Volaticotherini

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Volaticotherini
Temporal range: Toarcian–Berriasian
Volaticotherium-Paleozoological Museum of China (cropped).jpg
Holotype of Volaticotherium
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Clade:† Eutriconodonta
Clade:† Volaticotherini
Meng et al., 2006
Type species
† Volaticotherium antiquum
Meng et al., 2006
Genera

Volaticotherini is a clade of eutriconodont mammals from the Mesozoic. In addition to the type genus Volaticotherium , it includes the genera Argentoconodon , Ichthyoconodon , and potentially Triconolestes .

Contents

Since most remains are primarily teeth, they are foremostly diagnosticated by their highly distinctive molars. However, the remains of one species, Volaticotherium antiquum , show that at least some members of this clade were capable of gliding. [1] and Argentoconodon shares similar post-cranial features that also indicate aerial locomotion. As such, this clade contains some of the oldest known aerial mammals, alongside the various gliding haramiyidans.

Definition

Volaticotherini is phylogenetically defined as the clade derived from the most recent common ancestor of Argentoconodon, Ichthyoconodon, and Volaticotherium. [2]

History

Ichthyoconodon was the first described member of this group, back in 1995, previously usually ranked among eutriconodonts, albeit tentatively due to its atypical teeth. Volaticotherium , described in 2006, provided a fairly complete skeleton and led to the erection of a distinct family, Volaticotheridae, and order, Volaticotheria, to house the genus, and allowed Ichthyoconodon to be recognized as a potential relative. [1] Volaticotheria was considered the sister taxon of a clade comprising eutriconodonts, multituberculates, and trechnotheres. However, not long after, an eutriconodont identity was suspected, and Volaticotheria has since fallen into disuse. [3]

Subsequent analyses have consistently recovered Argentoconodon as the sister taxon of Volaticotherium, with Ichthyoconodon as the sister taxon of that clade and thus the basalmost volaticotherin. [2] [4] The North American genus Jugulator may be the sister taxon of Volaticotherini. These were moved to the eutriconodont family Triconodontidae, as part of the alticonodontine assemblage, and the clade was renamed Volaticotherini accordingly. [2] However, other sources consider the clade to be a separate family from Triconodontidae, as Volaticotheridae. [5] This may be supported by other, more recent analyses, which find the clade to be more basally placed within Eutriconodonta. [4]

Characteristics

Since most volaticotherian remains are based on teeth, the diagnostic characteristic of the group is its molar morphology. Though classified as "triconodont" in shape, volaticotherian molars are highly atypical, possessing high, curved, backwards facing cusps aligned anteroposteriorly, lacking a cingulum. [1] [2] Canines and incisors tend to be fairly large.

In the two forms that do possess postcranial remains, Argentoconodon and Volaticotherium , we see a highly specialised femur, lacking a femoral neck. [2]

Volaticotherium is rather well preserved, bearing a mostly complete skeleton and soft-tissue impressions such as hair and patagia.

Aerial locomotion

One genus of volaticotherin, Volaticotherium, has clear evidence of being capable of gliding. It was the first gliding Mesozoic mammal discovered and lived at least 70 million years before the appearance of the first flying and gliding therians. [1] It preserved a large, fur-covered patagium, extending not only between the limbs and tail, but also to the digits, "sandwiching" them. The limbs were proportionally longer than those of other Mesozoic mammals, fitting the standards in flying and gliding mammals, and the femur is uniquely specialised, allowing the leg to be extended laterally and remain steady during gliding. The tail is dorsoventrally flattened, and supports evidence of uropatagia in at least the proximal vertebrae. [1] Argentoconodon shares similar femur characteristics, suggesting that it too may have been capable of gliding. [2]

Distribution

Volaticotherini was a relatively widespread and long-lived clade, with occurrences known from the Toarcian of South America, Oxfordian of China, and Berriasian of Morocco. The presence of volaticotherins in Gondwana is unusual, as they are among the few known Gondwanan triconodonts (and, if aligned with triconodontids, the only representatives of the group in Gondwanna), with Argentoconodon occurring as far back as the Early Jurassic in otherwise australosphenidan dominated faunas. [2] [6]

