Ignacius

Last updated

Ignacius
Temporal range: Mid Paleocene-Late Eocene (Torrejonian-Chadronian)
~61.7–33.9  Ma
Ignacius NT.jpg
Restoration of Ignacius graybullianus
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Plesiadapiformes
Family:† Paromomyidae
Tribe:† Phenacolemurini
Genus:† Ignacius
Matthew and Granger, 1921 [1] [2]
Type species
†Ignacius frugivorus
Matthew and Granger, 1921
Species
  • †I. clarkforkensisBloch et al. 2007
  • †I. dawsonaeMiller et al. 2023
  • †I. fremontensisGazin 1971
  • †I. glenbowensisScott et al. 2023
  • †I. graybullianusBown and Rose 1976
  • †I. mckennaiMiller et al. 2023

Ignacius is a genus of extinct mammal from the early Cenozoic era. This genus is present in the fossil record from around 62-33 Ma (late Torrejonian-Chadronian North American Land Mammals Ages). [3] [4] The earliest known specimens of Ignacius come from the Torrejonian of the Fort Union Formation, Wyoming [5] and the most recent known specimens from Ellesmere Island in northern Canada. [1] Ignacius is one of ten genera within the family Paromomyidae, the longest living family of any plesiadapiforms, persisting for around 30 Ma during the Paleocene and Eocene epochs. [6] The analyses of postcranial fossils by paleontologists suggest that members of the family Paromomyidae, including the genus Ignacius, most likely possessed adaptations for arboreality. [7]

Contents

Taxonomy

As of 2022, there were four valid species within the genus Ignacius: I. frugivorus, [8] I. fremontensis, [5] I. clarkforkensis, [7] and I. graybullianus. [3] There are also two described species of Ignacius from the Arctic of Canada. [1] The type species for the genus Ignacius is I. frugivorus and was found at the Mason Pocket locality in Colorado. [8] The holotype specimen (AMNH 17368), published in 1921 by Matthew and Granger, consists of an upper jaw with the canine, fourth premolar, first molar, and second molar. [8]

The genus Ignacius is situated within the family Paromomyidae and the order Plesiadapiformes. The relationship between plesiadapiforms and the modern group Euarchonta (Dermoptera, Scandentia, and Primates) is still under debate by paleontologists with some suggesting a closer relationship with primates, [7] [9] and others suggesting a closer relationship with dermopterans. [10] [11]

The genus Ignacius was found to be synonymous with the closely related genus, Phenacolemur, by G.G. Simpson in 1935 [12] but revived by Bown and Rose in 1976. [3]

Description

Ignacius, along with the other plesiadapiforms, possess large, procumbent lower incisors convergent with those found in rodents, however, unlike rodents, the incisors of plesiadapiforms were not continuously growing. [3] Most species of Ignacius have a 1.0.1.3 lower dental formula although some specimens retain a small P3. [3] Compared with other paromomyids, Ignacius has small P4s in relation to M1s with relatively low crowned upper and lower molars. [3] The lower molars have reduced cusps, forming an almost continuous crest along the talonid basin. [9] The jaw of Ignacius is deep in comparison to tooth crown height, a feature distinct to this genus. Upper molars possess strong crests in a distinct ‘v’ shape between the paracone and metacone. [3]

Species

Ignacius frugivorus was the first species of Ignacius to be described, in 1921. [8] Ignacius frugivorus and I. fremontensis are the oldest species of Ignacius, both found in the Shotgun Local fauna of the Fort Union formation, Wyoming. [5] Until 2023, [1] the youngest known specimen of Ignacius was found in the Chadron formation of North Dakota and was represented by a single P4 (2). There is not enough material to identify this specimen to the species level. [4] Ignacius frugivorus and I. fremontensis are distinguishable from one another based primarily on the size of lower fourth premolars. [5] Ignacius fremontensis displays a significantly smaller P4 in relation to M1 when compared to I. frugivorus. [5] Ignacius clarkforkensis differs from other species in the retention of a single rooted P2 (5). Ignacius graybullianus has more quadrangular upper molars whereas the other three species are more triangular. [3] Strong v-shaped postparacone/prematacone cristae are present in I. graybullianus. [3] These cristae are less obliquely oriented in the other three taxa. [7] Ignacius mckennai and Ignacius dawsonae are the largest known species in the genus, living much further north and much later than the other known species, being found in Early Eocene deposits from Ellesmere Island. [1]

