built, indicating that they lived a fully terrestrial life. The largest specimens weighted probably as much as 100 kg, making them comparable in size to large rodents like Castoroides.
They reached their highest diversity in Asia during the late Cretaceous and Paleocene, which suggests that they originated from there.
About 80 genera of Multituberculata are known, including Lambdopsalis, Ptilodus and Meniscoessus. In the northern hemisphere, during the late Cretaceous, more than half of typical land mammalian species were multituberculates. While most mammals — along with birds and other dinosaurs and most other types of life — were wiped out during the K-T event (the extinction of the dinosaurs 65 million years ago), a large proportion of the mammals that show up in the fossil record after the extinction are multituberculates.
The group went on to dominate land in the next twenty million years of the paleocene, but it appears that increasing competition from placental mammals drove them to extinction by the end of the eocene, about 40 million years ago.
Multituberculate phylogenetic tree based off L. Xu, X. Zhang, H. Pu, S. Jia, and J. Zhang, J., and J. Meng. 2015. Largest known Mesozoic multituberculate from Eurasia and implications for multituberculate evolution and biology. Scientific Reports 5(14950):1-11 and Nicolás R. Chimento, Federico L. Agnolin and Fernando E. Novas (2015). "The bizarre 'metatherians' Groeberia and Patagonia, late surviving members of gondwanatherian mammals". Historical Biology: An International Journal of Paleobiology. 27 (5): 603–623. doi:10.1080/08912963.2014.903945.
Based on the combined works of Mikko's Phylogeny Archive and Paleofile.com.
Species †K. gobiensis Kielan-Jaworowska, 1970 [Gobibaatar parvus Kielan-Jaworowska, 1970 ]
The multituberculates existed for about 166 or 183 million years, and are often considered the most successful, diversified, and long-lasting mammals in natural history. They first appeared in the Jurassic, or perhaps even the Triassic, survived the mass extinction in the Cretaceous, and became extinct in the early Oligoceneepoch, some 35 million years ago. The oldest known species in the group is Indobaatar zofiae from the Jurassic of India, some 183 million years ago, and the youngest are two species, Ectypodus lovei and an unnamed possible neoplagiaulacid, from the late Eocene/Oligocene Medicine Pole Hills deposits of North Dakota. If gondwanatheres are multituberculates, then the clade might have survived even longer into the ColhuehuapianMiocene in South America, in the form of Patagonia peregrina.
The extinction of multituberculates has been a topic of controversy for several decades. After at least 88 million years of dominance over most mammalian assemblies, multituberculates reached the peak of their diversity in the early Palaeocene, before gradually declining across the final stages of the epoch and the Eocene, finally disappearing in the early Oligocene (mid-Miocene if gondwanatherians are multituberculates). Traditionally, the extinction of multituberculates has been linked to the rise of rodents (and, to a lesser degree, earlier placental competitors like hyopsodonts and Plesiadapiformes), which supposedly competitively excluded multituberculates from most mammalian faunas.
However, the idea that multituberculates were replaced by rodents and other placentals has been criticised by several authors. For one thing, it relies on the assumption that these mammals are "inferior" to more derived placentals, and ignores the fact that rodents and multituberculates had co-existed for at least 15 million years. According to some researchers, multituberculate "decline" is shaped by sharp extinction events, most notably after the Tiffanian, where a sudden drop in diversity occurs. Finally, the youngest known multituberculates do not exemplify patterns of competitive exclusion; the Oligocene Ectypodus is a rather generalistic species, rather than a specialist. This combination of factors suggests that, rather than gradually declining due to pressure from rodents and similar placentals, multituberculates simply could not cope with climatic and vegetation changes, as well as the rise of new predatory eutherians, such as miacids.
More recent studies show a mixed effect. Multituberculate faunas in North America and Europe do indeed decline in correlation to the introduction of rodents in these areas. However, Asian multituberculate faunas co-existed with rodents with minimal extinction events, implying that competition was not the main cause for the extinction of Asiatic multituberculates. As a whole, it seems that Asian multituberculates, unlike North American and European species, never recovered from the KT event, which allowed the evolution and propagation of rodents in the first place. A recent study seems to indeed indicate that eutherians recovered more quickly from the KT event than multituberculates.