Diet

Though highly unusual and possibly indicating atypical occlusion patterns, [1] [2] volaticotherian molars are thought to have had a shearing motion as in other eutriconodonts. [7] [6] Combined with long canines, this seems to indicate that, like their relatives, they were probably carnivorous. Ichthyoconodon was fairly large by Mesozoic mammal standards, and were probably capable of tackling vertebrate prey. [7] In a study about Mesozoic mammal diets Argentoconodon ranks among carnivorous species, while Volaticotherium ranks among insectivorous taxa. [8] This same result is provided almost identically in a posterior study, albeit with Volaticotherium closer to the carnivore space. [9]

It has been noted that most gliding mammals are predominantly herbivorous, [10] [11] which would make volaticothere carnivory truly exceptional. In particular, Volaticotherium itself has been compared to insectivore bats. [1]

Paleoecology

Volaticotherins, as is typical for gliding animals, were adapted for an arboreal lifestyle. [1] One volaticotherin, Ichthyoconodon, was recovered from marine facies and consequently initially interpreted as an aquatic animal. [12] However, many terrestrial mammals are preserved in aquatic environments, so it is unclear how strong this evidence is regarding its life habits, [7] though its teeth appear to not have undergone long aquatic transportation. [12]

Related Research Articles

<i>Akidolestes</i> Extinct genus of mammals

Akidolestes is an extinct genus of mammals of the family Spalacotheriidae, a group of mammals related to therians.

<span class="mw-page-title-main">Docodonta</span> Extinct order of mammaliaforms

Docodonta is an order of extinct Mesozoic mammaliaforms. They were among the most common mammaliaforms of their time, persisting from the Middle Jurassic to the Early Cretaceous across the continent of Laurasia. They are distinguished from other early mammaliaforms by their relatively complex molar teeth. Docodont teeth have been described as "pseudotribosphenic": a cusp on the inner half of the upper molar grinds into a basin on the front half of the lower molar, like a mortar-and-pestle. This is a case of convergent evolution with the tribosphenic teeth of therian mammals. There is much uncertainty for how docodont teeth developed from their simpler ancestors. Their closest relatives may have been certain Triassic "symmetrodonts", namely Woutersia, Delsatia, and Tikitherium.

<span class="mw-page-title-main">Australosphenida</span> Subclass of mammals

The Australosphenida are a clade of mammals, containing mammals with tribosphenic molars, known from the Jurassic to Mid-Cretaceous of Gondwana. Although they have often been suggested to have acquired tribosphenic molars independently from those of Tribosphenida, this has been disputed. Fossils of australosphenidans have been found from the Jurassic of Madagascar and Argentina, and Cretaceous of Australia and Argentina. Monotremes have also been considered a part of this group in many studies, but this is also disputed.

<i>Volaticotherium</i> Extinct family of mammals

Volaticotherium antiquum is an extinct, gliding, insectivorous mammal that lived in Asia during the Jurassic period, around 164 mya. It is the only member of the genus Volaticotherium.

<span class="mw-page-title-main">Eutriconodonta</span> Extinct order of mammals

Eutriconodonta is an order of early mammals. Eutriconodonts existed in Asia, Africa, Europe, North and South America during the Jurassic and the Cretaceous periods. The order was named by Kermack et al. in 1973 as a replacement name for the paraphyletic Triconodonta.

<span class="mw-page-title-main">Jeholodentidae</span> Extinct family of mammals

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Shuotherium is a fossil mammaliaform known from Middle-Late Jurassic of the Forest Marble Formation of England, and the Shaximiao Formation of Sichuan, China.

<i>Kuehneotherium</i> Extinct genus of mammaliaforms

Kuehneotherium is an early mammaliaform genus, previously considered a holothere, that lived during the Late Triassic-Early Jurassic Epochs and is characterized by reversed-triangle pattern of molar cusps. Although many fossils have been found, the fossils are limited to teeth, dental fragments, and mandible fragments. The genus includes Kuehneotherium praecursoris and all related species. It was first named and described by Doris M. Kermack, K. A. Kermack, and Frances Mussett in November 1967. The family Kuehneotheriidae and the genus Kuehneotherium were created to house the single species Kuehneotherium praecursoris. Modeling based upon a comparison of the Kuehneotherium jaw with other mammaliaforms indicates it was about the size of a modern-day shrew between 4 and 5.5 g at adulthood.