Paleoenvironment and geographic range

Ignacius occupied a broad geographic range during the early Cenozoic era in North America, ranging from Texas, [6] [13] to the Canadian Arctic. [6] [14] During the early Cenozoic, North America experienced multiple climatic changes with the warmest mean annual temperatures (around 16oC, 60oF) occurring during the Paleocene-Eocene Thermal Maximum (PETM) at around 55 Ma. [15] During the Eocene Climatic Optimum (c. 53 Ma) there was a correlated diversification of flora creating a complex, warm-temperate to subtropical habitat over much of interior North America. [16] The environment of Arctic Canada would have represented a temperate environment with winter temperatures rarely dropping below freezing. [14] The late Cretaceous and early Tertiary saw a diversification of angiosperms providing the opportunity for arboreal mammals to utilize the fruit, seed, exudate, and flower resources of these plants. [7] The environment of interior North America, extending into the Canadian Arctic, would have provided habitable ecosystems for these arboreal mammals to thrive and diversify. [7] [14] [16]

Functional morphology

Analysis of postcranial fossils of Ignacius suggest they were specialized for vertical climbing and clinging on tree trunks as well as for more agile arboreality than seen in other plesiadapiforms. [7] [17] Some researchers have also hypothesized based on analysis of hand bone morphology, that they possessed gliding adaptations like those of modern-day flying lemurs (Order Dermoptera). [10] Further anatomical analysis of cranial synapomorphies, also suggest a close relationship between dermopterans and plesiadapiforms. [11]

Evidence for vertical climbing can be seen in the morphology of the humerus, femur, and tarsal bones which are consistent with increased flexibility of the shoulder, elbow, hip, knee, and ankle joints. [7] [17] These features also suggest powerful flexion of the digits for grasping large tree trunks as well as small diameter support branches. [7] [17] The features listed above are seen in many plesiadapiforms, but some anatomical features set paromomyids apart in being more adept for arboreal living. Flexible lumbar vertebrae as well as increased surface area on the innominate and femur for the origin and insertion of gluteal muscles, suggest paromomyids were capable of powerful bounding across tree branches. [7] [17]

The large, procumbent incisors and reduced shearing crests of Paromomyids, especially Ignacius and Phenacolemur, suggest a diet specialized for feeding on exudates, comparable to the adaptions seen in extant callitrichine primates and Petaurus, a marsupial sugar-glider. [6] [7] [10] [18]

Related Research Articles

<span class="mw-page-title-main">Colugo</span> Family of mammals

Colugos are arboreal gliding mammals that are native to Southeast Asia. Their closest evolutionary relatives are primates. There are just two living species of colugos: the Sunda flying lemur and the Philippine flying lemur. These two species make up the entire family Cynocephalidae and order Dermoptera.

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

Purgatorius is a genus of seven extinct eutherian species typically believed to be the earliest example of a primate or a proto-primate, a primatomorph precursor to the Plesiadapiformes, dating to as old as 66 million years ago. The first remains were reported in 1965, from what is now eastern Montana's Tullock Formation, specifically at Purgatory Hill in deposits believed to be about 63 million years old, and at Harbicht Hill in the lower Paleocene section of the Hell Creek Formation. Both locations are in McCone County, Montana.

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

Plesiadapis is one of the oldest known primate-like mammal genera which existed about 58–55 million years ago in North America and Europe. Plesiadapis means "near-Adapis", which is a reference to the adapiform primate of the Eocene period, Adapis. Plesiadapis tricuspidens, the type specimen, is named after the three cusps present on its upper incisors.

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

Plesiadapiformes is an extinct basal Pan-Primates group, as sister to the rest of the pan-primates. The pan-primates together with the Dermoptera form the Primatomorpha. Purgatorius may not be a primate as an extinct sister to the rest of the Dermoptera or a separate, more basal stem pan-primate branch. Even with Purgatorius removed, the crown primates may even have emerged in this group.

<span class="mw-page-title-main">Plesiadapidae</span> Family of mammals

Plesiadapidae is a family of plesiadapiform mammals related to primates known from the Paleocene and Eocene of North America, Europe, and Asia. Plesiadapids were abundant in the late Paleocene, and their fossils are often used to establish the ages of fossil faunas.

<span class="mw-page-title-main">Anaptomorphinae</span> Extinct subfamily of primates

Anaptomorphinae is a pre-historic group of primates known from Eocene fossils in North America and Europe and later periods of Paleocene Asia, and are a sub-family of omomyids. The anaptomorphines is a paraphyletic group consisting of the two tribes Trogolemurini and Anaptomorphini. Anaptomorphine radiation in Wyoming, one of the most detailed records of changes within populations and between species in the fossil record, has provided remarkable evidence of transitional fossils.

The Willwood Formation is a sedimentary sequence deposited during the late Paleocene to early Eocene, or Clarkforkian, Wasatchian and Bridgerian in the NALMA classification.

The Margaret Formation is a geologic formation of the Eureka Sound Group in the Sverdrup Basin in Northwest Territories and Nunavut, Canada. The unit belonging to the Eureka Sound Group which crops out at Ellesmere Island preserves fossils dating back to the Early Eocene period, or Wasatchian in the NALMA classification.