Multituberculates are mostly known from the northern continents (Laurasia), but there are various records from the southern continents (Gondwana). The group Gondwanatheria, known from Argentina, Antarctica, Madagascar, India, and possibly Tanzania, has been referred to the order in the past and, while this placement remains controversial, most recent phylogenetic studies recover them as multituberculates outside but close to Cimolodonta. Two genera, Hahnodon and Denisodon, are known from the Early Cretaceous of Morocco, but they may instead be haramiyidans. Multituberculates have also been recorded from the Late Cretaceous of Madagascar and Argentina. An Australian multituberculate, Corriebaatar, is known from a single tooth.Indobaatar is known from the Kota Formation of India - then part of eastern Gondwanna - and is the oldest known multituberculate.
In the late Cretaceous, multituberculates were widespread and diverse in the northern hemisphere, and possibly across most southern landsmasses as well, making up more than half of the mammal species of typical faunas. Although several lineages became extinct during the faunal turnover at the end of the Cretaceous, multituberculates as a whole managed very successfully to cross the Cretaceous–Paleogene boundary and reached their peak of diversity during the Paleocene. They were an important component of nearly all Paleocene faunas of Europe and North America, and of some late Paleocene faunas of Asia. Multituberculates were also most diverse in size during the Paleocene, ranging from the size of a very small mouse to that of a panda. However, in Asia, Palaeocene and Eocene multituberculates compose a very small percentage of the overall local mammalian fauna, having never managed to recover from the KT event in the same way that their North American and European counterparts did. Gondwanatheres are common in the Late Cretaceous of Madagascar and India, the Paleocene and Eocene of Seymour Island, and occur in South America from the Late Cretaceous to the Miocene.
^ abKrause, David W.; Hoffmann, Simone; Wible, John R.; Kirk, E. Christopher; Schultz, Julia A.; von Koenigswald, Wighart; Groenke, Joseph R.; Rossie, James B. (2014-11-05). O'Connor, Patrick M., Seiffert, Erik R., Dumont, Elizabeth R., Holloway, Waymon L., Rogers, Raymond R., Rahantarisoa, Lydia J., Kemp, Addison D., Andriamialison, Haingoson. "First cranial remains of a gondwanatherian mammal reveal remarkable mosaicism". Nature. 515: 512–517. doi:10.1038/nature13922. ISSN1476-4687. PMID25383528.
^ abcNicolás R. Chimento, Federico L. Agnolin and Fernando E. Novas (2015). "The bizarre 'metatherians' Groeberia and Patagonia, late surviving members of gondwanatherian mammals". Historical Biology: An International Journal of Paleobiology. 27 (5): 603–623. doi:10.1080/08912963.2014.903945.
^ abKrause, David W. (1986). "Competitive exclusion and taxonomic displacement in the fossil record; the case of rodents and multituberculates in North America". Rocky Mountain Geology. 24 (special issue 3): 95–117. doi:10.2113/gsrocky.24.special_paper_3.95.
^Gurovich (2005). "p. 334; Gurovich & Beck 2009, pp. 31–32; Rougier". et al. 2009: 233.
^J. M. Lanyon & G. D. Sanson, Degenerate dentition of the dugong (Dugong dugon), or why a grazer does not need teeth: morphology, occlusion and wear of mouthparts, Received 26 May 2004; accepted 24 April 2005
^Williamson, Thomas E.; Brusatte, Stephen L.; Secord, Ross; Shelley, Sarah (2015). "A new taeniolabidoid multituberculate (Mammalia) from the middle Puercan of the Nacimiento Formation, New Mexico, and a revision of taeniolabidoid systematics and phylogeny". Zoological Journal of the Linnean Society. doi:10.1111/zoj.12336.
^Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates, First published: 16 June 2010 + DOI: 10.1111/j.1475-4983.2010.00957.x
^Williamson, Thomas E.; Brusatte, Stephen L.; Secord, Ross; Shelley, Sarah (2015). "A new taeniolabidoid multituberculate (Mammalia) from the middle Puercan of the Nacimiento Formation, New Mexico, and a revision of taeniolabidoid systematics and phylogeny". Zoological Journal of the Linnean Society. doi:10.1111/zoj.12336. Taeniolabidoids underwent a modest taxonomic radiation during the early Palaeocene of North America and underwent a dramatic increase in body size, with Taeniolabis taoensis possibly exceeding 100 kg
^Mathias M. Pires; Brian D. Rankin; Daniele Silvestro; Tiago B. Quental (2018). "Diversification dynamics of mammalian clades during the K–Pg mass extinction". Biology Letters. 14 (9): 20180458. doi:10.1098/rsbl.2018.0458. PMC 6170748. PMID30258031.
^Rose, K.D.; Deleon, V.B.; Mmissian, P.; Rana, R.S.; Sahni, A.; Singh, L.; Smith, T. (2007). "Early Eocene lagomorph (Mammalia) from western India and the early diversification of Lagomorpha". Proceedings of the Royal Society B. 275: R1. doi:10.1098/rspb.2007.1661.
^Marivaux, Laurent; Essid, El Mabrouk; Marzougui, Wissem; Ammar, Hayet Khayati; Adnet, Sylvain; Marandat, Bernard; Merzeraud, Gilles; Tabuce, Rodolphe; Vianey-Liaud, Monique (2014). "A new and primitive species of Protophiomys (Rodentia, Hystricognathi) from the late middle Eocene of Djebel el Kébar, Central Tunisia". Palaeovertebrata. 38 (1): 1–17.
^Poux, C.; Madsen, O.; Marquard, E.; Vieites, D. R.; de Jong, W. W.; Vences, M. (2005). "Asynchronous colonization of Madagascar by the four endemic clades of primates, tenrecs, carnivores, and rodents as inferred from nuclear genes". Systematic Biology. 54 (5): 719–730. doi:10.1080/10635150500234534. PMID16243759.
^Chimento, Nicolás R.; Agnolin, Federico L.; Novas, Fernando E. (2015). "The bizarre 'metatherians' Groeberia and Patagonia, late surviving members of gondwanatherian mammals". Historical Biology: An International Journal of Paleobiology. 27 (5): 603–623. doi:10.1080/08912963.2014.903945.
^Goin, F.J., Abello M.A. & Chornogubsky L. 2010. Middle Tertiary marsupials from Central Patagonia (Early Oligocene of Gran Barranca): Understanding South America's Grande Coupure. En: Madden R.H., Carlini A.A., Vucetich M.G. & Kay R.F. (Eds.), The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia. Cambridge University Press.
^Gurovich, Y.; Beck, R. (2009). "The phylogenetic affinities of the enigmatic mammalian clade Gondwanatheria". Journal of Mammalian Evolution. 16 (1): 25–49. doi:10.1007/s10914-008-9097-3.
^Krause, David W.; Hoffmann, Simone; Werning, Sarah (2017). "First postcranial remains of Multituberculata (Allotheria, Mammalia) from Gondwana". Cretaceous Research. 80: 91–100. doi:10.1016/j.cretres.2017.08.009.
^Rich, T. H.; Vickers-Rich, P.; Flannery, T. F.; Kear, B. P.; Cantrill, D. J.; Komarower, P.; Kool, L.; Pickering, D.; Rusler, P.; Morton, S.; van Klaveren, N.; Fitzgerald, E. M. G. (2009). "An Australian multituberculate and its palaeobiogeographic implications". Acta Palaeontologica Polonica. 54 (1): 1–6. CiteSeerX10.1.1.527.9540. doi:10.4202/app.2009.0101.
Agustí, Jordi; Antón, Mauricio (2002). Mammoths, Sabertooths, and Hominids: 65 Millions Years of Mammalian Evolution in Europe. New York: Columbia University Press. ISBN 0-231-11640-3.
This page is based on a Wikipedia article written by authors
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.