Triconolestes is an extinct genus of Late Jurassic eutriconodont mammal from the Morrison Formation, present in stratigraphic zones 4. Known from only a single molar, it is a small mammal typically considered an amphilestid. However, it has also been compared to Argentoconodon, which has been considered a volaticothere related to gliding mammals such as Volaticotherium and Ichthyoconodon.

<span class="mw-page-title-main">Triconodontidae</span> Extinct family of mammals

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<span class="mw-page-title-main">Gobiconodontidae</span> Extinct family of mammals

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<span class="mw-page-title-main">Euharamiyida</span> Extinct clade of mammaliaforms

Euharamiyida also known as Eleutherodontida, is clade of early mammals or mammal-like cynodonts from the Middle Jurassic to Early Cretaceous of Eurasia and possibly North America. The group is sometimes considered a sister group to Multituberculata, or part of an earlier divergence within the synapsid line. It is disputed whether or not they are related to the Haramiyids from the Late Triassic, such as Haramiyavia. The morphology of their teeth indicates that they were herbivorous or omnivorous. Some members of the group are known to be arboreal, including gliding forms similar to modern flying squirrels or colugos.

Argentoconodon is an extinct genus of theriimorph mammal from the Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Patagonia. When originally described, it was known only from a single molariform tooth, which possessed a combination of primitive and derived features. The tooth is currently held in the Museo Paleontológico Egidio Feruglio, where it was given the specimen number MPEF-PV 1877. New material described in 2011 show that Argentoconodon was similar to Ichthyoconodon, Jugulator and Volaticotherium within the family Triconodontidae, and possibly also Triconolestes.

<i>Ichthyoconodon</i> Extinct family of mammals

Ichthyoconodon is an extinct genus of eutriconodont mammal from the Lower Cretaceous of Morocco. It is notable for having been found in a unique marine location, and the shape of its teeth suggests an unusual, potentially fish-eating ecological niche. Analysis suggests it is part of a group of gliding mammals that includes Volaticotherium.

Jugulator is an extinct genus of mammals from the Cretaceous of North America. It contains one species, Jugulator amplissimus. A eutriconodont, it is known from the Cedar Mountain Formation, and is both a large sized and possibly ecologically specialised taxon, showcasing the diversity of mammals in the Mesozoic.

<i>Dyskritodon</i> Extinct family of mammals

Dyskritodon is a genus of extinct mammal from the Early Cretaceous of Morocco, and possibly the Early Jurassic of India. Of uncertain affinities, it is tentatively described as a eutriconodont.

Astroconodon is an extinct genus of mammal from the Cretaceous of North America. Part of Eutriconodonta, it was a small sized predator, either a terrestrial insectivore and carnivore, or a semi-aquatic piscivore.

<i>Triconodon</i> Extinct family of mammals

Triconodon is a genus of extinct mammal from the Early Cretaceous of England and France with two known species: T. mordax and T. averianovi. First described in 1859 by Richard Owen, it is the type genus for the order Triconodonta, a group of mammals characterised by their three-cusped (triconodont) molar teeth. Since then, this "simplistic" type of dentition has been understood to be either ancestral for mammals or else to have evolved multiple times, rendering "triconodonts" a paraphyletic or polyphyletic assemblage respectively, but several lineages of "triconodont" mammals do form a natural, monophyletic group, known as Eutriconodonta, of which Triconodon is indeed part of.

Alticonodon is a genus of extinct mammal from the Late Cretaceous of North America. It is the geologically youngest known eutriconodont, and is a fairly more specialised animal than earlier representatives of this clade.

Vilevolodon is an extinct, monotypic genus of volant, arboreal euharamiyids from the Oxfordian age of the Late Jurassic of China. The type species is Vilevolodon diplomylos. The genus name Vilevolodon references its gliding capabilities, Vilevol, while don is a common suffix for mammalian taxon titles. The species name diplomylos refers to the dual mortar-and-pestle occlusion of upper and lower molars observed in the holotype; diplo, mylos.