The Lignites de Soissonais is a geologic formation in the Var, Marne departments of France. It preserves fossils dating back to the Ypresian stage of the Eocene period.

Acidomomys is a plesiadapiform mammal of the family Paromomyidae, a precursor to the primates or very closely related to them.

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

Paromomyidae is a family of mammals that may include the earliest primates, or taxa closely related to them.

Micromomyidae (Micromomids) is a family of extinct plesiadapiform mammals that include some of the earliest known primates. The family includes five genera that lived from the Paleocene epoch into the early Eocene epoch.

Chiromyoides is a small plesiadapid primatomorph that is known for its unusually robust upper and lower incisors, deep dentary, and comparatively small cheek teeth. Species of Chiromyoides are known from the middle Tiffanian through late Clarkforkian North American Land Mammal Ages (NALMA) of western North America, and from late Paleocene deposits in the Paris Basin, France.

<i>Peradectes</i>

Peradectes is an extinct genus of small metatherian mammals known from the latest Cretaceous to Eocene of North and South America and Europe. The first discovered fossil of P. elegans, was one of 15 Peradectes specimens described in 1921 from the Mason pocket fossil beds in Colorado. The monophyly of the genus has been questioned.

Azygonyx was a small tillodont mammal, likely the size of a cat to raccoon, that lived in North America during the Paleocene and Eocene in the early part of the Cenozoic Era. The only fossils that have been recovered are from the Willwood and Fort Union Formations in the Bighorn Basin of Wyoming, United States, and date to the Clarkforkian to Wasatchian, about 56 to 50 million years ago. Fifty-six collections that have been recovered thus far include the remains of Azygonyx. Azygonyx survived the Paleocene Eocene Thermal Maximum along with other mammals like Phenacodus and Ectocion, both of which were ground-dwelling mammals. Azygonyx probably was a generalist terrestrial mammal that may have roamed around the ground, but was also capable of climbing trees.

Apatemys is a member of the family Apatemyidae, an extinct group of small and insectivorous placental mammals that lived in the Paleogene of North America, India, and Europe. While the number of genera and species is less agreed upon, it has been determined that two apatemyid genera, Apatemys and Sinclairella, existed sequentially during the Eocene in North America. The genus Apatemys, living as far back as 50.3 million years ago (mya), existed through part of the Wasatchian and persisted through the Duchesnean, and Sinclairella followed, existing from the Duchesnean through the Arikareean. Examinations of specimens belonging to the genus Apatemys suggest adaptations characteristic of arboreal mammals.

Carpodaptes was a genus that encompassed small, insectivorous animals that roamed the Earth during the Late Paleocene. Specifically, Carpodaptes can be found between the Tiffanian and Clarkforkian periods of North America. Although little evidence, this genus may have made it through to the early Eocene. They are known primarily from collections of jaw and teeth fragments in North America, mainly in southwestern Canada and northwestern America. Carpodaptes are estimated to have weighed approximately 53-96 grams which made them a little bigger than a mouse. However small, Carpodaptes was a placental mammal within the order Plesiadapiformes that appeared to have a high fiber diet. This insect-eating mammal may have been one of the first to evolve fingernails in place of claws. This may have helped them pick insects, nuts, and seeds more easily off the ground than with paws or claws. Carpodaptes was thought to only exist in North America but recent discoveries of dentition fragments have been found in China.

Navajovius is an extinct genus of plesiadapiforms that lived during the Paleocene epoch. Plesiadapiforms were small, arboreal mammals that are theorized to be either closely related to primates or dermopterans. Navajovius has only been documented from localities within North America. This genus was officially named in 1921 by Walter Granger and William Matthew and the type specimen is housed at the American Museum of Natural History.

Saxonella is a genus of extinct primate from the Paleocene Epoch, 66-56 Ma. The genus is present in the fossil record from around ~62-57 Ma. Saxonella has been found in fissure fillings in Walbeck, Germany as well as in the Paskapoo Formation in Alberta, Canada. Saxonella is one of five families within the superfamily Plesiadapoidae, which appears in the fossil record from the mid Paleocene to the early Eocene. Analyses of molars by paleontologists suggest that Saxonella most likely had a folivorous diet.

Torrejonia is a genus of extinct plesiadapiform that belongs to the family Palaechthonidae. There are currently two species known, T. wilsoni and T. sirokyi. This genus is present in the fossil record from around 62-58 Ma. Species belonging to this genus are suggested to be plesiadapiforms based on adaptations observed in the skeletal morphology consistent with arboreal locomotor behavior. Following the mass extinction event at the Cretaceous–Paleogene boundary (K-Pg), a large diversity of plesiadapiform families were documented beginning at the Torrejonian NALMA. Research has shown that T. wilsoni is one of the largest palaechthonids and is reconstructed as being more frugivorous than other palaechthonids.