References

  1. 1 2 3 4 5 6 7 8 Meng, J.; Hu, Y.; Wang, Y.; Wang, X.; Li, C. (2006). "A Mesozoic gliding mammal from northeastern China" (PDF). Nature. 444 (7121): 889–893. Bibcode:2006Natur.444..889M. doi:10.1038/nature05234. PMID   17167478. S2CID   28414039.
  2. 1 2 3 4 5 6 7 8 Gaetano, Leandro C.; Rougier, Guillermo W. (2011). "New materials of Argentoconodon fariasorum (Mammaliaformes, Triconodontidae) from the Jurassic of Argentina and its bearing on triconodont phylogeny". Journal of Vertebrate Paleontology. 31 (4): 829–843. Bibcode:2011JVPal..31..829G. doi:10.1080/02724634.2011.589877. hdl: 11336/68497 . S2CID   85069761.
  3. ↑ Luo, Zhe-Xi (2007). "Transformation and diversification in early mammal evolution". Nature. 450 (7172): 1011–1019. Bibcode:2007Natur.450.1011L. doi:10.1038/nature06277. PMID   18075580. S2CID   4317817.
  4. 1 2 Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D. (2015). "A Cretaceous eutriconodont and integument evolution in early mammals". Nature. 526 (7573): 380–384. Bibcode:2015Natur.526..380M. doi:10.1038/nature14905. PMID   26469049. S2CID   205245235.
  5. ↑ Averianov, A. O.; Lopatin, A. V. (2011). "Phylogeny of triconodonts and symmetrodonts and the origin of extant mammals". Doklady Biological Sciences. 436: 32–35. doi:10.1134/S0012496611010042. PMID   21374009. S2CID   10324906.
  6. 1 2 Butler, Percy M.; Sigogneau-Russell, Denise (2016). "Diversity of triconodonts in the Middle Jurassic of Great Britain". Palaeontologia Polonica. 67: 35–65. doi:10.4202/pp.2016.67_035 (inactive 31 January 2024).{{cite journal}}: CS1 maint: DOI inactive as of January 2024 (link)
  7. 1 2 3 Kielan-Jaworowska, Zofia; Cifelli,, Richard L.; Luo, Zhe-Xi (2004). "Chapter 7: Eutriconodontans". Mammals from the Age of Dinosaurs: Origins, Evolution, and Structure. New York: Columbia University Press. pp. 216–248. ISBN   0-231-11918-6.
  8. ↑ Grossnickle, D. M.; Polly, P. D. (2013). "Mammal disparity decreases during the Cretaceous angiosperm radiation". Proceedings of the Royal Society B: Biological Sciences. 280 (1771): 20132110. doi: 10.1098/rspb.2013.2110 . PMC   3790494 . PMID   24089340.
  9. ↑ Morales-García, N. M.; Gill, P. G.; Janis, C. M.; Rayfield, E. J. (2021). "Jaw shape and mechanical advantage are indicative of diet in Mesozoic mammals". Communications Biology. 4 (1): 242. doi:10.1038/s42003-021-01757-3. PMC   7902851 . PMID   33623117.
  10. ↑ Jackson, Stephen Matthew and Schouten, Peter. Gliding Mammals of the World, Csiro Publishing, 2012
  11. ↑ Luo, Zhe-Xi; Meng, Qing-Jin; Grossnickle, David M.; Di, Liu; Neander, April I.; Zhang, Yu-Guang; Ji, Qiang (2017). "New evidence for mammaliaform ear evolution and feeding adaptation in a Jurassic ecosystem". Nature. 548 (7667): 326–329. Bibcode:2017Natur.548..326L. doi:10.1038/nature23483. PMID   28792934. S2CID   4463476.
  12. 1 2 Sigogneau-Russell, Denise (1995). "Two possibly aquatic triconodont mammals from the Early Cretaceous of Morocco" (PDF). Acta Palaeontologica Polonica. 40 (2): 149–162.
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