References

  1. 1 2 3 4 5 Miller, K.; Tietjen, K.; Beard, K.C. (January 2023). "Basal Primatomorpha colonized Ellesmere Island (Arctic Canada) during the hyperthermal conditions of the early Eocene climatic optimum". PLOS ONE. 18 (1): e0280114. doi: 10.1371/journal.pone.0280114 . PMC   9876366 . PMID   36696373.
  2. ↑ Matthew, W.D.; Granger, W. (September 1921). "New genera of Paleocene mammals" (PDF). American Museum Novitates (13): 1–7.
  3. 1 2 3 4 5 6 7 8 9 Bown, T. M., & Rose, K. D. (1976). New early Tertiary primates and a reappraisal of some Plesiadapiformes. Folia Primatologica, 26, 109– 138.
  4. 1 2 Kihm, A. J., & Tornow, M. A. (2014). First occurrence of plesiadapiform primates from the Chadronian (latest Eocene). Paludicola, 9, 176– 182.
  5. 1 2 3 4 5 Gazin, C. L. "Paleocene primates from the Shotgun Member of the Fort Union Formation in the Wind River Basin, Wyoming." Proceedings of the Biological Society of Washington 84, no. 3 (1971): 13-38.
  6. 1 2 3 4 Silcox, Mary T., Jonathan I. Bloch, Doug M. Boyer, Stephen GB Chester, and Sergi López‐Torres. "The evolutionary radiation of plesiadapiforms." Evolutionary Anthropology: Issues, News, and Reviews 26, no. 2 (2017): 74-94.
  7. 1 2 3 4 5 6 7 8 9 10 11 Bloch, J. I., Silcox, M. T., Boyer, D. M., & Sargis, E.J. (2007). New Paleocene skeletons and the relationship of “plesiadapiforms” to crownclade primates. Proceedings of the National Academy of Sciences, USA, 104, 1159–1164.
  8. 1 2 3 4 Matthew, William Diller, and Walter Granger. New genera of Paleocene mammals. By order of the Trustees of The American Museum of Natural History, 1921.
  9. 1 2 Silcox, M. T. (2008). The biogeographic origins of Primates and Euprimates: east, west, north, or south of Eden? In M. J. Dagosto, & E. J. Sargis (Eds.), Mammalian Evolutionary Morphology: A Tribute to Frederick S. Szalay (pp. 199–231). New York, NY: Springer-Verlag.
  10. 1 2 3 Beard, K. C. (1990). Gliding behavior and palaecology of the alleged primate family Paromomyidae (Mammalia, Dermoptera). Nature, 345, 340–341.
  11. 1 2 Kay, R. F., Thorington, R. W. Jr, Houde, P. (1990). Eocene plesiadapiform shows affinities with flying lemurs not primates. Nature, 345, 342– 344.
  12. ↑ Simpson, George Gaylord. "The Tiffany fauna, Upper Paleocene. 3, Primates, Carnivora, Condylarthra, and Amblypoda. American Museum novitates; no. 817." (1935).
  13. ↑ Schiebout, Judith Ann. Vertebrate paleontology and paleoecology of Paleocene Black Peaks Formation, Big Bend National Park, Texas. Texas Memorial Museum, The University of Texas at Austin, 1974.
  14. 1 2 3 Eberle, J. J., & Greenwood, D. R. (2012). Life at the top of the greenhouse Eocene world – A review of the Eocene flora and vertebrate fauna from Canada’s High Arctic. Geological Society of America Bulletin, 124,3.
  15. ↑ Wing, Scott L., Thomas M. Bown, and John D. Obradovich. "Early Eocene biotic and climatic change in interior western North America." Geology 19, no. 12 (1991): 1189-1192.
  16. 1 2 Woodburne, Michael O., Gregg F. Gunnell, and Richard K. Stucky. "Climate directly influences Eocene mammal faunal dynamics in North America." Proceedings of the National Academy of Sciences 106, no. 32 (2009): 13399-13403.
  17. 1 2 3 4 Bloch, J. I., & Boyer, D. M. (2007). New skeletons of Paleocene-Eocene Plesiadapiformes: a diversity of arboreal positional behaviors in early primates. In M. J. Ravosa, & M. Dagosto (Eds.), Primate Origins: Adaptations and Evolution (pp. 535–581). New York, NY: Springer.
  18. ↑ Kay, Richard F., and Matt Cartmill. "Cranial morphology and adaptations of Palaechthon nacimienti and other Paromomyidae (Plesiadapoidea,? Primates), with a description of a new genus and species." Journal of Human Evolution 6, no. 1 (1977): 19-53.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.